Build LEAP Hand

Steps

13

Subassemblies

8

Hands-on time (sum)

—

Critical path

—

Your progress · this device

—

13 steps have no time estimate; times above are lower bounds.

1. Fabrication
   01

   Download the CAD

   Fill in the CAD request form on the LEAP site (it records acceptance of the CC BY-NC-SA licence) and download the STL set. Pick the Palm Upper that matches your arm (xArm mount or the blank to modify). For a left hand, print the left palm.

   CHECKYou have STLs for Palm Lower, Palm Upper, Cable Spacer, MCP Bracket, DIP Spacer and Fingertip, for the correct hand side.

   Parts in

   —

   Tools

   —

   Torque

   —

   Time

   —

   After

   Start

   Source

   v1.leaphand.com

2. Preparation
   02

   Confirm every motor horn is at the home mark

   The dot-and-dash marks on the Dynamixel horn show the home position, which the hand commands (180°) at power-up; most motors ship in it. Keep every horn at home while you attach it to a joint, so the hand's home pose matches the CAD. Sort the three screw types first: serrated TAP screws (with the brackets), plain Dynamixel M2x4, and hex screws.

   CHECKAll 16 horns show the dot/dash aligned to home before assembly starts, and the three screw types are in separate trays.

   Parts in

   • DYNAMIXEL XC330-M288-T (Full hand); Lite hand uses XL330-M288-T insteadactuator.xc330-m288-t

   Tools

   —

   Torque

   —

   Time

   —

   After

   Start

   Source

   v1.leaphand.com

3. Fabrication
   03

   Print palm, brackets, spacers and fingertips

   Slice in Cura 5 at the regular quality setting. PLA: palm at 60% infill with supports, everything else 100% infill without supports, 200 °C nozzle, 60 °C bed. Optional soft fingertips in NinjaFlex Edge: 20% infill, no supports, 240 °C nozzle, ~25 mm/s. Upstream says all parts print in under 24 hours.

   CHECK1 palm lower, 1 palm upper, 5 cable spacers, 3 MCP brackets, 3 DIP spacers and 4 fingertips, with clean screw holes and no warping on the palm.

   Parts in

   • Polymaker PLA Pro filament (~200 g used)printed.pla-pro
   • NinjaTek NinjaFlex Edge filament, 100 g (optional soft fingertips)printed.ninjaflex-edge
   • Palm Lower (left hand prints a left palm)printed.palm-lower
   • Palm Upper / mounting lid (xArm mount provided, or a blank to adapt to your arm)printed.palm-upper
   • Cable Spacerprinted.cable-spacer
   • MCP Bracketprinted.mcp-bracket
   • DIP Spacerprinted.dip-spacer
   • Fingertip, soft (NinjaFlex Edge) or hard (PLA)printed.fingertip

   Tools

   FDM printer (Ender 3 S1 used upstream; direct drive needed for flexible filament), Cura 5

   Torque

   —

   Time

   —

   After

   01

   Source

   v1.leaphand.com

4. Electronics
   04

   Set motor IDs one by one

   Safety · human-verified required

   Connect one motor at a time to the U2D2 with 5 V power and set its ID in Dynamixel Wizard. IDs: index 0-3, middle 4-7, ring 8-11, thumb 12-15, in the order MCP side, MCP forward, PIP, DIP. The MCP side motors are 0, 4 and 8. Close Wizard afterwards: the API cannot open the port while it is running.

   CHECKEach motor answers alone at its assigned ID; a scan of the full chain later shows IDs 0-15 exactly once.

   This step can hurt a person or ruin parts. Its instructions need sign-off by a human who has done it before relying on them. Stop and ask if anything differs from what you see.

   Parts in

   • DYNAMIXEL XC330-M288-T (Full hand); Lite hand uses XL330-M288-T insteadactuator.xc330-m288-t
   • DYNAMIXEL U2D2 USB-to-TTL interfaceelectronics.u2d2
   • 5 V 30 A power supplypower.psu-5v-30a

   Tools

   Dynamixel Wizard 2.0

   Torque

   —

   Time

   —

   After

   02

   Source

   v1.leaphand.com

5. Fabrication
   05

   Set brass inserts in fingertips and palm

   Safety · human-verified required

   Press the M2 6 mm inserts into the fingertips (6 per tip) and five M3 6 mm inserts into the palm and your chosen mounting lid with the iron at 250 °C. Hot tip: use a stand and keep the part clamped.

   CHECKEvery insert sits flush and square; an M2 screw threads in fully by hand without the insert spinning.

   This step can hurt a person or ruin parts. Its instructions need sign-off by a human who has done it before relying on them. Stop and ask if anything differs from what you see.

   Parts in

   • Heat-set brass insert variety pack (uses 5x M3 6 mm and 24x M2 6 mm)fastener.inserts-variety
   • Fingertip, soft (NinjaFlex Edge) or hard (PLA)printed.fingertip
   • Palm Lower (left hand prints a left palm)printed.palm-lower
   • Palm Upper / mounting lid (xArm mount provided, or a blank to adapt to your arm)printed.palm-upper

   Tools

   Soldering iron (250 °C)

   Torque

   —

   Time

   —

   After

   03

   Source

   v1.leaphand.com

6. Fingers
   06

   MCP joint assembly (x4)

   1) Fix an H101 horn to the MCP bracket with 4 M2 4 mm screws and nuts. 2) Attach idler and horn to a motor (upward orientation) with 4 black M2 4 mm TAP screws. 3) Put 6 nuts in the top of an S101 bracket and fix it to the motor with 4 long M2 8 mm TAP screws. 4) On top of the MCP bracket add a cable spacer and an S102 bracket, 4 M2 10 mm screws into the bracket nuts. 5) Fix a second motor, top toward the MCP bracket, with long M2 8 mm TAP screws. The thumb has its own sequence.

   CHECKThe two MCP motors are rigidly joined and the side-to-side and forward axes each swing by hand without the brackets touching.

   Parts in

   • MCP Bracketprinted.mcp-bracket
   • Cable Spacerprinted.cable-spacer
   • DYNAMIXEL FPX330-H101 horn, 4-pc set (11 horns needed)structure.fpx330-h101
   • DYNAMIXEL FPX330-S101 bracket, 4-pc set (10 brackets needed; designed to break first in a crash, buy spares)structure.fpx330-s101
   • DYNAMIXEL FPX330-S102 bracket, 4-pc set (6 brackets needed)structure.fpx330-s102
   • DYNAMIXEL XC330-M288-T (Full hand); Lite hand uses XL330-M288-T insteadactuator.xc330-m288-t
   • M2 x 8 mm hex screws, variety pack (16 used)fastener.m2-screws-8mm
   • M2 x 10 mm hex screws, variety pack (24 used; plus 4x M2 6 mm from the same pack)fastener.m2-screws-10mm

   Tools

   PH00 Phillips screwdriver (a motorised one is recommended), M2/M3 hex keys

   Torque

   —

   Time

   —

   After

   03, 02

   Source

   v1.leaphand.com

7. 07

   PIP and DIP assembly, fingertip (x3 fingers)

   1) S101 bracket onto the MCP-side motor, 4 short black 4 mm TAP screws. 2) PIP motor onto the S101 with 4 long M2 8 mm TAP screws. 3) Stack H101 horn, DIP spacer and an S101, 4 M2 10 mm screws into nuts inside the S101. 4) DIP assembly onto the PIP motor with an idler and 4 black M2 4 mm TAP screws. 5) DIP motor into the open S101 with 4 long 8 mm TAP screws. 6) Fingertip onto an H101 horn with 6 M2 screws into the inserts, then horn onto the DIP motor with idler and 4 short 4 mm TAP screws. Repeat for index, middle and ring.

   CHECKThree identical fingers; each joint moves through its range by hand and, with horns at home, the finger is straight as in the CAD.

   Parts in

   • DYNAMIXEL FPX330-S101 bracket, 4-pc set (10 brackets needed; designed to break first in a crash, buy spares)structure.fpx330-s101
   • DYNAMIXEL FPX330-H101 horn, 4-pc set (11 horns needed)structure.fpx330-h101
   • DIP Spacerprinted.dip-spacer
   • Fingertip, soft (NinjaFlex Edge) or hard (PLA)printed.fingertip
   • DYNAMIXEL XC330-M288-T (Full hand); Lite hand uses XL330-M288-T insteadactuator.xc330-m288-t
   • M2 x 10 mm hex screws, variety pack (24 used; plus 4x M2 6 mm from the same pack)fastener.m2-screws-10mm

   Tools

   PH00 Phillips screwdriver

   Torque

   —

   Time

   —

   After

   06, 05

   Source

   v1.leaphand.com

8. 08

   Thumb assembly

   1) S102 with 8 nuts onto the end of a motor, 4 long 8 mm TAP screws. 2) S101 onto that motor's horn, 4 short 4 mm TAP screws (left hand: mount this S101 the opposite way round). 3) Next motor onto the S101, 4 long TAP screws. 4) H101 horn onto it, then another motor to the horn with idler and 4 short TAP screws. 5) Stack S102, cable spacer and H101, 4 M2 6 mm screws and nuts. 6) Finger into the S102 with 4 long TAP screws; new motor into the H101 with idler and 4 short TAP screws. 7) Stack S102, cable spacer and fingertip with 6 M2 6 mm screws and fix to the motor with 4 long TAP screws.

   CHECKThe thumb has 4 motors, its S101 orientation matches the hand side, and all joints move by hand without collision.

   Parts in

   • DYNAMIXEL FPX330-S101 bracket, 4-pc set (10 brackets needed; designed to break first in a crash, buy spares)structure.fpx330-s101
   • DYNAMIXEL FPX330-S102 bracket, 4-pc set (6 brackets needed)structure.fpx330-s102
   • DYNAMIXEL FPX330-H101 horn, 4-pc set (11 horns needed)structure.fpx330-h101
   • Cable Spacerprinted.cable-spacer
   • Fingertip, soft (NinjaFlex Edge) or hard (PLA)printed.fingertip
   • DYNAMIXEL XC330-M288-T (Full hand); Lite hand uses XL330-M288-T insteadactuator.xc330-m288-t
   • M2 x 8 mm hex screws, variety pack (16 used)fastener.m2-screws-8mm
   • M2 x 10 mm hex screws, variety pack (24 used; plus 4x M2 6 mm from the same pack)fastener.m2-screws-10mm

   Tools

   PH00 Phillips screwdriver

   Torque

   —

   Time

   —

   After

   02, 05

   Source

   v1.leaphand.com

9. Palm
   09

   Mount the fingers on the palm

   Fix each of the 4 fingers to the palm with 4 M2 8 mm screws. Close the palm with the mounting lid (M3 6 mm screws into the inserts). Add grip tape where you want friction.

   CHECKAll four fingers are rigid on the palm and the lid is secured by 5 M3 screws.

   Parts in

   • Palm Lower (left hand prints a left palm)printed.palm-lower
   • Palm Upper / mounting lid (xArm mount provided, or a blank to adapt to your arm)printed.palm-upper
   • M2 x 8 mm hex screws, variety pack (16 used)fastener.m2-screws-8mm
   • M3 x 6 mm screws (5 used, palm mount)fastener.m3-screws-6mm
   • Grip tape (palm and finger surfaces)other.grip-tape

   Tools

   M2/M3 hex keys

   Torque

   —

   Time

   —

   After

   07, 08

   Source

   v1.leaphand.com

10. Electronics
    10

    Build the 5 V feed and chain all motors

    Safety · human-verified required

    Wire the 5 V 30 A supply to the Power Hub (or to the custom XT30/JST EH cable, or the LEAP Power board) with 14 AWG cable, and connect each finger chain plus the U2D2. The supply is mains-powered: close its terminal cover and never work on the AC side while plugged in. Check polarity before connecting any motor.

    CHECKWith the motors unplugged the hub output reads +5 V with correct polarity; after plugging in, all 16 Dynamixel LEDs blink once at boot.

    This step can hurt a person or ruin parts. Its instructions need sign-off by a human who has done it before relying on them. Stop and ask if anything differs from what you see.

    Parts in

    • DYNAMIXEL U2D2 Power Hub board set (or a custom 5-lead power cable, or the LEAP Power board)electronics.u2d2-power-hub
    • Custom power cable parts: XT30 pigtail, JST EH cables (15x) and JST EH housings (5x) (optional, replaces the Power Hub)cable.custom-power-kit
    • 14 AWG cable for the 5 V feedcable.14awg-5v
    • 5 V 30 A power supplypower.psu-5v-30a
    • AC power cable (change for your country)power.ac-cable

    Tools

    Soldering iron, Multimeter

    Torque

    —

    Time

    —

    After

    09, 04

    Source

    v1.leaphand.com

11. Software
    11

    Install the Python API and find the port

    Clone LEAP_Hand_API, then in python/: `python -m venv test_env`, activate it, `pip install dynamixel_sdk numpy`. On Ubuntu use the persistent `/dev/serial/by-id/...` path and `sudo chmod 666` it; on Windows find the COM port in Dynamixel Wizard. Put the port in `main.py`. Optional: set Return Delay Time (register 9) to 0 µs and lower USB latency.

    CHECKThe port opens from Python with Wizard closed and reading positions returns 16 values.

    Parts in

    • DYNAMIXEL U2D2 USB-to-TTL interfaceelectronics.u2d2

    Tools

    Python 3, Micro-USB cable (avoid chained USB extensions)

    Torque

    —

    Time

    —

    After

    10

    Source

    github.com

12. Bring-up
    12

    First motion: home pose

    Safety · human-verified required

    Run `python main.py`. The node enables torque with PID position control (kP 600, side-to-side motors at 0.75x) and a 350 mA current limit, and commands the 180° home pose. Keep fingers out of the joints. On a Full hand (XC330) you may raise `curr_lim` to 550 mA; leave Lite hands at the default.

    CHECKThe hand moves to the CAD home pose with every finger straight. A finger off by 90/180/270° means that horn was mounted wrong: remount it. Red-flashing motors mean overload: power-cycle and lower the current limit.

    This step can hurt a person or ruin parts. Its instructions need sign-off by a human who has done it before relying on them. Stop and ask if anything differs from what you see.

    Parts in

    —

    Tools

    —

    Torque

    —

    Time

    —

    After

    11

    Source

    github.com

13. Policy
    13

    Optional: run the pretrained in-hand rotation policy

    Install LEAP_Hand_Sim with Isaac Gym Preview 4, then in leapsim/ run `python3 train.py wandb_activate=false num_envs=1 headless=false test=true task=LeapHandRot checkpoint=runs/pretrained/nn/LeapHand.pth`. For the real hand, start the ROS module (`roslaunch example.launch`), then run `deploy.py` with the same arguments.

    CHECKIn sim the hand reorients the cube continuously; on hardware the hand goes to the pre-grasp pose and rotates a 7.5 cm cube.

    Parts in

    —

    Tools

    NVIDIA GPU, Isaac Gym Preview 4, ROS 1 (for real-hand deployment)

    Torque

    —

    Time

    —

    After

    12

    Source

    github.com

Progress is stored in this browser only (localStorage). Nothing is sent anywhere.