Optimizing a Strain Wave Gearbox for 3D Printing

Strain wave gearboxes, also known as harmonic gearing, are a specialized gearing often used in robotics. Due to their relative simplicity–consisting of only three main parts–and their unique properties, they are often used in hobbyist multi-axis robot arms. 3D printing these gearboxes, however, proves difficult due to the presence of the flex spline, the primary functional part in strain wave gearboxes, as the flex spline needs to be able to consistently deform over many cycles. Especially with a rather rigid plastic such as PLA, creating a flexible and durable enough flex spline can prove difficult. In most hobbyist designs, the engineer chooses a flexible plastic such as TPU due to its ease of use in designing a flexible part and employs the use of other materials such as ball bearings in order to improve functionality. This project attempted to print the entire strain wave gearbox out of entirely PLA due to its universality.