Air bearing is a high-performance non-contact bearing that supports the load with a thin layer of compressed air film. It is a type of "fluid film" bearing. Under typical operating conditions, there is no solid contact between the working surfaces of the air bearing, but they are separated by a stable air film. This structure can not only effectively transmit mechanical loads, but also significantly reduce friction and wear. It is an ideal solution for high-precision, high-speed and clean environments.
1. Working principle
The key to air bearings is the air film they form. This film is formed by introducing pressurized air into the bearing cavity and controlling its uniform discharge from the bearing surface. Depending on the air supply method, air bearings are mainly divided into two types:
Orifice air bearings: air is injected into the bearing surface through multiple tiny holes.
Porous medium air bearings: porous materials are used to evenly infiltrate air to ensure a more stable and uniform pressure distribution.
Regardless of the method used, a stable air gap (usually between 5 and 50 microns) is always maintained inside the bearing cavity to support the moving parts. Although the gas is constantly dissipating, the continuous air supply ensures that the load is always in suspension.
2. Technical Advantages
Compared with traditional rolling bearings or sliding bearings, air bearings have the following significant advantages:
Zero contact, zero friction: Due to the completely contactless operation, air bearings have theoretically zero static friction, which greatly improves the repeatability and dynamic response capabilities.
Ultra-high stability and precision: The floating layer of the air bearing self-adjusts within the micron range, has excellent stability and nanometer-level motion resolution, and is particularly suitable for submicron measurement and processing.
No lubricating oil required: Air is used as a lubricating medium, eliminating the dependence on traditional lubricants, avoiding oil pollution and long-term maintenance problems, and is particularly suitable for high-standard environments such as clean rooms.
Low noise, no vibration: Air bearings have no metal friction sound during operation, low vibration, and negligible operating noise.
High acceleration and dynamic response: Since there is no sliding or collision of rolling elements, air bearings perform particularly well in high acceleration and high speed applications.
Good damping performance: The air film itself has natural squeeze film damping characteristics, which effectively suppresses vibration and resonance, and improves system stability and controllability.
Dust-proof self-cleaning: The air film has an "air sweeping" function, which can effectively repel dust from entering the contact area, thereby avoiding the impact of pollution on the bearing accuracy and life.
3. Efficiency and load capacity
The efficiency of air bearings is generally about 60%. In design, the actual load capacity of the bearing can be estimated by "air pressure × force area × 60%". For example, under the conditions of air pressure of 0.5MPa and bearing area of 100cm², its maximum theoretical load capacity is 0.5×100×60% = about 30 kg.
It is worth noting that with the increase of force area, higher stability, rigidity and damping performance can be obtained while maintaining a lower air supply pressure.
4. Guide rail and guide surface selection
In order to ensure that the air bearing achieves the best operating effect, it is necessary to match high-quality guide rails or guide surfaces. Common guide rail materials include:
Granite: Excellent thermal stability, not easy to deform, often used in coordinate measurement systems.
Hard anodized aluminum: Lightweight, easy to process, and relatively low cost.
Stainless steel or hardened steel: Good corrosion resistance is required and is often used in special industrial environments.
Polymer: Emerging surface materials with good cost-effectiveness and applicability.
The surface finish requirement is generally 16 RMS or higher, and the local flatness (especially in the support area under the bearing) should be controlled within 50% of the bearing air gap to prevent air film rupture or unstable support.
4. Typical application areas
Air bearings are widely used in key equipment that requires ultra-high precision, low friction and clean environment. Typical application scenarios include:
Coordinate measuring machine (CMM): Achieve sub-micron three-dimensional measurement.
Semiconductor manufacturing equipment: Such as lithography machines and wafer handling systems, suitable for clean room requirements.
High-speed machining center: Used for precision spindle or platform systems to improve machining accuracy.
Laser cutting and inspection equipment: Ensure smooth movement and high repeatability.
Scientific research instruments: Such as interferometers, nanopositioning platforms, electron microscopes, etc.
5. Summary
Air bearings are becoming an important component in the field of precision engineering due to their technical characteristics such as non-contact, low friction, high precision and pollution-free. With the continuous advancement of manufacturing technology and material science, the structural design of air bearings will become more diversified and economical, and their applications will be further expanded to broader high-end manufacturing fields such as automation, aerospace, and medical equipment.
Whether it is to improve equipment performance or extend service life, air bearings are undoubtedly one of the core technologies that cannot be ignored in modern industrial systems.
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Introduction to air bearing products
Air bearings are high-precision bearing devices that use compressed air to form a thin air film between solid surfaces to achieve non-contact support and movement. It is a type of "fluid film" bearing with excellent characteristics such as zero friction, no wear, high precision and low noise. It is widely used in high-end manufacturing fields such as measuring equipment, semiconductor processes, optical systems, and scientific research platforms.
1. Working principle
The core of the air bearing is its "air film", which is formed by continuously supplying compressed air to the bearing surface. The air film provides a stable floating layer between solid moving parts, making the movement process truly "contactless". The common air supply structures currently include:
Microporous orifice type: multiple tiny pores are distributed on the bearing surface to release compressed air quantitatively.
Porous media type: sintered ceramics, porous graphite or polymer composite materials are used, and air evenly penetrates the entire bearing surface, which is more stable.
Slot-type: exhaust is distributed in linear gaps, suitable for large sliding surfaces.
2. Manufacturing process of air bearings
The performance of air bearings depends largely on their manufacturing process and precision control. The following are the main steps and points to note when manufacturing air bearings:
1. Material selection
Porous material bearings: usually use porous carbon graphite, porous ceramics or high-performance plastics such as PEEK. It is required that the pores are evenly distributed and the gas permeability is stable.
Rigid structure bearings: such as aluminum alloys and hard stainless steel surfaces with high-precision orifice arrays or ceramic spraying.
2. Micropore processing and positioning
The aperture of micropores is usually 10~50 microns, and precision methods such as laser drilling, electrospark micropore processing (EDM) or photolithography must be used.
The uniformity of the pores directly determines the floating stability of the bearing. CNC five-axis linkage equipment is usually used for high-precision hole positioning.
3. Surface treatment
The sliding surface should be ultra-finished (such as mirror grinding and polishing) to achieve a surface roughness of <16 RMS.
Some types also require hard oxidation and ceramic coating treatment to improve wear resistance and corrosion resistance.
4. Assembly and testing
Each air bearing must undergo quality control procedures such as air gap uniformity test, dynamic load test, and gas leakage test before leaving the factory.
The air film thickness and lift performance must be verified by a high-sensitivity laser interferometer or floating height measurement system.
III. Manufacturing precautions
High cleanliness requirements for the air source: compressed air must be filtered at multiple stages (generally below 0.01μm) to prevent particles from blocking micropores or contaminating the guide surface.
The air path design must be stable: it is recommended to use a high-stability pressure regulating valve and air storage tank to avoid pressure fluctuations that cause bearing drift or defloating.
The assembly environment requires cleanliness: manufacturing and assembly should be carried out in a clean workshop to prevent dust from entering the air channel or working surface.
Sealing and insulation structure treatment: For porous materials, edge leakage should be prevented, and boundary sealing treatment should be performed when necessary.
IV. Application fields
Air bearings have been widely used in the following fields due to their non-contact, friction-free, and high rigidity characteristics:
Coordinate measuring machine (CMM): used for submicron measurement, with good floating stability.
Semiconductor manufacturing equipment: such as lithography machines and wafer transfer arms, with high cleanliness requirements.
Laser processing equipment: cutting systems that require high speed and high repeatability.
Vacuum environment instruments: such as electron microscopes and mass spectrometers, suitable for oil-free operation.
Scientific research platforms: interferometers, gravity wave measurement equipment, etc., require extremely low noise and high stability.
V. Summary
Air bearings combine modern precision manufacturing, microfluidic design and material engineering technology to provide an ideal non-contact motion solution for high-end equipment. Its application in precision measurement, high-speed handling, clean room equipment and other fields is constantly expanding, and it is also driving the entire precision machinery industry towards higher precision, lower energy consumption and more intelligent development.
With the advancement of process technology and the optimization of costs, air bearings will play an increasingly important role in emerging fields such as industrial automation, aerospace, medical equipment, and quantum instruments.
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