https://wiki.freecad.org/api.php?action=feedcontributions&user=Jrheinlaender&feedformat=atomFreeCAD Documentation - User contributions [en]2024-03-29T05:31:28ZUser contributionsMediaWiki 1.40.1https://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=49254PartDesign Bearingholder Tutorial II2013-12-03T19:27:59Z<p>Jrheinlaender: corrected the branch</p>
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<div>{{VeryImportantMessage|'''This tutorial is for the development version of FreeCAD. Compile from here: http://sourceforge.net/p/free-cad/code/ci/jriegel/dev-assembly/~/tree/'''}}<br />
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[[Image:HolderTop2-19.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
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This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
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This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
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Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br />
You can find my version of the part created in this tutorial [[http://ubuntuone.com/39PTZ3Y3LUnmZzpZQPcJT4 here]]<br />
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== Design data ==<br />
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The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. The head of such a bolt will require at least 20mm diameter free space. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
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The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
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== Setting up the skeleton geometry ==<br />
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[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
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== The main body ==<br />
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[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
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You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
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[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
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[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
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[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
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[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
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[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
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== Adding the bodies for the bolts ==<br />
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[[Image:HolderTop2-13.jpg|The sketch for the body for the bolts|thumb|right|400px]]<br />
The bolts need two cylindrical bodies on both sides of the main Body. It is best to include the 2 degree draft angle in the sketch. I tried revolving a cylinder and later applying a draft, but weird things happened after mirroring it and I couldn't put fillets on it because the surface was warped somehow.<br />
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The sketch is dimensioned so that the rotation axis is 12mm distance to the outer diameter of the skeleton Body, 7mm for the radius of the hole plus 5mm for the wall thickness. For the sake of having a fully parametric part, it is a good idea to add a plane to the Skeleton about 25mm above the XY-plane to mark the top of the cylinders. Since this will be machined, the sketch is dimensioned 3mm above it.<br />
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[[Image:HolderTop2-14.jpg|The body for the bolts|thumb|right|400px]]<br />
Create a revolution from the sketch and apply a fillet of 4mm to the top. This means that after machining away 3mm, a slight radius will remain which helps to avoid a sharp edge where someone could cut their hand when tightening the bolt.<br />
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[[Image:HolderTop2-16.jpg|The main body with the two bodies for the bolts|thumb|right|400px]]<br />
Create a boolean feature to fuse the main Body and the bolt body. Then create a new body for the other side. Duplicate the sketch of the revolution, move it to this body and create the second body for the bolts (mirroring a Body is not supported yet so you need to redo most of it). Then fuse this second body into the main Body as well. Finally, apply a large fillet on the edge created by the boolean fuse operation. The largest I could get was 4mm.<br />
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== Hollowing out the main body ==<br />
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[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
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Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
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[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
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After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
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[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
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[[Image:HolderTop2-15.jpg|The completed raw part of the holder (without machining)|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". Put a 3mm fillet on the two edges resulting from the cut-out operation (again some edges remain that are "unfilletable"). The result should look like the picture on the right.<br />
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The raw part is now completed. This is what the holder will look like before machining. Note that since the mold will have a top and bottom half, the edge between these two cannot be filleted. Also, if you give away this model to a foundry make sure to point out that it has the dimensions after casting. The foundry will then have to apply a certain percentage of shrinkage to the model (making the digital model used to manufacture the mold larger so that when the metal cools down and shrinks after casting it will have the right size).<br />
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== Machining ==<br />
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[[Image:HolderTop2-17.jpg|Sketch to "drill" the hole for the bolts|thumb|right|400px]]<br />
To take away the material for machining the inside of the holder, very conveniently we can use the Skeleton Body itself. If you don't want that because then the skeleton gets hidden somewhere deep in the tree, you can also duplicate the sketch of the skeleton Revolution feature and re-create the revolution in another body. This is not completely parametric, though, because the duplicated sketch is independent of the original, so you will have to work on both if you change a dimension. Dependent duplicated features might be supported in the future sometime.<br />
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For the rest of the machining, create a new Body. The bottom of the holder will be machined by a Pad sketched on the XY-plane extending downwards. Next, sketch a revolution to make a hole for the bolts. You will need to sketch on the XZ-plane and revolve it so that you can choose the outer diameter of the skeleton Body as an external reference. The top part of the sketch will serve to machine a flat place for the head of the bolt. It is dimensioned to leave at least 5mm wall thickness in the holder. If this does not give enough space for the bolt head then you can move the datum plane upwards. Of course, you could put this logic into the Skeleton, which is left as an exercise to the reader!<br />
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[[Image:HolderTop2-18.jpg|The machining Body|thumb|right|400px]]<br />
You can mirror the revolution on the YZ-axis. The picture on the right shows the "machining" Body. Of course, most of the dimensions of the Pads and Revolutions are not important as long as there is plenty of overlap.<br />
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[[Image:HolderTop2-19.jpg|The finished Holder with machining|thumb|right|400px]]<br />
Finally, create a boolean operation to cut the machining Body out of the main Body. If you want a nice visual effect, you can colour the machined surfaces differently from the rest of the part. This is also a useful optical feedback showing you whether you forgot to machine somewhere.<br />
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{{languages | {{it|PartDesign_Bearingholder_Tutorial_II/it}} }}<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_I&diff=49253PartDesign Bearingholder Tutorial I2013-12-03T19:27:34Z<p>Jrheinlaender: corrected the branch</p>
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<div>{{VeryImportantMessage|'''This tutorial is for the development version of FreeCAD. Compile from here: http://sourceforge.net/p/free-cad/code/ci/jriegel/dev-assembly/~/tree/'''}}<br />
<br />
[[Image:HolderTop1-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the first part of the tutorial. It will use what might be called the 'single body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br />
You can find my version of the part created by this tutorial [[http://ubuntuone.com/5gok0J4dye3Fo4BKWMGWVa here]].<br />
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<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
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== Setting up the skeleton geometry ==<br />
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[[Image:HolderTop1-2.jpg|Bearing holder with the two most important skeleton planes|thumb|right|text-top|400px]]<br />
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The idea of skeleton geometry is to capture the basic design dimensions in a single datum feature (e.g. a plane or an axis). When the design dimension changes, all that needs to be done is to change the skeleton feature. If the model is well built, then all its feature will recompute to reflect the design change. This reduces the danger that in a complex model, where the basic design dimensions are used in multiple places, you forget to change it somewhere.<br />
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The alternative to skeleton geometry is to have a table of the basic design dimensions that assign a symbolic name to each dimension, and then use the symbolic name wherever the dimensions is required to build the model. FreeCAD does not allow this approach yet.<br />
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[[Image:HolderTop1-3.jpg|Base planes and all datum planes|thumb|right|text-top|400px]]<br />
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For the case of the bearing holder, the two most important design dimensions are the distance between the bolts (which limits the size of the bearing that can be used) and the height of the bolt heads. The dimensions chosen are<br />
* Distance between bolts: Radius of bearing (45) + wall thickness (5) plus radius of hole for bolt (7) = 57mm, so the vertical plane will be 57mm offset from the YZ-plane. To create this datum plane, select the YZ-plane and then choose to create a new datum plane. Enter the offset in the dialog that opens up<br />
* Height of bolt heads: This was chosen as an offset of 28mm from the XZ-plane<br />
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For convenience, two further datum planes can be created to reflect the amount of material that must be cut away from the sides of the bearing holder. They are offset +22 and -22 from the XY-plane.<br />
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It is advisable to give clear names to the skeleton geometry. Most of the time, you will want to turn off visibility for datum planes because they clutter up the screen, and if the planes have self-explanatory names you can just pick them by name instead of from the screen.<br />
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== The solid geometry ==<br />
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[[Image:HolderTop1-4.jpg|thumb|400px|right|text-top|Sketch of the first pad]]<br />
Now its time to start creating some real geometry. The sketch for the first pad is shown on the right. It is placed on the XY-plane. There are just three dimensions: The inner radius (22.5mm), the machining allowance (3mm) at the base as an offset to the XZ-plane and the distance from the datum plane representing the bolt axis (7mm). This means that if you later move the datum plane, the pad will automatically adjust its outer radius. Remember that before you can use the datum plane for dimensioning, you need to introduce it as external geometry to the sketcher.<br />
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You are probably wondering why there is a small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), just pad it symmetrically to the sketch plane with a length of 62mm: 34mm for the bearing, 2x 9mm for the sealing rings, 2x 5mm for the wall thickness.<br />
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[[Image:HolderTop1-5.jpg|thumb|400px|right|text-top|Sketch of the cut-away at the side of the pad]]<br />
Next we want to cut away some material where the sealing rings are, because their outer diameter is much less than the bearing's. The easiest way to create the sketches is to select the sketch of the pad and then choose "Duplicate selection" from the edit menu. You can then remap the sketch to the side of the pad, and modify it as shown in the picture.<br />
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The only two important dimensions in the sketch are 3mm of machining allowance at the bottom, and a inner diameter of 78mm: 68mm for the outer diameter of the sealing ring + 2x 5mm wall thickness. Since the sealing ring on the other side will only have a diameter of 55mm, the cut-out can be 65mm here.<br />
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After you have created the sketch, pocket it up to the datum plane marking the bearing side plus 5mm wall thickness. If you ever want to modify the holder to be able to hold wider bearings, all you have to do is to change the dimension of these datum planes, and the cut-out depth will follow along.<br />
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[[Image:HolderTop1-6.jpg|thumb|400px|right|text-top|Sketch of the cut-away inside the pad]]<br />
To reduce the amount of machining required, we also want to cut away some material inside the holder. Again, duplicating the sketch of the first pad is convenient. It doesn't even have to be remapped. Again, the only important dimensions are the machining allowance (3mm) and the outer diameters: 84mm for the place where the bearing will be (90mm - 2x machining allowance), 49mm for the smaller sealing ring (55mm - 2x 3mm) and 62mm for the larger sealing ring.<br />
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After creating the sketches, pocket them: Symetrically 28mm for the bearing cut-out (34mm - 2x machining allowance) and one-sided 23mm for the cut-outs for the sealing rings: 34mm / 2 for half the bearing width + 9mm for the sealing rings - 3mm machining allowance. <br />
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[[Image:HolderTop1-7.jpg|thumb|400px|right|text-top|Main geometry of the holder top]]<br />
Your part should now look like the picture on the right. Note how the different cut-aways combine to create an almost uniform wall thickness, which will make the casting easier and less liable to have pores.<br />
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[[Image:HolderTop1-8.jpg|thumb|400px|right|text-top|Sketch with draft where the bolts will be]]<br />
Now all that remains is to create some material for the bolts to go through. You might be tempted to sketch these as a circle and then pad them, but this will head you for trouble when you try to put the draft onto them later (I assume that is a weakness of OpenCascade). So to circumvent the problems, it is better to create a sketch with the draft angle included and then rotate it through 360 degrees.<br />
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Here again the skeleton planes come in useful. You will need the bolt axis plane and the bolt head plane as external geometry. Then, create a straight line for the rotation axis and make sure it is constrained to the bolt axis plane reference. Toggle it to be construction geometry. Then, sketch the rest of the contour. The important dimensions are the machining allowance at the top and bottom and the radius of 12mm: 7mm for the hole radius + 5mm wall thickness.<br />
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[[Image:HolderTop1-9.jpg|thumb|400px|right|text-top|Finished geometry of the holder top (without draft and fillets)]]<br />
Create a revolution feature from the sketch and then mirror it on the YZ-plane. This is all the solid geometry we need to model. The rest is draft and fillets.<br />
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== Applying draft to the side faces ==<br />
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[[Image:HolderTop1-10.jpg|thumb|400px|right|text-top|The neutral plane for creating drafts]]<br />
The next step is to apply drafts on all faces. Its important to consider the location of the neutral plane, that is, the plane which the face is "rotated" around. If we choose as neutral plane the bottom of the holder, then we will have a problem with the wall thickness in the top part of the holder. Therefore, we create a datum plane at an offset of 40mm from the XZ plane as a compromise between the top of the holder becoming to thin and the bottom becoming to wide.<br />
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[[Image:HolderTop1-11.jpg|thumb|400px|right|text-top|Applying draft to the side faces of the holder]]<br />
To put draft on a face, select this face and create the draft feature. You can then select more faces to apply the draft on. If you have a large part, it is advisable to draft only one face at a time. This means that if you change the geometry and a draft fails, only this one feature will fail, whereas if you put all faces in one draft feature, then the whole feature might fail because of one face failing. For a small part like the bearing holder, its sufficient to create two draft features: One for the four outside faces, and one for the inside faces.<br />
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The dialog will force you to select a neutral plane before completing. You can leave the pull direction empty, in this case it will be normal to the neutral plane. Don't forget to set the draft angle to 2 degrees.<br />
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== Filleting the holder ==<br />
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[[Image:HolderTop1-13.jpg|thumb|400px|right|text-top|Fillet where the bolts will go]]<br />
We can now fillet the part. The picture shows the first set of fillets. Start with the small circular fillets and make them 4mm radius. Even though 3mm would be enough as per specification of the part, a radius of 4mm means that after machining 1mm of the fillet is left, reducing the sharp edge produced by the machining. The large fillets are 6mm radius to help spread the force from the bolts into the rest of the part. It would be nice to make this radius even larger, but unfortunately OpenCascade can't handle overlapping fillets yet.<br />
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As with drafts, in a complex part you should fillet only one edge at a time to avoid unnecessary failures if the base geometry changes.<br />
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[[Image:HolderTop1-12.jpg|thumb|400px|right|text-top|Filleting the outside of the holder]]<br />
The rest of the fillets are simply 3mm radius. Looking at the picture on the right, the two highlighted fillets could actually be filleted with 5mm to achieve a more uniform wall thickness for the casting. After machining, the minimum wall thickness of 5mm would still be maintained. But again the fact that OpenCascade can't handle overlapping fillets prevents us from doing this for the inner of the two highlighted fillets.<br />
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[[Image:HolderTop1-14.jpg|thumb|400px|right|text-top|Filleting the inside of the holder - problematic edge]]<br />
Filleting the inside of the part presents us with a difficulty that cannot be solved with the current tools in the PartDesign workbench. The highlighted edge cannot be filleted at all, again because the rounds would overlap. This could be worked around by creating a sweep instead of a fillet, except that sweeps are not implemented in PartDesign yet. For the time being, we are forced to leave the edge as it is.<br />
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[[Image:HolderTop1-15.jpg|thumb|400px|right|text-top|The filleted part (except for the impossible edge)]]<br />
The picture on the right shows the finished part in the state it will be before machining (except for the one edge that is impossible to fillet). You will notice that one edge that runs around the whole part has been left unfilleted on purpose. This is the edge where the bottom and the top of the mould meet. Here, no fillet is possible (and none is required anyway).<br />
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== Machining ==<br />
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[[Image:HolderTop1-16.jpg|thumb|400px|right|text-top|Machining the top and bottom of the holder]]<br />
[[Image:HolderTop1-17.jpg|thumb|400px|right|text-top|Machining the inside of the bearing holder]]<br />
Now we can cut away the material that will be machined off the raw cast part. This is very easy with the skeleton geometry defined. The idea is to create all machining features (Pockets and Grooves) using datum features only. This means they will be totally independent of the solid geometry of the bearing holder, which gives us some big advantages:<br />
* No matter how you change the solid geometry, the features for the machining can never fail.<br />
* You can create the machining geometry before finalizing the solid, which gives you useful visual feedback.<br />
* If you move the skeleton datum planes, then both the solid geometry and the machining will adapt automatically.<br />
* If you make a mistake in your solid geometry, the machining will still be in the correct position, and very likely the mistake will become glaringly obvious (e.g. a wall thickness becoming 2mm instead of 5mm). Whereas if you reference the machining to the solid geometry, it will adapt to the error in the solid and e.g. maintain the 5mm wall thickness, just in the same wrong location as the solid is.<br />
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Before starting on the machining geometry, I like to place a datum point in the tree and name it something like "Machining_starts_here". This is useful if you want to switch between the raw and the machined state of the part because you can see at a glance where to move the insert point to get the raw state.<br />
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To machine the bottom of the holder, just sketch a large rectangle on the XZ plane and pocket it. For the top, sketch a circle on the datum plane defining the bolt head location, and then mirror the pocket on the YZ plane. In the same way, create a pocket for the hole which the bolt will go through and mirror it. To machine the inside of the holder, create a sketch on the YZ plane and groove it.<br />
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[[Image:HolderTop1-1.jpg|thumb|400px|right|text-top|Finished part]]<br />
Once you have done the machining, you can have a nice visual effect by colouring all the machined faces so that you can see at one glance which parts are raw casting and which are machined after casting.<br />
<br />
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<br />
== Final notes ==<br />
<br />
We have modelled the bearing holder top with the dimensions it will have after casting. To create the casting mould, you need to apply shrinkage to your part because after casting, when the hot metal cools down, it will shrink by a few percent (depending on the material). Usually it is best to leave the application of shrinkage to the foundry making the part because they have the required special knowledge. They should also tell you if your part has problematic areas, e.g. very thick walls suddenly joining to very thin sections without a properly tapered section between them.<br />
<br />
{{languages | {{it|PartDesign_Bearingholder_Tutorial_I/it}} }}<br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_I&diff=40461PartDesign Bearingholder Tutorial I2013-07-26T06:09:06Z<p>Jrheinlaender: </p>
<hr />
<div>{{VeryImportantMessage|'''This tutorial is for the development version of FreeCAD. Compile from here: https://github.com/jrheinlaender/FreeCAD/tree/jrheinlaender/dev-assembly-partdesign'''}}<br />
<br />
[[Image:HolderTop1-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the first part of the tutorial. It will use what might be called the 'single body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br />
You can find my version of the part created by this tutorial [[http://ubuntuone.com/5gok0J4dye3Fo4BKWMGWVa here]].<br />
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<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
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== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop1-2.jpg|Bearing holder with the two most important skeleton planes|thumb|right|text-top|400px]]<br />
<br />
The idea of skeleton geometry is to capture the basic design dimensions in a single datum feature (e.g. a plane or an axis). When the design dimension changes, all that needs to be done is to change the skeleton feature. If the model is well built, then all its feature will recompute to reflect the design change. This reduces the danger that in a complex model, where the basic design dimensions are used in multiple places, you forget to change it somewhere.<br />
<br />
The alternative to skeleton geometry is to have a table of the basic design dimensions that assign a symbolic name to each dimension, and then use the symbolic name wherever the dimensions is required to build the model. FreeCAD does not allow this approach yet.<br />
<br />
[[Image:HolderTop1-3.jpg|Base planes and all datum planes|thumb|right|text-top|400px]]<br />
<br />
For the case of the bearing holder, the two most important design dimensions are the distance between the bolts (which limits the size of the bearing that can be used) and the height of the bolt heads. The dimensions chosen are<br />
* Distance between bolts: Radius of bearing (45) + wall thickness (5) plus radius of hole for bolt (7) = 57mm, so the vertical plane will be 57mm offset from the YZ-plane. To create this datum plane, select the YZ-plane and then choose to create a new datum plane. Enter the offset in the dialog that opens up<br />
* Height of bolt heads: This was chosen as an offset of 28mm from the XZ-plane<br />
<br />
For convenience, two further datum planes can be created to reflect the amount of material that must be cut away from the sides of the bearing holder. They are offset +22 and -22 from the XY-plane.<br />
<br />
It is advisable to give clear names to the skeleton geometry. Most of the time, you will want to turn off visibility for datum planes because they clutter up the screen, and if the planes have self-explanatory names you can just pick them by name instead of from the screen.<br />
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<br />
== The solid geometry ==<br />
<br />
[[Image:HolderTop1-4.jpg|thumb|400px|right|text-top|Sketch of the first pad]]<br />
Now its time to start creating some real geometry. The sketch for the first pad is shown on the right. It is placed on the XY-plane. There are just three dimensions: The inner radius (22.5mm), the machining allowance (3mm) at the base as an offset to the XZ-plane and the distance from the datum plane representing the bolt axis (7mm). This means that if you later move the datum plane, the pad will automatically adjust its outer radius. Remember that before you can use the datum plane for dimensioning, you need to introduce it as external geometry to the sketcher.<br />
<br />
You are probably wondering why there is a small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), just pad it symmetrically to the sketch plane with a length of 62mm: 34mm for the bearing, 2x 9mm for the sealing rings, 2x 5mm for the wall thickness.<br />
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<br />
[[Image:HolderTop1-5.jpg|thumb|400px|right|text-top|Sketch of the cut-away at the side of the pad]]<br />
Next we want to cut away some material where the sealing rings are, because their outer diameter is much less than the bearing's. The easiest way to create the sketches is to select the sketch of the pad and then choose "Duplicate selection" from the edit menu. You can then remap the sketch to the side of the pad, and modify it as shown in the picture.<br />
<br />
The only two important dimensions in the sketch are 3mm of machining allowance at the bottom, and a inner diameter of 78mm: 68mm for the outer diameter of the sealing ring + 2x 5mm wall thickness. Since the sealing ring on the other side will only have a diameter of 55mm, the cut-out can be 65mm here.<br />
<br />
After you have created the sketch, pocket it up to the datum plane marking the bearing side plus 5mm wall thickness. If you ever want to modify the holder to be able to hold wider bearings, all you have to do is to change the dimension of these datum planes, and the cut-out depth will follow along.<br />
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<br />
[[Image:HolderTop1-6.jpg|thumb|400px|right|text-top|Sketch of the cut-away inside the pad]]<br />
To reduce the amount of machining required, we also want to cut away some material inside the holder. Again, duplicating the sketch of the first pad is convenient. It doesn't even have to be remapped. Again, the only important dimensions are the machining allowance (3mm) and the outer diameters: 84mm for the place where the bearing will be (90mm - 2x machining allowance), 49mm for the smaller sealing ring (55mm - 2x 3mm) and 62mm for the larger sealing ring.<br />
<br />
After creating the sketches, pocket them: Symetrically 28mm for the bearing cut-out (34mm - 2x machining allowance) and one-sided 23mm for the cut-outs for the sealing rings: 34mm / 2 for half the bearing width + 9mm for the sealing rings - 3mm machining allowance. <br />
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<br />
[[Image:HolderTop1-7.jpg|thumb|400px|right|text-top|Main geometry of the holder top]]<br />
Your part should now look like the picture on the right. Note how the different cut-aways combine to create an almost uniform wall thickness, which will make the casting easier and less liable to have pores.<br />
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<br />
[[Image:HolderTop1-8.jpg|thumb|400px|right|text-top|Sketch with draft where the bolts will be]]<br />
Now all that remains is to create some material for the bolts to go through. You might be tempted to sketch these as a circle and then pad them, but this will head you for trouble when you try to put the draft onto them later (I assume that is a weakness of OpenCascade). So to circumvent the problems, it is better to create a sketch with the draft angle included and then rotate it through 360 degrees.<br />
<br />
Here again the skeleton planes come in useful. You will need the bolt axis plane and the bolt head plane as external geometry. Then, create a straight line for the rotation axis and make sure it is constrained to the bolt axis plane reference. Toggle it to be construction geometry. Then, sketch the rest of the contour. The important dimensions are the machining allowance at the top and bottom and the radius of 12mm: 7mm for the hole radius + 5mm wall thickness.<br />
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<br />
[[Image:HolderTop1-9.jpg|thumb|400px|right|text-top|Finished geometry of the holder top (without draft and fillets)]]<br />
Create a revolution feature from the sketch and then mirror it on the YZ-plane. This is all the solid geometry we need to model. The rest is draft and fillets.<br />
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<br />
== Applying draft to the side faces ==<br />
<br />
[[Image:HolderTop1-10.jpg|thumb|400px|right|text-top|The neutral plane for creating drafts]]<br />
The next step is to apply drafts on all faces. Its important to consider the location of the neutral plane, that is, the plane which the face is "rotated" around. If we choose as neutral plane the bottom of the holder, then we will have a problem with the wall thickness in the top part of the holder. Therefore, we create a datum plane at an offset of 40mm from the XZ plane as a compromise between the top of the holder becoming to thin and the bottom becoming to wide.<br />
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<br />
[[Image:HolderTop1-11.jpg|thumb|400px|right|text-top|Applying draft to the side faces of the holder]]<br />
To put draft on a face, select this face and create the draft feature. You can then select more faces to apply the draft on. If you have a large part, it is advisable to draft only one face at a time. This means that if you change the geometry and a draft fails, only this one feature will fail, whereas if you put all faces in one draft feature, then the whole feature might fail because of one face failing. For a small part like the bearing holder, its sufficient to create two draft features: One for the four outside faces, and one for the inside faces.<br />
<br />
The dialog will force you to select a neutral plane before completing. You can leave the pull direction empty, in this case it will be normal to the neutral plane. Don't forget to set the draft angle to 2 degrees.<br />
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<br />
== Filleting the holder ==<br />
<br />
[[Image:HolderTop1-13.jpg|thumb|400px|right|text-top|Fillet where the bolts will go]]<br />
We can now fillet the part. The picture shows the first set of fillets. Start with the small circular fillets and make them 4mm radius. Even though 3mm would be enough as per specification of the part, a radius of 4mm means that after machining 1mm of the fillet is left, reducing the sharp edge produced by the machining. The large fillets are 6mm radius to help spread the force from the bolts into the rest of the part. It would be nice to make this radius even larger, but unfortunately OpenCascade can't handle overlapping fillets yet.<br />
<br />
As with drafts, in a complex part you should fillet only one edge at a time to avoid unnecessary failures if the base geometry changes.<br />
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<br />
[[Image:HolderTop1-12.jpg|thumb|400px|right|text-top|Filleting the outside of the holder]]<br />
The rest of the fillets are simply 3mm radius. Looking at the picture on the right, the two highlighted fillets could actually be filleted with 5mm to achieve a more uniform wall thickness for the casting. After machining, the minimum wall thickness of 5mm would still be maintained. But again the fact that OpenCascade can't handle overlapping fillets prevents us from doing this for the inner of the two highlighted fillets.<br />
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<br />
[[Image:HolderTop1-14.jpg|thumb|400px|right|text-top|Filleting the inside of the holder - problematic edge]]<br />
Filleting the inside of the part presents us with a difficulty that cannot be solved with the current tools in the PartDesign workbench. The highlighted edge cannot be filleted at all, again because the rounds would overlap. This could be worked around by creating a sweep instead of a fillet, except that sweeps are not implemented in PartDesign yet. For the time being, we are forced to leave the edge as it is.<br />
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<br />
[[Image:HolderTop1-15.jpg|thumb|400px|right|text-top|The filleted part (except for the impossible edge)]]<br />
The picture on the right shows the finished part in the state it will be before machining (except for the one edge that is impossible to fillet). You will notice that one edge that runs around the whole part has been left unfilleted on purpose. This is the edge where the bottom and the top of the mould meet. Here, no fillet is possible (and none is required anyway).<br />
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<br />
== Machining ==<br />
<br />
[[Image:HolderTop1-16.jpg|thumb|400px|right|text-top|Machining the top and bottom of the holder]]<br />
[[Image:HolderTop1-17.jpg|thumb|400px|right|text-top|Machining the inside of the bearing holder]]<br />
Now we can cut away the material that will be machined off the raw cast part. This is very easy with the skeleton geometry defined. The idea is to create all machining features (Pockets and Grooves) using datum features only. This means they will be totally independent of the solid geometry of the bearing holder, which gives us some big advantages:<br />
* No matter how you change the solid geometry, the features for the machining can never fail.<br />
* You can create the machining geometry before finalizing the solid, which gives you useful visual feedback.<br />
* If you move the skeleton datum planes, then both the solid geometry and the machining will adapt automatically.<br />
* If you make a mistake in your solid geometry, the machining will still be in the correct position, and very likely the mistake will become glaringly obvious (e.g. a wall thickness becoming 2mm instead of 5mm). Whereas if you reference the machining to the solid geometry, it will adapt to the error in the solid and e.g. maintain the 5mm wall thickness, just in the same wrong location as the solid is.<br />
<br />
Before starting on the machining geometry, I like to place a datum point in the tree and name it something like "Machining_starts_here". This is useful if you want to switch between the raw and the machined state of the part because you can see at a glance where to move the insert point to get the raw state.<br />
<br />
To machine the bottom of the holder, just sketch a large rectangle on the XZ plane and pocket it. For the top, sketch a circle on the datum plane defining the bolt head location, and then mirror the pocket on the YZ plane. In the same way, create a pocket for the hole which the bolt will go through and mirror it. To machine the inside of the holder, create a sketch on the YZ plane and groove it.<br />
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<br />
[[Image:HolderTop1-1.jpg|thumb|400px|right|text-top|Finished part]]<br />
Once you have done the machining, you can have a nice visual effect by colouring all the machined faces so that you can see at one glance which parts are raw casting and which are machined after casting.<br />
<br />
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<br />
== Final notes ==<br />
<br />
We have modelled the bearing holder top with the dimensions it will have after casting. To create the casting mould, you need to apply shrinkage to your part because after casting, when the hot metal cools down, it will shrink by a few percent (depending on the material). Usually it is best to leave the application of shrinkage to the foundry making the part because they have the required special knowledge. They should also tell you if your part has problematic areas, e.g. very thick walls suddenly joining to very thin sections without a properly tapered section between them.<br />
<br />
{{languages | {{it|PartDesign_Bearingholder_Tutorial_I/it}} }}<br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=40451PartDesign Bearingholder Tutorial II2013-07-26T06:08:44Z<p>Jrheinlaender: </p>
<hr />
<div>{{VeryImportantMessage|'''This tutorial is for the development version of FreeCAD. Compile from here: https://github.com/jrheinlaender/FreeCAD/tree/jrheinlaender/dev-assembly-partdesign'''}}<br />
<br />
[[Image:HolderTop2-19.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br />
You can find my version of the part created in this tutorial [[http://ubuntuone.com/39PTZ3Y3LUnmZzpZQPcJT4 here]]<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. The head of such a bolt will require at least 20mm diameter free space. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
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<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
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<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
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<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
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<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
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<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
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<br />
== Adding the bodies for the bolts ==<br />
<br />
[[Image:HolderTop2-13.jpg|The sketch for the body for the bolts|thumb|right|400px]]<br />
The bolts need two cylindrical bodies on both sides of the main Body. It is best to include the 2 degree draft angle in the sketch. I tried revolving a cylinder and later applying a draft, but weird things happened after mirroring it and I couldn't put fillets on it because the surface was warped somehow.<br />
<br />
The sketch is dimensioned so that the rotation axis is 12mm distance to the outer diameter of the skeleton Body, 7mm for the radius of the hole plus 5mm for the wall thickness. For the sake of having a fully parametric part, it is a good idea to add a plane to the Skeleton about 25mm above the XY-plane to mark the top of the cylinders. Since this will be machined, the sketch is dimensioned 3mm above it.<br />
<br />
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<br />
[[Image:HolderTop2-14.jpg|The body for the bolts|thumb|right|400px]]<br />
Create a revolution from the sketch and apply a fillet of 4mm to the top. This means that after machining away 3mm, a slight radius will remain which helps to avoid a sharp edge where someone could cut their hand when tightening the bolt.<br />
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<br />
[[Image:HolderTop2-16.jpg|The main body with the two bodies for the bolts|thumb|right|400px]]<br />
Create a boolean feature to fuse the main Body and the bolt body. Then create a new body for the other side. Duplicate the sketch of the revolution, move it to this body and create the second body for the bolts (mirroring a Body is not supported yet so you need to redo most of it). Then fuse this second body into the main Body as well. Finally, apply a large fillet on the edge created by the boolean fuse operation. The largest I could get was 4mm.<br />
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<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
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<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
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<br />
[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
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<br />
[[Image:HolderTop2-15.jpg|The completed raw part of the holder (without machining)|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". Put a 3mm fillet on the two edges resulting from the cut-out operation (again some edges remain that are "unfilletable"). The result should look like the picture on the right.<br />
<br />
The raw part is now completed. This is what the holder will look like before machining. Note that since the mold will have a top and bottom half, the edge between these two cannot be filleted. Also, if you give away this model to a foundry make sure to point out that it has the dimensions after casting. The foundry will then have to apply a certain percentage of shrinkage to the model (making the digital model used to manufacture the mold larger so that when the metal cools down and shrinks after casting it will have the right size).<br />
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<br />
== Machining ==<br />
<br />
[[Image:HolderTop2-17.jpg|Sketch to "drill" the hole for the bolts|thumb|right|400px]]<br />
To take away the material for machining the inside of the holder, very conveniently we can use the Skeleton Body itself. If you don't want that because then the skeleton gets hidden somewhere deep in the tree, you can also duplicate the sketch of the skeleton Revolution feature and re-create the revolution in another body. This is not completely parametric, though, because the duplicated sketch is independent of the original, so you will have to work on both if you change a dimension. Dependent duplicated features might be supported in the future sometime.<br />
<br />
For the rest of the machining, create a new Body. The bottom of the holder will be machined by a Pad sketched on the XY-plane extending downwards. Next, sketch a revolution to make a hole for the bolts. You will need to sketch on the XZ-plane and revolve it so that you can choose the outer diameter of the skeleton Body as an external reference. The top part of the sketch will serve to machine a flat place for the head of the bolt. It is dimensioned to leave at least 5mm wall thickness in the holder. If this does not give enough space for the bolt head then you can move the datum plane upwards. Of course, you could put this logic into the Skeleton, which is left as an exercise to the reader!<br />
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<br />
[[Image:HolderTop2-18.jpg|The machining Body|thumb|right|400px]]<br />
You can mirror the revolution on the YZ-axis. The picture on the right shows the "machining" Body. Of course, most of the dimensions of the Pads and Revolutions are not important as long as there is plenty of overlap.<br />
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<br />
[[Image:HolderTop2-19.jpg|The finished Holder with machining|thumb|right|400px]]<br />
Finally, create a boolean operation to cut the machining Body out of the main Body. If you want a nice visual effect, you can colour the machined surfaces differently from the rest of the part. This is also a useful optical feedback showing you whether you forgot to machine somewhere.<br />
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{{languages | {{it|PartDesign_Bearingholder_Tutorial_II/it}} }}<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=40401PartDesign Bearingholder Tutorial II2013-07-25T17:21:24Z<p>Jrheinlaender: </p>
<hr />
<div>[[Image:HolderTop2-19.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br />
You can find my version of the part created in this tutorial [[http://ubuntuone.com/39PTZ3Y3LUnmZzpZQPcJT4 here]]<br />
<br />
WARNING: THIS TUTORIAL IS FOR THE DEVELOPMENT VERSION OF FREECAD. <br />
Compile from here: https://github.com/jrheinlaender/FreeCAD/tree/jrheinlaender/dev-assembly-partdesign<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. The head of such a bolt will require at least 20mm diameter free space. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
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<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
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<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
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<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
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<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
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<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
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<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
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<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
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<br />
== Adding the bodies for the bolts ==<br />
<br />
[[Image:HolderTop2-13.jpg|The sketch for the body for the bolts|thumb|right|400px]]<br />
The bolts need two cylindrical bodies on both sides of the main Body. It is best to include the 2 degree draft angle in the sketch. I tried revolving a cylinder and later applying a draft, but weird things happened after mirroring it and I couldn't put fillets on it because the surface was warped somehow.<br />
<br />
The sketch is dimensioned so that the rotation axis is 12mm distance to the outer diameter of the skeleton Body, 7mm for the radius of the hole plus 5mm for the wall thickness. For the sake of having a fully parametric part, it is a good idea to add a plane to the Skeleton about 25mm above the XY-plane to mark the top of the cylinders. Since this will be machined, the sketch is dimensioned 3mm above it.<br />
<br />
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<br />
[[Image:HolderTop2-14.jpg|The body for the bolts|thumb|right|400px]]<br />
Create a revolution from the sketch and apply a fillet of 4mm to the top. This means that after machining away 3mm, a slight radius will remain which helps to avoid a sharp edge where someone could cut their hand when tightening the bolt.<br />
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<br />
[[Image:HolderTop2-16.jpg|The main body with the two bodies for the bolts|thumb|right|400px]]<br />
Create a boolean feature to fuse the main Body and the bolt body. Then create a new body for the other side. Duplicate the sketch of the revolution, move it to this body and create the second body for the bolts (mirroring a Body is not supported yet so you need to redo most of it). Then fuse this second body into the main Body as well. Finally, apply a large fillet on the edge created by the boolean fuse operation. The largest I could get was 4mm.<br />
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<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
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<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
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<br />
[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
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<br />
[[Image:HolderTop2-15.jpg|The completed raw part of the holder (without machining)|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". Put a 3mm fillet on the two edges resulting from the cut-out operation (again some edges remain that are "unfilletable"). The result should look like the picture on the right.<br />
<br />
The raw part is now completed. This is what the holder will look like before machining. Note that since the mold will have a top and bottom half, the edge between these two cannot be filleted. Also, if you give away this model to a foundry make sure to point out that it has the dimensions after casting. The foundry will then have to apply a certain percentage of shrinkage to the model (making the digital model used to manufacture the mold larger so that when the metal cools down and shrinks after casting it will have the right size).<br />
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<br />
== Machining ==<br />
<br />
[[Image:HolderTop2-17.jpg|Sketch to "drill" the hole for the bolts|thumb|right|400px]]<br />
To take away the material for machining the inside of the holder, very conveniently we can use the Skeleton Body itself. If you don't want that because then the skeleton gets hidden somewhere deep in the tree, you can also duplicate the sketch of the skeleton Revolution feature and re-create the revolution in another body. This is not completely parametric, though, because the duplicated sketch is independent of the original, so you will have to work on both if you change a dimension. Dependent duplicated features might be supported in the future sometime.<br />
<br />
For the rest of the machining, create a new Body. The bottom of the holder will be machined by a Pad sketched on the XY-plane extending downwards. Next, sketch a revolution to make a hole for the bolts. You will need to sketch on the XZ-plane and revolve it so that you can choose the outer diameter of the skeleton Body as an external reference. The top part of the sketch will serve to machine a flat place for the head of the bolt. It is dimensioned to leave at least 5mm wall thickness in the holder. If this does not give enough space for the bolt head then you can move the datum plane upwards. Of course, you could put this logic into the Skeleton, which is left as an exercise to the reader!<br />
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<br />
[[Image:HolderTop2-18.jpg|The machining Body|thumb|right|400px]]<br />
You can mirror the revolution on the YZ-axis. The picture on the right shows the "machining" Body. Of course, most of the dimensions of the Pads and Revolutions are not important as long as there is plenty of overlap.<br />
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<br />
[[Image:HolderTop2-19.jpg|The finished Holder with machining|thumb|right|400px]]<br />
Finally, create a boolean operation to cut the machining Body out of the main Body. If you want a nice visual effect, you can colour the machined surfaces differently from the rest of the part. This is also a useful optical feedback showing you whether you forgot to machine somewhere.<br />
<br clear=all><br />
{{languages | {{it|PartDesign_Bearingholder_Tutorial_II/it}} }}<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_I&diff=40391PartDesign Bearingholder Tutorial I2013-07-25T17:20:59Z<p>Jrheinlaender: </p>
<hr />
<div>[[Image:HolderTop1-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the first part of the tutorial. It will use what might be called the 'single body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br />
You can find my version of the part created by this tutorial [[http://ubuntuone.com/5gok0J4dye3Fo4BKWMGWVa here]].<br />
<br />
WARNING: THIS TUTORIAL IS FOR THE DEVELOPMENT VERSION OF FREECAD. <br />
Compile from here: https://github.com/jrheinlaender/FreeCAD/tree/jrheinlaender/dev-assembly-partdesign<br />
<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
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== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop1-2.jpg|Bearing holder with the two most important skeleton planes|thumb|right|text-top|400px]]<br />
<br />
The idea of skeleton geometry is to capture the basic design dimensions in a single datum feature (e.g. a plane or an axis). When the design dimension changes, all that needs to be done is to change the skeleton feature. If the model is well built, then all its feature will recompute to reflect the design change. This reduces the danger that in a complex model, where the basic design dimensions are used in multiple places, you forget to change it somewhere.<br />
<br />
The alternative to skeleton geometry is to have a table of the basic design dimensions that assign a symbolic name to each dimension, and then use the symbolic name wherever the dimensions is required to build the model. FreeCAD does not allow this approach yet.<br />
<br />
[[Image:HolderTop1-3.jpg|Base planes and all datum planes|thumb|right|text-top|400px]]<br />
<br />
For the case of the bearing holder, the two most important design dimensions are the distance between the bolts (which limits the size of the bearing that can be used) and the height of the bolt heads. The dimensions chosen are<br />
* Distance between bolts: Radius of bearing (45) + wall thickness (5) plus radius of hole for bolt (7) = 57mm, so the vertical plane will be 57mm offset from the YZ-plane. To create this datum plane, select the YZ-plane and then choose to create a new datum plane. Enter the offset in the dialog that opens up<br />
* Height of bolt heads: This was chosen as an offset of 28mm from the XZ-plane<br />
<br />
For convenience, two further datum planes can be created to reflect the amount of material that must be cut away from the sides of the bearing holder. They are offset +22 and -22 from the XY-plane.<br />
<br />
It is advisable to give clear names to the skeleton geometry. Most of the time, you will want to turn off visibility for datum planes because they clutter up the screen, and if the planes have self-explanatory names you can just pick them by name instead of from the screen.<br />
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<br />
== The solid geometry ==<br />
<br />
[[Image:HolderTop1-4.jpg|thumb|400px|right|text-top|Sketch of the first pad]]<br />
Now its time to start creating some real geometry. The sketch for the first pad is shown on the right. It is placed on the XY-plane. There are just three dimensions: The inner radius (22.5mm), the machining allowance (3mm) at the base as an offset to the XZ-plane and the distance from the datum plane representing the bolt axis (7mm). This means that if you later move the datum plane, the pad will automatically adjust its outer radius. Remember that before you can use the datum plane for dimensioning, you need to introduce it as external geometry to the sketcher.<br />
<br />
You are probably wondering why there is a small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), just pad it symmetrically to the sketch plane with a length of 62mm: 34mm for the bearing, 2x 9mm for the sealing rings, 2x 5mm for the wall thickness.<br />
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<br />
[[Image:HolderTop1-5.jpg|thumb|400px|right|text-top|Sketch of the cut-away at the side of the pad]]<br />
Next we want to cut away some material where the sealing rings are, because their outer diameter is much less than the bearing's. The easiest way to create the sketches is to select the sketch of the pad and then choose "Duplicate selection" from the edit menu. You can then remap the sketch to the side of the pad, and modify it as shown in the picture.<br />
<br />
The only two important dimensions in the sketch are 3mm of machining allowance at the bottom, and a inner diameter of 78mm: 68mm for the outer diameter of the sealing ring + 2x 5mm wall thickness. Since the sealing ring on the other side will only have a diameter of 55mm, the cut-out can be 65mm here.<br />
<br />
After you have created the sketch, pocket it up to the datum plane marking the bearing side plus 5mm wall thickness. If you ever want to modify the holder to be able to hold wider bearings, all you have to do is to change the dimension of these datum planes, and the cut-out depth will follow along.<br />
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<br />
[[Image:HolderTop1-6.jpg|thumb|400px|right|text-top|Sketch of the cut-away inside the pad]]<br />
To reduce the amount of machining required, we also want to cut away some material inside the holder. Again, duplicating the sketch of the first pad is convenient. It doesn't even have to be remapped. Again, the only important dimensions are the machining allowance (3mm) and the outer diameters: 84mm for the place where the bearing will be (90mm - 2x machining allowance), 49mm for the smaller sealing ring (55mm - 2x 3mm) and 62mm for the larger sealing ring.<br />
<br />
After creating the sketches, pocket them: Symetrically 28mm for the bearing cut-out (34mm - 2x machining allowance) and one-sided 23mm for the cut-outs for the sealing rings: 34mm / 2 for half the bearing width + 9mm for the sealing rings - 3mm machining allowance. <br />
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<br />
[[Image:HolderTop1-7.jpg|thumb|400px|right|text-top|Main geometry of the holder top]]<br />
Your part should now look like the picture on the right. Note how the different cut-aways combine to create an almost uniform wall thickness, which will make the casting easier and less liable to have pores.<br />
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<br />
[[Image:HolderTop1-8.jpg|thumb|400px|right|text-top|Sketch with draft where the bolts will be]]<br />
Now all that remains is to create some material for the bolts to go through. You might be tempted to sketch these as a circle and then pad them, but this will head you for trouble when you try to put the draft onto them later (I assume that is a weakness of OpenCascade). So to circumvent the problems, it is better to create a sketch with the draft angle included and then rotate it through 360 degrees.<br />
<br />
Here again the skeleton planes come in useful. You will need the bolt axis plane and the bolt head plane as external geometry. Then, create a straight line for the rotation axis and make sure it is constrained to the bolt axis plane reference. Toggle it to be construction geometry. Then, sketch the rest of the contour. The important dimensions are the machining allowance at the top and bottom and the radius of 12mm: 7mm for the hole radius + 5mm wall thickness.<br />
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<br />
[[Image:HolderTop1-9.jpg|thumb|400px|right|text-top|Finished geometry of the holder top (without draft and fillets)]]<br />
Create a revolution feature from the sketch and then mirror it on the YZ-plane. This is all the solid geometry we need to model. The rest is draft and fillets.<br />
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<br />
== Applying draft to the side faces ==<br />
<br />
[[Image:HolderTop1-10.jpg|thumb|400px|right|text-top|The neutral plane for creating drafts]]<br />
The next step is to apply drafts on all faces. Its important to consider the location of the neutral plane, that is, the plane which the face is "rotated" around. If we choose as neutral plane the bottom of the holder, then we will have a problem with the wall thickness in the top part of the holder. Therefore, we create a datum plane at an offset of 40mm from the XZ plane as a compromise between the top of the holder becoming to thin and the bottom becoming to wide.<br />
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<br />
[[Image:HolderTop1-11.jpg|thumb|400px|right|text-top|Applying draft to the side faces of the holder]]<br />
To put draft on a face, select this face and create the draft feature. You can then select more faces to apply the draft on. If you have a large part, it is advisable to draft only one face at a time. This means that if you change the geometry and a draft fails, only this one feature will fail, whereas if you put all faces in one draft feature, then the whole feature might fail because of one face failing. For a small part like the bearing holder, its sufficient to create two draft features: One for the four outside faces, and one for the inside faces.<br />
<br />
The dialog will force you to select a neutral plane before completing. You can leave the pull direction empty, in this case it will be normal to the neutral plane. Don't forget to set the draft angle to 2 degrees.<br />
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<br />
== Filleting the holder ==<br />
<br />
[[Image:HolderTop1-13.jpg|thumb|400px|right|text-top|Fillet where the bolts will go]]<br />
We can now fillet the part. The picture shows the first set of fillets. Start with the small circular fillets and make them 4mm radius. Even though 3mm would be enough as per specification of the part, a radius of 4mm means that after machining 1mm of the fillet is left, reducing the sharp edge produced by the machining. The large fillets are 6mm radius to help spread the force from the bolts into the rest of the part. It would be nice to make this radius even larger, but unfortunately OpenCascade can't handle overlapping fillets yet.<br />
<br />
As with drafts, in a complex part you should fillet only one edge at a time to avoid unnecessary failures if the base geometry changes.<br />
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<br />
[[Image:HolderTop1-12.jpg|thumb|400px|right|text-top|Filleting the outside of the holder]]<br />
The rest of the fillets are simply 3mm radius. Looking at the picture on the right, the two highlighted fillets could actually be filleted with 5mm to achieve a more uniform wall thickness for the casting. After machining, the minimum wall thickness of 5mm would still be maintained. But again the fact that OpenCascade can't handle overlapping fillets prevents us from doing this for the inner of the two highlighted fillets.<br />
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<br />
[[Image:HolderTop1-14.jpg|thumb|400px|right|text-top|Filleting the inside of the holder - problematic edge]]<br />
Filleting the inside of the part presents us with a difficulty that cannot be solved with the current tools in the PartDesign workbench. The highlighted edge cannot be filleted at all, again because the rounds would overlap. This could be worked around by creating a sweep instead of a fillet, except that sweeps are not implemented in PartDesign yet. For the time being, we are forced to leave the edge as it is.<br />
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<br />
[[Image:HolderTop1-15.jpg|thumb|400px|right|text-top|The filleted part (except for the impossible edge)]]<br />
The picture on the right shows the finished part in the state it will be before machining (except for the one edge that is impossible to fillet). You will notice that one edge that runs around the whole part has been left unfilleted on purpose. This is the edge where the bottom and the top of the mould meet. Here, no fillet is possible (and none is required anyway).<br />
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<br />
== Machining ==<br />
<br />
[[Image:HolderTop1-16.jpg|thumb|400px|right|text-top|Machining the top and bottom of the holder]]<br />
[[Image:HolderTop1-17.jpg|thumb|400px|right|text-top|Machining the inside of the bearing holder]]<br />
Now we can cut away the material that will be machined off the raw cast part. This is very easy with the skeleton geometry defined. The idea is to create all machining features (Pockets and Grooves) using datum features only. This means they will be totally independent of the solid geometry of the bearing holder, which gives us some big advantages:<br />
* No matter how you change the solid geometry, the features for the machining can never fail.<br />
* You can create the machining geometry before finalizing the solid, which gives you useful visual feedback.<br />
* If you move the skeleton datum planes, then both the solid geometry and the machining will adapt automatically.<br />
* If you make a mistake in your solid geometry, the machining will still be in the correct position, and very likely the mistake will become glaringly obvious (e.g. a wall thickness becoming 2mm instead of 5mm). Whereas if you reference the machining to the solid geometry, it will adapt to the error in the solid and e.g. maintain the 5mm wall thickness, just in the same wrong location as the solid is.<br />
<br />
Before starting on the machining geometry, I like to place a datum point in the tree and name it something like "Machining_starts_here". This is useful if you want to switch between the raw and the machined state of the part because you can see at a glance where to move the insert point to get the raw state.<br />
<br />
To machine the bottom of the holder, just sketch a large rectangle on the XZ plane and pocket it. For the top, sketch a circle on the datum plane defining the bolt head location, and then mirror the pocket on the YZ plane. In the same way, create a pocket for the hole which the bolt will go through and mirror it. To machine the inside of the holder, create a sketch on the YZ plane and groove it.<br />
<br clear=all><br />
<br />
[[Image:HolderTop1-1.jpg|thumb|400px|right|text-top|Finished part]]<br />
Once you have done the machining, you can have a nice visual effect by colouring all the machined faces so that you can see at one glance which parts are raw casting and which are machined after casting.<br />
<br />
<br clear=all><br />
<br />
== Final notes ==<br />
<br />
We have modelled the bearing holder top with the dimensions it will have after casting. To create the casting mould, you need to apply shrinkage to your part because after casting, when the hot metal cools down, it will shrink by a few percent (depending on the material). Usually it is best to leave the application of shrinkage to the foundry making the part because they have the required special knowledge. They should also tell you if your part has problematic areas, e.g. very thick walls suddenly joining to very thin sections without a properly tapered section between them.<br />
<br />
{{languages | {{it|PartDesign_Bearingholder_Tutorial_I/it}} }}<br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_I&diff=40211PartDesign Bearingholder Tutorial I2013-07-16T18:51:45Z<p>Jrheinlaender: </p>
<hr />
<div>[[Image:HolderTop1-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the first part of the tutorial. It will use what might be called the 'single body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br />
You can find my version of the part created by this tutorial [[http://ubuntuone.com/5gok0J4dye3Fo4BKWMGWVa here]].<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop1-2.jpg|Bearing holder with the two most important skeleton planes|thumb|right|text-top|400px]]<br />
<br />
The idea of skeleton geometry is to capture the basic design dimensions in a single datum feature (e.g. a plane or an axis). When the design dimension changes, all that needs to be done is to change the skeleton feature. If the model is well built, then all its feature will recompute to reflect the design change. This reduces the danger that in a complex model, where the basic design dimensions are used in multiple places, you forget to change it somewhere.<br />
<br />
The alternative to skeleton geometry is to have a table of the basic design dimensions that assign a symbolic name to each dimension, and then use the symbolic name wherever the dimensions is required to build the model. FreeCAD does not allow this approach yet.<br />
<br />
[[Image:HolderTop1-3.jpg|Base planes and all datum planes|thumb|right|text-top|400px]]<br />
<br />
For the case of the bearing holder, the two most important design dimensions are the distance between the bolts (which limits the size of the bearing that can be used) and the height of the bolt heads. The dimensions chosen are<br />
* Distance between bolts: Radius of bearing (45) + wall thickness (5) plus radius of hole for bolt (7) = 57mm, so the vertical plane will be 57mm offset from the YZ-plane. To create this datum plane, select the YZ-plane and then choose to create a new datum plane. Enter the offset in the dialog that opens up<br />
* Height of bolt heads: This was chosen as an offset of 28mm from the XZ-plane<br />
<br />
For convenience, two further datum planes can be created to reflect the amount of material that must be cut away from the sides of the bearing holder. They are offset +22 and -22 from the XY-plane.<br />
<br />
It is advisable to give clear names to the skeleton geometry. Most of the time, you will want to turn off visibility for datum planes because they clutter up the screen, and if the planes have self-explanatory names you can just pick them by name instead of from the screen.<br />
<br clear=all><br />
<br />
== The solid geometry ==<br />
<br />
[[Image:HolderTop1-4.jpg|thumb|400px|right|text-top|Sketch of the first pad]]<br />
Now its time to start creating some real geometry. The sketch for the first pad is shown on the right. It is placed on the XY-plane. There are just three dimensions: The inner radius (22.5mm), the machining allowance (3mm) at the base as an offset to the XZ-plane and the distance from the datum plane representing the bolt axis (7mm). This means that if you later move the datum plane, the pad will automatically adjust its outer radius. Remember that before you can use the datum plane for dimensioning, you need to introduce it as external geometry to the sketcher.<br />
<br />
You are probably wondering why there is a small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), just pad it symmetrically to the sketch plane with a length of 62mm: 34mm for the bearing, 2x 9mm for the sealing rings, 2x 5mm for the wall thickness.<br />
<br clear=all><br />
<br />
[[Image:HolderTop1-5.jpg|thumb|400px|right|text-top|Sketch of the cut-away at the side of the pad]]<br />
Next we want to cut away some material where the sealing rings are, because their outer diameter is much less than the bearing's. The easiest way to create the sketches is to select the sketch of the pad and then choose "Duplicate selection" from the edit menu. You can then remap the sketch to the side of the pad, and modify it as shown in the picture.<br />
<br />
The only two important dimensions in the sketch are 3mm of machining allowance at the bottom, and a inner diameter of 78mm: 68mm for the outer diameter of the sealing ring + 2x 5mm wall thickness. Since the sealing ring on the other side will only have a diameter of 55mm, the cut-out can be 65mm here.<br />
<br />
After you have created the sketch, pocket it up to the datum plane marking the bearing side plus 5mm wall thickness. If you ever want to modify the holder to be able to hold wider bearings, all you have to do is to change the dimension of these datum planes, and the cut-out depth will follow along.<br />
<br clear=all><br />
<br />
[[Image:HolderTop1-6.jpg|thumb|400px|right|text-top|Sketch of the cut-away inside the pad]]<br />
To reduce the amount of machining required, we also want to cut away some material inside the holder. Again, duplicating the sketch of the first pad is convenient. It doesn't even have to be remapped. Again, the only important dimensions are the machining allowance (3mm) and the outer diameters: 84mm for the place where the bearing will be (90mm - 2x machining allowance), 49mm for the smaller sealing ring (55mm - 2x 3mm) and 62mm for the larger sealing ring.<br />
<br />
After creating the sketches, pocket them: Symetrically 28mm for the bearing cut-out (34mm - 2x machining allowance) and one-sided 23mm for the cut-outs for the sealing rings: 34mm / 2 for half the bearing width + 9mm for the sealing rings - 3mm machining allowance. <br />
<br clear=all><br />
<br />
[[Image:HolderTop1-7.jpg|thumb|400px|right|text-top|Main geometry of the holder top]]<br />
Your part should now look like the picture on the right. Note how the different cut-aways combine to create an almost uniform wall thickness, which will make the casting easier and less liable to have pores.<br />
<br clear=all><br />
<br />
[[Image:HolderTop1-8.jpg|thumb|400px|right|text-top|Sketch with draft where the bolts will be]]<br />
Now all that remains is to create some material for the bolts to go through. You might be tempted to sketch these as a circle and then pad them, but this will head you for trouble when you try to put the draft onto them later (I assume that is a weakness of OpenCascade). So to circumvent the problems, it is better to create a sketch with the draft angle included and then rotate it through 360 degrees.<br />
<br />
Here again the skeleton planes come in useful. You will need the bolt axis plane and the bolt head plane as external geometry. Then, create a straight line for the rotation axis and make sure it is constrained to the bolt axis plane reference. Toggle it to be construction geometry. Then, sketch the rest of the contour. The important dimensions are the machining allowance at the top and bottom and the radius of 12mm: 7mm for the hole radius + 5mm wall thickness.<br />
<br clear=all><br />
<br />
[[Image:HolderTop1-9.jpg|thumb|400px|right|text-top|Finished geometry of the holder top (without draft and fillets)]]<br />
Create a revolution feature from the sketch and then mirror it on the YZ-plane. This is all the solid geometry we need to model. The rest is draft and fillets.<br />
<br clear=all><br />
<br />
== Applying draft to the side faces ==<br />
<br />
[[Image:HolderTop1-10.jpg|thumb|400px|right|text-top|The neutral plane for creating drafts]]<br />
The next step is to apply drafts on all faces. Its important to consider the location of the neutral plane, that is, the plane which the face is "rotated" around. If we choose as neutral plane the bottom of the holder, then we will have a problem with the wall thickness in the top part of the holder. Therefore, we create a datum plane at an offset of 40mm from the XZ plane as a compromise between the top of the holder becoming to thin and the bottom becoming to wide.<br />
<br clear=all><br />
<br />
[[Image:HolderTop1-11.jpg|thumb|400px|right|text-top|Applying draft to the side faces of the holder]]<br />
To put draft on a face, select this face and create the draft feature. You can then select more faces to apply the draft on. If you have a large part, it is advisable to draft only one face at a time. This means that if you change the geometry and a draft fails, only this one feature will fail, whereas if you put all faces in one draft feature, then the whole feature might fail because of one face failing. For a small part like the bearing holder, its sufficient to create two draft features: One for the four outside faces, and one for the inside faces.<br />
<br />
The dialog will force you to select a neutral plane before completing. You can leave the pull direction empty, in this case it will be normal to the neutral plane. Don't forget to set the draft angle to 2 degrees.<br />
<br clear=all><br />
<br />
== Filleting the holder ==<br />
<br />
[[Image:HolderTop1-13.jpg|thumb|400px|right|text-top|Fillet where the bolts will go]]<br />
We can now fillet the part. The picture shows the first set of fillets. Start with the small circular fillets and make them 4mm radius. Even though 3mm would be enough as per specification of the part, a radius of 4mm means that after machining 1mm of the fillet is left, reducing the sharp edge produced by the machining. The large fillets are 6mm radius to help spread the force from the bolts into the rest of the part. It would be nice to make this radius even larger, but unfortunately OpenCascade can't handle overlapping fillets yet.<br />
<br />
As with drafts, in a complex part you should fillet only one edge at a time to avoid unnecessary failures if the base geometry changes.<br />
<br clear=all><br />
<br />
[[Image:HolderTop1-12.jpg|thumb|400px|right|text-top|Filleting the outside of the holder]]<br />
The rest of the fillets are simply 3mm radius. Looking at the picture on the right, the two highlighted fillets could actually be filleted with 5mm to achieve a more uniform wall thickness for the casting. After machining, the minimum wall thickness of 5mm would still be maintained. But again the fact that OpenCascade can't handle overlapping fillets prevents us from doing this for the inner of the two highlighted fillets.<br />
<br clear=all><br />
<br />
[[Image:HolderTop1-14.jpg|thumb|400px|right|text-top|Filleting the inside of the holder - problematic edge]]<br />
Filleting the inside of the part presents us with a difficulty that cannot be solved with the current tools in the PartDesign workbench. The highlighted edge cannot be filleted at all, again because the rounds would overlap. This could be worked around by creating a sweep instead of a fillet, except that sweeps are not implemented in PartDesign yet. For the time being, we are forced to leave the edge as it is.<br />
<br clear=all><br />
<br />
[[Image:HolderTop1-15.jpg|thumb|400px|right|text-top|The filleted part (except for the impossible edge)]]<br />
The picture on the right shows the finished part in the state it will be before machining (except for the one edge that is impossible to fillet). You will notice that one edge that runs around the whole part has been left unfilleted on purpose. This is the edge where the bottom and the top of the mould meet. Here, no fillet is possible (and none is required anyway).<br />
<br clear=all><br />
<br />
== Machining ==<br />
<br />
[[Image:HolderTop1-16.jpg|thumb|400px|right|text-top|Machining the top and bottom of the holder]]<br />
[[Image:HolderTop1-17.jpg|thumb|400px|right|text-top|Machining the inside of the bearing holder]]<br />
Now we can cut away the material that will be machined off the raw cast part. This is very easy with the skeleton geometry defined. The idea is to create all machining features (Pockets and Grooves) using datum features only. This means they will be totally independent of the solid geometry of the bearing holder, which gives us some big advantages:<br />
* No matter how you change the solid geometry, the features for the machining can never fail.<br />
* You can create the machining geometry before finalizing the solid, which gives you useful visual feedback.<br />
* If you move the skeleton datum planes, then both the solid geometry and the machining will adapt automatically.<br />
* If you make a mistake in your solid geometry, the machining will still be in the correct position, and very likely the mistake will become glaringly obvious (e.g. a wall thickness becoming 2mm instead of 5mm). Whereas if you reference the machining to the solid geometry, it will adapt to the error in the solid and e.g. maintain the 5mm wall thickness, just in the same wrong location as the solid is.<br />
<br />
Before starting on the machining geometry, I like to place a datum point in the tree and name it something like "Machining_starts_here". This is useful if you want to switch between the raw and the machined state of the part because you can see at a glance where to move the insert point to get the raw state.<br />
<br />
To machine the bottom of the holder, just sketch a large rectangle on the XZ plane and pocket it. For the top, sketch a circle on the datum plane defining the bolt head location, and then mirror the pocket on the YZ plane. In the same way, create a pocket for the hole which the bolt will go through and mirror it. To machine the inside of the holder, create a sketch on the YZ plane and groove it.<br />
<br clear=all><br />
<br />
[[Image:HolderTop1-1.jpg|thumb|400px|right|text-top|Finished part]]<br />
Once you have done the machining, you can have a nice visual effect by colouring all the machined faces so that you can see at one glance which parts are raw casting and which are machined after casting.<br />
<br />
<br clear=all><br />
<br />
== Final notes ==<br />
<br />
We have modelled the bearing holder top with the dimensions it will have after casting. To create the casting mould, you need to apply shrinkage to your part because after casting, when the hot metal cools down, it will shrink by a few percent (depending on the material). Usually it is best to leave the application of shrinkage to the foundry making the part because they have the required special knowledge. They should also tell you if your part has problematic areas, e.g. very thick walls suddenly joining to very thin sections without a properly tapered section between them.<br />
<br />
{{languages | {{it|PartDesign_Bearingholder_Tutorial_I/it}} }}<br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_I&diff=40201PartDesign Bearingholder Tutorial I2013-07-16T18:51:23Z<p>Jrheinlaender: </p>
<hr />
<div>[[Image:HolderTop1-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the first part of the tutorial. It will use what might be called the 'single body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br />
You can find my version of the part created by this tutorial [[http://ubuntuone.com/39PTZ3Y3LUnmZzpZQPcJT4 here]].<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop1-2.jpg|Bearing holder with the two most important skeleton planes|thumb|right|text-top|400px]]<br />
<br />
The idea of skeleton geometry is to capture the basic design dimensions in a single datum feature (e.g. a plane or an axis). When the design dimension changes, all that needs to be done is to change the skeleton feature. If the model is well built, then all its feature will recompute to reflect the design change. This reduces the danger that in a complex model, where the basic design dimensions are used in multiple places, you forget to change it somewhere.<br />
<br />
The alternative to skeleton geometry is to have a table of the basic design dimensions that assign a symbolic name to each dimension, and then use the symbolic name wherever the dimensions is required to build the model. FreeCAD does not allow this approach yet.<br />
<br />
[[Image:HolderTop1-3.jpg|Base planes and all datum planes|thumb|right|text-top|400px]]<br />
<br />
For the case of the bearing holder, the two most important design dimensions are the distance between the bolts (which limits the size of the bearing that can be used) and the height of the bolt heads. The dimensions chosen are<br />
* Distance between bolts: Radius of bearing (45) + wall thickness (5) plus radius of hole for bolt (7) = 57mm, so the vertical plane will be 57mm offset from the YZ-plane. To create this datum plane, select the YZ-plane and then choose to create a new datum plane. Enter the offset in the dialog that opens up<br />
* Height of bolt heads: This was chosen as an offset of 28mm from the XZ-plane<br />
<br />
For convenience, two further datum planes can be created to reflect the amount of material that must be cut away from the sides of the bearing holder. They are offset +22 and -22 from the XY-plane.<br />
<br />
It is advisable to give clear names to the skeleton geometry. Most of the time, you will want to turn off visibility for datum planes because they clutter up the screen, and if the planes have self-explanatory names you can just pick them by name instead of from the screen.<br />
<br clear=all><br />
<br />
== The solid geometry ==<br />
<br />
[[Image:HolderTop1-4.jpg|thumb|400px|right|text-top|Sketch of the first pad]]<br />
Now its time to start creating some real geometry. The sketch for the first pad is shown on the right. It is placed on the XY-plane. There are just three dimensions: The inner radius (22.5mm), the machining allowance (3mm) at the base as an offset to the XZ-plane and the distance from the datum plane representing the bolt axis (7mm). This means that if you later move the datum plane, the pad will automatically adjust its outer radius. Remember that before you can use the datum plane for dimensioning, you need to introduce it as external geometry to the sketcher.<br />
<br />
You are probably wondering why there is a small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), just pad it symmetrically to the sketch plane with a length of 62mm: 34mm for the bearing, 2x 9mm for the sealing rings, 2x 5mm for the wall thickness.<br />
<br clear=all><br />
<br />
[[Image:HolderTop1-5.jpg|thumb|400px|right|text-top|Sketch of the cut-away at the side of the pad]]<br />
Next we want to cut away some material where the sealing rings are, because their outer diameter is much less than the bearing's. The easiest way to create the sketches is to select the sketch of the pad and then choose "Duplicate selection" from the edit menu. You can then remap the sketch to the side of the pad, and modify it as shown in the picture.<br />
<br />
The only two important dimensions in the sketch are 3mm of machining allowance at the bottom, and a inner diameter of 78mm: 68mm for the outer diameter of the sealing ring + 2x 5mm wall thickness. Since the sealing ring on the other side will only have a diameter of 55mm, the cut-out can be 65mm here.<br />
<br />
After you have created the sketch, pocket it up to the datum plane marking the bearing side plus 5mm wall thickness. If you ever want to modify the holder to be able to hold wider bearings, all you have to do is to change the dimension of these datum planes, and the cut-out depth will follow along.<br />
<br clear=all><br />
<br />
[[Image:HolderTop1-6.jpg|thumb|400px|right|text-top|Sketch of the cut-away inside the pad]]<br />
To reduce the amount of machining required, we also want to cut away some material inside the holder. Again, duplicating the sketch of the first pad is convenient. It doesn't even have to be remapped. Again, the only important dimensions are the machining allowance (3mm) and the outer diameters: 84mm for the place where the bearing will be (90mm - 2x machining allowance), 49mm for the smaller sealing ring (55mm - 2x 3mm) and 62mm for the larger sealing ring.<br />
<br />
After creating the sketches, pocket them: Symetrically 28mm for the bearing cut-out (34mm - 2x machining allowance) and one-sided 23mm for the cut-outs for the sealing rings: 34mm / 2 for half the bearing width + 9mm for the sealing rings - 3mm machining allowance. <br />
<br clear=all><br />
<br />
[[Image:HolderTop1-7.jpg|thumb|400px|right|text-top|Main geometry of the holder top]]<br />
Your part should now look like the picture on the right. Note how the different cut-aways combine to create an almost uniform wall thickness, which will make the casting easier and less liable to have pores.<br />
<br clear=all><br />
<br />
[[Image:HolderTop1-8.jpg|thumb|400px|right|text-top|Sketch with draft where the bolts will be]]<br />
Now all that remains is to create some material for the bolts to go through. You might be tempted to sketch these as a circle and then pad them, but this will head you for trouble when you try to put the draft onto them later (I assume that is a weakness of OpenCascade). So to circumvent the problems, it is better to create a sketch with the draft angle included and then rotate it through 360 degrees.<br />
<br />
Here again the skeleton planes come in useful. You will need the bolt axis plane and the bolt head plane as external geometry. Then, create a straight line for the rotation axis and make sure it is constrained to the bolt axis plane reference. Toggle it to be construction geometry. Then, sketch the rest of the contour. The important dimensions are the machining allowance at the top and bottom and the radius of 12mm: 7mm for the hole radius + 5mm wall thickness.<br />
<br clear=all><br />
<br />
[[Image:HolderTop1-9.jpg|thumb|400px|right|text-top|Finished geometry of the holder top (without draft and fillets)]]<br />
Create a revolution feature from the sketch and then mirror it on the YZ-plane. This is all the solid geometry we need to model. The rest is draft and fillets.<br />
<br clear=all><br />
<br />
== Applying draft to the side faces ==<br />
<br />
[[Image:HolderTop1-10.jpg|thumb|400px|right|text-top|The neutral plane for creating drafts]]<br />
The next step is to apply drafts on all faces. Its important to consider the location of the neutral plane, that is, the plane which the face is "rotated" around. If we choose as neutral plane the bottom of the holder, then we will have a problem with the wall thickness in the top part of the holder. Therefore, we create a datum plane at an offset of 40mm from the XZ plane as a compromise between the top of the holder becoming to thin and the bottom becoming to wide.<br />
<br clear=all><br />
<br />
[[Image:HolderTop1-11.jpg|thumb|400px|right|text-top|Applying draft to the side faces of the holder]]<br />
To put draft on a face, select this face and create the draft feature. You can then select more faces to apply the draft on. If you have a large part, it is advisable to draft only one face at a time. This means that if you change the geometry and a draft fails, only this one feature will fail, whereas if you put all faces in one draft feature, then the whole feature might fail because of one face failing. For a small part like the bearing holder, its sufficient to create two draft features: One for the four outside faces, and one for the inside faces.<br />
<br />
The dialog will force you to select a neutral plane before completing. You can leave the pull direction empty, in this case it will be normal to the neutral plane. Don't forget to set the draft angle to 2 degrees.<br />
<br clear=all><br />
<br />
== Filleting the holder ==<br />
<br />
[[Image:HolderTop1-13.jpg|thumb|400px|right|text-top|Fillet where the bolts will go]]<br />
We can now fillet the part. The picture shows the first set of fillets. Start with the small circular fillets and make them 4mm radius. Even though 3mm would be enough as per specification of the part, a radius of 4mm means that after machining 1mm of the fillet is left, reducing the sharp edge produced by the machining. The large fillets are 6mm radius to help spread the force from the bolts into the rest of the part. It would be nice to make this radius even larger, but unfortunately OpenCascade can't handle overlapping fillets yet.<br />
<br />
As with drafts, in a complex part you should fillet only one edge at a time to avoid unnecessary failures if the base geometry changes.<br />
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<br />
[[Image:HolderTop1-12.jpg|thumb|400px|right|text-top|Filleting the outside of the holder]]<br />
The rest of the fillets are simply 3mm radius. Looking at the picture on the right, the two highlighted fillets could actually be filleted with 5mm to achieve a more uniform wall thickness for the casting. After machining, the minimum wall thickness of 5mm would still be maintained. But again the fact that OpenCascade can't handle overlapping fillets prevents us from doing this for the inner of the two highlighted fillets.<br />
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<br />
[[Image:HolderTop1-14.jpg|thumb|400px|right|text-top|Filleting the inside of the holder - problematic edge]]<br />
Filleting the inside of the part presents us with a difficulty that cannot be solved with the current tools in the PartDesign workbench. The highlighted edge cannot be filleted at all, again because the rounds would overlap. This could be worked around by creating a sweep instead of a fillet, except that sweeps are not implemented in PartDesign yet. For the time being, we are forced to leave the edge as it is.<br />
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<br />
[[Image:HolderTop1-15.jpg|thumb|400px|right|text-top|The filleted part (except for the impossible edge)]]<br />
The picture on the right shows the finished part in the state it will be before machining (except for the one edge that is impossible to fillet). You will notice that one edge that runs around the whole part has been left unfilleted on purpose. This is the edge where the bottom and the top of the mould meet. Here, no fillet is possible (and none is required anyway).<br />
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<br />
== Machining ==<br />
<br />
[[Image:HolderTop1-16.jpg|thumb|400px|right|text-top|Machining the top and bottom of the holder]]<br />
[[Image:HolderTop1-17.jpg|thumb|400px|right|text-top|Machining the inside of the bearing holder]]<br />
Now we can cut away the material that will be machined off the raw cast part. This is very easy with the skeleton geometry defined. The idea is to create all machining features (Pockets and Grooves) using datum features only. This means they will be totally independent of the solid geometry of the bearing holder, which gives us some big advantages:<br />
* No matter how you change the solid geometry, the features for the machining can never fail.<br />
* You can create the machining geometry before finalizing the solid, which gives you useful visual feedback.<br />
* If you move the skeleton datum planes, then both the solid geometry and the machining will adapt automatically.<br />
* If you make a mistake in your solid geometry, the machining will still be in the correct position, and very likely the mistake will become glaringly obvious (e.g. a wall thickness becoming 2mm instead of 5mm). Whereas if you reference the machining to the solid geometry, it will adapt to the error in the solid and e.g. maintain the 5mm wall thickness, just in the same wrong location as the solid is.<br />
<br />
Before starting on the machining geometry, I like to place a datum point in the tree and name it something like "Machining_starts_here". This is useful if you want to switch between the raw and the machined state of the part because you can see at a glance where to move the insert point to get the raw state.<br />
<br />
To machine the bottom of the holder, just sketch a large rectangle on the XZ plane and pocket it. For the top, sketch a circle on the datum plane defining the bolt head location, and then mirror the pocket on the YZ plane. In the same way, create a pocket for the hole which the bolt will go through and mirror it. To machine the inside of the holder, create a sketch on the YZ plane and groove it.<br />
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<br />
[[Image:HolderTop1-1.jpg|thumb|400px|right|text-top|Finished part]]<br />
Once you have done the machining, you can have a nice visual effect by colouring all the machined faces so that you can see at one glance which parts are raw casting and which are machined after casting.<br />
<br />
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<br />
== Final notes ==<br />
<br />
We have modelled the bearing holder top with the dimensions it will have after casting. To create the casting mould, you need to apply shrinkage to your part because after casting, when the hot metal cools down, it will shrink by a few percent (depending on the material). Usually it is best to leave the application of shrinkage to the foundry making the part because they have the required special knowledge. They should also tell you if your part has problematic areas, e.g. very thick walls suddenly joining to very thin sections without a properly tapered section between them.<br />
<br />
{{languages | {{it|PartDesign_Bearingholder_Tutorial_I/it}} }}<br />
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[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=40191PartDesign Bearingholder Tutorial II2013-07-16T18:50:43Z<p>Jrheinlaender: </p>
<hr />
<div>[[Image:HolderTop2-19.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br />
You can find my version of the part created in this tutorial [[http://ubuntuone.com/39PTZ3Y3LUnmZzpZQPcJT4 here]]<br />
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<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. The head of such a bolt will require at least 20mm diameter free space. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
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<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
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<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
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<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
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<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
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<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
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<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
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<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
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<br />
== Adding the bodies for the bolts ==<br />
<br />
[[Image:HolderTop2-13.jpg|The sketch for the body for the bolts|thumb|right|400px]]<br />
The bolts need two cylindrical bodies on both sides of the main Body. It is best to include the 2 degree draft angle in the sketch. I tried revolving a cylinder and later applying a draft, but weird things happened after mirroring it and I couldn't put fillets on it because the surface was warped somehow.<br />
<br />
The sketch is dimensioned so that the rotation axis is 12mm distance to the outer diameter of the skeleton Body, 7mm for the radius of the hole plus 5mm for the wall thickness. For the sake of having a fully parametric part, it is a good idea to add a plane to the Skeleton about 25mm above the XY-plane to mark the top of the cylinders. Since this will be machined, the sketch is dimensioned 3mm above it.<br />
<br />
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<br />
[[Image:HolderTop2-14.jpg|The body for the bolts|thumb|right|400px]]<br />
Create a revolution from the sketch and apply a fillet of 4mm to the top. This means that after machining away 3mm, a slight radius will remain which helps to avoid a sharp edge where someone could cut their hand when tightening the bolt.<br />
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<br />
[[Image:HolderTop2-16.jpg|The main body with the two bodies for the bolts|thumb|right|400px]]<br />
Create a boolean feature to fuse the main Body and the bolt body. Then create a new body for the other side. Duplicate the sketch of the revolution, move it to this body and create the second body for the bolts (mirroring a Body is not supported yet so you need to redo most of it). Then fuse this second body into the main Body as well. Finally, apply a large fillet on the edge created by the boolean fuse operation. The largest I could get was 4mm.<br />
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<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
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<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
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<br />
[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
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<br />
[[Image:HolderTop2-15.jpg|The completed raw part of the holder (without machining)|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". Put a 3mm fillet on the two edges resulting from the cut-out operation (again some edges remain that are "unfilletable"). The result should look like the picture on the right.<br />
<br />
The raw part is now completed. This is what the holder will look like before machining. Note that since the mold will have a top and bottom half, the edge between these two cannot be filleted. Also, if you give away this model to a foundry make sure to point out that it has the dimensions after casting. The foundry will then have to apply a certain percentage of shrinkage to the model (making the digital model used to manufacture the mold larger so that when the metal cools down and shrinks after casting it will have the right size).<br />
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<br />
== Machining ==<br />
<br />
[[Image:HolderTop2-17.jpg|Sketch to "drill" the hole for the bolts|thumb|right|400px]]<br />
To take away the material for machining the inside of the holder, very conveniently we can use the Skeleton Body itself. If you don't want that because then the skeleton gets hidden somewhere deep in the tree, you can also duplicate the sketch of the skeleton Revolution feature and re-create the revolution in another body. This is not completely parametric, though, because the duplicated sketch is independent of the original, so you will have to work on both if you change a dimension. Dependent duplicated features might be supported in the future sometime.<br />
<br />
For the rest of the machining, create a new Body. The bottom of the holder will be machined by a Pad sketched on the XY-plane extending downwards. Next, sketch a revolution to make a hole for the bolts. You will need to sketch on the XZ-plane and revolve it so that you can choose the outer diameter of the skeleton Body as an external reference. The top part of the sketch will serve to machine a flat place for the head of the bolt. It is dimensioned to leave at least 5mm wall thickness in the holder. If this does not give enough space for the bolt head then you can move the datum plane upwards. Of course, you could put this logic into the Skeleton, which is left as an exercise to the reader!<br />
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<br />
[[Image:HolderTop2-18.jpg|The machining Body|thumb|right|400px]]<br />
You can mirror the revolution on the YZ-axis. The picture on the right shows the "machining" Body. Of course, most of the dimensions of the Pads and Revolutions are not important as long as there is plenty of overlap.<br />
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<br />
[[Image:HolderTop2-19.jpg|The finished Holder with machining|thumb|right|400px]]<br />
Finally, create a boolean operation to cut the machining Body out of the main Body. If you want a nice visual effect, you can colour the machined surfaces differently from the rest of the part. This is also a useful optical feedback showing you whether you forgot to machine somewhere.<br />
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<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=40181PartDesign Bearingholder Tutorial II2013-07-16T18:41:18Z<p>Jrheinlaender: </p>
<hr />
<div>[[Image:HolderTop2-19.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. The head of such a bolt will require at least 20mm diameter free space. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
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<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Adding the bodies for the bolts ==<br />
<br />
[[Image:HolderTop2-13.jpg|The sketch for the body for the bolts|thumb|right|400px]]<br />
The bolts need two cylindrical bodies on both sides of the main Body. It is best to include the 2 degree draft angle in the sketch. I tried revolving a cylinder and later applying a draft, but weird things happened after mirroring it and I couldn't put fillets on it because the surface was warped somehow.<br />
<br />
The sketch is dimensioned so that the rotation axis is 12mm distance to the outer diameter of the skeleton Body, 7mm for the radius of the hole plus 5mm for the wall thickness. For the sake of having a fully parametric part, it is a good idea to add a plane to the Skeleton about 25mm above the XY-plane to mark the top of the cylinders. Since this will be machined, the sketch is dimensioned 3mm above it.<br />
<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-14.jpg|The body for the bolts|thumb|right|400px]]<br />
Create a revolution from the sketch and apply a fillet of 4mm to the top. This means that after machining away 3mm, a slight radius will remain which helps to avoid a sharp edge where someone could cut their hand when tightening the bolt.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-16.jpg|The main body with the two bodies for the bolts|thumb|right|400px]]<br />
Create a boolean feature to fuse the main Body and the bolt body. Then create a new body for the other side. Duplicate the sketch of the revolution, move it to this body and create the second body for the bolts (mirroring a Body is not supported yet so you need to redo most of it). Then fuse this second body into the main Body as well. Finally, apply a large fillet on the edge created by the boolean fuse operation. The largest I could get was 4mm.<br />
<br clear=all><br />
<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-15.jpg|The completed raw part of the holder (without machining)|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". Put a 3mm fillet on the two edges resulting from the cut-out operation (again some edges remain that are "unfilletable"). The result should look like the picture on the right.<br />
<br />
The raw part is now completed. This is what the holder will look like before machining. Note that since the mold will have a top and bottom half, the edge between these two cannot be filleted. Also, if you give away this model to a foundry make sure to point out that it has the dimensions after casting. The foundry will then have to apply a certain percentage of shrinkage to the model (making the digital model used to manufacture the mold larger so that when the metal cools down and shrinks after casting it will have the right size).<br />
<br clear=all><br />
<br />
== Machining ==<br />
<br />
[[Image:HolderTop2-17.jpg|Sketch to "drill" the hole for the bolts|thumb|right|400px]]<br />
To take away the material for machining the inside of the holder, very conveniently we can use the Skeleton Body itself. If you don't want that because then the skeleton gets hidden somewhere deep in the tree, you can also duplicate the sketch of the skeleton Revolution feature and re-create the revolution in another body. This is not completely parametric, though, because the duplicated sketch is independent of the original, so you will have to work on both if you change a dimension. Dependent duplicated features might be supported in the future sometime.<br />
<br />
For the rest of the machining, create a new Body. The bottom of the holder will be machined by a Pad sketched on the XY-plane extending downwards. Next, sketch a revolution to make a hole for the bolts. You will need to sketch on the XZ-plane and revolve it so that you can choose the outer diameter of the skeleton Body as an external reference. The top part of the sketch will serve to machine a flat place for the head of the bolt. It is dimensioned to leave at least 5mm wall thickness in the holder. If this does not give enough space for the bolt head then you can move the datum plane upwards. Of course, you could put this logic into the Skeleton, which is left as an exercise to the reader!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-18.jpg|The machining Body|thumb|right|400px]]<br />
You can mirror the revolution on the YZ-axis. The picture on the right shows the "machining" Body. Of course, most of the dimensions of the Pads and Revolutions are not important as long as there is plenty of overlap.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-19.jpg|The finished Holder with machining|thumb|right|400px]]<br />
Finally, create a boolean operation to cut the machining Body out of the main Body. If you want a nice visual effect, you can colour the machined surfaces differently from the rest of the part. This is also a useful optical feedback showing you whether you forgot to machine somewhere.<br />
<br clear=all><br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=File:HolderTop2-19.jpg&diff=40171File:HolderTop2-19.jpg2013-07-16T18:40:57Z<p>Jrheinlaender: </p>
<hr />
<div></div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=File:HolderTop2-18.jpg&diff=40161File:HolderTop2-18.jpg2013-07-16T18:26:56Z<p>Jrheinlaender: </p>
<hr />
<div></div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=File:HolderTop2-17.jpg&diff=40151File:HolderTop2-17.jpg2013-07-16T18:26:36Z<p>Jrheinlaender: </p>
<hr />
<div></div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=40141PartDesign Bearingholder Tutorial II2013-07-16T18:05:40Z<p>Jrheinlaender: /* Adding the bodies for the bolts */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. The head of such a bolt will require at least 20mm diameter free space. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Adding the bodies for the bolts ==<br />
<br />
[[Image:HolderTop2-13.jpg|The sketch for the body for the bolts|thumb|right|400px]]<br />
The bolts need two cylindrical bodies on both sides of the main Body. It is best to include the 2 degree draft angle in the sketch. I tried revolving a cylinder and later applying a draft, but weird things happened after mirroring it and I couldn't put fillets on it because the surface was warped somehow.<br />
<br />
The sketch is dimensioned so that the rotation axis is 12mm distance to the outer diameter of the skeleton Body, 7mm for the radius of the hole plus 5mm for the wall thickness. For the sake of having a fully parametric part, it is a good idea to add a plane to the Skeleton about 25mm above the XY-plane to mark the top of the cylinders. Since this will be machined, the sketch is dimensioned 3mm above it.<br />
<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-14.jpg|The body for the bolts|thumb|right|400px]]<br />
Create a revolution from the sketch and apply a fillet of 4mm to the top. This means that after machining away 3mm, a slight radius will remain which helps to avoid a sharp edge where someone could cut their hand when tightening the bolt.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-16.jpg|The main body with the two bodies for the bolts|thumb|right|400px]]<br />
Create a boolean feature to fuse the main Body and the bolt body. Then create a new body for the other side. Duplicate the sketch of the revolution, move it to this body and create the second body for the bolts (mirroring a Body is not supported yet so you need to redo most of it). Then fuse this second body into the main Body as well. Finally, apply a large fillet on the edge created by the boolean fuse operation. The largest I could get was 4mm.<br />
<br clear=all><br />
<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-15.jpg|The completed raw part of the holder (without machining)|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". Put a 3mm fillet on the two edges resulting from the cut-out operation (again some edges remain that are "unfilletable"). The result should look like the picture on the right.<br />
<br />
The raw part is now completed. This is what the holder will look like before machining. Note that since the mold will have a top and bottom half, the edge between these two cannot be filleted. Also, if you give away this model to a foundry make sure to point out that it has the dimensions after casting. The foundry will then have to apply a certain percentage of shrinkage to the model (making the digital model used to manufacture the mold larger so that when the metal cools down and shrinks after casting it will have the right size).<br />
<br clear=all><br />
<br />
== Machining ==<br />
<br />
[[Image:HolderTop2-17.jpg|Sketch to "drill" the hole for the bolts|thumb|right|400px]]<br />
To take away the material for machining the inside of the holder, very conveniently we can use the Skeleton Body itself. If you don't want that because then the skeleton gets hidden somewhere deep in the tree, you can also duplicate the sketch of the skeleton Revolution feature and re-create the revolution in another body. This is not completely parametric, though, because the duplicated sketch is independent of the original, so you will have to work on both if you change a dimension. Dependent duplicated features might be supported in the future sometime.<br />
<br />
For the rest of the machining, create a new Body. The bottom of the holder will be machined by a Pad sketched on the XY-plane extending downwards. Next, sketch a revolution to make a hole for the bolts. You will need to sketch on the XZ-plane and revolve it so that you can choose the outer diameter of the skeleton Body as an external reference. The top part of the sketch will serve to machine a flat place for the head of the bolt. It is dimensioned to leave at least 5mm wall thickness in the holder. If this does not give enough space for the bolt head then you can move the datum plane upwards. Of course, you could put this logic into the Skeleton, which is left as an exercise to the reader!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-18.jpg|The machining Body|thumb|right|400px]]<br />
You can mirror the revolution on the YZ-axis. The picture on the right shows the "machining" Body. Of course, most of the dimensions of the Pads and Revolutions are not important as long as there is plenty of overlap.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-19.jpg|The finished Holder with machining|thumb|right|400px]]<br />
Finally, create a boolean operation to cut the machining Body out of the main Body. If you want a nice visual effect, you can colour the machined surfaces differently from the rest of the part. This is also a useful optical feedback showing you whether you forgot to machine somewhere.<br />
<br clear=all><br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=40131PartDesign Bearingholder Tutorial II2013-07-16T17:56:20Z<p>Jrheinlaender: /* Adding the bodies for the bolts */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. The head of such a bolt will require at least 20mm diameter free space. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Adding the bodies for the bolts ==<br />
<br />
[[Image:HolderTop2-13.jpg|The sketch for the body for the bolts|thumb|right|400px]]<br />
The bolts need two cylindrical bodies on both sides of the main Body. It is best to include the 2 degree draft angle in the sketch. I tried revolving a cylinder and later applying a draft, but weird things happened after mirroring it and I couldn't put fillets on it because the surface was warped somehow.<br />
<br />
The sketch is dimensioned so that the rotation axis is 13mm distance to the outer diameter of the skeleton Body, so that the head of the bolt can have at least 26mm diameter to rest on. For the sake of having a fully parametric part, it is a good idea to add a plane to the Skeleton about 25mm above the XY-plane to mark the top of the cylinders. Since this will be machined, the sketch is dimensioned 3mm above it.<br />
<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-14.jpg|The body for the bolts|thumb|right|400px]]<br />
Create a revolution from the sketch and apply a fillet of 4mm to the top. This means that after machining away 3mm, a slight radius will remain which helps to avoid a sharp edge where someone could cut their hand when tightening the bolt.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-16.jpg|The main body with the two bodies for the bolts|thumb|right|400px]]<br />
Create a boolean feature to fuse the main Body and the bolt body. Then create a new body for the other side. Duplicate the sketch of the revolution, move it to this body and create the second body for the bolts (mirroring a Body is not supported yet so you need to redo most of it). Then fuse this second body into the main Body as well. Finally, apply a large fillet on the edge created by the boolean fuse operation. The largest I could get was 4mm.<br />
<br clear=all><br />
<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-15.jpg|The completed raw part of the holder (without machining)|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". Put a 3mm fillet on the two edges resulting from the cut-out operation (again some edges remain that are "unfilletable"). The result should look like the picture on the right.<br />
<br />
The raw part is now completed. This is what the holder will look like before machining. Note that since the mold will have a top and bottom half, the edge between these two cannot be filleted. Also, if you give away this model to a foundry make sure to point out that it has the dimensions after casting. The foundry will then have to apply a certain percentage of shrinkage to the model (making the digital model used to manufacture the mold larger so that when the metal cools down and shrinks after casting it will have the right size).<br />
<br clear=all><br />
<br />
== Machining ==<br />
<br />
[[Image:HolderTop2-17.jpg|Sketch to "drill" the hole for the bolts|thumb|right|400px]]<br />
To take away the material for machining the inside of the holder, very conveniently we can use the Skeleton Body itself. If you don't want that because then the skeleton gets hidden somewhere deep in the tree, you can also duplicate the sketch of the skeleton Revolution feature and re-create the revolution in another body. This is not completely parametric, though, because the duplicated sketch is independent of the original, so you will have to work on both if you change a dimension. Dependent duplicated features might be supported in the future sometime.<br />
<br />
For the rest of the machining, create a new Body. The bottom of the holder will be machined by a Pad sketched on the XY-plane extending downwards. Next, sketch a revolution to make a hole for the bolts. You will need to sketch on the XZ-plane and revolve it so that you can choose the outer diameter of the skeleton Body as an external reference. The top part of the sketch will serve to machine a flat place for the head of the bolt. It is dimensioned to leave at least 5mm wall thickness in the holder. If this does not give enough space for the bolt head then you can move the datum plane upwards. Of course, you could put this logic into the Skeleton, which is left as an exercise to the reader!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-18.jpg|The machining Body|thumb|right|400px]]<br />
You can mirror the revolution on the YZ-axis. The picture on the right shows the "machining" Body. Of course, most of the dimensions of the Pads and Revolutions are not important as long as there is plenty of overlap.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-19.jpg|The finished Holder with machining|thumb|right|400px]]<br />
Finally, create a boolean operation to cut the machining Body out of the main Body. If you want a nice visual effect, you can colour the machined surfaces differently from the rest of the part. This is also a useful optical feedback showing you whether you forgot to machine somewhere.<br />
<br clear=all><br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=40121PartDesign Bearingholder Tutorial II2013-07-16T17:51:46Z<p>Jrheinlaender: /* Adding the bodies for the bolts */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. The head of such a bolt will require at least 20mm diameter free space. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Adding the bodies for the bolts ==<br />
<br />
[[Image:HolderTop2-13.jpg|The sketch for the body for the bolts|thumb|right|400px]]<br />
The bolts need two cylindrical bodies on both sides of the main Body. It is best to include the 2 degree draft angle in the sketch. I tried revolving a cylinder and later applying a draft, but weird things happened after mirroring it and I couldn't put fillets on it because the surface was warped somehow.<br />
<br />
The sketch is dimensioned so that the rotation axis is 13mm distance to the outer diameter of the skeleton Body, so that the head of the bolt can have at least 26mm diameter to rest on. For the sake of having a fully parametric part, it is a good idea to add a plane to the Skeleton about 25mm above the XY-plane to mark the top of the cylinders. Since this will be machined, the sketch is dimensioned 3mm above it.<br />
<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-14.jpg|The body for the bolts|thumb|right|400px]]<br />
Create a revolution from the sketch and apply a fillet of 4mm to the top. This means that after machining away 3mm, a slight radius will remain which helps to avoid a sharp edge where someone could cut their hand when tightening the bolt.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-16.jpg|The main body with the two bodies for the bolts|thumb|right|400px]]<br />
Create a boolean feature to fuse the main Body and the bolt body. Then create a new body for the other side. Duplicate the sketch of the revolution, move it to this body and create the second body for the bolts (mirroring a Body is not supported yet so you need to redo most of it). Then fuse this second body into the main Body as well. Finally, apply a large fillet on the edge created by the boolean fuse operation. The largest I could get was 5mm and if you put in too much FreeCAD will crash (which is a known bug) so its better to start small and work your way up.<br />
<br clear=all><br />
<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-15.jpg|The completed raw part of the holder (without machining)|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". Put a 3mm fillet on the two edges resulting from the cut-out operation (again some edges remain that are "unfilletable"). The result should look like the picture on the right.<br />
<br />
The raw part is now completed. This is what the holder will look like before machining. Note that since the mold will have a top and bottom half, the edge between these two cannot be filleted. Also, if you give away this model to a foundry make sure to point out that it has the dimensions after casting. The foundry will then have to apply a certain percentage of shrinkage to the model (making the digital model used to manufacture the mold larger so that when the metal cools down and shrinks after casting it will have the right size).<br />
<br clear=all><br />
<br />
== Machining ==<br />
<br />
[[Image:HolderTop2-17.jpg|Sketch to "drill" the hole for the bolts|thumb|right|400px]]<br />
To take away the material for machining the inside of the holder, very conveniently we can use the Skeleton Body itself. If you don't want that because then the skeleton gets hidden somewhere deep in the tree, you can also duplicate the sketch of the skeleton Revolution feature and re-create the revolution in another body. This is not completely parametric, though, because the duplicated sketch is independent of the original, so you will have to work on both if you change a dimension. Dependent duplicated features might be supported in the future sometime.<br />
<br />
For the rest of the machining, create a new Body. The bottom of the holder will be machined by a Pad sketched on the XY-plane extending downwards. Next, sketch a revolution to make a hole for the bolts. You will need to sketch on the XZ-plane and revolve it so that you can choose the outer diameter of the skeleton Body as an external reference. The top part of the sketch will serve to machine a flat place for the head of the bolt. It is dimensioned to leave at least 5mm wall thickness in the holder. If this does not give enough space for the bolt head then you can move the datum plane upwards. Of course, you could put this logic into the Skeleton, which is left as an exercise to the reader!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-18.jpg|The machining Body|thumb|right|400px]]<br />
You can mirror the revolution on the YZ-axis. The picture on the right shows the "machining" Body. Of course, most of the dimensions of the Pads and Revolutions are not important as long as there is plenty of overlap.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-19.jpg|The finished Holder with machining|thumb|right|400px]]<br />
Finally, create a boolean operation to cut the machining Body out of the main Body. If you want a nice visual effect, you can colour the machined surfaces differently from the rest of the part. This is also a useful optical feedback showing you whether you forgot to machine somewhere.<br />
<br clear=all><br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=File:HolderTop2-13.jpg&diff=40111File:HolderTop2-13.jpg2013-07-16T17:50:52Z<p>Jrheinlaender: Jrheinlaender uploaded a new version of &quot;File:HolderTop2-13.jpg&quot;</p>
<hr />
<div></div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=40101PartDesign Bearingholder Tutorial II2013-07-16T17:45:28Z<p>Jrheinlaender: /* Design data */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. The head of such a bolt will require at least 20mm diameter free space. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Adding the bodies for the bolts ==<br />
<br />
[[Image:HolderTop2-13.jpg|The sketch for the body for the bolts|thumb|right|400px]]<br />
The bolts need two cylindrical bodies on both sides of the main Body. Its best to include the 2 degree draft angle in the sketch. I tried revolving a cylinder and later applying a draft, but weird things happened after mirroring it and I couldn't put fillets on it because the surface was warped somehow.<br />
<br />
The sketch is dimensioned so that the rotation axis is 7mm distance to the outer diameter of the skeleton Body, because we want to drill a 14mm hole into it later. The wall thickness is another 5mm in addition to that. For the sake of having a fully parametric part, it is a good idea to add a plane to the Skeleton about 25mm above the XY-plane to mark the top of the cylinders. Since this will be machined, the sketch is dimensioned 3mm above it.<br />
<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-14.jpg|The body for the bolts|thumb|right|400px]]<br />
Create a revolution from the sketch and apply a fillet of 4mm to the top. This means that after machining away 3mm, a slight radius will remain which helps to avoid a sharp edge where someone could cut their hand when tightening the bolt.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-16.jpg|The main body with the two bodies for the bolts|thumb|right|400px]]<br />
Create a boolean feature to fuse the main Body and the bolt body. Then create a new body for the other side. Duplicate the sketch of the revolution, move it to this body and create the second body for the bolts (mirroring a Body is not supported yet so you need to redo most of it). Then fuse this second body into the main Body as well. Finally, apply a large fillet on the edge created by the boolean fuse operation. The largest I could get was 5mm and if you put in too much FreeCAD will crash (which is a known bug) so its better to start small and work your way up.<br />
<br clear=all><br />
<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-15.jpg|The completed raw part of the holder (without machining)|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". Put a 3mm fillet on the two edges resulting from the cut-out operation (again some edges remain that are "unfilletable"). The result should look like the picture on the right.<br />
<br />
The raw part is now completed. This is what the holder will look like before machining. Note that since the mold will have a top and bottom half, the edge between these two cannot be filleted. Also, if you give away this model to a foundry make sure to point out that it has the dimensions after casting. The foundry will then have to apply a certain percentage of shrinkage to the model (making the digital model used to manufacture the mold larger so that when the metal cools down and shrinks after casting it will have the right size).<br />
<br clear=all><br />
<br />
== Machining ==<br />
<br />
[[Image:HolderTop2-17.jpg|Sketch to "drill" the hole for the bolts|thumb|right|400px]]<br />
To take away the material for machining the inside of the holder, very conveniently we can use the Skeleton Body itself. If you don't want that because then the skeleton gets hidden somewhere deep in the tree, you can also duplicate the sketch of the skeleton Revolution feature and re-create the revolution in another body. This is not completely parametric, though, because the duplicated sketch is independent of the original, so you will have to work on both if you change a dimension. Dependent duplicated features might be supported in the future sometime.<br />
<br />
For the rest of the machining, create a new Body. The bottom of the holder will be machined by a Pad sketched on the XY-plane extending downwards. Next, sketch a revolution to make a hole for the bolts. You will need to sketch on the XZ-plane and revolve it so that you can choose the outer diameter of the skeleton Body as an external reference. The top part of the sketch will serve to machine a flat place for the head of the bolt. It is dimensioned to leave at least 5mm wall thickness in the holder. If this does not give enough space for the bolt head then you can move the datum plane upwards. Of course, you could put this logic into the Skeleton, which is left as an exercise to the reader!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-18.jpg|The machining Body|thumb|right|400px]]<br />
You can mirror the revolution on the YZ-axis. The picture on the right shows the "machining" Body. Of course, most of the dimensions of the Pads and Revolutions are not important as long as there is plenty of overlap.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-19.jpg|The finished Holder with machining|thumb|right|400px]]<br />
Finally, create a boolean operation to cut the machining Body out of the main Body. If you want a nice visual effect, you can colour the machined surfaces differently from the rest of the part. This is also a useful optical feedback showing you whether you forgot to machine somewhere.<br />
<br clear=all><br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=40091PartDesign Bearingholder Tutorial II2013-07-16T17:42:49Z<p>Jrheinlaender: /* Machining */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Adding the bodies for the bolts ==<br />
<br />
[[Image:HolderTop2-13.jpg|The sketch for the body for the bolts|thumb|right|400px]]<br />
The bolts need two cylindrical bodies on both sides of the main Body. Its best to include the 2 degree draft angle in the sketch. I tried revolving a cylinder and later applying a draft, but weird things happened after mirroring it and I couldn't put fillets on it because the surface was warped somehow.<br />
<br />
The sketch is dimensioned so that the rotation axis is 7mm distance to the outer diameter of the skeleton Body, because we want to drill a 14mm hole into it later. The wall thickness is another 5mm in addition to that. For the sake of having a fully parametric part, it is a good idea to add a plane to the Skeleton about 25mm above the XY-plane to mark the top of the cylinders. Since this will be machined, the sketch is dimensioned 3mm above it.<br />
<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-14.jpg|The body for the bolts|thumb|right|400px]]<br />
Create a revolution from the sketch and apply a fillet of 4mm to the top. This means that after machining away 3mm, a slight radius will remain which helps to avoid a sharp edge where someone could cut their hand when tightening the bolt.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-16.jpg|The main body with the two bodies for the bolts|thumb|right|400px]]<br />
Create a boolean feature to fuse the main Body and the bolt body. Then create a new body for the other side. Duplicate the sketch of the revolution, move it to this body and create the second body for the bolts (mirroring a Body is not supported yet so you need to redo most of it). Then fuse this second body into the main Body as well. Finally, apply a large fillet on the edge created by the boolean fuse operation. The largest I could get was 5mm and if you put in too much FreeCAD will crash (which is a known bug) so its better to start small and work your way up.<br />
<br clear=all><br />
<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-15.jpg|The completed raw part of the holder (without machining)|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". Put a 3mm fillet on the two edges resulting from the cut-out operation (again some edges remain that are "unfilletable"). The result should look like the picture on the right.<br />
<br />
The raw part is now completed. This is what the holder will look like before machining. Note that since the mold will have a top and bottom half, the edge between these two cannot be filleted. Also, if you give away this model to a foundry make sure to point out that it has the dimensions after casting. The foundry will then have to apply a certain percentage of shrinkage to the model (making the digital model used to manufacture the mold larger so that when the metal cools down and shrinks after casting it will have the right size).<br />
<br clear=all><br />
<br />
== Machining ==<br />
<br />
[[Image:HolderTop2-17.jpg|Sketch to "drill" the hole for the bolts|thumb|right|400px]]<br />
To take away the material for machining the inside of the holder, very conveniently we can use the Skeleton Body itself. If you don't want that because then the skeleton gets hidden somewhere deep in the tree, you can also duplicate the sketch of the skeleton Revolution feature and re-create the revolution in another body. This is not completely parametric, though, because the duplicated sketch is independent of the original, so you will have to work on both if you change a dimension. Dependent duplicated features might be supported in the future sometime.<br />
<br />
For the rest of the machining, create a new Body. The bottom of the holder will be machined by a Pad sketched on the XY-plane extending downwards. Next, sketch a revolution to make a hole for the bolts. You will need to sketch on the XZ-plane and revolve it so that you can choose the outer diameter of the skeleton Body as an external reference. The top part of the sketch will serve to machine a flat place for the head of the bolt. It is dimensioned to leave at least 5mm wall thickness in the holder. If this does not give enough space for the bolt head then you can move the datum plane upwards. Of course, you could put this logic into the Skeleton, which is left as an exercise to the reader!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-18.jpg|The machining Body|thumb|right|400px]]<br />
You can mirror the revolution on the YZ-axis. The picture on the right shows the "machining" Body. Of course, most of the dimensions of the Pads and Revolutions are not important as long as there is plenty of overlap.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-19.jpg|The finished Holder with machining|thumb|right|400px]]<br />
Finally, create a boolean operation to cut the machining Body out of the main Body. If you want a nice visual effect, you can colour the machined surfaces differently from the rest of the part. This is also a useful optical feedback showing you whether you forgot to machine somewhere.<br />
<br clear=all><br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=40041PartDesign Bearingholder Tutorial II2013-07-15T19:56:51Z<p>Jrheinlaender: /* Machining */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Adding the bodies for the bolts ==<br />
<br />
[[Image:HolderTop2-13.jpg|The sketch for the body for the bolts|thumb|right|400px]]<br />
The bolts need two cylindrical bodies on both sides of the main Body. Its best to include the 2 degree draft angle in the sketch. I tried revolving a cylinder and later applying a draft, but weird things happened after mirroring it and I couldn't put fillets on it because the surface was warped somehow.<br />
<br />
The sketch is dimensioned so that the rotation axis is 7mm distance to the outer diameter of the skeleton Body, because we want to drill a 14mm hole into it later. The wall thickness is another 5mm in addition to that. For the sake of having a fully parametric part, it is a good idea to add a plane to the Skeleton about 25mm above the XY-plane to mark the top of the cylinders. Since this will be machined, the sketch is dimensioned 3mm above it.<br />
<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-14.jpg|The body for the bolts|thumb|right|400px]]<br />
Create a revolution from the sketch and apply a fillet of 4mm to the top. This means that after machining away 3mm, a slight radius will remain which helps to avoid a sharp edge where someone could cut their hand when tightening the bolt.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-16.jpg|The main body with the two bodies for the bolts|thumb|right|400px]]<br />
Create a boolean feature to fuse the main Body and the bolt body. Then create a new body for the other side. Duplicate the sketch of the revolution, move it to this body and create the second body for the bolts (mirroring a Body is not supported yet so you need to redo most of it). Then fuse this second body into the main Body as well. Finally, apply a large fillet on the edge created by the boolean fuse operation. The largest I could get was 5mm and if you put in too much FreeCAD will crash (which is a known bug) so its better to start small and work your way up.<br />
<br clear=all><br />
<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-15.jpg|The completed raw part of the holder (without machining)|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". Put a 3mm fillet on the two edges resulting from the cut-out operation (again some edges remain that are "unfilletable"). The result should look like the picture on the right.<br />
<br />
The raw part is now completed. This is what the holder will look like before machining. Note that since the mold will have a top and bottom half, the edge between these two cannot be filleted. Also, if you give away this model to a foundry make sure to point out that it has the dimensions after casting. The foundry will then have to apply a certain percentage of shrinkage to the model (making the digital model used to manufacture the mold larger so that when the metal cools down and shrinks after casting it will have the right size).<br />
<br clear=all><br />
<br />
== Machining ==<br />
<br />
[[Image:HolderTop2-17.jpg|Sketch to "drill" the hole for the bolts|thumb|right|400px]]<br />
To take away the material for machining the inside of the holder, very conveniently we can use the Skeleton Body itself. If you don't want that because then the skeleton gets hidden somewhere deep in the tree, you can also duplicate the sketch of the skeleton Revolution feature and re-create the revolution in another body. This is not completely parametric, though, because the duplicated sketch is independent of the original, so you will have to work on both if you change a dimension. Dependent duplicated features might be supported in the future sometime.<br />
<br />
For the rest of the machining, create a new Body. The bottom of the holder will be machined by a Pad sketched on the XY-plane extending downwards. Next, sketch a cylinder to make a hole for the bolts. You will need to sketch a rectangle on the XZ-plane and revolve it so that you can choose the outer diameter of the skeleton Body as an external reference.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-18.jpg|The machining Body|thumb|right|400px]]<br />
You can mirror the resulting cylinder on the YZ-axis. Lastly, create another Pad to machine a flat place for the bolt heads, using the datum plane you created in the Skeleton Body earlier as a reference. The picture on the right shows the "machining" Body. Of course, the actual dimensions of the Pads are not important as long as there is plenty of overlap.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-19.jpg|The finished Holder with machining|thumb|right|400px]]<br />
Finally, create a boolean operation to cut the machining Body out of the main Body. If you want a nice visual effect, you can colour the machined surfaces differently from the rest of the part. This is also a useful optical feedback showing you whether you forgot to machine somewhere.<br />
<br clear=all><br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=40031PartDesign Bearingholder Tutorial II2013-07-15T19:32:58Z<p>Jrheinlaender: /* Hollowing out the main body */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Adding the bodies for the bolts ==<br />
<br />
[[Image:HolderTop2-13.jpg|The sketch for the body for the bolts|thumb|right|400px]]<br />
The bolts need two cylindrical bodies on both sides of the main Body. Its best to include the 2 degree draft angle in the sketch. I tried revolving a cylinder and later applying a draft, but weird things happened after mirroring it and I couldn't put fillets on it because the surface was warped somehow.<br />
<br />
The sketch is dimensioned so that the rotation axis is 7mm distance to the outer diameter of the skeleton Body, because we want to drill a 14mm hole into it later. The wall thickness is another 5mm in addition to that. For the sake of having a fully parametric part, it is a good idea to add a plane to the Skeleton about 25mm above the XY-plane to mark the top of the cylinders. Since this will be machined, the sketch is dimensioned 3mm above it.<br />
<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-14.jpg|The body for the bolts|thumb|right|400px]]<br />
Create a revolution from the sketch and apply a fillet of 4mm to the top. This means that after machining away 3mm, a slight radius will remain which helps to avoid a sharp edge where someone could cut their hand when tightening the bolt.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-16.jpg|The main body with the two bodies for the bolts|thumb|right|400px]]<br />
Create a boolean feature to fuse the main Body and the bolt body. Then create a new body for the other side. Duplicate the sketch of the revolution, move it to this body and create the second body for the bolts (mirroring a Body is not supported yet so you need to redo most of it). Then fuse this second body into the main Body as well. Finally, apply a large fillet on the edge created by the boolean fuse operation. The largest I could get was 5mm and if you put in too much FreeCAD will crash (which is a known bug) so its better to start small and work your way up.<br />
<br clear=all><br />
<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-15.jpg|The completed raw part of the holder (without machining)|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". Put a 3mm fillet on the two edges resulting from the cut-out operation (again some edges remain that are "unfilletable"). The result should look like the picture on the right.<br />
<br />
The raw part is now completed. This is what the holder will look like before machining. Note that since the mold will have a top and bottom half, the edge between these two cannot be filleted. Also, if you give away this model to a foundry make sure to point out that it has the dimensions after casting. The foundry will then have to apply a certain percentage of shrinkage to the model (making the digital model used to manufacture the mold larger so that when the metal cools down and shrinks after casting it will have the right size).<br />
<br clear=all><br />
<br />
== Machining ==<br />
<br />
[[Image:HolderTop2-17.jpg|xyz|thumb|right|300px]]<br />
<br />
<br clear=all><br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=40021PartDesign Bearingholder Tutorial II2013-07-15T19:31:55Z<p>Jrheinlaender: /* Hollowing out the main body */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Adding the bodies for the bolts ==<br />
<br />
[[Image:HolderTop2-13.jpg|The sketch for the body for the bolts|thumb|right|400px]]<br />
The bolts need two cylindrical bodies on both sides of the main Body. Its best to include the 2 degree draft angle in the sketch. I tried revolving a cylinder and later applying a draft, but weird things happened after mirroring it and I couldn't put fillets on it because the surface was warped somehow.<br />
<br />
The sketch is dimensioned so that the rotation axis is 7mm distance to the outer diameter of the skeleton Body, because we want to drill a 14mm hole into it later. The wall thickness is another 5mm in addition to that. For the sake of having a fully parametric part, it is a good idea to add a plane to the Skeleton about 25mm above the XY-plane to mark the top of the cylinders. Since this will be machined, the sketch is dimensioned 3mm above it.<br />
<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-14.jpg|The body for the bolts|thumb|right|400px]]<br />
Create a revolution from the sketch and apply a fillet of 4mm to the top. This means that after machining away 3mm, a slight radius will remain which helps to avoid a sharp edge where someone could cut their hand when tightening the bolt.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-16.jpg|The main body with the two bodies for the bolts|thumb|right|400px]]<br />
Create a boolean feature to fuse the main Body and the bolt body. Then create a new body for the other side. Duplicate the sketch of the revolution, move it to this body and create the second body for the bolts (mirroring a Body is not supported yet so you need to redo most of it). Then fuse this second body into the main Body as well. Finally, apply a large fillet on the edge created by the boolean fuse operation. The largest I could get was 5mm and if you put in too much FreeCAD will crash (which is a known bug) so its better to start small and work your way up.<br />
<br clear=all><br />
<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-15.jpg|The completed raw part of the holder (without machining)|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". Put a 3mm fillet on the two edges resulting from the cut-out operation (again some edges remain that are "unfilletable"). The result should look like the picture on the right.<br />
<br />
The raw part is now completed. This is what the holder will look like before machining. Note that since the mold will have a top and bottom half, the edge between these two cannot be filleted. Also, if you give away this model to a foundry make sure to point out that it has the dimensions after casting. The foundry will then have to apply a certain percentage of shrinkage to the model (making the digital model used to manufacture the mold larger so that when the metal cools down and shrinks after casting it will have the right size).<br />
<br clear=all><br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=40011PartDesign Bearingholder Tutorial II2013-07-15T19:31:09Z<p>Jrheinlaender: /* Hollowing out the main body */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Adding the bodies for the bolts ==<br />
<br />
[[Image:HolderTop2-13.jpg|The sketch for the body for the bolts|thumb|right|400px]]<br />
The bolts need two cylindrical bodies on both sides of the main Body. Its best to include the 2 degree draft angle in the sketch. I tried revolving a cylinder and later applying a draft, but weird things happened after mirroring it and I couldn't put fillets on it because the surface was warped somehow.<br />
<br />
The sketch is dimensioned so that the rotation axis is 7mm distance to the outer diameter of the skeleton Body, because we want to drill a 14mm hole into it later. The wall thickness is another 5mm in addition to that. For the sake of having a fully parametric part, it is a good idea to add a plane to the Skeleton about 25mm above the XY-plane to mark the top of the cylinders. Since this will be machined, the sketch is dimensioned 3mm above it.<br />
<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-14.jpg|The body for the bolts|thumb|right|400px]]<br />
Create a revolution from the sketch and apply a fillet of 4mm to the top. This means that after machining away 3mm, a slight radius will remain which helps to avoid a sharp edge where someone could cut their hand when tightening the bolt.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-16.jpg|The main body with the two bodies for the bolts|thumb|right|400px]]<br />
Create a boolean feature to fuse the main Body and the bolt body. Then create a new body for the other side. Duplicate the sketch of the revolution, move it to this body and create the second body for the bolts (mirroring a Body is not supported yet so you need to redo most of it). Then fuse this second body into the main Body as well. Finally, apply a large fillet on the edge created by the boolean fuse operation. The largest I could get was 5mm and if you put in too much FreeCAD will crash (which is a known bug) so its better to start small and work your way up.<br />
<br clear=all><br />
<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-15.jpg|The completed raw part of the holder (without machining)|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". Put a 3mm fillet on the two edges resulting from the cut-out operation (again some edges remain that are "unfilletable"). The result should look like the picture on the right.<br />
<br />
The raw part is now completed. This is what the holder will look like before machining. Note that since the mold will have a top and bottom half, the edge between these to cannot be filleted. Also, if you give away this model to a foundry make sure to point out that it has the dimensions after casting. The foundry will then have to apply a certain percentage of shrinkage to the model (making the digital model larger so that when the metal cools down and shrinks after casting it will have the right size).<br />
<br clear=all><br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=40001PartDesign Bearingholder Tutorial II2013-07-15T19:30:46Z<p>Jrheinlaender: /* Hollowing out the main body */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Adding the bodies for the bolts ==<br />
<br />
[[Image:HolderTop2-13.jpg|The sketch for the body for the bolts|thumb|right|400px]]<br />
The bolts need two cylindrical bodies on both sides of the main Body. Its best to include the 2 degree draft angle in the sketch. I tried revolving a cylinder and later applying a draft, but weird things happened after mirroring it and I couldn't put fillets on it because the surface was warped somehow.<br />
<br />
The sketch is dimensioned so that the rotation axis is 7mm distance to the outer diameter of the skeleton Body, because we want to drill a 14mm hole into it later. The wall thickness is another 5mm in addition to that. For the sake of having a fully parametric part, it is a good idea to add a plane to the Skeleton about 25mm above the XY-plane to mark the top of the cylinders. Since this will be machined, the sketch is dimensioned 3mm above it.<br />
<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-14.jpg|The body for the bolts|thumb|right|400px]]<br />
Create a revolution from the sketch and apply a fillet of 4mm to the top. This means that after machining away 3mm, a slight radius will remain which helps to avoid a sharp edge where someone could cut their hand when tightening the bolt.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-16.jpg|The main body with the two bodies for the bolts|thumb|right|400px]]<br />
Create a boolean feature to fuse the main Body and the bolt body. Then create a new body for the other side. Duplicate the sketch of the revolution, move it to this body and create the second body for the bolts (mirroring a Body is not supported yet so you need to redo most of it). Then fuse this second body into the main Body as well. Finally, apply a large fillet on the edge created by the boolean fuse operation. The largest I could get was 5mm and if you put in too much FreeCAD will crash (which is a known bug) so its better to start small and work your way up.<br />
<br clear=all><br />
<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-16.jpg|The completed raw part of the holder (without machining)|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". Put a 3mm fillet on the two edges resulting from the cut-out operation (again some edges remain that are "unfilletable"). The result should look like the picture on the right.<br />
<br />
The raw part is now completed. This is what the holder will look like before machining. Note that since the mold will have a top and bottom half, the edge between these to cannot be filleted. Also, if you give away this model to a foundry make sure to point out that it has the dimensions after casting. The foundry will then have to apply a certain percentage of shrinkage to the model (making the digital model larger so that when the metal cools down and shrinks after casting it will have the right size).<br />
<br clear=all><br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=39991PartDesign Bearingholder Tutorial II2013-07-15T19:29:43Z<p>Jrheinlaender: /* Adding the bodies for the bolts */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Adding the bodies for the bolts ==<br />
<br />
[[Image:HolderTop2-13.jpg|The sketch for the body for the bolts|thumb|right|400px]]<br />
The bolts need two cylindrical bodies on both sides of the main Body. Its best to include the 2 degree draft angle in the sketch. I tried revolving a cylinder and later applying a draft, but weird things happened after mirroring it and I couldn't put fillets on it because the surface was warped somehow.<br />
<br />
The sketch is dimensioned so that the rotation axis is 7mm distance to the outer diameter of the skeleton Body, because we want to drill a 14mm hole into it later. The wall thickness is another 5mm in addition to that. For the sake of having a fully parametric part, it is a good idea to add a plane to the Skeleton about 25mm above the XY-plane to mark the top of the cylinders. Since this will be machined, the sketch is dimensioned 3mm above it.<br />
<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-14.jpg|The body for the bolts|thumb|right|400px]]<br />
Create a revolution from the sketch and apply a fillet of 4mm to the top. This means that after machining away 3mm, a slight radius will remain which helps to avoid a sharp edge where someone could cut their hand when tightening the bolt.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-16.jpg|The main body with the two bodies for the bolts|thumb|right|400px]]<br />
Create a boolean feature to fuse the main Body and the bolt body. Then create a new body for the other side. Duplicate the sketch of the revolution, move it to this body and create the second body for the bolts (mirroring a Body is not supported yet so you need to redo most of it). Then fuse this second body into the main Body as well. Finally, apply a large fillet on the edge created by the boolean fuse operation. The largest I could get was 5mm and if you put in too much FreeCAD will crash (which is a known bug) so its better to start small and work your way up.<br />
<br clear=all><br />
<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-12.jpg|The hollowed-out part|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". Put a 3mm fillet on the two edges resulting from the cut-out operation (again some edges remain that are "unfilletable"). The result should look like the picture on the right.<br />
<br clear=all><br />
<br />
<br />
<br />
The raw part is now completed. This is what the holder will look like before machining. Note that since the mold will have a top and bottom half, the edge between these to cannot be filleted. Also, if you give away this model to a foundry make sure to point out that it has the dimensions after casting. The foundry will then have to apply a certain percentage of shrinkage to the model (making the digital model larger so that when the metal cools down and shrinks after casting it will have the right size).<br />
<br clear=all><br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=File:HolderTop2-16.jpg&diff=39981File:HolderTop2-16.jpg2013-07-15T19:29:12Z<p>Jrheinlaender: </p>
<hr />
<div></div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=39971PartDesign Bearingholder Tutorial II2013-07-15T19:27:18Z<p>Jrheinlaender: /* Hollowing out the main body */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Adding the bodies for the bolts ==<br />
<br />
[[Image:HolderTop2-13.jpg|The sketch for the body for the bolts|thumb|right|400px]]<br />
The bolts need two cylindrical bodies on both sides of the main Body. Its best to include the 2 degree draft angle in the sketch. I tried revolving a cylinder and later applying a draft, but weird things happened after mirroring it and I couldn't put fillets on it because the surface was warped somehow.<br />
<br />
The sketch is dimensioned so that the rotation axis is 7mm distance to the outer diameter of the skeleton Body, because we want to drill a 14mm hole into it later. The wall thickness is another 5mm in addition to that. For the sake of having a fully parametric part, it is a good idea to add a plane to the Skeleton about 25mm above the XY-plane to mark the top of the cylinders. Since this will be machined, the sketch is dimensioned 3mm above it.<br />
<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-14.jpg|The body for the bolts|thumb|right|400px]]<br />
Create a revolution from the sketch and apply a fillet of 4mm to the top. This means that after machining away 3mm, a slight radius will remain which helps to avoid a sharp edge where someone could cut their hand when tightening the bolt.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-15.jpg|The completed raw part of the holder (without machining)|thumb|right|400px]]<br />
Create a boolean feature to fuse the main Body and the bolt body. Then create a new body for the other side. Duplicate the sketch of the revolution, move it to this body and create the second body for the bolts (mirroring a Body is not supported yet so you need to redo most of it). Then fuse this second body into the main Body as well. Finally, apply a large fillet on the edge created by the boolean fuse operation. The largest I could get was 5mm and if you put in too much FreeCAD will crash (which is a known bug) so its better to start small and work your way up.<br />
<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-12.jpg|The hollowed-out part|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". Put a 3mm fillet on the two edges resulting from the cut-out operation (again some edges remain that are "unfilletable"). The result should look like the picture on the right.<br />
<br clear=all><br />
<br />
<br />
<br />
The raw part is now completed. This is what the holder will look like before machining. Note that since the mold will have a top and bottom half, the edge between these to cannot be filleted. Also, if you give away this model to a foundry make sure to point out that it has the dimensions after casting. The foundry will then have to apply a certain percentage of shrinkage to the model (making the digital model larger so that when the metal cools down and shrinks after casting it will have the right size).<br />
<br clear=all><br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=39961PartDesign Bearingholder Tutorial II2013-07-15T19:26:57Z<p>Jrheinlaender: /* Adding the bodies for the bolts */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-12.jpg|The hollowed-out part|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". Put a 3mm fillet on the two edges resulting from the cut-out operation (again some edges remain that are "unfilletable"). The result should look like the picture on the right.<br />
<br clear=all><br />
<br />
<br />
<br />
The raw part is now completed. This is what the holder will look like before machining. Note that since the mold will have a top and bottom half, the edge between these to cannot be filleted. Also, if you give away this model to a foundry make sure to point out that it has the dimensions after casting. The foundry will then have to apply a certain percentage of shrinkage to the model (making the digital model larger so that when the metal cools down and shrinks after casting it will have the right size).<br />
<br clear=all><br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=File:HolderTop2-15.jpg&diff=39951File:HolderTop2-15.jpg2013-07-15T19:26:03Z<p>Jrheinlaender: </p>
<hr />
<div></div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=File:HolderTop2-14.jpg&diff=39941File:HolderTop2-14.jpg2013-07-15T19:25:42Z<p>Jrheinlaender: </p>
<hr />
<div></div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=39931PartDesign Bearingholder Tutorial II2013-07-15T19:25:10Z<p>Jrheinlaender: /* Adding the bodies for the bolts */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-12.jpg|The hollowed-out part|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". Put a 3mm fillet on the two edges resulting from the cut-out operation (again some edges remain that are "unfilletable"). The result should look like the picture on the right.<br />
<br clear=all><br />
<br />
== Adding the bodies for the bolts ==<br />
<br />
[[Image:HolderTop2-13.jpg|The sketch for the body for the bolts|thumb|right|400px]]<br />
The bolts need two cylindrical bodies on both sides of the main Body. Its best to include the 2 degree draft angle in the sketch. I tried revolving a cylinder and later applying a draft, but weird things happened after mirroring it and I couldn't put fillets on it because the surface was warped somehow.<br />
<br />
The sketch is dimensioned so that the rotation axis is 7mm distance to the outer diameter of the skeleton Body, because we want to drill a 14mm hole into it later. The wall thickness is another 5mm in addition to that. For the sake of having a fully parametric part, it is a good idea to add a plane to the Skeleton about 25mm above the XY-plane to mark the top of the cylinders. Since this will be machined, the sketch is dimensioned 3mm above it.<br />
<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-14.jpg|The body for the bolts|thumb|right|400px]]<br />
Create a revolution from the sketch and apply a fillet of 4mm to the top. This means that after machining away 3mm, a slight radius will remain which helps to avoid a sharp edge where someone could cut their hand when tightening the bolt.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-15.jpg|The completed raw part of the holder (without machining)|thumb|right|400px]]<br />
Create a boolean feature to fuse the main Body and the bolt body. Then create a new body for the other side. Duplicate the sketch of the revolution, move it to this body and create the second body for the bolts (mirroring a Body is not supported yet so you need to redo most of it). Then fuse this second body into the main Body as well. Finally, apply a large fillet on the edge created by the boolean fuse operation. The largest I could get was 5mm and if you put in too much FreeCAD will crash (which is a known bug) so its better to start small and work your way up.<br />
<br />
The raw part is now completed. This is what the holder will look like before machining. Note that since the mold will have a top and bottom half, the edge between these to cannot be filleted. Also, if you give away this model to a foundry make sure to point out that it has the dimensions after casting. The foundry will then have to apply a certain percentage of shrinkage to the model (making the digital model larger so that when the metal cools down and shrinks after casting it will have the right size).<br />
<br clear=all><br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=39921PartDesign Bearingholder Tutorial II2013-07-15T19:14:26Z<p>Jrheinlaender: /* Adding the bodies for the bolts */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-12.jpg|The hollowed-out part|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". Put a 3mm fillet on the two edges resulting from the cut-out operation (again some edges remain that are "unfilletable"). The result should look like the picture on the right.<br />
<br clear=all><br />
<br />
== Adding the bodies for the bolts ==<br />
<br />
[[Image:HolderTop2-13.jpg|The sketch for the body for the bolts|thumb|right|400px]]<br />
The bolts need two cylindrical bodies on both sides of the main Body. Its best to include the 2 degree draft angle in the sketch. I tried revolving a cylinder and later applying a draft, but weird things happened after mirroring it and I couldn't put fillets on it because the surface was warped somehow.<br />
<br />
The sketch is dimensioned so that the rotation axis is 7mm distance to the outer diameter of the skeleton Body, because we want to drill a 14mm hole into it later. The wall thickness is another 5mm in addition to that. For the sake of having a fully parametric part, it is a good idea to add a plane to the Skeleton about 25mm above the XY-plane to mark the top of the cylinders. Since this will be machined, the sketch is dimensioned 3mm above it.<br />
<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-14.jpg|The body for the bolts|thumb|right|400px]]<br />
Create a revolution from the sketch and apply a fillet of 4mm to the top. This means that after machining away 3mm, a slight radius will remain which helps to avoid a sharp edge where someone could cut their hand when tightening the bolt.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-15.jpg|The completed raw part of the holder (without machining)|thumb|right|400px]]<br />
Create a boolean feature to fuse the main Body and the bolt body. Then create a new body for the other side. Duplicate the sketch of the revolution, move it to this body and create the second body for the bolts (mirroring a Body is not supported yet so you need to redo most of it). Then fuse this second body into the main Body as well. Finally, apply a large fillet on the edge created by the boolean fuse operation. The largest I could get was 6mm and if you put in too much FreeCAD will crash (which is a known bug) so its better to start small and work your way up.<br />
<br />
<br clear=all><br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=39911PartDesign Bearingholder Tutorial II2013-07-15T14:00:04Z<p>Jrheinlaender: /* Hollowing out the main body */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-12.jpg|The hollowed-out part|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". Put a 3mm fillet on the two edges resulting from the cut-out operation (again some edges remain that are "unfilletable"). The result should look like the picture on the right.<br />
<br clear=all><br />
<br />
== Adding the bodies for the bolts ==<br />
<br />
[[Image:HolderTop2-13.jpg|The sketch for the body for the bolts|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=File:HolderTop2-13.jpg&diff=39901File:HolderTop2-13.jpg2013-07-15T13:59:39Z<p>Jrheinlaender: </p>
<hr />
<div></div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=39891PartDesign Bearingholder Tutorial II2013-07-15T12:39:39Z<p>Jrheinlaender: /* Hollowing out the main body */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-12.jpg|The hollowed-out part|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". Put a 3mm fillet on the two edges resulting from the cut-out operation (again some edges remain that are "unfilletable"). The result should look like the picture on the right.<br />
<br clear=all><br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=File:HolderTop2-11.jpg&diff=39741File:HolderTop2-11.jpg2013-07-14T18:49:41Z<p>Jrheinlaender: </p>
<hr />
<div></div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=39731PartDesign Bearingholder Tutorial II2013-07-14T18:48:40Z<p>Jrheinlaender: /* Hollowing out the main body */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-11.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-12.jpg|The hollowed-out part|thumb|right|400px]]<br />
We are ready to hollow out the main body. Select it and choose to create a new Boolean operation. Add the cut-out body to the list window and set the operation to "Cut". The result should look like the picture on the right.<br />
<br clear=all><br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=39721PartDesign Bearingholder Tutorial II2013-07-14T18:45:47Z<p>Jrheinlaender: /* Hollowing out the first body */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Hollowing out the main body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The complete cut-out body (minus impossible fillets)|thumb|right|400px]]<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
<br clear=all><br />
<br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=39711PartDesign Bearingholder Tutorial II2013-07-14T18:44:19Z<p>Jrheinlaender: /* Hollowing out the first body */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Hollowing out the first body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting. Apply a general fillet of 3mm to all edges. You will notice that there are several edges that cannot be filleted... this is a defect of the underlying geometric kernel which FreeCAD uses.<br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=39701PartDesign Bearingholder Tutorial II2013-07-14T18:43:31Z<p>Jrheinlaender: /* The first body */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The main body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Hollowing out the first body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting.<br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=39691PartDesign Bearingholder Tutorial II2013-07-14T18:42:19Z<p>Jrheinlaender: /* Design data */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308 which has an inside diameter of 40mm). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
<br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The first body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Hollowing out the first body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting.<br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=39681PartDesign Bearingholder Tutorial II2013-07-14T18:41:29Z<p>Jrheinlaender: /* Hollowing out the first body */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The first body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Hollowing out the first body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br clear=all><br />
<br />
Now all that remains is to apply draft to the planar side faces, using the same neutral plane as for the main body, and filleting.<br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=39671PartDesign Bearingholder Tutorial II2013-07-14T18:37:15Z<p>Jrheinlaender: /* Hollowing out the first body */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The first body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Hollowing out the first body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The first Pad of the cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Next we want two more Pads to hollow out the place for the sealing rings. Duplicate the sketch of the first pad of the cut-out Body and map it to the XZ-plane. Edit the sketch and replace the external reference with the outer diameter of the bearing sealing ring. Extrude this sketch to an offset of 3mm of the side of the sealing ring. Repeat the whole process for the sealing ring on the other side.<br />
<br />
After this we want to create two more Pads like the last two to give the shaft a clearance (e.g. 3mm) inside the holder.<br />
<br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=File:HolderTop2-10.jpg&diff=39661File:HolderTop2-10.jpg2013-07-14T18:37:06Z<p>Jrheinlaender: Jrheinlaender uploaded a new version of &quot;File:HolderTop2-10.jpg&quot;</p>
<hr />
<div></div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=39651PartDesign Bearingholder Tutorial II2013-07-14T18:24:49Z<p>Jrheinlaender: /* Hollowing out the first body */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The first body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Hollowing out the first body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The cut-out body inside the main body|thumb|right|300px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
[[Image:HolderTop2-10.jpg|The cut-out body inside the skeleton body|thumb|right|300px]]<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=39641PartDesign Bearingholder Tutorial II2013-07-14T18:24:25Z<p>Jrheinlaender: /* Hollowing out the first body */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The first body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Hollowing out the first body ==<br />
<br />
[[Image:HolderTop2-9.jpg|The cut-out body inside the main body|thumb|right|400px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
[[Image:HolderTop2-9.jpg|The cut-out body inside the skeleton body|thumb|right|400px]]<br />
Create a new body and make it active. First, we need a datum plane offset 3mm inside the skeleton face that shows the side of the bearing. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Map the sketch onto the datum plane (if the sketch turns upside-down after mapping, move the datum plane to the other side of the bearing, next to where the duplicated sketch is located). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br clear=all><br />
<br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=File:HolderTop2-10.jpg&diff=39631File:HolderTop2-10.jpg2013-07-14T18:23:42Z<p>Jrheinlaender: </p>
<hr />
<div></div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=File:HolderTop2-9.jpg&diff=39621File:HolderTop2-9.jpg2013-07-14T18:23:21Z<p>Jrheinlaender: </p>
<hr />
<div></div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=39611PartDesign Bearingholder Tutorial II2013-07-14T17:58:41Z<p>Jrheinlaender: /* The first body */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The first body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
== Hollowing out the first body ==<br />
<br />
[[Image:HolderTop2-9.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
We will now work on the inside of the holder and hollow it out to make space for the bearing and sealing rings. When doing this of course we need to keep in mind the 3mm machining allowance. Since this tutorial teaches the multi-body method, we will create the inside geometry as a separate body and then cut it out of the main body with a boolean operation.<br />
<br />
Create a new body and make it active. Then, duplicate the sketch of the first Pad of the main body. It will be added to the main body, so right-click on it and choose to move it to the newly created body (this option is only available in the context menu if the PartDesign workbench is active). Now, modify the sketch so that the diameter is 3mm less than the outer diameter of the skeleton geometry that represents the bearing. All you need to do is remove the 5mm dimension, drag the sketch inside the reference circle, and create a new 3mm dimension.<br />
<br />
<br />
<br />
[[Category:Tutorials]]</div>Jrheinlaenderhttps://wiki.freecad.org/index.php?title=PartDesign_Bearingholder_Tutorial_II&diff=39591PartDesign Bearingholder Tutorial II2013-07-11T19:23:19Z<p>Jrheinlaender: /* The first body */</p>
<hr />
<div>[[Image:HolderTop2-1.jpg|Bearing Holder Tutorial - Finished bearing holder (top)|thumb|right|400px]]<br />
<br />
This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and fillets. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.<br />
<br />
This is the second part of the tutorial. It will use what might be called the 'multiple body' workflow, using the (simpler) top part of the holder as an example.<br />
<br />
Obviously, to follow through this tutorial you must activate the PartDesign workbench.<br />
<br clear=all><br />
<br />
== Design data ==<br />
<br />
The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.<br />
<br />
The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.<br />
<br />
<br clear=all><br />
== Setting up the skeleton geometry ==<br />
<br />
[[Image:HolderTop2-2.jpg|Sketch of the skeleton geometry|thumb|right|400px]]<br />
Create a new part in the PartDesign workbench. Rename the Body that is created by default to Skeleton. This Body is probably activated already, which you can see by the blue background colour in the feature tree. Create a new sketch on the YZ plane containing the outline of the shaft, bearing and sealing rings. After finishing the sketch, make a revolution feature from it. This skeleton feature will later be used to reference the real geometry to it. This means that if you want to change any dimensions, all you need to do is adjust the skeleton feature's dimensions and the rest of the part will update accordingly.<br />
[[Image:HolderTop2-2-1.jpg|The skeleton geometry|thumb|right|400px]]<br />
<br />
<br clear=all><br />
<br />
== The first body ==<br />
<br />
[[Image:HolderTop2-3.jpg|Sketch of the first Pad|thumb|right|400px]]<br />
Create a new body and make it active. The sketch for the first pad is shown on the right. It is placed on a datum plane with an offset of 5mm (wall thickness) from the skeleton face marking the side of one of the bearing sealing rings. Because all the important dimensions are taken from the skeleton, there are just three dimensions: The machining allowance (3mm) at the base as an offset to the XY-plane, the 5mm wall thickness from the outer diameter of the skeleton, and the two degrees draft angle. Two create the 5mm dimension, you first need to select the outer circle (radius 45mm) of the skeleton geometry as external geometry in the sketcher, and then put in a construction line constrained tangential to this circle and at an angle of two degrees.<br />
<br />
You are probably wondering why there is this small straight segment at the bottom of each arc. This segment ensures that there will be a draft angle of 2 degrees on the arcs. This might look like a lot of work for a very small benefit, but many CAD programs (and maybe FreeCAD one day) have tools that highlight a solid model in different colours and immediately show you all faces where the draft angle is not correct. You don't want that to happen to your model, especially after putting on a lot of fillets!<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-4.jpg|The first Pad|thumb|right|400px]]<br />
When you have done the sketch (which is a bit tricky because of the 2 degree tangential lines), create a Pad from it extending up to the other side of the skeleton geometry, again with a 5mm offset to the side face. You don't need to create a datum plane this time, the "up to face" mode of the Pad dialog offers to input an offset.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-5.jpg|Sketch for Pad cut-out|thumb|right|400px]]<br />
Next, we will cut away some material on both ends of the Pad because it is always ideal for cast parts to have as uniform a wall thickness as possible. Create a sketch on each of the end faces of the Pad and dimension it at 5mm offset from the circle representing the bearing sealing ring (radius 27.5mm on one side and 34mm on the other). For the bottom line segment of the sketch, create another external geometry from the Pad and constrain to this. Thus the sketch has only a single dimension, the 5mm wall thickness (the 150mm and 75mm dimensions are not important as long as they are large enough to ensure that everything is cut away).<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-6.jpg|The Pad with cut-outs to achieve uniform wall thickness|thumb|right|400px]]<br />
Use the sketch you created to make a Pocket and extend it to the face of the skeleton geometry that represents the bearing, minus 5mm offset for the wall thickness. For the second Pocket, you can use the option "Duplicate selected object" from the Edit menu to duplicate the sketch you already made (choose not to duplicate dependend objects if the question pops up). Then, select the face you want to move this sketch to, and tell FreeCAD to map the sketch to this face (this is an item on the PartDesign menu). After creating the second Pocket, you can look at the result from the bottom to check that you have a uniform wall thickness of 5mm around the contour of the skeleton geometry.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-7.jpg|Neutral plane for applying draft|thumb|right|400px]]<br />
Now it's time to create draft and fillets. The draft feature requires a neutral plane, meaning that the geometry that is cut by this plane will remain in its place, while the rest of the face is tilted at the draft angle. Using the bottom of the Pad for this purpose for this is not a good idea, because the wall thickness in the top part of the holder would become less than 5mm. So we create a datum plane offset about 35mm from the XY for this purpose. Activate the Skeleton body and create the plane there, because we will need it for applying draft to other bodies, too.<br />
<br clear=all><br />
<br />
[[Image:HolderTop2-8.jpg|First body with draft and fillets|thumb|right|400px]]<br />
The picture on the right shows the finished first body with draft and fillets applied. Note that the outer (concave) edges have a larger fillet radius of 5mm, again with the purpose of creating a more uniform wall thickness (more than 5mm is not possible because then after machining the inside of the holder the wall thickness would become less than 5mm).<br />
<br clear=all><br />
<br />
[[Category:Tutorials]]</div>Jrheinlaender