PartDesign Groove Issue (Cont.)

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pschindler
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Joined: Mon Nov 28, 2022 2:33 pm

PartDesign Groove Issue (Cont.)

Post by pschindler »

Hi everyone,

I recently made a post on a PartDesign issue where a Groove feature failed. I used a very simplified model to illustrate my issue, which has successfully been resolved by following a suggestion from domad, see https://forum.freecadweb.org/viewtopic.php?p=644250. Thank you very much. The idea which resolved the issue was to change the rotation axis of a previous Revolution feature from "Horizontal sketch axis" to "Base Y axis", despite both options actually referring to the same axis.

Unfortunately in my actual (more involved) model, the suggested approach does not fix the issue. I created a similar (simplified) model to illustrate the problem. I want to remove the geometry marked in red using the "Groove C" feature. However, as soon as the groove angle in the feature is increased beyond a certain threshold, the groove is not correctly computed.

I would highly appreciate any tips on how to fix the issue, as well as to gain an understanding of what causes this problem to avoid this issue in my actual part. Thank you very much.

Code: Select all

OS: Ubuntu 22.04.1 LTS (ubuntu:GNOME/ubuntu)
Word size of FreeCAD: 64-bit
Version: 0.20.1.29410 (Git) AppImage
Build type: Release
Branch: (HEAD detached at 0.20.1)
Hash: f5d13554ecc7a456fb6e970568ae5c74ba727563
Python 3.10.5, Qt 5.15.4, Coin 4.0.0, Vtk 9.1.0, OCC 7.6.2
Locale: English/United States (en_US)
Attachments
SphericalGeometry2.FCStd
(85.78 KiB) Downloaded 48 times
Screenshot from 2022-11-28 22-42-25.png
Screenshot from 2022-11-28 22-42-25.png (209 KiB) Viewed 1624 times
edwilliams16
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Re: PartDesign Groove Issue (Cont.)

Post by edwilliams16 »

I couldn't get groove to work - a bug? A subtractive pipe works.
Screen Shot 2022-11-28 at 4.55.54 PM.png
Screen Shot 2022-11-28 at 4.55.54 PM.png (26.23 KiB) Viewed 1582 times
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SphericalGeometry2_EW.FCStd
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Shalmeneser
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Re: PartDesign Groove Issue (Cont.)

Post by Shalmeneser »

Something is rotten in the state of Denmark
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Capture d’écran 2022-11-29 173332.jpg
Capture d’écran 2022-11-29 173332.jpg (45.31 KiB) Viewed 1498 times
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freedman
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Re: PartDesign Groove Issue (Cont.)

Post by freedman »

I got it to work. The problem is Sketch(red) is starting on the same face it is cutting. If you change the Sketch(red) Attachment Offset Z position to anything positive (.000001) it will work. It could also be mapped to the face if your careful.

Win Ver. .21304

Edit: I also see the step increase of the groove in 10 degree increments, is that a setting??
pschindler
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Re: PartDesign Groove Issue (Cont.)

Post by pschindler »

freedman wrote: Tue Nov 29, 2022 8:05 pm I got it to work. The problem is Sketch(red) is starting on the same face it is cutting. If you change the Sketch(red) Attachment Offset Z position to anything positive (.000001) it will work. It could also be mapped to the face if your careful.

Win Ver. .21304

Edit: I also see the step increase of the groove in 10 degree increments, is that a setting??
Thank you for this suggestion! Changing the Attachment Offset Z indeed resolves the problem. Not sure if the explanation is correct though, also a "Rotary Offset" for the sketch would ensure that the sketch is not on the same plane the cut starts at, yet this does not fix it.

Regarding the step increase of the groove I did not change any specific setting.
pschindler
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Joined: Mon Nov 28, 2022 2:33 pm

Re: PartDesign Groove Issue (Cont.)

Post by pschindler »

edwilliams16 wrote: Tue Nov 29, 2022 2:57 am I couldn't get groove to work - a bug? A subtractive pipe works.
Screen Shot 2022-11-28 at 4.55.54 PM.png
The subtractive pipe also works for me. Thanks a lot, another tool at my disposal.
I also was not required to do the additional changes you did (extended and rotating the red sketch).

Would you say one should in general prefer the subtractive pipe to the groove feature?
Last edited by pschindler on Tue Nov 29, 2022 10:22 pm, edited 1 time in total.
edwilliams16
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Re: PartDesign Groove Issue (Cont.)

Post by edwilliams16 »

freedman wrote: Tue Nov 29, 2022 8:05 pm I got it to work. The problem is Sketch(red) is starting on the same face it is cutting. If you change the Sketch(red) Attachment Offset Z position to anything positive (.000001) it will work. It could also be mapped to the face if your careful.
It's not that simple. I had tried what I thought was more logical - rotating the sketch away from the face with an angle about the X-axis. That doesn't work. There's some problem with rotating sketches about their axes.
edwilliams16
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Re: PartDesign Groove Issue (Cont.)

Post by edwilliams16 »

There's clearly some numerical fragility here. If I create the red sketch at the origin and then place it position, it works.

I would normally use groove over pipe - why use the more complicated tool - but here it seems to get around some problem that is as yet not fully understood.
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freedman
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Re: PartDesign Groove Issue (Cont.)

Post by freedman »

If memory serves me, there is an offset (from origin) added to the sketch (something small like .0000000000001) for viewing. This doesn't explain pipe working instead of groove unless the groovy folks failed to calculate this into the code in some way.

EDIT: I think this was just for viewing.
Last edited by freedman on Wed Nov 30, 2022 4:56 pm, edited 1 time in total.
domad
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Re: PartDesign Groove Issue (Cont.)

Post by domad »

Greetings to the Community!
...during the testing phase of the question, I was able to detect the serious error ( :o ) of the "Groove" function of Part Design, it is shown in the animated gif.
Attachments
serious_subtractive_Groove_error.gif
serious_subtractive_Groove_error.gif (469.59 KiB) Viewed 1266 times
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