Build ALOHA

Steps

23

Subassemblies

9

Hands-on time (sum)

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Critical path

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Your progress · this device

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

1. Fabrication
   01

   Print the 25 ALOHA parts

   Download the STLs from the Drive folder (file names are `(quantity)part_name.stl`) and print in PLA with supports on, 40-80% infill and extra walls/top/bottom layers, using the orientations shown in the 3D printing doc. File or sand holes so moving parts turn freely.

   CHECKYou have 25 pieces matching the quantities in the file names, and each slider slides freely along a removed WidowX gripper rail.

   Parts in

   • handle_lower (master handle)printed.handle-lower
   • handle_upper (master handle)printed.handle-upper
   • lever1 (backdriving unit)printed.lever1
   • lever2 (backdriving unit)printed.lever2
   • slider (backdriving unit, rides on the gripper rail)printed.slider
   • rotor (backdriving unit)printed.rotor
   • rotor_arm (backdriving unit)printed.rotor-arm
   • finger1 (puppet gripper)printed.finger1
   • finger2 (puppet gripper)printed.finger2
   • cam_mount (wrist camera)printed.cam-mount
   • cam_mount_2 (front camera)printed.cam-mount-2
   • FDM 3D printer and filament (BOM gives ~$300)other.fdm-printer

   Tools

   FDM printer (~$300 class), Ultimaker Cura, Metal file set

   Torque

   —

   Time

   —

   After

   Start

   Source

   docs.google.com

2. Electrical
   02

   Rewire robot power to the shared supply

   Safety · human-verified required

   The tutorial replaces the stock ViperX supplies with one supply that powers all four robots. Cut the female end off each of the 4 DC cables and fit fork spade connectors, then connect them to the supply terminals as its manual instructs. Mains wiring: do this unplugged and close the terminal cover before power-on.

   CHECKWith the supply switched on and no robot connected, each barrel plug reads the supply voltage with the same polarity as the stock adapter, and nothing gets warm.

   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

   • Replacement power supply able to power all 4 robots at once (stock ViperX supply can be unstable)power.psu
   • DC power cable to each robot (female end cut off, fitted with fork spade connectors)cable.dc-robot
   • Fork spade connectors (quantity not stated upstream)cable.fork-spade

   Tools

   Wire stripper, Crimp tool, Digital multimeter

   Torque

   —

   Time

   —

   After

   Start

   Source

   docs.google.com

3. Software
   03

   Install ROS, Interbotix and the aloha package

   Install ROS and the Interbotix X-series arm software per Trossen's docs (creates `~/interbotix_ws`). Clone this repo into `~/interbotix_ws/src`, run `source /opt/ros/noetic/setup.sh && source ~/interbotix_ws/devel/setup.sh`, `sudo apt-get install ros-noetic-usb-cam && sudo apt-get install ros-noetic-cv-bridge`, then `catkin_make` in `~/interbotix_ws`. In `interbotix_xs_modules/arm.py`, function `publish_positions`, change `self.T_sb = mr.FKinSpace(...)` to `self.T_sb = None` to avoid per-step FK latency.

   CHECK`catkin_make` finishes without errors and `rospack find aloha` prints the package path.

   Parts in

   • Linux PC with at least 6 USB3 ports (4 robots direct, 2 for camera hubs); 'heavy-duty' recommendedcompute.pc

   Tools

   Ubuntu 20.04 + ROS 1 Noetic (tested per README)

   Torque

   —

   Time

   —

   After

   Start

   Source

   github.com

4. Frame
   04

   Build the frame on the desk

   Safety · human-verified required

   Follow the Fusion 360 assembly (yellow 120 cm, green 100 cm, blue 15 cm bars). Place the blue 15 cm bar 25 cm from the table edge and the horizontal bar 80 cm above the tabletop. The highlighted bar meets the green horizontal bar outside the table edge. Secure the frame to the desk with L-brackets and wood screws. Tip-over risk: secure the frame to the table while building it.

   CHECKMeasured 25 cm and 80 cm positions are correct, and pushing the top of the frame does not rock the desk.

   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

   • Standing desk, 48x30 in, blackstructure.desk
   • Aluminium extrusion bars, black, 10 pcs x 1220 mm (48 in) (yellow bars in frame CAD)structure.extrusion-1220
   • Aluminium extrusion bars, black, 10 pcs x 1000 mm (39.4 in) (green bars)structure.extrusion-1000
   • Aluminium extrusion bars, black, 4 pcs x 150 mm (5.9 in) (blue bars)structure.extrusion-150
   • Corner bracket set, 20 sets, M5x8 (type 1 brackets)fastener.corner-bracket-m5
   • Corner bracket, black, L-4 with screws (type 2; supplies the drop-in T-nuts)fastener.l-bracket
   • Nuts 20S-M5 (T-nuts)fastener.m5-tnuts
   • Wood screws (L-brackets to desk)fastener.wood-screws

   Tools

   Allen keys, Tape measure

   Torque

   —

   Time

   —

   After

   Start

   Source

   a360.co

5. Software
   05

   Create the aloha conda environment and install ACT

   `conda create -n aloha python=3.8.10`, `conda activate aloha`, then pip install torch, torchvision, pyquaternion, pyyaml, rospkg, pexpect, `mujoco==2.3.7`, `dm_control==1.0.14`, opencv-python, matplotlib, einops, packaging, h5py, ipython. Clone tonyzhaozh/act and run `cd act/detr && pip install -e .`.

   CHECK`python -c "import mujoco, dm_control, detr"` succeeds inside the aloha env.

   Parts in

   • Linux PC with at least 6 USB3 ports (4 robots direct, 2 for camera hubs); 'heavy-duty' recommendedcompute.pc

   Tools

   —

   Torque

   —

   Time

   —

   After

   03

   Source

   github.com

6. Electrical
   06

   Connect the 4 arms and bind fixed serial ports

   Safety · human-verified required

   Plug each robot directly into the PC (no hub, no extension) and power it on. In Dynamixel Wizard 2 set Protocol 2.0, all ports, 1000000 bps, ID range 0-10 and scan. Then, per arm, get the FTDI serial with `udevadm info --name=/dev/ttyUSB0 --attribute-walk | grep serial` and add `SUBSYSTEM=="tty", ATTRS{serial}=="<serial>", ENV{ID_MM_DEVICE_IGNORE}="1", ATTR{device/latency_timer}="1", SYMLINK+="ttyDXL_master_right"` (and puppet_right, master_left, puppet_left) to `/etc/udev/rules.d/99-fixed-interbotix-udev.rules`; apply with `sudo udevadm control --reload && sudo udevadm trigger`. Arms collapse when torque is off: support them by hand.

   CHECKThe Wizard scan shows 4 devices with 9 motors each, and `ls /dev/ttyDXL*` lists all four symlinks.

   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

   • Trossen ViperX 300 Robot Arm 6DOF (puppet / follower arms)actuator.vx300s
   • Trossen WidowX 250 Robot Arm 6DOF (master / leader arms)actuator.wx250s
   • Micro-B to USB-A cable, 10 ft (replaces the short stock cable; one per robot implied, extensions do not work)cable.usb-microb-10ft

   Tools

   —

   Torque

   —

   Time

   —

   After

   02, 03

   Source

   github.com

7. Master arms (WidowX)
   07

   Install handles on the two WidowX (master) arms

   Fit handle_lower and handle_upper to each WidowX with 4 M2.5 nuts and M2.5x10 bolts. Enlarge the holes with a drill if the bolt does not pass; two diagonal screws may be enough, four is more secure.

   CHECKThe handle does not twist or rock on the wrist when you pull on it.

   Parts in

   • Trossen WidowX 250 Robot Arm 6DOF (master / leader arms)actuator.wx250s
   • handle_lower (master handle)printed.handle-lower
   • handle_upper (master handle)printed.handle-upper
   • M2.5 screws (M2.5x10 handle bolts, M2.5x8 camera-mount screws)fastener.m25-screws
   • Bolts and nuts (assortment; the guide also calls for M5x14 bolts and M2.5/M3 nuts, source not itemised)fastener.bolts-nuts

   Tools

   Drill, Allen keys

   Torque

   —

   Time

   —

   After

   01

   Source

   docs.google.com

8. 08

   Assemble the backdriving units

   Per unit: lever1, lever2, 2 sliders, 1 rotor, 2 rotor_arms. Check first that both sliders slide easily on the removed gripper rail and file them if not. Round or enlarge holes as needed so the linkage moves freely. Trim a cable tie for the velcro finger loop and hot-glue it to the lever.

   CHECKThe assembled unit matches the front/back/side photos and the linkage moves end to end without sticking.

   Parts in

   • lever1 (backdriving unit)printed.lever1
   • lever2 (backdriving unit)printed.lever2
   • slider (backdriving unit, rides on the gripper rail)printed.slider
   • rotor (backdriving unit)printed.rotor
   • rotor_arm (backdriving unit)printed.rotor-arm
   • Cable ties (also trimmed for the velcro finger loop)other.cable-tie
   • Hot glue gunother.hot-glue
   • Metal file set (post-processing prints, fitting sliders)other.metal-files

   Tools

   Allen keys, Metal file set, Hot glue gun

   Torque

   —

   Time

   —

   After

   01

   Source

   docs.google.com

9. Puppet arms (ViperX)
   09

   Mount printed fingers on the ViperX (puppet) grippers

   Check that the robot's sliders move freely on the gripper rail first; file the slider holes if they are too tight. Mount finger1/finger2 the same way as the OEM fingers with the two long screws supplied with the robot (a drill helps; it is expected to be hard). The straight edge faces up.

   CHECKFingers open and close by hand with the clearance shown in the tutorial video and meet squarely when closed.

   Parts in

   • Trossen ViperX 300 Robot Arm 6DOF (puppet / follower arms)actuator.vx300s
   • finger1 (puppet gripper)printed.finger1
   • finger2 (puppet gripper)printed.finger2
   • Metal file set (post-processing prints, fitting sliders)other.metal-files

   Tools

   Allen keys, Drill with hex bits

   Torque

   —

   Time

   —

   After

   01

   Source

   docs.google.com

10. Frame
    10

    Stiffen the frame with crossing cables

    Add diagonal crossing cables with the turnbuckles, attached through corner brackets or wound around the beam, and tension them so arm motion does not shake the cameras.

    CHECKTop-camera image shows no visible shake while an arm moves quickly.

    Parts in

    • Wire tensioner kit (60 m 1/16 in cable + M5 turnbuckles)structure.wire-tensioner
    • Corner bracket set, 20 sets, M5x8 (type 1 brackets)fastener.corner-bracket-m5
    • Rope crimping tool, 15 in, for 3/64 to 1/8 in cableother.rope-crimper

    Tools

    Rope crimping tool, Allen keys

    Torque

    —

    Time

    —

    After

    04

    Source

    docs.google.com

11. Master arms (WidowX)
    11

    Remove the OEM WidowX grippers

    Remove the stock gripper from each WidowX. Keep every original screw, washer and T-nut and note where each came from; they are reused in the same places.

    CHECKGripper rail and motor shaft are exposed and all removed hardware is bagged per arm.

    Parts in

    • Trossen WidowX 250 Robot Arm 6DOF (master / leader arms)actuator.wx250s

    Tools

    Allen keys

    Torque

    —

    Time

    —

    After

    07

    Source

    docs.google.com

12. Puppet arms (ViperX)
    12

    Apply grip tape to the fingers

    Apply a 1 cm piece at each fingertip (tape end at the tip of the triangle), then a ~10 cm strip wrapped around the straight edge first, then the other side, and trim. Optional: cover the whole finger with 5 cm, 3.5 cm and 2 cm pieces with no seam or overlap between the last two, which helps with round objects.

    CHECKTape is tight with no lifted edges; the closed gripper picks up a thin plastic bag or candy wrapper from the table.

    Parts in

    • Gripping tape, 1 in wideother.grip-tape

    Tools

    —

    Torque

    —

    Time

    —

    After

    09

    Source

    docs.google.com

13. 13

    Mount the wrist cameras

    Remove the webcam stand (see the linked video), slide the camera into cam_mount and hold it with one M3x4 screw. Mount cam_mount to the robot with 4 M2.5x8 screws.

    CHECKThe camera does not shift when the wrist is shaken by hand and its image shows the fingers.

    Parts in

    • Logitech C922x Pro Stream webcam (2 wrist, 1 top, 1 front)sensor.c922x
    • cam_mount (wrist camera)printed.cam-mount
    • M2.5 screws (M2.5x10 handle bolts, M2.5x8 camera-mount screws)fastener.m25-screws
    • M3 screws (M3x30 rail screws, M3x4 camera screw)fastener.m3-screws

    Tools

    Allen keys

    Torque

    —

    Time

    —

    After

    09

    Source

    docs.google.com

14. Policy
    14

    Train and evaluate ACT

    Sim sanity check first: `python3 record_sim_episodes.py --task_name sim_transfer_cube_scripted --dataset_dir <dir> --num_episodes 50`, then `python3 imitate_episodes.py --task_name sim_transfer_cube_scripted --ckpt_dir <ckpt dir> --policy_class ACT --kl_weight 10 --chunk_size 100 --hidden_dim 512 --batch_size 8 --dim_feedforward 3200 --num_epochs 2000 --lr 1e-5 --seed 0`; add `--eval` to evaluate. For real data train at least 5000 epochs or 3-4x past the loss plateau.

    CHECKSim evaluation success is around 90% for transfer cube (around 50% for insertion), per the ACT README.

    Parts in

    —

    Tools

    NVIDIA GPU

    Torque

    —

    Time

    —

    After

    05

    Source

    github.com

15. Master arms (WidowX)
    15

    Mount the backdriving unit on motor 9

    Safety · human-verified required

    Connect with Dynamixel Wizard, select the 9th motor (gripper), torque it on and set Position to 180 by dragging the red line. Mount the backdriving unit to the shaft using its left and right holes.

    CHECKWith the motor at 180 the shaft holes line up with the tutorial photo and the unit sits flush on both holes.

    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

    • Trossen WidowX 250 Robot Arm 6DOF (master / leader arms)actuator.wx250s

    Tools

    Allen keys, Dynamixel Wizard 2

    Torque

    —

    Time

    —

    After

    08, 11, 06

    Source

    docs.google.com

16. 16

    Refit the gripper rail with M3x30 screws

    On each side: M3x30 screw, a nut as washer, through the hole, a second nut to secure it; then another nut and the original T-nut so the screw is flush with the T-nut. Slide the rail through T-nut, slider, slider, T-nut and tighten the nuts at both ends. A little WD-40 on the rail helps.

    CHECKThe rail does not move when pushed, and both sliders run along it with no binding.

    Parts in

    • M3 screws (M3x30 rail screws, M3x4 camera screw)fastener.m3-screws
    • Bolts and nuts (assortment; the guide also calls for M5x14 bolts and M2.5/M3 nuts, source not itemised)fastener.bolts-nuts
    • WD-40 (lubricating the gripper rail)other.wd40

    Tools

    Allen keys

    Torque

    —

    Time

    —

    After

    15

    Source

    docs.google.com

17. 17

    Test backdriving

    Torque off motor 9 in Dynamixel Wizard and move the finger loop.

    CHECKThe gripper motor backdrives easily through its full travel, as in the tutorial video.

    Parts in

    —

    Tools

    Dynamixel Wizard 2

    Torque

    —

    Time

    —

    After

    16

    Source

    docs.google.com

18. Frame
    18

    Mount the WidowX and ViperX arms to the frame

    Mount each WidowX with two M5x14 bolts into drop-in T-nuts (position is up to you). Mount each ViperX with three M5x14 bolts into drop-in T-nuts, bolt 1 into the 15 cm bar; position matters here and washers may be needed. Mark the workspace centre with a 15x1 cm white tape at the intersection of the robot-base line and the table centre line.

    CHECKNo arm base moves when the arm is pushed at full reach, and the white tape sits on both reference lines.

    Parts in

    • Trossen WidowX 250 Robot Arm 6DOF (master / leader arms)actuator.wx250s
    • Trossen ViperX 300 Robot Arm 6DOF (puppet / follower arms)actuator.vx300s
    • Bolts and nuts (assortment; the guide also calls for M5x14 bolts and M2.5/M3 nuts, source not itemised)fastener.bolts-nuts
    • Corner bracket, black, L-4 with screws (type 2; supplies the drop-in T-nuts)fastener.l-bracket

    Tools

    Allen keys

    Torque

    —

    Time

    —

    After

    04, 17, 12, 13

    Source

    docs.google.com

19. 19

    Mount the top and front cameras

    Screw one webcam into the clamp mount and fix it to the middle of the horizontal bar. Remove the stand from another webcam, slot it into cam_mount_2 on a 15 cm bar held by 2 type-1 corner brackets at the centre of the table. Adjust both views to match the tutorial reference images. Run cameras through the USB hubs, max 2 per hub.

    CHECKTop and front images match the reference views with the white tape near the image centre.

    Parts in

    • Logitech C922x Pro Stream webcam (2 wrist, 1 top, 1 front)sensor.c922x
    • Camera mount: 1/4 in screw C-clamp + tripod head (top camera)structure.camera-mount
    • cam_mount_2 (front camera)printed.cam-mount-2
    • Aluminium extrusion bars, black, 4 pcs x 150 mm (5.9 in) (blue bars)structure.extrusion-150
    • Corner bracket set, 20 sets, M5x8 (type 1 brackets)fastener.corner-bracket-m5
    • USB hub (cameras only, max 2 cameras per hub)electronics.usb-hub

    Tools

    Allen keys

    Torque

    —

    Time

    —

    After

    18

    Source

    docs.google.com

20. 20

    Rubber-band gravity compensation for the master arms

    Hang each WidowX from the carbon fibre rod with rubber bands, zip ties and cable from the tensioner kit, as in the tutorial photo and video.

    CHECKWith torque off, each master arm stays roughly where you leave it instead of dropping.

    Parts in

    • Carbon fibre tube 10x12x500 mm (rubber-band hanger for the master arms)structure.cf-tube
    • Rubber bandsother.rubber-band
    • Cable ties (also trimmed for the velcro finger loop)other.cable-tie
    • Wire tensioner kit (60 m 1/16 in cable + M5 turnbuckles)structure.wire-tensioner

    Tools

    —

    Torque

    —

    Time

    —

    After

    18

    Source

    docs.google.com

21. Bring-up
    21

    Limit puppet gripper current and bind camera ports

    In Dynamixel Wizard select `[ID:009] XM430-W350` on each puppet arm, set `38 Current Limit` to `200` and save. Then add udev rules for the cameras (`SUBSYSTEM=="video4linux", ATTRS{serial}=="<serial>", ATTR{index}=="0", ATTRS{idProduct}=="085c", ... SYMLINK+="CAM_RIGHT_WRIST"`, likewise CAM_LEFT_WRIST, CAM_LOW, CAM_HIGH) and reload udev.

    CHECKCurrent Limit reads 200 after re-reading both motors, and `/dev/CAM_*` shows all four camera symlinks.

    Parts in

    • Trossen ViperX 300 Robot Arm 6DOF (puppet / follower arms)actuator.vx300s
    • Logitech C922x Pro Stream webcam (2 wrist, 1 top, 1 front)sensor.c922x

    Tools

    Dynamixel Wizard 2

    Torque

    —

    Time

    —

    After

    18, 19

    Source

    github.com

22. 22

    First motion: bimanual teleoperation

    Safety · human-verified required

    Put all 4 robots in their sleep positions and open the master grippers. Terminal 1: `roslaunch aloha 4arms_teleop.launch`. Terminals 2 and 3 (conda env aloha, in `aloha_scripts`): `python3 one_side_teleop.py right` and `python3 one_side_teleop.py left`. All robots rise to a teleop height; teleoperation starts when a master gripper is closed. Keep clear of the puppet arms. Before cutting power run `python3 sleep.py`.

    CHECKThe launch prints no errors, and each puppet follows its master joint by joint with the gripper tracking the finger loop.

    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

    21, 20, 05, 10

    Source

    github.com

23. Data
    23

    Record episodes

    Set `DATA_DIR` and the task in `aloha_scripts/constants.py`, then `python3 record_episodes.py --dataset_dir <dir> --episode_idx 0`. Check with `python3 visualize_episodes.py --dataset_dir <dir> --episode_idx 0` and replay on the robot with `python3 replay_episodes.py ...`.

    CHECKAn hdf5 file is written per episode and the visualisation shows all 4 camera streams and joint traces for the full episode length.

    Parts in

    —

    Tools

    —

    Torque

    —

    Time

    —

    After

    22

    Source

    github.com

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