Here at Key Tech, we often use physical prototypes in our design process to literally get a feel for the part. While 3D computer models can be helpful, there is simply no substitute for actually holding a part in your hands and feeling it. 3D printing is often a great option for an initial prototype, especially for complex parts that are difficult to machine. Essentially, 3D printers work by printing many thin 2D cross-sections of a part on top of each other, bonding each layer to the previous one as they go. For more complex parts, special support structures may be required to keep the part from falling apart during the printing process, but the process is essentially the same.