Reply To: CONVERTING STL FILE IN TO SOLID

[peteroznewman]

I can open the file in the second link.

Have you tried to create a solid in Rhino?  You would do that by creating a surface at each circle on each of the six faces of the cube. That would normally make this into a solid, but it probably will not because there is a foldover defect in the surface near the center of the cube.

Use the Cutting Plane tool to review the surfaces near the center of the cube and repair the foldover defect so that you can create a solid body.