Roller Bearings with 3.25 Million dmn

A company has developed an air oil lubrication ultra-high speed NU-type cylindrical roller bearing, featuring a dmn value of 3.25 million, for machine tool main spindles, used in machining centers.

The main spindles of high-speed machining centers and combined machine tools typically use duplex angular ball bearings in the front and either duplex angular ball bearings or cylindrical roller bearings in the rear. In the rear position, the high-speed performance of angular contact ball bearings is better than cylindrical roller bearings.

However, the main spindle structure is complex because the ball bushing or preload spring has to absorb thermal expansion of the shaft. On the other hand, when a cylindrical roller bearing is used, a structure absorbing thermal shaft expansion is unnecessary as the bearing itself can move axially but the high speed performance is inferior to the angular ball bearing.

Aiming to increase the speed rating of the cylindrical roller bearing while simplifying the main spindle structure, the company focused on the heat generation of the bearing, and developed an NU-type cylindrical roller bearing that allows speeds up to 3.25 million dmn.

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