The Ultimate Guide to Air Bearings: What Makes Them Stand Out

What Is An Air Bearing

What is air bearing

Bearing is a concept that most people are familiar with. The rolling bearing, which is commonly used, is probably the most recognizable. It is a crucial component of modern mechanical equipment. But what exactly is an air bearing?

The idea of using gas as a lubricant was first proposed by the Frenchman G.A. Ian in 1854. It wasn’t until 1896 that the first air bearing was introduced.

An air bearing is a type of sliding bearing that uses gas as a lubricant. The most common gas used for this purpose is air, but other gases such as nitrogen, argon, hydrogen, helium, or carbon dioxide can be used as required. Gas is often used as a lubricant in compressors, expanders, and circulators.

An air bearing operates by using the pressure of an air film to support the load between the sliding surfaces of the bearing. During operation, the sliding surfaces are completely separated by the air film. Air bearings belong to the category of fluid sliding bearings and they use fluid lubrication, with air as the lubricating medium.

Air bearing

According to the mechanism of pressure air film formation, air bearings are categorized into two types: aerodynamic bearings and aerostatic bearings.

The pressure air film in aerodynamic bearings is generated by the movement of the sliding pair, which draws air into the convergence area between the surfaces. This results in a roughly wedge-shaped air film, as depicted in Figure 1. Aerodynamic bearings are referred to as “self-acting bearings” because they don’t require an external air supply.

In contrast, the pressure air film in aerostatic bearings is created by introducing compressed air from an external source into the sliding pair surface through a restrictor, as shown in Figure 2. It is important to note that aerostatic bearings require a clean external air source.

working principle of aerodynamic bearing

Fig. 1 working principle of aerodynamic bearing

working principle of aerostatic bearing

Fig. 2 working principle of aerostatic bearing

Characteristics of air bearing

① Low Friction

Gas has a much lower viscosity compared to liquids, with the viscosity of air being only one fifth that of No. 10 mechanical oil at room temperature. The friction of a bearing is directly proportional to its viscosity, making the friction of a gas bearing lower than that of a liquid-lubricated bearing.

② Wide Speed Range

Gas bearings have low friction and generate low heat, even at high speeds of up to 50,000 RPM, with a temperature rise of only 20 to 30 degrees Celsius. Aerostatic bearings can also be used at very low speeds or even at zero speed.

③ Wide Temperature Range

Gas can remain a gas over a wide range of temperatures and its viscosity is relatively unaffected by temperature changes. For example, when the temperature increases from 20 to 100 degrees Celsius, the viscosity of air increases by only 23%. As a result, gas bearings can be used in a temperature range of -265 to 1650 degrees Celsius.

④ Low Load-Bearing Capacity

The load-bearing capacity of hydrodynamic bearings is directly proportional to its viscosity. The load-bearing capacity of a gas hydrodynamic bearing is only a few thousandths of that of a liquid hydrodynamic bearing of the same size. The compressibility of gas also limits the load-bearing capacity of a gas hydrodynamic bearing, with a typical maximum load per unit projected area of 0.36 MPa.

⑤ High Machining Precision

To increase the load-bearing capacity and gas film stiffness of gas bearings, a smaller bearing clearance (less than 0.015mm) is usually used compared to liquid lubricated bearings. This requires a corresponding improvement in the precision of the components.

Characteristics of air bearing

Application of air bearing

Air bearings are a new type of bearing that rely on aeroelastic potential energy for support. Unlike traditional bearings, air bearings use air as the only lubricant and are ideal for applications where no pollution is allowed.

In air bearings, the traditional ball bearing is replaced by an air cushion. One well-known example of air bearings in action is in hovercrafts. Huge fans blow air under the hovercraft, which is prevented from escaping by an elastic rubber “skirt.” The resulting high air pressure supports the weight of the hull, causing the hovercraft to float on the air cushion.

Gas bearings have been increasingly used and studied since the 1950s. Today, they are used in a variety of applications, including textile machinery, cable machinery, instrument machine tools, gyroscopes, high-speed centrifuges, dental drills, low-temperature refrigerators, hydrogen expanders, and high-temperature gas circulators.

Don't forget, sharing is caring! : )


Founder of MachineMFG

As the founder of MachineMFG, I have dedicated over a decade of my career to the metalworking industry. My extensive experience has allowed me to become an expert in the fields of sheet metal fabrication, machining, mechanical engineering, and machine tools for metals. I am constantly thinking, reading, and writing about these subjects, constantly striving to stay at the forefront of my field. Let my knowledge and expertise be an asset to your business.

Up Next

Mastering CAD/CAM: Essential Technologies Explained

Basic Concepts of Computer-Aided Design and Computer-Aided Manufacturing Computer-aided design and computer-aided manufacturing (CAD/CAM) is a comprehensive and technically complex system engineering discipline that incorporates diverse fields such as computer [...]

Virtual Manufacturing Explained: Concepts & Principles

Concept of Virtual Manufacturing Virtual Manufacturing (VM) is the fundamental realization of the actual manufacturing process on a computer. It utilizes computer simulation and virtual reality technologies, supported by high-performance [...]

Understanding Flexible Manufacturing Systems: A Guide

A Flexible Manufacturing System (FMS) typically employs principles of systems engineering and group technology. It connects Computer Numerical Control (CNC) machine tools (processing centers), coordinate measuring machines, material transport systems, [...]

Exploring 4 Cutting-Edge Nanofabrication Techniques

Just as manufacturing technology plays a crucial role in various fields today, nanofabrication technology holds a key position in the realms of nanotechnology. Nanofabrication technology encompasses numerous methods including mechanical [...]

Ultra-Precision Machining: Types and Techniques

Ultra-precision machining refers to precision manufacturing processes that achieve extremely high levels of accuracy and surface quality. Its definition is relative, changing with technological advancements. Currently, this technique can achieve [...]

Exploring High-Speed Cutting: Tech Overview & Application

Cutting machining remains the most prominent method of mechanical processing, holding a significant role in mechanical manufacturing. With the advancement of manufacturing technology, cutting machining technology underwent substantial progress towards [...]

Top 7 New Engineering Materials: What You Need to Know

Advanced materials refer to those recently researched or under development that possess exceptional performance and special functionalities. These materials are of paramount significance to the advancement of science and technology, [...]

Metal Expansion Methods: A Comprehensive Guide

Bulge forming is suitable for various types of blanks, such as deep-drawn cups, cut tubes, and rolled conical weldments. Classification by bulge forming medium Bulge forming methods can be categorized [...]
Take your business to the next level
Subscribe to our newsletter
The latest news, articles, and resources, sent to your inbox weekly.
© 2024. All rights reserved.

Contact Us

You will get our reply within 24 hours.