Manual:Preparing models for 3D printing/ro

Una dintre principalele utilizări ale FreeCAD este de a produce obiecte în lumea reală. Acestea pot fi proiectate în FreeCAD și apoi materializat în diferite moduri, cum ar fi cele comunicarea altor persoane care le vor construi sau, tot mai des, trimise direct la o 3D printer sau la o CNC mill. Capitolul său vă va arăta cum să vă pregătiți modelele pentru a le trimite la aceste mașini-unelte.

Dacă ați fost prudenți în timpul modelării, cea mai mare parte a dificultăților întâmpinate la imprimarea modelului dvs. în 3D a fost deja evitată. Aceasta implică în principiu:


 * Asigurarea că obiectele dvs sunt solid. obiectele din lumea reală sunt solide ( sau cel puțin cochilii), modelul 3D trebuie să fie și solid. Am văzut în capitolele anterioare că FreeCAD vă ajută foarte mult în această privință, și că PartDesign Workbench vă va anunța dacă efectuați o operație care împiedică modelul să rămână solid. Atelierul Part Workbench conține de asemenea uin instrument [[Image:Part_CheckGeometry.png|16px]] Check Geometry care este util pentru a verifica în continuare posibilele defecte.
 * Asigurați-vă de unitățile de măsură folosite la cotele/ dimensiunile obiectului dvs. Un milimetru în desen va fi un milimetru în viața reală. Fiecare cotă/dimensiune are importanță.
 * Controlarea degradării. Nicio imprimantă 3D sau sistem de frezare CNC nu poate prelua direct fișierele FreeCAD. Multe dintre ele vor înțelege doar limbajul mașină numit G-Code. Codul G are zeci de dialecte diferite, fiecare mașină sau vânzător de mașini are de obicei propria sa variantă. Conversia modelelor dvs. în G-Code poate fi ușoară și automată, dar o puteți face și manual, cu un control total asupra ieșirii. În orice caz, o anumită pierdere a calității modelului dvs. va apărea în mod inevitabil în timpul procesului. Când printați în 3D, trebuie să vă asigurați întotdeauna că această pierdere de calitate rămâne sub exigențile dvs. minime.

Mai jos, vom presupune că sunt îndeplinite primele două criterii și că până acum puteți produce obiecte solide cu dimensiuni corecte. Vom vedea acum cum să abordăm al treilea punct.

Exportarea feliilor
Aceasta este metoda cea mai frecvent utilizată pentru tipărirea 3D. Obiectul 3D este exportat către un alt program (dispozitivul de feliere), care va genera codul G de la obiect, prin împărțirea acestuia în straturi subțiri (de aici numele), care vor reproduce mișcările pe care le va face imprimanta 3D. Deoarece multe dintre aceste imprimante sunt construite acasă, există adesea diferențe mici de la una la alta. Aceste programe oferă de obicei posibilități avansate de configurare care vă permit să adaptați ieșirea exact pentru caracteristicile imprimantei 3D.

De fapt Imprimarea 3D este, totuși, un subiect prea vast pentru acest manual. Dar vom vedea cum să exportați și să utilizați acești sliceri pentru a verifica dacă output-ul este corectă.

Conversia obiectelor în ochiuri de plase

Niciunul dintre sliceri nu va prelua, în acest moment, o geometrie solidă pe măsură ce o producem în FreeCAD. Așa că va trebui să convertim pentru început orice obiect pe care dorim să-l tipărim 3 D într-o plasă mesh, pe care se poate deschide feliatorul. Din fericire, transformarea unei rețele într-un solid nu este o operație complicată, dimpotrivă, transformarea unui solid într-o rețea, este foarte simplă. Tot ce trebuie, este să fim atenți, pentru că se va produce degradarea menționată mai sus. Trebuie să verificăm dacă degradarea rămâne în limite acceptabile.

Toate manipulările cu plase, în FreeCAD, sunt realizate de un alt atelier de lucru specific Mesh Workbench. Ace3st atelier conține, în plus față de cele mai importante instrumente care fac conversia între obeicte Part și obeicte Mesh, mai multe utilitare sunt menite să analizeze și să repare ochiurile. Deși lucrul cu ochiurile nu este în centrul FreeCAD, atunci când lucrați cu modelarea 3D, adesea trebuie să vă ocupați cu obiecte tip plasă, deoarece utilizarea lor este foarte răspândită printre alte aplicații. Acest atelier de lucru vă permite să le gestionați pe deplin în FreeCAD.


 * Let's convert one of the objects we modelled in the previous chapters, such as the lego piece (which can be downloaded from the end of the previous chapter).
 * Open the FreeCAD file containing the lego piece.
 * Switch to the Mesh Workbench
 * Select the lego brick
 * Select menu Meshes -> Create Mesh from Shape
 * A task panel will open with several options. Some additional meshing algorithms (Mefisto or Netgen) might not be available, depending on how your version of FreeCAD was compiled. The Standard meshing algorithm will always be present. It offers less possibilities than the two others, but is totally sufficient for small objects that fit into the maximum print size of a 3D printer.




 * Select the Standard mesher, and leave the deviation value to the default value of 0.10. Press Ok.
 * A mesh object will be created, exactly on top of our solid object. Either hide the solid, or move one of the objects aside, so you can compare both.
 * Change the View -> Display Mode property of the new mesh object to Flat Lines, in order to see how the triangulation occurred.
 * If you are not happy, and think that the result is too coarse, you can repeat the operation, lowering the deviation value. In the example below, the left mesh used the default value of 0.10, while the right one uses 0.01:



In most cases, though, the default values will give a satisfying result.


 * We can now export our mesh to a mesh format, such as STL, which is currently the most widely used format in 3D printing, by using menu File -> Export and choosing the STL file format.

If you don't own a 3D printer, it is usually very easy to find commercial services that will print and send you the printed objects by mail. Among the famous ones are Shapeways and Sculpteo, but you will usually find many others in your own city. In all major cities, you will nowadays find Fab labs, which are workshops equipped with a range of 3D manufacturing machines, almost always including at least one 3D printer. Fab labs are usually community spaces, that will let you use their machines, for a fee or for free depending on the Fab lab, but also teach you how to use them, and promote other activities around 3D manufacturing.

Using Slic3r
Slic3r is an application that converts STL objects into G-code that can be sent directly to 3D printers. Like FreeCAD, it is free, open source and runs on Windows, Mac OS and Linux. Correctly configuring things for 3D printing is a complicated process, where you must have a good knowledge of your 3D printer, so it is not very useful to generate G-code before actually going to print (your G-code file might not work well on another printer), but it is useful for us anyway, to check that our STL file will be printable without problems.

This is our exported STL file opened in Slic3r. By using the preview tab, and moving the right slider, we can visualize the path that the 3D printer head will follow to construct our object.



Using the Cura addon
Warning: the Cura addon is currently not functional for FreeCAD 0.17!

Cura is another free and open source slicer application for Windows, Mac and Linux, maintained by the 3D printer maker Ultimaker. Some FreeCAD users have created a Cura Workbench that uses cura internally. The Cura Workbench is available from the FreeCAD addons repository. To use the Cura Workbench, you also need to install Cura itself, which is not included in the workbench.

Once you have installed both Cura and the Cura Workbench, you will be able to use it to produce the G-code file directly from Part objects, without the need to convert them to meshes, and without the need to open an external application. Producing another G-code file from our Lego brick, using the Cura Workbench this time, is done as follows:


 * Load the file containing our Lego brick (it can be downloaded at the end of the previous chapter)
 * Switch to the Cura Workbench
 * Setup the printer space by choosing menu 3D printing -> Create a 3D printer definition. Since we aren't going to print for real, we can leave the settings as they are. The geometry of the printing bed and available space will be shown in the 3D view.
 * Move the Lego brick to a suitable location, such as the center of the printing bed. Remember that PartDesign objects cannot be moved directly, so you need either to move its very first sketch (the first rectangle), or to move (and print) a copy, which can be made with the Part -> Create Simple Copy tool. The copy can be moved, for example with [[Image:Draft_Move.png|16px]] Draft -> Move.
 * Select the object to be printed, and select menu 3D printing -> Slice with Cura Engine.
 * In the task panel that will open, make sure the path to the Cura executable is correctly set. Since we are not going to really print, we can leave all other options as they are. Press Ok. Two files will be generated in the same directory as your FreeCAD file, an STL file and a G-code file.




 * The generated G-code can also be re-imported into FreeCAD (using the slic3r preprocessor) for checking.

Generating G-code
Warning: This section was made for FreeCAD 0.16. There have been made significant changes to the path creation. Please refer to the documentation of the Path workbench in general or the tutorial like path walk-through!

FreeCAD also offers more advanced ways to generate G-code directly. This is often much more complicated than using automatic tools as we saw above, but has the advantage to let you fully control the output. This is usually not needed when using 3D printers, but becomes very important when dealing with CNC milling, as the machines are much more complex.

G-code path generation in FreeCAD is done with the Path Workbench. It features tools that generate full machine paths and others that generate only parts of a G-code project, that can then be assembled to form a whole milling operation.

Generating CNC milling paths is another subject that is much too vast to fit in this manual, so we are going to show how to build a simple Path project, without caring much about most of the details of real CNC machining.


 * Load the file containing our lego piece, and switch to the Path Workbench.
 * Since the final piece doesn't contain anymore a rectangular top face, hide the final lego piece, and show the first cubic pad that we did, which has a rectangular top face.
 * Select the top face and press the [[Image:Path_FaceProfile.png|16px]] Face Profile button.
 * Set its Offset property to 1mm.




 * Then, let's duplicate this first loop a couple of times, so the tool will carve out the whole block. Select the FaceProfile path, and press the [[Image:Path_Array.png|16px]] Array button.
 * Set the Copies property of the array to 8, and its Offset to -2mm in the Z direction, and move the placement of the array by 2mm in the Z direction, so the cutting will start a bit above the pad, and include the height of the dots too.




 * Now we have defined a path that, when followed by the milling machine, will carve a rectangular volume out of a block of material. We now need to carve out the space between the dots, in order to reveal them. Hide the Pad, and show the final piece again, so we can select the face that lies between the dots.
 * Select the top face, and press the [[Image:Path_FacePocket.png|16px]] Face Pocket button. Set the Offset property to 1mm, and the retraction height to 20mm. That is the height to where the cutter will travel when switching from one loop to another. Otherwise, the cutter might cut right through one of our dots:




 * Once again, make an array. Select the FacePocket object, and press the [[Image:Path_Array.png|16px]] Array button. Set the Copies number to 1 and the offset to -2mm in the Z direction. Move the placement of the array by 2mm in the Z direction. Our two operations are now done:




 * Now all that is left to do is to join these two operations into one. This can be done with a Path Compound or a Path Project. Since we will need nothing more and will be ready to export already, we will use the project. Press the [[Image:Path_Project.png|16px]] Project button.
 * Set the Use Placements property of the project is to True, because we changed the placement of the arrays, and we want that to be taken into account in the project.
 * In the tree view, drag and drop the two arrays into the project. You can reorder the arrays inside the project if needed, by double-clicking it.
 * The project can now be exported to G-code, by selecting it, choosing menu File -> Export, selecting the G-code format, and in the pop-up dialog that will open, selecting a post-processing script according to your machine.

There are many applications available to simulate the real cutting, one of them that is also multi-platform and open source, like FreeCAD, is Camotics.

Downloads


 * The STL file generated in this exercise: https://github.com/yorikvanhavre/FreeCAD-manual/blob/master/files/lego.stl
 * The file generated during this exercise: https://github.com/yorikvanhavre/FreeCAD-manual/blob/master/files/path.FCStd
 * The G-code file generated in this exercise: https://github.com/yorikvanhavre/FreeCAD-manual/blob/master/files/lego.gcode

Read more


 * The Mesh Workbench
 * The STL file format
 * Slic3r
 * Cura
 * The Cura Workbench
 * The Path Workbench
 * Camotics