page 401
from poor grounding or unexpected metal contact.
•Some automation issues are,
-part recognition on a conveyor
-color changes
-booths are costly, but provide safety and process advantages
62.2 PRACTICE PROBLEMS
1.TRUE / FALSE - Parts can be electrostatically coated by dipping molds in a bath of thermo plastic powder.
2.TRUE / FALSE - Electrostatic painting uses electrical charge for better mixing of paint components.
63. AIR-PLASMA CUTTING
•Basic process - uses an ionized gas jet (plasma) to cut material
•can be used on all materials that conduct electricity
•can be used to cut materials resistant to oxy-fuel cutting,
-stainless steel
-monel
-super-alloy plates
•Plasma is generated by exposing a gas stream to the electrons from an electric arc. High velocity electrons generated by the arc impact gas molecules, and ionize them.
page 402
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electrode |
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H2,N2,O2 |
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gas inlet |
cutting |
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power |
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supply |
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plasma jet |
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work |
•The gas is forced through the nozzle, and the jet heats the metal, and blasts the molten metal away.
•Advantages
-3 to 5 times faster than conventional gas cutting
-can deal with any conducting material, including those not suited to normal gas cutting.
-stainless steels
-chromium-nickel alloys
-aluminum
-copper
-etc
-works best on ranges from .03” to 1”
-More efficient than other types of gas plasma
-can cut up to .15 m/sec continuously.
page 403
high
frequency air igniter
coolant |
torch |
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exhaust |
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filter- |
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material |
collector |
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smoke |
water |
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cooler |
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with |
slag |
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pump |
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air-plasma |
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power pack |
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smoke |
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water |
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air |
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water |
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compressor |
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and dryer |
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•Summary of Air-Plasma characteristics,
-mechanics of material removal - melting
-medium - plasma
-tool - plasma jet
-maximum temperature = 16,000C
-maximum velocity of plasma jet = 500 m/sec
-maximum mrr = 150 cm3/min
-specific energy = 1000 W/cm3/min
-power range = 2 to 200 KW
-maximum plate thickness = 200 mm (depends on material)
-cutting speed = 0.1 to 7.5 m/min
-voltage 30 to 250 V
-current <= 600 A
-critical parameters - voltage, current, electrode gap, gas flow rate, nozzle dimensions,
page 404
melting temperature
-materials applications - all conducting materials
-shape application - cutting plates
-limitation - low accuracy
63.1 REFERENCES
Ghosh, A., Manufacturing Science, Ellis Horwood Ltd., Chichester, UK, 1986.
Flexible Manufacturing Systems