Make it Work

PLASMA CUTTING

GUIDEPLASMA CUTTING

GUIDE

CONTENTS

Air plasma cutting technology explained . . . . . . . . . . . . . . . . . . . . . . . . . . 1

How a plasma cutter works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

How does plasma cutting compare to oxy-fuel (gas) cutting? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

What are the limitations to plasma cutting? . . . . . . . . . . . . . . . . . . . . . 2

What kinds of materials can the plasma cut? . . . . . . . . . . . . . . . . . . . 2

What thickness of materials can the plasma cut? . . . . . . . . . . 2

Duty cycle explained . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Torch assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

What is a 2t or 4t torch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Operating procedure for plasma cutting . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Tech tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Cut quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Amperage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Direction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Torch tip height and position . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Tip size and condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Electrode condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Air pressure and volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Air quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Buying considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Maintenance schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1

AIR PLASMA CUTTING TECHNOLOGY EXPLAINED Plasma cutters work by passing an electric arc through a gas that is passing through a constricted opening. The gas can be air, nitrogen, argon, oxygen, etc. The electric arc elevates the temperature of the gas to the point that it enters a 4th state of matter known as plasma. The restricted opening (nozzle) the gas passes through causes friction at a high speed. This restricted, high speed gas is what cuts through the molten metal. As the metal being cut completes the circuit, the electrical conductivity of the plasma causes the arc to transfer to the work.

HOW A PLASMA CUTTER WORKS

Plasma cutters require a compressed air supply and AC input power to operate.

Basic Operation:• When the trigger is squeezed, DC current flows through

the torch lead into the nozzle.• Next, compressed air flows through the torch head, through

the air diffuser that spirals the air flow around the electrode and through the hole of the cutting nozzle.

• A fixed gap is established between the electrode and the nozzle which allows electrons to arc across the gap, ionizing and super heating the air creating a plasma stream.

• Finally, the regulated DC current is switched automatically so that it no longer flows to the nozzle but instead flows from the electrode to the workpiece.

• Current and airflow continue until cutting is stopped.

HOW DOES PLASMA CUTTING COMPARE TO OXY-FUEL (GAS) CUTTING?

Plasma cutting can be performed on any type of conductive metal - mild steel, aluminum and stainless steel are some examples. Oxy-fuel cuts by burning, or oxidizing the metal it is severing. It is therefore limited to steel and other ferrous metals which support the oxidizing process. Metals like aluminum and stainless steel form an oxide that inhibits further oxidization, making conventional oxy-fuel cutting impossible. Plasma cutting however does not rely on oxidation to work and thus it can cut aluminum, stainless and any other conductive material. Plasma cutting is typically easier for the novice to master, and on thinner materials, plasma cutting is much faster than oxy-fuel cutting.

Electrode Insert

Nozzle

Plasma Stream

Air Diffuser

Electrode

Shield Cup

2

WHAT ARE THE LIMITATIONS TO PLASMA CUTTING?

Plasma cutting machines are typically more expensive than oxy/acetylene. Also, oxy/acetylene does not require access to electrical power or compressed air which may make it a more convenient method for some users. Oxy-fuel can generally cut thicker sections (>63/64 inch) of steel more quickly than plasma.

WHAT KINDS OF MATERIALS CAN THE PLASMA CUT?

All conductible metal material can be cut, including steel, copper, iron, brass, stainless steel and even dissimilar metals and alloys. For example, you can cut alloy that is sitting on steel for instance, but it will affect your cutting speed.

WHAT THICKNESS OF MATERIALS CAN THE PLASMA CUT?

The maximum thickness of a cut or rated cut capacity of metal depends on the power of the plasma cutter used. The maximum cut thickness for each plasma cutter is found under rated cut capacity and rated sever capacity on the product specifications.• Rated cut capacity is the maximum cut depth the specific

machine can cut cleanly. • Rated sever capacity is the maximum cut depth (rough cut)

of a given machine.

DUTY CYCLE EXPLAINED

The plasma cutter’s duty cycle rating defines how long the operator can cut before allowing the unit to cool. The duty cycle is a percentage of a 10 minute period. The plasma cutter must cool for the remainder of the cycle. For example, a plasma cutter with a duty cycle rating of 30% at the rated output, means that the user can cut for 3 minutes and then rest the unit for 7 minutes before using it again.

TORCH ASSEMBLY

The plasma torch consists of 4 main parts (below) and each needs to be installed and seated correctly for the torch to function. All torch assembly parts are consumables and will need to be replaced throughout the life span of the plasma cutter.*torch assembly configurations may vary from machine to machine

Nozzle ElectrodeRetaining Cap Swirl Ring

Note: torch assembly configurations may vary from machine to machine

3

WHAT IS A 2T OR 4T TORCH?

A 2T Torch is a simple on-and-off torch. Press the trigger for pilot and cutting arc, release and it turns off.A 4T torch requires the user to press the trigger to initiate the pilot and cutting arc and once the cutting arc is established the trigger can be released and as long as the cutting arc continuity is kept, the torch will keep cutting. To end the process depress the trigger again and release to end the cutting cycle.

OPERATING PROCEDURE FOR PLASMA CUTTING

Caution: Always wear face and hand protection when plasma cutting. The plasma cutting process produces very hot particles which are forced away from the cutting piece using air as the cutting and cooling medium. This superheated air must be treated with extreme caution.

Put on safety gear - Generally you want the same type of protective gear as when welding:• Leather welding gloves • Leather or FR welding jacket • Full length pants • Industrial grade approved footwear • Welding spats• Eye protection – A face shield or welding mask with a DIN

shade #5 is the minimum eye protection, with other shades required depending on amperage.

Grounding - Connect the Earth Clamp securely to the workpiece or the work bench.

Positioning - Place and hold the torch at a vertical angle at the edge of the plate.

Piercing - Pull the trigger to energize the pilot arc and slowly rotate it to an upright position. The cutting arc will start when the nozzle is moved closer to the edge of the workpiece. When the cutting arc has cut through the edge of the workpiece start moving evenly in the direction you wish to cut.

Correct amperage and travel speed - are important and relevant to material thickness and are correct when sparks are exiting from the workpiece. If sparks are spraying up from the workpiece there is insufficient amps selected or the travel speed is too fast.

Finish the cut - by releasing the torch switch. The air flow will continue for 30 seconds to cool the torch head.

4

TECH TIPS• It is easier to pull the torch

through the cut than to push it.• To cut thin material, reduce

the amperage until you get the best quality cut.

• Use the correct size tip orifice for the amperage being used.

• For straight cuts use a straight edge or cutting buggy as a guide. For circles, use a template or circle cutting attachment.

• Use a Standoff guide that mounts to the plasma torch. The feet of the standoff guide are placed on the cutting surface and maintains an optimal 5/64 in. distance between the cutting tip and the work, this is especially suitable if your hands are unsteady. It also helps extend tip life.

CUT QUALITYCut quality depends on several factors:• Amperage • Travel speed• Tip height and position • Tip and electrode quality• Air pressure and techniqueThe best quality cut will be produced when all these variables are set correctly for the material thickness and type of material being cut.

Cutting Buggy

Standoff Guide

AMPERAGE• Standard rule of thumb is the thicker the material the more

amperage required.• On thick material, set the machine to full output and vary

your travel speed.• On thinner material, you need to turn down the amperage and

change to a lower-amperage tip to maintain a narrow kerf. The kerf is the width of the cut material that is removed during cutting.

SPEED• Amperage and speed are critical to producing a good quality

cut. The faster you move (especially on aluminum), the cleaner your cut will be.

• To determine if you’re going too fast or too slow, visually follow the arc that is coming from the bottom of the cut. The arc should exit the material at a slight angle away from the direction of travel.

• If it’s going straight down that means you’re going too slow, and you’ll have an unnecessary buildup of dross or slag.

• If you go too fast, it will start spraying back onto the surface of the material without cutting all the way through.

• Because the arc trails at an angle, at the end of a cut slow your cutting speed and angle the torch in to cut through the last bit of metal.

Poor quality cut Good quality cut

5

DIRECTION

• It is easier to pull the torch towards you than push it. • The plasma stream swirls as it exits the tip, biting one side

and finishing off on the other leaving a beveled edge and a straight edge.

• The bevel cut effect is more noticeable on thicker material and needs to be taken into consideration before starting your cut as you want the straight side of the cut to be on the finished piece you keep.

TORCH TIP HEIGHT AND POSITION

• The distance and position of the plasma torch cutting tip has an effect on the quality of the cut and the extent of the bevel of the cut.

• The easiest way to reduce bevel is by cutting at the proper speed and height for the material and amperage that is being cut.

TIP SIZE AND CONDITION

• The nozzle and electrode are consumable parts of the plasma cutter – replace them all at the same time.

• The nozzle will need to be replaced when the cutting orifice has enlarged or if it has a “notched” appearance.

• Always ensure your tips are not worn before you start your cut.

New Tip Worn Tip

ELECTRODE CONDITION

• The electrode contains an insert in the end made of a highly conductive material called hafnium.

• The electrode insert erodes with use and develops a pit in the end; a concave or rough surface on the electrode will result in poor cut quality. When this occurs replacement of the electrode is necessary.

New Electrode Worn Electrode

Correct torch height and square to the material. Minimum bevel & equal bevel. Longest consumable life.

Torch angled to the material. Unequal bevel, one side may be excessively beveled.

Torch height too high. Excessive bevel, plasma steam may not cut all the way through the material.

Torch height too low. Reverse bevel. Tip may contact the work and short out or damage the tip.

6

AIR PRESSURE AND VOLUME• Air pressure, flow rate and air quality are critical to quality

plasma cutting and consumable life span. • The required air pressure and volume can vary from model

to model and the manufacturer will provide the proper specification measured in Cubic Feet/Minute or (CFM).

• The volume capacity of your compressor is VERY important, it is recommended you use a compressor with a CFM rating slightly higher than the plasma cutter requires to avoid burning out your compressor from continuous operation.

• If you are doing a lot of thick plate cutting (same air consumption but slower cut speeds = longer cut time) then choose a compressor at 1.5 to 2 times the plasma system requirement.

AIR QUALITY• Good air quality is essential to quality plasma cutting and

consumable life span. • Humidity in the air is condensed in the tank and in the airlines,

producing water.• Moisture that forms in air lines has a tendency to condense

into larger drops when the air pressure decreases as it is entering the plasma torch causing the cutter to malfunction.

BUYING CONSIDERATIONS• Cut Thickness: Determine thickness of material you require

to cut – most entry level plasma cutters will be able to cut 1/8 in. to 1/4 in. and professional level cutters will cut and sever up to 3 in.

• In order to cut thicker materials a more powerful plasma cutter will be needed.

• Amperage Output: the higher the unit’s rated amperage, the more powerful the unit is to handle thicker cuts.

• Amperage draw: ensure your power circuit can handle the amperage draw as to not trip your breaker.

• Most entry level plasma cutters draw 15A - 20A and will work on a standard household 20A circuit, where professional level machines typically draw 30A – 60A and require a 230V circuit.

• Input Power 115V/230V: determine if the unit uses a 110V plug or requires a 230V plug.

• Air compressor: ensure you check the plasma cutter’s CFM requirement so you can ensure you buy or use an air compressor large enough to generate what the plasma cutter requires to work.

• Most plasma cutters require a large air compressor that can generate at least 6 CFM.

• An alternate consideration to forgo the larger air compressor is to buy a plasma cutter that has a built – in air compressor which are only found in the entry level range.

• Safety gear: ALWAYS WEAR PROPER SAFETY GEAR BEFORE USING A PLASMA CUTTER

• This includes a welding helmet, leather or flame retardant (FR) clothing, approved covered footwear, and welding gloves.

7

TROUBLESHOOTING

Visit a Princess Auto location for a solution if the plasma cutter does not function properly or parts are missing. If unable to visit the store, have a qualified technician service the unit.

Issue Possible Causes Suggested Solutions

Pilot plasma is not stable

during operation

Compressed air is too low or too high

Adjust pressure

Electrode of cutting torch or nozzle is burnt

Replace electrode or nozzle

Connection between ground cable and workpiece is poor

Connect firmly

Cutting speed is too slow

Adjust speed

Cut is at wrong angle

Nozzle or electrode is burnt

Replace nozzle or electrode

The installation position of nozzle and electrode do not match

Correctly install both

Cutting speed is too high

Slow down cutting speed

Nozzle axis is not plumb with the plane

Adjust the torch angle

Cut is too wide, cut quality is

poor

Cutting speed is too slow

Accelerate cutting speed

Torch’s electrode or nozzle is burnt

Replace electrode or nozzle

Cutting speed is too high

Slow cutting speed

Wrong type of nozzle used

Replace with a suitable nozzle

Workpiece is not cut through

The cutting speed is too rapid

Slow down the cutting speed

Torch electrode or nozzle is burnt out

Replace electrode or nozzle

Cut thickness exceeds the limit of the cutting unit

Use a high-power plasma cutting unit

Cutting mouth is not vertical

Adjust cutting mouth angle

Leak from the gas circuit reduces gas/air flow

Examine and repair the gas circuit

8

Issue Possible Causes Suggested Solutions

Why can’t I get a

straight cut?

Unsteady body mechanics

Try using a straight edge and a smooth pulling motion with consistent speed when moving the torch.

I pull the trigger but

nothing happens, what am I

doing wrong?

Improper torch assembly

Ensure the torch retaining cap is fully seated and that the 2 pins under the cap are making contact with the retaining cap to allow the torch head to fire a pilot arc.

Improper torch assembly

Do not over tighten the retaining cap - the 2 safety pins can be pushed into the housing and will not make contact and allow the torch to fire.

Poor connectivity to workpiece

Check your ground clamp lead is attached securely to ensure good conductivity.

I get a pilot arc and when I try cutting it

won’t cut, then stops

Electrode tip is not at optimal distance form workpiece

When initiating the pilot arc, have the electrode tip close to the workpiece without touching it. The optimal gap between the electrode tip and the workpiece is 2-3 mm. The pilot arc only fires for 3-5 seconds before it will extinguish. If the machine does not make continuity to complete the circuit then the pilot arc will not transfer to a cutting arc.

Why aren’t my electrodes

and nozzles lasting very

long?

Operating machine above recommended amps for a particular cut

Reduce cutting amps until machine just cuts through workpiece. Using the machine at amps higher than what is required to make the cut is hard on consumables. Refer to the user manual for proper amperages to use.

Electrode is too close to workpiece

Ensure that the cutting nozzle to surface gap is maintained to ensure slag and dross are not plugging the cutting nozzle orifice.

Excessive heat in nozzle and electrode

Use extra cooling time after cutting thicker materials. Heat in the nozzle and electrode will always erode the consumables quicker and shorten their overall life.

Excessive heat in nozzle and electrode

Using the air check selector for 30 – 60 seconds after a cut will lengthen consumable life.

Poor compressed air quality

Always use clean dry air.

9

MAINTENANCE SCHEDULE

This schedule is based on the assumption that your machine will be used for its designed purpose.Sustained high-load or high-temperature operation or use in unusually wet or dusty conditions, will require more frequent service.

FREQUENCY MAINTENANCE

Daily examination

Check to make sure that the knob and switches on the front and back panels of the plasma cutting unit are working and correctly set. Replace a switch or knob that is not working or cannot be set correctly.

Turn the cutting unit on and note if it is shaking, making any strange sounds or emitting odours. If there is one of the above problems, have a qualified technician repair the cutting unit.

Check that the fan rotates and is undamaged. Check for and remove anything blocking the fan if it doesn’t rotate. Have a qualified service technician repair a damaged fan.

Check that all cable and hose connections are tight. Tighten if loose. If unable to tighten, replace the connector.

Check to see if the current output cable is damaged. If it is damaged, have the output cable replaced by a qualified service technician.

Monthly examination

Use dry, compressed air to clear the inside of the cutting unit. Make sure to blow out dust from the internal components.

Make sure that all hardware is securely tightened on the cutting unit.

Quarterly examination

Check to make sure that the current matches the specifications. Measure with clamp multi-meter. Have the cutting unit serviced if the amperage or voltage is not correct.

Annual examination

Measure the insulating impedance among the main circuit, PCB and case; if it is below 1MΩ, the insulation may be damaged and must be replaced.

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