- import STL in FreeCad
- From the dropdown middle menu select “part”
- Part – create shape from mesh
- Select the new shape in the file browser on left
- Part – Cross section – XY 1.5mm for mine
- Select the cross section in file browser on left
- Export – Flattened SVG
If your cad file is in STEP or IGES format you can skip the “create shape from mesh” step by going straight to the “Part” menu and choosing “Import CAD”