The FreeCAD interface

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 apart, 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 occured.

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 also usually find many others in your own city. In all major cities, you will also 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 configurating 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

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 sketc (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 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 reimported into FreeCAD (using the slic3r preprocessor) for checking.

Generating G-code

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 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 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 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 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 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 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-procesing 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: http://www.freecadweb.org/wiki/index.php?title=Mesh_Module

The STL file format: https://en.wikipedia.org/wiki/STL_%28file_format%29

Slic3r: http://slic3r.org/

Cura: https://ultimaker.com/en/products/cura-software

The Cura Workbench: https://github.com/cblt2l/FreeCAD-CuraEngine-Plugin

The Path Workbench: http://www.freecadweb.org/wiki/index.php?title=Path_Workbench

Camotics: http://camotics.org/

Generating 2D drawings

When your model cannot be printed or milled directly by a machine, for example it is too big (a building) or it requires manual assembly after the pieces are ready, you will usually need to explain to another person how to do that. In technical fields (engineering, architecture, etc), this is usually done with drawings, that are handed over to the person responsible for assembling the final product, that will explain how to do it.

Typical examples are Ikea instructions, architectural drawings or blueprints. These drawings usually contain not only the drawing itself, but also many annotations, such as texts, dimensions, numbers, symbols that will help other people to understand what needs to be done and how.

In FreeCAD, the workbench responsible for making such drawings is the Drawing Workbench.

The Drawing Workbench allows you to create sheets, which can be blank or use a pre-made template to already have a series of items on the sheet, such as borders and title. On these sheets, you can then place views of the 3D objects you modeled previously, and configure how these views must appear on the sheet. Finally, thanks to an addon called Drawing Dimensioning Workbench, you can also place all kinds of annotations on the sheet, such as dimensions, texts, and other usual symbols commonly used in technical drawings.

Drawing sheets, once complete, can be printed or exported as SVG, PDF or DXF files.

In the following exercise, we will see how to create a simple drawing of a chair model found in the FreeCAD library (Furniture -> Chairs -> IkeaChair). The FreeCAD library can easily be added to your FreeCAD installation (refer to the installing chapter of this manual), or you can simply download the model from the library webpage, or via the direct link provided at the bottom of this chapter.

Load the IkeaChair file from the library. You can choose between the .FCStd version, which will load the full modeling history, or the .step version, which will create only one object, without the history. Since we won't need to model any further now, it is best to choose the .step version, as it will be easier to manipulate.

Switch to the Drawing Workbench

Press the little arrow next to the New Drawing Page button.

Select the A4 Portrait / ISO7200 template. A new tab will open in your FreeCAD window, showing the new page.

In the tree view (or in the model tab), select the chair model.

Press the Insert view button.

A View object will be created on our page. Give the view the following properties:

X: 100

Y: 150

Scale: 0.1

Rotation: 270

We now have a nice top view (which is the default projection) of our chair:

Let's repeat the operation twice, to create two more views. We will set their X and Y values, which indicate the position of the view on the page, in order to show them apart from the top view, and their direction, to create different view orientations. Give each new view the following properties:

View001 (front view): X: 100, Y: 130, Scale: 0.1, Rotation: 90, Direction: (-1,0,0)

View002 (side view): X: 180, Y: 130, Scale: 0.1, Rotation: 90, Direction: (0,-1,0)

After that, we obtain the following page:

We can tweak a bit the aspect of our views if we want, for example we can raise their Line Width property to 0.5.

We will now place dimensions and indications on our drawing. There are two ways to add dimensions to a model, one is placing the dimensions inside the 3D model, using the Dimension tool of the Draft Workbench, and then place a view of these dimensions on our sheet with the Draft View tool (which can be used with a single dimension or a group containing dimensions), or we can do things directly on the Drawing sheet, using the Drawing Dimensioning Workbench, which is installable from the FreeCAD addons. We will use here this latter method.

Switch to the Drawing Dimensioning Workbench

Press the Add Linear Dimension button. Available nodes are highlighted in green on the drawing page:

Click two of these points, then click a third point to place the dimension line:

The Linear Dimension tool, as most of the other Drawing Dimensioning tools, will not exit after you finished, allowing you to place more dimensions. When you are done, simply click the Close button in the Task panel.

Repeat the operation, until all the dimensions you wish to indicate are placed. Take a minute to browse through the different options proposed in the Linear Dimension's task panel. For example, by unticking the auto place text option, you will be able to place the text of the dimension elsewhere, like on the image below:

We will now place two indications, using the Welding/Groove symbols tool, selecting the default one (no groove symbol). Draw the two lines like on the image above.

Now place two texts using the Add text tool, and change their text property to the contents of your likings.

Our drawing is now complete, all that is left to do is to fill in the informations of the sheet titleblock. With most of the default FreeCAD templates, this can be done easily, by changing the Editable Texts property of the page.

Our page can now be exported to SVG to be worked further in graphical applications like inkscape, or to DXF by selecting menu File -> Export. The Drawing Dimensioning workbench also features its own DXF export tool, which also supports the annotations added with that workbench. The DXF format is importable in almost all existing 2D CAD applications. Drawing pages can also be directly printed or exported to PDF.

Downloads

The chair model: https://github.com/FreeCAD/FreeCAD-library/blob/master/Furniture/Chairs/IkeaLikeChair.step

The file created during this exercise: https://github.com/yorikvanhavre/FreeCAD-manual/blob/master/files/drawing.FCStd