Assembly Guide

Assembly of exUMI Skeleton

Acknowledgement: Thanks Pengyu for writing this guide. 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 (using Flexiv Grav for Gripper, Meta Quest for Tracker and 9DTact for Sensor on our website).

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

Note: The assembly steps are not unique and are for reference only.

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

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}
}