STEP File import error when contain revolve for spherical objects.

[MartenKL]

Description of the bug

When importing STEP-File into Prusa Slicer it missas part of a revolve that is a sphere. Happens in all models I have done where part of a circle meets rotation axis perpendicularly. To exclude export errors from SolidWorks I also imported the STEP-file into 3ds Max 2024.

[PolishingBall.zip](https://github.com/prusa3d/PrusaSlicer/files/14480821/PolishingBall.zip)

Project file & How to reproduce

1. File/Import/Import STL...
2. Select STEP-file with revolve

Checklist of files included above

• Project file
• Screenshot

Version of PrusaSlicer

2.7.2

Operating system

Windows 11

Printer model

Prusa i3 MK4

[MartenKL]

If the end of the circle does not end perpendicular to axis this problem disappears. Like adding a small 45 degree (90 revolved) point or "bevel" the corner in the sketch between the axis line and the circle.

[u89djt]

I'm having trouble with STEP files sometimes too, but I've just found that importing your step file into Fusion 360 and re-exporting as STEP seems to introduce changes to the data that allow the slicer to work with it. Re-importing and exporting as STEP files this way has worked on a couple of my own original STEP exports that haven't previously imported to prusaslicer successfully, too.
Here's your PolishingBall step file after importing to- then immediately exporting from Fusion 360. This imports to prusaslicer 2.7.2 successfully for me under windows 10 giving the included 3mf file:
2ndgenpolishing.zip

Note that there are errors in the mesh built by the slicer that aren't visually apparent, and that slicing succeeds despite these.
I haven't attempted to find an explanation for any of this.
There might be a clue in the fact that (in your original) the whole sphere is subtracted, leaving a concave cup: