A 3D-Printable Robotic Arm That Can Do Real Work

Do a quick search on Printables, Hackster, or any community site and you’ll find dozens of open source 3D-printable robotic arms. But the fact is that most of them are little more than educational toys; they’re great for learning about robotic principles, but they aren’t capable of doing real work. For a robotic arm to perform useful tasks, it needs precision, accuracy, repeatability, and strength. The components needed to achieve that are expensive, but Pavel Surynek’s Real Robot One cuts costs with 3D-printed parts and clever engineering.

Closed-loop feedback is necessary for a robotic arm to perform well. Open-loop robots, including most of the low-cost projects we see, do not contain any hardware to tell the controller the real-world positions of the joints. They rely entirely on the assumption that each joint will be in the position that the controller sets it to, which doesn’t account for unpredictable backlash in gears, skipped motor steps, sag/flex in the arm, and so on. Closed-loop robots utilize sensors (encoders, in this case) that tell the controller the exact rotational angle of each joint. That doesn’t account for sag/flex, which would require additional feedback hardware, but it is a huge improvement.

This robot, dubbed “RR1 (Real Robot One),” has an encoder in every joint. Like most robotic arms, stepper motors rotate the joints. But RR1 is unique in that each motor has a 3D-printed planetary gearbox to increase torque and motor output resolution. Those help the robotic arm lift quite a bit of weight and move with precision. RR1 has six joints, so it contains six of those gearboxes. The final degree of freedom is the end effector, which is a servo-driven gripper.

An Arduino Due development board controls the stepper motors and monitors the encoders. But it doesn’t handle the more complicated inverse kinematic calculations. That’s the job of the Real Box One (RB1) control computer, though details are lacking on RB1’s specs.

Surynek says that Real Robot One has a reach of about 80cm and payload of 2kg. The robotic arm itself weighs 8kg and the RB1 weighs another 8kg. Surynek doesn’t provide repeatability specifications, but he’s already working on a rev. 2 that will implement lessons learned so far. We’re hoping we’ll get full details (and design files) when that revision is ready.