Export a model as *.stp file for metal processing - Unwrap not possible

Dear All,
I hope someone can help me here.

We are a lighting manufacture, often I’m doing part drawings that will be send as *.stp file to the metal processing company.

They tell me that my *.stp files are not usable to unwrap the model and for further handling, as they lose all the parts that are rounded or folded, they have to redraw all my drawings so that they can work with on the CNC Machines.

I thought then, I will unwrap in Rhino directly and send them the file as a *.dxf. Now they are telling me that the unwrapped result doesn’t show the bending line and the result doesn’t seem to be correct to work with.

My question: is there a way how I can save the model correctly as a *stp file so that they can work with it?

I have attached a picture of the result when they try to unwrap the model the violet part is fine but in the flat version the pink and yellow parts are just disappearing…

Hope someone can help me here?
would highly appreciate any help
Kind Regards

Hi Rachel,

I have had the same experience with my metalwork supplier over the last several years when importing Rhino STEP files to RADAN software for unfolding.

The only reliable solution I have found is to import the Rhino STEP file into Fusion, check it unfolds correctly using the Fusion Sheet Metal tools, and re-export through Fusion as STEP.

Somewhere in that process, the STEP becomes usable.



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@DavidWood can you send us a step file that does not work and the same one that does? (tech@mcneel.com, with a link back to this topic in your comments.)

@Camaieu - does this mean the stp files open in the target software with those objects missing? Can you send us an example? The simpler the better. (tech@mcneel.com, with a link back to this topic in your comments.)

This all sounds like maybe some entity type is not expected or recognized by the target software.


Hi Pascal,

I gave up trying to send STEP files directly from Rhino some time ago, so I’m not sure what files won’t work, but I’ll see what I can dig-out and send.

Occasionally a Rhino STEP file would unfold, but it was very unpredictable. Anything that had faces push/pulled was almost certain to fail.

Radan were not very helpful on their side. No issue with Fusion files however. I would be very happy to save the cost of a Fusion licence if it’s fixable! :smiley:



Like point-edited? I imagine sheet metal-feature-recognition tools have no clue what to do with that, even if it’s so slight it’s within tolerance of ‘flat’ or ‘round’…

For example, sub-selecting faces and adjusting the length of a flange.

Sometimes rebuilding the fillet would help, or manually rebuilding/lofting the surfaces at either end.

I kept running into issues even with very clean, unmodified parts…

@DavidWood thank you very much for your reply, and showing that there would be a way that works, but unfortunately I don’t have a Fusion license…

@pascal I just have sent you the files hope we find a way to fix it, would highly appreciate it


@Camaieu - just to make sure - you are sending the 3d part via STP format to the metal shop where in theory, their software will unfold the parts, is that correct? Or do they expect to get flattened parts from you?

@DavidWood - one thing to try, if you have not, is to export from Rhino via step schema AP 214 and not AP242. (Fusion writes 214)


@pascal Yes this is absolutely correct, they say normally (with stp files from other costumers) they have no problem to unfold parts from stp files.
It looks that is just my drawings causing problems.
(they don’t expect from me that I’m sending flattened parts)

Can you send me step,iges or parasolid?
You can ask your customer, what is the namn of software they unfold your step file.

Hi Pascal,

I’ve been using this work-around since R6, which was AP214 back then.