PLASMA CUTTING

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PLASMA CUTTING
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A. The Plasma Cutter

• Been around since World War II.
• Conceptually, a very simple tool.
• Harnesses one of most prevalent
• states of matter in universe - PLASMA

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B. New Discoveries

• Inert gas fed through an electric arc.
• Breakthrough discovery Charging gas with
• electric current formed barrier around weld.
• Made cleaner joints sturdier construction.
• Early 1960s boosted temperature by
• speeding up flow shrinking release hole.
• At higher temp, tool acted like a cutter
  instead
• of a welder.

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C. What is Plasma ?

• Boosting a gas to extremely high temperature
• produces plasma.
• Gas molecules begin to break apart, atoms
• begin to split nuclei become ions.
• Ions collide with other nuclei and ions.
• Collision releases vast amounts of energy.

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C. What is Plasma ?

• Plasma is Everywhere
• 99 of all matter in universe is plasma.
• Not common on Earth normal on the Sun.
• Present in lightning.
• Neon lights, fluorescent lighting, plasma
• displays use cool plasma.

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D. Inside a Plasma Cutter

• Cutters
• Electrode in center nozzle just below it.
• Swirl ring causes plasma to turn rapidly.
• All sizes hand held or large industrial.

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D. Inside a Plasma Cutter

• 2. Making Plasma
• Sending pressurized gas nitrogen, argon,
• oxygen through a small channel.
• Applying power to negatively charged
• electrode a creates electric circuit.
• Heat causes gas to reach fourth state of
• matter - PLASMA.
• Creates stream of plasma 30,000o F
• moving at 20,000 feet per second.

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D. Inside a Plasma Cutter

• 3. Plasma Cutting Technology
• Superheated, compressed air.
• Ionizes to form conductive gas.
• Gas conducts electricity from plasma
• cutter to work piece.
• Arc melts and blows away metal.

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1. Plasma Cutting Technology

• How Does Plasma Compare to Oxyacetylene ?
• Oxyacetylene slowly burns through metal
  limited
• to steel and other ferrous metals.
• Plasma melts metal and blows it away.
• Plasma does not require use of flammable or
• explosive materials.
• Drawbacks to Plasma
• More expensive
• Requires access to electricity compressed air.

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1. Plasma Cutting Technology

• Thickness
• Most units rated on cutting ability and
  amperage.
• Smaller units make sever cut leaves
  behind
• dross and slag.
• ¼- inch machine has about 25 amps output
• ½-inch machine has 50-60 amp output.
• ¾ to 1-inch machine has 80 amp output.

• Cutting Speed
• Good rule of thumb Choose machine that can
• handle approx. twice your normal cutting
  thickness.
• Duty cycle Time you can continuously cut
  before
• machine overheats.

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1. Plasma Cutting Technology

• Initiating the Cutting Arc
• Most units have a pilot arc utilizing high
  frequency.
• High frequency may interfere with computers.

• Consumables
• Parts that wear out or supplies that get used
  up.
• Make sure to compare same data between
  machines.

• Arc Transfer
• Transfer occurs when pilot arc is close to
  work piece.
• After arc transfers, a switch opens current
  path.
• Quick transfer to cutting, with larger
  transfer height.

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1. Plasma Cutting Technology

• Maintaining Efficiency
• Filters remove oil from compressed air.
• Oil can cause arcing and reduce cutting
  ability.

• Before starting, check for
• Clean air supply without water or oil.
• Consumable wear and burn marks.
• Correct air pressure.
• Nozzle and electrode in correct place.
• Clean ground connection.

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4. Plasma Cutting Safety
Machine should have Nozzle in Place sensor.
Plasma cutter will not start an arc unless
nozzle is there. Look for pre-flow sequence and 3
second pre-flow safety.

• Basic Safety Practices
• Read instruction manual thoroughly.
• Always wear long sleeves and gloves.
• Dark goggles or weld shield required. Shade
  7 - 9
• Discuss all tips and guidelines in your
  manual.