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In robotics, I've seen quite a few people make use of cycloidal drives. They seem robust, compact and have a relatively simple design, while still achieving high reduction ratios.

Yet outside robotics, they don't seem to be that popular- often times, other high reduction gearing is used e.g. worm drives.

I was wondering why this is and what advantages/disadvantages cycloidal drives have over their worm gear counterparts.

Maybe it's ease of manufacturability, cost or something else I'm missing.

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  • $\begingroup$ Probably the strain wave reducer is better suited for robotics. The robots ive had to open either had strain wave reducer, cycloid or a planetary gear. But obviously the good thing about a worm drive is that its simple, can be very small and its not inline which can be useful in some usecases. Worm drive is also relatively easy to make. The downside of a cycloid is that its not balanced, balancing it increases complexity a lot. $\endgroup$
    – joojaa
    Oct 31, 2023 at 19:31

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Your question is so open ended that its hard to answer. But lets try. The reason is almost certainly cost, manufacturing capability and legacy reasons.

A worm gear is very easy to make in volume. This may sound a bit weird, since if all you have is a cnc mill then it seem that a cycloid is a no brainer. A worm gear can be made by hobbing or power sikiving. While they require a specialized tooling once you have the tool its extremely simple to make these parts. So for a worm gear you need 4 bearing journals and two features with special tooling. This is relatively simple to do with even non CNC equipment in a dedicated setup.

The worm drive is also a very old invention. This means there are old dedicated factory setups that can churn out worm drives very cheaply. The result of this is that all kinds of weird things have been done. I have seen ultra cheap worm drives that have been stamped out of sheet stock. While technically possible with cycloid drives too, I have not encountered one.

Then there is the thing that worm drives change the direction of the axis of the output. This is a benefit in some applications. Likewise many machinery dont need to rotate both ways so much of the must have features in robotics like backlash might be of no concern to the application at hand.

And finally there is also some cultural inertia, if you have a design that works why adapt it to a new form factor. Consider that the tuners of guitars and ukuleles are worm gears! Could you manufacture as small cycloidal gears, for less than 10 cents a piece?

Beverything except robotics is surely a big area so there can be many other reasons too.

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  • $\begingroup$ Thank you! This makes sense- it seemed like the cycloidal drive was not that much harder to make than the worm drive and there seems to be some nice efficiency gains. But definitely agree that once you have the tooling it makes little sense to change. $\endgroup$
    – testing09
    Nov 1, 2023 at 19:00
  • $\begingroup$ @testing09 Yeah well but a cycloidal gear requires much more parts, which increases cost. All you really need for a worm gear is a lathe, See youtube.com/watch?v=-umcQtrn1CQ . Anyway consider also cultural artefacts, you probably dont want to use cycloid gearing as the tuner of a guitar, yet the worm gears are used. $\endgroup$
    – joojaa
    Nov 1, 2023 at 19:43

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