Too long time to create a Gmsh

About the development of the FEM module/workbench.

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cgf
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Joined: Sun Mar 21, 2021 4:19 pm

Too long time to create a Gmsh

Post by cgf »

Hello,

Is it normal a Gmsh take more than 24 hours to be generated? The concerned part is small and (I think) the element sizes are proporcional to the whole part size (there is a mesh region with limited size, the rest is left to automatic), but has one section that is a M8 threaded screw. FreeCAD is not frozen, as it is possible navigate though the other objects in the tree and the timer is still counting.

I don't know now if I should keep waiting, due to may be it is going to finish soon, as so long time has already passed, or halt it and start over with other parameters. There is no progress bar or something that indicates the estimated remaining time. May be it can be a good idea for development (I'm an engineer, not a programmer).

Is it possible to "estimate", based on the elements in a body (revolutions, pads, fillets, helix, etc.), how long a mesh creation will take. I mean...should I ever start a mesh creation in a screw again (I've never done it before and I think that this is what's taking too long)?

Thanks,
BR,
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bernd
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Re: Too long time to create a Gmsh

Post by bernd »

No for sure not. More than 5 minutes meshing time is not common even for bigger models. up to more than 100'000 elements.

You may post your part and we could have a look.

cheers bernd
cgf
Posts: 7
Joined: Sun Mar 21, 2021 4:19 pm

Re: Too long time to create a Gmsh

Post by cgf »

Hello bernd,

Thanks for the advice. Now I have a knowledge base of a reasonable time for a meshing job.
After I halted the meshing job, I have found out that this is more like a FreeCAD bug. I closed FreeCAD and started over the FEM analysis, then the same mesh was created in 7 seconds. Leaving the element size in automatic gave me a too coarse mesh so, I just changed the max size setting and clicked "Apply", then meshing creation reached more than one minute and nothing was shown. FreeCAD behavior was the same as before, with the active time counter and I was able to navigate through other objects in the tree, zoom in/out, etc. The mouse pointer also changed to the windows hourglass, but using its center, it was possible to save the model, close and open again. Then, with the same untouched model, I just clicked "Apply" again and the mesh was created in the same 7 seconds. The windows pointer didn't change from the hourglass just closing and opening the model. It was only gone by closing FreeCAD and opening it again.

BR,
cgf
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bernd
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Re: Too long time to create a Gmsh

Post by bernd »

Which version do you use? I assume 0.19?

You should get the latest 0.20 dev version. Lots of FEM bugs have been fixed already. You get if from here: https://github.com/FreeCAD/FreeCAD-Bund ... kly-builds
cgf
Posts: 7
Joined: Sun Mar 21, 2021 4:19 pm

Re: Too long time to create a Gmsh

Post by cgf »

0.19. Didn't know about the .20 version. I will migrate soon then! Thanks bernd!
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