Same rig, same 300 g hanging from the gripper, dial indicator in the same spot.
• SO-ARM 101 — 7.5 mm • SO-ARM 102 — 3.9 mm
About half the deflection. Both arms are built with printed servo dummies, so this is the structure being compared, not the motors. Parts printed at 25 % infill.
SO-ARM 102 goes open source in the next few weeks.
What's new: - A parallel gripper: the jaws stay parallel through the whole stroke instead of pivoting around the object as they close. - PET-CF instead of PLA+ for a much stiffer frame. - A topology-optimized structure. - Wider joint rotation and folding range. - STS3250 servos on the first shoulder joint.
Compared with the SO-ARM 101, that adds up to 2.5x the payload, roughly 2x better positioning accuracy, roughly 1.6x the movement speed, and about 36 mm more reach.
It runs on Hugging Face LeRobot, so the same tooling, training pipeline and tutorials for the SO-ARM 101 work on it from day one.
Hackernoon published our article on how semi-SCARA kinematics and mechanical design choices reduce the cost of a 6DOF manipulator without relying on expensive actuators.
"An open-source test stand for backlash measurement in low-cost UART servo motors" presents a ~$100 automated platform for measuring backlash in compact serial bus servos — no dial indicators, no probe contact force, fully scripted and repeatable.
All CAD files, control software, and analysis tools are open source.
We added multi-simulator support for our parallel gripper on the SO-ARM 100/101 arm. One URDF, one launch file, five physics engines: Gazebo, MuJoCo, Webots, CoppeliaSim, Isaac Sim.
The ROS2 package includes xacro descriptions, joint trajectory controllers, robot state publisher, and parameterized hardware interfaces for each simulator.
We have received the majority of components for our first small commercial batch of SO-ARM101 robotic arms. Feetech STS3250 servo drives, parallel gripper, and depth camera.
Progress update on our Robonine mobile robotic platform. We've wired up the full electronics stack - Raspberry Pi, motor controllers, and a camera module - and added Bluetooth joystick and keyboard control with WiFi-based management. A 7 kg counterweight keeps the platform stable. Powered by a powerbank and ready to roll.
Robonine just published a new article! Mechanical backlash is a common limitation in servo-driven robotic joints. In this experiment, paired Feetech STS3215 servos are used with a small opposing preload to eliminate gearbox play, significantly improving positional stability and motion precision in robotic manipulators.
Testing a parallel gripper with a MaixSense-A010 ToF depth camera (100-point sensor) and pressure sensors.
By combining depth data with force feedback, the gripper closes only when the object is in a graspable position. If the object slips or leaves the grasp zone before closing, the system can automatically retry — as shown in the video.
We tested our 3D-printed parallel gripper for the SO-ARM100/101 robotic platform, successfully handling a 1.5 kg payload. The gripper features a 100.5mm full stroke and ±0.05mm repeatability — all for around $76 in parts and 30 minutes of assembly.
Our colleague Vladimir Osipov equipped the SO-ARM100 parallel gripper with FSR402 force sensors to enable delicate object handling with real-time grip force feedback. The sensor detects forces as low as 0.2N, while the target grip force is tuned per object — around 5N for a cherry tomato — to account for the limited torque precision of STS3215 servos and prevent slipping. This allows the gripper to grasp soft objects gently, detect slippage, and automatically retry the grip.
We stress-test the FEETECH STS3215: real backlash (0.87° measured vs spec), repeatability, speed accuracy, stall torque above rating, and thermal overload behavior under continuous load. Practical implications for robot arms and grippers.
Robonine (Educational Robotics) completed a structural optimization of our 6-DOF robotic manipulator after a structural optimization study. By increasing structural rigidity through topology optimization and design refinement, we reduced end-effector deflection by over 60% (from ~1.05 mm to ~0.41 mm) and improved motion stability. The final configuration delivers higher precision and reliability for industrial applications.
Our engineer Alan from https://robonine.com/ (Educational Robotics) integrated Feetech STS3250 and STS3215 servo motors into the prototype and completed the first test run of a 6-DOF semi-SCARA manipulator.
During motion, the structure demonstrates high stiffness with no visible backlash or mechanical play. The kinematic chain remains stable throughout the test trajectory, confirming the rigidity of the mechanical design and joint assembly.
The next stage includes full assembly with all actuators operating in backlash compensation mode, followed by quantitative measurement of positioning accuracy and repeatability.
Our engineer Alan from https://robonine.com team has assembled the mechanical frame of our 6-DoF manipulator prototype - without servo motors for now. At this stage we are evaluating how easy the structure is to assemble, checking for any mechanical play, and validating the kinematics.
Good news: the structure feels solid and Alan reports no detectable backlash so far.
We tested the maximum dynamic payload of the SO-ARM101 with our parallel gripper and a base servo replaced by a Feetech STS3250. The maximum load before failure was 630 g, at which point the Feetech STS3215 in joint 3 failed — its large brass output gear was completely worn down.
The Feetech STS3250 in the base with a metal gear train withstood a significantly higher load.
Next week, we will release full documentation for the SO ARM 101 with a parallel gripper, featuring leader and follower arms and support for widely used stereo cameras.
Update: Our engineer Alan has received a batch of components for the manipulator assemblies — including clamps and metal bracket parts. Prototype assembly is planned for the beginning of next year.
