Koch v1.1 Leader-Follower Robot Arm Pair

A pair of small 6-axis robot arms for teaching robots by demonstration. You move the leader arm by hand and the follower copies it in real time. Record those demonstrations and train a policy with Hugging Face LeRobot so the follower can repeat the task on its own.

Updated for modern use: one combined parts list for both arms, a clear power setup and a rewritten print and assembly guide.

What you build

• Follower arm: 2 x XL430 for the shoulder and elbow, 4 x XL330 for base, wrist and gripper
• Leader arm: 6 x low-geared XL330, light enough to move by hand, with a trigger-style gripper handle
• An optional leader platform so the follower can reach objects on the table surface

Files

• 14 print-ready STL files: 7 for the leader including the platform, 7 for the follower
• Build guide PDF: printing, servo setup, assembly, power and wiring, calibration and teleoperation
• Bill of Material PDF with quantities, notes and a shop link for every part

Print settings

PLA+, PETG or ABS at 0.2 mm layers or finer, 0.4 mm nozzle, about 30% infill. A glue stick on the bed helps. The leader frame and the follower idlers are bought as ROBOTIS FPX330-S101 and HN11-I101 sets from ROBOTIS; they are not printed and are not in the shop list.

Electronics

• 12 Dynamixel servos: 2 x XL430-W250-T, 4 x XL330-M288-T, 6 x XL330-M077-T
• Two USB bus servo driver boards
• 12 V and 5 V power supplies and a 12 V to 5 V step-down for the follower XL330 servos

Bill of Material

Every part you need to buy, with quantities, notes and shop links, is in the Bill of Material PDF in the files of this model.

Software

Both arms run with Hugging Face LeRobot on your computer. Give each servo its ID, calibrate both arms, then start teleoperation and record episodes to train a policy.

Full build guide and source

The build guide, source and all project files: https://github.com/ToolKnox/hawkridge-koch-v1-1-low-cost-robot-arm (Code > Download ZIP).

Safety

Never put 12 V on the XL330 servos; measure the step-down output before you connect them. Clamp both bases to the table and keep fingers clear of the follower gripper while it is powered.