CalculiX FEM
CalculiX (ccx) is an open-source FEM solver (GPLv2, no license). It reads
Abaqus-style .inp decks and writes text .dat results plus .frd field output.
ccx returns exit code 0 even on *ERROR, so never judge success by the exit
code — the solver layer checks stdout for *ERROR and requires a data row in the
.sta.
When to Use
Use this skill when an agent must run an open-source linear-static FEA analysis on
CalculiX: parse/inspect a .inp deck, tune section/material/load parameters, solve
with ccx, read .dat results, or export a viewer-renderable result. For commercial
solvers (Abaqus/Ansys), use those solvers' own skills instead.
Workflow
fea_health— confirm meshio is available andccxis detected.parse_inp— inspect the.inp(nodes, elements, sections, materials, loads).list_design_vars_tool— list tunable variables; each carries avar_id.modify_card_tool— change a variable byvar_id(pure-text, in place).run_solver_tool— submit the deck toccx.read_results_tool— read max von Mises (self-computed), max |U|, volume, mass.export_results_tool— writeresult_mesh.jsonfor the viewer.
Rules
- Units follow the
.inpworking system (commonly mm-t-s-MPa). Report them. .dathas no von Mises column and no total volume/mass — these are derived.- Never rewrite a deck with
meshio.write(it drops cards and corrupts element types). Usemodify_card_tool. - For the deck to produce both text results and the field output the viewer needs,
include
*NODE PRINT/*EL PRINT(for.dat) and*NODE FILE/*EL FILE(for.frd).
Example
MCP/CalculiX/examples/cantilever.inp is a public cantilever benchmark (steel
C3D8 solid bar, clamped end, transverse tip load). Hand-calc targets at P = 100 N:
tip deflection ≈ 0.8 mm, root stress ≈ 140 MPa.
