When most people talk about bearings, they usually think of ball bearings. In this type of bearing, the fixed and moving surfaces are separated by a series of lubricating balls. These balls travel along special tracks or raceways. Perhaps the most common application is a shaft that rotates within a fixed hub, such as the drive shaft on the front wheel of a car or bicycle.
In air bearings, the ball is replaced by an air cushion. Perhaps one of the most familiar applications of air bearings is for hovercraft.
Huge fans blow air under the hovercraft, stopping it from escaping through elastic rubber "skirts". The high air pressure created under the hovercraft supports the weight of the hull, thus allowing it to float on the air cushion. The huge cushion of air not only supports the weight of the ship, but also acts as a soft spring to keep it afloat smoothly over rough land surfaces or water.
The same principle can be applied to rotary shaft bearings. High pressure air is injected into the gap between the rotating shaft and the fixed bearing. The gap is very small (about 0.01 mm), allowing the air pressure in the gap to remain constant. Moreover, this narrow gap also significantly reduces the "elasticity" of the air cushion, allowing the shaft to be fixed very precisely, i.e., with only low dynamic eccentricity. The low friction allows the shaft to rotate freely, and the air pressure ensures that the shaft does not come into contact with the fixed bearing surface.
The most commonly used gas medium for air bearings is air, and it can also be nitrogen, hydrogen, helium, carbon dioxide and so on according to different needs. Nowadays, in some advanced mechanical equipment, bearings with higher accuracy, longer service life and greater bearing capacity are needed. Air bearings can meet such requirements.
Why use air bearings?
advantages
Non - contact bearing, low friction
Wide range of speed operation capability: from 0rpm to more than 350000rpm
These spindles feature high rigidity and high load capacity, can be liquid-cooled, and produce only low dynamic eccentricity.
High rotation accuracy, low spindle movement error
Long service life due to non-contact surface
Low heat
disadvantages
High geometric accuracy is required in the manufacturing process
A clean and dry pressurized air supply is required
The biggest disadvantage of air bearings is probably that they have high precision requirements and difficult production technology. This is why bearings that can achieve no friction and no wear in the design load are not popular.
TECHNOLOGY
TECHNOLOGY
