Plasma Cutting 265. Class Outline

Plasma Cutting 265 Welcome to the Tooling University. This course is designed to be used in conjunction with the online version of this class. The on...
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Plasma Cutting 265

Welcome to the Tooling University. This course is designed to be used in conjunction with the online version of this class. The online version can be found at http://www.toolingu.com. We offer high quality web -based e -learning that focuses on today's industrial manufacturing training needs. We deliver superior training content over the Internet using text, photos, video, audio, and illustrations. Our courses contain "roll -up -your -sleeves" content that offers real -world solutions on subjects such as Metal Cutting, Workholding, Materials, and CNC with much more to follow. Today's businesses face the challenge of maintaining a trained workforce. Companies must locate apprenticeship programs, cover travel and lodging expenses, and disrupt operations to cover training needs. Our web -based training offers low -cost, all -access courses and services to maximize your training initiatives.

 

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 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

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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.

 

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. Copyright © 2009 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. Copyright © 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 Copyright © 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. Copyright © 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, Copyright © 2009 Tooling U, LLC. All Rights Reserved. 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 Copyright © 2009 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. Copyright © 2009 Tooling U, LLC. All Rights Reserved. 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. Copyright © 2009 Tooling U, LLC. All Rights Reserved. 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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