Preserve Solid between import from and export to step

I’ve got several step files from various CAM systems which contain solids.
After importing those into Rhino (V5) and exporting again as step, some of the solids decay to shells.
Most likely, this happens because the faces involved don’t describe a solid as Rhino would expect a well described one (they may have gaps, self intersections and other problems).
Other CAD Systems are capable of preserving these attributes, e.g. store and handle (as good as possible) these geometries as solids and preserve the solidness.
Is there an option in Rhino 5, or a new Rhino version, which can handle such non-conforming solid descriptions?

Maybe I’m wrong but I don’t think that is possible since the STEP conversion involves a translation between cad kernels which is how each software understand the shapes. For example a cylinder, in one software can be an extrusion of a cyrcle, in other, a straigh line revolved.
most of the cad programs have some tools to repare models imported, but those issues will always exists I guess.
Inside Rhino can be a bit tricky and mainly a manual work since is a surface modeler and it doesn’t have, as far as I know, geometry restrictions to keep the surfaces connected as others direct modeling softwares have.

Yeah, i fear that the Rhino kernel does not distinguish between expressed intentions, like, this should be a solid, and constraints inherent to its kernel, e.g. if these are not satisfied, it cannot be a solid at all, because this would add a significant overhead in combinatorial states which is hard to track and might give little benefit for Rhino. I’m asking this question because we’re evaluating Rhino as a replacement for our current CAD landscape, which is quite diverse, and because one of our CAM library suppliers seems to use Rhino as the scripted test environment of their choice.

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