Among the innovations being presented by NSK at EMO 2019 is a new series of ball screws which, among other things, achieves a service life that is around three times longer when subjected to high loads. Of enormous benefit to machine tool builders and users, this longevity is made possible by a specially devised surface texture that promotes improved oil film formation.Like all mechanical components, ball screws are subject to wear. One of the constant development goals of NSK’s research is to continuously reduce friction, and thus increase service life.
Before commencing development, NSK noted that typical damage patterns on the surface of ball screws can be traced back to inadequate lubrication, which leads to direct metal-to-metal contact between the shaft and nut. The shafts of precision ball screws are precision ground, and their surface texture appears under a microscope as a strip. Unfortunately, oil can easily run off these micro-strips, soon leading to inadequate lubrication.
On the basis of these findings, NSK set about developing a new surface treatment that produces a flat texture with micro-recesses. Even the smallest oil deposits can settle in these recesses and prevent inadequate lubrication, permanently and effectively. The nut thus moves constantly on an oil film, reducing wear on the ball screw, especially during slow and short strokes.
Compared with standard NSK ball screws, service life is increased by a factor of three. In addition, the new surface texture reduces break-away and stick-slip effects, even during the aforementioned slow and short movements.
The new series is suitable for use in machine tools that perform high-precision machining operations, such as milling centres for mould and die production, spark erosion machines, grinding centres, and other similarly challenging applications.
NSK’s ball screws featuring the new surface texture will be available in pitches from 10 to 50, in accuracies of C5 and better. The company is presenting the ball screw on Booth B34 in Hall 7.
