solid mesh cannot be convert to a solid

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noemurr
Posts: 1
Joined: Fri Jan 21, 2022 12:20 pm

solid mesh cannot be convert to a solid

Post by noemurr »

Hi all,

I'm trying to modify a stl mesh. I did the following procedure:
  1. import the mesh
  • convert the shape to a body
  • convert the body to a solid
The problem is that during the last point I got this error: "Cannot convert mesh because Shape is not a shell".

So I selected the mesh and in the mesh design workbench I checked with analyze -> "check solid mesh" and the result is a dialog telling me that the mesh IS a solid..

I don't get where in the process the mesh is damaged and how to solve the problem.
drmacro
Veteran
Posts: 8870
Joined: Sun Mar 02, 2014 4:35 pm

Re: solid mesh cannot be convert to a solid

Post by drmacro »

noemurr wrote: Fri Jan 21, 2022 12:30 pm Hi all,

I'm trying to modify a stl mesh. I did the following procedure:
  1. import the mesh
Correct. Assuming the mesh has been verified using the Mesh workbench as a valid (manifold mesh).
  • convert the shape to a body
Probably correct. But, it's the Part workbench "Create shape from mesh".
Once this is done you can use the Part "Check geometry" (typically with BOP option ticked) to confirm a valid shape object was created.
  • convert the body to a solid
Probably correct. But, it's the Part workbench "Convert to solid".
Once this is done you can use the Part "Check geometry" (typically with BOP option ticked) to confirm a valid solid object was created.

Sorry, but using the right terms is important so we know we are all talking about the same thing. ;)

The problem is that during the last point I got this error: "Cannot convert mesh because Shape is not a shell".

So I selected the mesh and in the mesh design workbench I checked with analyze -> "check solid mesh" and the result is a dialog telling me that the mesh IS a solid..

I don't get where in the process the mesh is damaged and how to solve the problem.
You did an analyse. Did you use the repair?

It may be, that, like so many stl files the mesh is just junk.

You can attempt to repair it in a real mesh tools like Meshmixer or Blender. (THere are some tools for this in the FreeCAD Mesh woirkbench, but, their efficacy is limited.)

Most times, it's just easier to re-model the thing in FreeCAD using the stl as a guide.


Please follow the recommendations in the big pink banner and provide your FreeCAD info, as I show mine below. Many time the version of FreeCAD and platform can make a difference. For example different revisions have different issues and fixes. And, it would be helpful to provide the stl file as well.

OS: Debian GNU/Linux 10 (buster) (XFCE/lightdm-xsession)
Word size of FreeCAD: 64-bit
Version: 0.20.27089 (Git)
Build type: Release
Branch: master
Hash: ead1bce8e994358388fd6dd993f0c9b756ec0eac
Python version: 3.7.3
Qt version: 5.11.3
Coin version: 4.0.0a
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TheMarkster
Veteran
Posts: 5505
Joined: Thu Apr 05, 2018 1:53 am

Re: solid mesh cannot be convert to a solid

Post by TheMarkster »

In Mesh Design there is the tool to check the solid mesh, but another that does a more thorough test for self intersections and other defects. There are also cases where the mesh must be split by component before converting to BREP format.
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