About Model T

The Model T is the initial released design of the Yale OpenHand Project, based on the original SDM Hand. It consists of four underactuated fingers with compliant flexure joints, driven by a single actuator through a pulley tree differential. During grasp acquisition, each finger will continue to move until the links make contact with the object, reducing the need for sensors or feedback control.

Flexure joints are made through Dieless Deposition Manufacturing (DDM), utilizing Smooth-on polyurethane. Tendon-driven, flexure-based joints allow for adaptive behavior and robustness against collisions.

The estimated fabrication cost is $400-700:

  • 3D printed parts (~$300-400 depending on vendor)
  • urethane materials (~$50)
  • Dynamixel actuator (~$250)
  • fasteners (~$50)

Raymond R. Ma, Lael U. Odhner, Aaron M. Dollar
"A Modular, Open-Source 3D Printed Underactuated Hands," Proceedings of the 2013 IEEE International Conference on Robotics and Automation (ICRA), Karlsruhe, Germany, May 6-10, 2013.



  • Actuator: Dynamixel MX-64
  • Base height: 75-90 mm
  • Base width: 100 mm
  • Weight: 400 g
  • Grip Force: 10 N


Build - Model T


  • Ver 0.5.2 (11/14/13) [.rar] [.zip]

  • Ver 0.5 (6/2/13) [.rar] [.zip]
  • Ver 0.4.1 (4/2/13) [.rar] [.zip]

  • In Progress: Ver 0.6 (wrist mounts)