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Ceramic rollers follow a smooth path.

Hybrid bearings combining silicon nitride rollers and metal races run faster and longer than their all-steel counterparts, according to Paul Johnson, a staff engineer specializing in ceramic roller manufacturing at MRC Bearings in Jamestown, N.Y.

Because the ceramic rollers weigh 60 percent less than similar-size metal rollers, there's less inertia to overcome when stopping or starting. Lower weight reduces the centrifugal force that rollers exert on outside races, raising the speed that the bearings can attain. Ceramic rollers typically demand less lubricant than their steel cousins and expand less, too.

Their light weight suits the ceramic bearings to aerospace applications, where MRC--a division of SKF--concentrates its efforts. Ceramic roller bearings have been used in jet and rocket engines and are beginning to show up on helicopter transmissions, Johnson said.

MRC produces many of its rollers from Cerama ceramic roller blanks made by Saint-Gobain Ceramics of East Granby, Conn. The blanks arrive at MRC 1/2 to 1 mm over what their finished size will be, including a reaction layer formed during the isostatic pressing of their manufacture.

Where making steel or ceramic balls is an almost unattended process, one that has been perfected over the years, many other considerations besides sphericity, size, and defects go into making rollers, Johnson explained. Roller makers need to consider diameter, length, corners, crowns, and runout, he said.


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Title Annotation:Power Transmission And Motion Control
Comment:Ceramic rollers follow a smooth path.(Power Transmission And Motion Control)
Author:Sharke, Paul
Publication:Mechanical Engineering-CIME
Article Type:Brief Article
Geographic Code:1USA
Date:Nov 1, 2003
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