Types
of Spindles
Different bearing systems are integrated into spindles. Spindles are high-speed shaft rotation systems. Air bearing spindle is a popular category of spindles where air supply is used for operation. Air bearings are used in such spindles. Air bearings employ a compressed air supply in these spindles which provide clearance and allow for rotary motion with any physical contact, thereby removing wear and friction, and allowing for high speeds.
The demand for air bearing spindles is on the rise because of the modern technological developments leading to increasing demand for rotation systems with lower vibration and higher maximum rotation speed. The air bearing spindles are suitable for high speed micro machining applications in a restricted space. They are ideal for high speed precision applications.
Features of air bearing spindles
Some notable features of air bearing spindles are as follows:
- Air-bearing spindle allows higher-speed rotation.
- They are designed in such a way so as to produce higher accuracy.
- There is lower vibration of the rotating shaft of these spindles.
- They only require a clear air supply for operation. Air supply,
either compressed air or compressed air, is used.
- These air bearing spindles provide good load capacity.
- They provide extremely high stiffness with very low runout.
- They are inherently frictionless.
- The combination of air bearings and air turbine drive makes the
spindle almost maintenance free.
- Many sizes, configurations and materials of such spindles are
available.
- Run out is very minimal in such spindles.
Types of air bearing spindles
Two common types of air bearing spindles are
- Aerostatic : Compressed air
- Aerodynamic: Atmospheric pressure
Applications of Air Bearing Spindles
- Micromachining & Fine Milling
- Fine Drilling
- Grinding
- Soft and Hard-Material Dicing
- Wafer testing
- Spinners
- Optical Components
- Semi-conductor industries
- PCB drilling
- Digital pre-press
- Machining
- Disk-drive inspection
- Testing system
Advantages of air bearing spindles
Some of the advantages of air bearing spindles which make them better compared to other types of spindles are as follows:
- High Rotational Accuracy
- Low Vibration
- High Dimensional Stability: This is achieved by low bearing
friction and water cooling leading to negligible thermal growth.
- High Speeds: Again low bearing friction and the use of water
cooling allow air bearing spindles to operate at extremely high surface
speeds.
- High Stiffness: The small clearances inherent to air bearings
makes the spindle to be designed with high static stiffness. Usage of
air bearings enhances the stiffness of spindle assemblies.
- Increased Bearing Life: The absence of metal to metal contact
leads to an unlimited bearing life. For this the air supply should be
maintained clean and free from oil and water.
- Improved Surface Finish: Due to the unique feature of high
accuracy of rotation of air bearings and low vibration, air bearing
spindles used in machining applications can produce ultra high surface
finishe.
- Cleanliness: Since air spindles do not require any liquid
lubricants, they are suitable for use in clean rooms.
- Ease of Maintenance: These spindles generally do not require any servicing but only the air supplies should be maintained.
Disadvantages of air bearing spindles
- Air bearings are available in some fixed sizes and there is every
chance of contaminants (solid particles, oil, water) in the air supply
which will clog the air portals.
- The air pressure to keep the air bearings stiff should be at least 80
PSI at the input to the spindle which is not always the case in most
spindles. As a rule, air pressure must not exceed 90 PSI.
- Always maintain the cooling system. Overheating a air bearing spindle causes the metal to expand, thereby suffocating the air bearing gaps.
