Nema 17 Gearbox "Pulleybox" Mod for Extruder

thingiverse

4/27/2020: Latest versions have been updated, and these are now considered "Release Candidate". The hex nut version holes were fixed (they were 4.2mm instead of 3.3mm for screw), and I also realized that 4.2 is the size for heatserts when remaking this design, whoops? A slight redesign of screw pockets for motor has been done, with a little more plastic and it's now squared off. Draft was added to the "spokes" to help bridging. The outside bearing pocket was adjusted by .1mm, now matching the inside bearing pocket depth of 4mm. The spacer is slightly larger for a tighter wheel fit (in addition to the bearing pocket adjustment), and the v3 spacer is also easier to slip onto the shaft as the ID is bigger (5.5mm). More surface area has been added to the part that touches the wheel. Thanks go out to Grégoire and Florian for testing and providing critical feedback on these changes. STLs are included for now, with STEP and fusion updates to come later. Soon, a BOM, print settings, and assembly guide will be created. Stay tuned! 4/19/2020: Another update to the single piece design has been made, older versions wouldn't allow you to tighten fully depending on how deep the flat is on your shaft. 4/18/2020: The single piece has been updated to b2 release, with the wheel tread now thicker (6.6mm instead of 6.1mm that skele and Zaribo wheels use). A new spacer has been added, which has a slightly larger ID for easier assembly. Heatserts are still recommended. I really loved the "Bunny Science Extruder Motor Gearbox" by BunnyScience. I used it with some minor modifications but BunnyScience moved on to making complete extruders, so I wanted to make some additional refinements. This mod works effectively the same way but there are some changes in the design to slightly improve (per my opinion). Changes from Bunny Science Extruder Motor Gearbox * Better optimized for 3d printing, prints with no supports and the geometry should print using bridges instead of sloped overhangs. * Less plastic making it 30% lighter (19 grams vs 27 grams). * I'm using this on a bear extruder, and a bear extruder is happier with chamfers instead of fillets. * The BunnyScience design belt was a little too tight for me and the 16T pulley had to be almost right on the motor to prevent the belt from rubbing. I moved the motor out a little to allow more room here. * Just think it looks better, but this is just my opinion. Materials (This is basically the same as the BunnyScience gearbox) * 1 x 5 mm shaft rod with two flats ground 0.35 to 0.4 mm deep (STL for Jig is provided) Length 45 mm * 2 x 105ZZ bearings * 1 x continuous loop 140-2GT-6 Timing Belt * 4 x M3 hex nuts * OR 4 x M3 Heatserts * 1 x M3 square nut * M3 * 6mm screw (set screw for wheel) (JLTX Wheel, see skelestruder guide for more details on this step) * 3 x M3*18mm Screws * 3 x M3 washers * 1x16T drive pulley Assembly is basically the same as the Bunny Science gearbox. Prusa FW Settings For 1.8 degree stepper you will want to use 1/16 microstepping on the E axis, for a .9 degree stepper motor use 1/8 microstepping. And with both you would want to use 490 esteps. Example M350 E16 ; sets microstepping to 1/16 M92 E490 ; sets esteps to 490 M500 ; save to eeprom You can verify your current settings by issuing M503