Assembly Guide

Part 1: Skeleton Part 2: Electronics
We take our default recipe as an example (Flexiv Grav for Gripper + Meta Quest for Tracker + 9DTact)

Part 1: exUMI Skeleton

Acknowledgement: Thanks Pengyu for writing this part. Please let us know if anything is unclear.


Overview

All the 3D printed models and tools required for assembling the skeleton of exUMI are as follows.

exUMI Assembly Overview

Specifically, the nuts and screws needed in the assembly process are as shown in the following table.

Category Part Name Quantity Purpose Auxiliary Tools
Nut M3 Hex Nut 12
Nut M5 Hex Nut 4
Screw M3*8 Flat Head Screw 4 Fixing handle and bottom plate A small flat-head screwdriver
Screw M3*18*M4 Socket Head Cap Screw 4 Fixing gripper arm An H2 hex key
Screw M5*30*Φ6 Hex Socket Cap Screw 4 Fixing top cover, bottom plate and the middle gripper arm An H4 hex key
Screw M3*35 Socket Head Cap Screw 2 Fixing top cover and bottom plate
Screw M3*20 Socket Head Cap Screw 2 Fixing orangepi mount

Steps

1. Place the four M5 Hex nuts in the four grooves in the middle of the back of the bottom plate.

Step 1

2. Turn the handle upside down and align its grooves with the four nuts on the bottom plate. Then turn the whole thing over, and be careful not to drop the nuts.

Step 2a Step 2b

3. Fix the handle and the bottom plate together using four M3*8 Flat Head screws and M3 Hex nuts.

Step 3a Step 3b

4. Now let's start assembling the gripper arm. Prepare the four models shown in the following figures (pay attention to their relative positions) and fix them using two M3*18*M4 Socket Head Cap screws and M3 Hex nuts to get the left gripper. We have also shown a picture of the left gripper turned over below.

Step 4a Step 4b Step 4c

5. The assembly of the right arm is similar, symmetrical to that of the left arm.

Step 5a Step 5b Step 5c

6. Next, we can easily put the grippers on the bottom plate follow the pictures below.

Step 6a Step 6b Step 6c

7. Next, we are going to use four M5*30*Φ6 Hex Socket Cap Screw to fix the top cover, bottom plate and the middle gripper arm. Before fixing, first ensure that the four circular holes on the gripper are completely aligned with the holes on the bottom plate, as shown in the following figures. Then pass the M5*30*Φ6 Hex Socket Cap Screw through the top cover, gripper and bottom plate in sequence and slightly tighten the screws.

Step 7a Step 7b Step 7c Step 7d Step 7e

8. Fix top cover and bottom plate at the back of exUMI with two M3*35 Socket Head Cap Screws and M3 Hex nuts.

Step 8

9. Fix the orangepi mount with two M3*20 Socket Head Cap Screws and M3 Hex nuts.

Step 9

10. Finally, we have assembled the skeleton of exUMI!

Step 10

11. Make two 9DTact tactile sensors and screw them on the fingertips.

Part 2: Electronic Components

BOM

Part Name Quantity Amazon Link Taobao Link
Raspberry Pi-4/5 or Orangepi 4B 1
AS5600 Board and magnet 1 AS5600; Magnet Suite
Meta Quest 3/3S 1
Powerbank 1 Pisen
Dupon cables 10cm (female) 5
M3 Heat-stake Inserts 4
M3x8 screws 4
M2 screw 1
M3x4 flat-head screws 2

Steps

1. Seat the heat-stake inserts to the Orangepi mount.

Step 1

2. Use M3x8 screws to secure the Orangepi mount, the OrangePi/RaspberryPi and the Quest controller mount in a sandwich manner

Step 2

3. Glue the magnet to the seat and screw the magnet seat to the bar. Place the AS5600 board face down and secure it with M3x4 screws.

Step 3

4. Connect the AS5600 and the Raspberry Pi/Orange Pi following the figure.

Step 4

5. Install the powerbank and Quest controller (remove its battery lid first).

Step 5

6. Install the Orange Pi / Raspberry Pi operation system. Activate the I2C interface by "sudo orangepi-config" or "sudo raspi-config". Clone the exUMI code repo and the data collection code is in the ARCap folder.

BibTeX

@inproceedings{xu2025exumi,
  title     = {exUMI: Extensible Robot Teaching System with Action-aware Task-agnostic Tactile Representation},
  author    = {Xu, Yue and Wei, Litao and An, Pengyu and Zhang, Qingyu and Li, Yong-Lu},
  booktitle = {Conference on Robot Learning (CoRL)},
  year      = {2025}
}