Post on 09-Jan-2017
transcript
ASeminar
ON
“AIR BEARING IN HIGH PRECISION SYSTEM”
By Mr. KUMBHAR AKSHAY
CONTENTHISTORYINTRODUCTIONWORKING APPLICATIONSADVANTAGES /DISADVANTAGESCONCLUSION
HISTORYAir bearings are not a new technology
In 1828 Rev. Wills published a work in the Cambridge
Philosophical Society entitled “On the Pressure Produced on a Flat
Surface When Opposed to Stream of Air Issuing from an Orifice
in a Plane Surface”.
In 1904 air bearings were patented by G Westinghouse in vertical
steam turbine
The technology was commercialized when IBM used air bearing
spindles to produce large hard disc drives during the 70’s.
Last decades brought high accuracy demands in production
equipment applications.
•AIR BEARING
•An air bearing is a non-contacting system
where a gas film (typically air) acts as the lubricant
and supports the two surfaces in relative motion.
• As they are contact-free, air bearings
avoid the traditional bearing-related problems of
friction, wear, particulates, and lubricant handling.
•FRICTION Less Friction as compared to rolling And plain bearing
• WEARIBILITY Materials used in other bearing eventually gets used up with time, which requires replacement.
• LUBRICATION Unlike other bearing ,no lubrication is required.
USE OF AIR BEARINGS
•STIFFNESS:
A 6” diameter bearing running at 60psi actually has a stiffness greater
than 2,000,000 lb/in with a load of 1,000 lbs
•LOAD CAPACITY:
•When compensation is used to increase bearing stiffness, the average
pressure under the bearing is usually about 50 percent of the input supply
pressure. Air bearings can therefore generally be considered to be 50
percent efficient with regard to input pressure.
Types of air bearing• There are basically two types of air bearing:
1)Aerostatic : a) Air Caster b) Porous Media c) Orifice2)Aerodynamic: a) Foil bearing
Aerodynamic Bearing
Aerostatic Bearing
WORKING• Deflated :
In the deflated stage, the air bearing , it is resting on the floor with most of the weight being supported by the center load pad.
• Inflated :The second image shows the air bearing in an inflated form
after it has formed a seal with the floor surface. At this stage, the load has not been engaged to float away from the floor.
WORKING
• Load Lifted On Air : The above image shows the air bearing after it has engaged and floated the load. Compressed air will then start to escape from the bearing diaphragm into the area that is being contained by the floor seal. • The weight of the load causes the compressed air escapingout of the air bearing to force downward onto the floorsurface thus causing the load to float away from the floor.
Applications in High Precise System
•CMM•Automotive technology•Adjustment slider for optics production•Inspection Devices•Linear Drives•Medical Technology•Precision Machine Tools•Many more
CMM
•A machine which takes readings
in six degrees of freedom and displays
these readings in mathematical form is
known as a CMM.
•It requires very high and precise readings
•The probe which moves in X,Y, & Z
direction is controlled by Air bearing.
Medical technology
•Fat- and oil-free drives for respirators, stick-
slip-free movements of scanners or
a high rotary speed of large rotors have all
been achieved with air bearings.
•Air-guided computed tomography.
Linear drives
Precision measurement stageHigh-accelerated Doppler driveDrive for production machine
Production technology•Air bearing for the adjustment of components:
With air-guided units, optical components can be arranged
to have the same diameter on a rotary table.
•Adjustment slider for optics production:
The linear slider, which is air-guided and statically determined,
guarantees a high-precision positioning of the optical
component before grinding
Testing Equipment
•Many of the most accurate friction testing machines use air
bearings to eliminate mechanical contact friction.
•Being non-contact, air bearings are insensitive to high frequency
short travel applications.
ADVANTAGES
• GREATER PRECISION
• HIGH SPEED
• INCREASED TOOL LIFE
• IMPROVED SURFACE FINISH
• LONG BEARING LIFE
• CLAENLINESS
DISADVANTAGE
• HIGH GEOMETRY ACCURACY DURING
MANUFACTURING.
• CLEAN AND DRY SUPPLY OF PRESSURIZED AIR.
• HIGH PRICING.
• REQUIRE SOME KIND OF POWER CONSUMPTION
CONCLUSION•It is a technology that improves accuracy, resolution, smoothness
and dynamic response performance over rolling element bearings
• It is Viable clean solution for high speed applications.
• These advantages turn them into a clean and environment
Friendly bearing solution for various high-speed applications
such as optical scanning equipment and machine tool spindles
for PCB drilling and micro-milling.
References•Tobias Waumans, Jan Peirs, Farid Al-Bender, Dominiek Reynaert(2011) “Air bearing for
high speed applications” Vienano
•Crăcăoanu1 and F. Bremer(2008)” Air bearing in high precision system”
•Manoj Kumar Sharma, Gohil Priyank(2013)” Study of Dynamic Characteristics and Design
Analysis of Bush & Spindle of Ultra-Precision Aerostatic Bearing” IJSR
•http://www.newwayairbearings.com/design/technical-resources/new-way-technical-
reports/tech-report-1-air-bearing-comparison
•https://en.wikipedia.org/wiki/Air_bearing
•AIRFLOAT” How air bearings work” Decatur LLC · 2230