Porous Media Radial Air Bearings

Description

New Way Air Bearings announced the launch of a new line of radial air bearings for use in precision rotary motion applications. These new modular components do not constrain rotary motion using a 360° housing as rolling element bearings do; instead they are positioned in combinations of 3-4 segments to support a rotor from just a small percentage of its circumference. When this rotor is also constrained axially – for example, using New Way flat round or rectangular air bearings – it will float on a five micron film of air, enabling frictionless rotary motion. The resulting assembly is simple, has only one moving part, and provides smoother, faster, more consistent and precise frictionless motion, without noise, vibration, or need for lubrication. “Rolling-element bearings have many limitations, despite their ability to carry impressive loads,” noted Drew Devitt, New Way Chief Technology Officer. “Our new radial air bearings are a non-contact solution, so they offer engineers all the advantages of frictionless motion: Much higher speed, greater precision, repeatability, and many other superior performance characteristics.” “A general rule thumb is that a radial air bearing will have 10% of the load capacity of a similar-sized rolling element bearing,” Devitt continued, “But it will also have 10 times the speed capability and 100 times less friction.” Indeed, rolling-element bearings are often oversized to provide for long life even in more lightly-loaded applications. This is because, as contact bearings, they will wear. Without contact, New Way radial air bearings will not wear, reducing the need for routine maintenance and replacement. They operate the same way in the tenth year of use as in the first. Further, there is no need for the fossil-fuel based lubricants required by roller bearings. As a significant side-benefit, New Way radial air bearings also run silent. But the big benefits come from the elimination of contact and, consequently, of friction. There is no startup friction or stick slip. And because friction at high speed is still essentially zero, it takes less energy to keep a race rotating. Modular radial air bearings also have the advantage of being kinematically correct. They are consistent with exact constraint theory; so three radial air bearings can be used to constrain an axis of rotation for the same reason that a three-legged stool cannot rock. Exact force paths are also known through the bearings and into the structure, simplifying FEA analysis with neat, closed-end equations. Another advantage is that a higher degree of precision is easier to achieve. Using radial air bearings – with only one rotating element – virtually eliminates asynchronous error and reduces synchronous errors by a factor of 10. This makes radial air bearings ideal for large machine tool worktables or spindles. Configurations to cover a wide array of applications New Way radial air bearings are available in four basic configurations: Concave configurations are for use on the Outside Diameter (OD) of a rotating body; Convex configurations may be used on the Inside Diameter (ID). The radius for either of these basic configurations may then be cut by the length of the bearing or by its width. This new line is available for shafts as small as 25 mm and for rings as large as 3 meters. Larger diameters can also be accommodated, as custom orders. Technically, New Way Radial Air Bearings are not a standard product. Because each radius must be precisely machined to the dimension and tolerance requirements of the application at hand, they cannot be ‘stocked.’ They are, however, as close to a stock item as a ‘Designed-to-Order’ component can be. New Way does stock the ten standard-size bearing housings with which they are manufactured. These housings range in size from 12x24mm to 150x300mm, for a wide variety of application scales. Although they are not quite available ‘off the shelf,’ the delivery timeframe for these precision components is just eight weeks, with incremental shipping timeline improvement projected as quantities-of-scale build. The bearings themselves mount on spherical ball gimbal seats, so they are self-aligning to the rotor. Because the gimbals are on threaded studs, they are adjustable, so no precision is required on the stator to mount the bearing, just a threaded hole for the studs. This is in contrast to the 360° flat mounting surface with many tapped holes required by a large roller bearing or slewing ring. The Advantages of Porous Media New Way's modular radial air bearing products are inexpensive and easy to use. They operate quite differently from conventional orifice air bearings. New Way’s Porous Media® Technology distributes air evenly through millions of sub-micron sized holes across the bearing surface. More consistent air pressure distribution provides for superior performance. These porous media radial air bearings are also very robust compared with conventional air bearings, and can withstand repeated crashes (loss of air pressure) even at high speeds. The porous carbon New way uses is a sintered material and will not ‘pick up or spall,’ even on a soft material like aluminum. Further, because the carbon is itself a bearing material, New Way radial air bearings will still function effectively even after severe damage. Porous media technology has been in use for more than 20 years in precision applications such as coordinate measuring machines, precision machine tools, and test equipment. Because they are a non-contact solution – eliminating friction, wear and the need for lubrication – New Way radial air bearings are ideal even for applications in clean rooms or clean manufacturing environments.
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