CalculiX is a classic open-source, general-purpose finite element solver licensed under the GPL. It supports linear and nonlinear static, dynamic, thermal, and contact analyses, and is natively compatible with the Abaqus INP input file format. It is widely used in university research and small-to-medium-sized enterprise simulations.
As a general-purpose CAE pre- and post-processing software, WELSIM features built-in pre-processing support for CalculiX: users can either one-click export CalculiX INP input scripts for offline calculation or directly call the CalculiX solver within the WELSIM graphical user interface to complete computations, streamlining the workflow of “CAD import -> mesh -> material -> boundary conditions -> solving.”
This article outlines the steps for co-solving finite element models using both software applications under the Windows operating system.
Software Preparation
Download and install the latest version of WELSIM; this blog uses the 2026R3 development version as an example.
The CalculiX solver can be downloaded as a pre-compiled package from the official website (www.calculix.de) or GitHub. After extraction, you will find the solver executable files in the bin folder: ccx.exe (serial) and ccx_MT.exe (multi-threaded parallel version). Users do not need to modify any of the extracted CalculiX files. Please note that you should avoid placing the CalculiX folder on the system drive (such as the C drive), and the absolute path of the folder should not be excessively long.
Path Configuration
When invoking the CalculiX solver via WELSIM for the first time, you need to briefly configure the CalculiX path. The steps are as follows: 1.Open the WELSIM software, and click Preferences in the menu or toolbar.
2.Locate the Solvers tab in the left-hand list.
3.Find the CalculiX file field on the right, click Browse, and select the extracted ccx_MT.exe or ccx.exe. On Windows, an example path could be: D:\WelSimLLC\executable34\CalculiX-2.23.0-win-x64\bin\ccx_MT.exe.
4.Click OK to save the configuration.
5.During specific finite element analyses, simply set the Solver property of the Study Settings node to CalculiX in the project tree window.
Once configuration is complete, you can directly call the CalculiX solver.
Conclusion
This article describes how to configure the co-solving of finite element models between CalculiX and WELSIM under the Windows operating system. The setup and operations in a Linux environment are largely identical. The WELSIM installation package does not bundle the CalculiX solver; users must download the CalculiX binary program themselves and configure its path, which is the core content of this article.
WELSIM does not yet support post-processing for CalculiX results; reading and displaying CalculiX result files will be supported in future versions.
WELSIM and the author are not affiliated with CalculiX or Abaqus, and have no direct relationship with the development teams or organizations of CalculiX and Abaqus. The names of the open-source software referenced here are used solely for technical blog articles and software usage reference.