Sealing and lubrication of ballscrews achieved simultaneously with extension of K1 seal technology from NSK-RHP; two new greases also available
Sealing and lubrication of ballscrews achieved simultaneously with extension of K1 seal technology from NSK-RHP; two new greases also available
Keywords Lubrication,Sealing
Both sealing and lubrication of ballscrews can be achieved simultaneously with the extension by NSK-RHP of its unique K1 seal technology. The newly developed K1 seal, for which a patent is pending, is manufactured from a "porous synthetic resin". The material is oil impregnated to eliminate the need for re-lubrication and enhance long-term ballscrew performance. The introduction of the K1 seal technology to NSK-RHP's range of ballscrews follows its initial development for linear guides. Overall, the technology is revolutionizing the performance of machines, in terms of reliability, maintenance free intervals and operation in environments exposed to contamination such as dust and or water. The effectiveness of the K1 technology should also enable machine builders to make real cost savings by replacing existing, and often costly, methods of lubricating precision machine parts. The K1 seal is produced from an NSK-developed material called "Moulded Oil". Moulded Oil is a plastic containing lubricating oil. It differs from other marketed oil impregnated plastics, where the oil content is a mere few per cent by weight, by offering a lubricating oil content of more than 50 per cent by weight. The oil discharge rate from the new material depends on the operating temperature. Moulded Oil has lubricating oil enclosed among polyolefin molecules. When the temperature rises the polyolefin molecules tend to shrink,resulting in discharge of the lubricating oil, allowing more lubricating oil to be supplied through slide heat generation when needed. The K1 seals are particularly effective in environments where oil-related pollution must be avoided, for example in the food industry and during manufacture of semi-conductors and medical equipment. The use of this technology overcomes problem areas such as lubricant loss when washing down equipment, situations where lubricant is difficult to apply, and other manufacturing operations where oil and grease-absorbing dust is produced such as in the woodworking industry.
In many applications today, high speed operating conditions are compounded by the high temperatures at which the bearings work. This is particularly true of bearings in electrical prime movers and auxiliary equipment installed around automotive engines. The deep groove ball bearings used in these applications may also have to contend with salt and turbid water, not to mention high loads and vibration. NSK has developed two high performance greases for these types of applications. Both ENS and ENR greases use a polyester oil with a diurea thickener. The greases are claimed to have:
superior shearing stability, with less grease leakage during high speed rotation and outer ring rotation;
superior high temperature durability with long grease life at temperatures up to 160°C;
good low torque performance; less abnormal noise in the bearings during cold starts;
superior water resistance of the thickener, which makes softening and outflow difficult even when water may enter the bearing.
The latest challenge has been to develop a new generation of seals which combine high levels of sealing with speed capabilities similar to those of shields. NSK's V type seal was developed for this very purpose. In contrast to conventional seals, V types are non-contact units which are held in the outer ring of a bearing by the elasticity of the rubber seal material. With this design friction is not a problem. Consequently, bearings employing the seals can be used at the same high speeds as bearings equipped with shields. However, compared to shields, V type seals provide better grease sealing efficiency and resistance to the ingress of fine dust particles. Offering a solution somewhere between the standard contact seal and the V seal is NSK's newly developed DDW seal. A light contact device,the DDW seal facilitates high speed operation but not to the same extent as shields or V type seals. In overall sealing terms, though, it is much superior,both in respect of resisting moisture and dirt ingress. The DDW seal also offers advantages over the standard contact seal. Its innovative design means that the support for the main seal lip is long and thin, resulting in light contact and low torque operation. Starting torque is approximately one half that of the standard seals and running torque is also lower. Finally, the main ring has outward contact with the inner ring seal groove, so internal pressure does not open the seal and allow grease leakage to contaminate a process or impair the long-term operation of the bearing itself.
For more information contact Penny Lawrence, Marketing Communications Dept., NSK-RHP UK Ltd, Mere Way, Ruddington, Notts. NG11 6JZ. Tel: +44 (0) 115 936 6600.
