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Odd behavior when untrimming an extruded arc

Posted: Fri Jul 07, 2023 1:50 pm
by ryan-feeley
Thought I'd share this to see if anyone else has seen similar oddities with untrim. This was created in Swx2020, but I've confirmed Swx2022 has the same behavior.

If I have an arc sketched on the top plane, sketched left-to-right such that the first arc endpoint is to the left and the 2nd is to the right, and extrude it as a surface in the +Y direction, it will untrim just fine

If instead I extrude it in the -Y direction, only half of the surface will untrim.

If I reverse the sketching direction, such that the first arc end point is to the right, and again extrude it as a surface in the -Y direction, it won't untrim at all.

I expect untrim to do better and worse at times with tolerant NURBS geometry. But I was very surprised that it can't reliably handle a simple analytic (cylindrical) surface. Can anyone venture a guess as to why? I'm curious if this is a solidworks issue or a parasolid kernel issue.
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Re: Odd behavior when untrimming an extruded arc

Posted: Fri Jul 07, 2023 2:20 pm
by JSculley
Might be described in this KB article:

Article ID : SPR1240822
Abstract : Parts, Surface - Trim, Untrim: Untrim - It is not possible to untrim a cylinder due to the position and direction of a cut extrude feature

Link : https://support.3ds.com/knowledge-base/ ... SPR1240822

Listed as implemented in 2024 b1.

Re: Odd behavior when untrimming an extruded arc

Posted: Tue Jul 11, 2023 1:55 am
by ryan-feeley
Thanks @JSculley! Based on the title that looks like exactly the same sort of root cause.

I couldn't make the `support.3ds.com` knowledgebase link work. Sadly it came up "search yielded no results".
3ds knowledgebase comes up empty.png

Re: Odd behavior when untrimming an extruded arc

Posted: Tue Jul 11, 2023 9:32 am
by JSculley
ryan-feeley wrote: Tue Jul 11, 2023 1:55 am Thanks @JSculley! Based on the title that looks like exactly the same sort of root cause.

I couldn't make the `support.3ds.com` knowledgebase link work. Sadly it came up "search yielded no results".

3ds knowledgebase comes up empty.png
This is the entirety of the report:
image.png
So, not much help but if it is the same issue, the 2024 Beta has begun and you could download it and check it out.

Re: Odd behavior when untrimming an extruded arc

Posted: Tue Jul 11, 2023 7:18 pm
by ryan-feeley
Thanks! I reset my password with 3ds, and now the link works. Not sure if it was a password issue, or if they had server-side issues yesterday. I will experiment with the 2024 Beta.

Re: Odd behavior when untrimming an extruded arc

Posted: Wed Jul 12, 2023 10:48 am
by zxys001
ryan-feeley wrote: Fri Jul 07, 2023 1:50 pm

Hello Ryan... BUG! thanks for sharing this..., it's something I've seen for years, it's not uncommon with either nurbs or analytical arc untrims.
yeah, the only difference is the +Y extrude directions and this changes per plane? and if you export/import they still have issues, it Wierd! <()>