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Humanoid Robot Bearings: Technical Architecture, Supply Chain Landscape, and Industry Frontier Analysis

From 2025 to 2026, the humanoid robot industry has entered a phase of intensive commercialization. Tesla's Optimus is performing material handling at Gigafactories, UBTech's Walker S is undergoing assembly line training at NIO, and Boston Dynamics' Atlas has released industrial-grade operation demonstrations. According to a Goldman Sachs report from February 2026, global shipments of humanoid robots are expected to surge from under a thousand units in 2025 to a million units by 2030.

Joint actuators are the physical carriers of a robot's motion capability. Within each rotational joint, precision bearings endure complex, multi-directional loads and are the core components ensuring motion accuracy and system reliability. A single humanoid robot typically has 30-40 rotational joints; adding the micro-bearings inside dexterous hands, the total number of bearings per robot can exceed 100. As algorithmic competition becomes increasingly homogeneous, hardware costs and reliability emerge as the bottlenecks to mass production, making the role of bearings in this industrial chain worthy of in-depth examination.

I. Technical Architecture: Three Types of Bearings Support One Joint

While industrial motor bearings strive for high speeds and long life, the operational logic for robot joint bearings is fundamentally different: low speeds (10-50 rpm), high torque, and frequent starts, stops, and reversals. Rather than rotating uniformly, they oscillate periodically under alternating stress, demanding higher material uniformity and machining precision. Furthermore, joint space is extremely compact—the radial cross-section for the bearing in Tesla Optimus's shoulder, for instance, is only a few millimeters, yet it must withstand an overturning moment exceeding 100 Nm. Balancing slimness with rigidity is the core challenge.

Currently, humanoid robot joints primarily use three types of precision bearings:

Crossed Roller Bearings are used in shoulders and hips. Cylindrical rollers are arranged with their axes at 90° in V-shaped raceways. A single bearing can simultaneously bear radial, axial, and overturning moments, achieving P4 accuracy. The manufacturing challenge lies in controlling V-shaped raceway angle consistency and roller grouping precision to sub-micron levels.

Thin-Section Angular Contact Ball Bearings are used in elbows and wrists. They feature an extremely thin cross-section and often employ a four-point contact design to achieve bi-directional load capacity within a limited space. Thin rings are highly prone to deformation during quenching, making heat treatment control and precision grinding core barriers.

Flexible Bearings are built inside harmonic drives. The harmonic drive's wave generator forces the flexspline to deform into an ellipse, causing the flexible bearing to flex periodically. The bearing's inner and outer rings must be flexible, and the raceway must provide uniform load support even in its elliptical shape. Fatigue life is the key performance indicator. Harmonic Drive Systems' (Japan) matched flexible bearings can achieve over 10,000 hours under rated conditions.

Dexterous hands represent the ultimate challenge for micro-bearings. The Tesla Optimus hand contains dozens of micro-deep groove ball bearings with inner diameters of 2-4mm. Their starting torque must be controlled to the millinewton-meter level, and they must use solid lubrication—oil or grease leakage would be a fatal contaminant for sensors. Nachi-Fujikoshi (Japan) introduced a 3mm specialty bearing in 2025 with a starting torque of just 0.02 mNm and roundness of 0.1μm, setting the current industry benchmark.

II. Supply Chain Landscape: Different Paths for Japan, Europe, and China

Japan: First-Mover Advantage, But Supply Rigidity

Japanese companies are pioneers in precision bearings for humanoid robots. Their advantage is built upon the long-established industrial ecosystem for harmonic drives—Harmonic Drive Systems for reducers, NSK for bearings, and Yaskawa for motors form a tightly integrated supply chain.

NSK announced in February 2026 that it had developed a third-generation joint bearing module for a "leading North American humanoid robot company," integrating a torque sensor and temperature monitoring. This represents a typical case of smart bearings evolving from industrial equipment condition monitoring to robotic applications; bearings are shifting from passive "rotating parts" to "sensing elements."

JTEKT established a robotics division in 2025, leveraging its precision manufacturing capabilities from the Toyota automotive supply chain. Its primary focus is on crossed roller bearings for harmonic drives, with a production capacity target of 500,000 units per year by 2027.

NACHI has decades of experience in micro-precision bearings and launched a series of dexterous-hand bearings in 2025. It is one of the few companies in this niche market with mass production capabilities. Its 3mm inner diameter product sets the benchmark for starting torque and roundness.

Japanese companies' advantages are evident across the entire value chain, including materials, heat treatment, and ultra-precision machining. Another characteristic of their supply system is rigidity—standard lead times are typically 6-8 months, with low acceptance of small-batch customized orders. As the number of humanoid robot startups increases, the suitability of this supply model is being tested.

Europe: Upward Integration, Strategic Shift

Major European bearing players are showing a clear trend of upward integration in their robotics strategies.

SKF explicitly stated in its Q1 2026 financial report that it will "increase capital expenditure on precision bearings for robotics." At the 2025 Hannover Messe, SKF showcased a series of hybrid ceramic bearings for robot joints—steel rings with silicon nitride ceramic balls, reducing friction torque by 30% and increasing speed capability by 50%. Concurrently, SKF is integrating its oil condition monitoring systems with bearing sensing technology to explore full lifecycle condition monitoring for robot joints.

SCHAEFFLER acquired a German robot joint module company in 2025, completing the vertical integration of "bearings + reducer + motor." The CEO stated at the 2026 annual general meeting: "Humanoid robots represent the largest incremental market for precision bearings over the next decade."

European companies' strategic focus is shifting from purely supplying bearings to providing overall joint module solutions. This trend implies at an industry level that the technical value of bearings is being re-evaluated—they are no longer just independent standard components but an integral part of system performance.

China: Closing the Gap, From "Generation Gap" to "Multiples Gap"

The progress in domestic precision bearings for robotics can be summarized as "noteworthy speed, but clear disparities," based on public information from 2025-2026.

C & U Group, a leading Chinese industrial bearing manufacturer, established a dedicated robotics bearing division in 2025. It has completed the serialization development of needle roller bearings for RV reducers and flexible bearings for harmonic reducers. According to its 2026 exhibition materials, the fatigue life of its flexible bearings has reached 8 million cycles, with a target of 15 million cycles.

CW Group has a scale advantage in micro-deep groove ball bearings. It has supplied prototype dexterous-hand bearings to several domestic humanoid robot companies and has entered small-batch deliveries.

WANDA specializes in thin-section bearings. It received approval for its IPO on the Beijing Stock Exchange in 2026, with the funds targeted for expanding precision bearing capacity for robotics. Thin-section bearings are one of the product categories where domestic substitution is relatively low, making their industrial progress noteworthy.

Zhejiang XCC Group Co.,Ltd. has achieved mass production of flexible bearings for harmonic reducers and announced in a 2025 public filing that it signed a long-term supply agreement with a leading domestic robotics company.

Observing the development timeline: In 2023, the fatigue life of domestically produced flexible bearings for harmonic reducers was generally below 3 million cycles. By 2026, leading players are approaching 8 million cycles. The gap is narrowing from a "generational difference" to a "multiples difference." Drivers of this change include improved material cleanliness, enhanced heat treatment consistency, and mature superfinishing processes.

Structural Changes

The traditional robot supply chain was highly vertical, with OEMs rarely purchasing bearings separately. However, the influx of humanoid robot startups is changing this landscape—they cannot establish direct supply relationships with companies like NSK or tolerate 6-month lead times, thus turning to independent purchasing. The supply system for robot bearings is transitioning from "closed supporting" to "open procurement," opening doors to the global supply chain for companies with precision manufacturing capabilities.

III. Materials and Manufacturing: Three Key Technologies Defining Performance Boundaries

Steel cleanliness is the foundation of fatigue life. When flexible bearings are subjected to alternating stress, non-metallic inclusions—especially DS-type brittle inclusions—are the primary source of fatigue spalling. The seemingly small difference in oxygen content from 4 ppm to 5 ppm determines whether a domestic flexible bearing's life jumps from 3 million to 8 million cycles. The key to further breakthroughs lies in controlling consistency across the entire process, from steelmaking to assembly.

Ceramic materials are entering practical application. Silicon nitride ceramic balls have only 40% of the density of steel, lower centrifugal force, are electrically insulating, and can run dry. SKF and NSK have both launched hybrid ceramic bearings (steel rings + ceramic balls), achieving a 30% reduction in friction torque. Domestic companies like Sinoma Advanced Materials can supply G5-grade ceramic balls, on par with international levels. All-ceramic bearings, due to processing difficulty and cost, are currently mainly used in specialized scenarios like semiconductor cleanroom robots.

Solid lubrication addresses the challenge of lifetime maintenance-free. Dexterous hands and medical collaborative arms strictly prohibit grease leakage, forcing a shift from liquid to solid lubrication films. Diamond-like carbon (DLC) coatings, with a friction coefficient as low as 0.05 and wear resistance exceeding 10 million cycles, are already mass-produced by Japanese companies. Polymer transfer films (cage material containing PTFE, which transfers a minute amount to the raceway during operation) and aerospace-grade tungsten disulfide sputtered films (no failure after 5 million cycles in vacuum) are also advancing towards engineering application. The core value of solid lubrication is: no need to disassemble the joint for regreasing throughout its entire lifecycle.

IV. Standards and Verification: From "Can Do" to "Can Prove Can Do"

As of 2026, there is no dedicated international standard for humanoid robot bearings. ISO/TC 4 initiated a work item proposal for "precision bearings for service robots" in 2025, with an official standard potentially released around 2029. Currently, the industry refers to general standards such as ISO 10285, JIS B 1520, and ASTM F2215.

In China, the National Technical Committee on Rolling Bearings of Standardization Administration (SAC/TC 98) approved a national standard revision plan for "Bearings for Industrial Robot Precision Reducers" in 2025. The draft adds test methods for dynamic fatigue life of flexible bearings and stiffness test specifications for crossed roller bearings. This signifies that robot bearings are transitioning from exploratory products to standardized categories.

Regarding verification capabilities, robot bearings must be tested on combined load simulation test rigs that simultaneously apply radial, axial, and overturning moments. Currently, only a few institutions in China, like ZYS, possess this capability. As the standard system is established, independent, reliable third-party testing data will become a mandatory requirement for entering mainstream supply chains.

V. Conclusion

The humanoid robot industry is transitioning from the engineering verification phase to a commercial inflection point. As the window for algorithmic differentiation narrows, hardware performance—especially joint bearings—will once again become a competitive focal point.

Japanese companies possess the most complete material, processing, and inspection chains, but their supply system's rigidity leaves room for the diverse needs of humanoid robots. European giants are integrating upwards, initiating structural adjustments in the pure bearing supply segment. Chinese companies have crossed the threshold from "unable to catch up" to "seeing the leader's taillights." The next challenge is: can they control life dispersion to Japanese levels during mass production?

From materials to manufacturing, from standards to verification, progress in every link is redefining the value a single bearing can carry.

This information is sourced from NSK technical reports (2025), CITIC Steel public filings (March 2026), SKF 2025-2026 financial reports and exhibition materials, SAC/TC 98 standard plans (2025-2026), publicly available literature from ZYS, and ESA space robotics test reports (2025), among other public materials.*