Koch arm
Robot / hardware buildA printable Dynamixel arm with a separate leader design for teleoperation and robot-learning experiments. [1]
Build & first use →Parts & pricesOfficial websiteUpstream build guideBill of materials
- For
- Makers comfortable with soldering and servo configuration; Robot-learning researchers [1]
- Cost
- USD 245.85 Koch follower only, elbow-to-wrist extensionUSD 450.93 Koch follower + leader, elbow-to-wrist extensionNot included: host computer able to run LeRobot, FDM 3D printer (220 x 220 mm bed or larger), shipping and tax, soldering iron with solder and LM2596 adjustable buck converter module.
- Source rights
- Named licenses are documented by part. Review licenses
- Unknowns
- host computer, operating system not fully established. Review gaps
Source researched · Not tested by us
Sources checked · Research details
Overview
Koch's low-cost arm pairs a printed frame with Dynamixel servos. A second, manually moved leader can control the follower through the repository's teleoperation script. The build combines printing, soldering and individual motor configuration; it is a useful candidate for someone who wants to understand that hardware path into robot learning. [1]
Is this for you?
- Use cases
- Leader/follower teleoperation
- Robot-learning experiments
- Known limitations
- README introductory cost differs from its detailed BOM tables
- Longer and shorter geometries require different idler quantities
- Published instructions say Linux/macOS should work; this is not a tested compatibility matrix
- No measured payload, repeatability or support turnaround established
3D preview
Koch follower arm assembly. Assembly geometry from the upstream STEP. Purchased components are represented; their manufacturing sources and physical fit are not established by this preview.
The 3D preview loads after the page.
Drag to orbit · Scroll or pinch to zoom · Right-drag to pan. Use the view buttons for front, side and top views. The tree shows names supplied by the source; unnamed bodies remain labeled as such.
Download original STEP · File checksums and provenance
Separate bodies can be inspected in the model tree. Explode is a viewing aid, not an assembly sequence.
Model sources
The preview uses the linked original design. Source grouping is retained where present; the caption identifies whether this is an assembly or one component.
Source, license and scale
Source: AlexanderKoch-Koch contributors, revision 0602b0c1e6a67d8f6ab96f81d1378639018d98af. Original and preview: MIT. Preview conversion by Open Source Robotics; original file unchanged. Preview coordinates are centered and rounded to six decimal places. STEP preview triangulated in millimetres. No physical part tested.
Viewer: three-cad-viewer 5.0.7 (MIT license). Confirm scale and manufacturing settings before printing.
What you need
Hardware & parts
Open the parts list with US prices for 2 configurations.
Upstream bill of materials [1]
- Hardware configuration
Desktop robot arm
- Actuators
- Follower: two XL430-W250 and four XL330-M288 in the listed BOM
- Leader: six XL330-M077 in the listed BOM
- Controller
Waveshare serial bus servo driver board connected to a host computer
- Power
Follower: 12V supply plus reducer adjusted to 5V for XL330 servos; leader: 5V supply.
Assembly & first use
Open the upstream getting-started guide [1] · Project documentation [1]
- Select shorter or elbow-to-wrist extension geometry before printing and ordering idlers
- Print STL parts and assemble following the linked video and instructions
- Configure individual motor IDs and baud rates using Dynamixel Wizard
- Adjust follower voltage reducer and check wiring before using teleoperation scripts
- Assembly
Print the selected arm variant, configure motors individually, assemble at documented servo positions, wire the driver and adjust the follower voltage reducer.
- Calibration
Set motor baud rate to 1M and IDs according to selected geometry; install horns at the documented default position. Quantified repeatability is not established.
Cost & sourcing
US delivery · USD · Configuration-specific parts estimates
Leader-follower teleoperation with the repository scripts
Known parts subtotal · additional costs unresolved
USD 450.93
Prices dated Oct 4, 2026.
Baseline: nothing owned
BOM coverage & pricing basis
BOM coverage: partial · Pricing coverage: 13/17 procurement groups · First-task budget: incomplete
README tables reconciled line by line; servo and frame packages include their bolts per ROBOTIS package contents. Not complete: screws for mounting the driver board and voltage reducer to the base, and solder, are not listed.
Known required subtotal across all layers: USD 450.93. Unpriced: Host computer able to run LeRobot, FDM 3D printer (220 x 220 mm bed or larger), Shipping and tax, Soldering iron with solder, LM2596 adjustable buck converter module.
Cost layers & unpriced requirements
Cost layers
| Layer | Known expenditure | Unpriced requirements |
|---|---|---|
| Purchased parts | USD 403.39–USD 405.43 | — |
| Printed parts: material purchase | USD 14.99 | — |
| Fabricated parts | No requirements recorded | — |
| Power & cabling | USD 32.55 | LM2596 adjustable buck converter module |
| Host computer | Unpriced | Host computer able to run LeRobot |
| Sensors & cameras | No requirements recorded | — |
| Tools | Unpriced | FDM 3D printer (220 x 220 mm bed or larger), Soldering iron with solder |
| Shipping & tax | Unpriced | Shipping and tax |
Parts & sourcing
Purchases combine repeated requirements before rounding to supplier packs. Shared purchases appear once. Printed material consumption and whole-spool purchase costs are different. Under “Other offers & price history”, historical observations may be excluded from today's subtotal. Broken or unavailable listings do not count.
| Part / requirement | Quantity & ownership | Lowest eligible purchase |
|---|---|---|
| DYNAMIXEL XL430-W250-TRequired · Purchased parts | 2 each | USD 55.00 ROBOTIS America2 pack(s) × 1 each; minimum 1 pack(s) · in stockChecked by us · Oct 4, 2026
Price sourcesDYNAMIXEL XL430-W250-TOther offers & price historyROBOTIS America (linked from Koch README)USD 50.00 / 1 each; minimum 1 pack(s). Upstream-published · Apr 7, 2024 · unknown, link unknown.Koch README "Required Materials" cost column at pinned revision 0602b0c. The figures ($258 and $183 totals; $100 for 2 XL430, $96 for 4 XL330-M288, $144 for 6 XL330-M077) are present in every README revision from 265535c (2024-04-07) to the newest (retained source evidence), so the price is dated to that earliest revision. Per-unit figures divide the listed line cost by its quantity.Koch low_cost_robot README bill of materials · Koch README commit history and price presence scan ROBOTIS AmericaUSD 27.50 / 1 each; minimum 1 pack(s). Checked by us · Oct 4, 2026 · in stock, link working.schema.org Offer price 27.50 USD, availability http://schema.org/InStock.DYNAMIXEL XL430-W250-T |
| DYNAMIXEL XL330-M288-TRequired · Purchased parts | 4 each | USD 109.96 ROBOTIS America4 pack(s) × 1 each; minimum 1 pack(s) · in stockChecked by us · Oct 4, 2026
Price sourcesDYNAMIXEL XL330-M288-TOther offers & price historyROBOTIS America (linked from Koch README)USD 24.00 / 1 each; minimum 1 pack(s). Upstream-published · Apr 7, 2024 · unknown, link unknown.Same observation notes as DYNAMIXEL XL430-W250-T above.Koch low_cost_robot README bill of materials · Koch README commit history and price presence scan ROBOTIS AmericaUSD 27.49 / 1 each; minimum 1 pack(s). Checked by us · Oct 4, 2026 · in stock, link working.schema.org Offer price 27.49 USD, availability http://schema.org/InStock.DYNAMIXEL XL330-M288-T |
| ROBOTIS FPX330-H101 hinge frame and idler (per idler)Required · Purchased parts | 3 each | USD 22.54 ROBOTIS America2 pack(s) × 4 each; minimum 1 pack(s) · in stockChecked by us · Oct 4, 2026
Price sourcesFPX330-H101 4pcs SetRequirement notesThree idlers for the elbow-to-wrist extension geometry. Other offers & price historyROBOTIS America (linked from Koch README)USD 10.00 / 4 each; minimum 1 pack(s). Upstream-published · Apr 7, 2024 · unknown, link unknown.Same observation notes as DYNAMIXEL XL430-W250-T above.Koch low_cost_robot README bill of materials · Koch README commit history and price presence scan ROBOTIS AmericaUSD 11.27 / 4 each; minimum 1 pack(s). Checked by us · Oct 4, 2026 · in stock, link working.schema.org Offer price 11.27 USD, availability http://schema.org/InStock.FPX330-H101 4pcs Set |
| ROBOTIS HN11-I101 idler set (XL430)Required · Purchased parts | 1 each | USD 8.05 ROBOTIS America1 pack(s) × 1 each; minimum 1 pack(s) · in stockChecked by us · Oct 4, 2026
Price sourcesHN11-I101 SetRequirement notesOne set as listed upstream. Other offers & price historyROBOTIS America (linked from Koch README)USD 7.00 / 1 each; minimum 1 pack(s). Upstream-published · Apr 7, 2024 · unknown, link unknown.Same observation notes as DYNAMIXEL XL430-W250-T above.Koch low_cost_robot README bill of materials · Koch README commit history and price presence scan ROBOTIS AmericaUSD 8.05 / 1 each; minimum 1 pack(s). Checked by us · Oct 4, 2026 · in stock, link working.schema.org Offer price 8.05 USD, availability http://schema.org/InStock.HN11-I101 Set |
| Serial bus servo driver board (Waveshare-type, USB)Required · Purchased parts | 1 each | USD 24.94 Wonrabai Electronics2 pack(s) × 1 each; minimum 1 pack(s) · in stockChecked by us · Oct 4, 2026
Requirement notesSame listing as upstream (a.co/d/7C3RUYU -> B0CTMM4LWK). Other offers & price historyAmazon listing linked from upstream READMEUSD 10.60 / 1 each; minimum 1 pack(s). Upstream-published · Jun 2, 2025 · unknown, link unknown.Upstream README "Unit Cost (US)" column at pinned revision 5f6d2b8 (2026-09-23). The figures (13.89 servo; 121.94 and 229.88 totals) appear unchanged in every README revision from 2415d54 (2025-06-02) to the pinned revision (20 consecutive revisions; retained source evidence), so the price is dated to that earliest revision. Supplier MOQ not independently checked; the table prices single units for the listed amount.SO-ARM100 README bill of materials · SO-ARM100 README commit history and price presence scan Wonrabai ElectronicsUSD 12.47 / 1 each; minimum 1 pack(s). Checked by us · Oct 4, 2026 · in stock, link working.Listing page fetched and buy box read on 2026-10-04; seller: Wonrabai Electronics.Serial Bus Servo Driver Board, Support 253 ST/SC Serial Bus Servos |
| LM2596 adjustable buck converter moduleRequired · Power & cabling | 1 each | Unpriced
Requirement notesOne of the six-pack per follower. Other offers & price historyAmazon listing linked from Koch READMEUSD 10.00 / 6 each; minimum 1 pack(s). Upstream-published · Apr 7, 2024 · unknown, link unknown.Same observation notes as DYNAMIXEL XL430-W250-T above.Koch low_cost_robot README bill of materials · Koch README commit history and price presence scan Amazon.com marketplace (no featured offer)Unpriced / 6 each; minimum 1 pack(s). Checked by us · Unknown · out of stock, link working.Buy box read on 2026-10-04; seller: None; availability: Currently unavailable. We don't know when or if this item will be back in stock.. Upstream short link https://a.co/d/cy02ADW.Queta 6 Pieces LM2596s DC to DC Buck Converter Step Down Voltage Regulator Power Module 3.2-40V to 1.25-35V 3A High Efficiency DC Voltage Stabilizer Volt Transformer LM2596 DC-DC Buck Converter |
| 12 V 5 A power supply, barrel plugRequired · Power & cabling | 1 each | USD 11.99 Mo-gu1 pack(s) × 1 each; minimum 1 pack(s) · lowChecked by us · Oct 4, 2026
Other offers & price historyAmazon listing linked from Koch READMEUSD 12.00 / 1 each; minimum 1 pack(s). Upstream-published · Apr 7, 2024 · unknown, link unknown.Same observation notes as DYNAMIXEL XL430-W250-T above.Koch low_cost_robot README bill of materials · Koch README commit history and price presence scan Mo-guUSD 11.99 / 1 each; minimum 1 pack(s). Checked by us · Oct 4, 2026 · low, link working.Buy box read on 2026-10-04; seller: Mo-gu; availability: Only 14 left in stock - order soon.. Upstream short link https://a.co/d/40o8uMN.Facmogu 12V 5A Power Supply Adapter, AC 100-240V to DC 12V Converter |
| Dupont jumper wire kit (M-F, M-M, F-F)Required · Power & cabling | 1 each | USD 6.98 ELEGOO Official US1 pack(s) × 1 each; minimum 1 pack(s) · in stockChecked by us · Oct 4, 2026
Other offers & price historyAmazon listing linked from Koch READMEUSD 7.00 / 1 each; minimum 1 pack(s). Upstream-published · Apr 7, 2024 · unknown, link unknown.Same observation notes as DYNAMIXEL XL430-W250-T above.Koch low_cost_robot README bill of materials · Koch README commit history and price presence scan ELEGOO Official USUSD 6.98 / 1 each; minimum 1 pack(s). Checked by us · Oct 4, 2026 · in stock, link working.Buy box read on 2026-10-04; seller: ELEGOO Official US; availability: In Stock. Upstream short link https://a.co/d/hQfk2cb.ELEGOO 120pcs Multicolored Dupont Wire M-F, M-M, F-F for Breadboard Jumper |
| Small bar / trigger clamp for mounting the arm baseRequired · Purchased parts | 1 each | USD 7.95 Mr. Pen1 pack(s) × 2 each; minimum 1 pack(s) · in stockChecked by us · Oct 4, 2026
Requirement notesUpstream links a BESSEY CM30 3" C-clamp (USD 6); its listing showed no price on 2026-10-04, so generic clamp offers are used. Other offers & price historyAmazon listing linked from upstream README (two-arm table)USD 9.00 / 4 each; minimum 1 pack(s). Upstream-published · Jun 2, 2025 · unknown, link unknown.Same observation notes as Serial bus servo driver board (Waveshare-type, USB) above.SO-ARM100 README bill of materials · SO-ARM100 README commit history and price presence scan Amazon listing linked from upstream README (follower table)USD 5.00 / 2 each; minimum 1 pack(s). Upstream-published · Jun 2, 2025 · unknown, link unknown.Same observation notes as Serial bus servo driver board (Waveshare-type, USB) above.SO-ARM100 README bill of materials · SO-ARM100 README commit history and price presence scan PartstockUSD 9.99 / 4 each; minimum 1 pack(s). Checked by us · Oct 4, 2026 · in stock, link working.Listing page fetched and buy box read on 2026-10-04; seller: Partstock.TAODAN 4PCS 4 Inch Trigger Quick Grip Clamps Bar Clamp Trigger Quick Grip Clamp Single Hand Ratchet Woodworking Clamp for Wood Bonding Processes Mr. PenUSD 7.95 / 2 each; minimum 1 pack(s). Checked by us · Oct 4, 2026 · in stock, link working.Listing page fetched and buy box read on 2026-10-04; seller: Mr. Pen.Mr. Pen- Bar Clamps for Woodworking, 6", 2 Pack, Orange |
| USB-A to USB-C cableRequired · Power & cabling | 1 each | USD 7.19 etguuds1 pack(s) × 2 each; minimum 1 pack(s) · in stockChecked by us · Oct 4, 2026
Requirement notesREADME: a USB-C cable is necessary to connect the driver board. Other offers & price historyAmazon listing linked from upstream READMEUSD 7.00 / 2 each; minimum 1 pack(s). Upstream-published · Jun 2, 2025 · unknown, link unknown.Same observation notes as Serial bus servo driver board (Waveshare-type, USB) above.SO-ARM100 README bill of materials · SO-ARM100 README commit history and price presence scan etguudsUSD 7.19 / 2 each; minimum 1 pack(s). Checked by us · Oct 4, 2026 · in stock, link working.Listing page fetched and buy box read on 2026-10-04; seller: etguuds.etguuds 6.6ft USB A to USB C Cable, 2Pack Fast Charging Cord Type C Charger |
| Soldering iron with solderRequired · Tools | 1 each | Unpriced
Requirement notesWires are soldered onto the voltage reducer. Other offers & price historyNo offer recorded. |
| DYNAMIXEL XL330-M077-TRequired · Purchased parts | 6 each | USD 164.94 ROBOTIS America6 pack(s) × 1 each; minimum 1 pack(s) · in stockChecked by us · Oct 4, 2026
Price sourcesDYNAMIXEL XL330-M077-TOther offers & price historyROBOTIS America (linked from Koch README)USD 24.00 / 1 each; minimum 1 pack(s). Upstream-published · Apr 7, 2024 · unknown, link unknown.Same observation notes as DYNAMIXEL XL430-W250-T above.Koch low_cost_robot README bill of materials · Koch README commit history and price presence scan ROBOTIS AmericaUSD 27.49 / 1 each; minimum 1 pack(s). Checked by us · Oct 4, 2026 · in stock, link working.Same observation notes as DYNAMIXEL XL330-M288-T above.DYNAMIXEL XL330-M077-T |
| ROBOTIS FPX330-S101 side frame (per frame)Required · Purchased parts | 4 each | USD 10.01 ROBOTIS America1 pack(s) × 4 each; minimum 1 pack(s) · in stockChecked by us · Oct 4, 2026
Price sourcesFPX330-S101 4pcs SetRequirement notesOne set of four, as listed upstream. Other offers & price historyROBOTIS America (linked from Koch README)USD 7.00 / 4 each; minimum 1 pack(s). Upstream-published · Apr 7, 2024 · unknown, link unknown.Same observation notes as DYNAMIXEL XL430-W250-T above.Koch low_cost_robot README bill of materials · Koch README commit history and price presence scan ROBOTIS AmericaUSD 10.01 / 4 each; minimum 1 pack(s). Checked by us · Oct 4, 2026 · in stock, link working.schema.org Offer price 10.01 USD, availability http://schema.org/InStock.FPX330-S101 4pcs Set |
| ROBOTIS FPX330-H101 hinge frame and idler (per idler)Required · Purchased parts | 3 each | Included in shared purchase above
Requirement notesThree idlers for the extension geometry. Other offers & price historyROBOTIS America (linked from Koch README)USD 10.00 / 4 each; minimum 1 pack(s). Upstream-published · Apr 7, 2024 · unknown, link unknown.Same observation notes as DYNAMIXEL XL430-W250-T above.Koch low_cost_robot README bill of materials · Koch README commit history and price presence scan ROBOTIS AmericaUSD 11.27 / 4 each; minimum 1 pack(s). Checked by us · Oct 4, 2026 · in stock, link working.FPX330-H101 4pcs Set |
| Serial bus servo driver board (Waveshare-type, USB)Required · Purchased parts | 1 each | Included in shared purchase above
Other offers & price historyAmazon listing linked from upstream READMEUSD 10.60 / 1 each; minimum 1 pack(s). Upstream-published · Jun 2, 2025 · unknown, link unknown.SO-ARM100 README bill of materials · SO-ARM100 README commit history and price presence scan Wonrabai ElectronicsUSD 12.47 / 1 each; minimum 1 pack(s). Checked by us · Oct 4, 2026 · in stock, link working.Serial Bus Servo Driver Board, Support 253 ST/SC Serial Bus Servos |
| 5 V 2 A power supply, barrel plugRequired · Power & cabling | 1 each | USD 6.39 GUOHONGZHAN1 pack(s) × 1 each; minimum 1 pack(s) · in stockChecked by us · Oct 4, 2026
Other offers & price historyAmazon listing linked from Koch READMEUSD 6.00 / 1 each; minimum 1 pack(s). Upstream-published · Apr 7, 2024 · unknown, link unknown.Same observation notes as DYNAMIXEL XL430-W250-T above.Koch low_cost_robot README bill of materials · Koch README commit history and price presence scan GUOHONGZHANUSD 6.39 / 1 each; minimum 1 pack(s). Checked by us · Oct 4, 2026 · in stock, link working.Buy box read on 2026-10-04; seller: GUOHONGZHAN; availability: In Stock. Upstream short link https://a.co/d/5u90NVp.5V 2A Power Adapter Supply 10W DC 5V 2A 1.5A 1A Wall Plug Power Cord |
| Small bar / trigger clamp for mounting the arm baseRequired · Purchased parts | 1 each | Included in shared purchase above
Other offers & price historyAmazon listing linked from upstream README (two-arm table)USD 9.00 / 4 each; minimum 1 pack(s). Upstream-published · Jun 2, 2025 · unknown, link unknown.Same observation notes as Serial bus servo driver board (Waveshare-type, USB) above.SO-ARM100 README bill of materials · SO-ARM100 README commit history and price presence scan Amazon listing linked from upstream README (follower table)USD 5.00 / 2 each; minimum 1 pack(s). Upstream-published · Jun 2, 2025 · unknown, link unknown.Same observation notes as Serial bus servo driver board (Waveshare-type, USB) above.SO-ARM100 README bill of materials · SO-ARM100 README commit history and price presence scan PartstockUSD 9.99 / 4 each; minimum 1 pack(s). Checked by us · Oct 4, 2026 · in stock, link working.TAODAN 4PCS 4 Inch Trigger Quick Grip Clamps Bar Clamp Trigger Quick Grip Clamp Single Hand Ratchet Woodworking Clamp for Wood Bonding Processes Mr. PenUSD 7.95 / 2 each; minimum 1 pack(s). Checked by us · Oct 4, 2026 · in stock, link working.Mr. Pen- Bar Clamps for Woodworking, 6", 2 Pack, Orange |
| USB-A to USB-C cableRequired · Power & cabling | 1 each | Included in shared purchase above
Other offers & price historyAmazon listing linked from upstream READMEUSD 7.00 / 2 each; minimum 1 pack(s). Upstream-published · Jun 2, 2025 · unknown, link unknown.Same observation notes as Serial bus servo driver board (Waveshare-type, USB) above.SO-ARM100 README bill of materials · SO-ARM100 README commit history and price presence scan etguudsUSD 7.19 / 2 each; minimum 1 pack(s). Checked by us · Oct 4, 2026 · in stock, link working.etguuds 6.6ft USB A to USB C Cable, 2Pack Fast Charging Cord Type C Charger |
| Host computer able to run LeRobotRequired · Host computer | 1 each | Unpriced
Requirement notesComputer running the Dynamixel SDK control scripts. Other offers & price historyNo offer recorded. |
| FDM 3D printer (220 x 220 mm bed or larger)Required · Tools | 1 each | Unpriced
Requirement notesRequired for the self-print route. Other offers & price historyNo offer recorded. |
| PLA filament, 1.75 mmRequired · Printed parts: material purchase | 100.8 g | USD 14.99 eSUN official Store1 pack(s) × 1000 g; minimum 1 pack(s) · in stockChecked by us · Oct 4, 2026
Requirement notesMaterial consumption: 86.3–100.8 g. Print method and assumptions are under Printing & required equipment. Other offers & price historyeSUN official StoreUSD 14.99 / 1000 g; minimum 1 pack(s). Checked by us · Oct 4, 2026 · in stock, link working.Buy box read on 2026-10-04; seller: eSUN official Store; variants: Silver, 1KG.eSUN PLA Basic Filament 1.75mm 3D Printer Filament 1KG Silver |
| PLA filament, 1.75 mmRequired · Printed parts: material purchase | 76.9 g | Included in shared purchase above
Requirement notesMaterial consumption: 63.5–76.9 g. Print method and assumptions are under Printing & required equipment. Other offers & price historyeSUN official StoreUSD 14.99 / 1000 g; minimum 1 pack(s). Checked by us · Oct 4, 2026 · in stock, link working.eSUN PLA Basic Filament 1.75mm 3D Printer Filament 1KG Silver |
Printing & required equipment
follower-frame: 86.3–100.8 g material consumption; buy whole supplier packs.
Print method, fit & assumptions
Slicer: PrusaSlicer-2.9.6 based on Slic3r (with GUI support); each file sliced separately (retained source evidence): low = 2 perimeters and 15% infill, high = PrusaSlicer defaults (3 perimeters, 20% infill). Upstream states only that the moving gripper part needs supports; material, nozzle, layer height and infill are not stated, so PLA, 0.4 mm nozzle and 0.2 mm layers are assumed and infill/perimeters span a stated range. Elbow-to-wrist extension geometry; both elbow_to_wrist files are included (the short piece may be unused, about 5 g). arm.stl / leader_arm.stl are assembly exports and are not printed. No skirt or brim; one successful print, no reprint allowance.
hardware/follower/stl/base.stl · quantity 1hardware/follower/stl/elbow_to_wrist.stl · quantity 1hardware/follower/stl/elbow_to_wrist_extension.stl · quantity 1hardware/follower/stl/gripper_moving_part.stl · quantity 1hardware/follower/stl/gripper_static_part.stl · quantity 1hardware/follower/stl/shoulder_rotation.stl · quantity 1hardware/follower/stl/shoulder_to_elbow.stl · quantity 1leader-frame: 63.5–76.9 g material consumption; buy whole supplier packs.
Print method, fit & assumptions
Slicer: PrusaSlicer-2.9.6 based on Slic3r (with GUI support); each file sliced separately (retained source evidence): low = 2 perimeters and 15% infill, high = PrusaSlicer defaults (3 perimeters, 20% infill). Upstream states only that the moving gripper part needs supports; material, nozzle, layer height and infill are not stated, so PLA, 0.4 mm nozzle and 0.2 mm layers are assumed and infill/perimeters span a stated range. Elbow-to-wrist extension geometry; both elbow_to_wrist files are included (the short piece may be unused, about 5 g). arm.stl / leader_arm.stl are assembly exports and are not printed. No skirt or brim; one successful print, no reprint allowance.
hardware/leader/stl/base.stl · quantity 1hardware/leader/stl/elbow_to_wrist.stl · quantity 1hardware/leader/stl/elbow_to_wrist_extension.stl · quantity 1hardware/leader/stl/gripper_handle.stl · quantity 1hardware/leader/stl/gripper_trigger.stl · quantity 1hardware/leader/stl/shoulder_to_elbow.stl · quantity 1Required host computers, cameras and tools are separate from the Parts total. They appear in the required subtotal only where priced or explicitly owned. Labor: unknown.
Prices are dated US listings or upstream-published figures, not checkout guarantees. Shipping and tax assumptions remain visible above. We don’t earn from these links.
Download reviewed data
Full cost and sourcing receipt (JSON)
Koch follower + leader, elbow-to-wrist extension baseline CSV
Earlier upstream estimates and vendor offers
Earlier estimates
These are the project's published parts estimates, not current shop prices. They do not cover a complete build.
Both prices were checked 2026-09-30. The following applies to both versions.
| Included | Listed servos, driver board, power supply, clamp and listed accessory packs |
|---|---|
| Not included | 3D printed parts/material; Host computer; Tools; USB-C cable; Assembly work; Camera or learning compute |
| Stock | Supplier stock not checked. |
| Delivery and tax | Not established; no landed total. |
Price details
Historical upstream table; not a fresh supplier quote. Discounts are not assumed.
US-linked upstream supplier examples; destination not established · Checked 2026-09-30 · Quantity 1
Printed parts, host, USB-C connection and assembly tools; exact geometry must be selected.
Project notes
Use the detailed tables as the starting point
The README opens with approximate prices of $250 for the follower and $180 for the leader, but its detailed tables list $258 and $183, or $441 for the pair. Those figures have stood since April 2024. [1]
At US prices checked on October 4, 2026, the known parts subtotal for the elbow-to-wrist-extension build is USD 450.93 for the pair and USD 245.85 for the follower alone, including one 1 kg PLA spool for USD 14.99, most of which is left over, and the USB-C cable the README says the driver board needs. Servo prices have moved in both directions at ROBOTIS America: the XL430-W250-T now lists at USD 27.50, against the table's USD 50, while each XL330 lists at USD 27.49, against USD 24. The voltage reducer six-pack the README links is currently unavailable; the README's April 2024 USD 10 remains in the price history but is excluded from both subtotals. A current replacement and its price are unresolved. [1] [5]
These are subtotals, not complete budgets. The tables leave out the screws for mounting the driver board and voltage reducer, solder and a soldering iron; shipping, tax, a computer and a 3D printer are also extra. Our printing estimate slices each part separately, because the README states no print settings beyond supports for the moving gripper part: about 86–101 g of PLA for the follower and 64–77 g for the leader. Those figures count both elbow-to-wrist pieces, although the short one (about 5 g) may be unused, and assume every print succeeds. The full-arm STL files are assembly exports and are not printed. [1] [4] [5]
The guide also distinguishes shorter and elbow-to-wrist-extension geometries. That changes the required idler count: three XL330 idlers per arm for the extension geometry and two for the shorter one, sold in sets of four. Select the geometry and reconcile its files against the parts list before ordering; the headline price does not identify a fully specified build. [1] [4]
The follower requires two voltage levels
The listed follower uses two XL430 and four XL330 servos. Its 12V supply feeds a reducer that the guide instructs the builder to adjust to 5V for the XL330 chain. The leader uses six XL330 servos and a 5V supply. Both routes require motor IDs and baud rates to be configured individually. Follow the upstream wiring and assembly instructions for the chosen geometry. [1]
The guide describes Linux and macOS connections as expected to work, but supplies no validated host requirements matrix. We have not run the control scripts, verified the wiring or measured motion. [1]
What the local source copy contains
The reviewed commit includes follower and leader STL, STEP and Fusion files, plus Python control and simulation code. Its root license is MIT. That repository license does not establish the design or firmware terms of the separately purchased Dynamixel servos or driver board. [2] [4]
No published stable release was found in the checked release listing, so this review pins commit 0602b0c1e6a67d8f6ab96f81d1378639018d98af as a source snapshot. A snapshot makes the reviewed files identifiable; it does not establish a tested build configuration. [3]
Before selecting this arm for a supported build, we still need a reconciled variant-specific shopping list, current sourcing, a repeatable calibration and motion test, and measured troubleshooting effort. This is a researched candidate; we have not established our ability to build or support it.
What we checked
Source-researched by Codex; no physical build, purchase or testing performed for this review. No affiliate links added.
Not yet established
- Requirements: operating system, host computer
Updates
- Upstream last updated
- Sep 21, 2024 [3]
- Latest release
- Not established
- Profile updated
- Oct 4, 2026
- Sources last checked
- Sep 30, 2026
- Next review
- Oct 30, 2026
- Reviewed revision
- 0602b0c1e6a67d8f6ab96f81d1378639018d98af (default-branch snapshot; no published stable release found) · combined hardware and software repository
Source files and licenses
Printable CAD and control code are available; this does not establish open designs or firmware for purchased servos and electronics.
| Layer | Availability / license |
|---|---|
| mechanical design | available · MIT Repository root license; external linked material and purchased components require separate checks. [2] [4] |
| electronics | not found · License not fully assessed Reviewed arm repository and build guide specify purchased servo/driver components; complete component designs/firmware were not established within that scope. [1] [4] |
| firmware | not found · License not fully assessed Reviewed arm repository and build guide specify purchased servo/driver components; complete component designs/firmware were not established within that scope. [1] [4] |
| software | available · MIT Repository root license; external linked material and purchased components require separate checks. [2] [4] |
| documentation | available · MIT Repository root license; external linked material and purchased components require separate checks. [1] [2] |
No specific model or dataset is included in this physical arm configuration.
References
Each source links to the exact revision we read. “Used for” shows where this page relies on it.
Project sources
- S001 Koch arm build guide and BOM
BOM tables list $258 follower and $183 leader; opening approximations are $250 and $180. Lists actuators, printing, assembly, voltage setup and example scripts.Revision, date & where cited
Alexander Koch / low_cost_robot contributors · github.com · revision
0602b0c· Accessed Sep 30, 2026
Used for: Overview, Is this for you?, What you need, Hardware & parts and 5 more - S002 Repository MIT license
MIT repository root license; purchased electronics and external artifacts are not assigned this license.Revision, date & where cited
Alexander Koch / low_cost_robot contributors · github.com · revision
0602b0c· Accessed Sep 30, 2026
Used for: What the local source copy contains, Source files and licenses - S003 Repository snapshot
Pinned default-branch commit; release API returned no published stable release. Repository metadata is not independent adoption evidence.Revision, date & where cited
Alexander Koch / low_cost_robot contributors · github.com · revision
0602b0c· Accessed Sep 30, 2026
Used for: What the local source copy contains, What we checked - S004 Mechanical and control source inventory
Follower and leader directories contain STL, STEP and Fusion assemblies; source tree contains Python control and simulation files.Revision, date & where cited
Alexander Koch / low_cost_robot contributors · github.com · revision
0602b0c· hardware/, dynamixel.py and simulation.py · Accessed Sep 30, 2026
Used for: Use the detailed tables as the starting point, What the local source copy contains, Source files and licenses
Our checks and receipts
- S005 Koch arm US cost and sourcing estimate receipt
Line-level US offers, price dates, printed-part slicing and rollups for the Koch arm configurations.Revision, date & where cited
Open Source Robotics · opensourcerobotics.dev · Rollups as of 2026-10-04 · Accessed Oct 4, 2026
Used for: Use the detailed tables as the starting point
Videos
- S006 Low-Cost Robot Arm Assembly (YouTube video)
Video from the project’s own channel (Alexander Koch), linked from the project’s own documentation. Not reviewed by us for accuracy.Revision, date & where cited
YouTube video Alexander Koch · youtube.com · Accessed Oct 4, 2026
Correction guidance · Discussion is not enabled · Profile format 0.7.0-draft.5
Change history
2026-10-04 — Staged v0.7 cost and sourcing estimate: line-level BOM, US offers and printed-part slicing. Not yet reviewed or published.
2026-10-04 — Staged draft.5 estimate excludes confirmed broken/unavailable listings while preserving historical prices. Not published.
2026-10-04 — Added 1 YouTube reference(s) (S006): official channel or videos linked from the pinned upstream sources. Existing claims, source-check dates and evidence are unchanged.