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FEM Workbench

The FEM (Finite Element Method) workbench provides a complete structural, thermal, fluid, and electromagnetic analysis workflow inside FreeCAD. It connects the geometry of a Part Design or Part model to external open-source solvers and then displays the results back on the original geometry.

What the FEM workbench is for

FEM answers: how does this part (or assembly) respond when forces, heat, pressure, or electric fields are applied to it?

Given a solid model, the FEM workflow lets you:

  1. Define materials — assign elastic modulus, density, Poisson ratio, thermal conductivity, and other physical properties.
  2. Apply boundary conditions — fix faces, apply forces, set temperatures, constrain displacements.
  3. Generate a mesh — divide the geometry into small elements (tetrahedra, hexahedra) so the solver can process it.
  4. Run a solver — CalculiX, Elmer, Mystran, or Z88 compute the field solution.
  5. Visualise results — stress, displacement, temperature, electric potential, and other fields are mapped back onto the mesh and displayed with colour scales.

Key concepts

The analysis container

Everything in an FEM study — materials, boundary conditions, mesh, solver, and results — lives inside an Analysis container (Fem::FemAnalysis). You can have multiple analyses in one document (e.g. a static analysis and a thermal analysis of the same part). Only the active analysis receives new objects.

Mesh

The mesh is the discrete representation of the geometry used by the solver. FreeCAD wraps two meshing engines:

  • Netgen — automatic tetrahedral mesher; simpler interface, built into the standard FreeCAD package.
  • Gmsh — more powerful; supports structured meshes, boundary layers, and physical groups. Requires Gmsh to be installed separately.

Mesh quality matters: too coarse a mesh misses stress concentrations; too fine a mesh is slow. Mesh refinement regions let you increase density only where needed.

Solvers and physics

Solver Physics supported
CalculiX Static structural, frequency (modal), buckling, thermo-mechanical, coupled/uncoupled heat transfer
Elmer Electrostatic, electromagnetic, magnetodynamics, heat, fluid flow (Navier-Stokes), deformation
Mystran Linear static structural (lightweight, fast)
Z88 Linear static structural

Each solver requires its own executable to be installed; FreeCAD only generates the input files and reads the output.

Boundary conditions

A boundary condition is an assignment of a known value (or relationship) to a geometric entity (face, edge, vertex):

  • Dirichlet condition — the value is fixed (e.g. a fixed displacement = 0, a fixed temperature = 20 °C).
  • Neumann condition — the flux or derivative is fixed (e.g. an applied force, a heat flux, a pressure).

Getting the boundary conditions right is the most important modelling step — they define what your simulation is actually computing.

Results and post-processing

After the solver runs, FreeCAD reads the result files and creates a Result object containing field data (displacement, stress, temperature, etc.). The simple Show Results tool displays a colour-mapped view with a slider to exaggerate deformation.

For advanced post-processing, FreeCAD uses VTK (Visualisation Toolkit) — the same library used by ParaView. The VTK pipeline tools allow clipping, warping, line plots, stress linearisation, and custom calculator fields.

Typical workflow

1. Create Analysis       ← FEM → Model → Analysis container
2. Assign materials      ← FEM → Model → Materials → Material Solid
3. Generate mesh         ← FEM → Mesh → Mesh from Shape (Netgen or Gmsh)
4. Apply BCs and loads   ← FEM → Model → Mechanical / Thermal / ...
5. Add solver            ← FEM → Solve → Solver CalculiX (or Elmer, ...)
6. Choose analysis type  ← Solver properties: static / frequency / thermomech
7. Run solver            ← FEM → Solve → Run Solver
8. View results          ← FEM → Results → Show Results
9. Post-process          ← FEM → Results → Pipeline from Result (VTK)

Relationship to other workbenches

Workbench Relationship
Part Design The most common source of FEM geometry — bodies are meshed directly.
Part Part shapes and compounds can also be analysed.
Spreadsheet Material properties and load values can be driven by spreadsheet aliases.
TechDraw FEM result images can be inserted into TechDraw drawings as bitmap views.

See the Tools index for a complete reference.