wave generator

2 Articles

3D Printed Strain-Wave Gearbox Turns Up The Torque

September 17, 2022 by 6 Comments

3D printers are good for a lot of things, but making parts for power transmission doesn’t seem to be one of them. Oh sure, some light-duty gears and timing belt sprockets will work just fine when printed, but oftentimes squooshed plastic parts are just too compliant for serious power transmission use.

But that’s not a hard and fast rule. In fact, this 3D-printed strain-wave transmission relies on the flexibility of printed parts to work its torque amplification magic. In case you haven’t been briefed, strain-wave gearing uses a flexible externally toothed spline nested inside an internally toothed stationary gear. Inside the flexible spline is a wave generator, which is just a symmetrical cam that deforms the spline so that it engages with the outside gear. The result is a high ratio gear train that really beefs up the torque applied to the wave generator.

It took a couple of prototypes for [Brian Bocken] to dial in his version of the strain-wave drive. The PLA he used for the flexible spline worked, but wasn’t going to be good for the long haul. A second version using TPU proved better, but improvements to the motor mount were needed. The final version proved to pack a punch in the torque department, enough to move a car. Check it out in the video below.

Strain-wave gears have a lot of applications, especially in robotic arms and legs — very compact versions with the motor built right in would be great here. If you’re having trouble visualizing how they work, maybe a Lego version will clear things up.

Continue reading “3D Printed Strain-Wave Gearbox Turns Up The Torque” →

3D-Printed Strain Wave Gear Needs Your Help

January 17, 2017 by 22 Comments

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.

Continue reading “3D-Printed Strain Wave Gear Needs Your Help” →