Design modifications lead to 50% longer operating life

Targeted at machine building, automation, control, robotics and general engineering applications, Schaeffler UK’s new light range of linear ball bearings offers design engineers a range of technical benefits, including smoother running characteristics, higher load carrying capacity and up to 50% longer operating life.

The KN ..B-PP range is the latest addition to Schaeffler’s existing, well-proven KN/KNO series of linear ball bearings, which are designed to compensate for shaft misalignment in a diverse range of applications.

The unit comprises a high strength plastic cage with steel load plates, balls, shields and seals. The cage guides the balls and an external steel retaining ring supports the load plates. The bearings can support high loads, while having a relatively low mass and therefore enable the construction of linear guidance systems with unlimited travel.

In developing the KN ..B-PP linear ball bearing, engineers at Schaeffler took the existing KN/KNO series and completely overhauled the design, including optimising the load plates and introducing a ‘tapered’ lead chamfer entry zone for the balls. Due to the self-alignment function, the balls now run freely into the load zone and load distribution over the whole row of balls is now more uniform. These design improvements result in smoother running characteristics, higher accelerations and prevent overloading of the individual balls. In addition, noise levels are reduced and operating life is increased.

With standard linear ball bearings, the raceway plates can sometimes ‘rock’ about the retaining ring, leading to slippage and undesirable running characteristics. With the KN ..B-PP, the tapered lead chamfer and optimised load and raceway plates ensure that there is no slippage at high acceleration, and the unit is always slightly pre-loaded by the retaining ring. The new robust construction means the KN ..B-PP is self-aligning to ±30 angular minutes and can operate in temperatures up to 80°C.

The KN ..B-PP bearings are available in ‘open’ or ‘closed’ variants, the former having a segment cut out for supporting shafts. Highly effective double lip, polyester-elastomer rings are used on both sides to prevent ingress of contaminants into the bearing and to retain the grease inside. ‘Open’ type bearings are available with additional sealing strips. The units are maintenance-free for most applications.

Schaeffler can also supply the bearing as a complete support solution, comprising a housing and shaft, both optimally matched to meet the customer’s application. The housings are made from a high rigidity, high strength aluminium alloy that enables the full load carrying capacity of the ball bearings to be utilised. Due to their comparatively low mass, the units are suitable for lightweight designs with high loads and where higher accelerations and travel speeds are required.

The housings, which come in open, closed, slotted or tandem designs (fitted with two linear ball bearings), have threaded and counter bored holes that enable easy mounting on the adjacent construction.