Linear bearing

● Linear bearings generally use a pad, bushing, or roller system to carry a load on a rail that need not be a straight line. The rail can be most any length, although that dimension is limited by the actuator. 

● The durability of the bearing is determined by the load and required speed. Furthermore, rails can generally be any profile – simple flat surfaces, round polished rods, or complex profiles with polished ground surfaces on which balls or cylindrical rollers can ride. Hard and ground bearing surfaces work best.

● Bushings provide possibly the simplest linear bearing. These thin-walled cylinders can be injection molded of proprietary polymers infused with a lubricant. An oil-infused bronze design, also cylindrical, rides on a polished round rod. This linear-bearing classification is often referred to as slides.

● Purpose-built linear bearings are available for frequently encountered tasks, such as pull-out equipment drawers or storable work surfaces. These usually light-duty devices let polymer wheels or ball bearings ride on stamped or rolled steel rails. Telescoping arrangements allow designing pull-out equipment drawers into cantilevered positions while supporting up to 50 lb or more for maintenance.

● Heavier loads are carried by linear guides that use re-circulating ball or roller bearings in rectangular mounting pads or slide units. These are so constructed that a loop of balls or cylindrical rollers cycles into and out of a load area along shafts at most any required load. Two, three, and four rails can work in unison to carry loads that exceed the rating of one rail. The ball spline is a variation on this design. In it, the sliding unit is a cylinder with at least three and up to five circuits of re-circulating balls. There are dozens of cylindrical shapes to choose from.

● The linear bearing is used in conjunction with the cylindrical shaft for unlimited linear motion. Due to the point contact with quenched drive shaft, the ball allows small load. In addition, the steel balls rotate with minimal friction resistance, so as to obtain high-precision smooth movement. Therefore, this low-cost product is mainly used in light industry machinery that moves in straight line, such as CNC machine tool, laser welding machine, tile cutter, mitre saw, paper bowl machine, engraving machine, screen printing machine, etc.