Skip to content
ShopCommunitySign in
Intermediate build

How to build Actuated UMI Gripper

1-DoF robot gripper · Intermediate

Build the TU Darmstadt actuated UMI gripper: one Dynamixel XL430 drives printed jaws on MGN7C rails through a flat belt, controlled from Python.

Start the buildProject files
Difficulty
Intermediate

Some soldering, calibration and Linux comfort needed.

Build time
2–4 weekends

Our estimate, part-time

Parts cost
Not published

Price the BOM yourself

Degrees of freedom
1

MIT

What is Actuated UMI Gripper?

The original Universal Manipulation Interface (UMI) from Chi et al. is a hand-held, unpowered gripper people squeeze to record demonstrations. Erik Helmut, Niklas Funk, Tim Schneider and Jan Peters at TU Darmstadt turned it into a robot end effector by adding a motor, so a policy trained on UMI-style data can run on the same jaw geometry.

The mechanism is compact: one DYNAMIXEL XL430-W250-T pulls a 5 mm flat belt that moves two printed jaws along a pair of 80 mm MGN7C rails, and two constant-force springs keep the belt loaded. Everything structural is PLA from an ordinary 0.4 mm-nozzle FDM printer.

The team also publishes dynamixel-api, a small Python wrapper that already knows this gripper, plus a ROS 2 package.

Versions and forks

  • v2 part set adds optional GelSight Mini tactile-sensor mounts.
  • The unpowered UMI gripper (Columbia/Stanford) remains the data-collection tool it is based on.

Actuated UMI Gripper specifications

Actuator
1× DYNAMIXEL XL430-W250-T
Drive
Flat belt (5 × 1 × 300 mm) on 2 MGN7C rails
Interface
ROBOTIS U2D2 + U2D2 Power Hub
Print
PLA, 0.4 mm nozzle, 0.2 mm layers
License
MIT

Figures as published by the project. See Sources below.

Bill of materials

PartQtyNotes
DYNAMIXEL XL430-W250-T1
ROBOTIS U2D2 and U2D2 Power Hub1 each
MGN7C linear rail and carriage, 80 mm2
Constant-force spring 0.1 × 8 × 1102
Flat belt, 5 mm wide, 1 mm thick, 300 mm1
Heat-set inserts, M3 screws and nuts, M2 flat-head screws—
Printed structure, jaws, idlers and drive pulley—Carriage mount and pulleys at 100% infill
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
  • Soldering iron for heat-set inserts
  • Hex keys
  • Dynamixel Wizard 2.0

Step-by-step build overview

Electronics & wiring overview

There is only one bus: XL430 → U2D2 Power Hub (power) → U2D2 → USB host. The library's reduce_latency.sh sets the Linux USB latency timer to 1 ms, which noticeably speeds up position reads.

DC power supplypower sourceLaptop / PChigh-level controlEncoderssensingMicrocontrollerreal-time controllerServo bus adapterdrivers / busDynamixel XL430 servos1 joint / motors
PowerData / commandsSensor feedbackOverview only. Follow the project's own schematic for pinouts and voltages.

Software

The project ships its own firmware and control code. See the repository for setup.

dynamixel-api wraps the ROBOTIS Dynamixel SDK with a connector class and a motor class, and includes a sweep tool to find an unknown ID or baud rate. A separate actuated-umi-ros2 repository exposes the gripper to ROS 2.

Tips from the bench

  • ☕ If the servo stops responding after a baud change, run the library's find_grippers sweep rather than guessing.
  • ☕ Print the pulley and carriage mount solid, since they carry all the belt load.
  • ☕ Fingers for the original UMI are printed in TPU; follow the UMI guide for those.

Actuated UMI Gripper FAQ

What motor does the actuated UMI gripper use?

A single DYNAMIXEL XL430-W250-T, connected through a ROBOTIS U2D2 and Power Hub.

How much does it cost?

The project doesn't publish a total. The servo and U2D2 set are the main expense; the rest is rails, springs, a belt and printed PLA.

Can I control it from ROS 2?

Yes. The team publishes an actuated-umi-ros2 package alongside the Python dynamixel-api library.

Sources

Written by Bots n' Beans from the project's own documentation. Check the sources for the latest revision before you buy parts.

Related builds

Robot deals

All deals →
  • Everblog AI fridge calendar

    Deal · Everblog

    10% off

    Get deal
  • CircuitMess DIY robot kits

    Shop · CircuitMess

    DIY robot kits

    Robot and gadget kits you build yourself.

    Shop
  • GRABO Cordless vacuum lifter

    Shop · GRABO

    Cordless vacuum lifter

    GRABO Pro Brushless: the original cordless vacuum lifter for pavers, stone, glass and panels.

    Shop

Like what we do? Buying through these links supports Bots n' Beans. We earn a commission at no extra cost to you. Thank you!