The first production laser cutter drilled holes in diamond
Laser cutting started with about the hardest job imaginable. In 1965 a machine from the Western Electric Engineering Research Center went into production boring holes through diamond dies. Six decades later the same basic trick, focusing light onto a speck smaller than a hair, is used in school workshops, architects' studios and hobbyists' garages.
The beam leaving a laser is only a millimetre or two wide. A lens or mirror squeezes it onto a spot around 0.025 millimetres across, concentrating enough energy to melt, burn or vaporise whatever sits there, while a computer steers the cutting head along a pattern translated from a design file. Cuts can be as narrow as a tenth of a millimetre, and machines position themselves to within 10 micrometres.
How the material leaves the cut depends on what it is. Wood, carbon and thermoset plastics, which do not melt, are simply boiled away: the beam digs a keyhole that suddenly absorbs more light and deepens fast. Metals are usually melted and then blasted out by a high-pressure gas jet, which saves power because the metal never has to be heated further. Glass is handled more cleverly still. A beam warms a line on the surface, the local expansion starts a crack, and moving the beam steers that crack at metres per second.
The technology grew in steps. British engineers pioneered laser-assisted oxygen cutting of metal in 1967, and by the early 1970s it was slicing titanium for aircraft. Carbon dioxide lasers of that era lacked the power to beat the heat-spreading of metals, so they cut textiles instead. Newer fibre lasers amplify light inside glass fibre at a wavelength of 1064 nanometres, producing spots up to 100 times smaller than carbon dioxide lasers and cutting shiny copper and brass that would bounce other beams away.
Compared with blades, a beam never dulls, touches nothing that could contaminate the part and leaves only a small heat-affected zone, so warping is rare. It also cuts hard materials like tungsten and titanium. Plasma torches still win on steel thicker than about 10 millimetres, and high-power lasers that approach them cost far more. One variant guides pulses through a thin water jet, which acts like an optical fibre while cooling the cut and washing debris away.
Source: Laser cutting
