OpenArm is Enactic's open-source humanoid arm platform for physical AI research: a pair of human-sized 7-DOF arms on a pedestal, made to be built, repaired and modified by labs, and used for teleoperation, dataset collection and policy learning. OpenArm 2.0 is the second generation, released in 2026, with a more compact gripper that carries its own camera and a pedestal made from MiSUMi aluminium frame.

Arms

Each arm has seven revolute joints on DAMIAO motors, all on CAN-FD:

Joint	Motor	Peak torque	Range (right arm)
1 shoulder pitch	DM-J8009P-2EC	40 N m	-80 to 200 deg
2 shoulder roll	DM-J8009P-2EC	40 N m	-10 to 190 deg
3 upper-arm yaw	DM-J4340P-2EC	27 N m	-90 to 90 deg
4 elbow	DM-J4340-2EC	27 N m	0 to 140 deg
5 forearm yaw	DM-J4310-2EC V1.1	7 N m	-90 to 90 deg
6 wrist pitch	DM-J4310-2EC V1.1	7 N m	-45 to 45 deg
7 wrist roll	DM-J4310-2EC V1.1	7 N m	-90 to 90 deg

The left arm is the mirror image. The structure is MiSUMi meviy machined parts under covers, and each joint has a mechanical stop. The wrist pitch motor sits in the forearm and drives the joint through a parallelogram linkage. Enactic rates the arm at 4.1 kg nominal and 6.0 kg peak payload (including the end effector); the URDF gives 6.1 kg per arm with its gripper.

Gripper

A pinch gripper with two fingers turned by one DM-J4310 through a pair of spur gears, with an Arducam B0495 global-shutter USB camera inside the case for in-hand vision. The fingers are made to be swapped for task-specific designs.

Pedestal

A 60 x 60 mm aluminium extrusion column on a base plate with M6 taps, with the arms' shoulders 697 mm above the plate and a chest cover between them. An optional head camera (ZED mini) mounts on top.

Electronics and software

The motors run at 24 V; each arm is one CAN-FD bus (1 Mbps nominal, 5 Mbps data) behind a USB-CAN-FD adapter. Enactic publishes a C++/Python CAN library, ROS 2 control and MoveIt configurations, a MuJoCo model, a URDF, VR teleoperation and a leader device (OpenArm KER) for data collection, plus dora-rs nodes for recording and policy inference.

In this project

The parts are the official 2.0.0 STEP, split by URDF link and colour (covers, aluminium, bearings and motor bodies as separate parts) and placed unchanged: the STEP is already in the URDF zero pose (motor axes on the joint axes within 0.01 mm). Joints, limits, masses and inertias come from the openarm_description v2 URDF. Each joint has a position servo at the motor's peak torque with the repository's real-robot gains and gravity compensation; the second finger follows the first through the gears, and the wrist pitch linkage (crank and coupler rod) follows joint 6. The demo reaches forward with both arms, grasps, and hands an object from the right gripper to the left.

License

CAD (hardware) under CERN-OHL-S-2.0, software (URDF, MuJoCo model, control code) under Apache-2.0. Copyright 2025 Enactic, Inc. Source: https://github.com/enactic/openarm_hardware (release 2.0.0) and https://github.com/enactic/openarm.

Modification notice (CERN-OHL-S-2.0 section 3.3): the CAD shown here was modified by flomotion on 2026-10-16. The assembly STEP was split into one file per robot link and colour, rotated from Y-up to the URDF's Z-up frame, screws, nuts and washers were removed, and B-spline faces were re-approximated within 0.1 mm to reduce file size. The modified CAD remains under CERN-OHL-S-2.0; the complete original source is at the links above.