Freecad

FreeCAD’s PartDesign workbench is the closest equivalent to SolidWorks’ Part environment. It uses a feature-based, parametric modeling approach built on OpenCASCADE Technology (OCCT) — the same geometry kernel that powers CATIA and Salome. If you’re coming from SolidWorks, Inventor, or any history-based modeler, you’ll recognize the concepts but encounter a few structural differences that aren’t obvious from the UI. This guide covers what actually matters for getting productive: the Body container model, how the Sketcher’s constraint system differs from what you’re used to, the core PartDesign features and their underlying OCCT operations, the topological naming problem that plagued earlier versions (and the fix in FreeCAD 1.0), and how to export finished geometry to STEP, DXF, and STL using FreeCAD’s import/export pipeline. ...

“Failed to create empty document.” That error message from SolidWorks when opening a STEP file means the STEP importer could not even initialize a document container before hitting a fatal problem. It is not a timeout. It is not a permissions issue. The file has structural corruption that SolidWorks’s geometric kernel cannot work around. If you got this from a vendor file, a downloaded dataset, or a STEP that was partially written when something crashed, SolidWorks is not going to open it. The recovery path goes through a different STEP importer — one with a higher tolerance for malformed AP214 entity references — and then back into SolidWorks via Parasolid. ...

You click “Fillet,” pick an edge, type a radius, and hit the green check. The edge rounds off. Done. Until it isn’t. Until you get “Fillet operation failed” on a perfectly reasonable-looking edge. Or until the same 2mm radius works on one edge but blows up on the adjacent one. Or until your model rebuilds fine in SolidWorks but the same STEP file fillets differently in Inventor. These aren’t random bugs. They’re the predictable result of three completely different geometric kernels making three completely different decisions about how to roll a ball along an edge. We decompiled the DLLs, read the exported symbols, and walked through the open-source code to see what’s actually happening. ...

You click “Insert View” in FreeCAD’s TechDraw workbench, point it at a 3D part, and a few seconds later a clean 2D projection appears on the drawing page. Hidden lines are dashed, silhouettes follow curved surfaces, and section views show cross-hatched cut faces. It looks like the same thing SolidWorks does. And at a high level, it is — both systems solve the same fundamental problem: project a 3D solid onto a 2D plane, figure out which edges are visible, and draw the result. ...