Tinkering with FreeCAD An introduction to FreeCAD, the free and open source CAD tool, for anyone who wants to start designing parts of their own. We'll find our way around the interface, sketch a simple part, and turn it into a 3D model. Along the way we'll cover parametric design, which is the thing that makes CAD worth learning: change one dimension and the whole model updates instead of you starting over. We'll also look at exporting for 3D printing.