Compact Nema 17 Gearbox 6.5 to 1 Ratio

thingiverse

BudgeProjects had a solid concept, but his design needed refining instead of tinkering with his files; I tore down the gearbox from scratch. To correct his gear ratio, which isn't 16 to 1 as he claimed, it's actually 7.5 to 1. Gearboxes like this are calculated using a simple equation: (Driven Gear / Driving Gear) * Number of stages. So therefore his gearbox is calculated as (30/12)*3 = 7.5. With my own gearbox, I have a ratio of 6.5 to 1, since my driven gear is only 26 teeth. I've also used herringbone gears because they're quieter and offer a more positive engagement. I'm using different bearings too; on the main output side, I'm employing 623 bearings. Here's my BOM: 3D Printed Parts * 1 x Nema 17 with 21mm shaft * 3 x 623 Flange Bearings * 1 x 623 Bearing * 1 x 6802 Bearing * 6 x M3 x 6mm Socket Cap Screws * 1 x M3 x 50mm Socket Cap Screw * 4 x M3 Nuts My Gearbox design is significantly more compact than BudgeProjects'. Apart from the different gear ratio, I've greatly improved on his design and its looks; the use of nuts is more discreet, and the general appearance is better. Although my output shaft is 3D printed, it has a M3 Screw core for added strength. I'm currently printing the gearbox; once it's done, I'll upload pictures of the assembly and how to assemble the gearbox. Update: I've modified the gearbox because I made an error in my measurements, which meant the M3 axle couldn't fit. A few other minor changes have been made, but I now have a slightly increased gear ratio too. So, (31/12)*3=7.75; now the gearbox has a 7.75 to 1 ratio. Update 2: After assembly and testing operation, I applied PTFE grease lubricant to all the gears. I then ran the motor back and forth multiple times to work the gears into place. Initial operation of the gearbox would require it to be done with the lid off to get the lubricant on all gears and get them settled down and into position. Lubricant should also be applied to the inside of the lid, allowing the gears to slide smoothly over its surface; as the lid is used to constrain the gear position, continue running the gearbox in both directions multiple times until operation becomes quiet, and then it's ready for use.