New Way® Air Bearings Extends Line of Flat Rectangular Air Bearings To Accommodate New Profiles and Applications
Aston, Pennsylvania, USA, June 26, 2008 — New Way Air Bearings has expanded its line of flat, rectangular porous media air bearings. Previously, this core product line – New Way’s original product, in fact – consisted of four sizes. With the addition of seven new sizes – three larger bearings (up to 150mm x 300mm) and four smaller bearings (down to 12mm x 24mm) – there are now a total of 11 New Way rectangular air bearings altogether.
This broader range of rectangular air bearings will enable engineers to address a number of changing needs. The first is the increasing size of Flat Panel Display glass. FPD manufacturers now use gantries that must span several meters. These moving gantries are often made of granite, and can be much heavier. With this line extension, New Way now offers rectangular air bearings with the load capacity to handle these new large gantries – the fastest-growing segment of the stage market.
Second, recognizing the benefits of air bearings, engineers had been trying to use multiple bearings (per side) to support a single heavier gantry. This made adjustments more difficult, because when load is shifted to one of the bearings, load is reduced on a neighboring bearing. To be kinematically correct, three points define a plane – or at most four bearings (two on each side) define two lines on a plane. Attempts to define a plane with eight bearings are fraught with issues, as it is difficult to adjust all of those bearings to carry equal load. New Way recognized the need to offer larger bearings so that engineers could follow good design principles when using our air bearings in their equipment.
“New Way does offer large flat round air bearings,” noted New Way Chairman and CTO Drew Devitt. “Our largest standard product is 200mm in diameter, and we continue to receive requests for even larger ones. And because many machine builders use large granite surface plates as a reference base, they often have real estate available to run these wide (round) bearings.”
“But round bearings take up a lot of machine-width real estate,” Devitt continued, “And extra width can mean extra cost for the builder. Our three new large rectangular bearings enable us to offer more load capacity in a smaller-width area. It’s a more efficient solution for the space.”
New Way also responded to the development of the micro – and more recently the nano – industries, by engineering four smaller rectangular air bearings ideal for smaller profiles.
“Our new smaller rectangular air bearings provide a significant advantage over traditional roller-bearings for micromachining or nano-positioning applications,” said Devitt. “With contact bearings the friction becomes too high a percentage of the total force. But with New Way Porous Media TechnologyTM, there is no contact, so there is no friction.”
New Way engineered these four new smaller rectangular air bearings to be used anywhere engineers are trying to build small, lightweight machines with high-precision requirements; for example, biomedical and pharmaceutical applications.
With a complete line of 11 flat rectangular air bearings, New Way now enables customers to handle applications from the micro to the macro with precision – in fact, with all of the advantages that air bearings typically provide.
The Advantages of Porous Media
New Way’s modular air bearing products are inexpensive, robust, and easy to use. Unlike conventional orifice air bearings, New Way Porous Media® Technology controls the airflow across the entire bearing surface through millions of sub-micron-sized holes in the material. More consistent air pressure distribution provides for superior performance.
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. One advantage is that the bearing does not damage the surface it runs on should the air supply be inadvertently lost.
Further, because carbon is itself inherently a bearing surface, the New Way air bearings still fly even after severe surface damage. Having no friction or wear problems, and with no lubrication requirements, air bearings are ideal for applications in abrasive, dry and demanding environments that wreak havoc on traditional contact bearings.
For more sophisticated applications like the FPD marketplace, New Way® Air Bearings are approved for use in Class-10 Clean Rooms, where the constant flow of air helps keep the dust and particles found even in that environment away from the bearing surface.
New Way Rectangular Air Bearing Product Line Extension
Part Number Size Status
S121201 12mm x 24mm New Small
S121501 15mm x 30mm New Small
S122001 20mm x 40mm New Small
S122501 25mm x 50mm New Small
S124001 40mm x 50mm Original
S124002 40mm x 80mm Original
S125001 50mm x 100mm Original
S127501 75mm x 150mm Original
S1210001 100mm x 200mm New Large
S1212501 125mm x 250mm New Large
S1215001 150mm x 300mm New Large
A common misconception about air bearings is that they do not have the required stiffness for precision applications. However, a 6″ diameter bearing running at 60psi actually has a stiffness greater than 2,000,000 lb/in with a load of 1,000 lbs. Put another way, that’s less than one-half of a millionth of an inch deflection per pound of additional force. By testing a bearing through a range of loads and measuring the change in air gap, a stiffness plot can be created. This plot will show that the slope is not linear and as the film gets thinner the stiffness gets higher.
The Benefits of Air Bearings
Because of zero static friction, infinite resolution and very high repeatability are possible.
Non-contact means virtually zero wear resulting in consistent machine performance and low particle generation.
Rolling element bearings are directly influenced by surface finish and irregularities on the guide. Being non-contact air bearings average these errors.
Silent and smooth operation
Re-circulating rollers or balls create noise and vibration as hard elements become loaded and unloaded and change direction in return tubes. This is especially noticeable in the resolution of scanners.
Being fluid film bearings, air bearings have a squeeze film damping effect resulting in higher dynamic stiffness and better controllability.
Air bearings do not use oil lubrication, eliminating the problems associated with oil. In dusty environments (dry machining) ways are dry and bearings are self-cleaning because positive air pressure pushes dust away. In contrast, oil lubrication becomes a lapping slurry.
High speeds – high acceleration. No balls or rollers to slip at high acceleration.
Engineering With the Right Aspect Ratio
Although New Way also manufactures flat round air bearings, the company engineered this complete line of rectangular air bearings to optimize the bearing area for a given guide-width. When dimensioning this product line, New Way engineers determined that it would be ideal to create a two-to-one aspect ratio. This configuration maximizes the amount of load capacity possible for a particular guide-surface width without the need for the bearings to become inordinately thick.
Increasing the ratio to three times the width would create significant bearing deflection issues because the loading point in the back is in the center, and the load is evenly distributed across the face via the air film. The load from the air film, especially around the edge of the bearing, makes for a significant cantilever. So a bearing with a three-to-one dimensional ratio would need to be substantially thicker in order to avoid deflections.
Our bearings operate nominally near five-to-ten microns of ‘air gap.’ Air bearings will bend microscopically as customers apply load to the center point, even when there is an equal distribution of pressure beneath. If the bearing bends more than 5 microns it may ground on the guide surface. As bearings get to be three times their width, they either have to be very thick or they are going to bend and touch down.
But air distribution is not homogeneous even in the best porous media air bearings (ours). Typically, pressure distribution can be illustrated as a bell curve. As the aspect ratio of the bearing grows beyond 2-to-1, the further from rectangular ‘symmetry,’ the more the bell curve for pressure distribution erodes at the outer reaches. This is the case due to the deflection referenced above, because resistance to flow is a cubed function of the gap, so the resulting bend reduces pressure most significantly near the edges of the bearing.
So the 2-to-1 aspect ratio is a sort of fundamental ratio in nature, and it also works out very well for New Way because we are able to maximize the amount of carrying capacity for a given width of air bearing without too high a price in the total thickness of the bearing.
If you examine our Flat Rectangular Air Bearings you will see that they are a little thicker than our Flat Round Air Bearings. That is because the distance from the center of the bearing to the edge of the bearing can be greater in the rectangular shape than in the round shape. This added thickness helps to prevent deflection when these rectangular bearings are utilized within recommended operating parameters.
About New Way Air Bearings
New Way® Air Bearings, Inc. is the market leader in the design and manufacture of modular air bearings and the recognized provider of porous media air bearing solutions. Founded in 1994, the company is located in Aston, Pennsylvania, USA, 15 minutes from Philadelphia International Airport.
In August, 2007, New Way Air Bearings was named to Inc. Magazine’s list of the 5,000 fastest-growing, private companies in America for 2007. The company ranked as No. 2,294 on the list, which measured companies by revenue growth from 2003 to 2006. In November of 2007, The Greater Philadelphia Chamber of Commerce named New Way recipient of its Technological Excellence of the Year Award for 2008.
Visit New Way Air Bearings at www.newwayairbearings.com. This web site includes specifications for the company’s full product range, design and installation guides, mounting hardware, air specifications, technical support, and a full range of accessories.