Maybe this is just the deficiency of a small sheet metal unfolding algorithm.

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Zhyong Quan
Posts: 7
Joined: Sun Feb 11, 2024 3:31 am

Maybe this is just the deficiency of a small sheet metal unfolding algorithm.

Post by Zhyong Quan »

Hello, all veterans

Just now, I modeled a right-angle elbow. When I was studying unfolding this model on SheetMetal WB, I found that the generated metal patches and sketches looked a little strange.
  • Each patch had two extra things that looked like datum-planes, and isolated vertexes.
  • The curved edge side of the patch is also broken. The projections of their upper and lower edges are not coincident.
  • The transformed sketches are wrong.
Is it the result that I didn't use any of SM's commands?
strange faces in sheetmetal parts.png
strange faces in sheetmetal parts.png (18.53 KiB) Viewed 215 times
Thanks

Attachment:
RightAngleElbow-Sheetmetal.FCStd
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Code: Select all

OS: KDE Flatpak runtime (pop:GNOME/pop)
Word size of FreeCAD: 64-bit
Version: 0.21.2.33771 (Git)
Build type: Release
Branch: (HEAD detached at b9bfa5c)
Hash: b9bfa5c5507506e4515816414cd27f4851d00489
Python 3.11.7, Qt 5.15.10, Coin 4.0.0, Vtk 8.2.0, OCC 7.6.3
Locale: Chinese/China (zh_CN)
Installed mods: 
  * Assembly4 0.50.6
  * SheetMetal 0.4.0
  * Reporting
  * FastenersWB 0.4.75
Workshop_Notes
Posts: 543
Joined: Wed Sep 29, 2021 8:35 am

Re: Maybe this is just the deficiency of a small sheet metal unfolding algorithm.

Post by Workshop_Notes »

I think Sheetmetal only unfolds planar (flat) faces. The faces in your model are curved, which might be why you are seeing a problem.

You can unwrap them by making a Facebinder and then unwrapping in the Mesh Workbench.

See this video:

https://www.youtube.com/watch?v=nNPI8HEzu6g

https://wiki.freecad.org/Draft_Facebinder

https://wiki.freecad.org/MeshPart_CreateFlatFace

I think if you want a really accurate development of your sheet metal part, you'd need to unwrap it at mid-thickness of the metal. Try with the inside and the outside, overlay the two developments and see if the difference is significant.
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