OpenArm's Open-Source Robot Arm Costs $6,500 a Pair
Hardware / explainer
OpenArm's Open-Source Robot Arm Costs $6,500 a Pair
Enactic's 7-DOF arm has been shipping since July 2025, but a Hacker News post about it drew 202 points this month, more attention than the hardware has gotten in over a year.
What OpenArm actually is
OpenArm is a 7-degree-of-freedom robot arm whose hardware design, firmware and control software are published under open licenses, Apache 2.0 for the software and CERN-OHL-S-2.0 for the mechanical CAD, by Enactic, a Tokyo robotics company founded by chief executive Hiroto Yamamoto as a spinout of Reazon Holdings' speech-recognition lab, according to The Dynamics. Two arms make a bimanual, 16-degree-of-freedom system with grippers on each end, and Enactic sells a complete pair for $6,500, according to the project's GitHub repository, which the company keeps as the canonical build documentation rather than a marketing page. Each arm weighs 5.5 kg, reaches 606 mm and drives its seven joints with Damiao quasi-direct-drive motors, a motor type chosen because it lets the arm be pushed by hand without fighting back, the property roboticists call backdrivability.
That matters more than a spec sheet number because OpenArm is built for teleoperation: a person moves the arm, or a lighter 1.7 kg leader version of it, and the motion and force feed back through the joints into a dataset a model can later learn from. The arm can hold 6 kg for a three-second movement or 4.1 kg for a full minute, and a 1 kHz CAN-FD control loop running on STM32 microcontrollers is what keeps that force feedback fast enough to feel responsive rather than laggy.
What the $6,500 actually buys, and what it does not
Enactic's own pricing runs three ways: the $6,500 bimanual pair, a $6,200 fixture called OpenArm Cell that standardizes lighting, camera angle and arm position so results are comparable across different labs' benchmarks, and a $2,599 wearable leader arm called OpenArm KER, a motorless, 70-percent-scale version worn to record human motion without a robot attached at all, according to coverage from The Dynamics. None of those figures include a compute box, a camera rig beyond the gripper's built-in one, or the GPU needed to actually train on the data OpenArm collects.
What the license buys is more unusual than the price. CERN-OHL-S-2.0 is a share-alike hardware license, meaning a company that modifies OpenArm's mechanical design and sells the result has to publish those modifications too, and Apache 2.0 on the software side carries no such obligation and permits closed commercial use outright. That split, open hardware with a copyleft catch, open software without one, is Enactic's own choice, not a default any open-source robotics project has to make.
The reproducibility problem OpenArm Cell is aimed at
Enactic's pitch for OpenArm Cell is specific: a robotics paper's results are hard to reproduce because a different light source changes what a camera sees and a different camera angle changes the geometry a model has to interpret, so two labs running the same arm can still get different numbers, a framing The Dynamics reported from the company. Standardizing the rig, not just the arm, is the fix Enactic is selling, and it is a narrower and more checkable claim than most open-source robotics marketing: a lab can verify whether its own Cell setup matches another lab's by comparing the fixed variables directly, rather than trusting a benchmark number on faith.
Enactic backs that pitch with integration work rather than just documentation. Hugging Face's LeRobot library added native OpenArm support in version 0.5.0 in March 2026, and Nvidia's Isaac GR00T N1 foundation model has been deployed on the hardware under OpenArm's own v0.3 software release, giving labs a model to run on day one instead of writing a driver first.
Why it is on Hacker News now
OpenArm shipped its first beta in February 2025, launched formally the same day Enactic itself was founded, July 23, 2025, and reached its current OpenArm 2.0 hardware revision in May 2026. None of that is new. What changed is that a Hacker News post titled "OpenArm: An open-source 7DOF humanoid arm," linking straight to the GitHub repository, collected 202 points on Sept. 13, according to Hacker News' own search API, more attention in one day than the project appears to have drawn since its launch. Neither Enactic nor the thread itself gives a reason for the timing; there is no new release, funding announcement or partnership dated to that week. The likeliest explanation is simply that humanoid and teleoperation hardware is drawing more attention generally this month, and OpenArm's repository, sitting at 3,300 stars and 365 forks, was already positioned to catch it.
The arm sits in the same supply chain as companies building the data pipelines that teach robots to use hardware like it. XDOF, which was in talks for a Series B in September, builds the collection tools and annotation systems that turn teleoperation sessions, the exact workflow OpenArm's leader arm is built for, into training data. Whether an open-source arm at Enactic's price point changes who can supply that data, rather than just who can buy a robot, is the question the current attention has not yet answered. A viral GitHub repository is not adoption by itself, a lesson OpenClaw's own trajectory has already made plain on the software side; stars measure attention, not the number of labs actually running OpenArm Cells today, and Enactic has not published that count.
| OpenArm product | Price | What it is |
|---|---|---|
| OpenArm 2.0 bimanual pair | $6,500 | Two 7-DOF arms with grippers, 16 DOF total |
| OpenArm Cell | $6,200 | Standardized lighting, camera and mounting fixture |
| OpenArm KER | $2,599 | 1.7 kg motorless wearable leader arm, 70% scale |
Source: Enactic, via The Dynamics, May 2026.
Sources
- 02OpenArm
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