Auto-assembled, not yet reviewed

SO-101

Low-cost 6-DoF teleoperated arm, the LeRobot reference.

Apache-2.0
robot arm6 DoF
$121.94source total

Reproducibility83/100Strong source coverage, unverifiedCADBOMWIREFWBUILDLICREPHow it is computed

SO-101 open-source 6-DoF robot arm, 3D render from so101_new_calib.urdf

main assembly 3D · so101_new_calib.urdf

Source record

Source: TheRobotStudio/SO-ARM100 @fda892c
7.6k stars, last push 2026-09-23
HW license: Apache-2.0
Cost: $121.94source total, follower arm only
Lifecycle: Active
Engine: v3.1.1
Checked: 2026-09-30
Model: so101_new_calib.urdf@fda892crendered 2026-09-30
Envelope: 430 × 268 × 111 mmas modelled, default pose

Maintain SO-101? Claim this page to correct it.

SO-101 reproducibility score

How confidently this design builds into a working robot, from what its sources publish: each criterion's points, quality tier and evidence.

metCAD / mesh present35 editable CAD files (STEP), including an assembly + 110 mesh files20/20
Quality tier 3 of 3
metBOM evidenceREADME.md table (Parts For Two Arms (Follower and Leader Setup):): 8 line items, quantities, priced (USD), vendor links, stated total USD 229.8820/20
Quality tier 5 of 5
- README.md table (Parts For Two Arms (Follower and Leader Setup):)fda892c
partialWiring diagramReviewedThe LeRobot SO-101 guide describes the wiring in text: USB and power supply to the controller board, 3-pin cables chained motor to motor; no diagram. The engine does not read the HF docs.7.5/15
Quality tier 1 of 3
Reviewed override, 2026-09-30
Evidence on huggingface.co
Engine alone: missing at tier 0 (no wiring diagram found)
metFirmware linkedReviewedLeRobot's so_follower module (with its so101 page) is the SO-101 control code that drives the arm's Feetech bus; the engine only counts the project's own repos.10/10
Quality tier 2 of 3
Reviewed override, 2026-09-30
Evidence on github.com
Engine alone: partial at tier 1 (firmware mentioned, no source or link)
- README.md mentions firmwarefda892c
metBuild instructionsReviewedLeRobot's SO-101 guide gives written assembly steps joint by joint, each shown in a video clip (no step photos); the engine does not open the Hugging Face docs.15/15
Quality tier 2 of 3
Reviewed override, 2026-09-30
Evidence on huggingface.co
Engine alone: partial at tier 1 (external build guide linked, not inspected by the engine)
- guide on huggingface.co, not inspected by the engine
metOSHW-compatible licenseApache-2.0 (from repository license)10/10
Quality tier 2 of 2
- LICENSEfda892c
missingKnown reproductionsno verified builds yet0/10
Quality tier 0 of 2
Only build reports a maintainer or admin has reviewed count here.

Engine v3.1.1 at fda892c, 3 items reviewed by hand

How this score is computed

About SO-101

SO-101 is the refined Standard Open Arm design from The Robot Studio, the reference arm of Hugging Face's LeRobot. A leader arm teleoperates a follower arm. The BOM here is the upstream table for one follower arm; printing, fasteners and alternate power supplies are not added to its total.

Licenses

Hardware: Apache-2.0
Software: Not published
Docs: Not published

Degrees of freedom

6 DoF arm 5gripper 1

Breakdown source

Serial armLeader-follower pairsource

How to build SO-101

5 steps

Steps marked Motari summary condense the linked source; follow the source for exact instructions. Upstream step marks a step taken from the linked guide.

Print the structural parts
STL and STEP files are provided, including single-file print plates for common bed sizes. Upstream tested PLA+ at 15% infill with a 0.4 mm nozzle at 0.2 mm layers or a 0.6 mm nozzle at 0.4 mm layers, after printing the fit gauges.
Motari summaryhuggingface.co/docs/lerobot/so101
Flash and ID the servos
Before assembly, connect each STS3215 servo alone to the motor control board and run the LeRobot motor setup to set its ID and baudrate. The follower uses 6 servos with 1/345 gearing; the leader mixes 1/345, 1/191 and 1/147 gear ratios.
Motari summaryhuggingface.co/docs/lerobot/so101
Assemble the links
Assemble joint by joint from the base up, fixing each servo with M2x6 mm screws and bolting the printed parts to the servo horns with M3x6 mm screws.
Upstream stephuggingface.co/docs/lerobot/so101
Wire power and data
Daisy-chain the bus servos, connect the driver board to USB. Verify wiring against the source.
Upstream stephuggingface.co/docs/lerobot/so101
Calibrate and teleoperate
Run the LeRobot calibration, then drive the follower from the leader arm.
Motari summaryhuggingface.co/docs/lerobot/so101

Print timenot published

Assembly timenot published

Wiring, power and firmware are safety-relevant and shown for reference only. Check them against the source before building.

SO-101 bill of materials

6 rows

Cost to build

$121.94USDsource total

follower arm only$121.94source total
leader and follower teleoperation pair$229.88source total

In the source currency, as read on 2026-09-30. Not converted, and not checked against current vendor prices: none of these is a Motari-verified checkout total.

SO-101 parts, as the source lists them (read 2026-06-07). Prices are the source's, not checked against vendors.

SO-101 bill of materials
Part	Qty	Spec	Source	Confidence
STS3215 Servo 7.4V, 1/345 gear (C001)Follower-arm bus servos from the source BOM table	6	Feetech STS3215, 1/345 gear	Feetech / Alibaba$13.89 eachTheRobotStudio/SO-ARM100 README.md line 93	high
Motor Control BoardUSB servo control board	1	Waveshare-style serial bus servo controller	Amazon / TaoBao / Akizuki Denshi$10.60TheRobotStudio/SO-ARM100 README.md line 94	high
USB-C Cable 2 pcsCable pair listed as one BOM line	1	USB-C cable, 2 pieces	Amazon / TaoBao$7.00TheRobotStudio/SO-ARM100 README.md line 95	high
Power SupplyDC power supply for the follower arm	1	5V supply in upstream BOM	Amazon / TaoBao / Akizuki Denshi$10.00TheRobotStudio/SO-ARM100 README.md line 96	high
Table Clamp 2pcsFollower-arm table clamp set	1	2-piece clamp set	Amazon / TaoBao$5.00TheRobotStudio/SO-ARM100 README.md line 97	high
Screwdriver SetAssembly tool listed in the source BOM	1	precision screwdriver set	Amazon / TaoBao$6.00TheRobotStudio/SO-ARM100 README.md line 98	high

Rows from the source's own parts list 14

README.md@fda892cmarkdown

Source row	Qty	Price and vendor	Line
STS3215 Servo 7.4V, 1/345 gear (C001)	7	Alibaba TaoBao$13.89	L76
STS3215 Servo 7.4V, 1/191 gear (C044)	2	Alibaba Akizuki Denshi$13.89	L77
STS3215 Servo 7.4V, 1/147 gear (C046)	3	Alibaba Akizuki Denshi$13.89	L78
Motor Control Board	2	Amazon TaoBao$10.6	L79
USB-C Cable 2 pcs	1	Amazon TaoBao$7	L80
Power Supply	2	Amazon TaoBao$10	L81
Table Clamp 4pcs	1	Amazon TaoBao$9	L82
Screwdriver Set	1	Amazon TaoBao$6	L83

6 more rows in README.md

SO-101 source files

12 files

Files stay in the upstream repository under their own licenses; these links open them there. The 3D model on this page is Motari's conversion of the file named under Simulation.

SO-101 in simulation

Robot description files a simulator or CAD tool can load, linked at the commit they were found.

URDFSimulation/SO101/so101_new_calib.urdfTheRobotStudio/SO-ARM100
URDFSimulation/SO101/so101_old_calib.urdfTheRobotStudio/SO-ARM100

The 3D specimen on this page is converted from Simulation/SO101/so101_new_calib.urdf at fda892c.

Builds of SO-101

0 reviewed

No reviewed builds of SO-101 yet.

A build log records the evidence (photos, a video, your repository), what the build cost, how long it took and what you changed. Each one is checked by Motari (until a maintainer claims this page) before it shows here, and reviewed builds count toward the reproducibility score.

Sources and provenance

Sources

Hardwaregithub.com/TheRobotStudio/SO-ARM100fda892c
Bill of materialsgithub.com/TheRobotStudio/SO-ARM100/blob/main/README.mdfda892c
Build guidehuggingface.co/docs/lerobot/so101

Last push to TheRobotStudio/SO-ARM100: 2026-09-23 (checked 2026-10-01)

How this page was made

Assembled from public sources on 2026-05-14, not yet reviewed by the maintainer. Each figure links to where it is stated; a value the sources do not state reads "not published". Last source review: 2026-06-07 TheRobotStudio/SO-ARM100 README BOM.

Original files stay intact and separately licensed; Motari adds only the summary on this page. Maintainer? Request a correction or removal.

Badge for the README

Maintain SO-101? Show its reproducibility score in the project's README. The badge links back to this page and updates with the score.

Markdown

[![Motari reproducibility score for SO-101](https://motari.io/api/v1/badge/so-101)](https://motari.io/r/so-101)

HTML

<a href="https://motari.io/r/so-101"><img src="https://motari.io/api/v1/badge/so-101" alt="Motari reproducibility score for SO-101" height="20"></a>

Not fully met yet: wiring diagram (partial). The score is read from the project's own sources, so publishing what is missing is what raises it. A score of 90 or more needs a reviewed build. How the score is computed

About SO-101

Licenses

Degrees of freedom

How to build SO-101

Print the structural parts

Flash and ID the servos

Assemble the links

Wire power and data

Calibrate and teleoperate

SO-101 bill of materials

Cost to build

Rows from the source's own parts list 14

SO-101 source files

SO-101 in simulation

Builds of SO-101

Sources and provenance

Sources

How this page was made

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Badge for the README