Most guides are from 2013-2019, several call for discontinued Dynamixels, and editable CAD needs SolidWorks.
A family of open-source underactuated grippers from Yale's GRAB Lab, including the two-finger Model T42 and the three-finger Model O. Fingers are 3D-printed with cast urethane flexure joints and pads (Hybrid Deposition Manufacturing) and are pulled closed by tendons from Dynamixel servos. Parametric SolidWorks CAD lets link lengths and transmission ratios be changed.
At a glance
| Parts cost | $1,400 estimated How Estimated for this page from current retail prices (2026-10-02) of the parts in the project parts list source ↗ Build priced Model O v2.0 (XM430) with pivot-flexure fingers Not included 3D printing, tools, shipping, tax; Dynamixel USB interface and power supply (not in the parts list) |
|---|---|
| Difficulty | 3/5 Intermediate · Printing is simple, but casting urethane flexures and pads is an extra skill, and CAD edits need SolidWorks. |
| Build time | Not stated |
| Tools needed | 3D printer, urethane casting (mix and pour into printed or thin-wall molds), SolidWorks to edit the parametric CAD |
| Motors | Model O 4x Dynamixel XM430 (v2) or RX-28/MX-28 (v1); Model T42 2x Dynamixel RX/MX-28 or Power HD 1501MG |
| Controller | PC with ROS openhand_node over Dynamixel serial |
| Sensors | Servo feedback only |
| Published | ✓ Parts list✓ CAD/STL✓ Assembly guide✗ Wiring✓ Software✗ Video Project website with per-model PDF assembly guides, finger casting and CAD guides + GitHub repo |
| Activity | Last update 2025-03-25 · 236 GitHub stars · 114 forks; low issue activity |
| Kits | None (Model O is a derivative of RightHand Robotics' commercial ReFlex Hand) |
Licenses
The design license is non-commercial. Building one for personal, educational or research use is allowed, but selling builds, parts or kits is not.
| Design files | CC BY-NC 3.0 source ↗ |
|---|---|
| Code | MIT (openhand_node ROS driver) source ↗ |
| Documentation | CC BY-NC 3.0 (website footer) source ↗ |
Builder notes
Practical points from the project's issue tracker, forum and docs, each linked to its source.
- The PMC-780 urethane for the flexure joints must be the DRY version. The WET version is for concrete molding. source ↗
- Source CAD is SolidWorks only and relies on design tables and external references. One builder could not get parameter changes to propagate in SolidWorks 2022, and others had to convert the Sphinx hand themselves to get STL/OBJ files. source ↗
- The parts lists name specific McMaster pins and screws but say they are just what the lab used, not an optimized list, so substitutions are expected. source ↗
- Most guides date from 2013-2015. Only the Model O got a 2019 update for current XM430 servos, and older guides call for discontinued RX-28/MX-28 motors. source ↗
Other hands plans
- LEAP Hand · $1,800 (2023) · difficulty 2/5
- AmazingHand · $140 · 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
- DexHand (The Robot Studio) · $300 (2023) · difficulty 4/5