Hi, I made several experiment and you are right the file exported from Moi has other objects, the best way to get a clean file is exporting into sat format and import again into empty scene and export the new one into igs. but if your application doesn't support trimmed surfaces you get the same visualization problem as the screenshot below of my test done with gCAD3D and PolyCAD, i used other application but is hard get a file correct, the best way is making it by network curves in the holed faces.