How Does a Laser Cut Through Metal?

Laser light is energy produced at a precise wavelength. It can be focused and aimed to an exact location on metal to be cut. The equipment may use mirrors or fiber optics to direct light to the metal. A lens focuses the light to a pinpoint. Lasers used for cutting have very high power, on the order of one to four kilowatts, thousands of times greater than those used for other purposes.

Materials reflect, transmit, and absorb light to varying degrees. To cut metal, it must absorb enough light to heat and melt it. If the metal's absorbance is relatively low, the laser's power must be greater to compensate.

A high-pressure gas jet moves alongside the laser beam, blowing the melted material out of the way. This speeds up the process and helps make clean edges. Laser-cutting equipment typically uses oxygen or nitrogen gas.

The maximum metal thickness the laser can cut is determined by the metal and the laser's power. Thicker metal takes more time to cut. If the material is thin, several sheets can be stacked and cut at the same time. Lasers can be used to cut up to .5 inch thick steel.

Sheet-metal cutting equipment is usually packaged as a flat-bed system. It may move the metal, keeping the laser stationary, it may move the laser, or both. A computerized drive system guides the cutting head to make the desired shapes. The drive system moves in two dimensions, along an x and y axis. Since the beam can be stopped and started at any time, the laser can cut any two-dimensional shape. Depending on the material and thickness, typical cutting speeds run between 30 and 500 inches per minute.

Laser systems can make cuts from .006 to .016 inches wide. It removes very little material, produces little waste, and allows precise cuts. The whole drive system must operate to tolerances of around .005 inches.

Lasers can also be used to cut thin-walled metal tubes. The tube turns in a fixture while the laser moves along the tube and cuts it. Round, oval, and square cross-section tubes may be cut this way.

Three-dimensional laser machining can be performed by other equipment. In this case, the laser beam and gas jet are packaged as an independent cutting tool manipulated by a robotic arm. The laser light is carried in a flexible fiber optic cable connected to the cutting tool.