Where cylindrical roller bearings are concerned, NSK believes that
design choices can cut costs, while yielding greater reliability and
longer life
The pressurised, cost-down nature of global manufacturing, means that
bearings employed in modern machines and equipment must perform well at
higher speeds and under higher loads than at any time previously. What is
more, they must provide these enhanced levels of performance with market
leading levels of reliability. One of the major implications of these
requirements for the design engineer is that some applications, once
designed using ball bearings, can no longer meet today's demands for
L10life1 (the nominal rating life assuming a 10% probability of failure
in any statistical batch) or reliability. As a result, cylindrical roller
bearings (CRB) are increasingly being employed as a higher performing
alternative.
High kilowatt electric motors are a good example of this substitution
process in operation. In many electric motor applications the drive end
bearing is a ball bearing. However, a significant number require the
bearing to carry a radial load that is too high for a ball bearing to
yield a satisfactory L10life1. This problem can be overcome by
substituting a cylindrical roller bearing.
Another consideration in today's highly competitive global markets is
cost reduction. The substantial developments in materials, mechanical
design, lubrication and sealing that have occurred in bearing design over
the last decade mean that in many applications bearings can be downsized
to reduce costs - and size and weight - without affecting machine
performance. A typical example of this initiative in operation is the
replacement of pairs of angular contact bearings, with single cylindrical
roller bearings in motorised machine tool spindles.
NSK is in the vanguard of the movement to achieve cost reduction through
downsizing with two new designs of cylindrical roller bearing, the EW and
EM series. Both of these products provide a higher performing substitute
for ball bearings in applications where increased performance demands
mean that the latter cannot offer either the life, or the levels of
reliability required.
The EW and EM designs permit downsizing due to an increased complement of
larger rollers and novel high strength cages. In the case of the EW
series these design improvements result in a radial load capacity
exceeding that of conventional CRB bearings by between 17 and 20%,
without any reduction in axial load capacity (depending upon the design).
This results in an improvement in theoretical operating life by as much
as 70%.