FEM CalculiX

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This page collects all information about the [CalculiX] solver, the most used and best developed solver in the FEM Workbench (as of FreeCAD 0.17-0.18_pre). Depending on the OS you are working with, most likely you'll need to pre-install CalculiX first. Check out FEM Install.


Interaction between the FEM Workbench and CalculiX is done by text files. The sequence of the FEM Workbench for CalculiX is as follows:

  1. creates a CalculiX input file
  2. starts CalculiX application
  3. logs the output of CalculiX and
  4. reads the output files of CalculiX (if they are available)

The FEM Control Solver tool manages the whole process. User interaction in the process is possible.

Preprocessing interface

CalculiX uses abaqus input file format. The input file could be edited before the solver is started. The units used in the CalculiX input file are independet from the units used in FreeCAD. They will be mm and N. (ToDo: check this. What happens with the mesh if inch is used in FreeCAD. Density was introduced. With this we have kg and s and no longer N?! how about this !?!)

The FEM Workbench CalculiX interface supports the following objects:

FEM Elements
  • linear static analysis
  • Frequency analysis
  • Coupled thermal structural analysis
  • one linear elastic isotropic (uniformity in all directions) material
  • multiple material is in development

Postprocessing interface

read resulting stress (Von Mises) and all displacement