Compact 20:1 Cycloidal Gearbox for Robots

Compact 20:1 Cycloidal Gearbox

This is a compact 3D-printable cycloidal gearbox with a 20:1 reduction ratio, designed for a NEMA 17 stepper motor.

The gearbox uses two cycloidal discs running with a phase offset to provide smoother operation, better load distribution, and reduced vibration.

The output is transferred through 8 output pins to the output disc. A separate eccentric bushing and bearing arrangement supports and guides the cycloidal discs, while the compact housing keeps the overall dimensions of the gearbox small.

Main Features

• 20:1 reduction ratio

• Designed for NEMA 17 stepper motors

• Dual cycloidal disc design

• Ball-bearing-supported eccentric drive

• Compact construction

• Mostly 3D-printable parts

• Suitable for robotics, actuators, and experimental mechanical projects

This is an experimental DIY gearbox and is still being tested and improved. Depending on your printer, material, and print settings, some tolerances may require slight adjustment.

You need:

• 1× NEMA 17 stepper motor

• 6× 6801RS ball bearings

• 15× Ø5 mm precision steel balls

• 7× M3 heat-set threaded inserts

• 7× M3x10 countersunk head screws

• 4× M5 heat-set threaded inserts

• 4× M3×12 cylinder head screws

• 4× M5×16 or M5×20 cylinder head screws
  

Print Instructions

Parts to Print

• 1× Housing

• 1× Ball Cage

• 1× Bearing Adapter

• 1× Cycloidal Disc 1

• 1× Cycloidal Disc 2

• 1× Eccentric Bushing

• 1× Main Eccentric

• 1× Output Disc

• 2× Spacer Rings

• 1× Top Cover

Recommended Print Settings

• Material: PETG

• Layer height: 0.2 mm

• Nozzle diameter: 0.4 mm

• Infill: 15%

• Supports: Yes

Other print settings can be adjusted according to your printer and personal preferences.

If you build one, I’d love to see your make and hear how it performs!