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The following information is presented here courtesy of The Engravers Journal. More information may be available by visiting the EJ web site (www.engraversjournal.com) and checking out EJ’s archive of articles (1975-present). Key word searches may be performed using the EJ Index of Articles, and most back issues (1975-present) are available.

LASER MARKING—OVERVIEW

Laser marking involves using an industrial laser which produces a highly intense beam of concentrated laser energy focused to a pinpoint-sized spot where the beam contacts the material substrate being marked. The technique encompasses a whole host of related but often distinct methods which vary depending upon the type of laser, material or substrate used, lasering method and the desired end result.




One method, ablation, (commonly known as laser engraving or laser cutting) involves using a type of laser and appropriate power level which produces a beam which is readily absorbed by the material substrate and which vaporizes the material, creating a mark with an incised groove which varies in contrast and sometimes in texture from the substrate surface color. It can be used for either direct part marking or for tag and nameplate production.

Another technique, laser annealing, involves using a type of laser and appropriate power level to produce a beam which provides a localized heating of the material substrate (often metals), causing a permanent color change which contrasts in color from the substrate’s surface color. The color of the mark is determined by the maximum surface temperature attained during lasering. This process is most often used for direct marking of bare metal parts.

A third approach to laser marking, laserable colorable substrates, involves the use of either a specially coated or specially treated substrate which, when lasered, changes color creating a mark that contrasts with the surface. Since this technique requires specially coated materials, it is most often used for tag and nameplate production.

Yet another laser marking option, laserable surface coated substrates, involves laser cutting or engraving a substrate which contains a laminated or coated surface layer, such that where the laser beams cuts away the surface layer it exposes a contrasting core color in the finished mark. Some common industrial materials, e.g. anodized aluminum can be marked in this fashion, while a large number of metal and plastic "engraving stocks" have been expressly designed for this purpose. Accordingly this process is most often used for tag and nameplate production.

A final variation of laser marking involves the application of a laser-fusable coating to the substrate which, once lasered, adheres solidly to the substrate with a highly durable mark in a contrasting color. Typically this involves coating a bare substrate, e.g. metal or glass, with a liquid coating, lasering, and then removal of the unlasered coating. This process is used primarily for direct marking of metal parts, although it's also suitable for metal nameplates.

Lasers used for marking/cutting/engraving are generally characterized by the material used to create the laser energy beam. Each laser medium produces a different wavelength of laser light which affects its suitability and/or efficiency for cutting or marking various substrates.

A CO2 laser gets its energy by applying an electrical current to the laser to be, which is filled with carbon dioxide gas. Laser engraving systems are popular for their relatively low price will generally do a good job of cutting/engraving/marking (by ablation) most materials which are poor conductors of heat and electricity. Therefore they are well suited for marking a wide rage of materials such as plastic, wood, glass, paper, leather, stone, etc. However CO2 lasers generally can do little marking on highly conductive materials, in particular bare metals. Higher wattage lasers can cut metals and low wattage lasers can mark specially coated metals using laser-fusable coatings.

Another common laser type for industrial marking is an Nd:YAG laser, which derives its laser energy by "pumping" a rod of "Neodium-Yttrium-Aluminum-Garnet material with energy. These so-called "YAG" lasers produce a wavelength of light which is more readily absorbed by conductive materials such metals and therefore are known for their ability to mark metal, either by ablation or by creating a color change through annealing.

Another popular laser is known as a Nd:YVO4 ("Vanadate") laser, which utilizes a Neodymium Doped Yttrium Orthranadate crystal rod to generate its laser energy. Vanadate lasers are closer in capability to YAG lasers in their overall performance and their ability to cut or mark various materials.