Plasma Cutting

Thu, 10 Jul 2008

Plasma is the most common state of matter in this universe. Plasma is an ionized gas where sufficient energy is provided to free electrons from atoms or molecules, to allow both ions and electrons to co-exist. Plasma is the fourth state of matter. A spark in a gas creates plasma. A plasma cutter cuts steel and other electrically conductive metals. These cutters work by using a high voltage electrical arc and a compressed gas or normal air.

Plasma cutters work by sending an electric arc through a gas compressed in a constricted opening. The gas can be nitrogen, argon, oxygen, etc. The electrical arc generated by an internal electrode ionizes gas as it passes through the opening, creating a concentrated arc of plasma at the cutter’s tip. Excited in this way, the gas is raised to its plasma state.

As metal is being cut it becomes part of the plasma generating circuit, the electrical conductivity of plasma causes the arc to transfer energy and heat the work.

In today’s plasma cutting devices, a pilot arc between the electrode and nozzle (opening) is used to ionize the gas, and initially generates plasma prior to the full arc transfer. Light portable plasma cutters often use 110 volts with an output 12 – 35 amp. Large cutters use 220 volts with an output of 50 – 80 amps, or more. These machines often feature on-board air compressors to simplify their use.

Plasma cutting does not require highly flammable gases. Plasma cutting is more efficient than laser cutting. It can cut thicker sheets than laser, as reflectivity encountered in aluminum and other alloys, reduces laser efficiency.