Direct extruder for my SquareBOT 3D printer. Fits for Nema16/Nema17 stepper motors with planetary gearboxes any gear ratios. My stepper motor is Nema 17 with planetary gearbox 5:1 gear ratio. (part # 17HS13-0404S-PG5 from StepperOnline). Nema 16 motor (part # 16HS13-0604S-PG5) has an identical size gearbox, except shaft diameter (8mm). I'm going to use short-distance E3D hotend, so the bottom side has the mounting groove. SquareBOT 3D printer: http://www.thingiverse.com/thing:480008 News: The knob part needs a support and thick walls. Fan 40x40x20mm. You need also: