Modular Gear Reducers

by mirk, published

Modular Gear Reducers by mirk Mar 28, 2011

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3:1 gear stages that can be assembled to get a gear ratio to any power of 3.

I needed to reduce the speed of a motor by a large degree. My first tries used a a worm gear, but I didn't have my support settings dialed in well enough to print one yet. I went with this design so it would be easy to add or remove stages depending on the desired gear ratio.

For my current project, I am using 6 stages of gear reduction. 3^6=729 so I have a 729:1 reduction in speed. Included with this is a 1:729 increase in torque.


Print one of the gear stages and one gear mount. Be careful depending on your machine, as the raft for the gear stage just barely fit on my ToM ABP.

The two pieces screw together using an M3 socket head screw. I used leftover M3x16's from building my ToM, however there is room for larger and smaller lengths. Any extra length of bolt will simply fall into the cutout in front of the gear two stages behind itself, and this actually helps to line them up better as well.

Screw the gear mounts down to a scrap piece of wood, as shown in the pictures. Holes are provided for 2 screws, however I used just the inner hole because it gave more play for the gears (preventing them from jamming) and also more precision in placement because the second screw always seems to move it out of place. Both might be a good idea for just the first one.

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Seeing this made me think... if there was a set of stackable gears with prime number ratios (2,3,5,7,11,...) then any reduction rate could be built by stacking the factors.

Correction: driving the smaller gear directly (see previous comment)

Im assuming if you were to drive the larger gear directly you would have the opposite effects, correct?

Driving the smaller gear directly takes an extremely large force, as the gearing ratio is so high. In fact, the plastic would likely break. However, if the force and materials were strong enough, then you would get a massively increased speed.

Made the 3 to 1 gear as my first print on a k8200. What design program was used for this? I noticed while it was printing, it did a hex shaped basket weave pattern internal to the part. Was that part of the design or is that something that slic3r does by itself. BTW, the thinning up the plastic sections is necessary to minimize warping of the part.

This is a combination of two stock gears from Solidworks. The internal pattern is something that is a part of your slicer. Warping will also be controlled by a combination of your software and printer specs.

Can you also release the file for the motor output shaft :-). I realize my motor is probably different than yours but my test setup is a very simple one that I think will hold w/glue. I am simply using the gear reducer to simulate the final form in a different machine.

The plastic piece on the output shaft was actually already on the motor. I ripped the motor out of a fan, and that part was there to attach to the fan blades. Unfortunately I don't have it any more so I can't model up the part for you :(

I have a problem gear transmission for a development of a machine I would like to have your email.
[email protected]
thank you
E. B

Excellent! :)

We can now each have "Machine With Concrete" as an existential reminder:
More Arthur Ganson:

Instead of a concrete block it can be attached to the 3D printer itself!

Thats awesome! I'd never heard of this guy before, but his sculptures are really cool.

I did a quick calculation, and I would need 43 stages of this for approximately the same gear ratio :-P.

That looks really cool. How much noise does it make?

The gears look perfect. Did they come off the ToM like that, or did you have to sand them, or otherwise clean them up?


It makes a decent amount of noise when the motor is running at high speeds, however I've reduced the motor speed to about 1Hz already for the project I'm using it for and at that speeds there's almost no noise. Part of the problem though is that the earlier versions of the gear stages had a lot of
play, and they're the ones that are closest to the motor and moving the fastest. I improved the design after each of the first 3 stages (the given files are the final versions) but didn't bother printing new ones because noise wasn't an issue for me at such low speeds. The new ones shouldn't make a
s much noise, but I haven't tested it. I'll try to upload a video in the next few days if you're interested:).

They came that way pretty much right off of the ToM with stock settings, I had to scrape a few leftover strands of raft off of the back to help reduce friction between the gear and the mou
nt, but thats the only post processing that was needed. The hole for the bolt was a little small in early versions so i just had to push the bolt back and forth through it a few times to increase the size, but it wasn't an issue with the most recent versions.