Reinforcement mesh generation for 3D printing

lexitus · Post by **lexitus** » Sat Feb 19, 2022 5:58 pm

I was watching CNC Kitchen's video on reinforcing 3D printed parts by increasing the infill based on FEM simulations. Stefan uses Fusion 360 and Ansys in his video, but I wanted to see if I could get some similar results in FreeCAD.

Using the famous test hook. I had some difficulty finding a workflow, but here are my notes in case you also want to experiment with this. I ended up going via Paraview, credit to this thread which had most of the details I needed.

: 2022-02-19 18_42_14-FreeCAD 0.19.png (58.2 KiB) Viewed 1863 times

Create body, or import mesh and convert to solid in Part workbench
Switch to FEM workbench
Create FEM analysis container
Create material for part, e.g. PET
Add fixed constraint on some faces
Add force constraint on some other faces
Add mesh. Can be problematic, I found gmesh ok, but best to start with coarse mesh and see how it goes.
Open "SolverCcxTools"
Select "Static" and "Write .inp file"
Run Calculix

This should then produce a CCX results object. This can be interacted with to view displacement, strain and so on. ScalarClip shows a mesh that is something like what we want, but I couldn't find a way of exporting it. Happily the FEM results can also be exported to a .vtk file, which is understood by Paraview.

: 2022-02-19 18_46_20-FreeCAD 0.19.png (132.01 KiB) Viewed 1863 times

Import .vtk file into Paraview
Here we can visualize stress etc. as in Freecad. I based the reinforcement mesh on the von Mises stress, following Stefan.
Select "clip" filter, select clip type = scalar, choose a value and select invert. Select "apply"
Add "extract surface" extractor to remove internal geometry etc.
"Save data" allows export as stl

: 2022-02-19 18_47_50-ParaView 5.10.0.png (205.87 KiB) Viewed 1863 times

With this stl we can then modify the output of the slicer. In PrusaSlicer:

Import original mesh
Right-click, add modifier, load...
Choose saved output from Paraview. It should line up exactly with the existing mesh
Right-click on the modifier mesh and select the desired reinforcement infill level.

: 2022-02-19 18_48_33-_Untitled - PrusaSlicer-2.4.0 based on Slic3r.png (695.39 KiB) Viewed 1863 times

And we're done! PrusaSlicer handles the modifier mesh ok, although there are some weird bits of 100% infill where there are holes in the modifier mesh. Good enough to be usable though. Looking forward to trying this out with a real project