Plasma Cutting 265
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Class Outline
Objectives
What Is Plasma Cutting?
Power Supply
Plasma Cutting Torch
Starter Types
Air Flow Control
Plasma Cutting Safety
Preparing a Cut
Steps for Cutting
Cutting Guides
Plasma Gouging
Plasma Piercing
Mechanized Plasma Cutting
Basic Troubleshooting
Copyright
© 2009 of
Tooling
U, LLC.
All Rights Reserved.
The
Advantages
Plasma
Cutting
Summary
Class Outline
Objectives
What Is Plasma Cutting?
Power Supply
Plasma Cutting Torch
Starter Types
Air Flow Control
Plasma Cutting Safety
Preparing a Cut
Steps for Cutting
Cutting Guides
Plasma Gouging
Plasma Piercing
Mechanized Plasma Cutting
Basic Troubleshooting
The Advantages of Plasma Cutting
Summary
Lesson: 1/16
Objectives
l
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Define plasma cutting.
List the major parts of a plasma cutting
machine.
Describe the plasma cutting torch.
Distinguish between types of starters.
Explain the control of gas by a plasma cutting
machine.
Describe basic plasma cutting safety.
Explain how to prepare for a cut.
Explain the plasma cutting procedure.
Describe the use of a cutting guide.
Explain how to gouge metal with a plasma
cutting machine.
Describe basic mechanized plasma cutting.
Describe basic troubleshooting techniques.
Describe the advantages of plasma cutting.
Figure 1. Plasma cutting is a versatile way to cut metal.
Figure 2. Plasma cutting machines involve parts called consumables, which can be
worn out with usage.
Copyright © 2009 Tooling U, LLC. All Rights Reserved.
Lesson: 1/16
Objectives
l
l
l
l
l
l
l
l
l
l
l
l
l
Define plasma cutting.
List the major parts of a plasma cutting
machine.
Describe the plasma cutting torch.
Distinguish between types of starters.
Explain the control of gas by a plasma cutting
machine.
Describe basic plasma cutting safety.
Explain how to prepare for a cut.
Explain the plasma cutting procedure.
Describe the use of a cutting guide.
Explain how to gouge metal with a plasma
cutting machine.
Describe basic mechanized plasma cutting.
Describe basic troubleshooting techniques.
Describe the advantages of plasma cutting.
Figure 1. Plasma cutting is a versatile way to cut metal.
Figure 2. Plasma cutting machines involve parts called consumables, which can be
worn out with usage.
Lesson: 2/16
What Is Plasma Cutting?
Plasma cutting is a method of cutting metal with a jet of air, ionized by an electric
arc to create plasma, as shown in Figure 1. Plasma is the fourth state of matter.
The other more common states of matter are solid, liquid, and gas, as shown in
Figure 2. When gas is superheated, it becomes plasma.
Because plasma is incredibly hot, it can easily melt through most metals, making
cutting simple. However, until recently, the high cost of plasma cutting machines
restricted their widespread use. With advances in technology, plasma cutting
machines have become more affordable and thus more widely used.
The high temperatures of plasma cutting can be a major safety hazard if improperly
handled. With proper care and use, a plasma cutter can efficiently cut a variety of
metals safely.
In this class, you will learn about plasma cutting equipment and proper cutting
methods. You will also learn about plasma cutter safety and the other processes for
which a plasma cutting torch may be used.
Copyright © 2009 Tooling U, LLC. All Rights Reserved.
Figure 1. The electrode creates plasma by ionizing
air.
Lesson: 2/16
What Is Plasma Cutting?
Plasma cutting is a method of cutting metal with a jet of air, ionized by an electric
arc to create plasma, as shown in Figure 1. Plasma is the fourth state of matter.
The other more common states of matter are solid, liquid, and gas, as shown in
Figure 2. When gas is superheated, it becomes plasma.
Because plasma is incredibly hot, it can easily melt through most metals, making
cutting simple. However, until recently, the high cost of plasma cutting machines
restricted their widespread use. With advances in technology, plasma cutting
machines have become more affordable and thus more widely used.
The high temperatures of plasma cutting can be a major safety hazard if improperly
handled. With proper care and use, a plasma cutter can efficiently cut a variety of
metals safely.
In this class, you will learn about plasma cutting equipment and proper cutting
methods. You will also learn about plasma cutter safety and the other processes for
which a plasma cutting torch may be used.
Figure 1. The electrode creates plasma by ionizing
air.
Figure 2. Plasma is the fourth state of matter,
resulting from superheating gas.
Lesson: 3/16
Power Supply
Plasma cutting machines such as the one shown in Figure 1 come in a variety of sizes
based on the requirements of the job. The size of a plasma cutter is described by
the amperage and voltage of the machine. Plasma cutters have higher voltage and
lower amperage than arc welding machines, despite being similar in appearance.
Larger machines are capable of cutting up to one inch thick steel. Each machine
should come with manufacturer recommendations regarding the appropriate cutting
speed for a particular thickness. Thicker metals require slower cutting speeds, which
are measured in inches per minute (IPM).
The four main components of a plasma cutting machine are the power supply, the
torch, the air flow control, and the starter. The power supply is a DC power
source. Some plasma cutting machines require a low enough voltage that they can
be plugged into a normal 120 V outlet, though others require higher voltage outlets.
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Tooling
U, plasma
LLC. All cutters
Rights Reserved.
Additionally,
some
newer
use inverters that allow for higher power
and lower weight by converting AC power to DC power.
Lesson: 3/16
Power Supply
Plasma cutting machines such as the one shown in Figure 1 come in a variety of sizes
based on the requirements of the job. The size of a plasma cutter is described by
the amperage and voltage of the machine. Plasma cutters have higher voltage and
lower amperage than arc welding machines, despite being similar in appearance.
Larger machines are capable of cutting up to one inch thick steel. Each machine
should come with manufacturer recommendations regarding the appropriate cutting
speed for a particular thickness. Thicker metals require slower cutting speeds, which
are measured in inches per minute (IPM).
The four main components of a plasma cutting machine are the power supply, the
torch, the air flow control, and the starter. The power supply is a DC power
source. Some plasma cutting machines require a low enough voltage that they can
be plugged into a normal 120 V outlet, though others require higher voltage outlets.
Additionally, some newer plasma cutters use inverters that allow for higher power
and lower weight by converting AC power to DC power.
Figure 1. Plasma cutting machines consist of four
major components: the power supply, torch, air flow
control, and starter.
Lesson: 4/16
Plasma Cutting Torch
The plasma cutting torch, shown in Figure 1, is the handheld unit used to cut the
workpiece. The torch is connected to the plasma cutting machine by hoses through
which electricity and pressurized air run.
Torches have several components that can wear over time as the torch is used. These
components, shown in Figure 2, are called consumables. The number of consumables in
each torch varies, but every torch has a consumable electrode and nozzle. Both of
these parts will wear down with use because they are directly involved in the creation of
the plasma. Some torches also feature a consumable drag shield or shield cup to help
define the proper distance to hold the torch from the cut.
In addition to holding the consumables used in plasma creation, the torch also provides
cooling to the consumables in the form of gas or water. Cooling components during and
after usage helps extend their life and increases the safety of torch handling.
Additionally, some plasma torches feature a trigger safety lock to prevent accidental
activation of the plasma arc. If a torch has a safety lock, it must be deactivated manually
before the trigger can be pressed and the arc fired.
Copyright © 2009 Tooling U, LLC. All Rights Reserved.
Figure 1. The plasma torch is the handheld unit
used to cut metal.
Lesson: 4/16
Plasma Cutting Torch
The plasma cutting torch, shown in Figure 1, is the handheld unit used to cut the
workpiece. The torch is connected to the plasma cutting machine by hoses through
which electricity and pressurized air run.
Torches have several components that can wear over time as the torch is used. These
components, shown in Figure 2, are called consumables. The number of consumables in
each torch varies, but every torch has a consumable electrode and nozzle. Both of
these parts will wear down with use because they are directly involved in the creation of
the plasma. Some torches also feature a consumable drag shield or shield cup to help
define the proper distance to hold the torch from the cut.
Figure 1. The plasma torch is the handheld unit
used to cut metal.
In addition to holding the consumables used in plasma creation, the torch also provides
cooling to the consumables in the form of gas or water. Cooling components during and
after usage helps extend their life and increases the safety of torch handling.
Additionally, some plasma torches feature a trigger safety lock to prevent accidental
activation of the plasma arc. If a torch has a safety lock, it must be deactivated manually
before the trigger can be pressed and the arc fired.
Figure 2. Electrodes, nozzles, and shield cups are
all consumable plasma cutting components.
Lesson: 5/16
Starter Types
Two types of starters are used in plasma cutters: the high frequency contact starter
and the pilot arc starter. Each type has advantages and disadvantages that you should
consider when choosing a plasma cutter.
High frequency contact starters use high voltage, high frequency circuits to start the arc
that ignites the plasma. The arc can only be started when the torch is in contact with the
workpiece. Many older machines rely on this type of starter. The major drawback of high
frequency contact starters is the amount of interference they can cause with nearby
electronic equipment. For this reason, these starters should not be used around CNC
machines or any other electronic equipment.
Pilot arc starters have only recently begun to be widely used in plasma cutting machines.
Pilot arc starters use contact between the nozzle and electrode to create a pilot arc,
Copyright
© 2009
All the
Rights
Reserved.
which
ionizes
theTooling
gas asU,itLLC.
blows
nozzle
and electrode apart, causing plasma
formation. Though slightly more expensive, a pilot arc starter creates much less
interference and can be safely used around all other electronic devices, as shown in
Figure 1. When working in an area with other
Lesson: 5/16
Starter Types
Two types of starters are used in plasma cutters: the high frequency contact starter
and the pilot arc starter. Each type has advantages and disadvantages that you should
consider when choosing a plasma cutter.
High frequency contact starters use high voltage, high frequency circuits to start the arc
that ignites the plasma. The arc can only be started when the torch is in contact with the
workpiece. Many older machines rely on this type of starter. The major drawback of high
frequency contact starters is the amount of interference they can cause with nearby
electronic equipment. For this reason, these starters should not be used around CNC
machines or any other electronic equipment.
Pilot arc starters have only recently begun to be widely used in plasma cutting machines.
Pilot arc starters use contact between the nozzle and electrode to create a pilot arc,
which ionizes the gas as it blows the nozzle and electrode apart, causing plasma
formation. Though slightly more expensive, a pilot arc starter creates much less
interference and can be safely used around all other electronic devices, as shown in
Figure 1.
Figure 1. When working in an area with other
working machines, a pilot arc starter is essential.
Though you may not always be able to choose the type of starter you are working with,
being aware of the differences can save you time and trouble. Preparing for interference
generated by a starter is necessary to avoid damage to any other machinery.
Lesson: 6/16
Air Flow Control
During operation, gas is pumped into the plasma torch. This gas is used to
create the plasma and also to cool the torch after use. Most often, this gas is
compressed air provided by an attached air compressor. Some machines
include a built-in air compressor to supply air to the torch.
Air flow control, in which the flow of air from a compressor is regulated, is
achieved with a flow control valve, shown with an air pressure gauge in
Figure 1. This valve allows the operator to precisely control the amount of
pressure being supplied to the torch. Gauges show the air pressure flowing to
the torch.
Manufacturers recommend different air pressures for cutting different
thicknesses of metal. The operator of the plasma cutting machine should
consult these recommendations and regularly monitor pressure while working.
When working in a mobile setting, many operators use bottled air instead of a
heavy compressor. In these situations, operators may choose bottled nitrogen,
as it can be less expensive than bottled air.
Copyright © 2009 Tooling U, LLC. All Rights Reserved.
Figure 1. Plasma cutting machines have air pressure
gauges and flow control valves to adjust the pressure of
the air properly.
Lesson: 6/16
Air Flow Control
During operation, gas is pumped into the plasma torch. This gas is used to
create the plasma and also to cool the torch after use. Most often, this gas is
compressed air provided by an attached air compressor. Some machines
include a built-in air compressor to supply air to the torch.
Air flow control, in which the flow of air from a compressor is regulated, is
achieved with a flow control valve, shown with an air pressure gauge in
Figure 1. This valve allows the operator to precisely control the amount of
pressure being supplied to the torch. Gauges show the air pressure flowing to
the torch.
Manufacturers recommend different air pressures for cutting different
thicknesses of metal. The operator of the plasma cutting machine should
consult these recommendations and regularly monitor pressure while working.
When working in a mobile setting, many operators use bottled air instead of a
heavy compressor. In these situations, operators may choose bottled nitrogen,
as it can be less expensive than bottled air.
Figure 1. Plasma cutting machines have air pressure
gauges and flow control valves to adjust the pressure of
the air properly.
Lesson: 7/16
Plasma Cutting Safety
Safety is a priority any time you are working with a plasma cutting machine. The extreme
temperature of plasma creates a variety of hazards for anyone who is not extremely careful.
The safety precautions for using a plasma cutting machine are similar to those for any type of
arc welding.
Long sleeves and leather gloves like those in Figure 1 must be worn at all times when
handling the plasma torch. Molten metal is generated during plasma cutting and can lead to
severe burns if you are not properly protected. Clothing should be made of non-flammable
materials to prevent fire. Materials like rayon and polyester can catch fire easily and should be
avoided.
Eye protection, shown in Figure 2, is required for all plasma operations, as the infrared and
ultraviolet rays emitted by the arc can damage vision. A welding mask or goggles may be
worn depending on the preference of the welder. Filter plates and lenses should have a
darkness between 7 and 9 in most operations.
Finally, read the instruction manual of your plasma cutting machine. Any additional safety
steps recommended by the manual should be strictly followed.
Copyright © 2009 Tooling U, LLC. All Rights Reserved.
Figure 1. Leather gloves protect your hands
from sparks.
Lesson: 7/16
Plasma Cutting Safety
Safety is a priority any time you are working with a plasma cutting machine. The extreme
temperature of plasma creates a variety of hazards for anyone who is not extremely careful.
The safety precautions for using a plasma cutting machine are similar to those for any type of
arc welding.
Long sleeves and leather gloves like those in Figure 1 must be worn at all times when
handling the plasma torch. Molten metal is generated during plasma cutting and can lead to
severe burns if you are not properly protected. Clothing should be made of non-flammable
materials to prevent fire. Materials like rayon and polyester can catch fire easily and should be
avoided.
Eye protection, shown in Figure 2, is required for all plasma operations, as the infrared and
ultraviolet rays emitted by the arc can damage vision. A welding mask or goggles may be
worn depending on the preference of the welder. Filter plates and lenses should have a
darkness between 7 and 9 in most operations.
Figure 1. Leather gloves protect your hands
from sparks.
Finally, read the instruction manual of your plasma cutting machine. Any additional safety
steps recommended by the manual should be strictly followed.
Figure 2. Goggles protect your eyes from
harmful light.
Lesson: 8/16
Preparing a Cut
Preparing a cut before you begin a plasma cutting procedure can help ensure a
successful cut. You should be certain the air you are using is clean. If the air is coming
from a compressor, you should make sure the compressor and any filters are clean. Be
certain the air you are using is free of water and oil. Any unclean air supply will
eventually cause consumables to wear prematurely, or leave black marks on the
workpiece.
In order to ensure proper cutting, you should check the air pressure flowing into the
cutting torch. Proper pressure should be specified in the instruction manual of your
machine. Most plasma cutters have a pressure gauge to monitor air pressure, as shown
in Figure 1.
Before cutting, make certain the workpiece is properly secured and your working lead,
if needed, is connected to the piece properly. The lead should be fairly close to the cut
and attached to a clean part of the workpiece. If the lead is attached to a dirty section,
proper cutting can be difficult. Make sure to grind off any additional rust or paint on the
surface, especially if using a lower power cutting machine.
Finally, inspect the cutting torch. Be certain the nozzle and electrode are in place. Check
your consumables for any added wear. Be certain all parts fit together properly as
shown in Figure 2 and are snug before beginning the cut.
Copyright © 2009 Tooling U, LLC. All Rights Reserved.
Figure 1. Most plasma cutting machines have an
air pressure gauge.
Lesson: 8/16
Preparing a Cut
Preparing a cut before you begin a plasma cutting procedure can help ensure a
successful cut. You should be certain the air you are using is clean. If the air is coming
from a compressor, you should make sure the compressor and any filters are clean. Be
certain the air you are using is free of water and oil. Any unclean air supply will
eventually cause consumables to wear prematurely, or leave black marks on the
workpiece.
In order to ensure proper cutting, you should check the air pressure flowing into the
cutting torch. Proper pressure should be specified in the instruction manual of your
machine. Most plasma cutters have a pressure gauge to monitor air pressure, as shown
in Figure 1.
Before cutting, make certain the workpiece is properly secured and your working lead,
if needed, is connected to the piece properly. The lead should be fairly close to the cut
and attached to a clean part of the workpiece. If the lead is attached to a dirty section,
proper cutting can be difficult. Make sure to grind off any additional rust or paint on the
surface, especially if using a lower power cutting machine.
Figure 1. Most plasma cutting machines have an
air pressure gauge.
Finally, inspect the cutting torch. Be certain the nozzle and electrode are in place. Check
your consumables for any added wear. Be certain all parts fit together properly as
shown in Figure 2 and are snug before beginning the cut.
Figure 2. The electrode, nozzle, and sheild should
fit together and attach snugly to the torch.
Lesson: 9/16
Steps for Cutting
With the workpiece and plasma cutting machine properly set up, you should
follow these steps to complete the cut:
1. Place the drag shield on the edge of the piece, or hold the torch at the
correct standoff distance from the piece if you do not have a drag shield.
Usually, this distance is 1/8 inch, although the manufacturer should have
recommendations for use.
2. Direct the torch straight down, so that the plasma emerges from the
torch
at a 90°
angle
to the
as shown in Figure 1.
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© 2009
Tooling
U, LLC.
All workpiece,
Rights Reserved.
3. Release any safety lock on the torch and press the trigger. This should
start the cutting arc.
4. Once the cutting arc starts, you can begin to slowly move the torch over
Lesson: 9/16
Steps for Cutting
With the workpiece and plasma cutting machine properly set up, you should
follow these steps to complete the cut:
1. Place the drag shield on the edge of the piece, or hold the torch at the
correct standoff distance from the piece if you do not have a drag shield.
Usually, this distance is 1/8 inch, although the manufacturer should have
recommendations for use.
2. Direct the torch straight down, so that the plasma emerges from the
torch at a 90° angle to the workpiece, as shown in Figure 1.
3. Release any safety lock on the torch and press the trigger. This should
start the cutting arc.
4. Once the cutting arc starts, you can begin to slowly move the torch over
the metal along the line you wish to cut.
5. Be certain to move the torch slow enough that sparks from the plasma arc
emerge from the bottom of the piece, as shown in Figure 2. Adjust your
speed as necessary.
6. As you reach the end of the cut, be sure to angle the torch slightly to cut
fully through the metal, or pause briefly until the piece is fully cut.
7. After you release the trigger, the torch will continue to pump gas for
cooling. Pressing the trigger during this period will immediately restart the
plasma arc.
Figure 1. The torch should be held at a 90° angle to the
workpiece.
This same basic procedure should be followed with any size or shape of cut.
Proper traveling speed depends mostly on the piece being cut and the strength
of the torch being used.
Figure 2. Be certain to move the torch slowly enough that
sparks emerge from the bottom of the workpiece.
Lesson: 10/16
Cutting Guides
When you are getting started using a plasma cutting machine, or if you know your
hand is not very steady, you may wish to use a cutting guide or a straight edge to
help you make better cuts. Cutting guides, shown in Figure 1, are separate tools that
attach to the torch and restrict movement of the torch.
For
your first
cuts,
you U,
should
focus
on Reserved.
straight cuts. A straight cutting guide allows
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© 2009
Tooling
LLC. All
Rights
the torch to move only in a straight line. This should allow you to become familiar with
using the torch without worrying about the straightness of your own cut.
Lesson: 10/16
Cutting Guides
When you are getting started using a plasma cutting machine, or if you know your
hand is not very steady, you may wish to use a cutting guide or a straight edge to
help you make better cuts. Cutting guides, shown in Figure 1, are separate tools that
attach to the torch and restrict movement of the torch.
For your first cuts, you should focus on straight cuts. A straight cutting guide allows
the torch to move only in a straight line. This should allow you to become familiar with
using the torch without worrying about the straightness of your own cut.
There are several other types of cutting guides that can help make more accurate
cuts. As shown in Figure 2, a circular guide works much like a compass, allowing the
torch to only move in a precise circle. A bevel cutting guide angles the torch, allowing
it only to cut at an angle to create the desired bevel in the finished cut.
Figure 1. Cutting guides are separate tools that
attach to the torch to restrict movement.
Straight edges can be any piece of metal clamped to the workpiece. Straight edges do
not restrict movement as much as a plasma torch, and are easier to attach and
remove quickly. Straight edges should only be used for making straight, even cuts.
Many operators, regardless of experience, regularly use guides to ensure perfect
cuts. Trickier cuts, such as bevels, are made much easier by the use of a guide. When
preparing for a cut, consider if a guide would make that cut easier or more regular.
Figure 2. A circular cutting guide helps a torch cut a
perfect circle.
Lesson: 11/16
Plasma Gouging
Plasma torches can also be used for gouging. Gouging is the removal of an old weld
or any imperfections in a workpiece by blasting them with the plasma torch.
To gouge a workpiece, make sure the piece is secure and prepared in the same
manner as for cutting. To perform the gouging, follow these steps:
1. Direct the torch at a 40° or 45° angle to the part of the piece being gouged
(Figure 1).
2. Release the safety lock on the torch and press the trigger. This should start
the pilot arc.
3. Once the cutting arc starts, you can begin to slowly move the torch over the
metal along the line you wish to gouge. Be sure to direct sparks away from you
and the torch.
4. Do not try to gouge too deeply on your first pass. Gouging often requires
multiple
passes
toU,
complete.
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© 2009
Tooling
LLC. All Rights Reserved.
Gouging is a useful process for correcting poor welds and fixing minor problems with
any workpiece.
Figure 1. The torch should be held at 45 degrees for
Lesson: 11/16
Plasma Gouging
Plasma torches can also be used for gouging. Gouging is the removal of an old weld
or any imperfections in a workpiece by blasting them with the plasma torch.
To gouge a workpiece, make sure the piece is secure and prepared in the same
manner as for cutting. To perform the gouging, follow these steps:
1. Direct the torch at a 40° or 45° angle to the part of the piece being gouged
(Figure 1).
2. Release the safety lock on the torch and press the trigger. This should start
the pilot arc.
3. Once the cutting arc starts, you can begin to slowly move the torch over the
metal along the line you wish to gouge. Be sure to direct sparks away from you
and the torch.
4. Do not try to gouge too deeply on your first pass. Gouging often requires
multiple passes to complete.
Gouging is a useful process for correcting poor welds and fixing minor problems with
any workpiece.
Figure 1. The torch should be held at 45 degrees for
plasma gouging.
Lesson: 12/16
Plasma Piercing
Plasma cutting machines can also be used to pierce metal. Piercing creates a hole in a
metal workpiece quickly. The procedure for plasma piercing is similar to gouging, with a
few minor differences. To pierce metal with a plasma cutting torch, follow these steps:
1. Direct the torch at a 40° or 45° angle to the part of the piece being pierced
(Figure 1).
2. Release the safety lock on the torch and press the trigger. This should start the
pilot arc.
3. Once the cutting arc starts, bring the tip to 90° to pierce through the workpiece
(Figure 2).
4. Once the piece is pierced, release the trigger and allow the torch to cool.
Using this method, plasma cutting machines can quickly and reliably pierce metals up
to half the thickness that they are recommended to cut. For example, a machine rated
to cut through 1/4 inch metal would be able to pierce metal up to 1/8 inch thick.
Piercing is hard on plasma cutting machines and consumables, and causes a reduction
in the life expectancy of the consumables.
Copyright © 2009 Tooling U, LLC. All Rights Reserved.
Figure 1. To begin piercing, hold the plasma torch
at a 45° angle to the location of the piercing.
Lesson: 12/16
Plasma Piercing
Plasma cutting machines can also be used to pierce metal. Piercing creates a hole in a
metal workpiece quickly. The procedure for plasma piercing is similar to gouging, with a
few minor differences. To pierce metal with a plasma cutting torch, follow these steps:
1. Direct the torch at a 40° or 45° angle to the part of the piece being pierced
(Figure 1).
2. Release the safety lock on the torch and press the trigger. This should start the
pilot arc.
3. Once the cutting arc starts, bring the tip to 90° to pierce through the workpiece
(Figure 2).
4. Once the piece is pierced, release the trigger and allow the torch to cool.
Using this method, plasma cutting machines can quickly and reliably pierce metals up
to half the thickness that they are recommended to cut. For example, a machine rated
to cut through 1/4 inch metal would be able to pierce metal up to 1/8 inch thick.
Piercing is hard on plasma cutting machines and consumables, and causes a reduction
in the life expectancy of the consumables.
Figure 1. To begin piercing, hold the plasma torch
at a 45° angle to the location of the piercing.
Figure 2. Once the cutting arc ignites, move the
torch to a 90° angle to pierce the metal.
Lesson: 13/16
Mechanized Plasma Cutting
Many CNC cutting tables have plasma cutters for performing complex cuts, such as
the one shown in Figure 1. These tables have traditionally been horizontal, but newer
technologies are allowing for vertical cutting tables as well. Though CNC-based plasma
cutting is more expensive than manual cutting, it offers a few advantages that many
companies find useful.
CNC plasma cutting equipment is capable of performing complex, multi-axis cutting of
thicker materials. This allows for more complex cuts than can be done by hand.
Copyright © 2009 Tooling U, LLC. All Rights Reserved.
CNC plasma cutting also offers a level of accuracy that hand cutting cannot. A hand
held plasma torch can be modified for use with a CNC cutting table using a special kit,
Lesson: 13/16
Mechanized Plasma Cutting
Many CNC cutting tables have plasma cutters for performing complex cuts, such as
the one shown in Figure 1. These tables have traditionally been horizontal, but newer
technologies are allowing for vertical cutting tables as well. Though CNC-based plasma
cutting is more expensive than manual cutting, it offers a few advantages that many
companies find useful.
CNC plasma cutting equipment is capable of performing complex, multi-axis cutting of
thicker materials. This allows for more complex cuts than can be done by hand.
CNC plasma cutting also offers a level of accuracy that hand cutting cannot. A hand
held plasma torch can be modified for use with a CNC cutting table using a special kit,
similar to the one shown in Figure 2. A well-programmed and maintained CNC plasma
cutter can reliably make the exact same cut repeatedly. For operations that need
multiple identical cuts, mechanized plasma cutting is essential.
The advantages of CNC plasma cutting have led to its wide adoption by the HVAC
industry. Ductwork requires numerous exact cuts to various metals. CNC plasma
cutting meets the strict specifications HVAC companies require.
The main disadvantage of CNC plasma cutting is that it is not ideal when working with
thin materials. When working with thin materials, most companies choose a laser
cutter.
Figure 1. A CNC plasma cutting table performs the
complex cut on this pipe.
Figure 2. A special kit can be used to modify
handheld plasma torches for use with CNC machines.
Lesson: 14/16
Basic Troubleshooting
Plasma cutting machines occasionally have problems. If your machine is cutting slowly or
wearing down too quickly, a few simple adjustments may fix the problem.
Unclean air being supplied to the torch can cause a lot of problems for the plasma torch.
Problems may appear in the cut itself, or in the extended wear of the consumables on the
torch. Electrode wear will appear as shown in Figure 1. Nozzle wear will appear as shown in
Figure 2. If a cut seems to be progressing too slowly, unclean air may be the cause. Check
your compressor to make sure all filters are clean. If you are using compressed air, switch to a
different tank, and see if the problem is resolved.
Another cause of premature consumable wear is improperly assembled torches. Replacing
consumables requires some disassembly of the torch. If the torch is not properly reassembled,
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with all parts fitting securely in place, the consumables may wear down too soon.
Though wear is expected of consumables, they should not wear prematurely. Manufacturers of
Figure 1. Electrodes showing different
degrees of wear.
Lesson: 14/16
Basic Troubleshooting
Plasma cutting machines occasionally have problems. If your machine is cutting slowly or
wearing down too quickly, a few simple adjustments may fix the problem.
Unclean air being supplied to the torch can cause a lot of problems for the plasma torch.
Problems may appear in the cut itself, or in the extended wear of the consumables on the
torch. Electrode wear will appear as shown in Figure 1. Nozzle wear will appear as shown in
Figure 2. If a cut seems to be progressing too slowly, unclean air may be the cause. Check
your compressor to make sure all filters are clean. If you are using compressed air, switch to a
different tank, and see if the problem is resolved.
Another cause of premature consumable wear is improperly assembled torches. Replacing
consumables requires some disassembly of the torch. If the torch is not properly reassembled,
with all parts fitting securely in place, the consumables may wear down too soon.
Figure 1. Electrodes showing different
degrees of wear.
Though wear is expected of consumables, they should not wear prematurely. Manufacturers of
plasma machines specify the average life of consumables in the machine manual. Ideally, all
consumables should be replaced simultaneously.
Figure 2. Nozzles showing different degrees
of wear.
Lesson: 15/16
The Advantages of Plasma Cutting
Plasma cutting has many advantages over the older oxyfuel method of cutting. Plasma
cutting simply cuts faster than oxyfuel. To cut with oxyfuel, metal must be preheated
by the torch before the cut can be performed. Plasma torches require no preheating.
Plasma is also able to cut any metal that conducts electricity. Oxyfuel cannot be used to
cut stainless steel or aluminum.
The cut made by a plasma torch is better for several reasons. The cut itself is much
more narrow, meaning less wasted metal for each cut. Plasma cutting affects less of an
area of the piece being cut, which means that it does less damage to the heataffected zone.
Plasma cutting offers some safety advantages that allow it to be used in a variety of
settings. Oxyfuel cutting uses explosive gases which must be properly handled at all
times. Plasma cutting uses only clean air, which even when compressed is not
explosive. If using compressed air, you must be careful to avoid puncturing the bottle.
Punctures cause high-pressure gas to be released very quickly, dangerously propelling
the bottle at high speeds.
In the past, plasma cutting machines were far more expensive than oxyfuel torches
and gas. However, recent advances in technology have lowered the cost of plasma
machines, making them far more affordable and cost effective. In addition, advanced
technologies
have
madeU,plasma
smaller and more portable than before, making
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Tooling
LLC. Allcutters
Rights Reserved.
using them anywhere much easier, as shown in Figure 1. Plasma cutting is becoming
more widely used than ever before because of their portability.
Figure 1. Plasma cutting machines are now smaller
Lesson: 15/16
The Advantages of Plasma Cutting
Plasma cutting has many advantages over the older oxyfuel method of cutting. Plasma
cutting simply cuts faster than oxyfuel. To cut with oxyfuel, metal must be preheated
by the torch before the cut can be performed. Plasma torches require no preheating.
Plasma is also able to cut any metal that conducts electricity. Oxyfuel cannot be used to
cut stainless steel or aluminum.
The cut made by a plasma torch is better for several reasons. The cut itself is much
more narrow, meaning less wasted metal for each cut. Plasma cutting affects less of an
area of the piece being cut, which means that it does less damage to the heataffected zone.
Plasma cutting offers some safety advantages that allow it to be used in a variety of
settings. Oxyfuel cutting uses explosive gases which must be properly handled at all
times. Plasma cutting uses only clean air, which even when compressed is not
explosive. If using compressed air, you must be careful to avoid puncturing the bottle.
Punctures cause high-pressure gas to be released very quickly, dangerously propelling
the bottle at high speeds.
In the past, plasma cutting machines were far more expensive than oxyfuel torches
and gas. However, recent advances in technology have lowered the cost of plasma
machines, making them far more affordable and cost effective. In addition, advanced
technologies have made plasma cutters smaller and more portable than before, making
using them anywhere much easier, as shown in Figure 1. Plasma cutting is becoming
more widely used than ever before because of their portability.
Figure 1. Plasma cutting machines are now smaller
than ever, allowing for portable use in any situation.
Lesson: 16/16
Summary
Plasma cutting is a method of cutting metal workpieces with a jet of air ionized by
an electric arc to create plasma. The size of a plasma cutting machine is described
by its amperage and voltage.
The four main components of a plasma cutting machine are the power supply, the
torch, the gas flow control, and the starter. The power supply is a DC power
source. The plasma cutting torch is the handheld unit used to cut the workpiece.
Two types of starters are used in plasma cutters, the high frequency contact
starter and the pilot arc starter. Gas flow control, in which the flow of air from a
compressor is regulated, is achieved with a flow control valve.
Safety is a priority any time you are working with a plasma cutting machine. Long
sleeves and leather gloves must be worn at all times when handling the plasma
torch. Eye protection is required for all plasma operations.
Preparing a cut before you begin a plasma cutting procedure can help ensure a
successful cut. When cutting, be sure to properly handle the torch and make a full
cut. A cutting guide can help you make a more precise cut if needed.
Plasma torches may also be used for gouging to remove unwanted welds or
imperfections in a workpiece. Holes can be pierced using a plasma cutting torch as
well. Plasma torches are also used with mechanized cutting machines.
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Wear to consumables is the main source of trouble in operating a plasma cutting
machine. Although plasma cutting machines have many advantages, proper care
Figure 1. Plasma cutting torches ionize air to create the
plasma cutting arc.
Lesson: 16/16
Summary
Plasma cutting is a method of cutting metal workpieces with a jet of air ionized by
an electric arc to create plasma. The size of a plasma cutting machine is described
by its amperage and voltage.
The four main components of a plasma cutting machine are the power supply, the
torch, the gas flow control, and the starter. The power supply is a DC power
source. The plasma cutting torch is the handheld unit used to cut the workpiece.
Two types of starters are used in plasma cutters, the high frequency contact
starter and the pilot arc starter. Gas flow control, in which the flow of air from a
compressor is regulated, is achieved with a flow control valve.
Safety is a priority any time you are working with a plasma cutting machine. Long
sleeves and leather gloves must be worn at all times when handling the plasma
torch. Eye protection is required for all plasma operations.
Preparing a cut before you begin a plasma cutting procedure can help ensure a
successful cut. When cutting, be sure to properly handle the torch and make a full
cut. A cutting guide can help you make a more precise cut if needed.
Figure 1. Plasma cutting torches ionize air to create the
plasma cutting arc.
Plasma torches may also be used for gouging to remove unwanted welds or
imperfections in a workpiece. Holes can be pierced using a plasma cutting torch as
well. Plasma torches are also used with mechanized cutting machines.
Wear to consumables is the main source of trouble in operating a plasma cutting
machine. Although plasma cutting machines have many advantages, proper care
and maintenance will ensure a long life to offset the high initial cost of the machine
itself.
Figure 2. Make certain that sparks are coming out of
the bottom of the workpiece, or else it is not being
properly cut.
Class Vocabulary
Term
Definition
air compressor A component that pressurizes ambient air and directs it into a plasma cutting machine.
air flow control The regulation of air flowing from an air compressor. Gas flow control is achieved with a flow control valve.
amperage A measurement that indicates the amount of current flowing in a circuit, which is measured in amperes.
arc welding A welding process that uses heat generated from electricity to melt filler metal and base metals to form an airtight weld.
consumables Any part of a plasma cutting machine that may wear over time and usage. Nozzles and electrodes are the two main
consumables, though some torches have others.
cutting arc A stream of plasma used to cut metal workpieces. The cutting arc is formed by an electrode superheating air pumped
into the torch.
cutting guide A device that attaches to the plasma torch and restricts the movement of the torch to ensure proper cutting.
drag shield A shield that mounts on the front of a plasma torch in order to prevent it from getting too close to the workpiece.
electrode A device that conducts electricity. In plasma cutting, electrodes are one of the two main types of consumables.
filter plate The shaded protective lens inside a helmet that filters harmful rays and intense bright light.
flow control valve A valve that allows an operator to precisely control the amount of air pressure being supplied to the torch.
gouging The use of a plasma cutting torch to remove an old weld or any imperfections in a workpiece.
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heat-affected zone Also known as the HAZ. The area around a cut affected by the heat of the plasma torch. Plasma cutting does much less
damage to the heat-affected zone than oxyfuel cutting.
high frequency A type of plasma cutting machine starter that uses high voltage circuits to start the arc. High frequency contact starters
Class Vocabulary
Term
Definition
air compressor A component that pressurizes ambient air and directs it into a plasma cutting machine.
air flow control The regulation of air flowing from an air compressor. Gas flow control is achieved with a flow control valve.
amperage A measurement that indicates the amount of current flowing in a circuit, which is measured in amperes.
arc welding A welding process that uses heat generated from electricity to melt filler metal and base metals to form an airtight weld.
consumables Any part of a plasma cutting machine that may wear over time and usage. Nozzles and electrodes are the two main
consumables, though some torches have others.
cutting arc A stream of plasma used to cut metal workpieces. The cutting arc is formed by an electrode superheating air pumped
into the torch.
cutting guide A device that attaches to the plasma torch and restricts the movement of the torch to ensure proper cutting.
drag shield A shield that mounts on the front of a plasma torch in order to prevent it from getting too close to the workpiece.
electrode A device that conducts electricity. In plasma cutting, electrodes are one of the two main types of consumables.
filter plate The shaded protective lens inside a helmet that filters harmful rays and intense bright light.
flow control valve A valve that allows an operator to precisely control the amount of air pressure being supplied to the torch.
gouging The use of a plasma cutting torch to remove an old weld or any imperfections in a workpiece.
heat-affected zone Also known as the HAZ. The area around a cut affected by the heat of the plasma torch. Plasma cutting does much less
damage to the heat-affected zone than oxyfuel cutting.
high frequency A type of plasma cutting machine starter that uses high voltage circuits to start the arc. High frequency contact starters
contact starter can cause interference with other machines and tend to only be part of older plasma cutting machines.
HVAC Heating, Ventilating, and Air Conditioning. The HVAC industry is responsible for the installation and maintenance of
various climate control systems.
inches per minute A unit of measurement for feed that indicates how many inches the plasma cutting machine can travel in one minute.
infrared Invisible rays emitted during the plasma cutting process. Infrared rays can damage vision.
inverter A newer technology in some plasma machines that saves space while allowing for higher voltage by converting AC power
to DC power.
multi-axis Able to move along more than one linear axis, including additional rotational axes. A multi-axis CNC cutting table is able
to cut complex shapes on multiple axes, instead of just straight lines.
nozzle The part of the plasma cutting torch at the tip that directs gas into a narrow cone around the electrode. Nozzles are
one of the two main consumables in a plasma torch.
oxyfuel A mix of oxygen and a fuel gas that is used to fuel a flame for welding and cutting metal.
piercing The use of a plasma cutting torch to create a hole in a metal workpiece quickly.
pilot arc starter A type of plasma cutting machine starter that uses the contact between the nozzle and electrode to create a pilot arc.
When gas flows into the torch, it separates the nozzle from the electrode, and the arc between the two causes plasma
to form.
plasma The fourth state of matter that is created by superheating a gas.
plasma cutting A method of cutting metal workpieces with a jet of air, ionized by an electric arc to create plasma.
power supply The device that provides DC power to the plasma cutting machine.
safety lock A part of a plasma torch designed to prevent the trigger from accidentally being pressed. Safety locks differ between
torch models.
starter The method by which the plasma cutting machine starts the formation of plasma. Starters may be either high frequency
contact starters or pilot arc starters.
state of matter The form matter takes, depending mostly on temperature and pressure. The states of matter are solid, liquid, gas, and
plasma.
superheated Rapidly raised in temperature. Superheating gas causes it to become plasma.
torch The handheld unit used to cut the workpiece. Air is pumped into the torch and converted to plasma at the tip of the
torch.
ultraviolet Harmful invisible rays emitted by the arc during plasma cutting. UV rays can damage vision and burn skin.
voltage A measure of electrical pressure or potential known as electromotive force. Voltage is measured in volts.
working lead The path used in some plasma cutting to conduct electricity from the machine to the workpiece. Working leads are
required with high frequency contact starters.
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