NSK has developed tapered roller bearings and cylindrical roller bearings incorporating new pin-type cages that are claimed to have up to six-times the strength of conventional cages against the effects of shock loads. The bearings are made of a new bearing material called SAC steel, which can extend bearing life in harsh environments such as steel and aluminium mills, where bearings are exposed to wear particles from the gear teeth of large gearboxes.
The new cage design and material specification were developed as a means of addressing the problems of maintenance on large gearboxes in rolling mills. The sheer difficulty of removing and maintaining such large gearboxes, and the costly downtime commensurate with such maintenance, places the onus on components such as bearings to provide ever increasing levels of reliability and operating life - qualities that the pin-cage bearings have been designed to provide.
This new design of cage eliminates the clearance that conventional pin-type cages have between the pin and the cage side plate. Central to the design is a pin that runs through the bore of each roller; the pin works to maintain clearance between the roller and the cage, and spaces the rollers equally apart from each other. This newly developed design helps to improve cage strength by reducing force that would normally be applied to the welded areas of the cage side plate under operating conditions where large impact loads result from rapid acceleration and deceleration. Tests have shown that this new cage is up to six times more durable than conventional cages, and achieves higher reliability.
Complementing the performance of the pin cage design is NSK's SAC steel. Said to be unique to NSK, this bearing material provides enhanced durability against exposure to wear particles from the reduction gears. Test results show that bearings made from SAC steel have twice the service life of bearings made from conventional bearing steel.