From FreeCAD Documentation
- Analyzing and repairing the mesh object, if needed, should be done before launching this command. Appropriate tools for this task are available in the Mesh Workbench.
- Select the mesh object.
- Select the Part → Create shape from mesh option from the menu.
- The Shape from mesh dialog opens.
- Optionally check the Sew shape checkbox and specify a tolerance:
- This option is usually not needed. It is meant for mesh objects that are not watertight and have small gaps between edges.
- If the option is selected a compound of shells, instead of a compound of faces, is created.
- The sewing operation may be computationally demanding.
- Press the OK button.
- A shape is created as a separate new object.
- Optionally turn this object into a solid with Part MakeSolid.
- Optionally use Part RefineShape on the final object.