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Signs are made to make a point. In a world crowded with advertising messages, laser engraving provides some unique means to make a point and make that point stand out.
By far the most common material used in laser engraving is acrylic, and for good reason. As David Stevens, senior technology specialist for Universal Laser Systems puts it: “Acrylic is a common material, but no other material reacts better with the laser when it comes to no pre- or post-processing.”
“Acrylic is a natural partner for laser equipment as it is cut with a fire polished edge and etches a frosty white color that illuminates when LED lights are snapped in the side of the panel,” says Derek Kern, president of sales for Kern Laser Systems. “Acrylic is also available in a large variety of colors, thicknesses and textures.”
Making Acrylic Shine
Among the various combinations of engraving and cutting you can do with a laser engraver and acrylic, one of the most potent is edge lighting. With recent advances in LED lighting, the light-transmission qualities of acrylic and the effects laser engraving can create, the options and potential of laser-engraved acrylic has greatly increased.
“Edge-lit acrylics are phenomenal for signs. They’re designed to transmit light, but they need that clear polished edge, which the laser does exceptionally well,” says Stevens.
Stevens adds that Lucite makes acrylic products that transmit light better than standard acrylic, which already does a fine job of light transmission.
“When you engrave the surface of it the imagery really pops out. You can also paint the backside and engrave through the paint with one pass on the laser. Then, as a second pass, take the laser lens out of focus and engrave it again to create a glazing effect, turning the white, frosted acrylic clear. When you then paint over that area that you just engraved, glaze with a translucent ink or paint and hit the acrylic with an edge light. The light captures the lettering, allowing those areas to glow in colors when looking at it from the front clear side,” says Stevens. “The other thing I like to do with acrylics that you can’t do with a lot of other materials are 3-D textured effects, like a gun grip or patterned texture. When you light it from the back and side it produces a brilliant look, but they look great un-lit as well.”
Stevens adds that three-dimensional textured effects are best when used with thicker acrylics that can handle the tension release of removing a certain amount of material on one side. However, a thinner material can be placed in an oven and heated to a certain temperature so that it can “relax” and flatten again.
Kern says dot patterns and etched lines are two of the most popular effects that are used in a variety of acrylic backlighting applications. Both are relatively easy to create with software such as CorelDRAW or Illustrator.
Cast Vs. Extruded
Another thing to keep in mind when working with acrylic and lasers is whether the material is cast or extruded. Cast acrylic has a higher melting point and produces a white, frosted look when laser engraved while extruded acrylic has a lower melting point, producing a clear engraving. What that means practically and generally is that cast acrylic is best for engraving while extruded acrylic is better for cutting out letters and forms.
“Cast acrylic will produce a frosted look when you engrave it. With extruded acrylic, on the other hand, you don’t necessarily get a frosted look, but due to the lower melting point you can cut it much quicker,” says Josh Stephens of Trotec Laser. “The big advantage with laser-cutting acrylic is that you can get a glass-like edge straight out of the laser machine without flame polishing. The end product quality increases dramatically if you use the proper setup and settings for achieving a glass-like edge for point of sale displays and signs that require more visual pop.”
For Bill Baker, owner of Park Place Sign Systems, a wholesale sign manufacturer based in Hannibal, Missouri, the polished edges that laser engraving can produce on acrylic makes sign production easier and faster.
“We primarily use our laser engravers for cutting sign shapes out of acrylic because the laser gives us consistency and accuracy when we’re joining signs together that have high tolerances so the edges line up perfectly,” says Baker. “We also do a lot of subsurface graphics when we’re doing ADA signs or directories that require subsurface graphics. We’ll paint the backside of the non-glare acrylic then burn through the paint with the laser and color-fill into the area where the paint has burned off. If we paint green on the back side then burn the paint off and fill it with white. When you look at it from the front side it will give you a green background with white text.”
Baker adds that he found a time-saving technique for the production of acrylic letters that require stud mounting: “We reverse-cut the letters and engrave the stud locations on the back of the sign so that all we have to do is drill and tap. We can use the same file we used to laser-cut the letters to generate a paper pattern, which takes out the step of drilling, tapping and putting them onto the paper pattern with the studs in them and then punching the pattern.”
Baker says the choice between using a laser engraver-Park Place Sign Systems runs three laser engravers from Universal Laser Systems-and a CNC router is based on the type of material and the size of the project.
“The laser engravers we have accommodate a sheet size of 18″ x 24″; anything larger we run on our CNC routers. The advantage of the laser is that you can get extremely sharp corners. A router bit will give you a little bit of a rounded corner,” says Baker. “If you have a sign with a name insert-a sandwich-type sign where you take two pieces of acrylic that you bond together with a piece of tape and slide a thin insert between the sandwich layers of acrylic-and want sharp corners, you have to cut it on the laser. We do a lot of our jobs that require name inserts and that’s one of the areas we found where the laser gives us the ability to build up multiple layers with crisp edges on the outside of the sign.”
Baker adds that Park Place Sign Systems also cuts a lot of laminate, such as those manufactured by Wilsonart and Pionite. “Architects and designers like to incorporate the look of the different laminates into their signage. To make those pieces fit accurately onto and into the other pieces of a sign we’ll cut the laminate with a laser. It takes some experimenting with the wattage amount and the speed you run the laser, which is measured in pulses per minute. With different laminates you can get better results by varying the amount of power and speed you cut with,” he says.
As Baker notes, acrylic is the workhorse, but other materials can provide equally good results and produce unique things. David Stevens points to a Mother of Pearl laminate produced by Aqua Blue Maui, Kula, Hawaii (www.aquabluemaui.com), that works well for laser cutting and inlays.
“It’s a thin laminate material adhered in sheets so that it’s easy to cut and can be applied to any material,” explains Stevens. “It’s also much lower in cost than typical shell material because it’s so thin.”
For metals, Stevens says a typical CO2 laser system doesn’t work well unless you prime the metal with a metal marking compound like TherMark. However, laser engraver manufacturers are also producing multi-wavelength lasers (aka fiber lasers) that can mark onto and cut various metals without the use of a marking compound.
“In addition to the ability to engrave a high-contrast, UV-stable mark onto the surface of brass, copper, aluminum, stainless steel and other metals, fiber lasers allow you to control color on certain metals,” explains Stevens. “I can laser-mark a piece of stainless steel with our fiber laser and produce red, green or blue by controlling frequency, wavelength, focus and wave form all at once to produce different effects. It’s like when you put flame on a metal you see a rainbow effect from heat distortion; we can control that in a localized state and control what color is in what location without any inks. It can only be done with a fiber laser because it has so much control and it only works with metals with high carbon content, versus aluminum, brass, copper and precious metals. You can mark on those, but you can’t produce the color effect.”
When working with metals that have a high carbon content-like stainless steel and titanium-fiber lasers allow for an annealing process where the laser migrates the carbon to the surface and produces a rich, dark mark without removing surface layers.
“Annealing is a great application if the sign will be exposed to harsh elements, or if the job is for the medical industry. Annealing creates a mark that doesn’t leave areas for bacteria to hide in,” says Trotec’s Josh Stephens. “With annealing you de-focus the laser. That way it’s not necessarily removing the surface and is simply applying raw heat to the metal. You operate it much slower so you have time to cook the metal.”
Similarly, says Stephens, you can drop the focus on the laser with wood to get more of a “charred” look. And, for making cleanup a cinch, Stephens says: “We use transfer tape and mask the wood beforehand. That way if there are any resins or glue in the wood it will save a lot of cleanup time. Even you have intricate engraving that leaves behind a lot of tiny pieces of tape, you can use a lint roller and pick up those little pieces of tape. You laser right through the transfer tape so it will keep the wood piece nice and clean, and if you wanted to add paint to it, it’s already masked and you can roll or spray it. You can do that with just about any other material as well. Sometimes you’ll have dust left on the material after lasering and I’ve found the easiest way to remove that is to use a Mr. Clean Magic Eraser. It’s something you can pick up at any store and it cleans the product really well. It’s pretty easy, because you just take one of those and wipe it down real quick so there’s not a lot of labor involved in cleanup.”