6-DOF Robot Arm

Overview

A six-axis robotic arm built as my own variation of the BCN3D Moveo, the open-source arm released by BCN3D Technologies. Rather than printing the published parts as they are, I reworked the design in CAD, the articulations, bearing stacks, and drive layout, and sourced the entire bill of materials from US suppliers. I plan on adding and implementing an LLM, camera, and sound sensor so the arm would be able to move on its own, recognize objects, and listen to voice commands.

Architecture

Six stepper motors across five articulations, plus a servo gripper:

• Shoulder — a pair of NEMA 23 steppers (SM57HT112-3004A, 3 A, 28 kg·cm) driving the heaviest joint together through T5 belts, so the load is shared rather than carried by one oversized motor.

• Elbow — a NEMA 17 behind a 5:1 planetary gearbox (17HS19-1684S-PG5), giving 2 N·m at a 0.35° step.

• Forearm and wrist — NEMA 17s (SM42HT47-1684 at 1.6 A, SM42HT33-1334 at 1.33 A) and a NEMA 14 (SM35HT36-1004A) where the payload is lightest.

• Gripper — a 180° servo at 13 kg·cm driving a printed gear-and-pivot jaw.

Motion hardware

Every joint runs on ball bearings sized to its load, 608ZZ, 625ZZ, 624ZZ and 623ZZ, thirty in total — with oilite bushings where a plain bearing is enough. Power reaches the joints through a 16 mm T5 timing belt on 14- and 10-tooth pulleys, with chrome steel shafts and a rigid 5→8 mm coupling at the gearbox output. Brass heat-set inserts in M3 and M4 take every threaded fastener, so the printed parts can be assembled and taken apart repeatedly without stripping the plastic.

Electronics

An Arduino Mega 2560 with a RAMPS 1.4 shield and six TB6560 drivers, running from a 24 V 320 W supply with a 24→12 V converter for logic and cooling. The driver stack sits in a printed enclosure with two axial fans.

Printed structure

Around thirty printed parts: four articulations, the gripper assembly (top and bottom plates, pivot arm, left and right jaws, idler and servo gears), the electronics box and driver mounts, a cover for each joint, and feet for the 550 × 550 mm base.