3D printers are good for many things, but making parts for power transmission doesn’t seem to be one of them. Sure, some lightweight gears and timing belt sprockets will work just fine when printed, but often the crushed plastic parts are just too conformable for serious power transmission use.
But this is not an absolute rule. In reality, this 3d printed stress wave transmission relies on the flexibility of printed parts to work its torque-boosting magic. In case you weren’t aware, the strain wave gear uses an externally toothed flexible spline nested inside a fixed internally toothed gear. Inside the flex spline is a wave generator, which is just a symmetrical cam that bends the spline so that it engages with the outer gear. The result is a high ratio gear set that really boosts the torque applied to the wave generator.
It took a few prototypes to [Brian Bocken] to compose his version of the stress wave reader. The PLA he used for the flex spline worked, but wasn’t going to be good long term. A second version using the TPU proved to be better, but motor support improvements were needed. The final version proved effective in the area of torque, enough to move a car. Check it out in the video below.
Strain wave gears have many applications, especially in robotic arms and legs – very compact versions with the built-in motor would be perfect here. If you’re having trouble visualizing how they work, maybe a Lego version will clear things up.