The illustrated PPT presentation for the seminar gives a brief report on Air bearings also known as Gas bearing with diagrams, images, and animations. The main topics covered are types, Aerostatic bearings, Aerodynamic bearings, Advantages and disadvantages of gas-lubricated bearings, Theoretical modeling, Applications in automotive, space technology, medical, production, semiconductor, linear drives etc.

1. Air
Bearings

2. What is an Air Bearing?
An air bearing is a non-contacting system where
air acts as the lubricant that separates the two
surfaces in relative motion.
To compare this with ball bearings, in ball bearings
the balls are in constant contact with and form a
solid bridge between the machine elements.
Air bearings are being mainly used in precision
machinery tools (measuring and processing
machines) and high-speed machines (spindle,
small-scale turbomachinery).

3. Cutaway of an air bearing PCB drilling spindle

4. Why use air (instead of oil)?
• Air is clean, contaminant free
• Zero friction - no heat
• Generation at high speeds
• Small bearing gap means
• High accuracy components,
• High accuracy motion
• Air nitrogen or any other
• Gas can be used

5. When to use air bearings?
• Air bearings are not suitable for all applications but when they are used
effectively, each prescription has some common characteristics.
• Generally, it is advisable to use air bearings when one or more of the
following is an application requirement:
• Nanometric repeatability and/or accuracy
• Frictionless motion
• Zero stiction
• Zero backlash
• Zero wear of the mating surfaces
• High speed and high acceleration
• Low or near-zero particle emission

6. When not to use air bearings?
Generally, do not use air bearings when the application:
• does not require near frictionless motion
• does not require high accuracy and repeatability
• involves environments where the air bearing surfaces may be exposed to oils or other sticky
substances
• cannot allow for a pressure source in the case of aerostatic air bearings (externally pressurized)
• requires minimal performance after high overload conditions on the air bearing
• cannot provide for accurate machining of the mating surface in the case of flat or cylindrical
bushing air bearings
• requires high load capacity in a small design envelope

7. Types of Air Bearing
Gas-lubricated bearings are classified in two groups, depending on the
source of pressurization of the gas film providing the load-carrying
capacity:
• Aerostatic bearings
• Aerodynamic bearings

8. Aerostatic Bearings
Externally pressurized
• A separate external supply of air is
fed under pressure between the
two surfaces being kept apart.
• It is a continuous flow system where
pressurized gas from the source
flows through restrictors into the
clearance between the bearing
surfaces escaping to the
atmosphere at the outside edges of
the bearing.

9. Cross-section through bearing, fitted with orifices Section through orifice line
Source: Westwind

10. Delivery of Gas to the Gap
• Supplying gas to the interface between moving elements of an
aerostatic bearing can be achieved in a few different methods:
• Porous Surface
• Partial porous surface
• Discrete orifice feeding
• Slot feeding
• Groove feeding
• There is no single best approach to feeding the film.
• All methods have their advantages and disadvantages specific to each
application.

11. Image Source: Specialty Components

12. Porous Air Bearing
Nozzle-air bearing with
chambers and channels

13. Aerodynamic Bearings
Self Generating
• The supporting film is generated by the relative
motion of the two surfaces being kept apart.
• As the speed increases, a velocity induced
pressure gradient is formed across the clearance.
• The increased pressure between the surfaces
creates the load carrying effect.
• Load capacity is dependent on the relative speed
at which the surface moves and therefore at zero
speed, the bearing supports no load.
• Types: Simple cylinders, Tri-lobe, Grooved (axial /
herringbone / spiral) and Stepped.
Westwind tri-lobed aerodynamic bearing
Source: Westwind

14. Aerodynamic Bearings - Technology
• Foil bearing
• Bearing surface is flexible, allowing large displacement and providing a good
stability.
• Spiral groove bearing
• Gas film is pressurized by grooves machined on one of the surfaces, achieving
high load capacity and stability.
• The usual groove patterns are herringbone-shaped, spiral or straight (step
bearings)

15. Applications
• Foil Bearing: Turbomachinery
• Spiral groove bearing :
• Gyroscopes for pro aviation and
astronautics
• Circulation Blowers
• Rotor support of helium
liquefaction expansion turbine
• High speed blowers
• Polygonal mirrors in Laser Scanning
• As magnetic read/write heads in
disk memory storage devices
Spiral groove bearings with journal and
thrust forms.
Foil Bearing
High Capacity Air Bearings
Source: Lincoln Laser

16. Applications
Air bearing cutting engine Air bearing Doppler engine

17. Air bearing 2-axis table with friction drive
Air bearing satellite system for Solar Arrays

18. Bearing with piston actor
Air Bearings in proposed Hyperloop

19. Advantages and Disadvantages of Air Bearings
Advantages
• lack of oil-based lubricants for
operation
• no service maintenance
• no “run-in” period
• simplification over conventional
bearings
• improved damping in dynamic
performance
• improved machine efficiency
• Cost advantage and repeatability.
Disadvantages
• Self-excited vibration
• Tight manufacturing tolerances
• sensitive to the presence of
particulates and dust

20. Thank You