Two methods are currently used to cut sheet metal: plasma cutting and laser cutting. Plasma cuttingdates back to the 1950s when it was developed as an alternative to flame cutting. It works by firing a superheated, electrically ionized gas (i.e., plasma) out of a nozzle at high speed toward the workpiece. An electrical arc is then formed within the gas. This electrical arc ionizes some of the gas, creating an electrically conductive channel of plasma in the process. As electricity from the cutter torch travels down this plasma, sufficient heat is generated to melt through the workpiece. The plasma and compressed gas blow the hot molten metal away, resulting in separation of the workpiece.
Laser cutting was first developed in the 1960s as a way to cut holes in diamond dies. This thermal cutting process uses a computer-directed, high-power laser along with oxygen, nitrogen, and compressed air to burn, melt, vaporize, or blow away the material being cut. The laser beam is emitted from the laser source and then transported through a suitable beamline (made by several mirrors or an optical fiber cable) into the laser head containing the lenses that focus the beam onto the surface of the material for cutting and piercing.
There are two types of lasers used in these applications: CO2, which works at a wavelength of 10.6 μm, and solid-state lasers, which operate at around 1 μm (thin-disk and fiber lasers). CO2 lasers are cheaper, but they cannot cut through copper, brass, and aluminum because they do not work on reflective surfaces. In contrast, solid-state lasers (besides a higher energy/wall-plug efficiency and wider variety of materials) have the major benefit of a much higher processing speed/feed rates, due to the higher absorption rate of ~1 µm vs. ~10 µm wavelength in ferrous materials.