China's Planetary Roller Screw Suppliers: The Linear Muscles of Humanoid Robots

A humanoid robot doesn't only rotate — it pushes. Every squat, stride and finger pinch comes from linear motion, and in the flagship humanoids of this generation that linear motion is generated by a planetary roller screw: a screw whose threaded rollers share the load, turning motor spin into thousands of newtons of linear thrust. Tesla's Optimus packs 14 of them across its arms and legs; analysts estimate roller screws are a humanoid's single most expensive mechanical part, roughly 19% of mechanical cost per unit.

Why roller screws are the humanoid standard

A planetary roller screw is a ball screw's stronger cousin. Where a ball screw transmits load through point contact on a few balls, a roller screw spreads it through line contact across multiple threaded rollers — giving roughly 3-10x the load capacity of a comparable ball screw, better stiffness, longer life and superior impact resistance. A standard 20mm-diameter roller screw can take about 50,000 N of axial load where a same-size ball screw tops out near 5,000 N. That is exactly the duty a humanoid's hip, knee and shoulder demand: high force, high cycle life, and the self-locking ability to hold a pose with the motor off — saving battery while the robot stands.

The West's monopoly — and China's ~20%

High-end planetary roller screws remain a Western oligopoly. European names such as SKF, Rollvis and GSA (plus Ewellix and Tolomatic in actuators) hold roughly 80% of global premium share, with China's domestic makers collectively under 20%. The barrier is manufacturing, not design: roller screws need ultra-precision thread grinding, specialized machines and years of process know-how. Chinese suppliers crossed into mass production only around 2024-2025 — and they are scaling fast on the back of the humanoid boom.

The Chinese lineup

Nanjing Gongyi — the domestic leader

State-backed Nanjing Gongyi Equipment Manufacturing (南京工艺装备制造) is China's largest maker of rolling-function components and the clear #1 in domestic planetary roller screws, with roughly 8-14% of the China market depending on the report. It already mass-produces the full Φ16-32mm series and has built the country's first dedicated roller screw grinding line, compressing lead time to about 14.2 days versus an industry average near 28.6 days. That combination of precision, range and speed makes it the default reference point for Chinese humanoid OEMs today.

Wuzhou Xinchun — the cost-killer

Bearing specialist Wuzhou Xinchun (五洲新春, 603667) holds roughly 10% of China's planetary roller screw market and has become the benchmark for cost-down. In 2025 it shipped about 87,000 reverse planetary roller screws at an average price of ~1,360 yuan, down 39% year over year — the clearest sign that roller screws are heading down the same cost curve that made harmonic drives and frameless motors Chinese commodities. Its tie-up with Xinjian Transmission (新剑传动) gives it a door into the global humanoid supply chain.

The challengers

Hengli Hydraulic (恒立液压, 601100) is the most watched crossover: the hydraulics and precision-machining champion is applying decades of high-precision manufacturing to screws, with ball screws already in small-batch delivery and planetary roller screws in trial production — and it has sent samples to Tesla and others. Tuopu (拓普集团) takes the integration route as Tesla Optimus' exclusive Tier-1 for linear/rotary executor modules, with 300,000-unit annual capacity in Ningbo and a Mexico plant online. Beste (贝斯特) reached C0-grade ball screws via its Yuhua subsidiary plus Germany's KISSLING, and Bote Precision (博特精工) holds ~8% share. Auto-parts players like Bete Technology (北特科技) round out a deep bench.

Why China is breaking in

Three structural advantages explain the surge. First, machine-tool self-sufficiency: China now builds its own thread-grinding machines (Qinchuan Machine Tool produces them in-house), removing the historical dependency on imported precision grinders. Second, reverse roller screw economics: the inverted design simplifies manufacturing and cuts cost dramatically — Wuzhou Xinchun's 39% price drop in a single year shows how fast that curve moves. Third, integrated executor modules: Tuopu and Sanhua sell motor + reducer + screw as one tuned assembly, exactly what humanoid OEMs want to avoid stitching five vendors together.

What to watch

• Miniature screws for dexterous hands — micro roller screws under 8mm diameter (Shuanglin's offering) target the finger joints of the next generation.
• Integrated executor modules — Tuopu-style "screw + motor + reducer in one" packages are becoming the default procurement unit.
• Precision grades climbing — Chinese makers are moving from C3-C5 into C0/C1 territory, the last frontier of the Western moat.

Frequently asked questions

Which Chinese company leads the planetary roller screw market?

Nanjing Gongyi (南京工艺) is China's #1 planetary roller screw maker with roughly 8-14% domestic share, full Φ16-32mm series mass production, and the country's first dedicated roller screw grinding line.

Why are planetary roller screws better than ball screws for humanoids?

Line contact spreads load across multiple rollers, giving planetary roller screws roughly 3-10x the load capacity of ball screws and far better impact resistance — ideal for the high-force linear joints of a humanoid's legs and arms.

How many roller screws does a humanoid robot need?

Tesla's Optimus packs 14 reverse planetary roller screws across its arms and legs. Roller screws are typically a humanoid's most expensive mechanical part — around 19% of mechanical cost per unit.

Is China catching up with the West in roller screws?

Western makers such as SKF, Rollvis and GSA still hold roughly 80% of global high-end share, but Nanjing Gongyi, Wuzhou Xinchun, Hengli Hydraulic and Tuopu are now in mass production or Tesla validation.