FEM and Blender

Introduction

Blender
- 3D print add-on (Check all)
- BFEX - Blender FEA Exporter https://github.com/MiguelDLM/BFEX
- Blendmsh https://github.com/senthurayyappan/blendmsh
- quad remesher https://www.youtube.com/watch?v=kfQfU_cDRWE
- Fix meshes https://github.com/evaherbst/Blender_remeshing_guide
Elmer https://www.elmerfem.org/blog/
FreeCAD
Gmsh https://gmsh.info/
Netgen https://ngsolve.org/
OpenFOAM https://www.openfoam.com/
Paraview https://www.paraview.org/
Salome
TetGen

Blender and CAD

TinyCAD https://docs.blender.org/manual/en/4.1//addons/mesh/tinycad.html
CadSketcher https://www.cadsketcher.com/
Parts list
- Using a script: Selected parts only, and don't apply rotations! https://github.com/kittengue-dot/Blender-Script-Export-Part-list https://www.youtube.com/watch?v=C1RZszKlojQ

import bpy
import csv

def export_selected_mesh_dimensions_to_csv(filepath):
    """Export Parts
    Args:
        filepath (str): Le chemin du fichier CSV de sortie.
    """

    with open(filepath, 'w', newline='', encoding='utf-8') as csvfile:
        fieldnames = ['Part', 'Section X (mm)', 'Section Y (mm)', 'Length Z (mm)']
        writer = csv.DictWriter(csvfile, fieldnames=fieldnames)

        writer.writeheader()
        for obj in bpy.context.selected_objects:
            if obj.type == 'MESH':
                
                dimensions = obj.dimensions
                x = [0,0,0]
                x[0] = round(dimensions.x * 1000, 3)
                x[1] = round(dimensions.y * 1000, 3)
                x[2] = round(dimensions.z * 1000, 3)
                x.sort()

                writer.writerow({'Part': obj.name, 'X (mm)': x[0], 'Y (mm)': x[1], 'Z (mm)': x[2]})

filepath = "/home/user/Downloads/part_list.csv"  # Replace destination path

export_selected_mesh_dimensions_to_csv(filepath)

FreeCAD import

Steps:

Export in Blender
- Use Boolean
- Eliminate the bolts and some holes
Part -> Create shape from mesh
Part -> MakeSolid

Some problems (see a Part check Geometry)

Geometry is a shell -- not a solid: a shell mesh on meshing
- Check this by right clicking on the mesh and printing mesh informations (Tasks: Node count vs Triangle count vs Tetrahedron count)
Self intersections
- Use Boolean in Blender for all parts (both, if two are overlapping)
- Self intersecting meshes are considered dirty
- Use Part -> View -> Transparency to see the intersection points, if they persist.
- eg Netfabb cleans

Workflow and test examples

Make the Blender mesh and export as .obj file
Make the mesh using GMSH or FreeCAD, and use FreeCAD to FEM calculations

Simple Cube

Works OK with the FreeCAD, not with the Gmsh

The imported cube has double nodes, and the color is strange.
It works flawless in the FreeCAD.
The FreeCAD FEM solver gives some results.
However, when importing to GMSH, it will produce an error.
If the cube is exported as STL, then GMSH will work better.
The mesh generation does not work: "PLC Error: A segment and a facet intersect at point" and "Invalid boundary mesh (segment-facet intersection) on surface 1, intersection (0.333327,0.333327,1)".