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Fluid film bearings offer a number of advantages over mechanical bearings. First, because there is no contact, [air bearings] do not suffer from wear or heat generation due to friction. They also exhibit no starting or running friction, even under their highest design loading. In addition, the fluid film acts to center and average out small scale errors in the components resulting in motion which can be more accurate than the individual bearing components. Air bearings also offer much higher stiffness than rolling element bearings because the air film fully supports the components, as opposed to balls or rollers which have point or line contact and are therefore limited due to Hertzian contact stiffness.

The repeatability of air bearings far exceeds that of mechanical bearings for the simple reason that they have no contact or wear. Heat generation in mechanical bearings sometimes require "warm up" periods during which there is thermal movement. Also, the mechanical preload on roller bearings can vary with temperature and cause the bearings to operate differently (varying friction for example) and lack repeatability. When working at the highest accuracy levels, these effects can cause mechanical bearings to lose their accuracy from hour to hour, day to day, or month to month. Because the accuracy of our air bearings is built into its solid metal components (made from one type of material for uniform thermal expansion), they can operate for years without any degradation in accuracy. This way, a calibration done one day will "stick". They also can be run at top speed without any need for warm-up time (excluding motor heating effects) and maintain their best accuracy.

Because vacuum is limited to around negative 14 psi (atmospheric pressure) and typical air bearing pressures are 40-80 psi the net effect is still a lifting of the bearing, even when the fag bearing and vacuum areas are equal. Vacuum preload enhances the stiffness and helps to maintain constant air gap, without adding unnecessary moving mass. The main drawbacks to this method are the need for a larger bearing area to accommodate both pressure and vacuum and the requirement of a vacuum source. This method has been used successfully in many applications, especially for flat pads and planar systems which do not lend themselves to other forms of preload.

The third method of preloading is magnetic preload. Magnetic attraction between a magnet on the moving part and a magnetic material on the stationary part of the bearing loads the nachi bearing and adds stiffness.

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NNC 4914