Caged balls improve new ballscrew performance

Two new ballscrews collectively offer significantly improved levels of performance over previously available devices.

Two new ballscrews collectively offer significantly improved levels of performance over previously available devices.

In particular, the SBK and SBN ballscrews from THK provide exceptionally smooth rotational movement with DN ratings (the product of bore and rotational speed) up to 160,000 and 130,000, respectively - making them twice as fast as many competing ballscrews - an operating life that can be three times that of traditional devices, minimal maintenance and a reduction in noise levels of around 6dB.

The SBK and SBN have been designed at THK's extensive research and development centre in Japan and are intended for use with a wide range of production equipment, including machine tools, industrial robots, high speed transfer units and pick and place systems.

The two ballscrews both achieve exceptional levels of performance by incorporating THK's proven caged ball technology within the ballscrew nut assembly.

The caged ball mechanism is essentially a series of separators between the balls that run between the screw shaft and ballscrew nut to provide smooth and precise motion.

The caged ball system eliminates the problems of noise, friction, heat and wear, commonly associated with conventional ball race configurations, by enclosing high precision stainless steel balls within a separator cage, with controlled density grease pockets on the circumference of each ball.

This effectively prevents contact between balls when in operation, leading to significant improvements in both overall performance and operating life.

The two new products differ, however, in the way in which they use the caged ball system within the recirculating mechanisms in each ballscrew nut assembly.

The SBK being a high lead product uses an end cap method of recirculation, to enable the highest speeds to be achieved.

By comparison, the SBN uses a special geometry return tube within the nut to pickup and recirculate balls back to the beginning of the load zone.

A number of options are available for both ballscrews, including THK's QZ lubricating system, that continuously applies oil directly to the raceway by means of a compact reservoir and high density fibre applicator, and specialised wiper rings, that protect the ballscrew nut and shaft from damage by accumulated dirt or debris.

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