Every part of
a robot arm,
as a file.

RB-6 is a six-axis desktop robot arm with a 33:1 cycloidal reducer of our own design in every joint. You download the files for the printed parts and make them on your own printer.

01 · Cycloidal reducer

Cycloidal drive.

Two discs running 180° out of phase, an eccentric shaft and output pins. 33:1 reduction, low backlash, one module.

02 · Desktop manufacturing

With standard parts.

The discs are printed in PETG, the housing and cover in PLA. Bearings and screws are off-the-shelf; no machining required.

03 · One module, six joints

The same module in every joint.

The reducer mounts directly on a NEMA17 motor; all six joints of the arm use the same module.

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Cycloidal reducer · 33:1

More torque in the same volume.

In a cycloidal drive the load is shared by many pins at once instead of a single tooth. Compared with a planetary gear, it offers lower backlash and quieter operation.

Cycloidal reducer mounted on a NEMA17 motor, cross-section
Cross-section · mounts directly on a NEMA17
Reduction ratio
33:1One module with a NEMA17 input
Robot arm
6axesThe same reducer in every joint
STL files
Print-ready.

Support-free orientation; tested at 0.2 mm layers and 30% infill. Discs in PETG, other parts in PLA.

CAD source
Editable.

The STL + STEP option includes the STEP file, so you can adapt the dimensions to your own motor.

J1J2J3 J4J5J6 RB-6 · 6 DOF · UR-TYPE J2 ∥ J3 ∥ J4 · WRIST OFFSET 165.5 MM
RB-6 · 6-axis robot arm

Six axes, closed-loop drive.

Every joint has a NEMA17 motor and a 33:1 cycloidal reducer. The drivers are MKS SERVO42C and the controller is a custom board on an Arduino Mega. Kinematics are computed on the PC; the board only generates steps and reads position feedback.

  • Forward and inverse kinematicsA numerical solution based on the DH model, the Jacobian and damped least squares (DLS); it passed an acceptance test of 5,000 configurations.
  • Trajectory planningPoint-to-point, linear and jog motions with a trapezoidal velocity profile. Moves that exceed a limit are rejected.
  • Desktop appA live state stream and a three.js 3D model; ships as a Windows installer.
  • Hardware emergency stopAn NC relay independent of the software; a single 24 V / 15 A supply line.
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