The accuracy requirements and precision control requirements for 3D printers are all very high, and all use of stepper motors is necessary. Most 3D printers on the market use two-phase 42mm stepper motors. The 3D printer is a combination of X, Y, E, and X axes. 34mm is used on the E axis. The Z axis needs 40mm. The X axis and Y axis need a 48mm stepper motor. In general, 40mm will be used. With a screw, for external drive, if the length of the screw is 300 or so.