From FreeCAD Documentation
- Select the shape you want to analyze. For volume FEM this needs to be a solid or compsolid. A compsolid is necessary if your part is made from multiple materials. (A compsolid can be created with the BooleanFragments command.)
- Optionally edit the minimal and maximal element size (autodetection often creates meshes that are too coarse).
- Click the Apply button and wait for the generation of the mesh to complete.
- Close the task. You now should see a new FEMMeshGMSH object in your active analysis container.