Linear Motion
or quiet operation. Here’s how they work: A pressure regulator sends pressurized fluid between the rail and carriage. That lifts the carriage off the guideway by about 0.01 mm or so. Aerostatic versions use air as the fluid; hydrostatic linear bearings use specially formulated hydraulic oil. This type of guide is difficult to manufacture and expensive, but damps vibrations and allows for moves to 120 m/min. and 10 g—useful for ultraprecision machines. Linear-rail lubrication Some linear-motion systems need periodic application of lubricant, but many are available pre-lubricated. In addition, a number of systems use self-lubricated moving elements, eliminating the need for lubrication during the useful life. Note that the rails, ways and guides of linear motion systems tend to pick up dirt and debris from their application environment. For this reason, use carriages and slides with some kind of wiper system to keep the systems clean. When selecting linear systems, engineers should consider space limitations, accuracy needs, stiffness, travel length, magnitude and direction of loads, moving speed and acceleration, duty cycle, and the application’s environment. Note that an excessively large load or an impact load can permanently deform the raceway surface whether the linear guideway is at rest or in motion. Most manufacturers offer tables on the basic dynamic load rating, which can help engineers determine the proper load ratings for a system. Another caveat about friction: Friction measurements are carried out on all profiled rails. The friction values are given in tables in the manufacturers’ respective product catalogs. The level of friction depends on load, preload and sealing, travel speed, lubricant and runner block temperature. Total friction from a runner block includes associated rolling or sliding friction, lubricant friction and the friction of any seals.
This Schaeffler INA Linear Technology is a linear recirculating-ball bearing and guideway assembly. Called the KUVE-B-HS, it has conventional steel rolling elements for speeds to 10 m/sec. Plastic in the recirculation mechanism prevents rolling-element tilting and pulse loads. The guides run on standard guideways.
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