How does a plasma cutter cut metal?
Q: How does a plasma cutter cut metal?
A: One common description of plasma is to describe it as the fourth state of matter (aside from solid, liquid and gas). The difference between these states relates to their energy levels. When we add energy in the form of heat to ice, the ice melts and forms water. When we add more energy, the water vaporizes into hydrogen and oxygen (steam). By adding more energy to steam, these gases become ionized, causing the gas to become electrically conductive. This electrically conductive, ionized gas is called plasma.
The process of plasma cutting electrically conductive metals uses this electrically conductive gas to transfer energy from an electrical power source through a plasma cutting torch to the material being cut. The basic plasma arc-cutting system consists of a power supply, an arc starting circuit and a torch. These components provide the electrical energy, ionization space capability and process control necessary to produce high-quality cuts on different materials. The power supply is a constant current DC power source. The open circuit voltage is typically in the range of 240 to 400 VDC. The output current (amperage) of the power supply determines the speed and cut thickness capability of the system. The power supply provides the energy to maintain the plasma arc after ionization. The arc starting circuit produces an AC voltage of 5,000 to 10,000 volts at approximately 2 megahertz. This voltage is used to create a high-intensity arc inside the torch to ionize the gas, thereby producing the plasma. The Torch serves as the holder for the nozzle and electrode, and provides cooling (air) to these parts. The nozzle and electrode constrict and maintain the plasma jet, which reaches temperatures up to 40,000° F, quickly piercing through the metal work piece and blowing away the molten material. (Source: Forney Industries)