Surface artifacts with imported .stp files

I’m working on automotive racing wheels for a client. Part of the process involves exporting .stp files so they can be imported into AutoCad for FEA testing. Once imported into AutoCad, they must be made into a mesh model. Creating the mesh model fails. AutoCad Tech suspected artifacts in the model being the reason. (They can’t import any mesh model that I create), by the way.)

If I import the .stp model I create in Rhino 6, I can see artifacts in the surface. I’ve tried exporting the Rhino model with every combination of .stp export options, with no change.

This is the response from AutoCad:

“So at first glance they think there’s an issue with the geometry, even though Inspect-Validate doesn’t show any geometry issues. There an funky looking artifact here that could be causing the Brep regularization process to hang, and we don’t even get to the meshing process. Also, I see that Symmetry is already been considered since it’s only the inner (or outer) half. In this case, we may be able to use 1/4 or 1/8 of the model. We have symmetry guidelines in the OLH. The child page for symmetry types explains more detail.” (

I don’t know what they’re talking about. It’s above my pay grade.

Importing the .stp file that I made back into Rhino, I do indeed see surface anomalies.:

What is the problem? What can I do to fix this?



can you please just post that file or a portion of it. it will be far less complicated.

I think is mainly a creases problem for revolving filleted curves. if you run DivideAlongCreases withSplitAtTangents=Yes. should solve those problems

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Seems possible, as having internal G1 joints can even cause problems with meshing in Rhino.

I checked “Split at Tangents” before revolving the section, created the model, and sent it to engineer that does the FEA testing. He was able to make a mesh with ease.

Thank you very much.