Q: What are air bearings made from?
A: Most common is aluminum with a coating called hard-coat. PI also use stainless steel and nickel plate steel. Granite is often used as the bearing support surface or structure.
Q: What happens if the bearing moves with the air off?
A: Forcing an air bearing to move with no air can damage the bearing, although it will often be ok. The mating surfaces are quite durable, but contaminants can cause scratches.
Q: Do air bearings wear out?
A: The air bearing life is unlimited, assuming the following:
- The bearing is kept clean and the surfaces undamaged
- The air supply is kept clean, dry, and oil-free
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.
Q: Can an air bearing stage work in a vertical (lift) application?
A: Yes. The problem with vertical applications is how you support the gravity load. In a typical ballscrew-driven stage, the mechanical advantage of the screw can support the load with minimal load on the motor. However, in a direct-drive system, motors will overhead in this case. The solution is to add a pneumatic counterbalance mechanism to support the gravity load. PI has built many such systems. Counterbalances to add some cost and complexity to the system and require extra space.