Basic Part Design Tutorial 017/de

Dieses Tutorial richtet sich an Anfänger und beschreibt einige, aber nicht alle, Werkzeuge und Techniken des Arbeitsbereichs Part Design. Dem Leser wird dabei Schritt für Schritt erklärt, wie das in der nachfolgenden Abbildung sichtbare Modell mittels Skizzen in FreeCAD erstellt werden kann.

Dieses Tutorial basiert auf Basic Part Design Tutorial von Quick61 mit Änderungen für die Version v0.17.

Ein Video (englisch) der kompletten Konstruktion finden Sie hier: https://youtu.be/geIrH1cOCzc

( Für jeden Teilbereich gibt es auch ein einzelnes Video )

Die Aufgabe
In diesem Tutorial verwenden Sie den Part Design Arbeitsbereich (Workbench), um ein 3D-Volumenmodell des in der Zeichnung (Drawing) gezeigten Teils zu erstellen. Alle notwendigen Abmessungen, um diese Aufgabe zu erfüllen, sind angegeben. Sie beginnen damit, dass Sie eine Kernform aus einer Basisskizze erstellen und dann auf dieser Form aufbauen, indem Sie sogenannte Features hinzufügen. Diese Features oder Formelemente fügen entweder dem Material Material hinzu oder entfernen es mithilfe zusätzlicher Skizzen und begleitender Feature-Operationen. Dieses Tutorial wird nicht alle Funktionen und Werkzeuge verwenden, die in der Part Design Workbench verfügbar sind, sollte aber das nötige verwenden, um dem Benutzer dieses Tutorials eine grundlegende Grundlage zu geben, auf der er sein Wissen und seine Fähigkeiten aufbauen kann.

Start
Beginnen Sie zuerst damit, dass Sie in die Part Design Workbench wechseln. Dort sollten Sie ein neues Dokument erstellen, wenn Sie dies noch nicht getan haben. Es empfiehlt sich, die Arbeit oft zu speichern, also speichern Sie das neue Dokument vor der Bearbeitung und geben Sie ihm einen beliebigen Namen.

Alle Arbeiten in Part Design beginnen mit einem Bauteil (Body). Klicken Sie auf diese Schaltfläche, um ein neues Bauteil zu erstellen und es zu aktivieren. Das Bauteil enthält am Ende mindestens einen Festkörper (Solid). Hier erstellen wir diesen aus einer Skizze (Sketcher). Klicken Sie auf diese Schaltfläche, um eine neue Skizze innerhalb des gerade erstellten Bauteils zu erstellen. Die erste Skizze basiert auf einer Ebene aus dem Ursprung (Origin). Wählen Sie hier die YZ_Ebene (Plane). Nun erscheint im 3D Fenster der Skizziermodus(Sketch)

Als nächstes wollen Sie das Polylinien-Werkzeug verwenden und eine Form ähnlich der im nächsten Bild erstellen. Es muss nicht perfekt sein, da die endgültige Form mit Einschränkungen gemacht wird. Sobald Sie die Grundform haben, werden wir anfangen, die Einschränkungen anzuwenden. Wenn Sie die automatischen Beschränkungen aktiviert haben, werden einige dieser Einschränkungen automatisch angewendet. Wenn nicht, führen Sie die folgenden Schritte aus.


 * 1) Select the two horizontal lines with your mouse by clicking on them, and once selected, click on the Constraint Horizontal.png horizontal constraint.
 * 2) Select the vertical line on the right and then click on the Constraint Vertical.pngcal constraint.
 * 3) Select the start and end points of your polyline and click on the Constraint PointOnPoint.png coincident constraint to close the polyline.
 * 4) Select the bottom horizontal line and the right vertical line and apply and Constraint EqualLength.png equal constraint.
 * 5) Select either the horizontal or vertical line and apply either a corresponding Constraint HorizontalDistance.png horizontal or Constraint VerticalDistance.png vertical distance constraint and give it a value of 26 mm.
 * 6) Select the top horizontal line and apply the horizontal distance constraint and give it a value of 5 mm
 * 7) Select the lower right point, (vertice) of the horizontal line Origin and then the center point of the grid and apply the Constraint PointOnPoint.png coincidence  constraint to fix your shape.

At this point you should have a fully constrained sketch as indicated by it changing color and the message shown in the Combo View. It should now look just like the image below. Now in the Combo View, click on the Close button to leave the sketch edit mode and select Pad from the toolbar or from the Part Design menu. This will give you a Pad dialog in the Combo View. Using that dialog, first using the Type pulldown menu, select Two dimensions. Drawing presented at the beginning of this tutorial says the part is 53 mm long. We do it by Padding our sketch both ways from the center plane to make up that distance i.e. make the pad symmetric in relation of sketch-plane. The reason for is seen later when creating features. For now, given we want it to be 53 mm long in total we will input 26.5 for Length, and 26.5 again for the Second length. Alternatively, you can provide a single length of 53 mm and click the Symmetric to plane check box. Once that is done we now have our base solid upon which we will add additional features to construct our part.

A video of the steps used in this portion of the tutorial is here: https://youtu.be/cUyPnCMeTgg

Features with pocket and external geometry
Using the mouse or the view icons turn the model around so you can see its back. Once the back of the part is visible, select the back face by clicking on it as seen in the next image. After the face is selected, click on the New sketch icon in the toolbar or from the Part Design menu and that will map our next sketch to the back face of the part. Now select rectangle tool and place a rectangle on the rear face of the part in a similar fashion as shown below. Now following the steps listed, constrain the sketch.


 * 1) Select one of the horizontal lines apply a horizontal distance constraint and a value of 5 mm.
 * 2) Select one of the vertical lines and give it a vertical distance constraint and a value of 11 mm.
 * 3) Use Sketcher_External.png External geometry tool and select the upper right vertex of the face and click it so you are provided a point from the external geometry to link our sketch to.

Select that point you just made available with the External geometry tool and then select the upper right vertex of the rectangle and click on the coincident constraint. At this point the sketch should be fully constrained and look like the next image. Once that is done, click the Close button at the top of the Tasks tab in the Combo View window, then select Pocket tool from the toolbar or Part Design menu. Using this tool is the opposite of the Pad tool. As the Pad tool adds material to the part, the Pocket tool removes material from the part. Both operations are called features. In this Pocket operation we want to select Through all from the type pulldown-menu and then click the OK button.

For the next operation, make sure that “Pocket” is selected in the Model tree view and once done, click on the Mirror feature on the toolbar or from the Part Design menu. In the Mirror dialog in the Combo View, select Horizontal sketch axis from the Plane pulldown menu. Then click OK. The Mirror feature works in this way because the base feature of our model was Padded both ways from the horizontal plane in the first operation with the base sketch. If all has gone well, you should now have a part that looks like the image below after you orbit it around to the front.



A video of the steps used in this portion of the tutorial is here: https://youtu.be/wiGXV9G7mrM

Features with pad and external geometry
After taking a look, orbit back around and once again select the back face of the part and select that face to map the next sketch to. Select New sketch and make a new rectangle in the manner similar to what is shown below in the next image. Then proceed to add dimensional constraints to the rectangle.

Now selecting the upper left vertex of the rectangle and the external geometry point, click on the coincident constraint to fully constrain the sketch. Next we will click on the Pad feature and in the Pad dialog in the Combo View we want a length of 26 mm leaving the type as Dimension and then placing a check on the Reversed checkbox. Using the Reversed checkbox will cause the Pad to go into the part instead of away from the part. This operation provides with the following result. Once again use the Mirror feature to get the second pad. First ensure that created Pad is selected in the tree view, then click on Mirror in the toolbar of select it from the Part Design menu. We will repeat the operation we did for Pocket above and select Horizontal sketch axis from the Plane pulldown menu.
 * 1) Select a horizontal line and apply a horizontal distance constraint with a value of 16.7.
 * 2) Select a vertical line and apply a vertical distance constraint of 7 mm
 * 3) Using the External geometry tool, select the upper left vertex of the part face.

A video of the steps used in this portion of the tutorial is here: https://youtu.be/Ido1owp8ubc

Feature with pocket and external geometry
At this point orbiting the part around to the front, we can see that our part is now starting to look like the part in the dimensioned drawing at the beginning of this tutorial. Once you have the view of the front, click on the sloped face with your mouse to select the face we will use for the next sketch. Here we will use the rectangle tool and place a rectangle in our sketch and once having done so, apply the following constraints.


 * 1) Select a horizontal line and a vertical line, and after both are selected, click on the Equals constraint.
 * 2) Select either a horizontal or vertical line and apply a corresponding horizontal or vertical distance constraint with a value of 17 mm
 * 3) Using the External geometry tool, select the top right vertex as shown in the image below.

Now using the dimensions from the drawing, apply the following constraints.


 * 1) Select the external geometry point and the upper right vertex of the now square sketch and apply a horizontal distance constraint of 7 mm
 * 2) Select the external geometry point and the upper right vertex of the now square sketch and apply a vertical distance constraint of 11 mm

The result should be as follows.



At this point if we were to simply Pocket this sketch, the resulting hole would be perpendicular to the sloped face that it is mapped to, and this is not what we want.



We want the hole to be perpendicular to the back face, but it's projected dimensions are not the 17 mm x 17 mm dimensions that are given in the drawing. Now we could do the math and calculate the dimensions needed, or we can use the tools provided in FreeCAD to make that projection for us.

A video of the steps used in this portion of the tutorial is here: https://youtu.be/x4d5nZPWCLQ

To create pocket which has the sloped rectangle as it´s outlet, we draw a new rectangle on the rear side, using the projection of the sloped rectangle as an external reference. Orbit the Solid around to see the rear face of the part once again and select the back face to map the final sketch to. Select New Sketch from the toolbar or Part Design menu. Now in sketch edit mode, we do not see the sketched rectangle of the slope. To make it selectable, we switch the combo view to model tab and select the last sketch made (Sketch003) on the sloped plane. Then using the spacebar, make it visible. Next, select the mirror feature above (mirrored001) and again using spacebar, hide it. Then you should see the rectangle inside the 3D View. You may continue to work with the model tab visible, or switch back to tasks tab. Using the External geometry tool, select the upper and lower  horizontal edges of the sloped rectangle.




 * 1) Select the upper left vertex of the rectangle and the upper left point of the external geometry and click on the coincident constraint.
 * 2) Click on the lower right vertex of the rectangle and the lower right point of the external geometry and click on the coincident constraint.

And we should end up with this.

For the final step in this tutorial, close the sketcher window using close or fish editing from the context menu of sketch004 and then select the Pocket feature from the toolbar or from the Part Design menu. From the Type pulldown select Through all and click the OK button.

At this point, you will see some lines which come from intersecting features. In this case the side block intersects with the base profile letting it appear as a triangular block above the profile. To remove these lines, you can either switch on "refine shape" in your Part Design Settings or, to save some processing speed and still have these lines while constructing, individually switch it on at each feature, which will create such lines. The Setting on feature level can be done in the "data" tab of the feature. Set the refine property to TRUE to invoke refining.



A video of these steps of the tutorial is here: https://youtu.be/UYI0gvxCYeI

This tutorial and your model are complete.

Additional Resources

 * Links to accompanying video have been included.


 * FreeCAD file for comparison (made with 0.17) Download