Teen Engineers a 3D-Printed Cycloidal Gearbox with a Custom Python Generator

A self-described 15-year-old aspiring engineer has open-sourced a working cycloidal gearbox alongside the Python script that generates its geometry. Cycloidal drives achieve high reduction ratios in a compact package by having a lobed rotor wobble against a ring of pins, and the project reproduces that mechanism using parts a hobbyist can 3D print. The generator, built to run as a Fusion 360 script, is driven by the parametric equations for a cycloidal disc drawn from a SolidWorks tutorial, with the output disc turning opposite the input shaft at a ratio of 1:(N−1).

The build log is a candid account of iterating against real-world constraints. Version 1 was a hand-cranked 1:9 unit meant only to validate the generator’s math. Version 2 tried to shrink the drive into a NEMA 17 stepper’s footprint but failed — the tight tolerances a small cycloidal disc demands were beyond what consumer 3D printing could hold. Version 3 traded compactness for a larger footprint that loosened those tolerances, yielding the first fully functional gearbox capable of running on a NEMA 17.

Beyond the mechanism itself, the project is a tidy example of parametric, code-driven CAD: rather than hand-modeling gear profiles, the author encodes the geometry once and regenerates it for any tooth count. It’s a reminder of how accessible sophisticated mechanical design has become when scripting, low-cost printers, and shared reference material meet a motivated builder.