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AN EXPLANATION OF THE
PROCESS
Plasma cutting is a process that is used to
cut steel and other metals of different thicknesses (or sometimes other materials) using a plasma
torch. In this process compressed air is blown at high speed out of a nozzle; at the same time an
electrical arc is formed through that gas from the nozzle to the surface being cut, turning some of
that gas to plasma. This is sufficiently hot to melt the metal being cut and moves sufficiently
fast to blow molten metal away from the cut..
HOW IT
WORKS?
The HF Contact type uses a high-frequency,
high-voltage spark to ionise the air through the torch head and initiate an arc. This requires the
torch to be in contact with the job material when starting, not sp good if you have to penetrate
through things like rust or painted surfaces.
The Pilot Arc type uses a two cycle approach
to producing plasma, avoiding the need for initial contact. First, a high-voltage, low current
circuit is used to initialize a very small high-intensity spark within the torch body, thereby
generating a small pocket of gas. This is referred to as the pilot arc. The pilot arc has a
return electrical path built into the torch head. The pilot arc will maintain itself until it is
brought into proximity of the workpiece where it ignites the main cutting arc. These arcs are
extremely hot and are in the range of 15,000 degrees Celsius.
Plasma is an effective means of cutting thin
and thick materials alike. Hand-held torches can usually cut up to 2 in (48 mm) thick steel plate,
and stronger computer-controlled torches can pierce and cut steel up to 12 inches (300 mm) thick.
Formerly, these cutters could only work on conductive materials; however, new technologies allow
the plasma ignition arc to be enclosed within the nozzle, thus allowing the cutter to be used for
non-conductive workpieces such as glass and plastics. Since plasma cutters produce a very hot and
very localized "cone" to cut with, they are extremely useful for cutting sheet metal in curved or
angled shapes.
Inverter cutters rectify the mains supply to
DC, which is fed into a high-frequency transistor inverter between 10kHz to about 200kHz. Higher
switching frequencies give greater efficiencies in the transformer, allowing its size and weight to
be reduced. Today's power modules are called IGBT's (Inter Gate Bipolar Transistors) and are
generally found in better quality machines. IGBT based machines operate more efficiently and
reliably.
The best way to
decide which model is going to be right for you is to consider the thickness of metal you intend
to cut. We are always honest in what we claim our machines will cut. We quote the clean cut
depth as a benchmark for cutting thickness. This will mean that the maximum, or severance cut,
will be 20 -25% higher then the clean cut measurement. Severance cuts on most machine will
normally require some finishing on the cut edge due to the cutter operating at the upper most
limit of it's operational envelope.
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