Computer-implemented processes for allowing a user with limited technical knowledge to easily design 3D models. The 3D models generated by such processes may be 3D printed, as the models are solid, which is necessary for 3D printing. Each of these computer-implemented processes takes a small amount of simplified user input and generates one of a number of different 3D models. More specifically, based on the user input, the computer-implemented processes automatically generate CAD primitives, and automatically perform certain CAD operations on those primitives, such that a 3D model is generated.