A new brochure describes the application of Holo-Rol cylindrical roller bearings for reduced vibration and lower runout on machine tools. The bearings are said to increase accuracy and last longer than ball bearings.
Cylindrical rollers reportedly have greater radial stiffness and vibration damping than conventional ball bearings because the cylinders can be preloaded. This improves accuracy, especially on machine-tool spindles and high-speed grinding machines. The reduced vibration also extends grinding-wheel life because the bearings run truer so the wheel doesn't have to be dressed as often. And the bearings run cooler. Hollow rollers weigh less than solid rollers, which reduces centrifugal forces at high speeds and quickly dissipates heat.
The bearings come in four basic types designed to replace standard "light" and "extra-light" series ball bearings and straight or tapered cylindrical roller bearings commonly used in machine-tool applications. The brochure includes dimensional data, maximum loads, and maximum operating speeds for each type of bearing.
This information supplied by Kaydon Corp., Muskegon, Mich.
Hollow Rollers Damp Vibration
An Engineering Data section in the Holo-Rol brochure provides design information on topics such as lubrication techniques, tolerances, and vibration damping. For instance, according to the brochure, imbalance is a major cause of vibration in machine spindles. Hollow-roller bearings damp vibration because the rollers control shaft position.
Preloaded hollow cylindrical rollers are essentially stiff springs. Resistance to bending makes them act as shock absorbers that damp radial spindle motion. Hysteresis in bending causes the rollers to resist rapid changes in shape and produces a strong centering force on the spindle. This centering action also counteracts centrifugal (unbalanced) forces that cause vibration in machine spindles. Vibration of spindles using hollow-roller bearings is reduced to 50% of solid roller bearings. This is especially beneficial for grinding machines because it produces better finishes and closer tolerances.