How to build Yale OpenHand Project
4-DoF robot gripper · Intermediate
Build a Yale OpenHand: 3D-printed underactuated tendon hands from Yale's GRAB Lab, with cast urethane flexure joints and Dynamixel actuators.
Some soldering, calibration and Linux comfort needed.
Our estimate, part-time
Price the BOM yourself
CC-BY-NC-3.0 · non-commercial
What is Yale OpenHand Project?
The Yale OpenHand Project, from Aaron Dollar's GRAB Lab, is a family of open robot hands built by rapid prototyping. Rather than one design, the repo holds many: the single-actuator four-finger Model T, the two-finger T42, the three-finger Model O, the finger-gaiting Model Q, the variable-friction VF, the Stewart Hand and newer designs like the camera-equipped F3.
Almost all of them use underactuated, tendon-driven fingers. Fewer motors than joints means the fingers wrap around objects on their own, without sensors or complex control, which makes them sturdy and cheap.
The lab's trick is Hybrid Deposition Manufacturing: print a finger with cavities, then cast urethane into them to form flexure joints and fingerpads in one monolithic piece. That cuts fasteners and survives knocks.
Yale OpenHand Project specifications
- Designs
- Model T, T42, O, Q, VF, W, Stewart, F3 and more
- Actuators
- Dynamixel servos (XM430, XL-320 on some models)
- Joints
- Cast urethane flexures + pivots
- CAD
- SolidWorks with STL exports
- License
- CC BY-NC 3.0
Figures as published by the project. See Sources below.
Bill of materials
| Part | Qty | Notes |
|---|---|---|
| Dynamixel servos | — | 1–4 depending on the model; F3 uses 2× XM430 |
| Spectra tendon line | — | |
| Smooth-On PMC-780 urethane and Dragon Skin 10 | — | Flexures and pads |
| Dowel pins, bearings, standoffs, bolts and heat-set inserts | — | |
| Printed base, motor fixtures, finger molds and cases | — | |
| Logitech C920 webcam | — | Model F3 only |
Where's the full bill of materials?
The full BOM, with exact quantities and vendors, lives in the project's own files. Prices change often, so treat Not published as a ballpark. Start at the project repository.
Tools you'll need
- FDM printer
- Urethane casting supplies and mold release
- SolidWorks
- Hex and Phillips drivers
Step-by-step build overview
Electronics & wiring overview
Dynamixel servos chain on one bus to a USB adapter; the number of servos depends on the model.
Software
The project ships its own firmware and control code. See the repository for setup.
Control code and a ROS node for Models T, T42 and O are in the lab's openhand_node repository.
Tips from the bench
- ☕ Open SolidWorks assemblies with external references set to load all, or you'll get missing-part errors.
- ☕ Many assemblies use configurations to switch finger options; check them before exporting STLs.
Yale OpenHand Project FAQ
Which Yale OpenHand should I build first?
Model T or T42 are the simplest and best supported by the control code.
What does underactuated mean here?
Each finger has more joints than motors, so it conforms to objects passively.
Can I sell OpenHand builds?
Not without permission; the designs are CC BY-NC 3.0.
Sources
Written by Bots n' Beans from the project's own documentation. Check the sources for the latest revision before you buy parts.
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