Bunny and Butterworth MK3S Geared Extruder

thingiverse

(Please download latest files just before printing to ensure you have most recent revisions) Geared extruder mod for MK3S extruder integrates the Bunny Science Gearbox with the Butterworth design (Nathan Whitchurch) N4 and N4A (indirect laser) versions of MK3S extruder. Antegrade = motor runs in normal direction, shaft pointed to back of printer Retrograde = motor runs backwards, shaft pointed to front of printer Six variants are supplied 1. N4XT MK3S sensor, retrograde motor 2. N4XT indirect laser, retrograde motor 3. N4 MK3S sensor, retrograde motor 4. N4A indirect laser, retrograde motor 5. N4 MK3S sensor, antegrade motor 6. N4A indirect laser sensor, antegrade motor The retrograde variants place motor mass closer to x-axis as in the Bunny and Bear Retrograde option extruder. Unfortunately, due to interference with the indirect sensor mechanism, it was not possible to move the motor 4 mm further back for indirect laser versions. The N4 or N4XT Retrograde options with their maximal motor mass setback would be my choice. The N4 motor plates can be interchanged with each other. They share a common extruder body. Similarly, the two N4A motor plates can be interchanged. You cannot swap N4 with N4A motor plates as the N4 extruder body and N4 extruder body differ from each other. Butterworth versions were used as bases because he corrects the Prusa R4 MK3S filament path. Bottom hot end fin opening diameter were tightened to 22.4 mm Bunnies have supplied only the parts modified or added to implement geared drive. You will need the rest of the extruder parts from the original Butterworth designs. See https://www.myminifactory.com/object/3d-print-86329 ----- Advantages of Bunny and Butterworth Geared MK3S Extruder Improve extruder uniformity via gearing like Bunny and Bear, Skelestruder or BMG extruders. Reduce extruder mass by about 70 gm compared to stock motor. Move motor 4 to 14 mm closer to x-axis than possible with just the Bunny Science Gearbox. Reduces moment arm by moving motor closer to axis. --- Upgrade replaces extruder body, motor plate, and idler door. You will need some MK3S extruder parts like x-carriage, back clamp, PINDA clamp, tail, etc. Motor plate / gearbox MUST be printed with supports. 3mf file supplied with suggested plating and support enforcement block for N4 variants. Specify support only for the gearbox portion and up to the 2nd bearing. This leaves filament path unmarred by support material. 3mf's are set for 0.15 mm layers for nicer finish. Removing support material from inside gearbox cavity takes 10 to 15 minutes. Take care to completely clean out mounting holes for bearings. Push shaft rod into gearbox from outside to remove support material within bearing mounts. If you do not clear out bearing mount holes completely, bearings will not spin freely. Some support scarring will remain, but is largely hidden by installed motor. --- NO - YOU CANNOT PUT THE MOTOR PLATES FROM THE BNBTR PROJECT ON A STOCK PRUSA R4 EXTRUDER BODY. The BNBTR includes a filament path correction. Although the motor plates may seem to fit, the path difference will crush your PTFE tubing. --- Build with THREE shaft bearings. 3rd bearing goes in rear of extruder body and optionally adds extra shaft support. see https://www.thingiverse.com/thing:3595205 for shaft cutting guides and instructions --- Materials needed... Antegrade shaft (both MK3s and Indirect Laser Sensor) 1 x 5 mm shaft rod shaft x 44 mm long, grind two flats 0.38 to 0.4 mm deep BNBTR Antegrade (both MK3S & IDL use same shaft) Length 44 (3 bearings) Pulley Flat 0 to 15 mm Bondtech Flat 28 mm to end The retrograde versions require longer shafts. Please verify length and shaft flat locations. They are as below BNBTR Retrograde MK3S sensor Length 61 mm for 2 bearings (Optional 65 mm long if 3 bearings) Pulley Flat 0 to 9 mm Bondtech Flat 50 mm to end BNBTR Retrograde IndirectLaser sensor Length 65 mm for 2 bearings (Optional 69 mm long if 3 bearings) Pulley Flat 0 to 9 mm Bondtech Flat 54 mm to end 3 x 1050ZZ bearings 1 x continuous loop 140-2GT-6 Timing Belt 3 x M3 square nuts 3 x M3 set screws M3 hex nuts & bolts (various lengths from 12 to 30 mm long. Some must be cut to custom length during assembly) M3 washers 1 x 16T drive pulley (to simplify alignment, use one for a 10 mm wide GT2 belt despite the belt being 6 mm wide) Motor - 1.8 degree, STEPPERONLINE Nema 17 Bipolar Stepper Motor 0.7A 13Ncm (18.4oz.in) 17HS10-0704S. This is the ONLY short body motor that worked well in my testing. Wiring harness for motor. If building a retrograde motor plate option, cutting gear shaft shorter to engage only front 2 bearings reduces friction. The standard motor plates are not as deep and may benefit from the 3rd bearing. On the other hand, the BNB bolt on gearbox functions well without a 3rd bearing. ---- You MUST also set e-steps by sending g-codes to printer M92 E980 M500 ---- Pulley gearing inspired by Skelestruder ----- B02 Added N4A indirect laser variant Added standard (non mmu) idler door Main extruder bodies and motor plate gearboxes now have index pins to assist with alignment. B03 Increased cable passage clearance. Added Bunny Science pulley and spacers Added retrograde motor plate options. B04 Stronger Bunny Science pulley B05 Fixed retrograde motor plates to allow for bridging clearance sags. Moved motor collar coving for easier motor insertion into retrograde motor plates Tightened bottom cooling hot end fin opening to 22.4 mm Added N4 extruder covers that also implement 22.4 mm change B05a Extruder body index pins adjusted for easier motor plate engagement Added N4XT retrograde versions for MK3S and indirect laser sensors. B06 Removed redundant motor mount holes from retrograde motor plates. Fixed interference with indirect laser assembly and motor plate Changed shaft flat grinds to ends of shaft for easier alignment during assembly