Guide to Plasma Arc Equipment

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Guide to Plasma Arc Equipment

Summary:

The plasma arc cutting process requires equipment that is within reach from a price and difficulty perspective for hobbyists and welding shops.

Plasma arc equipment includes:

  • torch: small units are air-cooled and larger units are water cooled
  • electrode tip: copper and tungsten
  • nozzle insulator: between the electrode tip and nozzle tip
  • a control unit
  • a power supply
  • one
    or more cutting gases
  • supply of clean cooling water
  • regulator assembly containing a pressure regulator to control pounds per square inch of gas used

Equipment
is relatively small in size and is available for both manual and mechanized PAC.

Plasma Arc Equipment

Inverter-based economical plasma cutting system from Hobart. Operates from both a 230 and 115 VAC through a standard household outlet.
Shown: Hobart 500548 Airforce 500i 115/230 Volt Plasma Cutter

Plasma Arc Equipment

Plasma Arc Cutting In Action

Professional Engaged in the Plasma Arc Cutting Process

It's important to note that used machinery equipment can and should be an alternative you look at before buying new.

Plasma Cutting Torch

A cutting torch consists of an electrode holder which centers the
electrode tip with respect to the orifice in the constricting nozzle.
The electrode and nozzle are water cooled to prolong their lives. Plasma
gas is injected into the torch around the electrode and exits through
the nozzle orifice. Nozzles with various orifice diameters are available
for each type of torch. Orifice diameter depends on the cutting
current; larger diameters are required at higher currents. Nozzle design
depends on the type of PAC and the metal being cut.

Both single and
multiple port nozzles may be used for PAC. Multiple port nozzles have
auxiliary gas ports arranged in a circle around the main orifice. All of
the arc plasma passes through the main orifice with a high gas flew
rate per unit area. These nozzles produce better quality cuts than
single port nozzles at equivalent travel speeds. However, cut quality
decreases with increasing travel speed. Torch designs for introducing
shielding gas or water around the plasma flame are available. PAC
torches are similar in appearance to gas tungsten arc welding electrode
holders, both manual and machine types. Mechanized PAC torches are
mounted on shape cutting machines similar to mechanized oxyfuel gas
shape cutting equipment. Cutting may be controlled by photoelectric
tracing, numerical control, or computer.

Plasma Arc Cutting Equipment Diagram

Plasma Arc Cutter Equipment Schematic Diagram

Plasma Arc Equipment Controls

Control consoles for PAC may contain solenoid valves to turn gases and
cooling water on and off. They usually have flow-meters for the various
types of cutting gases used and a water flow switch to stop the
operation if cooling water flow falls below a safe limit. Controls for
high-power automatic PAC may also contain programming features for
up-slope and down slope of current and orifice gas flow.

Power Sources

Power sources for PAC are specially designed units with open-circuit
voltages in the range of 120 to 400 V. A power source is selected on the
basis of the design of PAC torch to be used, the type and thickness of
the work metal, and the cutting speed range. Their volt-ampere output
characteristic must be the typical drooping type.

  • Heavy cutting requires high open-circuit voltage (400 V) for
    capability of piercing material as thick as 2 in. (51 mm). Low current,
    manual cutting equipment uses lower open-circuit voltages (120 to 200
    V). Some power sources have the connections necessary to change the
    open-circuit voltage as required for specific applications.
  • The output current requirements range from about 70 to 1000 A
    depending on the material, its thickness, and cutting speed. The unit
    may also contain the pilot arc and high frequency power source
    circuitry.

Plasma Arc Equipment

50 Amp Digital Inverter Air Plasma Cutter. Can Cut any kind of metal, including Aluminum.

Shown: LT5000D Lotos LT5000D 50A Air Inverter Plasma Cutter Dual Voltage 110/220VAC 1/2" clean Cut

Gas Selection

Cutting gas selection depends on the material being cut and the cut
surface quality requirements. Most nonferrous metals are cut by using
nitrogen, nitrogen-hydrogen mixtures, or argon-hydrogen mixtures.
Titanium and zirconium are cut with pure argon because of their
susceptibility to embrittlement by reactive gases.

(Carbon steels are cut by using compressed air (80 percent N2, 20 percent 02)
or nitrogen for plasma gas. Nitrogen is used with the water injection
method of PAC. Some systems use nitrogen for the plasma forming gas with
oxygen injected into the plasma downstream of the electrode. This
arrangement prolongs the life of the electrode by not exposing it to
oxygen.

For some nonferrous cutting with the dual flow system, nitrogen is used for the plasma gas with carbon dioxide (C02) for shielding. For better quality cuts, argon-hydrogen plasma gas and nitrogen shielding are used.

For Additional Reading

Overview of Plasma Arc Cutting

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Page Author: Jeff Grill