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ArmAlexander Koch / Hugging Face LeRobot2024US

Koch v1.1 Low-Cost Robot Arm

Dynamixel-based low-cost leader/follower arm pair; an assembly-friendly revision of Alexander Koch's low_cost_robot, used in early LeRobot work.

orphanedDIYL2 Sim-verifiedbuildable

Difficulty index

4.9/13
4.9
Index breakdown
Classarm+2
Cost$461 BOM+0.7
DOFunknown · midpoint+1.5
Parts51 parts+0.7
How the index works

Specimen photographs

5 items
  • Koch v1.1 Low-Cost Robot Arm studio render, three-quarter front view
    Studio render of the published MJCF, keyframe pose from the model. Geometry only; colours are the model's own materials.Rendered by Hyperspawn from mujoco_menagerie/low_cost_robot_arm (Apache-2.0) · Hyperspawn render · source
  • Koch v1.1 Low-Cost Robot Arm studio render, side view
    Side view of the same MJCF render, keyframe pose from the model.Rendered by Hyperspawn from mujoco_menagerie/low_cost_robot_arm (Apache-2.0) · Hyperspawn render · source
  • 4 s turntable of the MJCF studio render.Rendered by Hyperspawn from mujoco_menagerie/low_cost_robot_arm (Apache-2.0) · Hyperspawn render · source
  • Koch v1.1 leader and follower arms on a desk with cabling
    From the koch-v1-1 README.Jess Moss (koch-v1-1) · Apache-2.0 · source
  • Low-Cost Robot Arm AssemblyAlexander Koch · official video, embedded · source

Spec card

3/13 known
BOM total
$461 · 17/19 lines priced
Part count
51
Actuators
Follower: Dynamixel XL430-W250-T x2 + XL330-M288-T x4; leader: XL330-M077-T x6

Not in the registry: degrees of freedom, height, mass, payload, speed, runtime, battery, price, compute, sensors. Left blank rather than guessed.

What you learn building it

  • +Forward and inverse kinematics
  • +Joint calibration and homing
  • +Trajectory planning
  • +Teleoperation and collecting demonstrations for learning
  • +FDM 3D printing: 17 parts
  • +Tools used: FDM printer (e.g. Prusa Mini+, Bambu P1, Ender 3), Glue stick, Putty knife, Linux or macOS computer, conda (miniforge), 1.5 mm cruciform screwdriver, Digital multimeter, NVIDIA GPU or Apple silicon
  • +16 assembly steps across 8 subassemblies
  • +Flashing firmware for Dynamixel XL430-W250-T (stock firmware), Dynamixel XL330-M288-T (stock firmware), Dynamixel XL330-M077-T (stock firmware), Waveshare Serial Bus Servo Driver Board (USB-serial, no user firmware)
  • +Testing in simulation (URDF/MJCF) before touching hardware

Openness

75/100
  • publicCAD
  • publicBOM
  • not publicFirmware
  • publicSim model
  • publicSoftware
  • not publicPolicies

Score 75/100 computed from what is public: CAD 25, BOM 20, sim 20, firmware 15, software 10, policies 10. Hardware license: Apache-2.0. Software license: Apache-2.0.

Repos & models

URDF ↗MJCF ↗MuJoCo Menagerie ↗
SiteDocs

Build it

Has an ORP build package.
BOM total
$461
Lines priced
17/19
Parts
51
Steps
16
Version
0.1.0

2 lines have no price yet, so the real total is higher.

Largest BOM lines

Largest bill of materials lines
PartQtyUnit
Dynamixel XL330-M077-T servo (leader arm, 5 V)XL330-M077-T (902-0162-000)6$24
Dynamixel XL430-W250-T servo (follower shoulder pan + shoulder lift, 12 V)XL430-W250-T (902-0135-000)2$50
Dynamixel XL330-M288-T servo (follower elbow, wrist flex, wrist roll, gripper; 5 V)XL330-M288-T (902-0163-000)4$24
12 V to 5 V voltage reducer (feeds the four XL330 servos)EP-JY-DC5 (wiring diagram)1$14
12 V DC power supply (follower arm)1$12
XL330 frame and idler wheel set FPX330-H101, 4 pcs (leader; 3 of 4 used)FPX330-H1011$10
Waveshare Serial Bus Servo Driver Board (leader, run at 5 V)Amazon ASIN B0CTMM4LWK (wiring diagram)1$10
XL330 frame and idler wheel set FPX330-H101, 4 pcs (follower; 3 of 4 used)FPX330-H1011$10

Fabrication

  • FDM 3D printing17
Firmware repo
  • No official Koch policy checkpoints are published by LeRobot; only datasets exist (e.g. lerobot/koch_pick_place_5_lego). The robots.ts 'policies: true' flag rests on community models, not an upstream release.
  • USD prices are the README's 2024 US figures (leader total $199, follower $278); EUR/GBP/CNY/JPY prices are kept as notes. Robotis prices and Amazon listings may have changed since the repo's last commit (Sep 2024).
  • UK links are filed under region EU and Japan links under GLOBAL because the registry has no UK or JP region.
  • Taobao/Tmall URLs are the README links reduced to item id and skuId; several a.co short links resolve to Amazon listings that may be gone.
  • Leader and follower tables both list the Waveshare board, jumpers and a table clamp; the screwdriver and USB cable sets are listed twice upstream but the footnotes say buy once, so they appear once here.
  • The LeRobot Koch page powers the follower board from the 5 V supply during motor setup, while the README and wiring diagram run the follower at 12 V with a 12-to-5 V reducer for the XL330 chain. Both are consistent only if the 12 V supply is never used while an XL330 is plugged straight into the board (XL330 rated 3.7-6.0 V, XL430 6.5-12.0 V per the Robotis e-Manual). Whether the XL430s answer ID setup at 5 V is not stated upstream.
  • The leader board runs at 5 V although the Waveshare board is rated 9-12.6 V; the README says this is intended (footnote 14).
  • The assembly video predates the screwed Leader_Platform and the LeRobot motor-setup order; follow the README and LeRobot notes where they differ.
  • No fastener list beyond the four M2x5 screws and M2 nuts for the platform: servo screws come with the Robotis frame/idler sets. Check the video for counts.
  • No camera is in the BOM; recording datasets needs at least one USB camera.
  • Repo is Apache-2.0; the original low_cost_robot is MIT. The repo has not changed since Sep 2024 and LeRobot now centres on SO-101.

Simulate

Load it in the browser simulator and train a policy before building.

Open on humanoidrobots.training ↗

Next rung

Aero Hand Open →Chestnut Robotics (formerly TetherIA) · hand · index 5.5

Easiest buildable hand, the next class up from arm. Adds tendon and linkage transmissions.

NoteRepo last pushed Sep 2024; LeRobot community has largely moved to SO-101. Original low_cost_robot is MIT-licensed. Uses stock Dynamixel firmware (firmware=false). policies=false: only datasets are published upstream.

Sources

  1. [1]Koch v1.1 repo (Apache-2.0, BOM, leader/follower totals)checked 2026-09-25
  2. [2]LeRobot Koch dataset (no official policy)checked 2026-09-25
  3. [3]Original low_cost_robot (MIT)checked 2026-09-24
  4. [4]MuJoCo Menagerie low_cost_robot_armchecked 2026-09-24
  5. [5]Alexander Koch on GitHub (location)checked 2026-09-24