How to Generate FEM Mesh Using Gmsh in FreeCAD

Generating a finite element mesh using Gmsh in FreeCAD allows you to convert solid CAD models into high-quality 1D, 2D, or 3D meshes suitable for numerical simulation. This article provides a clear, step-by-step guide to configuring the Gmsh binary path in FreeCAD, creating an analysis container, defining mesh sizing parameters, and generating the final mesh within the Finite Element Method (FEM) workbench.

Step 1: Configure Gmsh in FreeCAD

Before generating a mesh, FreeCAD needs to know where the Gmsh executable is located on your system:

  1. Download Gmsh from its official source if it was not bundled with your FreeCAD installation.
  2. Open FreeCAD and go to Edit > Preferences.
  3. Select the FEM tab in the sidebar.
  4. Go to the Gmsh sub-tab.
  5. In the Gmsh binary path field, browse to and select the gmsh executable file on your computer.
  6. Click Apply and then OK.

Step 2: Set Up the FEM Workbench

  1. Open the 3D part or assembly you wish to mesh.
  2. Switch to the FEM Workbench using the workbench dropdown selector in the top toolbar.
  3. Click the Analysis container button (represented by a yellow capital "A" icon) to create a new simulation environment in the tree view.

Step 3: Create the Gmsh Object

  1. Select the solid geometry you want to mesh from the tree view or the 3D viewport.
  2. Click the FEM mesh from shape by Gmsh icon in the toolbar, or navigate to Mesh > FEM mesh from shape by Gmsh in the menu.
  3. A Gmsh mesh dialog will open in the Tasks panel on the left, and a mesh object will be added inside your Analysis container.

Step 4: Configure Mesh Settings

In the Gmsh task panel, define the parameters for your mesh:

  • Element dimension: Choose From Shape (auto-detects 3D/2D), or explicitly force 3D, 2D, or 1D.
  • Max element size: Sets the upper bound for element edge lengths. Lower values create a finer, denser mesh.
  • Min element size: Sets the lower bound for element edge lengths, useful around curved surfaces or sharp features.
  • Mesh order: Choose between 1st Order (linear elements, faster solving) and 2nd Order (quadratic elements with mid-side nodes, higher mechanical simulation accuracy).
  • Algorithm: Select 2D and 3D meshing algorithms (e.g., Delaunay, Frontal) if default settings produce poor element quality.

Step 5: Generate and Verify the Mesh

  1. Click the Apply button in the task panel. FreeCAD runs Gmsh in the background, which generates the elements and logs progress in the FreeCAD Report View.
  2. Once the log indicates completion, click OK to close the task panel.
  3. In the Model tree view, select the original solid part and press the Spacebar to hide it. This reveals the generated FEM mesh for visual inspection.