3d Printed Gearbox for Small Dc Motors





Introduction: 3d Printed Gearbox for Small Dc Motors

About: Passion for making.

I have many salvaged dc motors just laying around in my garage. They
often produce too high rpm/ low torque for many application. So I decided do something about this problem. I just bought my first 3d printer (prusa i3 clone) so this was quite easy problem to fix. I only got PLA plastic available so the heat was bit a problem but if you follow this guide you can make it work too. I also made a test wheels so your next robot can move around :)

Step 1: Assembly Video

All steps are included in this video. There's some test setups in 5.40 mark.

Step 2: Technical Details and Materials

This gearbox has ratio of 1/16. With this 12v motor it can lift around 3,5kg (straight from the shaft.) 2 washers should place between each gear (see details in video). It reduces heat between plastic parts when 2 washers is rubbing each other. Adding lots of bearing grease between everything is essential. Depending your printer tolerances you might need drill out some holes bigger. Motor mount should be standard size.

My print settings with slicer.


  • layer 0.2
  • infill 25%
  • perimeters 3
  • bottom layer 2, top 3


  • Layer 0.3
  • infill 20%
  • perimeters 2
  • bottom layer 2, top 3

Step 3: Files

If you want know more about gears and ratios check for google "compound gears".

All comments are welcome. Thank you !

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18 Discussions

Happy to see a use for my salvaged DC motors! 2 questions though.

1. My Prusa clone (CTC) consistently prints PLA small, resulting in me having to up the scale 102%, does your printer do this and did you design it accordingly?

2. Would you ever consider sharing CAD files for some of us to tinker with it? Say to change gear ratios for different applications.

1 reply


I don't have any problems with scaling when printing it. The Design should print fine with 100% scale option. Right now I don't have a time to convert sketch up files to CAD compatible format. Thnx for your interest.

Cool project ... thnx for sharing with us ... can u tell me the weight of this gear box To calculate it's cost for me ?!

This is beautiful !!!
really liked it looked really proffesional!

Thanks for your nice job. What chemical did you used in the surface finishing step of the gearbox?

1 reply

Firts I clean all surfaces with oil and dirt cleaner. Then I add 1 layer of primer, 2 layers of surface paint and 2 layers of clear laquer. Im using acrylic spray paints.

Very good!

good for a battery powered irrigation controller - thanks a lot !


1 year ago

The gearbox looks great and it's just what I need for a project I am working on. What is the electric motor you are using and where can I buy one?

1 reply

My motor 12v version. If you have old printers, scanners.... you may find these motors inside it.

Here's couple links to ebay.



I really enjoyed this instructable; as others have said (and you mentioned inspiration from), you're not too far away from it being a servo!

Very nice job. The press fit to the motor shaft is common. In older toy trains the stress of the press fit can lead to splitting, so don't skimp on the diameter of the hub. I've added brass rings to fix split hubs with good results. Good luck and thank you for the inspiration.

Add a potentiometer, make some space for an ATTINY and a H bridge inside the casing and you've got yourself a servo

1 reply

Good point. When I designed this gearbox I actually studied servos and how the gears are arranged inside it.

Did you just press fit the gear onto the motor shaft? What keeps the shaft from just spinning without the gear moving?

1 reply

yes it's press fitted. Press fit if common way to attach gear to the motor shaft (small dc motors) High friction keep it in place.