Importing a (.STEP) file

I’ve a (.STEP) file that in other CAD packages shows it being a solid model. Once imported into Rhino it comes in as a block, which is no problem to explode, but then has a ton of naked edges. Am wondering if there are some tolerances that need to be adjusted to help keep the model as a solid polysurface? Am not seeing a difference between the results of the (.step) file being saved as either the 203 or 214 versions.


Hi Arthur - is the object joined into a polysurface but has open edges, or does it come in as all individual surfaces (after ExplodeBlock)?
Can you send us an example step file (smaller and simpler the better) to to my attention, with a link back to this topic in your comments.


Hello Pascal - thank you for responding. I’ve sent an email with a link to download the file to the email.


Hi Arthur - I got your file and I also see some naked edges - that is one complicated part - looks like output from GeoMagic, maybe? I will poke at it some more, but I suspect I’ll need to just put it on the pile for the developer.

@arthurys - some of the patches that show naked edges (they are untrimmed) appear to be genuinely wonky at the corners-

Fixing these is not too hard, but it would be interesting to know if the same file in your other apps show the same problems.

There is one missing face - very small - that is also easy to fix, but seems more likely to be a boo-boo on Rhino’s part - the face is small, ~.005" on an edge but the file tolerance is also very tight and would seem to allow this tiny face. I believe we read the file tolerance from the step file, but I do not know how that is originally set.

In any case, I have a closed up version which I will upload for you on our server, in case that helps.


I Imported the STEP file, changed the tolerance to 0.001mm (0.0002mm seemed silly), and Joined the surfaces into a closed, solid, polysurface.
Then Volume command worked fine.

I suspect when the STEP file was exported, they used a tighter tolerance value that it was originally modeled at. This is a pretty common problem.

The Volume command worked fine then.

@John_Brock - not sure we’re looking at the same file…

Hello All - it was my understanding that changing the tolerance in Rhino would only make a difference on new geometry? If I am understanding what you’re suggesting after importing the file, change the tolerance, explode it and then join back together?

Yes the file shows as solids in both Solidworks and Solidedge. This is from a 3D scan done with Artec and made “water tight” in their software Artec Studio.

Yes Geomagic Wrap was used to convert the mesh to BREP. I’ve tried this in Rhino by first duplicating the mesh then with quad-remeshing, then conversion to NURBS. This process is really close to being usable, the biggest missing feature in the ability to shrink wrap/project the converted quad-mesh to the original mesh. This would help it conform to the original data and thus holding it to be closer in detail once converted.

Hi Arthur -

I think John was looking at a different file. Yours does not benefit from that treatment…

I understand it turns up solid in the Solid* but I am wondering about the quality of the surfaces - the bits I looked at are pretty messy right at a couple of the corners and I think we read the surface data accurately.


Sorry, my bad…