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For Inner Ring Rotation – Outer Ring Rotation

THK Cross Roller Bearings for Inner Ring Rotation represent a specialized class of linear motion components engineered for applications demanding exceptional rotational accuracy, high rigidity, and compact design. These bearings are fundamentally characterized by their unique structural arrangement, where cylindrical rollers are alternately crossed at right angles between the inner and outer rings. This configuration allows the bearing to simultaneously support complex load combinations—including radial loads, axial loads, and moment loads—all within a single, highly integrated unit. The primary design intent for the inner ring rotation variant is to facilitate scenarios where the shaft or the inner ring is the rotating element, a common requirement in many precision machinery setups.

The technical features of these bearings are meticulously crafted to deliver superior performance. The rollers make line contact with the raceways, a critical design aspect that significantly increases rigidity and minimizes elastic deformation under load compared to point contact found in ball bearings. This results in exceptionally smooth and precise rotation with minimal runout. The bearings are available with either a one-piece or split-type inner ring, with the split-type design offering simplified assembly and maintenance, particularly in applications where other components are mounted on the shaft. High-grade bearing steel, advanced heat treatment processes, and precision grinding of all contact surfaces ensure high load capacity, long service life, and consistent performance. Optional sealing units are also available to protect the precision rolling elements from contaminants like dust and moisture, enhancing reliability in harsh operating environments.

The performance advantages of THK Cross Roller Bearings for Inner Ring Rotation are substantial and directly address the challenges of modern industrial automation. Their high rigidity translates into improved machining accuracy and surface finish in equipment like machine tools, as it prevents deflection under cutting forces. The compact cross-section allows for the design of more slender and space-efficient machinery, a crucial factor in robotics and semiconductor manufacturing equipment where every millimeter counts. Furthermore, the ability to handle moment loads eliminates the need for multiple bearing arrangements, simplifying system design, reducing parts count, and lowering overall costs. The high rotational accuracy ensures precise positioning and repeatability, which is paramount in applications like rotary tables, indexing heads, and industrial robot joints.

Typical applications for these bearings are found wherever precision, rigidity, and a compact footprint are non-negotiable. In industrial machinery, they are the core component of rotary tables for machining centers, enabling high-speed, high-precision multi-axis milling and grinding. Within the realm of robotics, they are indispensable in the revolute joints of articulated robot arms, providing the stiff and accurate rotation required for complex assembly and welding tasks. In the automotive sector, they are utilized in advanced manufacturing and testing equipment, such as the rotary indexers for automated assembly lines. Precision equipment, including semiconductor wafer steppers, optical inspection devices, and medical imaging systems like CT scanners, relies on these bearings for their vibration-dampening characteristics and flawless rotational smoothness, ensuring the highest levels of operational fidelity.

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Standard Model RU SERIES
THK's RU SERIES Cross Roller Bearing for Inner Ring Rotation represents a pinnacle of precision engineering in linear motion components, specifically engineered to deliver exceptional rotational accuracy, rigidity, and load capacity in demanding applications. This standard model features a compact, integral design where cylindrical rollers are arranged crosswise at 90 degrees to each other between the inner and outer rings, with each roller alternating direction in a single-row configuration. This unique cross-roller arrangement enables the bearing to simultaneously withstand radial, axial, and moment loads with high stiffness, eliminating the need for multiple bearing assemblies and simplifying mechanical design. Key technical features include the use of high-grade bearing steel for all critical components, ensuring durability and long service life under heavy loads and high-speed rotation. The inner ring rotation design is optimized for applications where the shaft rotates, providing stable and precise motion control. The RU SERIES incorporates precision-ground raceways and rollers, resulting in minimal rotational torque variation and smooth, consistent operation. Standard models are available with either tapered holes or threaded holes for secure mounting, and they come pre-lubricated with high-performance grease suitable for a wide range of operating temperatures and environments. Optional seals are available to protect against contamination in harsh conditions, further enhancing reliability. Performance advantages are substantial, starting with superior rotational accuracy, typically within microns, making these bearings ideal for precision positioning systems. The high rigidity minimizes elastic deformation under load, maintaining accuracy even during high-speed operation or when subjected to complex combined loads. This design also offers space-saving benefits, as a single RU bearing can replace traditional two-bearing setups, reducing overall assembly size and weight. Additionally, the low friction characteristics contribute to energy efficiency and reduced heat generation, extending the operational lifespan of both the bearing and the surrounding components. Typical applications span across various high-precision industries. In industrial machinery, RU SERIES bearings are integral to rotary tables for machining centers, indexing heads, and industrial robot joints, where precise angular positioning and high load capacity are critical. Within automotive systems, they are employed in advanced manufacturing equipment, such as welding robot rotators and automated assembly line turntables, ensuring reliable performance in high-cycle production environments. In precision equipment, these bearings are found in semiconductor manufacturing devices, optical instrument stages, and medical imaging system gantries, where uncompromising accuracy and stability are paramount for sensitive operations. The versatility and robustness of the THK RU SERIES make it a cornerstone component in advancing automation and precision across modern industrial and technological sectors.
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Model RAU
The THK Cross Roller Bearing for Inner Ring Rotation Model RAU represents a precision-engineered rotary bearing solution designed specifically for applications requiring high rigidity, exceptional rotational accuracy, and compact design efficiency. Characterized by its cross-arranged cylindrical rollers alternating at right angles between the inner and outer rings, this configuration enables the bearing to simultaneously withstand radial, axial, and moment loads with a single unit, eliminating the need for multiple bearing combinations and simplifying assembly structures. The inner ring rotation design is optimized for scenarios where the shaft or inner ring serves as the rotating element, providing stable performance under high-speed operational conditions. Key technical features include a compact and lightweight structure achieved through a thin-walled, cross-roller arrangement, which minimizes the overall footprint while maximizing load capacity. The bearing incorporates precision-ground raceways and rollers manufactured from high-carbon chromium bearing steel, subjected to rigorous heat treatment processes to enhance surface hardness and wear resistance. Optional sealing units are available to prevent contamination from dust, debris, or moisture, ensuring longevity in harsh operating environments. Pre-load adjustments can be applied to eliminate internal clearance, resulting in higher rigidity and minimal deflection under load, which is critical for maintaining positional accuracy. Performance advantages of the RAU series are evident in its high rotational accuracy, with runout tolerances maintained within micrometers, making it suitable for precision indexing and positioning tasks. The bearing’s ability to handle complex combined loads reduces vibration and noise, contributing to smoother operation and extended service life. Its low starting torque and consistent rotational torque enhance energy efficiency and reduce power consumption. Additionally, the simplified design reduces the number of components required in a system, lowering maintenance demands and total cost of ownership. Typical applications span across various high-demand sectors. In industrial machinery, the RAU bearing is integral to rotary tables for machining centers, robotic arm joints, and indexing units in automated assembly lines, where precise angular positioning and rigidity are paramount. Within automotive systems, it finds use in electric power steering mechanisms, transmission testing equipment, and brake disc machining fixtures, offering reliability under dynamic loads. In precision equipment, the bearing is employed in medical device actuators, optical instrument rotators, and semiconductor manufacturing apparatus, where minimal vibration and high accuracy are non-negotiable. The THK RAU series thus stands as a versatile and robust solution for advanced motion control challenges.
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