When working with cavity, you can either include the cavity in your sketching or create the cavity later and use the boolean operation tool (difference) to remove the matter. See for exemple this video for a detail tuto.

Here are the tools to draw your sketch ( ) and to set constraints ( ). When sketching, keep in mind that there are tools to automatically generate symetries.

Here we choosed the “complete” workshop, which displays a sample of all the workshops. In FreeCAD you have several workbench (Part, Sketcher…) showing the different corresponding tools. The first step is to sketch your structure. In this section we will give a quick overview of how to design a soft pneumatic actuator using FreeCAD, together with links to more detailed explanations. In the following, we will show an example using FreeCAD for the design and GMSH for the mesh generation. For CGAL, a dedicated plugin is available within the SOFA framework (see a documentation here). Several tools also exist for volume meshing such as GID ( ), CGAL ( ), or Gmsh ( ). Several tools exist for 3D modelisation such as OpenSCAD ( ), FreeCAD ( ), or Blender ( ). The aim of this tutorial is to explain how to design a closed surface description made of triangles, and create a volumetric mesh from it. This volume, referred as volumetric mesh will serve as a domain for FEM computation. In order to simulate a mechanical object using Finite Element Modeling (FEM), a discrete version of its volume is required.

Freecad 2d tutorial