November '22

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G R A P H I C S - P R O. C O M N O V E M B E R 2 0 2 2 • G R A P H I C S P R O 8 9 laser energy, so you have to slow the machine down, unless you have a 120 watt and then you can run full speed," Dean says. "For lasers that are 50-watt or 60-watt, you have to slow the laser down so that you get enough depth into the wood." But if a laser engraver goes too slowly over wood, it can leave a charred mark, notes Voigt. It also depends on the type of wood being cut or engraved. Some woods are more porous than oth- ers and will leave grains behind when engraving. Hardwoods are always a good choice. Engraving plastics is different. "Vaporizing the cap sheet on engraver's plastic can be done at high speed. ose are the two primary variables that control the laser: speed and power," Dean states. For glass, the laser should be on medium speed and high power, but you might want to adjust the artwork to 70% or 80% fill instead of being 100% because when the laser hits the glass, it chips the engraving surface. If you reduce the fill, you aren't applying as much heat to the glass overall, and it doesn't chip as much. If you want to use a CO 2 laser on metal, you must first apply a metal-marking spray onto it. When the laser hits the coated sur- face, it creates a thermochemical reaction that bonds the spray to the metal, producing a permanent black mark, says Dean. Other metals, like anodized aluminum, produce a nice white contrast when engraving without applying a metal-marking spray first, Dean adds. Powder-coated metals can also be lasered. e laser vaporizes the paint and exposes the shiny subsurface beneath it. Most colored stainless steel mugs are powder coated. Leather is a great product for both cutting and engraving. Shops can laser engrave a logo onto leather for keychains or luggage tags and then cut them out. Set your laser to high speed/low power, and it will produce a nice, charred mark on the leather, which creates a high contrast. Stone is yet another popular substrate for engraving. Granite and marble are used for headstones and monuments. Typically, the names of the deceased will be sandcarved onto the stone, and then a photo or saying will be laser engraved onto it. It is much easier to engrave a picture or design with a laser than to develop a stencil for sandcarving, argues Smallwood. A 50- to 100-watt laser can engrave on granite and marble. Another big industry for engraving is bricks. Hospitals, schools, and even sports complexes sell engraved bricks to help raise funds for projects. In the past, those items were only sandcarved then painted. With a laser engraver, the intense heat turns the engraved area black, so the engraved area doesn't need to be painted or touched up down the road. "Bricks are a huge moneymaker in the business," notes Smallwood. On the bigger side of things, Kern's lasers are used for many industrial purposes, like large point-of-purchase displays, shower and bathroom doors, lighting, and aerospace. Much of it is laser engraving UPC bar codes or parts numbers on ID tags, tools, and control panels. It's clear each substrate has its own set of guidelines. "It is impor- tant to use the appropriate laser parameters for each material to achieve the best result," adds Stevens. "For example, engraving paper usually requires less power than engraving wood or engrav- er's plastic, and when engraving acrylic, you typically achieve the most uniform results when using lower power. It's also impor- tant to note that going too slow could result in a fire depending on the material, which is why using the appropriate settings is so important." GP Paula Aven Gladych is a writer based in Denver, Colorado, who has been covering the graphics industry since 2014. She can be reached at Relief carving can make for some very high-end looking awards. (Image courtesy Trotec Laser) It is important to learn how a laser reacts to a variety of materials. For example, wood requires different settings than marble. (Image courtesy Trotec Laser)

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