Process design for the object to produce
In order to produce a 3d object the most important thing is to produce a drawing file in the format STL that contains the geometric description of the object, which can be more or less detailed. You can start from other 3D formats and with a tool like MeshLab do the conversion to STL. (Starting formats: PLY, OFF, OBJ, 3DS, VRML 2.0, U3D, X3D and Collada).
From the STL file it is then necessary to generate the G code which is what is used to operate the printer (it actually contains the instructions for the three translational axes of the printer along the route that the extruder will have to follow to create the object through the deposition of thin filaments).
Selection of CAD software
Today there are several possibilities for the CAD modeling software choice.
Using this link you can find a list of Opensource CAD
3D modeling software selected in the short list, see the table below.
| CAD | License | Platform | Complexity | Note |
| Sketch up | Basic version is free. | Win, Mac, Linux with Wine | easy to use. Work for extrusion | Plugin for generating STL directly. Plugin to make complex objects Curviloft (Lofting). Parametric via Ruby scripting |
| Blender | Open Source | Win, Mac, Linux | Overall | Direct Modeling Mesh-based (digital sculpting). Non-parametric. Focused on 3D modeling and animation art |
| OpenSCAD | Free Software GNU GPL V2 | Win, Mac, Linux | Parametric scripting language. Work with Constructive Solid Geometry (CSG) and extrusion of 2D | Spread. On Thingiverse has become a standard for sharing projects. Suitable for simple models and parametric design. Less suitable for complex models |
| FreeCAD | Open Source | Win, Linux, Mac | Focused on modeling mechanical parts | Parametric 3D Modeling. Python scripting |
| Tinkercad | Free version | Web | Easy to use, works on solid composition fundamentals | Parametric Shape Script (JavaScript) |
For this project Tinkercad was preferred because it does not require installation and it fits well in term of functionalities with the scope of the project. A user Thymio3d was created in Tinkercad, used to design the objects.