Air Diffuser
Electrode
Shield Cap
Plasma Stream
Tip
Elecrode Insert
Plasma cutters work by passing an electric arc through a gas that is passing through a constricted opening.
The electric arc elevates the temperature of the gas to the point that it enters a 4th state of matter. We all are
familiar with the first three: i.e., Solid, liquid, and gas. Scientists call this additional state plasma. As the metal
being cut is part of the circuit, the electrical conductivity of the plasma causes the arc to transfer to the work.
The restricted opening (Tip) the gas passes through causes it to squeeze by at high speed, like air passing
through a venturi in a carburettor. This high-speed gas cuts through the molten metal. Plasma cutting was
invented as a result of trying to develop a better welding process. Many improvements then led to making this
technology what it is today. Plasma cutters provide the best combination of accuracy, speed, and affordability
for producing a variety of flat metal shapes. They can cut much finer and faster than oxy-acetylene torches.
How a plasma cutter works:
Basic plasma cutters use electricity to superheat air into plasma (the 4th state of matter), which is then blown
through the metal to be cut. Plasma cutters require a compressed air supply and AC power to operate.
Operation:
1.
When the trigger is squeezed, DC current flows through the torch lead into the tip.
2.
Next, compressed air flows through the torch head, through the air diffuser that spirals the airflow around
the electrode and through the hole of the cutting tip.
3.
A fixed gap is established between the electrode and the tip. (The power supply increases voltage in order
to maintain a constant current through the joint.) Electrons arc across the gap, ionizing and superheating
the air creating a plasma stream.
4.
Finally, the regulated DC current is switched so that it no longer flows to the tip but instead flows from the
electrode to the workpiece. Current and airflow continue until cutting is stopped.
The nozzle and electrode require periodic replacement. The electrode has an insert of a tough high
conductive material such as hafnium and cerium. This insert erodes with use; also, the tip orifice will erode
with use. Quality of the air used is paramount to longer life of electrodes and tips, in short, clean dry air gives
more extended parts life, the cleaner and dryer the better. We recommend the use of a Plasma Air Filter.
What kinds of materials can the plasma cut?
Virtually any metal can be plasma cut including steel, stainless steel, aluminium, brass, copper, etc. Any
thickness from 30 gauge through 30mm can be cut, depending on the power of the plasma cutter used.
How Does Plasma Cutting Compare to Oxy-fuel (gas) cutting?
Plasma cutting can be performed on any conductive metal - mild steel, aluminium and stainless are some
examples. With mild steel, operators will experience faster, thicker cuts than with alloys.
Oxy-fuel cuts by burning, or oxidizing the metal it is severanceing. It is therefore limited to steel and other
ferrous metals which support the oxidizing process. Metals like aluminium 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 aluminium, stainless and any other conductive material.
While different gasses can be used for plasma cutting, most people today use compressed air for the plasma
gas. In most shops, compressed air is readily available, and thus plasma does not require fuel gas and
compressed oxygen for operation.
Plasma cutting is typically more accessible for the novice to master, and on thinner materials, plasma cutting
is much faster than oxy-fuel cutting. However, for heavy sections of steel (25mm and greater), oxy-fuel is still
preferred since oxy-fuel is typically faster and, for heavier plate applications, high powered plasma machines
are required for plasma cutting applications.
What are the limitations to Plasma Cutting? Where is Oxy-fuel preferred?
The 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 (>25mm) of steel more quickly than plasma.
PLASMA CUTTING TECHNOLOGY
15
Summary of Contents for VIPER CUT 30Mk II
Page 2: ...2...
Page 23: ...NOTES 23...
