More about Linear Slides

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Linear slides use a multitude of complicated design principles to achieve an uncomplicated goal: precise movement along a straight plane. They consist of two main parts, a stationary base and moveable carriage. The carriage moves along the base, separated only by the rolling element: the bearing. Bearings for linear slides include ball bearings, air bearings and crossed roller bearings. Ball slides use rows of ball bearings to allow the carriage to slide over the base. These slides are generally used for applications involving loads less that two hundred pounds and distances under a foot.

Crossed roller slides have greater load carrying capacity and are capable of higher accuracy. They offer smoother movement than similarly sized ball slides. Crossed roller slides involve a number of cylindrical rollers and a raceway. Half of the cylindrical rollers are able to roll in one direction, while the other half allow movement in a perpendicular direction. The height of each bearing is slightly smaller than the diameter of the opposing cylinder. They are cross-positioned to each other. One set of cylinders rolls along the vertical axis of the cross, while the other rolls along the horizontal axis. In most slides they are positioned diagonally rather than directly up and down and side to side. Each roller contacts the raceway along a line, unlike a ball bearing, which only meets at a single point. Although crossed roller slides can have better accuracy, they are easily damaged by dust and other particles, whereas ball slides are self-cleaning.

Common uses for linear slides are in automated manufacturing machinery, industrial press arms, heavy duty doors and specific positioning tasks. Typical slide materials are stainless steel and coated aluminum, although many other materials are available, including polymers. The longevity and efficiency of a linear bearing depend on its regular load and speed, and the temperatures it must endure. Many bearings require lubrication to enhance this longevity and to provide better rolling functions. Grease and oil are the two most common lubricants, although each has its own set of pros and cons. Ball slides generally do not require lubrication.