Avoid cage creep

Back to Basics: When using linear roller bearings, various anti-cage creep mechanisms can help retain accuracy by limiting unwanted movement.

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When using linear roller bearings, various anti-cage creep mechanisms can help retain accuracy by limiting unwanted movement. The term "anti-creep" is used to describe the method of eliminating any slippage of the retainer holding the crossed rollers between the two V-grooved rails of the slideway.

It then can be used in any mounting direction and with lower momentum motors, such as linear motors. Anti-creep devices include rack and pinion mechanism; an external attachment made of plastic gears outside of the rail; and a metal gear inside of the rail. Some are quite expensive.

NB Corporation of America offers an anti-cage creep mechanism called the Studroller, which uses a roller with round balls studded around its surface. By placing studs in the center roller and machining a path along the rail, this retainer will never slip. It has the smoothest tracking motion and therefore is quieter. It is suitable for high acceleration, vertical mounting and uneven load distribution.

Since the Studroller from NB Corporation of America uses a ball bearing, as opposed to a gear or exterior control, it costs about half of what other anti-creep devices do. In addition, there are no redesign costs to replace a standard slideway. See how it works in a PDF by NB Corp. at www.nbcorporation.com/catalog/pdf/nv_nvt.pdf

- Naoki Yamaguchi is assistant technical manager for NB Corporation of America, www.nbcorporation.com. April 2010 "Back to Basics" inthe North American edition of Control Engineering has more about the advantages of linear bearings . Edited by Mark T. Hoske, editor in chief, Control Engineering , www.controleng.com.