STEP export bug with mirrored solid

I exported two solids to .step. One face got “corrupted” when opening it with CAM software (alphacam and mastercam). Same problem is with ap 203 and 214, export settings.

Original solid is ok.
Mirrored Solid has corrupted surface.
Rhino 8 opens exported step correctly (no corruption).
If I export opened step again, step is fixed. (R8 → step → R8 → step)
I couldn’t replicate bug in rhino 7.

2 Solids.stp (2.0 MB)
2 Solids.3dm (927.6 KB)

Hi Henri -

Thanks, I’ve put this on the list for a closer look by the developer:
RH-78009 File IO: STEP export issue

Version 8 STEP export notices that the problem surface is a cylinder and exports it as such. The mirrored one has some combination of normal flipping that may be messing up the other importers. I’ll see if I can make it a little simpler for them and have you test it out. Thanks for the report.

@WinterSun I found a bug in our exporter that made that surface have flipped normals. Our importer knows how to deal with that and fixed it. That’s why reopening in Rhino fixed the file for you. Here is the STEP file created directly form your 3dm, with my fix. Does your CAM software approve? The fix should be in V8 SR2.
2 SolidsFixed.stp (2.0 MB)