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I have designed and 3D printed a gear system with three gears. Two identical gears at each end with a smaller gear in the center. One of the larger end gears is to be rotated by a stepper motor, the middle gear transfers the motion to the other gear that carries a device.

The issue is that there is a wiggle in the end gears even when one is fixed/held in place. If I hold down the gear controlled by the stepper motor, I can still create a small bit of rotation in the other end gear (carrying the device). In the video, I show this 'wiggle' by holding down one gear and still being able to move the other.

What can I edit/change or add to the design to prevent this movement from happening e.g. design ideas or additional components I could add? I need the gears to be precise so that they move exactly with each other and no wiggling in one of them without the other taking place.

YouTube video showing the issue

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  • $\begingroup$ purchase higher precision gears $\endgroup$
    – jsotola
    Dec 29, 2022 at 7:22
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    $\begingroup$ the technical term for the "wiggle" is called backlash. You'll probably never be able to eliminate it entirely with a 3D printed gear, but you might be able to reduce it. How did you design your gears? It is hard to tell from the video, but it looks like the teeth might just be rectangles? If so, the first thing to correct would be to replace the rectangles with an involute profile. $\endgroup$
    – Daniel K
    Dec 29, 2022 at 18:24
  • $\begingroup$ This question probably belongs on this site: 3dprinting.stackexchange.com $\endgroup$
    – Bob Ortiz
    Nov 24, 2023 at 12:31

3 Answers 3

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3D printing is insufficiently precise to produce gears without backlash. You need injection-molded gears, or ones machined out of metal.

If you insist on using 3D printing, then you need to print the center gear a few thousandths of an inch bigger overall so as to obtain an interference fit between the center gear teeth and the outer gear teeth.

This means printing the hole in the center of the gear a few thousandths of an inch smaller to obtain a wobble-free fit with the shaft.

If your 3D printing process dimensions cannot be controlled to +/- 0.001", then your process is doomed.

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Include pins or shafts and sleeves that the gears get printed onto.

That means you control the clearance between the sleeve and shaft.

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  1. If the load is light you may be able to make the gears with zero clearance teeth (or even negative). The gears will be very tight but you can force them to turn manually until they break in just the right amount to have low backlash. If you lubricate them at this point and use them with very light loads, this condition might last decently long. Once the gears wear the backlash will come back.

  2. Make the teeth finer. Generally speaking finer gear teeth will have less backlash (scale of everything is smaller).

  3. You can make zero backlash split gears. The outer gears would be split into 2, and the halves adjusted or spring loaded so that teeth are always in full contact with the center gear.

zero backlash split gear

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