STEP Exports from Rhino vs Inventor

Hello! From the past couple of weeks there is an issue ive been trying to solve. I work in a manufacturing company which uses STEP files to manufacture aluminium components. The usual workflow is to use Autodesk Inventor to model the components and export STEP files from that which is then loaded to the CAM software (Unilink).

Recently we had a project which required some complex geometry which I thought is more easily modelled using a Rhino/Grasshopper. For some reason the CAM software does not seem to gather the data from the STEP files exported from Rhino. Simple orthogonal cuts are detected, but anything which has a hole or angular cuts doesnt seem to be recognized.

We contacted Unilink and they suggest using inventor. Does anyone have any clue what could be the issue? Are there difference in how the data is structured when expporting step files in inventor as compared to rhino which seems to be causing this issue?

Maybe you can provide a STEP file of some simple part modeled in Inventor (that has a hole or a cut as you mentioned) and the same part modeled in Rhino so that someone can look at the differences?

Thanks for the reply.
Following is are two step files containing a simple extrusion profile with holes, modelled in inventor and rhino.

The holes are recognized when using the step file from inventor but not from rhino.

3332078_TI_E02(RHINO).stp (741.6 KB)
3332078_TI_E02(INVENTOR).stp (243.6 KB)

What I see is this:
The Rhino exported hole surfaces are split in half (which used to be the preferred way IIRC), and are “rational NURBS surfaces”, whereas the Inventor-exported holes are full cylinders and show up as a “surfaces of revolution”.

You can fix both of those when exporting by hitting the “Options” button in the Export dialog and choosing the STEP file type, and unchecking “Split closed surfaces” (checked by default):


I opened the Inventor export in Rhino and re-exported with the split closed surfaces option unchecked. It is below - does this work for you to get the holes recognized?

TestReExport.stp (291.8 KB)

The object color in the Inventor exported file is orange, the Rhino is gray, I don’t know why that is, normally color is kept via STEP.


@Helvetosaur Yes this seems to work. Do you think the same would work for the model made in rhino ?

I don’t see why not, I did export that one from Rhino…

I remade the extrusion using the side profile and re-cut the holes in Rhino. Thus it is a 100% Rhino made object. I reexported that as STEP. Is this one OK?
TestReBuildReExport.stp (360.1 KB)
TestReBuildRhino3dm.3dm (2.5 MB)

@Helvetosaur Yes. This seems to work. So I managed to rebuilt it myself with the holes and it seems to be working for sure! Thanks for that. But I also need some stepped angular cuts in the profile. When I did that, the software again recognizes it as just linear cuts. Do you know what could be the issue this time ?
Testwithcuts.3dm (7.0 MB)

This is how it shows up in the CAM software.

That is very odd… I don’t know what might be going on there. Looks like it might not like trimmed surfaces. What CAM software are you using? Do you have the same part made in Inventor that you can post as a STEP so we might be able to try and detect some differences?

Yes indeed, its a bit strange.
We are using this software called Unilink. Uni_Link |

I unfortunately do not have the same part modelled in inventor. Also I do not have inventor on my machine to give this a try, Ill have to bother my colleagues for this. Let me try to find a file with a step cut which we can remodel and check.

Thanks again for all the help!


Any machine – any software

We are compatible with all machines and all construction software.

What you see is really what you get. In 3D.

Well, maybe they need to revise that a bit… I would have them try to explain why their software doesn’t import Rhino-generated STEP files correctly, rather than they suggesting you use some other software…

Uni_Link makes manufacturing of designs from ANY construction software on ANY machine as easy as printing a document from a PC

Make them live up to that slogan.

@Helvetosaur So. I modelled a step cut profile from Rhino and Inventor and tried to read the file in the software and both the inventor export and rhino export had issues. So it has nothing to do with the Rhino export specifically, the software has issues in reading angular cuts in general. So we have to take it up with the software company itself.