Plasma Cutting
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, an inert gas (in some units, 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. The plasma is sufficiently hot to melt the metal being cut and moves sufficiently fast to blow molten metal away from the cut.
Processes
The HF Contact type uses a high-frequency, high-voltage spark to ionise the air through the torch head and initiate an arc. These require the torch to be in contact with the job material when starting, and so are not suitable for applications involving CNC cutting.
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 plasma 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 plasma cutting arc. Plasma arcs are extremely hot and are in the range of 25,000 °C (45,000 °F).
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 cut steel up to
6 inches (150 mm) thick. 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.