Ball Bearings Ultra-precision Applications

Of all bearing industries, the rolling bearing industry has been the most successful in standardizing its products but taking into account the number of parameters necessary to select a particular bearing design diameter, section, internal clearance, cage type, lubricant type, and whether or not seals or shields are required, means that leading manufacturers may each have more than 50 000 standard designs to select from. However, very few of these bearings meet the criterion used in this article to define ultra-precision bearings, namely a motion error of less than 100 nm peak to peak.

There is a vast selection of rolling bearing types: single-row radial ball bearings, angular contact bearings, cylindrical roller bearings, tapered roller bearings, needle roller bearings, spherical roller bearings, and double-row and self-aligning ball bearings are just some of the principal types. Furthermore, within each of these categories there is a wide range of variants; single-row radial ball bearings, for example, are available in different grades of precision, with different ball sizes and internal clearances, with or without seals or shields, and with or without a pre-charge of grease as a lubricant. In this text, only two types of rolling bearing are singled out as being suitable for ultra precision engineering applications and these are the single-row radial ball bearing and the angular contact ball bearing. Even then, not all of the variants available within these types may generate the low motion error that is a basic requirement for ultra-precision applications. Generally, only the precision grades or low noise grades of ball bearing are likely to produce low motion errors. These types of ball bearing are widely used in high precision machine tools, quiet running electric motors, computer disc drives, and instrumentation, where they provide good but not exceptional running accuracy at a competitive price.

Apart from good running accuracy, ball bearings as distinct from other types of rolling bearings, have a number of other attributes that are useful in ultra-precision applications. They have low friction that minimizes thermal distortion and enables them to achieve high rotational speeds. They are versatile in terms of the types of load they can take and the types of lubrication they may be used with. They are easy to mount and preload in order to generate good static stiffness, eliminate free play and hence center the rings. Collectively these factors have made ball bearings a popular choice in most types of precision equipment and as a result, the manufacturing processes used to make ball bearings have been continuously improved to further reduce motion errors now, making them a clear choice over other types of the rolling bearing in most high precision applications.

The difference between single-row radial and angular contact ball bearings is their construction and hence the type of loads they can support. Single-row radial ball bearings have inner and outer rings with shoulders on both sides of the ball complement. With the balls being trapped by the ring geometry, assembly generally involves placing the inner ring inside the outer ring, fully ooff-center filling the gap between the two raceways with balls, snapping the inner ring into a central position, and then spacing out the balls ready for cage insertion. The assembly process thus limits the number of balls in the bearing and hence its load carrying capacity, but it can support axial loads in two directions as well as radial loads. An angular contact bearing has one shoulder relieved on one of the rings, usually the outer ring. The diameter of the relief is carefully controlled for the purpose of assembly, which comprises putting the cage and ball complement in position around the inner ring, heating the outer ring, and then moving it axially into position over the balls. When the outer ring cools the relief diameter is just sufficient to prevent the bearing from being separated. Thus the angular contact bearing can have a greater number of balls and hence a higher load carrying capacity and static stiffness than a single-row radial ball bearing, but it can only support axial load in one direction and radial load.

Single-row radial ball bearings are favored in precision engineering applications such as computer disc drives and precision electric motors, where low motion errors or low noise are a primary requirement. Angular contact bearings, on the other hand, are widely used in precision applications such as machine tool spindles and rotary tables where static stiffness is also important.

Shandong Langche Bearing Co., Ltd. was established in December 2017. Mainly engaged in P6, P5 motor grade zero bearings and ferrules, the main products are used in motors, automobile gearboxes, agricultural machinery and mining machinery, power tools and medical equipment and other industries, Langche Bearing is committed to building a high-end brand, implementing strict quality standards and meticulous Intensive quality control measures to improve product quality and service quality. To achieve growth, success and achievement together with every partner is the eternal goal.