'Adding' thickness to a polysurface. 3Dprint - MS Thesis - Urgent

Hey everyone,

For my thesis i need to give my polysurface a thickness of 20mm or 10mm both sides. It needs to be a solid. So i can slice it and 3D print it. However i cant seem to enable ‘Solid’ and ‘BothSides’ at the same time. Does anyone have a workaround? (It’s the first cube in the file)
Any help is much appreciated
Truncated Octahedron Small Cube.3dm (11.0 MB)

10mm each way would cause the resulting shape to self-intersect, which sometimes makes strange things happen. I was able to offset 9.9mm
The shape would not go solid possibly because the result of the offset did not have planar edge curves.
I was able to get an almost solid piece by adding planes and trimming on the top and bottom. The cube is slightly shorter now.

There were some holes left over that the OffsetSrf command couldn’t deal with, but I managed to export the mesh, and Bambu Slicer fixed the holes.
If I have indeed saved your these, I wouldn’t mind being mentioned in the “Acknowledgements” Section.

Happy modeling.
Truncated Octahedron Small Cube_Fat_.3dm (13.8 MB)