Load the filament
Load your Bambu H2D with PLA Basic and TPU 90A.
GEAR UMI / Hardware Guide
Hardware Guide
Document ID: UMI-FLX-DOC-01-0001 · UMI flexure gripper assembly instructions.
3D model
Click a part to jump to the steps that build it. Drag to rotate, scroll to zoom.
Tools and software
Part numbers, vendors and links are in the Bill of Materials.
Tools
- Bambu Lab H2D printer
- 0.4 mm nozzles
- Bambu Lab P2S printer (for the fingers)
- M2 screwdriver or Allen key
- M3 screwdriver or Allen key
Consumables
- Super glue (for example, Gorilla Glue)
- Lubricant
Software
- Bambu Studio
Print instructions
Download the print files
Download UMI Open Source Printed Parts.3mf and the gripper STL files (ZIP). Unpack the STL files.
Open the project
Open UMI Open Source Printed Parts.3mf in Bambu Studio.
Import the multi-part assemblies
To print the flexure grip and the gear mount as combined multi-part assemblies, select all of their .STL files (in the flexure grip and gear folders of the STL ZIP) and import them at the same time. Click Yes when asked to load the files as a single object with multiple parts.
Note The gear and gear mount print together as one print-in-place part. Do not try to separate them.
Prepare Plate 1 (the flexure grip)
- If using a Bambu H2D: no settings need to change.
- If not using a Bambu H2D:
- Go to Process → Objects.
- Highlight both flexure grips.
- Open the Support tab.
- Set both Filament for Supports options to PLA.
- When asked to change settings automatically for PLA supporting TPU, click No.
Open the finger project
Download finger.3mf and open it in Bambu Studio.
Print the fingers on the Bambu P2S
- Make sure your Bambu P2S is loaded with TPU 95A HF.
- Print the file. Do not change any of the process settings.
- Make sure the print speed is set to 50%, Silent.
Print the remaining PLA parts
Print the remaining PLA parts in their current orientation, with default PLA supports.
Remove the supports
Remove the supports from the finished parts.
See also the filament and print profile section of the Bill of Materials.
Assembly instructions
Gripper mechanismSteps 1–9
Mount the MGN9 rail to the handle
Fasten the MGN9 rail to the handle with two M3 x 12 mm hex socket cap screws and two M3 nuts.
Mount the finger mounts to the rail
Fasten the finger mounts to the rail with eight M3 x 6 mm screws.
Mount the flexure linkage to the center fastening holes
Fasten the flexure linkage to the center fastening holes with two M3 x 8 mm screws and two M3 nuts.
Mount the rotary encoder to the handle
Fasten the rotary encoder board to the handle with two M2 x 8 mm screws and two M2 nuts.
Super glue the magnet to the gear
Super glue the magnet to the gear, then grease the gear and its mount for smooth rotation.
Fasten the gear to the handle
Fasten the gear to the handle with two M2 x 8 mm screws and two M2 nuts.
Cut and add grip tape on the fingers
Cut the grip tape to shape with scissors and stick it on the fingers.
Fasten the left finger on the left finger mount
Fasten the left finger to the left finger mount with two M3 x 30 mm screws and two M3 nuts.
Fasten the right finger with the rack on top of the right finger mount as shown
Fasten the right finger and the rack on top of the right finger mount with two M3 x 35 mm screws and two M3 nuts.
Cameras and electronicsSteps 10–14
Fasten the top camera on the top camera mount
Fasten the top camera to the top camera mount with four M2 x 8 mm screws and four M2 nuts.
Assemble the main PCB board
- Stick the thermal tape under the heatsink.
- Clip the OAK-SoM onto the UMI-OAK-CB1 board by the circled connector.
- Fasten the heatsink to the OAK-SoM with four M2 x 8 mm screws, or the Phillips screws supplied with the heatsink.
Plug the top camera cable into the main PCB board
Plug the top camera cable into the main PCB board. The circled area in the photo shows the connection.
Fasten the top camera mount with the PCB board to the top cover
Fasten the top camera mount, with the PCB board, to the top cover with four M3 x 16 mm screws and four M3 nuts.
Fasten the wide camera to the trigger camera mount
Fasten the wide camera to the trigger camera mount with three M2 x 6 mm hex socket screws and three M2 nuts.
Final assemblySteps 15–21
Fasten the top cover to the handle piece
Fasten the top cover to the handle with two M3 x 30 mm hex socket cap screws and two M3 nuts.
Fasten the top cover, the handle and the trigger camera mount together as shown
Fasten the top cover, the handle and the trigger camera mount together with two M3 x 35 mm screws and two M3 nuts, as shown.
Fasten the handle link
Fasten the handle link with one M3 x 12 mm screw and one M3 nut.
Fasten the iPhone mount on top of the top cover, then attach the iPhone and the clip
Fasten the iPhone mount on top of the top cover with four M3 x 12 mm screws and four M3 nuts, then attach the iPhone and the clip.
VIVE tracker: if you use the VIVE tracker mount instead, fasten it the same way, with four M3 x 12 mm screws and four M3 nuts.
Plug in the necessary wiring to the PCB board
- Plug the rotary encoder board cable into the main PCB board.
- The trigger camera cable ends in a USB-A plug that goes into your computer.
The circled areas in the photos show each connection, in the same order.
Attach the wrist strap
Put your thumb through the thumb loop of the wrist wrap strap, wrap the strap once around your wrist, then wrap it around the forearm mount.
Perform the same assembly steps 1–20 on handle L/R
This builds the second gripper of the pair.
Finished gripper
Firmware
The RP2040 microcontroller on the UMI-OAK-CB1 main PCB runs the umi-encoder firmware, version 2.0.0 (electronics release Rev2617). It reads the TLE5012B rotary encoder 120 times a second and records the two on-board microphones, and sends both to the computer over USB. The encoder PCB has no microcontroller, so it needs no firmware of its own.
Note The release does not include a ready-to-flash firmware file. Build umi-encoder.uf2 from the source first, then flash it.
Downloads
| File | Contents | Size |
|---|---|---|
| umi-encoder-v2.0.0-source.zip | Firmware v2.0.0: RP2040 sources and CMake build files | 68 KB |
| umi-oak-cb1-production.zip | UMI-OAK-CB1 main PCB: Gerbers, drill files, BOM and placement | 0.7 MB |
| tle5012b-encoder-production.zip | TLE5012B encoder PCB: Gerbers, drill files, BOM and placement | 30 KB |
| UMI-Gripper-Rev2617-offline.zip | Full release: KiCad projects for both boards, custom library and firmware | 7.7 MB |
| UMI-Gripper-Rev2617-README.md | Release notes: board architecture, USB interfaces, encoder data format | 5 KB |
The same files are in this repository, unzipped: the firmware in files/firmware/umi-encoder/ and the KiCad projects in files/electrical/kicad/. Keep the kicad/ folder structure as it is, so the boards find their custom library. Open them in KiCad 10 or newer.
Build the firmware
Install the build tools
- CMake 3.13 or newer
- Arm GNU Toolchain 14.2.Rel1 (
arm-none-eabi) - Raspberry Pi Pico SDK 2.2.0, with its submodules:
git clone -b 2.2.0 --recurse-submodules https://github.com/raspberrypi/pico-sdk.git ~/pico-sdkTip The Raspberry Pi Pico extension for VS Code installs the same SDK, toolchain and picotool versions for you, and the firmware’s build files pick them up automatically.
Build umi-encoder.uf2
Unzip umi-encoder-v2.0.0-source.zip, then run these commands in the unzipped folder (the one that contains firmware/):
export PICO_SDK_PATH=~/pico-sdk
cmake -S firmware -B build -DCMAKE_BUILD_TYPE=Release
cmake --build buildThe firmware file is build/umi-encoder.uf2. The encoder and the microphones are both on by default; the pin assignments are in firmware/board.h.
Flash the firmware
Connect the gripper to your computer with a cable in the main PCB's USB-C data port. The other USB-C port only supplies power, so the RP2040 can't be reached through it.
Flash with picotool
Use this when the gripper already runs UMI firmware. Install picotool 2.2.0 or newer, then run:
picotool load -f -x build/umi-encoder.uf2-f restarts the RP2040 into its USB bootloader (BOOTSEL mode) over the USB cable, and -x starts the new firmware when the copy is done. On Linux, run it with sudo if picotool can’t open the device.
Or copy the file in BOOTSEL mode
Use this for a new board with no firmware yet, or if picotool can’t find the gripper.
- Hold the RP2040’s BOOTSEL button on the main PCB while you connect the USB-C data cable.
- A USB drive named
RPI-RP2appears. Copybuild/umi-encoder.uf2onto it. - The RP2040 restarts and runs the new firmware.
Check the firmware
Check the version
picotool info -fThe output should show the program name umi-encoder and version 2.0.0.
Check the USB connections
The gripper shows up on the computer as two serial ports and a microphone:
- Serial port 1 (CDC 0): readable diagnostic messages.
- Serial port 2 (CDC 1): binary encoder frames with the angle and sensor health. See
umi_protocol.hfor the format. - USB microphone (UAC2): stereo, 48 kHz, 16-bit.
Check the sensor health in each frame before you trust its angle.
UMI Robot Wrist
UMI Robot Wrist · UMI fingers on a YAM linear gripper, mounted on a robot arm through the Tianji mount.
3D model
Click a part to jump to the steps that build it. Drag to rotate, scroll to zoom.
Tools and software
Part numbers, vendors and links are in the Bill of Materials. Print the fingers first, following print steps 6 and 7 in the Gripper tab.
Tools
- Bambu Lab P2S printer (for the fingers)
- M2 screwdriver or Allen key
- M3 screwdriver or Allen key
- M4 screwdriver or Allen key
Software
- Bambu Studio
Assembly instructions
Quantities are for one wrist. Build a second one for a pair.
FingersSteps 1–4
Unfasten the finger tips
Starting with the YAM gripper, unfasten the left and right finger tips.
Note Keep the dowel pins. You need them in step 2.
Mount the finger mounts to the YAM linear gripper
Fasten the finger mounts to the YAM linear gripper with four M4 x 15 mm hex socket cap screws, using the two dowel pins from step 1.
Cut and add grip tape on the fingers
Cut the grip tape to fit with scissors and stick it on each finger as shown.
Insert the fingers as shown and screw them in
Slide each finger into its finger mount as shown, then fasten both with four M3 x 30 mm hex socket cap screws.
Cameras and electronicsSteps 5–8
Fasten the top camera on the top camera mount
Fasten the top camera to the top camera mount with four M2 x 8 mm screws and four M2 nuts.
Assemble the main PCB board
- Stick the thermal tape under the heatsink.
- Clip the OAK-SoM onto the UMI-OAK-CB1 board by the circled connector.
- Fasten the heatsink to the OAK-SoM with four M2 x 8 mm screws, or the Phillips screws supplied with the heatsink.
Fasten the top camera and the PCB board onto the wrist mount
Fasten the top camera mount, with the PCB board, onto the wrist mount with four M3 x 18 mm hex socket cap screws and four M3 nuts.
Fasten the trigger camera on the wrist mount
Fasten the trigger camera to the wrist mount with three M2 x 6 mm hex socket cap screws and three M2 nuts.
Mounting on the robot armSteps 9–12
Mount the wrist mount on the wrist
Fasten the wrist mount to the wrist with four M3 x 14 mm hex socket cap screws.
Mount the wrist padding to the wrist mount
Fasten the wrist padding to the wrist mount with four M3 x 14 mm hex socket cap screws.
Attach the Tianji mount to the robot arm
Fasten the Tianji mount to the robot arm with six M4 x 8 mm hex socket cap screws.
Attach the whole wrist to the wrist mount padding
Fasten the whole wrist to the wrist padding with four M3 x 25 mm hex socket cap screws and four M3 nuts.
