STL to Solid - "Part object is not a shell" error

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arhabib
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STL to Solid - "Part object is not a shell" error

Postby arhabib » Mon May 19, 2014 1:58 am

Hi;
I am new to FreeCAD, trying to convert a 3D mesh in STL format to a solid to do cfd modeling.
First, I created a "part" and tried to convert it to a solid but came up with the following error message:
"Part object is not a shell."

Any help will be appreciated.
Thanks
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NormandC
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Re: STL to Solid - "Part object is not a shell" error

Postby NormandC » Mon May 19, 2014 3:31 am

Hello,

To convert a mesh object to a solid, here are the steps:
  1. Switch to the Part workbench
  2. Select the mesh, and go to the Part menu --> Create shape from mesh
  3. Click OK to the dialog
  4. Select the newly created shape
  5. Go to Part --> Convert to solid
  6. Select the newly created solid
  7. Go to Part --> Refine shape
The last step is not necessary, but it will clean the solid of most of its residual edges on planar and cylindrical surfaces.
arhabib
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Re: STL to Solid - "Part object is not a shell" error

Postby arhabib » Mon May 19, 2014 4:18 pm

Hi;
Thanks for your response.
This is exactly what I do, but still I get the
"cannot convert because shape is not a shell"
error message!
wmayer
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Re: STL to Solid - "Part object is not a shell" error

Postby wmayer » Mon May 19, 2014 4:38 pm

After you created the Part object enter this into the Python console:

Code: Select all

App.ActiveDocument.ActiveObject.Shape.ShapeType
What does it say then?
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NormandC
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Re: STL to Solid - "Part object is not a shell" error

Postby NormandC » Mon May 19, 2014 4:41 pm

Then it probably means that the mesh does not form a valid enclosed volume (shell).

Switch to the Mesh design workbench, select the mesh object then go to the menu Meshes --> Analyze --> Check solid mesh.

What does it tell you?

Also, can you attach the mesh so we can have a look at it?
arhabib
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Re: STL to Solid - "Part object is not a shell" error

Postby arhabib » Tue May 20, 2014 4:42 am

Hi again;
It says: "The mesh is not a solid."

Anyways, the STL file is attached.
FYI, this is a dinosaur!
Attachments
cryptocleidus.zip
(86.12 KiB) Downloaded 111 times
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NormandC
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Re: STL to Solid - "Part object is not a shell" error

Postby NormandC » Tue May 20, 2014 4:50 am

Then the mesh has holes or self-intersecting surfaces and thus cannot be made a solid.

The Mesh design workbench has analysis tools to evaluate a mesh, you could try it.
jmaustpc
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Re: STL to Solid - "Part object is not a shell" error

Postby jmaustpc » Tue May 20, 2014 6:47 am

The stl file has problems
meshanalyze.jpeg
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quick61
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Re: STL to Solid - "Part object is not a shell" error

Postby quick61 » Tue May 20, 2014 7:18 am

If you look at how the model was made, you'll see why it has problems. I converted it to a shape and them used transparency on it to reveal the fact that the fins were just "stuck into" the body. Not the way to model such a critter. Espicialy if you intend to do anything with it after it is modeled. You might be better off modeling a new one from scratch and doing it right.

Mark
Dino_bad.png
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jmaustpc
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Re: STL to Solid - "Part object is not a shell" error

Postby jmaustpc » Tue May 20, 2014 7:25 am

If he has them as separate "blobs" in some application somewhere...maybe a work around might be to export the body and fins as independent stl files, then "import" them into a single FreeCAD document as 5 separate stl files, convert them independently to solids and then use Part Boolean Fuse to make one solid?

A fuse of the stl file might work, but stl Booleans often give problematic results. So I would think you would be best to convert them to solid shapes first.