Transcript Plasma Cutting and Its Effect on Mild Steel

Plasma Arc Cutting
29103-09
Background of Plasma Arc Process
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In 1941 the U.S. defense
industry was looking for a
way to join light metals,
from this came Tungsten
Inert Gas (TIG) welding
It was found that by
passing a gas through the
TIG arc that metal could
be cut by gas in a plasma
state
TIG and plasma arc
processes were created for
the aerospace industry,
primarily for aluminum
which is difficult to weld by
other processes and
difficult to cut with a torch
CNC Plasma Cutting Machine,
1980
How a Plasma Cutter Works
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An arc is used to
ionize the gas around
a high voltage arc
This ionized gas is
superheated by the
arc to plasma (1)
In the plasma state,
the gas is at
30,000˚F, reducing
the steel to a molten
state, allowing the
stream of gas to push
it out of the cut
Advantages Plasma Cutting
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Super heat makes
plasma cutting
faster and more
efficient than any
other form of
cutting. (2)
Two Types of PAC
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Transferred Arc
Process – the work
piece is part of the
electrical circuit as in
other arc processes.
(3)
Non-transferred Arc
Process – the work is
not part of the circuit.
The arc is generated
inside the torch and
nozzle.
Most PAC
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The simplest and most common form of PAC is the use of
filtered compressed air (4) and cooling gases.
When compressed air is used with a PAC unit, the correct air
flow rate and pressure are maintained by the air pressure
regulator and filter/dryer on the power source. (14)
They use a pilot arc and the transferred arc process.(6)
The most common PAC contains the following (7):
• Retaining cup
• Copper electrode with a hafnium thoriated tungsten
insert
• Gas swirl ring, and
• nozzle
Most PAC
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The most common PAC PARTS THAT ARE
CHANGED OUT ARE (8):
• ELECTRODE
• NOZZLE
• MOST HEAVY DUTY PAC REQUIRE GAS:
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ONE GAS CYLINDER CONTAINING THE CUTTING GAS AND
ANOTHER CONTAINING SHIELDING OR COOLING GASES.
(11)
• Sometimes they will hiss and sputter like an oxyfuel
torch. This means that there is moisture entering the
unit through the air line. (15)
SAFETY PAC
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The plasma cutter can get up to 30,000 degrees
F.
In industrial uses it can cut up to 3” thick mild
steel. (5)
It will cut through gloves, never put hands under
the plasma arc or the work piece when cutting.
Make sure plasma cutter power Is off before
touching.
Safety glasses, full face mask, or helmet, same
rules as a apply to other arc processes.
Same PPE (leather, dark clothes, wool, cotton,
thick, boots, gloves, insulated).
SAFETY FIRE AND EXPLOSION
WITH PAC
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CHECK FOR FLAMMABLES DUE TO SPARKS
(MATCHES AND LIGHTERS, ETC.)
NEVER USE OXYGEN AS COMPRESSED AIR
(BABOOM!)
A HYDROGEN GAS EXPLOSION EXPOSURE EXISTS
IF USING A PAC NEAR A BETTERY. (9)
ALWAYS REMOVE CYLINDERS AND REPLACE
CYLINDER CAPS FROM PAC UNITS. (10)
SETTING FOR PAC
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CHECK THE METAL AND THICKNESS YOU ARE
CUTTING. THUIS WILL DICTATE THE SETTINGS:
• RATING MACHINERY USUALLY BY:
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DUTY CYCLE
MAXIMUM CUTTING CAPABILITY
• IMPORTANT THAT YOU UNDERSTAND THE POWER
SUPPLY REQUIRED AND LIMITATIONS BEFORE
COMMENCING CUTTING.
• RUNS ON DCEN
• MOST RUN ION 115 OR 230 VAC AND CUTTING THINNER
SHEET OF METAL, 14 TO 30 AMPS
SETTING FOR PAC
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CHECK THE METAL AND THICKNESS YOU ARE
CUTTING. THUIS WILL DICTATE THE SETTINGS:
• RATING MACHINERY USUALLY BY:
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DUTY CYCLE
MAXIMUM CUTTING CAPABILITY
• IMPORTANT THAT YOU UNDERSTAND THE POWER
SUPPLY REQUIRED AND LIMITATIONS BEFORE
COMMENCING CUTTING.
• RUNS ON DCEN
• MOST RUN ON 115 OR 230 VAC AND CUTTING THINNER
SHEET OF METAL, 14 TO 30 AMPS
• HOWEVER A 2” ALUMINUM MAY REQUIRE UP TO 250
AMPS. (12)
SETTING FOR PAC
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ANGLE IS ALSO AN IMPORTANT VARIABLE.
• THIN STEEL, USE 0 DEGREES ANGLE. (13)
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When compressed air is used with a
PAC unit, the correct air flow rate and
pressure are maintained by the air
pressure regulator and filter/dryer on
the power source.