Printing Strain Wave Gears

We just wrapped up the Robotics Module Challenge portion of the Hackaday Prize, and if there’s one thing robots need to do, it’s move. This usually means some sort of motor, but you’ll probably want a gear system on there as well. Gotta have that torque, you know.

For his Hackaday Prize entry, [Johannes] is building a 3D printed Strain Wave Gear. A strain wave gear has a flexible middle piece that touches an outer gear rack when pushed by an oval central rotor. The difference in the number of teeth on the flexible collar and the outer rack determine the gear ratio.

This gear is almost entirely 3D printed, and the parts don’t need to be made of flexible filament or have weird support structures. It’s printed out of PETG, which [Johannes] says is slippery enough for a harmonic drive, and the NEMA 17 stepper is completely contained within the housing of the gear itself.

Printing a gear system is all well and good, but what do you do with it? As an experiment, [Johannes] slapped two of these motors together along with a strange, bone-like adapter to create a pan/tilt mount for a camera. Yes, if you don’t look at the weird pink and blue bone for a second, it’s just a DSLR on a tripod with a gimbal. The angular resolution of this setup is 0.03 degrees, so it should be possible to use this setup for astrophotography. Impressive, even if that particular implementation does look a little weird.

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3D-Printed Strain Wave Gear Needs Your Help

In most mechanical systems, metal gears that bend are a bad thing. But not so for strain wave gearing, which is designed to take advantage of a metal gear flexing to achieve an action much like planetary gears. The fun isn’t limited to metal anymore, though, if you 3D print a strain wave gear like this.

Strain-wave gearing is nothing new – it was invented in 1957 and has traveled to the moon on the lunar rover. And you may recall [Kristine Panos]’ recent article on a LEGO strain wave gear, which makes it easy to visualize how they work. She also has a great description of how the flex spline, wave generator, and circular spline interact, so we’ll spare those details here. [Simon Merret]’s interpretation of the strain wave gear is very simple and similar to other 3D-printed versions, except that he uses an inside-out timing belt as the flex spline. The wave generator is just an arm with a roller bearing at each end, and despite needing a few tweaks the gear does an admirable job.

Simon is reaching out for help in getting this gear ready for use where the industrial versions see frequent application – the first and second degrees of freedom of robotic arms. If you’ve got any ideas, head over to his project page on Hackaday.io and pitch in.

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Ask Hackaday: What Are Magnetic Gears (Good For)?

Magnetic gears are surprisingly unknown and used only in a few niche applications. Yet, their popularity is on the rise, and they are one of the slickest solutions for transmitting mechanical energy, converting rotational torque and RPM. Sooner or later, you’re bound to stumble upon them somewhere, so let’s check them out to see what they are and what they are good for.

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