I created a 50mmx50mmx50mm cube with a relatively large square hole (41mm side length) inside the cube using sketchup. The model is manifold and exported using stl. It imports fine in Simplify3D, and it scales and depicts correctly when imported. The hole in the middle gets removed when the model is prepared for printing, meaning that the gcode will draw a solid cube. Any insights into this would be appreciated. I tried several geometries (circular holes) without success.