This is a compact gearbox for NEMA 17 stepper motors. It is intended to be used for extruders, but can be used in many other applications as well. The gears are mostly enclosed in the housing.
This gearbox does NOT change the direction of rotation of the motor. Because of that and its small size, it can be used in many printers. No firmware changes are necessary; just multiply the extrusion multiplier value in your slicer by 3.3, because this is a 33:10 gearbox.
Additional parts:
- NEMA 17 stepper Motor
- 3x M3x30 screw
- 5mm steel shaft
- Spacers for that shaft
- 6x M3 nut
- M3x5 grub screw (I cut the head of a normal screw and cut a slit in it)
- M3x12 screw or another M3 grub screw
- 2x 625ZZ ball bearing (5x16x5mm)
Print instructions
Instructions:
Printing:
- All parts except the small gear should be printed “upside down”
- All parts except the upper half of the housing and the big gear can be printed without support material
- I printed them in PLA with thick walls and many top and bottom layers
- Currently, holes etc. are 0.15mm larger than they would need to be. This is to account for over extrusion or a printer that is not perfectly calibrated. If you need more play (like I did) or less, you can download the .f3d file, open it in Autodesk Fusion 360 and change t under modify --> change parameters, and then save the bodies as .stl.
Assembly:
- Put the nut, screw and shaft in the big gear
- Put the nut and grub screw in the small gear and slide it on the stepper motor shaft. The end of the shaft should be flush with the top of the gear
- Place the bottom half on the stepper motor while inserting the bearing in it
- Place the big gear over the small gear and make sure everything fits, then tighten the screws and put on the spacers
- Place the second bearing in the bearing retainer and put them in the top half of the housing, then heat up a needle and melt the plastic in a few spots to secure the bearing in place
- Put two m3 nuts in the holes in the upper housing
- Place the upper housing on over everything else and secure everything together with the 3mm m3 screws
Project18
