---
title: "Strain-wave cobot joint: bill of materials"
description: "Frameless motor, strain-wave gear, brake and motor encoder: ZeroErr eRob 80 T class: what is inside, who makes each part, cost against raw material and who keeps the margin. Half the price is the strain-wave gear, whose steel costs about ten cents; its incumbent maker keeps nearly a third of what it charges."
canonical: https://actuatorlist.com/bom/harmonic-frameless
last-updated: 2026-11-07
---
# Strain-wave cobot joint

Frameless motor, strain-wave gear, brake and motor encoder: ZeroErr eRob 80 T class. The classic industrial and cobot joint. A handful of incumbent component makers set its price.

- Price: $1.44k[^1]. Off-the-shelf price for one integrated joint.
- Raw material in it: $5.27 at 2026-09 prices, so an idiot index of 273x.
- Half the price is the strain-wave gear, whose steel costs about ten cents; its incumbent maker keeps nearly a third of what it charges.

Interactive page: https://actuatorlist.com/bom/harmonic-frameless (deep link `#node=<id>`). JSON: https://actuatorlist.com/api/v1/bom/harmonic-frameless. As of November 2026.

## Bill of materials

Unit cost is what the next tier pays for one unit. Raw material and the idiot index cover all units in one actuator. Idiot index is unit cost over raw-material cost; step is unit cost over the cost of its inputs, shown only where every input has a cost. Masses come from our model of each part's geometry, not from a scale. "Typical maker" means the real supplier is not public and a listed maker of that part stands in for its margin.

| Node | Qty | Mass | Unit cost | Raw material | Idiot index | Step | Maker, gross margin |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Strain-wave joint (`harmonic-frameless`)[^1] | 1 | 968 g (model) | $1.44k[^1] | $5.27 | 273x | 1x | ZeroErr |
| · Strain-wave gear (`strain-wave-gear`)[^1] | 1 | 169 g (model) | $741-741[^2] (model, 2026) | $0.10 | 7,469x | n/a | Harmonic Drive Systems, margin 30%[^3] (model, 2026-03) (typical maker, stands in) |
| · · Wave generator (`wave-generator`) (inferred)[^1] | 1 | 42 g (model) | not public | $0.03 | n/a | n/a | not public |
| · · · Elliptical cam (`wave-cam`) (inferred)[^1] | 1 | 33 g (model) | not public | $0.02 | n/a | n/a | not public |
| · · · Flexible bearing (`flex-bearing`) (inferred)[^1] | 1 | 9 g (model) | not public | $0.01 | n/a | n/a | not public |
| · · Circular spline (`circular-spline`) (inferred)[^1] | 1 | 91 g (model) | not public | $0.05 | n/a | n/a | not public |
| · · Flexspline (`flexspline`) (inferred)[^1] | 1 | 35 g (model) | not public | $0.02 | n/a | n/a | not public |
| · Frameless motor (`frameless-motor`)[^1] | 1 | 466 g (model) | $278-278[^2] (model, 2026) | $4.3 | 65x | n/a | Leadshine, margin 39%[^4] (typical maker, stands in) |
| · · Stator (`stator`) (inferred)[^1] | 1 | 374 g (model) | not public | $1.88 | n/a | n/a | not public |
| · · · Lamination stack (`stator-core`) (inferred)[^1] | 1 | 254 g (model) | not public | $0.15 | n/a | n/a | not public |
| · · · Copper windings (`stator-winding`) (inferred)[^1] | 1 | 121 g (model) | not public | $1.73 | n/a | n/a | Jiangxi Copper (typical maker, stands in) |
| · · Frameless rotor (`rotor`) (inferred)[^1] | 1 | 92 g (model) | not public | $2.42 | n/a | n/a | not public |
| · · · NdFeB magnets (`rotor-magnet`) (inferred)[^1] | 1 | 53 g (model) | not public | $2.4 | n/a | n/a | Shin-Etsu Chemical (typical maker, stands in) |
| · · · Rotor hub (`rotor-hub`) (inferred)[^1] | 1 | 39 g (model) | not public | $0.02 | n/a | n/a | not public |
| · Bearing, encoder, brake, driver (`other-parts`)[^1] | 1 | 334 g (model) | $422-422[^2] (model, 2026) | $0.87 | 486x | n/a | not public |
| · · Crossed-roller bearing (`crossed-roller-bearing`) (inferred)[^1] | 1 | 69 g (model) | not public | $0.05 | n/a | n/a | Nippon Thompson (IKO), margin 32%[^5] (model, 2026-03) (typical maker, stands in) |
| · · Motor encoder (`motor-encoder`) (inferred)[^1] | 1 | 0.53 g (model) | not public | $0.02 | n/a | n/a | not public |
| · · · Angle sensor chip (`motor-encoder-chip`) (inferred)[^1] | 1 | 0.00 g (model) | $7.44-8.83[^6] (model, 2025) | $0.00 | 867,667x | 867,667x | not public |
| · · · Diametric magnet (`encoder-magnet`) (inferred)[^1] | 1 | 0.53 g (model) | not public | $0.02 | n/a | n/a | not public |
| · · Friction brake (`brake`) (inferred)[^1] | 1 | 42 g (model) | not public | $0.16 | n/a | n/a | not public |
| · · · Armature plate (`brake-armature`) (inferred)[^1] | 1 | 15 g (model) | not public | $0.01 | n/a | n/a | not public |
| · · · Field body (`brake-field`) (inferred)[^1] | 1 | 17 g (model) | not public | $0.01 | n/a | n/a | not public |
| · · · Brake coil (`brake-coil`) (inferred)[^1] | 1 | 10 g (model) | not public | $0.14 | n/a | n/a | not public |
| · · · Pressure spring (`brake-springs`) (inferred)[^1] | 6 | 0.35 g (model) | not public | $0.00 | n/a | n/a | not public |
| · · Servo driver board (`driver-board`) (inferred)[^1] | 1 | 2 g (model) | not public | $0.03 | n/a | n/a | not public |
| · · · Bare circuit board (`bare-board`) (inferred)[^1] | 1 | 2 g (model) | not public | $0.03 | n/a | n/a | not public |
| · · · Motor-control MCU (`mcu`) (inferred)[^1] | 1 | 0.01 g (model) | $0.8-1.1[^7] (model, 2025) | $0.00 | 36,501x | 36,501x | not public |
| · · · Gate driver (`gate-driver`) (inferred)[^1] | 1 | 0.00 g (model) | $0.25-0.36[^8] (model, 2025) | $0.00 | 57,490x | 57,490x | not public |
| · · · Dual power MOSFET (`power-mosfets`) (inferred)[^1] | 3 | 0.01 g (model) | $0.25-0.31[^9] (model, 2025) | $0.00 | 26,616x | 26,616x | not public |
| · · · Bus transceiver (`bus-transceiver`) (inferred)[^1] | 1 | 0.00 g (model) | not public | $0.00 | n/a | n/a | not public |
| · · Housing (`housing`) (inferred)[^1] | 1 | 221 g (model) | not public | $0.61 | n/a | n/a | not public |
| · · · Housing tube (`housing-shell`) (inferred)[^1] | 1 | 146 g (model) | not public | $0.47 | n/a | n/a | not public |
| · · · Output flange (`output-flange`) (inferred)[^1] | 1 | 36 g (model) | not public | $0.12 | n/a | n/a | not public |
| · · · Hollow shaft (`hollow-shaft`) (inferred)[^1] | 1 | 32 g (model) | not public | $0.02 | n/a | n/a | not public |
| · · · Screw (`fasteners`) (inferred)[^1] | 12 | 7 g (model) | not public | $0.00 | n/a | n/a | not public |

Modeled parts weigh 968 g in all.

## Used in

Robots and catalog actuators that use this actuator or one of its design, from the /humanoids fleet and the robots and actuator catalogs.

- [ENCOS EC-A5013-H17-100](https://actuatorlist.com/actuators/encos-ec-a5013-h17-100): same design. A catalog actuator of the same design.
- [Harmonic Drive LLC FHA-14C-100 (FHA-C Mini)](https://actuatorlist.com/actuators/harmonic-drive-fha-14c-100): same design. A catalog actuator of the same design.
- [Tesla Optimus Gen 2](https://actuatorlist.com/humanoids?robot=tesla-optimus): same design, 14 joints (no photo on the site). 14 joints of the same design on /humanoids.
- [Menlo Research Asimov 1](https://actuatorlist.com/humanoids?robot=menlo-asimov-1): same design, 8 joints. 8 joints of the same design on /humanoids.

## Cost stacks

Each priced node's unit cost in four bands that add up to it: the raw material inside, what the tiers below added on top of their raw material, this step's labour, energy, machines and overhead (with any margin we cannot attribute), and its maker's gross profit at the company's latest margin. The Sankey on the page draws the last two as flows into each step.

| Priced node | Unit cost | Raw material | Added by tiers below | Labour, energy, overhead | Maker's gross profit |
| --- | --- | --- | --- | --- | --- |
| Strain-wave joint (`harmonic-frameless`) | $1.44k | $5.27 | $1.44k | $0.00 | $0.00 |
| Strain-wave gear (`strain-wave-gear`) | $741 | $0.10 | $0.00 | $515.6 | $225.3 |
| Frameless motor (`frameless-motor`) | $278 | $4.3 | $0.00 | $165.3 | $108.4 |
| Bearing, encoder, brake, driver (`other-parts`) | $422 | $0.87 | $10.1 | $411.1 | $0.00 |
| Angle sensor chip (`motor-encoder-chip`) | $8.15 | $0.00 | $0.00 | $8.15 | $0.00 |
| Motor-control MCU (`mcu`) | $0.80 | $0.00 | $0.00 | $0.80 | $0.00 |
| Gate driver (`gate-driver`) | $0.36 | $0.00 | $0.00 | $0.36 | $0.00 |
| Dual power MOSFET (`power-mosfets`) | $0.25 | $0.00 | $0.00 | $0.25 | $0.00 |

## How the parts are made

The usual route from raw material to each part, in our words; magnets link to the steps on [/manufacturing](https://actuatorlist.com/manufacturing.md).

- Strain-wave joint (`harmonic-frameless`): Mount stator → Fit gear → Fit bearing → Fit brake, board → Calibrate encoder → Test
- Strain-wave gear (`strain-wave-gear`): Pair flexspline, spline → Assemble → Run in → Measure backlash
- Elliptical cam (`wave-cam`): Cut bar → Turn → Grind ellipse → Harden
- Flexible bearing (`flex-bearing`): Turn thin rings → Harden → Grind races → Fit balls
- Circular spline (`circular-spline`): Forge ring → Turn → Shape teeth → Nitride
- Flexspline (`flexspline`): Forge cup → Turn wall thin → Hob teeth → Heat-treat → Shot peen
- Lamination stack (`stator-core`): Slit coil → Stamp sheets → Stack and bond
- Copper windings (`stator-winding`): Draw wire → Enamel → Wind coils → Impregnate
- Rotor hub (`rotor-hub`): Cut bar → CNC turn → Heat-treat
- Crossed-roller bearing (`crossed-roller-bearing`): Forge rings → Turn → Harden → Grind V-races → Fit crossed rollers
- Angle sensor chip (`motor-encoder-chip`): Wafer fab → Dice → Package → Test
- Armature plate (`brake-armature`): Stamp → Grind flat
- Field body (`brake-field`): Cut bar → CNC turn → Heat-treat
- Brake coil (`brake-coil`): Draw wire → Enamel → Wind coils → Impregnate
- Pressure spring (`brake-springs`): Draw wire → Coil → Stress-relieve
- Bare circuit board (`bare-board`): Laminate → Drill → Plate → Etch
- Motor-control MCU (`mcu`): Wafer fab → Dice → Package → Test
- Gate driver (`gate-driver`): Wafer fab → Dice → Package → Test
- Dual power MOSFET (`power-mosfets`): Wafer fab → Dice → Package → Test
- Bus transceiver (`bus-transceiver`): Wafer fab → Dice → Package → Test
- Housing tube (`housing-shell`): Die-cast → CNC machine → Anodise
- Output flange (`output-flange`): CNC machine → Anodise
- Hollow shaft (`hollow-shaft`): Cut bar → CNC turn → Heat-treat
- Screw (`fasteners`): Cold-head → Roll thread → Heat-treat → Plate

## Raw materials

| Material | In one actuator | Price per kg | Cost |
| --- | --- | --- | --- |
| NdPr alloy | 16 g (model) | 133.4 USD/kg[^10] | $2.14 |
| Copper | 133 g (model) | 14.3 USD/kg[^11] | $1.9 |
| Aluminium | 182 g (model) | 3.25 USD/kg[^12] | $0.59 |
| Dy metal | 1 g (model) | 233.6 USD/kg[^13] | $0.26 |
| Electrical steel | 254 g (model) | ~0.6-0.62 USD/kg[^14] (estimate, 2026-06) | $0.15 |
| Steel | 236 g (model) | ~0.51-0.52 USD/kg[^15] (estimate, 2026-06) | $0.12 |
| Bearing steel | 147 g (model) | ~0.67-0.69 USD/kg[^16] (estimate, 2025) | $0.10 |
| Silicon | 0.02 g (model) | 3.13 USD/kg[^17] | $0.00 |

## Margin capture

Each tier's gross profit is what it sells into this actuator times its latest company gross margin (a group figure, not a product line). The rest of the price pays for labour, energy, machines and margins of makers we cannot name.

| Who | Tier | Sells in this actuator | Gross margin | Gross profit | Share of price |
| --- | --- | --- | --- | --- | --- |
| Harmonic Drive Systems (typical maker) | `strain-wave-gear` | $741 | 30%[^3] (model, 2026-03) | $225.3 | 15.6% |
| Leadshine (typical maker) | `frameless-motor` | $278 | 39%[^4] | $108.4 | 7.5% |
| China Northern Rare Earth (typical maker) | `rotor-magnet-ndpr` | $2.12 | ~12%[^18] (estimate, 2025) | $0.25 | 0% |
| China Northern Rare Earth (typical maker) | `encoder-magnet-ndpr` | $0.02 | ~12%[^18] (estimate, 2025) | $0 | 0% |
| Raw material (miners' and mills' margins inside) |  | $5.27 |  |  | 0.37% |
| Everything else: makers' costs and margins we cannot attribute |  | $1.1k |  |  | 76.5% |

## Method

- Costs: the price is split by a published share of each part in an actuator of this type, so every part cost is a model.
- Bought-in chips and bearings: distributor or marketplace listings for the same or a comparable part, never the actuator maker's contract price.
- Raw material: grams from our part geometry times cited densities, priced with /metals for rare earths and cited commodity readings for the rest.
- Magnets: an SH-grade recipe with grain-boundary diffused Dy, from /metals.
- See [/manufacturing](https://actuatorlist.com/manufacturing.md) for how the magnet is made, and [/bom](https://actuatorlist.com/bom.md) for all three cases.

## Sources

[^1]: RCDrone, "ZeroErr eRob 80 T integrated joint (shop listing)". https://rcdrone.top/products/zeroerr-erob-80-t-motor (not opened).
[^2]: HONPINE (RoboticsTomorrow), "Linear actuators vs rotary actuators: the core choice for humanoid robot joints". https://www.roboticstomorrow.com/content.php?post=25703 (not opened).
[^3]: Envalith, "Harmonic Drive Systems (6324): financial summary". https://envalith.com/en/companies/6324 (accessed 2026-11-03).
[^4]: Leadshine, "Leadshine 2025 annual report and 2026 Q1 report: revenue hits new highs". https://en.leadshine.com/newsEvent/details/Leadshine%202025%20Annual%20Report%20&%202026%20Q1%20Report:%20Accelerating%20the%20Growth%20Flywheel,%20Revenue%20Hits%20New%20Highs.html (not opened).
[^5]: Stock Analysis, "Nippon Thompson (TYO:6480) income statement: financial summary". https://stockanalysis.com/quote/tyo/6480/financials/income-statement/ (accessed 2026-11-03).
[^6]: FindChips, "AS5045-ASST price and stock across distributors". https://www.findchips.com/search/AS5045-ASST (not opened).
[^7]: LCSC, "STM32F103C8T6 (C8734) price tiers". https://www.lcsc.com/product-image/C8734.html (not opened).
[^8]: LCSC, "Fortior Tech FD6288Q three-phase gate driver (C328453) price tiers". https://lcsc.com/product-detail/Gate-Drivers_Fortior-Tech-FD6288Q_C328453.html (not opened).
[^9]: LCSC, "Winsok WSD4066DN dual N-channel 40 V MOSFET (C377861)". https://www.lcsc.com/datasheet/lcsc_datasheet_1912111437_Winsok-Semicon-WSD4066DN_C377861.pdf (not opened).
[^10]: Rare Earth Mining (SMM data), "Neodymium price today: NdPr spot and industrial benchmark". https://rare-earth-mining.com/neodymium-price/ (accessed 2026-10-26).
[^11]: Cbonds (World Bank Pink Sheet), "Copper (World Bank) monthly price, USD/t". https://cbonds.com/indexes/154158/ (not opened).
[^12]: Cbonds (World Bank Pink Sheet), "Aluminum (World Bank) monthly price, USD/t". https://cbonds.com/indexes/154154/ (not opened).
[^13]: Rare Earth Mining (SMM data), "Dysprosium price today: spot rate and market outlook". https://rare-earth-mining.com/dysprosium-price/ (accessed 2026-10-26).
[^14]: SMM, "SMM weekly summary: non-oriented silicon steel market". https://news.metal.com/es/newscontent/103952808-SMM-Weekly-Summary-Leading-steel-mills-did-not-continue-to-push-up-prices-and-the-non-oriented-silicon-steel-market-may- (not opened).
[^15]: SMM, "Shagang June 2026 hot-rolled steel price adjustment". https://news.metal.com/id/newscontent/103932178-Informasi-Penyesuaian-Harga-Baja-Canai-Panas-Shagang-Juni-2026 (not opened).
[^16]: China Bearing Industry Association (CBCC), "Bearing steel market report: GCr15 absolute price index". https://bearing.com.cn/dev/read_news.php?id=73305 (not opened).
[^17]: USGS, "Mineral Industry Surveys: silicon, December 2025". https://d9-wret.s3.us-west-2.amazonaws.com/assets/palladium/production/s3fs-public/media/files/mis-202512-simet.pdf (not opened).
[^18]: StockAnalysis, "China Northern Rare Earth (SHA:600111) income statement". https://stockanalysis.com/quote/sha/600111/financials/income-statement/ (not opened).