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Air Bearings vs Contact Bearings

Air Bearings vs Contact Bearings

How Air Bearings Outlast and Outperform the Competition

New Way Air Bearings® has long been a proponent of Frictionless Motion® across a wide range of industries and applications. And here, we’d like to take the time to cover the true breadth of benefits provided by frictionless, Porous Media™ air bearings.

The air bearing itself is no recent invention. Our newly updated technical report discusses the history of the air bearing, all the way back to its earliest iterations—invented by Robert Wills and Albert Kingsbury in England, and later refined in America by George Westinghouse. Each saw the potential for both linear and rotary applications of this new invention, and we’re proud to say that their pioneering intuition was right on target.

Speed

When considering the use of bearings—roller, ball, or journal—for your high speed applications, your first thought might naturally be whether your chosen bearing itself will impose a speed limit on your process. With traditional bearings, this fear isn’t unfounded. Contact bearings have mechanical limitations on speed. Often surrounding functions of inner diameter, outer diameter and bore. Additionally, oil-lubricated bearings are a necessity for increasing speed, as the viscous shear enables higher rpm speeds.

While all of these innovations are admirable, they still don’t compare to the kinematic efficiency and speed achieved by air bearings. In our tests, we’ve shown that air bearings can produce speeds up to 10 times that of a comparable contact bearing system, often in excess of 30-50 m/s. Since a system built on Externally Pressurized Porous Media has a frictional coefficient of zero, there’s almost no upper limit on the speeds our products can achieve.

Precision and Straightness

For virtually all bearing applications, precision positioning and straightness are of the utmost importance. And, New Way has a long history of our air bearing products revolutionizing precision applications where contact bearing systems simply don’t make the cut. No matter how precisely the bearings are made or the track is cut, roller and ball bearings present obstacles to the implementation of repeated precise, straight motion.

As the individual bearings elements move and pick up speed, they accumulate momentum, which causes overshoot. This overshoot eventually compounds into full blown hysteresis, making truly precise motion an impossibility.

The work of MIT’s Michael Chiu touched on this. Through his masters thesis, Low-Cost, Highly Damped, Precision Linear Motion, Using Porous Carbon Air Bearings and Epoxy Replication (covered in detail in technical report three), Chiu demonstrated the superiority of an air bearing system vs. a contact bearing one, focused primarily on precision of motion and straightness.

Force vs Displacement Diagram showing the Hysteresis of Roller Bearing Systems

The above graph demonstrates the sizable hysteresis of a roller bearing system, thoroughly disqualifying them from such precision fields as semiconductor and wafer inspection, where New Way air bearings provided the nanoscale accuracy the industry demands.

What gives air bearings their precision positioning capability also allows for incredibly straight motion. As shown in our technology comparison video, roller or ball bearings generate straightness deviations as a result of grooves, pitting, or other geometric imperfection in the bearing’s surfaces. On the other hand, air bearings produce the exact opposite effect, averaging out any surface imperfections across the pad of air, creating an even flatter motion curve, as Chiu’s work once again shows.

Straightness vs. position diagram of Porous Carbon and Ball Bearing Systems.

Durability and Safety

Air Bearings don’t just provide the fastest or smoothest or most precise product; they also represent the safest and most durable.

All contact bearings may as well come with an expiration date; the only question is when they’ll go, and how much damage they do when they fail. The Torrington Company lists no less than several dozen, distinct failure modes which can affect bearings, from spalling and flaking on individual balls and rollers to lubricant failure and particle infiltration in journal bearings.

If you’re performing preventative maintenance, then all you lose is production downtime, but if a contact bearing system fails, then expect damage. Not just to your guide system, but potentially to your product as well.

Air Bearing products sidestep all these concerns with their unique operation. Because air bearings have no dynamic components themselves and operate on a micrometer-thin layer of air, there are no components to wear down, and thus none to replace. Furthermore, should the power go out, an air bearing system will slowly depressurize, settling the soft graphite against the guide surface, and preserving all your assembly’s components.

Even in situations where particle infiltration is likely, so long as your air supply is filtered, there’s no obstacle to the performance of porous media. In fact, our new products are designed for exactly this type of operating environment. The New-Seal™ is a combination bearing and seal, enabling rotational motion while sealing a shaft against particle or fluid infiltration up to 35 PSi.

Cleanroom Compatibility

With the advent of miniaturized manufacturing and more precise machining techniques, cleanroom conditions have rapidly become a necessity, stretching beyond electronics manufacturing and into spacecraft production, nanotechnology and even 3d printing. Almost all forms of contact bearings are inherently unsuited for cleanroom conditions, and those which are used are out of necessity and not desirability.

Any form of lubricated bearing runs the risk of outgassing into the environment, or, generating metal particulates which can similarly be ejected into the cleanroom.

Conversely, the nature of our porous media air bearings makes them a unique match for the demanding needs of a cleanroom environment, filtering out particulates before they can ever pass through the bearing’s surface. In house testing by New Way confirmed that all of our air bearing products are ISO 146-44 Class 3 compliant, producing only single digit numbers of 0.1 micron sized particles in an enclosed testing area. During this test, only 3 particles at a time were ever detected, making a strong case for the usage of air bearings in the most stringent, ISO Class 1 environs.

Contact Us

If you’d like to learn more about the advantages of porous media air bearings or already have an application in mind, please contact us so New Way can best serve your needs!

Contact us today for a complimentary consultation