Slim Type Crossed Roller Bearings

Thin‑Wall Crossed Roller Bearings – The Core Choice for Humanoid Robot Joint Rotary Actuators

The secret to a robot’s agility lies in a 5‑mm joint

At the 2026 CCTV Spring Festival Gala, Unitree’s humanoid robot troupe performed WuBOT alongside martial arts students – a breathtaking show of high‑dynamic group choreography, including rapid sprints, formation changes, somersaults, nunchaku duels, and even Drunken Fist moves. Months earlier, at the Beijing E‑Town Half Marathon, the “Lightning” humanoid robot crossed the finish line in 50 minutes 26 seconds net, beating the men’s world record for human half‑marathon runners.

Behind these astonishing feats lies a tiny but critical component: the thin‑wall crossed roller bearing – the “soul of the joint” in humanoid robot rotary actuators.

Why humanoid robots cannot do without thin‑wall crossed roller bearings

The joint actuators of humanoid robots – whether harmonic‑drive or planetary‑type – place very different demands on bearings compared to industrial robots: tighter space, multi‑directional loads, frequent reversing motions, and continuous impact. As the core rotating component of every joint, the crossed roller bearing directly determines how smoothly the robot moves, how precisely it positions, and how reliably it operates over its lifetime.

In humanoid robots, crossed roller bearings are almost always used as the output bearing of the rotary actuator. Their cylindrical rollers are arranged at 90° crosswise (X‑pattern) via spacers in V‑shaped raceways, enabling them to simultaneously support radial loads, bidirectional axial loads, and tilting moments. This unique structure delivers a combination of advantages that conventional bearings simply cannot match.

Four core advantages – redefining bearing standards for humanoid robotics

1. Ultra‑compact design – frees up valuable space

Humanoid joints are extremely space‑constrained, demanding ever‑thinner bearing sections. Our thin‑wall crossed roller bearings feature ultra‑thin cross‑sections (wall thickness ≤ 5 mm), allowing efficient integration within minimal installation envelopes while keeping the robot lightweight and compact.

Conventional solutions often require two thin‑section bearings to do the same job – doubling space usage and cost. The crossed roller bearing integrates the function of two bearings into a single, compact platform through its X‑arranged rollers, fundamentally resolving the space‑vs‑cost dilemma.

2. Extreme rigidity – handles complex load conditions

The shoulder, hip, knee, and other core motion joints must withstand radial, axial, and tilting loads simultaneously – and these loads fluctuate with every dynamic movement.

Thin‑wall crossed roller bearings offer three to four times the rigidity of conventional single‑row bearings, providing stable rotational support and high load‑carrying capacity for the robot’s most demanding joints. Whether it’s high‑frequency flexion during running or alternating loads during heavy manipulation, our bearings rise to the challenge.

3. Ultra‑high precision – ensures silky‑smooth motion

Positioning accuracy is the foundation for fine manipulation. Our thin‑wall crossed roller bearings achieve P4 and P2 precision grades – among the highest available – with rotational accuracy on par with international leaders. By applying a light preload or minimising clearance, we further optimise accuracy and eliminate backlash, ensuring perfectly smooth motion.

4. Lifetime maintenance‑free – lowers total cost of ownership

Humanoid robots must maintain stable performance over years of operation, with minimal downtime for service. Our thin‑wall crossed roller bearings are engineered to overcome the life‑cycle challenges of high‑frequency motion and are truly maintenance‑free for the entire service life. The low‑friction design between rollers ensures stable torque, so the robot never needs frequent lubrication or replacement.

Technical deep‑dive: how the cross‑arrangement delivers “strength with flexibility”

The key technology lies in the crosswise (90°) arrangement of cylindrical rollers. Rollers are placed in V‑shaped raceways on the inner and outer rings, separated by spacers, so that a single bearing simultaneously resists loads from multiple directions.

This design achieves three major breakthroughs:

• Integration – replaces the function of two separate bearings, simplifying design and reducing axial length

• High rigidity – line contact between rollers and raceways provides a much larger contact area, resulting in far higher rigidity than point‑contact ball bearings of similar size

• Low friction – spacers between rollers eliminate roller‑to‑roller friction, ensuring stable rotational torque

Typical application scenarios

Thin‑wall crossed roller bearings are widely used in all rotary joints of humanoid robots:

According to market forecasts, the global humanoid‑robot crossed‑roller‑bearing market is expected to reach USD 213 million by 2032, with a CAGR of 45.0%. Leg joints are projected to account for approximately 40‑45% of robot bearing revenue, while wrist joints will represent about one‑quarter. This explosive growth presents an unprecedented opportunity for thin‑wall crossed roller bearings.

Built for the next generation of humanoid robots

Humanoid robots are moving from labs to the real world – from high‑dynamic stage performances to long‑distance road races. These real‑world tests prove one thing: the quality of the joint bearing directly sets the upper limit of the robot’s motion capability.

Thin‑wall crossed roller bearings – with their extreme compactness for design freedom, ultra‑high rigidity for complex loads, precision manufacturing for silky motion, and lifetime maintenance‑free operation for reduced costs – are the essential choice for humanoid rotary actuators and a critical technological pathway to the next generation of high‑performance humanoid robots.

Contact us today – customised solutions for your robot joints

We offer a full range of thin‑wall crossed roller bearing solutions for all robot joint applications, from industrial arms to advanced humanoids. Our products cover precision grades P5 to P2, and we support custom designs – including flanges, bolt‑hole patterns, and mounting configurations tailored to your specific actuator.

Make every joint precise and powerful – let humanoid robots truly move with agility and grace.