Linear Slides and Linear Stages

Linear slides are simple linear motion devices composed of a stationary base and a moving carriage. Linear stages are slides with a drive mechanism that provide controlled, precise positioning along a linear axis. Linear slides and linear stages use several types of bearings and guide mechanisms. Air bearings ride on a thin cushion of air and provide support in only one direction. Ball slides use a bearing system composed of two rows of balls on both sides of the base. Ball spline shafts have ground grooves for the movement of recirculating balls. Crossed rollers are enclosed in rails with machined, V-shaped grooves that are ground at 90°. Dovetail slides are interlocking, direct contact systems suitable for heavy load applications. Hardened way slides or box ways are similar to dovetail slides, but use the direct contact of the base and saddle. Linear bushing systems contain recirculating linear bushings and a shaft, shaft support, and carriage. Linear motion guides or square rail linear bearings include a guide rail and carriage unit. Needle rollers or M/V ways are housed in cages mounted on matching machined rails. One roller is machined in an M-shape. The other is machined in a V-shape. Linear slides and linear stages with plain bearings and sleeve bushings are also available. 

Selecting linear slides and linear stages requires an analysis of axis configuration and travel specifications. Single-axis systems have only one carriage or saddle and move along the X-axis. By contrast, vertical lift devices move along the Z-axis. Some stacked or coupled units move along two, usually orthogonal, axes in the X-Y plane. Others include one carriage that moves along the X-axis and another carriage that moves along the Z-axis. Three-axis systems provide motion in three orthogonal axes. Important travel specifications for linear slides and linear stages include X-axis linear travel, Y-axis linear travel, and Z-axis linear travel.

There are many drive types and drive mechanisms for linear slides and linear stages. Manually powered devices include a handwheel or crank. Motorized systems include an AC motor, brushless servomotor, DC servomotor, linear motor, stepper motor, pneumatic motor, or hydraulic motor. Linear slides and linear stages with motor mounts do not have an integral motor, but are equipped with hardware for mounting a user-supplied motor. Drive mechanisms for linear slides and linear stages use ball screws, ground screws, lead or acme screws, belts and bands, cables and pulleys, micrometers, or racks and pinions. Devices without an integral drive mechanism are also available. Important drive specifications for linear slides and linear stages include lead screw pitch, positioning accuracy, dynamic load carrying capacity, and maximum linear velocity or speed. 

Linear slides and linear stages differ in terms of output feedback options and features. Home switches define a specified reference point. Travel limit switches define the ends of travel. Rotary encoders and potentiometers are used to sense motor position or table position. Tachometers measure the speed of a rotating shaft in revolutions per minute (RPM). Some linear slides and linear stages include a brake assembly for slowing or stopping linear motion, or a lock for maintaining carriage position. Others provide a clutch assembly for connecting or disconnecting the drive mechanism. Brake / clutch combinations are commonly available. Stackable, side-mounted, cleanroom-rated, and vacuum-rated systems are used in specialized applications. Double-carriage devices are equipped with two sliding carriages. Rotary axis linear slides and linear stages include a multi-axis stage in which the last axis (Y or X) is capable of rotary motion. Way covers or bellows are often used to cover rails and guides. Wipers or scrapers are used to clean rail and guide surfaces.

• Ball Slides
  Ball slides are sometimes referred to as ball and rod bearing assemblies, or ball bearing slides. Ball slide stages are simply ball slides coupled with a drive mechanism. The result is a very smooth...
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