Using free software, we can convert a 3D scan (STL) into a CAD format (STEP). This process is called reverse engineering. We will reconstruct a solid model based on a 3D scan. This is not an automatic process, but a manual reconstruction. For this tutorial, we will use Netfabb (version 7.4.0) or Netfabb (current version) to measure the 3D scan. And the current version of FreeCAD (free CAD software) to redesign the part in CAD.