An air bearing, also known as a gas bearing, uses compressed air or another gas to form a supporting film between moving surfaces. Unlike rolling element and sliding bearings, an air bearing supports moving components through a thin gas film, keeping the mating surfaces apart during normal operation. This reduces friction, mechanical wear, and vibration caused by solid contact.
Air bearings are used in semiconductor manufacturing, precision measurement, and high-speed spindle systems because of their low friction, high motion accuracy, and clean operation. However, their load capacity, air supply quality, and system design also require careful consideration. The appropriate bearing type must be selected according to the actual operating conditions.
Main Advantages of Air Bearings
Low Friction and Minimal Mechanical Wear
Air bearings support moving components through a thin film of gas. During normal operation, the mating surfaces remain separated, significantly reducing friction and mechanical wear.
Unlike conventional rolling element bearings, air bearings do not have balls or rollers repeatedly passing through contact areas. When the air film is properly established, both starting friction and running friction are very low. This helps reduce drive power losses and particle generation.
Because there is little direct mechanical contact during operation, air bearings experience minimal wear and generally require less bearing replacement and maintenance. However, a stable air supply must be maintained, and the air filtration system and guide surfaces still require periodic inspection.
High Motion Accuracy and Smooth Operation
Air bearings are suitable for equipment requiring high linear and rotational accuracy. The continuous gas film provides support without the periodic mechanical impacts associated with rolling elements and can eliminate mechanical backlash in properly designed systems.
Their main characteristics include:
Low friction and minimal stick-slip: Non-contact support reduces static friction and stick-slip effects during movement, allowing smoother motion response.
High motion accuracy: With appropriate design and precision machining, air bearings can achieve good straightness, rotational accuracy, and repeatability.
Low vibration: The gas film reduces mechanical impacts between rolling elements and raceways, helping minimize vibration and noise during operation.
Surface error averaging: Under suitable conditions, the gas film can average small surface irregularities along the guideway, improving the straightness of motion.
These characteristics make air bearings suitable for lithography equipment, wafer processing systems, coordinate measuring machines, and other ultra-precision motion mechanisms. Actual motion accuracy still depends on guideway machining quality, installation structure, and air film stiffness. It cannot be determined by bearing type alone.
Suitability for High-Speed Operation
Air bearings have low frictional resistance and generate relatively little frictional heat during operation. This makes them suitable for certain high-speed rotating applications.
For example, some high-speed grinding and micromachining spindles use air bearings and operate at tens of thousands of revolutions per minute. Specialized high-speed spindles can reach several hundred thousand rpm. The achievable speed depends on bearing design, rotor dynamics, air film stability, and the associated drive system.
Lower frictional heat helps control spindle temperature rise and reduces the effect of thermal deformation on machining accuracy.
Oil-Free Operation for Clean Environments
Air bearings use air or another gas as the lubricating medium. Under normal operating conditions, they do not require lubricating oil or grease between the bearing surfaces.
This reduces the risk of oil contamination and lubricant particles affecting products or the surrounding environment. Air bearings are therefore suitable for semiconductor manufacturing, flat panel display production, precision optical machining, and certain biomedical equipment.
However, the absence of grease lubrication does not mean that the entire machine is free from possible contamination sources. The air supply system and surrounding mechanical components still require appropriate filtration and contamination control.
Thermal Stability and Temperature Adaptability
Compared with conventional bearings that transfer loads through solid contact, air bearings generate less frictional heat. This helps reduce thermal effects on precision motion systems.
Some specialized designs can operate over a wide temperature range, depending on the materials, sealing arrangements, and air supply conditions. The temperatures of -40°C and +200°C mentioned in the original material can be considered examples for specific applications, but they are not universal operating limits for all air bearings. Actual operating conditions must be checked against the temperature limits of the bearing materials, gas supply equipment, and associated components.
Structural Characteristics and Types of Air Bearings
Air bearings support moving components through a gas film formed within a very small clearance. The clearance is typically several micrometers to several tens of micrometers.
According to how the supporting gas pressure is generated, air bearings are generally divided into two types: aerodynamic bearings and aerostatic bearings.
Aerodynamic Bearings
Aerodynamic bearings generate supporting pressure through the relative movement of two surfaces. As the surfaces move, gas is drawn into a wedge-shaped gap, creating hydrodynamic pressure that supports the load.
Some designs incorporate shallow spiral grooves on the journal or bearing surface. These grooves help move gas through the bearing clearance and improve load-carrying capacity.
Aerodynamic bearings do not rely on an external pressurized gas supply to generate their primary supporting film. However, they require sufficient relative motion to develop supporting pressure. Their load-carrying capability during low-speed operation, startup, and shutdown differs from that at normal operating speed. The possibility of surface contact and wear during these stages must therefore be considered during design.
Aerodynamic bearings are mainly used in high-speed, relatively light-load applications, such as certain high-speed dental handpieces and refrigeration centrifuges.
Aerostatic Bearings
Aerostatic bearings use an external gas supply to provide pressurized air. The compressed air passes through supply holes, restrictors, or porous materials into the bearing clearance, forming a supporting film between the mating surfaces.
Since the supporting film is generated by external pressure, aerostatic bearings can support loads at low speeds and even at zero rotational speed. They are suitable for equipment requiring precise positioning and low-speed motion.
The main components include:
Air supply system: Provides a continuous and stable supply of compressed air to the bearing.
Restrictor structure: Controls gas flow and pressure distribution through orifices, capillaries, or porous materials.
Bearing clearance: Forms the space in which the supporting gas film is established. Its dimensions affect load capacity and film stiffness.
Some aerostatic bearings use shallow recesses or designs without deep air pockets. These arrangements can reduce the response time of the gas film and help prevent instability such as pneumatic hammer.
The 0.6 MPa pressure mentioned in the original material can be used as a reference for certain designs, but it is not a universal pressure limit for all aerostatic bearings. The actual supply pressure must be determined according to bearing dimensions, restrictor design, load conditions, and manufacturer specifications.
Aerostatic bearings are commonly considered for applications such as lithography stages, precision grinding spindles, and high-accuracy measuring platforms.
Main Applications of Air Bearings
Air bearings are mainly used in equipment with demanding requirements for motion accuracy, operating speed, and environmental cleanliness.
Semiconductor Manufacturing Equipment
Lithography machines, wafer inspection equipment, and wafer processing stages require precise movement and stable positioning. Air bearings reduce mechanical friction, particle generation, and vibration, helping maintain the motion accuracy of the worktable.
Precision Measuring Instruments
Coordinate measuring machines (CMMs), roundness measuring instruments, and other precision measurement equipment require smooth and repeatable movement. The low friction and absence of mechanical backlash in air bearing systems help reduce motion-related errors during measurement.
High-Speed Spindle Systems
Precision grinding machines, micromachining equipment, and high-speed milling spindles can use air bearings for support. With an appropriate bearing design and air supply, these systems can achieve high rotational speeds while reducing frictional heat and operating vibration.
Aerospace and Precision Testing Equipment
Air bearings can be used in certain high-precision inertial instruments, gyroscope testing equipment, and precision motion mechanisms. For specialized equipment such as flight simulator motion platforms and radar antenna pointing systems, suitability must be evaluated according to load, stiffness, travel range, and air supply conditions. These should not be regarded as standard configurations for all such equipment.
Clean Manufacturing Environments
Flat panel display manufacturing, semiconductor production, and certain biomedical applications have strict requirements for controlling oil contamination and airborne particles. Since air bearings do not require grease lubrication and generate relatively few particles during normal operation, they can be considered as one of the supporting solutions for these environments. They are not the only available option.
Main Limitations of Air Bearings
Although air bearings offer high motion accuracy and low friction, several limitations must be considered during equipment design and selection.
Load capacity depends on bearing dimensions: Load capacity is determined by the bearing area, supply pressure, air film clearance, and restrictor design. Applications requiring high loads within limited installation space need specific load capacity and stiffness calculations.
Strict air supply requirements: Aerostatic bearings require a continuous supply of stable, clean, and dry compressed air. The supply system generally needs filtration, drying, pressure regulation, and pressure monitoring to prevent moisture, oil, and particles from entering the bearing clearance.
Higher initial manufacturing costs: Air bearing guide surfaces, restrictor holes, and mating clearances often require high machining accuracy. Some designs also use specialized materials such as ceramics, increasing manufacturing complexity and cost.
Complex design and stability control: Air film pressure distribution and stiffness are affected by supply pressure, clearance dimensions, and load variations. Incorrect design may cause instability such as pneumatic hammer, which must be controlled through appropriate restrictor design and dynamic analysis.
Sensitivity to air supply interruptions: For externally pressurized aerostatic bearings, a drop in pressure or complete loss of air supply reduces the supporting capacity of the gas film and may cause contact between moving surfaces. Pressure monitoring and appropriate protection measures are therefore required.
Custom Machining of Precision Components for Air Bearing Systems
Air bearing systems contain bearing housings, precision shafts, mounting brackets, air supply connectors, and other mechanical components. Their machining requirements depend on the air film clearance, mounting fits, structural stiffness, and customer drawings. Hansheng Automation provides custom precision machining based on customer drawings and accepts both single-piece and small-batch orders.
In addition to components for air bearing systems, our precision machining services also cover parts for yachts and RC racing cars, as well as components for tobacco packaging machinery and filling equipment. Parts are manufactured according to the structural requirements and drawings provided for each project.
