I talked a lot about Pre processors FreeCAD and Salome, in some cases the pre processor environment is more and offers the complete modelling package including a solver as in the case of FreeCAD. Calculix is the tool that will pick up a meshed model with boundary conditions and calculate specific results, being structural displacements, stresses, thermal behaviours and other physics.

A good work that was performed in making sense of these tools can be found on the following link:

https://www.theseus.fi/bitstream/handle/10024/87106/Neupane_Dilip.pdf?sequence=1

and Calculix documentation can be found here:

http://web.mit.edu/calculix_v2.7/CalculiX/cgx_2.7/doc/cgx/node4.html

It is important to know what Calculix needs input files  calculate something, this will depend on the type of files.

Geometry
• .Fbd
• .Step
• .stl

Mesh Generator and boundary-condition inputs (Model)

• Abaqus (Input)
• Ansys (Export)
• Code_Aster (Export)
• Samcef (Export)
• Dolfyn (Export)
• Duns (Export)
• Isaac (Export)
• OpenFOAM (Export)
• Nastran (Export)
• Tochnog (Export)

Mesh Generator

• Abaqus (.inp)
• Netgen

Read solver files
• Frd
• Duns
• Isaac
• OpenFOAM
• Nastran