Open-Source Arm Puts Robotics Within Reach

In November 2017, we showed you [Chris Annin]’s open-source 6-DOF robot arm. Since then he’s been improving the arm and making it more accessible for anyone who doesn’t get to play with industrial robots all day at work. The biggest improvement is that AR2 had a closed-loop control system, and AR3 is open-loop. If something bumps the arm or it crashes, the bot will recover its previous position automatically. It also auto-calibrates itself using limit switches.

AR3 is designed to be milled from aluminium or entirely 3D printed. The motors and encoders are controlled with a Teensy 3.5, while an Arduino Mega handles I/O, the grippers, and the servos. In the demo video after the break, [Chris] shows off AR3’s impressive control after a brief robotic ballet in which two AR3s move in hypnotizing unison.

[Chris] set up a site with the code, his control software, and all the STL files. He also has tutorial videos for programming and calibrating, and wrote an extremely detailed assembly manual. Between the site and the community already in place from AR2, anyone with enough time, money and determination could probably build one. Check out [Chris]’ playlist of AR2 builds — people are using them for photography, welding, and serving ice cream. Did you build an AR2? The good news is that AR3 is completely backward-compatible.

The AR3’s grippers work well, as you’ll see in the video. If you need a softer touch, try emulating an octopus tentacle.

Thanks for the tip, [Andrew]!

16 thoughts on “Open-Source Arm Puts Robotics Within Reach

    1. Indeed.
      @ Hackaday: you goofed up, please correct:
      Quote @ 2:10:
      “The main difference between the AR2 and AR3 is that the AR2 was open loop, the AR3 is now closed loop, meaning that I’ve added encoders to each axis”

  1. This is absolutely not open source. I’ve only looked at the AR3 portion but the software has this condition on it:

    * Selling robots, robot parts, or any versions of robots or software based on this
    work is strictly prohibited.

    And the STL files have this condition on them:

    * You may not sell, market, barter or profit from parts created directly
    or indirectly from any of these models made out of any material.

    Making source files available to look at does not make them open. “Open source” has a commonly accepted definition of allowing commercial use (see

    This is not the fault of the OP (Kristina Panos) as the author of the project clearly misrepresents their project as being open source when it absolutely isn’t.

    1. Good catch. That’s truly a shame, and it looks to be snuck in for monetary gain if any large player decides to profit off the design. I understand that maybe he wanted to prevent abuse, but it tarnishes the meaning of open source.

  2. I really appreciate the project even if I can’t sell copies of it for a profit. The robot arm with 6 or7 degrees of freedom is not something within reach (pun acknowledged but not intentional). Having a learning option like this is invaluable if you want to get experience in an expensive field, or a tough project for an advanced kid.
    Even with the mirepresentation, I love this project.

  3. That’s a professional work, that, even if the documentation is complete (the source are present), is not an open source since you can’t distribute them. In all cases, the work is impressive and making such an arm for $1300 is very valuable.

  4. I confirmed with the developer on youtube that this project is NOT OPEN SOURCE and that he is aware of it. It
    is his prerogative to release it under any license he likes, and this is better than not releasing it at all, but it is NOT open source and the article name should be corrected.

  5. While possible, it’s impractical, due to a combination of axis stacking (each joint has play in it, and will have error to correct for, and having them stacked together makes the effect multiplicative, as all of these joints are rotary and provide a lever arm), and low damping mass to dissipate vibration. In industry you’ll notice that despite the much higher quality of the components involved, that robots are largely limited to light duty machining and deburring, and that six axis machining centers will usually have the axis in multiple stacks, such as a swivel on the head and a trunnion holding the workpiece, to reduce the multiplicative effects on the ultimate error, and simplify the hardware and wiring.

  6. Sorry, this was in reply to the six/seven axis engraving/routing comment. This project is on the whole, really cool. I’ve worked with actual industrial robots, and it’s better to have a system that can actually be taken apart, and that the drawings and other technical information is freely available to teach students how they work, unlike those industrial robots. I just don’t think it’s practical to use most any robotic arm for machining operations.

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