PIglide Air Bearing Technology

Typical specifications are:

Linear: Straightness/Flatness 0.1µm/25mm, Pitch/Yaw 0.5 arc-sec/25mm

Rotary: Radial/Axial Runout 0.1µm, Wobble < 1 arc-sec

The total error motion over full travel is usually specified in “microns TIR.” TIR means Total Indicator Reading. TIR is specifying the peak-to-peak measurement of error motion. We do not assume symmetry about a zero reference. Air bearing stages can typically achieve better than 1 µm flatness and straightness TIR for every 200 mm of travel.

The lack of mechanical bearing elements means there is nothing to get in the way of smooth, controlled velocity (stability to better than 0.01 %). Experiments and processes like inertial sensor testing, tomography, wafer scanning, and surface profiling require continuous motion at a tightly controlled speeds are best served by air bearing systems.

A direct-drive motor and high-resolution encoder can position a moving carriage supported by an air bearing to within nanometers in a linear application or within tenths of arc-seconds in rotational applications. The lack of friction and mechanical contact means there is minimal vibration, hysteresis or reversal error, making it highly repeatable and ideal for many inspection and manufacturing operations. Stiction is virtually eliminated, improving resolution capabilities and reducing in-position „hunting“ (limit cycling) and position repeatability can be obtained within a few fundamental encoder counts. Similar precision can be obtained by piezo flexure guided stages, however over much smaller travel ranges. Magnetic levitation is another option.

The air bearing life is unlimited, assuming the following:

As long as nothing damages the bearing it will run forever. The maintenance of the air filters and the air compressor is the important thing. After that, the life-limiting items are usually the flex cables, which will wear out and break after too many cycles (many millions). Motor coils and encoders usually only fail if they have been damaged, or have a short, or overheat.

Air bearings can be used universally with very few limitations:

While it is not impossible to operate an air bearing in a vacuum, it is challenging. Vacuum applications should generally be avoided and instead use mechanical bearing, mag-lev, or flexure systems.

Air bearings are generally used in clean environments. Applications where heavy amounts of dust, dirt, debris, and fluids are present should generally be avoided.

Air bearings require a continuous supply of clean compressed air or nitrogen. If the application does not allow for such a supply to be present, an air bearing cannot be used.