I frequently export flat SU views as DXF files for CNC work (plasma, waterjet, laser etc.) For certain objects, I am thwarted by by the facets SU uses to create curves and circles. Is there a plugin that will export a DXF and, translate the facets into a smooth curve or circle?

Currently I have to pay fabricators with CAD software to redraw my SU generated DXF files. Alternately is there an easy non-SU converter software to do this?