ArmDrive Bowden Extruder

thingiverse

ArmDrive, a 1.75mm filament bowden extruder, was designed to work with NEMA 17 stepper motor. It mounts directly onto OpenBeam or equivalent sized (15mm) extrusion and can also be attached at a 90° angle with the help of a complimentary mounting bracket. The MK7 and MK8 versions are designed for specific drive gears, or those with similar dimensions. It is built to be robust and reliable using easily available hardware. The latest revision includes increased diameter post holding the 608ZZ bearing, more clearance around the outside of the bearing near the swivel shaft area, significantly stronger input filament alignment post, added support behind spring retainer arm on base-plate, and taller standalone posts on the base-plate. Revision 3 was released to increase rigidity of upper and lower arm segments in response to feedback about occasionally cracked or broken arms. A 90° mounting bracket is available for easy alternate angle installations. ArmDrive should be printed at .2mm layer height, with suggested print settings being a perimeter of 4, solid layers top and bottom of 4, infill of .4, and ABS plastic recommended over PLA due to warping over time, especially near the NEMA 17 stepper motor. Drill bit sizes required include 15/64" for upper and lower arm pivot holes, 1/8" for all screw holes except lower arm, and 7/64" for two lower arm screw holes. Metric drill bit diameters should be approximately 6mm for upper and lower arm pivot holes, 3.2mm for all screw holes excluding the lower arm, and 3mm for two lower arm screw holes. Be cautious while installing the lower arm on swivel post as it can break easily. A binder clip arm often provides enough tension with one arm, using four spring slots is optional but beware of excessive pressure causing premature failure. The alternate lower arm works with an M4 nut threaded directly onto the bowden tube or 4mm push-to-connect fitting. The 608 size bearing is a standard used in various products like scooters, skateboards, rollerskates, and fidget spinners, making it easily available.