As an occasional wood-turner, I'm sometimes asked to make wooden urns. I've got a workflow where I model these in FreeCAD in order to calculate the internal volume..
- Create or trace a b-spline curve in Inkscape for body outline to centre line
- Import SVG as geometry, transform to XZ plane, with bottom centre at 0,0
- Part->Revolve around Z axis to form shape for inner wall
- Draft->Clone the revolve, and then scale the cloned object to achieve required volume
(Can measure the volume using FCInfo macro, or in Python console - App.ActiveDocument.Clone.Shape.Volume) - Part->3D Offset (outwards) for required wall thickness
Wondering whether this is a bug, or whether there is something wrong with my process. Quite happy to do it another way if there is a better option, but do need to be able to easily change the scale and verify internal volume..
Attaching an example FreeCAD project to demonstrate the issue. The clone is currently scaled by the same factor in all axis, just change the Z axis scale and recompute the 3D offset to see the error.
Thanks in advance,
Jon.
OS: Fedora 33 (Workstation Edition) (GNOME/gnome)
Word size of FreeCAD: 64-bit
Version: 0.20.25157 (Git) AppImage
Build type: Release
Branch: master
Hash: 257cdd8f423f1530b8df6f53e242de629fee4e85
Python version: 3.9.5
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.5.2
Locale: English/United Kingdom (en_GB)