Translations:Manual:Modeling for product design/2/en

When you print objects in 3D, it is of ultimate importance that your objects are solid. As they will become real, solid objects, this is obvious. Nothing prevent them from being hollow inside, of course. But you always need to have a clear notion of which point is inside the material, and which point is outside, because the 3D printer or the CNC machine needs to know exactly what is filled with material and what is not. For this reason, in FreeCAD, the PartDesign Workbench is the perfect tool to build such pieces, because it will always take care for you that your objects stay solid and buildable.