Auto-assembled, not yet reviewed

SO-ARM100 / SO-ARM101 (Standard Open Arm)

Deprecated first Standard Open Arm, superseded by SO-101: low-cost printable leader/follower arm.

Apache-2.0
robot arm6 DoF
$123source total

Reproducibility83/100Strong source coverage, unverifiedCADBOMWIREFWBUILDLICREPHow it is computed

SO-ARM100 / SO-ARM101 (Standard Open Arm) open-source 6-DoF robot arm, 3D render from so100.urdf

main assembly 3D · so100.urdf

Source record

Source: TheRobotStudio/SO-ARM100 @5f6d2b8
7.6k stars, last push 2026-09-23
HW license: Apache-2.0
Cost: $123source total, follower arm only
Lifecycle: Deprecated
Engine: v3.1.1
Checked: 2026-09-30
Model: so100.urdf@fda892crendered 2026-06-08
Envelope: 111 × 170 × 305 mmas modelled, default pose

Maintain SO-ARM100 / SO-ARM101 (Standard Open Arm)? Claim this page to correct it.

SO-ARM100 / SO-ARM101 (Standard Open Arm) 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 + 117 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):)5f6d2b8
partialWiring diagramReviewedThe LeRobot SO-100 guide describes the wiring in text (USB and power to the controller board, jumper setting, 3-pin cables chained motor to motor) with routing photos; no diagram.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 so100 page) is the SO-100 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 firmware5f6d2b8
metBuild instructionsReviewedLeRobot's SO-100 guide has 27 numbered assembly steps with 29 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
- LICENSE5f6d2b8
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 5f6d2b8, 3 items reviewed by hand

How this score is computed

About SO-ARM100 / SO-ARM101 (Standard Open Arm)

SO-ARM100 is The Robot Studio's first Standard Open Arm, a low-cost printable 6-DoF arm used with LeRobot. Upstream marks the SO-100 docs as deprecated in favour of SO-101. The BOM is the SO100.md table for one follower arm, without print costs. Upstream says the six leader-arm motors need their gears removed.

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-ARM100 / SO-ARM101 (Standard Open Arm)

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 files are provided for several printer bed sizes, plus STEP files. Upstream recommends PLA at 13% infill with a 0.4 mm nozzle at 0.2 mm layers or a 0.6 mm nozzle at 0.4 mm layers.
Motari summaryhuggingface.co/docs/lerobot/so100
ID the servos
Assign each Feetech STS3215 bus servo a unique ID with the motor control board before assembly.
Motari summaryhuggingface.co/docs/lerobot/so100
Assemble the links
Bolt the printed links to the servo horns from the base up, following the assembly guide. Upstream says to remove the gears of the six leader-arm motors before assembly.
Upstream stephuggingface.co/docs/lerobot/so100
Wire power and data
Daisy-chain the bus servos and connect the control board to USB. Verify wiring against the docs.
Upstream stephuggingface.co/docs/lerobot/so100
Calibrate and teleoperate
Run the LeRobot calibration, then drive the follower from the leader arm.
Motari summaryhuggingface.co/docs/lerobot/so100

Print timenot published

Assembly time2 h

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

SO-ARM100 / SO-ARM101 (Standard Open Arm) bill of materials

6 rows

Cost to build

$123USDsource total

follower arm only$123source total
leader and follower pair$232source 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-ARM100 / SO-ARM101 (Standard Open Arm) parts, as the source lists them (read 2026-09-30). Prices are the source's, not checked against vendors.

SO-ARM100 / SO-ARM101 (Standard Open Arm) bill of materials
Part	Qty	Spec	Source	Confidence
STS3215 ServoFollower-arm servos from the SO-100 BOM table	6	Feetech STS3215 7.4V bus servo	Alibaba / TaoBao$14 eachTheRobotStudio/SO-ARM100 SO100.md line 34	high
Motor Control BoardUSB servo control board	1	Waveshare serial bus servo board	Amazon / TaoBao$11TheRobotStudio/SO-ARM100 SO100.md line 35	high
USB-C Cable 2 pcsCable pair listed as one BOM line	1	USB-C cable, 2 pieces	Amazon / TaoBao$7TheRobotStudio/SO-ARM100 SO100.md line 36	high
Power SupplyDC power supply for the follower arm	1	5V supply in upstream BOM	Amazon / TaoBao$10TheRobotStudio/SO-ARM100 SO100.md line 37	high
Table Clamp 2pcsFollower-arm table clamp set	1	2-piece clamp set	Amazon / TaoBao$5TheRobotStudio/SO-ARM100 SO100.md line 38	high
Screwdriver SetAssembly tool listed in the source BOM	1	precision screwdriver set	Amazon / TaoBao$6TheRobotStudio/SO-ARM100 SO100.md line 39	high

Rows from the source's own parts list 12

SO100.md@5f6d2b8markdown

Source row	Qty	Price and vendor	Line
STS3215 Servo	12	Alibaba TaoBao$15	L22
Motor Control Board	2	Amazon TaoBao$11	L23
USB-C Cable 2 pcs	1	Amazon TaoBao$7	L24
Power Supply	2	Amazon TaoBao$10	L25
Table Clamp 4pcs	1	Amazon TaoBao$9	L26
Screwdriver Set	1	Amazon TaoBao$6	L27
STS3215 Servo	6	Alibaba TaoBao$14	L34
Motor Control Board	1	Amazon TaoBao$11	L35

4 more rows in SO100.md

SO-ARM100 / SO-ARM101 (Standard Open Arm) 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-ARM100 / SO-ARM101 (Standard Open Arm) in simulation

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

URDFSimulation/SO100/so100.urdfTheRobotStudio/SO-ARM100

The 3D specimen on this page is converted from Simulation/SO100/so100.urdf at fda892c.

Builds of SO-ARM100 / SO-ARM101 (Standard Open Arm)

0 reviewed

No reviewed builds of SO-ARM100 / SO-ARM101 (Standard Open Arm) 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-ARM1005f6d2b8
Bill of materialsgithub.com/TheRobotStudio/SO-ARM100/blob/main/SO100.md5f6d2b8
Build guidehuggingface.co/docs/lerobot/so100

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

How this page was made

Assembled from public sources on 2026-06-04, 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-ARM100 / SO-ARM101 (Standard Open Arm)? 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-ARM100 / SO-ARM101 (Standard Open Arm)](https://motari.io/api/v1/badge/so-arm100)](https://motari.io/r/so-arm100)

HTML

<a href="https://motari.io/r/so-arm100"><img src="https://motari.io/api/v1/badge/so-arm100" alt="Motari reproducibility score for SO-ARM100 / SO-ARM101 (Standard Open Arm)" 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-ARM100 / SO-ARM101 (Standard Open Arm)

Licenses

Degrees of freedom

How to build SO-ARM100 / SO-ARM101 (Standard Open Arm)

Print the structural parts

ID the servos

Assemble the links

Wire power and data

Calibrate and teleoperate

SO-ARM100 / SO-ARM101 (Standard Open Arm) bill of materials

Cost to build

Rows from the source's own parts list 12

SO-ARM100 / SO-ARM101 (Standard Open Arm) source files

SO-ARM100 / SO-ARM101 (Standard Open Arm) in simulation

Builds of SO-ARM100 / SO-ARM101 (Standard Open Arm)

Sources and provenance

Sources

Related links

How this page was made

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Lineage

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Badge for the README