Deck 8: Plasma Arc Cutting

Question 1

In stacked cutting of sheets using the PAC process, sheets are held together using ____.

A) a small piece of metal welded to the side of the sheets
B) a water table
C) C-clamps
D) their weight

Answer 1

C

Question 2

The electrode tip is often made of copper with a ________ imbedded in the tip

A) tungsten
B) hafnium-coated tungsten
C) hafnium cylinder
D) All of the above

Answer 2

D

Question 3

The temperature of an unrestricted arc is about ____ degrees Fahrenheit.

A) 1,000
B) 11,000
C) 43,000
D) 110,000

Answer 3

B

Question 4

Keeping the diameter of the nozzle orifice ____ will keep the kerf ____.

A) as small as possible, smoother
B) as small as possible, smaller
C) as large as possible, smoother
D) as large as possible, smaller

Question 5

The ____ has a small, cone-shaped, constricting orifice in the center.

A) nozzle tip
B) nozzle insulator
C) electrode tip
D) water shroud

Question 6

The earliest gas tungsten arc welding process used ____.

A) tungsten
B) argon
C) oxygen
D) helium

Question 7

The ____ is made of a special plastic that is resistant to high temperatures, ultraviolet light, and impact.

A) torch body
B) torch head
C) power switch
D) nozzle

Question 8

Heat distortion is a greater problem for cuts on ________________.

A) thin metal
B) thicker metal
C) out of position metal sections
D) thicker aluminum plates

Question 9

High-powered plasma cutting machines have amperages as high as ____ amps, and some very large automated cutting machines may have 1000-ampere capacities.

A) 100
B) 200
C) 500
D) 800

Question 10

The plasma created by an arc ____.

A) is the fluid portion of blood
B) contains an ionized gas
C) is an ionized gas that contains both electrons and positive ions
D) cannot conduct electricity

Question 11

The voltage required for plasma arc processes range from ____ open circuit.

A) 18 to 45 volts
B) 150 to 400 volts
C) 400 to 600 volts
D) 600 to 1000 volts

Question 12

The power switch on a handheld torch must have a _________ as part of the switch.

A) bright color
B) smooth finish
C) easy pull
D) safety guard

Question 13

The temperature created when the arc is concentrated to form a plasma is about ____degrees Fahrenheit.

A) 1,000
B) 11,000
C) 43,000
D) 110,000

Question 14

Manual plasma arc cutting is ____.

A) suitable for all plasma machines
B) limited to high-power machines
C) limited to robotic processes
D) limited to low-power machines

Question 15

In plasma arc gouging, the torch is held at approximately a ____ degree angle to the metal surface.

A) 30
B) 45
C) 90
D) 180

Question 16

What is the term used to describe the plasma cutting process that uses two different gasses?

A) twin gas cutting
B) multiple gas plasma cutting
C) dual gas plasma cutting
D) twin gas plasma cutting process

Question 17

The production of the plasma requires a(n) ____ power supply.

A) alternating current
B) direct current
C) either AC or DC
D) low voltage

Question 18

Why should deionized water be used for cooling high-amperage plasma torches?

A) It is free of materials that can clog the small internal openings in the torch.
B) It is free from conductive ions that can damage torch parts over time.
C) It will not freeze in cold weather.
D) Both a and b are correct.

Question 19

What happens to the plasma column when water is injected around the plasma stream?

A) It concentrates the plasma stream.
B) It causes a steam cloud to shield the arc.
C) It reduces the temperature of the plasma.
D) It shorts out the plasma arc.

Question 20

The ____ surrounding the nozzle tip is used to control the potential hazards of light, fumes, noise, and other pollutants.

A) argon
B) water
C) oxygen
D) ions

Question 21

​The sides of the plasma stream are not parallel, so one side of the cut will have a bevel of ______.

A) ​1/2o to 3o
B) ​2o to 4o
C) ​1/4o to 1/2o
D) ​0o to 2o

Question 22

​Some small plasma cutting machines have ______ and can be used on 120V power.

A) ​self-contained air compressors
B) ​an argon cylinder for a shielding gas
C) ​an oxygen cylinder for cutting gasses
D) ​Both b and c are correct

Question 23

​What metals can produce poisonous metal fumes that must be collected in a fume collection system to prevent air pollution?

A) ​cadmium
B) ​zinc
C) ​chromium
D) ​All of the above

Question 24

​What may need to be done as the nozzle and electrode wear?

A) ​Tighten the nozzle and loosen the electrode to reduce the gap.
B) ​Increase the cutting gas flow.
C) ​Increase the machine voltage.
D) ​Reduce the cutting speed.

Question 25

​What will happen if the gas flow is too high?

A) ​The cutting speed can be increased on thicker metal.
B) ​Thicker metal can be cut but only if the torch can travel faster.
C) ​Aluminum can be cut easier.
D) ​Turbulence will cause a poor cut.

Question 26

The ____________________ created by an arc is an ionized gas.

Question 27

​What happens if the standoff distance is increased?

A) ​The arc force is increased because the resistance is higher and the voltage increases.
B) ​The plasma are will begin to drift sideways due to arc blow.
C) ​The plasma stream will lose some of its stiffness.
D) ​Not much until the distance is so great that the arc goes out.

Question 28

​All nontransfer-type plasma torches must have ________________.

A) ​argon shielding gas
B) ​two power cables-one for + and one for -
C) ​a hose to carry cooling water
D) ​a drag type nozzle

Question 29

​The nozzle or gas shield of a plasma torch is made of ____.

A) ​tungsten or hafnium
B) ​copper or brass
C) ​chrome plated stainless steel
D) ​ceramic or other high-temperature resistant material

Question 30

The nozzle is sometimes called the ____________________.

Question 31

​What tip material is resistant to oxidation at high temperatures?

A) ​tungsten
B) ​hafnium
C) ​copper
D) ​brass

Question 32

​What happens if the standoff distance becomes too close?

A) ​The working life of the nozzle tip is reduced.
B) ​The plasma stream becomes too cool to continue the cut due to the lower arc voltage.
C) ​As long as the arc keeps going, the cut will be better and can be cut faster.
D) ​On sheet metal the plate can be overheated and begin to distort from the heat.

Question 33

​What effect does the swirling of the plasma gas have?

A) ​Centrifugal force causes the stream to spread out or even causes it to go off.
B) ​The wider plasma arc is best used for gouging.
C) ​It causes the sparks to spin outward scattering them around the shop floor.
D) ​It causes the stream to become more dense.

Question 34

____ are good metals to gouge because there is almost no cleanup.

A) Copper and magnesium
B) Zinc and iron
C) Stainless steel and aluminum
D) Carbon steel and copper

Question 35

The ____________________ distance is the distance from the nozzle tip to the work.

Question 36

The spacing between the electrode tip and the nozzle tip is called the ____________________.

Question 37

​Why would some large plasma cutting machines have two gas hoses?

A) ​One for cooling and one for the plasma gas.
B) ​One is a backup in case the other is damaged by the hot sparks and slag.
C) ​One for the plasma gas and one for the shielding gas.
D) ​Torches only need one gas hose.

Question 38

​When air is used for the plasma gas, it must be clean and dry so a ______ must be used.

A) ​filter dryer
B) ​strainer and dust collector
C) ​clear plastic hose so you can see any dirt
D) ​short as possible hose

Question 39

____________________ are units of measure for electrical power.

Question 40

​Plasma cutting machines can cut mild steel ranging from _____ to _____or more in thickness.

A) ​1/4 in (6 mm) to 3 in (75 mm)
B) ​1/8 in (3 mm) to 1 in (25 mm)
C) ​1/64 in (0.4 mm) to 7 in (180 mm)
D) ​1/16 in (1.6 mm) to 1.5 in (37 mm)

Question 41

A(n) ____________________ is used to reduce the noise level, control the plasma light, trap the sparks, eliminate most of the fume hazard, and reduce distortion.

Question 42

Explain Ohm's Law, and use Ohm's Law to calculate the number of watts used for an electrode operating at 18 volts and 90 amps.

Question 43

Explain what happens when standoff distance increases.

Question 44

Sheets can be stacked in the PAC process because PAC does not rely on the ____________________ between stacked parts.

Question 45

Describe the history of the development of plasma arc cutting.

Question 46

Explain how high-frequency alternating current and a pilot arc can be used to start a plasma arc torch.

Question 47

Any material that is ____________________ can be cut using the PAC process.

Question 48

The most common method to establish a current path through the gas uses a high-frequency ____________________ current carried through the conductor, the electrode, and back from the nozzle tip.

Question 49

Explain how metal becomes distorted during the welding process.

Question 50

____________________ is the metal compound that resolidifies and attaches itself to the bottom of a cut.