The micro servos are weak and the designer says the hand has not been tested on long or forceful grasping tasks.
A low-cost, fully 3D-printed four-finger hand from Pollen Robotics, designed for the wrist of the Reachy 2 humanoid but adaptable to other arms. Each finger is moved by two tiny Feetech serial servos through a parallel linkage, giving 8 DoF with every actuator inside the palm. It can be driven from Python with a serial bus board or from an Arduino.
At a glance
| Parts cost | $140 parts list · Sum of the prices in the project's parts list, 128 EUR source ↗ |
|---|---|
| Difficulty | 2/5 Easy · Small parts count and cheap servos, but each ball-joint rod must be adjusted by hand and every finger calibrated. |
| Build time | Not stated |
| Tools needed | 3D printer (PLA plus flexible shells; print guide PDF), small screwdrivers, ball-joint rods adjusted by hand |
| Motors | 8 Feetech SCS0009 micro serial servos (STS3032 in the Enhanced version) |
| Controller | Waveshare serial bus servo driver + PC, or Arduino Mega + Feetech TTLinker; separate 5 V supply |
| Sensors | Servo position, torque and temperature feedback |
| Published | ✓ Parts list✓ CAD/STL✓ Assembly guide✓ Wiring✓ Software✗ Video GitHub README + assembly and print-tips PDFs + Google Sheets parts list + public Onshape document |
| Activity | Last update 2026-04-03 · 2,405 GitHub stars · Pollen Robotics Discord channel; 280 forks; community add-ons such as a GUI and an SO-ARM mount |
| Kits | Kits sold by Seeed Studio and WowRobo |
Licenses
| Design files | CC BY 4.0 (mechanical design) source ↗ |
|---|---|
| Code | Apache-2.0 source ↗ |
| Documentation | Apache-2.0 (project-wide statement; PDFs not separately licensed) source ↗ |
Builder notes
Practical points from the project's issue tracker, forum and docs, each linked to its source.
- Several parts list links went stale or pointed to the wrong parts soon after launch, including a servo link to a different model. Pollen confirmed only the Feetech SCS0009 works with the current code, though one builder got cheaper PWM 9 g servos working with custom code. source ↗
- The Waveshare driver board in the parts list takes 9-12.6 V, while the SCS0009 servos want about 4-7.4 V, so a separate regulated supply for the servos is needed. source ↗
- The Onshape document was originally view-only. It is now public so it can be copied and edited, and the full Finger and Right Hand assemblies include the rods and ball joints missing from the STEP export. source ↗
- An Enhanced branch swaps in stronger, backdrivable Feetech STS3032 servos with a separate parts list, at a higher cost. source ↗
- The designer notes it has not been tested on long or demanding grasping tasks, and real joint angles drift from theory because of print tolerances and hand-adjusted rods. source ↗
Other hands plans
- LEAP Hand · $1,800 (2023) · difficulty 2/5
- UMI gripper (Universal Manipulation Interface) · $370 (2024) · difficulty 2/5
- RUKA hand · $1,300 · difficulty 3/5
- Aero Hand Open · $320 · difficulty 3/5
- ORCA Hand · $2,000 · difficulty 4/5
- YUBI glove and gripper (Toyota) · $550–$750 · difficulty 4/5
- Yale OpenHand (Model T42 / Model O) · $1,400 · difficulty 3/5
- DexHand (The Robot Studio) · $300 (2023) · difficulty 4/5