It all starts with a digital file, the Computer-Aided Design file (one example seen above), which serves as the instructions for what to print. Think of the file as a blueprint. The machine then prints layer after layer of plastic, metal, nylon or another of the many materials that can be used. These layers eventually create the final shape.
There are several different methods that can be used to 3D print, depending on variables such as what material you want to use and how much you want to spend. The most common is Fused Deposition Modeling (FDM). With this method, an object is produced by use of melted thermoplastic material to form layers. Each layer stacks on top of and fuses with the previous layer as the material hardens almost immediately to create a 3D object.