Cutting is a manufacturing process used to separate materials. Laser cutting is often used in industrial manufacturing areas for cutting sheet metal and piping. It uses a computer controlled high output laser to do the cutting. Plasma cutting uses a torch which blows an inert gas at high speed through a nozzle which when held close enough to the parts creates an arc and melts the material. Water jet cutting uses extremely high pressure and velocity water to cut into metals. A torch is used in oxyfuel cutting to heat the metal; oxygen is then blown into the part causing the metal that it combines itself with to leave the cut as slag. Electric discharge (EDM) is also known as spark machining or spark eroding. EDM removes material by rapid arc discharges between the electrode of the cutter and the work-piece which has to be a conductor.