Plasma cutting technology has been in existence for decades1

A plasma cutter is actually a relatively simple device. The cutting head consists of a central hollow tube that has a small opening on the end. An inert gas is pumped through this tube so that it increases in pressure when it exits at the end. An electrode in the center of the tube affects the inert gas so that it becomes negatively charged. When the metal end of the nozzle comes into contact with the metal surface that is going to be cut then a circuit is completed. This generates a spark that ignites the gas and forms a stream of plasma. Plasma is charged so it is actually conductive and will keep the circuit completed as long as the stream is in contact with the metal. A CNC plasma cutter generates the initial spark inside of the nozzle so that an uncontrolled spark does not damage the material being cut.

With both a handheld and CNC plasma cutter the hot plasma arc is controlled by a second gas. This gas is pumped through airways that are located along the outer edge of the cutting nozzle. This is known as the shielding gas. The shielding gas uses air pressure to create an invisible barrier around the plasma arc. The speed and direction of the shielding gas can be used to control the dimensions of the plasma arc so that cuts of any size can be made. The shielding gas also helps with a CNC cutter by forcibly ejecting molten metal that would otherwise cool and created jagged edges along curves and other complex cuts.

The circuit that is created when performing a plasma cut means that the material that is being worked on must be grounded during the process. The type of inert gas that is used to create the plasma arc as well as the speed of the gas and the size of the nozzle can all be varied to compensate for different types of metal. Improper settings can cause the cutter to melt away large portions of a soft metal or can make the cutter ineffective on thick pieces of durable alloys.