| Plasma (arc) cutting was developed in the 1950s for cutting of metals that could not be flame cut, such as stainless steels, aluminium and copper.
Technological developments since then include mild and low-alloy steel-cutting devices and also high-precision plasma-cutting units.
Basically, the Plasma gas is ionized in the nozzle and focused by a special nozzle design. This hot Plasma stream alone can be used to cut materials such as plastics (non-transferred arc). In metal cutting, an electrical arc is also ignited between the electrode and the workpiece to increase the energy transfer. A very narrow nozzle orifice focuses the arc and the Plasma stream.
Additional lacing of the discharge path can be achieved by a secondary (shroud) gas. The nature of gas determines the lacing ability. For environmental reasons, plasma cutting is often done underwater in a basin.
Plasma gases include argon, hydrogen, nitrogen and mixtures thereof, as well as air and oxygen.
High-precision plasma-cutting units work by highly effective focusing the plasma stream, by rotating it for example. And gases are the key to success, forming the plasma, lacing the plasma, reacting with the material and removing melt and slag. |
