I use electrical enclosures from Saginaw Controls.  They provide .stp, .igs, and ._xt translations, but none seem to provide a usable SolidWorks model.  I have the same problems with files from Hoffman and Hammond.  Does anyone have a good technique for dealing with these issues.  The files import, but SolidWorks import diagnostics is unable to repair to a usable solid, just surfaces, and I can't put holes in surfaces.