When specifying a linear bearing, there seems to be dozens of products and manufacturers to choose from. But after closer inspection it becomes apparent that many of the products are similar even though different companies manufacture them. High-precision bearings were originally designed for machine tools. They’re typically extremely stiff and have high load capacities. Most also require machined mounting surfaces and hours of installation time to ensure parallelism and rail alignment.
When the product being designed does not require extreme amounts of precision and rigidity, machining the mounting surfaces and spending hours guaranteeing parallelism does not add functionality to the final product. It only complicates assembly and adds cost.
Most linear-bearing manufacturers try to convince engineers to modify their machine specifications to allow mounting high-precision, machine-tool bearings. Industries, such as assembly, material handling, medical, and packaging need linear bearings that mount easily and quickly to surfaces that are not exactly parallel. They need linear bearings that work well in contaminated environments without bellows and other extra components.
The Compact Rail System surpasses the need for high-load, intermediate-precision linear bearings that are easy to mount. Offering up to 0.004-in. linear precision, the devices are perfect for applications in which mounting ease is as important as quality of movement.
The sliders in the Compact Rail family run inside the steel rails along hardened raceways. The slider in the “K” rail guides movement and carries load. It also absorbs structural and assembly errors by tilting up to 2°. The slider in the “U” rail carries radial loads and Z-axis bending moments and moves up to 4 mm laterally within the rail. This design eliminates having to spend time machining mounting surfaces and tweaking the system to ensure proper movement. When mounted, the sliders in the K and U rails will “find home” and run without play.
Placing the raceways inside the rail protects them from damage and contaminants and lets the rail and slider mount compactly. Built-in, spring-loaded wipers in the heads and lateral seals on the sides of the slider keep the guides clean in the dirtiest environments. Individual sliders carry up to 3,300 lb and travel at up to 9 m/sec.
The “K + U” system absorbs rotational positioning errors, misalignments between lateral planes, longitudinal parallelism errors, and a combination of these while maintaining a proper preload. The system offers smooth movement whether or not mounting planes are parallel.
This information supplied by Rollon Corp., Sparta, N.J.
For more information, Circle 621.