Not very attractive but powerful
I started the CAD assignment by testing FreeCAD. I was looking for an open source cad design tool alternative for a while. I have been using Fusion 360 until they changed there license policy. For some reason, I never had the opportunity to test FreeCAD.
For my final project, I will probably need a stepper motor. At this time I don’t know if I’ll need a NEMA 17 or a NEMA 23. Thus, I started designing a NEMA 17 stepper motor in FreeCAD.
After opening FreeCAD, I was surprised by all the sample project available. FreeCAD seems to have plenty of simulation environment which I didn’t expect to find. As FreeCAD is an open source alternative, lots of developers contribute to the project by either fixing bug or adding new feature. That’s why freecad is both flexible and difficult to pick up. I started a new empty project. I will need a stepper motor as a reference. Instead of finding a model on grabcad, I’ll try to design it on my own using FreeCAD and a caliper.
FreeCAD is very helpful to determine what’s next task. There is an important menu on the left of the GUI, this menu is where you find : - the navigation tree - the operation parameters - the task prediction - Sketch element & constraint
As all prismatic CAD tool, I started by creating a new sketch. First you have to select a sketch plane. In my case the XY Plane.
The FreeCAD sketch is a bit frustrating… First, the interface isn’t pretty or blue light friendly… I switched to dark theme later, that’s why there is gray screen capture as well. To switch to the dark theme, go to
But the more frustrating problem are the constraint ! It took me years to figure out how automatic constraint work.
Here is an example, I started to create a polyline.
But when you try to move one of these lines, you discover that they aren’t attach at all…
If you press Ctrl key while drawing a poly line, FreeCAD automatically generate the coincidence constraint on the poly line. Which isn’t so obvious… Then I manage to create a fully constrained polygon.
After a while I manage to master the symmetry tool, I created this sketch :
Once I managed to make the whole polygon symetric, I took some mesurment of the real stepper using my caliper.
Then I added the only useful dimensions to the sketch.
When the sketch was fully constraint I extruded the solid.
Tips : FreeCAD does a descent job indicating how many degrees of freedom your sketch have. It may get stuck with complicated sketch (including symmetry) but it is still pretty useful.
I managed to create the stepper. A few more sketches to drill attachment point, and we’re ready to export the model.
Note : I tried to change the appearance of the different part of the model, but you need to make multiple body to do that. I have only extruded the body using three extrusion…