The demands that industry places on linear guides are becoming higher: they must be suitable for very fast applications, offer increased operational lifetime and cope with higher loads. The new precision UK manufactured NH and NS series linear guides from NSK satisfy all of these criteria, thereby enabling machine builders to either increase the performance of their products or to downsize.
Many engineers regard the introduction of new mechanical systems that replace tried and tested technology with mixed feelings; however, in this case there is nothing to fear as the new guides are dimensionally directly interchangeable with the outgoing LH and LS series models. Machines therefore only need to re-designed if the downsizing option is taken.
Kevin Delehanty, Principal Application Engineering at NSK UK, in Newark, Nottinghamshire, explains: “The new NH and NS series have a 30 per cent higher dynamic load rating. We have achieved this by further optimising the geometry of the ball grooves.” The new design ensures a more uniform distribution of forces between the ball and the groove. Conversely, this means that the contact surface pressures for the same loading are significantly lower, allowing the dynamic load ratings to be revised according to ISO guidelines.
The result is a dynamic load rating that is at least 30 per cent higher, and the fatigue life is doubled. In real numbers this means that the calculated service life of the NH25AN linear guide, for example, is 2.24 times that of the LH25AN. At the same time the noise level drops by an average of 3 dB(A). This is great for new designs, but what has changed for the engineer who is already using the old NSK linear guides?
Kevin Delehanty stresses: “The dimensions have not been changed at all. Also unchanged is the high degree of self-alignment of the slide on the rail due to the face-to-face arrangement of the bearings, resulting in lower internal loads compared to a back-to-back arrangement. This allows the linear guide to compensate for greater installation errors without significantly reducing the service life.” Optionally, the new versions can also be used together with the NSK K1 lubrication units, which have proven their worth over many years increasing reliability and longevity.
Kevin Delehanty goes on to explain that not only is the changeover to the new series unproblematic; it is also possible to mix old and new components in the same machine or system. When the components are mixed, however, the load rating of the old series applies, as the weakest link in the chain determines the service life of the system. Another advantage of the new series, besides the longer service life, is the fact that they can be operated at considerably higher speeds – again, without having to modify the machine.
A completely redesigned ball circulation system
Owing to the use of high-speed end caps, the maximum allowable speed has been increased by a factor of three compared with their predecessors. Instead of 100m/min., the new NH/NS series are able to traverse at 150–300m/min. At the same time the smooth-running properties and the noise levels have been improved due to a completely redesigned ball circulation system. This allows the balls to be guided much more smoothly out of the load zone into the return cap.
The new series can be employed in a wide range of possible applications. Kevin Delehanty explains: “In principle, this covers all applications in which something moves and where precision, speed, service life and process reliability are important factors.” They are suitable for applications that need to be precise and free of play in metal-cutting machines for example; medical equipment, semiconductor manufacturing, packaging machinery, robots and in material handling machinery in general.
In addition, NSK believes the option of downsizing to be of importance. Due to the higher load ratings it is possible to replace the linear guides previously used with significantly more compact versions with the same service life. A typical example: Instead of an LH30AN guide, the engineer can now select a more compact NH25AN that is 20 per cent narrower and 10 per cent lower. Moreover, it weighs about 30 per cent less. Kevin continues to explain: “This option allows the engineer to design a system that is more compact, lighter and thus also cheaper, with no loss of functionality.”
UK availability for this new range is also very good as it is precision manufactured at NSK’s state-of-the-art bearing plant and European stock facility in Newark, Nottinghamshire. There is also a flexible precision engineering facility based at Newark that can design and assemble bespoke assemblies; for example, cut rails to custom lengths, change the carriage preload or change the lubrication. The workshop has significant capacity and can also completed orders on short lead times due to its close proximity to the stock and manufacturing facilities.
For further information about NH and NS series linear guides from NSK, please go to www.nskeurope.com.