The plasma cutter is the big brother to the oxyacetylene cutting torch. Utilizing a high speed high temperature jet of plasma, the tool can cut through almost anything with startling speed.
Plasma cutters developed out of the arc welders employed during WWII to help speed production. Arc welding uses an electric current to melt the material being joined while blowing inert gas onto the weld to protect the material from impurities and oxidation. It was discovered that by constricting the flow of this protective gas and increasing the energy the temperature would increase. Under the right circumstances the inert gas becomes a plasma which moves with very high speed.
Modern plasma cutters consist of an electrode that is inside a nozzle that the inert gas flows through. The large potential difference between the electrode and the piece to be cut results in the gas becoming ionized. The current then passes through the ionized gas heating it to 25,000 degrees Fahrenheit. The nozzle is specially designed to direct the flow of plasma into a jet that can move as fast as 9,000 mph. To ensure that the plasma jet is not disrupted and to protect the piece being cut there is usually an additional flow of inert gas around the cutting gas.
Depending on the type of plasma cutter used the material may need to be metallic and attached to a grounding wire to establish the circuit that generates the plasma. However some models do not need this, creating the ignition arc inside the nozzle allowing them to be used on all types of materials.
Industrial plasma cutters can cut through upwards of 12 inches of steel and can be mounted on cnc machines and cost thousands of dollars. Hand held torches can cut about 2 inches of steel, and some models can weigh only a few pounds and cost only a few hundred dollars.