NSK Develops Low-Particle-Emission, High-Performance Bearing for Servomotors

Achieving Low-Particle-Emission Performance,1 Long Life, and Low Torque with New Grease and Seal Technology

●Improvements identified by research into the mechanism behind malfunction and a higher-precision evaluation and testing method

●New grease and seal developed, delivering twice the low-particle-emission performance of conventional products

●Contributes to stable operation of industrial machinery such as industrial robots

1 Low-particle-emission performance: Prevents grease and oil spraying out of the bearing.

　NSK Ltd. has developed a low-particle-emission, high-performance bearing that contributes to stable operation of industrial machinery such as industrial robots.

　In fiscal 2024, NSK will begin accepting orders for samples of this new product, targeting annual sales of 1.5 billion yen in fiscal 2026. The new grease and seal developed for this bearing are not only for use in servomotors; they are finding applications to other products that require low-particle-emission performance, contributing to stable operation in a wide range of industrial machinery.

1. Background

　With a dwindling workforce and advances in industrial automation, the market for robot servomotors continues to grow. Servomotors are used in robot joints and operate in demanding conditions such as high temperatures and sudden changes in speed, accurately controlling robot movement positions and speed, and taking on the role of precision positioning.

Bearings employed in servomotors are used near essential functional components for precision positioning such as encoders and brakes, and bearing grease and oil can scatter, sticking to the disks (disk contamination). This can cause failures such as encoder read errors and slipping brakes, resulting in robot operation stoppage. Because of this, there is greater demand than ever for bearings with low-particle-emission performance. NSK has addressed this need by developing anti-scattering grease and seals that offer a high level of hermeticity.

　Higher precision designs in recent robots and the growing market have created demand for even more reliable servomotors, driving the need for better low-particle-emission performance from bearings. However, there were multiple obstacles: the mechanism of disk contamination was unknown, and it was not possible to obtain high-precision assessments with conventional low-particle-emission performance evaluation and testing methods.

2. Technology

　1) Researching the mechanism behind disk contamination

　NSK inferred the mechanism behind disk contamination, then verified the inference using visualization, evaluation, and testing of the phenomena.

　2) Higher precision evaluation and testing

　Using NSK evaluation reproduction techniques, NSK produced a test machine with a structure and environment similar to an actual servomotor. The machine produced precision test results, allowing the development of a product with superior low-particle-emission performance.

　3) More advanced design elements

　Thanks to the clear understanding of the mechanism and the advanced testing method mentioned above, NSK was able to identify elements that required improvement. Using tribology technology2 cultivated over many years at NSK, NSK succeeded in developing grease and seals with superior low-particle-emission performance.

2 Tribology technology: Controlling friction and wear via grease and material surfaces

3. Features

The new grease and seal deliver twice the low-particle-emission performance as conventional products. The grease also lasts much longer, and the seal provides lower torque.

1) New grease: Restrains evaporation in high-temperature environments, and uses superior thermal-resistant components to achieve the following:

● Low-particle-emission capability: twice the performance of conventional products

● Enhanced resistance to seizing: double the conventional lifespan

2) New rubber seal: Development of a new lip3 shape design achieves the following:

● Low-particle-emission capability: twice the performance of conventional products

● 10% lower torque: reduced contact friction between the seal and inner ring than conventional products