STEP export quality / tolerance settings

[JulianGroeli]

Hi All,

Is there any way to verify tolerances/quality of an exported STEP file from Fusion? From what I understand STEP is a vector-like format so tolerances wouldn't apply, correct?

I'm having an issue where an elliptical part is importing and being machined with visible facets, and I'm thinking it'd due to my CNC shop's tolerance settings during import or toolpath creation, but I need a way to prove that my STEP file is good.

This is holding up an active project. Your help and ideas for how to debug are much appreciated.

[HughesTooling]

Can you export that part of your design and attach here, either as an f3d or stp. As long as it's a smooth surface in Fusion it will be smooth in the export to STP. An ellipse will be linearised  and maybe then smoothed with arcs by the CAM software and it sound like the tolerances they are using are not fine enough.

Mark

[JulianGroeli]

Thanks for confirming my understanding that the STEP format will preserve the smooth surface, and that this is most likely either an import problem or a toolpath tolerance problem. I suggested that they try doing a test 2D contour cut with the tolerances tightened up, so we'll see how that goes.

Sorry, I can't post the file since it's under NDA, but here's a zoomed in screenshot of what they're seeing on the CAM side. Looks like an import issue to me.

[TheCADWhisperer]

Can you create a simplified dummy file that exhibits the same behavior but does not have proprietary design geometry and attach here?

[JulianGroeli]

Update:

I'm working with two different CNC shops. I requested that the first one re-export the file as step and send it back to me, and when they did it re-imported back into Fusion without any faceting. They are going to try tightening up their tolerances, and I have good confidence that this should address the issue.

The second one was still having problems, and it seems like their CAM software, ONECNC, is having trouble importing the file. We tried STEP, IGES and Parasolid (via Solidworks), and all three imports had the same issues, it's likely the problem is on their end. We are contacting ONECNC and will update again once we get to a conclusion.

[JulianGroeli]

@TheCADWhisperer I started making a dummy file, and discovered what could be the issue in the 2nd file. I had two odd edges that I've now fixed and will re-export and see if that takes care of it. It looks like the odd edges were created after a "split face" feature, when offsetting a perpendicular face. The split edge didn't get extended when the perpendicular face was offset. See attached pic.

If this doesn't take care of it I'll finish the dummy file and post it.

Thanks for the suggestion!