Is there a bearing that will not produce friction and wear as long as it does not exceed its design load?
The answer is yes, air bearings.
Today, let’s talk about what air bearings are and why air bearings are used.
What is air bearing?
When most people talk about bearings, they usually think of ball bearings.
In such bearings, the fixed and moving surfaces are isolated by a series of lubricated balls.
These balls move along special tracks or raceways.
Perhaps the most common application is a shaft rotating in a fixed hub, such as a 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 well-known applications of air bearings is hovercraft.
Huge fans blow air under the hovercraft and prevent the escape of air through elastic rubber “skirt”.
The high air pressure generated under the hovercraft can support the weight of the hull, so it floats on the air cushion.
The huge air cushion not only supports the weight of the hull, but also acts as a soft spring to make the hull float smoothly on the rough land surface or water surface.
The same principle can be applied to shaft bearings.
Inject high-pressure air into the gap between the rotating shaft and the fixed bearing.
The gap is very small (about 0.01 mm) so that the air pressure in the gap remains constant.
Moreover, this narrow gap also significantly reduces the “elasticity” of the air cushion, so that the shaft is fixed very accurately, that is, only low dynamic eccentricity can be generated.
Due to the low friction, the shaft can rotate freely, and the air pressure can ensure that the rotating shaft does not contact the surface of the fixed bearing.
The most commonly used gas medium of air bearing is air.
According to different needs, it can also be nitrogen, hydrogen, helium, carbon dioxide and so on.
Nowadays, in some advanced mechanical equipment, bearings with higher precision, longer service life and greater bearing capacity are needed, and air bearings can meet such requirements.
Why use air bearings?
- Non contact bearing, low friction;
- Wide range of speed operation capacity: from 0rmp to 350000rpm or above;
- These spindles have unique high rigidity and high load capacity, can be cooled by liquid, and only produce low dynamic eccentricity;
- High rotation accuracy and low spindle movement error;
- Long service life due to non-contact surface;
- Low heat production.
- High geometric accuracy is required in the manufacturing process;
- Clean and dry pressurized air supply is required.
The biggest disadvantage of air bearing is that it has high requirements for precision and difficult production technology.
This is why this kind of bearing that can achieve no friction and wear within the design load is not popularized.