Harmonic (strain-wave) reducers
Compact, zero-backlash, high-ratio gearboxes for precise joints such as arms and wrists.
Data updated
Why it matters
Strain-wave gears use a flexing spline to get ratios of 50-160:1 in a flat, light package with near-zero backlash, which suits shoulders, elbows and wrists. An Optimus-class humanoid uses around 14 harmonic reducers.
Why it is a bottleneck. Precision machining and fatigue life are hard to replicate. Harmonic Drive Systems long dominated, but Chinese makers such as Leaderdrive sell at a reported 40-60% of Japanese prices and are adding capacity of more than 1M units a year, which is driving prices down.
Cost. Leaderdrive sold 425,158 harmonic reducers in 2025 (+72% YoY) and targets 1.44M units of annual capacity by end-2026.
Suppliers 4
- HIWIN TechnologiesBall screws, harmonic reducers, crossed-roller bearings, joint modules; planetary roller screws (planned)
- Harmonic Drive SystemsStrain-wave gears; integrated actuator units
- Leaderdrive (Suzhou Green Harmonic)Harmonic reducers; integrated joint modules (in development)
- NabtescoRV and RV-N cycloidal gearboxes
Sources for this category
- Who builds the joints? The humanoid actuator supplier landscape in 2026 (humanoid.guide) (Sep 16, 2026)
- Leader Harmonic deep dive (404K Research) (Jul 7, 2026)
- Harmonic Drive Systems consolidated financial results, FY ended March 2026 (May 18, 2026)
- Harmonic Drive Systems FY2027 Q1 earnings call (BigGo Finance) (Aug 7, 2026)
- The 'shovel seller' behind Unitree and Agibot: upcoming IPO (36Kr) (Sep 4, 2026)