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Machine Design

Cage keeps bearings in line and lubricated


Ball-to-ball friction in bearings generates heat, limits the speed, and shortens the life of linear-motion guides. To solve these problems, engineers at THK designed a caged-ball system that places recirculating bearings in a retainer, or cage, that separates and aligns the bearings. The cage creates a bearing chain with spaces, or grease pockets, to hold lubricant and keep the bearings from touching each other.

Separating the bearings provides several benefits. Because the bearings are not in contact with one another, there is much less metallic noise during operation. The lack of bearing-to-bearing contact also decreases wear and allows room for lubricant, two factors which promote long-term, maintenance-free operation. Meanwhile, the lack of bearing noise or vibration means rolling resistance is more uniform, keeping performance of the linear guide consistent. And reduced heat levels and low bearing stresses lets the linear guide move at higher speeds.

The caged-ball technology is especially well suited for medical devices and semiconductor-inspection applications, according to THK, and is available in a wide variety of linear-guide models.

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