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Laser metal engraving involves a process where a small amount of surface material is vaporized or burned off of the metal surface by a laser beam to form a logo, model code, or other design for the metal part. Several different types of laser beams are used to do this, including carbon dioxide (CO2) lasers, ytterbium (Yb) fiber lasers, and yttrium aluminum garnet (YAG) lasers. The shorter the light wavelength of the laser beam, the finer the markings it can make.
CO2 lasers usually have a fairly large wavelength of laser light, which is 10 times greater than that of a YAG laser at 10,064 nanometers. This makes them suitable for general laser metal engraving in a variety of materials aside from metals, including marble, wood, and plastic. YAG and Yb lasers have wavelengths of 1,064 to 1,080 nanometers in size and are used for finer metalworking, but won't engrave into other materials due to their limited power.
Both YAG and Yb lasers for engraving metal will cut to very minimal depths, but their superior detailed work makes them suitable for custom engraving uses. Laser metal engraving with the Yb fiber laser will produce markings to a depth of 0.001 inches (0.0254 millimeters). YAG lasers are slightly more powerful, and can cut to a depth of 0.003 inches (0.0762 millimeters). Of the two, the Yb fiber laser costs less and is a more compact engraving machine. The YAG laser metal engraving system is faster, however, and offers slightly more versatility, as the depth of the cutting can be varied more by altering the speed and number of passes of the YAG laser beam over the surface.
Types of laser engraving machines also vary by how automated they are and how the surface to be engraved is mounted. The most advanced machines are those that are the fastest, with computer-controlled, preloaded programs for the laser. Resolutions of anywhere from 50 dots per inch (DPI) to 1,200 DPI are possible for the engraving. By contrast, a typical printer for a home computer can offer a contrast ratio of 600 by 600 DPI.
A CO2 laser metal engraving machine is often the most versatile, and can work with metals such as aluminum, steel, and chrome. Softer metals such as brass, copper, and tin can also be engraved. In the arena of industrial engraving, the CO2 laser is used almost exclusively over other types. This is because it can engrave into a wide variety of metals and other materials such as rubber and acrylic, whereas a YAG laser is limited to fine printing in metal, such as for the markings on ballpoint pen clips.