This is an OpenSCAD source (.scad/plaintext) for easy generation of 3U "Eurorack" generic panel CAD (STL files for 3D printer, LASER cutter, W.H.Y.)
Use the customizer window to set various paremeters (panel width in HP, and so on)
I've only been meddling with OpenSCAD for about a week, so there may be errors, and are bound to be better ways to do things.
Freeware - if it breaks, or breaks something, all the pieces are yours.