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Problem using boolean operation "cut" using a spiral over 360°

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Problem using boolean operation "cut" using a spiral over 360°

Posted by Jens F. Acker at April 29. 2018


I work on a parametric python script for Salome 8.4.0 which basically constructs a basic cylinder shape with filleted edges and cut spiraling grooves from it.

For that I construct a spiral line and a proper aligned circular face and sweep it along that line. Then I make a multi-copy from it and use that for the lower grooves object. After rotating and translating I get an upper groove and make a multi-copy to create an upper groove object.

So far so good.

Then I cut those grooves objects from the basic cylinder shape. Or try to do that at least...

As long as the spiral is under 360° all went well. But for over 360° there are some strange effects. Some of the grooves appear only as outlines, as if they would have been used for a partitioning, but the object stays as one solid! In Salome 8.3.0 it would produce an error with "no valid shape".

This problem disappears when the spiral is partitioned first with a plane object into smaller parts. The downside is an increase in the computation time for the later cut operation (it explodes!).

Is this an know error?

By the way:
I know that circular shapes can be modeled precise as rational B-splines. Is there a script, which creates an exact spiral curve given radius, pitch, start z-coordinate, end z-coordinate, and start angle?

Or is there even a script which creates full spiral objects using those informations together with a shape in XY-plane, which keeps the shape oriented correctly/as expected along the path?

This would be a useful tool to include into Salome directly. Fusion 360 from Autodesk started to include such a tool recently, too.

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