THE problem of providing seals in standard angular contact bearings has been solved by FAG/Barden with a revolutionary new design.
The 2RSD bearings, available from CGB Precision Products , enable spindle builders and users to enjoy the cost, life and maintenance-free benefits of grease lubrication.
Ready to fit, lubricated for life, and maintenance free, they are completely interchangeable with standard non-sealed bearings, but offer up to five times the grease life.
Angular contact bearings have for many years been the established rolling element for use in machine tool spindles. The standard configuration for these bearings is to have one outer ring land relieved.
Unfortunately, with this design there is insufficient material cross section in which to machine a standard seal recess. Without this the bearing cannot be supplied with seals or shields.
FAG/ Barden has made this process unnecessary with a new seal and recess design for standard angular contact bearings.
The depth of recess is not as great as that provided on standard deep grooved bearings and can be machined into the narrow cross section of the relieved side of angular contact outer rings.
This enables seals to be fitted to retain grease and exclude contamination from both sides of the bearing.
The RSD seals have retention characteristics equal to standard seal designs, but are fitted in such a way that there is no contact with the bearing inner rings. As a result, friction is minimised and there is no rise in the bearing operating temperature.
The Barden design also overcomes problems of ring distortion from seal radial pressure, and it provides additional operational benefits as the space between seals and balls serves as a grease reservoir.
The B7-2RSD (standard sealed) and HCB7-2RSD (sealed with ceramic balls) spindle bearings are ready to fit and offer the advantage of being lubricated for life, under controlled conditions by the manufacturer.
For the OEM and user this means ease of handling and greater operational security.
Lubrication performance is optimised because the correct amount of grease is applied to the bearing in the correct position close to the contact zone, with no risk of contamination.
This operation also relieves the user of the time consuming and messy operation of washing out and re-greasing prior to fitting of the bearing.
Operational test have shown that even after many operating hours the sealed bearings are still much cleaner inside than non-sealed types.
The effectiveness of the seals not only means that foreign particles are excluded from the bearing, but also that more grease is retained because airflows are unable to dry it out.
The lubrication life of the grease is prolonged, therefore, and this, combined with the bearings unique Cronidur "30 material specification, results in significantly improved bearing life - up to five times that of standard open type angular contact bearings.
This improvement in bearing life means reduced costs to the user over the longer term. However, with the new seal developments, even greater cost savings can be made at the "front end" of new spindle investments.
This is because the package of sealed, greased-for-life spindle bearings, supplied with new high technology greases and ceramic balls, is increasingly being used as a replacement for complex, and costly, re-circulating oil lubrication systems in many applications.
The general benefits provided by the new sealed bearings are of special significance with regard to vertical or inclined machine tool spindles. The excellent grease retaining characteristics mean that, irrespective of the bearing position, lubricant migration is minimised.