Subtract a bloc from a polygonnet

Hello NG,
I have a 3-dimensional structure as polygon net and can print it out with a 3D printer. Now I have to subtract 3 blocs out of this structure to create a space for electronics and a battery. And I plan to cut the structure in 3 pieces to have it printed out avoiding problems due to the cutouts.
I tried in many ways, but I failed because rhino handles the structure as if it would be empty and when I cut it in 3 pieces, I see only the “skin”, not a full structure. I’m trapped.
Thanks for any help!

Hi Chiara - please post a file with the objects, or if it is confidential, please send to and include a link back to this topic in your comments,