BullDog Extruder mount with 1:4 speed reduction for 2.85 mm filament (for 3030 extrusions)

thingiverse

UPDATE: a more compact version is found here. There are only a few good extruders for 2.85 filament available on this website, but none of the ones I printed worked well enough for me. I decided to look at what stuff I had laying around (as I didn't have the time to wait for new parts) and designed a simple mount for a NEMA17 stepper and the aluminium BullDog Extruder. The direct placement of the Bulldog extruder onto the NEMA17 did not work well, resulting in skipping as the filament exerted too much force onto the extruder gear. The design incorporates a speed reduction of 1:4, which increases the torque required for the filament to be pushed through. The reduction uses a 16 teeth idler and a pulley printed from Parametric Pulley for toothed belts in OpenSCAD by 0scar. Note the sliding attachment of both the NEMA17 stepper (to tension the 200-2GT-6 belt) and the BullDog extruder (to allow various different extruder gears, e.g. MK8 which I'm using now, the default BullDog gear or the knurled Ultimaker extruder gear). Note that this will also give support to 1.75mm filament! The offset for the BullDog extruder is set by two horizontal screws in the vertical mount (this uses two brass 5x5xM3 knurled brass inserts). Two more knurled brass inserts are used in the top mount to secure the lid that holds the 5mm shaft and its bearing in place. Parts list: - 200-2GT-6 belt - 16 teeth idler pulley for 5mm shaft of NEMA17 - 64 teeth idler pulley - a 5mm shaft (make some flat spots on it to secure the extruder gear and the 64T idler wheel) - two 695 ZZ bearings (5x13x4mm) - M3 screws (various sizes 8, 12, 14mm), washers and (lock)nuts and four brass knurled inserts Note that at the time I had only pneumatic fittings with 10 mm diameter threads, so I designed a small mount for using those instead of the 6mm threaded ones that fit the BullDog extruder natively.