{"id":904,"date":"2018-03-23T15:08:52","date_gmt":"2018-03-23T15:08:52","guid":{"rendered":"http:\/\/project.inria.fr\/softrobot\/?page_id=904"},"modified":"2022-11-07T09:23:40","modified_gmt":"2022-11-07T09:23:40","slug":"from-design-to-mesh-generation-using-freecad-and-gmsh","status":"publish","type":"page","link":"https:\/\/project.inria.fr\/softrobot\/documentation\/from-design-to-mesh-generation-using-freecad-and-gmsh\/","title":{"rendered":"From design to mesh generation using FreeCAD and GMSH"},"content":{"rendered":"

From design to mesh generation
\nusing FreeCAD and GMSH<\/h1>\n

 <\/p>\n

In order to simulate a mechanical object using Finite Element Modeling (FEM), a discrete version of its volume is required. This volume, referred as volumetric mesh will serve as a domain for FEM computation. 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. Several tools exist for 3D modelisation such as OpenSCAD (http:\/\/www.openscad.org\/<\/a>), FreeCAD (https:\/\/www.freecadweb.org\/<\/a>), or Blender (https:\/\/www.blender.org\/<\/a>). Several tools also exist for volume meshing such as GID (http:\/\/www.gidhome.com\/<\/a>), CGAL (http:\/\/www.cgal.org\/<\/a>), or Gmsh (http:\/\/geuz.org\/gmsh\/<\/a>). For CGAL, a dedicated plugin is available within the SOFA framework (see a documentation here<\/a>).<\/p>\n

In the following, we will show an example using FreeCAD for the design and GMSH for the mesh generation. We will also try to give useful links.<\/p>\n

A. Design and Modeling using FreeCAD<\/h2>\n

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.<\/p>\n

1. Sketch<\/h3>\n

The first step is to sketch your structure. In FreeCAD you have several workbench<\/a> (Part, Sketcher…) showing the different corresponding tools. Here we choosed the “complete” workshop, which displays a sample of all the workshops. Clic on sketch (\"\"<\/a>). When sketching, keep in mind that there are tools to automatically generate symetries. Here are the tools to draw your sketch (\"\"<\/a>) and to set constraints (\"\"<\/a>). See for exemple this video<\/a> for a detail tuto.
\nWhen 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.<\/p>\n

\"\"<\/a><\/p>\n

2. Revolve<\/h3>\n

The next step is to use the “revolve” tool (\"\"<\/a>) to create the solid. See for example this video.<\/a><\/p>\n

\"\"<\/a><\/p>\n

3. Mirror and Fusion<\/h3>\n

Now we use the “mirror” tool (\"\"<\/a>) to get our final shape.<\/p>\n

\"\"<\/a><\/p>\n

The structure is in two parts:<\/p>\n