Plasma Cutting

Plasma cutting is a process that is used to cut steel and other metals of different thicknesses using a plasma torch. An inert gas is blown at high speed out of a nozzle, at the same time an electrical current is formed through that gas from the nozzle to the surface that is being cut, turning some of that gas into plasma. This plasma is sufficiently hot enough to melt the metal and moves fast enough to blow the molten metal away from the cut. One process, the HF Contact type uses a high frequency high voltage spark to ionise the air through the torch head and produce an arc. This method requires the torch to be in contact with the workpiece on starting and so this is not a suitable method for CNC machinery. The Pilot Arc type uses a two cycle approach for producing plasma, this avoids the initial contact. It first sends a small high intensity spark within the torch body which generates a small pocket of plasma gas. This is known as the pilot arc. This pilot arc has a return electrical path built into the torch head. This arc will maintain itself until the nozzle is brought into the proximity of the work piece where it ignites the main pressure cutting arc. These arcs are extremely hot and can range from 25,000 centigrade to 45,000 centigrade. Plasma cutting is an effective way of cutting thick and thin metal, the hand held torches can cope with 48mm thickness and the large CNC machines can cut up to 150mm thick.