Did you ever find a solution to your problem? I too have recently needed to convert my workflow for IGES and certain shapes are giving me issues when I convert to NURBs. For example, screw threading. The result is a bunch of pieces that are unstitched and I don't know of any fast ways of repairing it enough so that I can convert it to STEP in another program.

Basically I am looking for the optimal workflow of going from polygon modeling in Maya to creating STEP files for Solidworks so that the models can be machined.

Can anyone help with that?