To be able to do a Finite Element Analysis (FEA) using the FEM Worbench FreeCAD makes use of two external programs. One is used for generating the FEM Mesh and the other for solving the system of equations. If your FreeCAD is set up to do mechanical Finite Element Analysis’s could be checked easily by loading and analyzing an example file. See FEM CalculiX Cantilever 3D
For solving the system of equations, CalculiX is used. FreeCAD writes a CalculiX input file, starts CalculiX and reads the output of CalculiX. This means CalculiX binary is standalone and independent from FreeCAD. Because of this and since there are more possibilities to get a valid FEM Mesh it is recommended to install the Solver first.
FEM Mesh Generator
In respect to a meshing tool, in order to create a FEM Mesh, FreeCAD uses Netgen. Using Netgen in the FEM Workbench, FreeCAD needs to be compiled against netgen libraries. Apart from Netgen a common way to create a FEM Mesh is the use FEM Gmsh mesh tool. For the use of this tool Gmsh has to be installed on your system. Check out FEM Mesh#Create a FEM Mesh for the various possibilities to create an FEM Mesh in FreeCAD.
Installation of external FEM Module Software
If either a stable or development version from Download is used no further software needs to be installed. Netgen and CalculiX are included in the FreeCAD download package.
The easiest possibility to get an working FEM Workbench on Linux is the use of the Ubuntu PPA Version. Check out Install on Unix#Daily PPA with console. The netgen FEM Mesh Generator is already included in the PPA version. CalculiX is an extra package provided by the Ubuntu PPA Version as well. If the Ubuntu PPA repository is already added to your package manager install CalculiX by
apt-get install ccx
The following FreeCAD Ubuntu PPA packages have Netgen and CalculiX:
- Ubuntu 14.04 (Trusty Tahr)
- Ubuntu 14.10 (Utopic Unicorn)
- Ubuntu 15.04 (Vivid Vervet)
For Developers: There is a huge forum thread in which the creation of the Ubuntu PPA packages was discussed. It may be useful if the Ubuntu PPA packages needs to be updated. On Launchpad there are more than one CalculiX packages. Only one CalculiX package should be installed and any of them should work. There is a simple reason for not taking the one which was already on Launchpad. We did not know about it (see http://forum.freecadweb.org/viewtopic.php?f=18&t=10393&start=90#p85498)
On other Linux distributions you need to make sure to get the appropriate software and libraries installed yourself before using FEM workbench.
Since CalculiX is a standalone software you either can install a CalculiX binary or compile CalculiX yourself. Any CalculiX version from 2.7.X works with FreeCAD. Since there hasn't been much changes in CalculiX resently lower versions than 2.7.X might work as well.
Install CalculiX Binary
There are only a few Linux Distributions which are known to have CalculiX Packages in their Repositories. Following a list:
- Arch Linux:
- Debian 09 Buster:
- Debian packages are outdated, thus https://forum.freecadweb.org/viewtopic.php?f=18&t=31360&start=10#p279925
- Debian 08 Stretch:
- Debian packages are outdated, thus https://forum.freecadweb.org/viewtopic.php?f=18&t=31360&p=279925#p260872
- Debian 07 Jessie:
- The packages of Debian Stretch can be installed by dpkg see FreeCAD forum
- CalculiX binary from ccx website:
- On the CalculiX Website it is possible to download a generic Linux binary of CalculiX. Check out http://www.dhondt.de/ Since any Linux Distribution could have different library paths it is likely possible this binary will not work out of the box at your linux distribution.
- Fedora 21:
- for newer fedora versions see how to compile CalculiX, there is a script out there.
- Some bash commands that may help too
Compiling CalculiX is not as easy as it is with many OpenSource software. There are many different resources at FreeCAD forum and the internet. Check out the following:
- Fedora 27, 28, 29
- There is a CMake Repository on github, but at FreeCAD forum noone has reported if this one works
There have been mixed results with the Netgen mesher and the compilation of FreeCAD with Netgen support.
The FreeCAD forum is a very good resource for informations in this regard. Check out google search on FreeCAD forum page by :
The OSX development packages of FreeCAD 0.17.xxxxx do include Netgen  but they do not include CalculiX.
See this forum post FreeCAD Fem on OSX how to install CalculiX on OSX Following informations might be outdated: