STEP Files

We have some trouble when sending STEP files for manufacturing.

When we export STEP from Rhino 7, they aren’t properly imported into AlphaCam (a CAM software our supplier uses). Especially are boreholes not recognized as boreholes.
We found a temporary solution, in that we can import the STEP file into SpaceClaim (3rd party software), and then export them as STEP again. These STEP files can be correctly imported into AlphaCAM, and boreholes are recognized as such.

I’ve attached examples of:

  • The original Rhino file.
  • The Rhino STEP exports, with all possible combinations of export options. They are written into the filename.
  • The SpaceClaim exported STEP files. (60.9 KB)

Is it possible to expose some more options in the STEP exporting menu, so the generated STEP files will be more like the ones from SpaceClaim?


Hello - thanks for the files, that is very helpful, I’ll see if that can be fixed.
RH-62880 Step export - tune up requested

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@aske As a first attempt, can you please check if this file works for you?

Thanks.rhino_example.stp (15.3 KB)

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Hey Chuck,

Thank you so much for the fast response!
It didn’t work unfortunately.

The feedback I got from our manufacturer who tried importing the example STEP files and the one you send was:

  • None of them work.
  • Some are invalid step files in some way.
  • rhino_example_split_closed.stp has these funky issues:
  • In general it appears to be an issue that the sides of the cylinders of the bore holes are split into 2 surfaces. This appears to happen for files that have been exported with and without Split Closed Surfaces.
  • Not all SpaceClaim files appear to work correctly either :neutral_face:

(Sorry the feedback is not higher quality. The manufacturers aren’t the best communicators…)

I’ve contacted the makers of AlphaCam to get information regarding what their exact requirements to STEP files are, and what’s wrong with the example STEP files. Hopefully they’ll get back to or jump into the discussion here.


Hi Aske. Thank you for the detailed response. I am aware of at least one problem with V7 export of inverted cylindrical surfaces. It thought I had fixed it in the example I sent, but on further inspection, I see I only did for one of the two cylinders.

The first question I should have asked was if the export from V6 works. The inverted cylinder problem is not there, but the cylinders are represented as rational_bspline_surface entities rather than cylindrical_surface entities in the step file. rhino_exampleV6.stp (18.8 KB)

Another possible problem may come from the seam edges of the cylinders. If you show all edges in your Rhino model, you can see that the cylinders have a vertical seam edge. This edge goes into the step file. Some applications do not include that edge for special surfaces like cylinders. The step importer for an application that doesn’t want the seams should be able to figure it out, but maybe not in this case.

Since you have to send files elsewhere to test any changes that I make, I’ll try to limit the number of tests we need to do in order to figure this out. It may be best to switch the conversation to email. If this is OK with you, please contact me at

Thanks again.

Hi Chuck.

I send you, and the other AlphaCam team an email now.

We’ll talk there instead.

Thanks. I’m looking at it now.

RH-62880 is fixed in the latest Rhino 7 Service Release Candidate

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