Direct Drive Bowden Extruder for 20 mm extrusion

thingiverse

An open-source Direct Drive Bowden Extruder with bolt-free attachment to 20mm extrusion is designed for ease of use and cleaning. It can also be fixed using a single bolt. Key features include a simple, compact design, adjustable drilling for 1.75 or 3mm filament, and compatibility with a 5mm or 1/8 coupling. The Arcol hobbed pulley is position close to the motor base to minimize cantilevered load on the motor shaft. Inspired by other open-source extruders, this design uses an 86oz*in motor with a DRV8825 stepper driver for 1.75mm filament; geared stepper drivers may be needed for 3mm filament, available on eBay with compatibility for Nema 17 bolts. A mirror image of the extruder is provided, requiring deletion of unnecessary parts and splitting in slic3r to print the arm separately from the base. An Extruder 1.4NPT is added to accommodate larger pneumatic fittings. The necessary components include a Nema 17 stepper with high torque capability, a hobbed pulley set screw (5mm ID), a pneumatic coupling, a 625 bearing, M3-8mm bolts, an M3-12 to 16mm bolt, an M5-12mm bolt with nut, an M5-30+mm bolt with nut and washer, and a spring for tensioning over the M5 bolt. A knurled nut is suggested for the spring tensioner, but a normal or winged nut could also be used. An alternative design similar to this one can be found at http://www.thingiverse.com/thing:102153.