Plasma is a state of matter and is similar to a gas because it has no specific shape or volume. It can be created when an electrical current is sent through an inert gas and compressed through a narrow plasma torch nozzle that creates and conducts a highly charged electrical arc. This charged compression results in very high temperatures, giving plasma the ability to cut through a range of metal material thicknesses and types, as long as that material can conduct electricity. There are three main types of plasma cutting systems: the pilot arc process, the high frequency (HF) contact process and the computerized numerical control (CNC) process.
The systems that use the pilot arc process utilize a highly efficient electrical circuit that creates a very small, high-intensity spark inside the body of the plasma torch, resulting in the generation of a small amount of plasma gas before the nozzle even touches metal. When the arc does come into contact with the cutting surface, this electrical conductivity is then transferred to the metal being cut, creating an electrical circuit that ignites at temperatures as high as 45,000 degrees Fahrenheit (almost 25,000 degrees Celsius). This method is used with CNC machining to reduce the problems that can be caused by high-frequency electricity reacting with computerized machinery and generally produces a much cleaner metal cut and blows away any debris.
Plasma cutting systems using the HF contact process utilize a high-frequency circuit generated by an internal, negatively charged electrode that ionizes the gas, creating a spark and ignition, similar to a spark plug, instead of using a lower-voltage pilot arc to initiate the plasma generation. There is more debris and clean up with this method, but the nozzle creates a very concentrated, stable arc of plasma at the tip of the plasma cutter. Cutting begins when that plasma arc connects with the metal, not before it connects.
Systems that use a CNC plasma cutting process utilize a computer-generated design to determine the welding cuts to be made. These CNC units are larger, fixed machines that should use pilot arcs to alleviate reactions caused by high-frequency electrical interference. CNC plasma cutting systems are able to create clean, sharp, quick and complicated automated cuts through the use of computer programming.
Plasma cutting systems have become advanced, flexible and more affordable, and they can be used in a variety of applications. The choice of plasma cutting systems will vary depending on factors such as purpose, volume, speed, accuracy and material type and thickness. Other factors that might affect the choice include cutting precision required, portability, voltage availability, user experience level, safety requirements and costs.
