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Tips & Techniques for Personalizing Acrylic

Copyright © 2011 by Davis Multimedia, Int'l. All Rights Reserved.
As Printed in April 2011, Volume 36, No. 10 of The Engravers Journal
     
Figure 1: Suggested laser power and speed settings for engraving acrylic using a CO2 laser engraving machine.

 

  Figure 2: Adjusting the pulse rate on your laser will affect the smoothness of the cut.

     Acrylic is highly regarded as one of the most popular materials in the industry. It’s a beautiful material with high-end appeal, yet it is still an affordable option for many customers. The applications for this material are seemingly limitless and include product categories such as awards, gifts, signage and more. Take a look at catalogs from acrylic product suppliers and you will find pages and pages of unique designs that will appeal to high-end markets, such as corporate awards, as well as to more budget-conscious clients like school sports leagues. On top of that, acrylic engraves beautifully. Using a laser or a rotary engraving machine, you can achieve truly outstanding engraved images from intricate logos to the super fine details of a photograph.
     In many cases, all you need to do is show a customer a beautiful acrylic product and the sale is in the bag. What’s even better is that acrylic is an extremely versatile material that is easy to work with. Your design options today are many times greater than just a few years ago with more choices in colors and shapes and with the advent of full-color enhancements such as the AcryliPrint process. Here are some tips and techniques for personalizing acrylic to keep both your in-house production and your sales running at full speed.
Types of Acrylic
     Acrylic is a generic name for a heat-sensitive plastic material that is made by many manufacturers, including Rohm & Haas, Dupont, Eastman, Cyro and Mitsubishi. Familiar brand names include Plexiglas and Lucite. Different types of acrylic are used for different applications, but the two types of acrylic used for most engraving applications are cast acrylic and extruded acrylic. While both are used, note that there are fundamental differences between the two.
     In our industry, the standard for award production is cast acrylic. Cast acrylic is produced by pouring an acrylic “syrup” between two sheets of tempered glass. A rubber gasket is placed between the sheets of glass and the thickness of the gasket creates the thickness of the poured sheet as the “monomer” hardens into a solid sheet of acrylic polymer. Today, acrylic awards are made out of cast material because of its premium optical clarity and because the material turns frosty white when laser engraved.
     Extruded acrylic is another common type of acrylic. Manufacturing extruded acrylic involves feeding pellets of resins into an extruder that heats them to a molten mass. This molten plastic is forced through a die to create a molten sheet and then the sheet is fed through rollers to determine the thickness and, in some cases, the surface finish. Extruded acrylic is popularly used for certain applications such as producing display fixtures and, sometimes, for accents on acrylic awards, such as mirroring. Extruded acrylic is rarely used to manufacture acrylic awards because, unlike cell cast acrylic, it engraves “clear.” It’s also a much softer material, which tends to “gum up” during rotary engraving unless an extremely sharp cutter is used. Although not always ideal for engraving, extruded acrylic cuts superbly with a laser. It will cut cleanly and smoothly with a flame-polished glass-like edge quality.
     In general, cast acrylic products work best for engraving gifts and awards. Extruded acrylic works best for profile cutting letters, blanks and special shapes where a smooth, polished edge is desired. In either case, though, keep in mind that different types or brands of acrylic sometimes engrave with different results, so most engravers find a variety they like and stick with it.
     Because acrylic is easy to fabricate, you can choose to work with sheets of acrylic that you can saw, rout and thermobend in your shop. But there’s also a huge selection of stock products in many interesting and intricate shapes and edge finishes. Most suppliers also offer custom fabricating services.



     
Figure 3: Two options for rotary engraving acrylic are the flat look (left) and the raised dimensional look.    

Figure 4: Illustration shows a 60? included angle cutter making a flat groove, and 90? included angle cutter making a dimensional,
or V-shaped, groove.


       You can choose from the always-popular clear acrylic or, for a different look, try something tinted with a color like sapphire (blue), jade (green), red or gold. Opaque colors are also available and include white, black, brown, blue, red, etc. Mirrored accents are also a very popular option. Manufacturers will laminate or glue mirrored material onto the top, bottom or sides of an acrylic product to create interesting, colorful reflections and accents that add a touch of distinction. Screen printing is another method used to add color to acrylic. This technique can be used to create colorful patterns, such as a black and blue marble, on the back of an award. Acrylic also looks stunning when paired with other materials, such as metal or wood bases or accents.
     As mentioned, acrylic products can be personalized with a laser engraving machine or a rotary engraving system. Following is a look at both of these methods and some tips for getting the best results.
Laser Engraving
     Acrylic is unique in that it is highly sensitive to absorbing certain wavelengths of light. One highly absorbed wavelength of light energy is 10.6 microns which, coincidentally, is the exact same output frequency of a CO2 laser. When exposed to a laser beam, acrylic acts like a sponge and essentially soaks up the laser energy. Even low watt lasers—as low as 10 watts—can produce excellent engraved results (albeit slowly) as the laser vaporizes the material.
Fine Tuning the Layout
     Acrylic products can be engraved on the front or the back so the engraving can be viewed through the acrylic. Engraving the back of an acrylic piece is often preferred because it gives the item a dimensional quality that really enhances the look of the material. If you do this, however, remember that the graphics and text should be reverse-reading to make them read correctly from the front. You can use the “mirror” function in CorelDRAW (or your engraving software) to easily accomplish this. The difficult part is remembering to do it; it’s a much more common mistake than you might think. (Note: This is also true for rotary engraving.)
     When setting up a job to be laser engraved, follow the old carpenter’s rule “measure twice, cut once,” especially when engraving expensive acrylic items. One way to check your layout skills is to apply a green-tinted polyester mask to the acrylic piece and use very low power, e.g. 5% power and 100% speed on a 30 watt laser system, to cut only the mask (not the acrylic). Once you are satisfied the image will engrave in the correct location, remove the mask and engrave at the correct power and speed settings for acrylic.

     
Figure 5: 3D engraved logos look beautiful on clear acrylic. Sample from Vision Engraving & Routing Systems, Phoenix, AZ.   Figure 6: Use a lint-free soft cloth to dust or clean acrylic. Paper towels and ammonia-based cleaners can scratch acrylic.

Fine Tuning the Laser Settings
     Laser engraving acrylic is usually problem-free but you might, on occasion, run into some problems. A common complaint from people who laser engrave large fill areas is the appearance of horizontal “raster” lines that make the engraved areas appear coarse. These raster lines create a horizontal, linear pattern where the lasered dots slightly overlap. To reduce the appearance of raster lines, try enlarging the spot size of the focused laser. The focus lens creates a cone-shaped beam that gets larger the more distance there is from the optimum focus point. If you lower the engraving table by .020", the spot size of the laser is increased slightly which, in turn, increases the overlap of each of the raster strokes and creates smoother engraving.
     Generally speaking, acrylic engraves best using high speed and low power. If you are engraving acrylic that is painted or screen printed on one side, use the same speed setting as you would for unpainted acrylic but turn up the power about 10%. That should allow the laser to cut cleanly through the paint.
     On some occasions you may experience problems such as cracking, melting or hazing which usually indicates that there is too much heat present. To remedy this, try decreasing the power and/or increasing the engraving speed. Optimum power and speed settings will depend on the acrylic you are engraving and your laser system. Figure 1 shows some general starting guidelines.
Cutting Acrylic
     A laser can also be used to cut completely through (profile) acrylic using an operation called “vector cutting” because the laser is set to move using an X-Y motion path. Vector cutting provides first-rate quality once you understand a few tricks of the trade. These tricks involve preparing the acrylic sheet, setting it up properly on the engraving table and adjusting some print driver settings.
     All acrylic sheets come with a factory-applied paper mask designed to protect the polished surfaces during handling and fabrication. This brown paper, however, contains paraffin that can cause charring and excessive flame-ups during cutting that could damage the acrylic. To prevent this, always remove the mask and replace it with a medium tack paper mask (available from engraving suppliers). The paper mask protects the acrylic surface, cuts cleanly and can be easily removed after the acrylic is cut. Lightly misting the mask with water will also help draw heat away from the surface of the acrylic.
     Next, it is a good idea to elevate the acrylic sheet above the worktable. The laser energy is not absorbed by the metal table of the laser system but instead, it reflects off of it which can burn the bottom side of the acrylic and cause pitting and distortion. Creating an air space between the acrylic and the table can dissipate this reflected light and thereby improve the cut.
     You can use either shims or a vector cutting table to accomplish this. If you use shims, it’s a good idea to place a metal back-up plate beneath the material. This improves the quality of the cut and saves you from repeatedly cleaning the worktable. Vector cutting tables, available from laser manufacturers, are designed specifically for this purpose and are a good accessory to have if you do a lot of cutting with your laser. A vector cutting table is essentially a metal honeycomb grid that creates air space to dissipate the reflected beam and increase the air flow to reduce flame-ups.
     Most laser machines also have an air assist feature, either as a standard feature or an option. An air assist system directs a constant stream of compressed air across the cutting surface which can reduce flaming, scorching and charring.
     With regard to the machine settings, use a slow speed and a high power setting for vector cutting (profiling) acrylic. This allows the edges to melt and produces a flame-polished effect.
     Keep in mind also that the laser beam does not emit a constant stream of light when it is cutting. In reality, it is being pulsed at a high frequency of up to 2,000 times per second. You can control the frequency that the laser switches on and off by adjusting the “rate” or “PPI” (pulses per inch) setting in your laser’s print driver. Using a high or maximum rate or PPI setting causes the laser to pulse more frequently and will give the effect of a fine-tooth saw blade, resulting in much smoother cuts (Fig. 2).

   
The AcryliPrint process from Acrylic Idea Factory, Norcross, GA, is an excellent way to incorporate photos onto acrylic awards. Color and a unique shape can make an acrylic award very eye-catching (from Acrylic Idea factory).     This freestanding 1" thick acrylic award from Marco Awards Group, South Windsor, CT, features a preprinted golf design.

     Depending on the wattage of your laser and the thickness of the acrylic sheet you are cutting, you might need to make more than one pass in order to achieve a clean edge cut. The higher the wattage on your laser, the deeper and quicker you can cut. For example, a 30 watt laser can cut through 1/4" thick acrylic in one pass, but a 50 watt laser can cut it faster and can also cut thicker pieces in one pass.
     If you do need to make multiple passes, keep in mind the issue of focusing the laser. For example, if the laser is focused on the material surface during the first cutting pass, the beam may be out of focus during the second pass unless you refocus between passes. If the beam is out of focus, you have to burn through more material which takes more time and can cause a poor cut. Most of today’s laser engraving systems offer an auto-focus feature that takes care of this for you. The feature allows you to predefine focus depth changes from within the software in order to automatically cut thick materials in multiple passes with a focusing depth change between passes.
Rotary Engraving
     You can also use a rotary engraving machine to engrave acrylic with beautiful results. Unless you are profiling or making extra-deep cuts, standard tooling and engraving techniques (like what you would use on conventional plastic engraving stock) should work fine. You usually don’t need a coolant, and if you use a sharp carbide cutter, you can front- or reverse-engrave acrylic with stunning visual appeal and exceptional dimensional accuracy.
Cutter Selection & Engraving Depth
     For conventional rotary engraving on acrylic, select a standard 60 degree included angle cutter and engrave at minimal depth. This creates an engraving with a “flat” look that is non-dimensional and appears flush with the material surface (Figs. 3 and 4). Keep in mind, though, that if you plan to color fill the characters, you need to engrave at least .006"-.008" deep (.010"-.012" is optimum).
     If you want to achieve a more dimensional look in the characters and graphics, you will want to create V-grooved letters that have a smaller flat on the bottom and a wide groove at the mouth (Figs. 3 and 4). Front-engraved dimensional letters appear as deep V-grooves; reverse-engraved dimensional letters look as though they are raised when viewed from the front.

   

Acrylic Idea Factory has introduced the AcryliPrint process for creating full-color acrylic awards and gifts.

This cast acrylic pyramid award features a gold bottom that can be engraved with stunning results. Photo courtesy of LaserBits, Phoenix, AZ.   Acrylic can be laser engraved with amazing detail. Photo courtesy of LaserBits.

     To create this look, choose a cutter with a 90 degree included angle and a small tip size. With this larger cutter angle, the deeper you engrave, the wider the mouth of the groove becomes. Even slight increases in depth can produce noticeable differences, so after you select the typestyle, set the depth to achieve the look you want.
     If you have three-dimensional engraving capabilities, you will no doubt want to use them on acrylic. Three-dimensional designs look stunning on acrylic, especially when reverse engraved (Fig. 5).
     For a slightly different effect, you might want to try using a slightly dull cutter to engrave acrylic. This produces bright white lettering and graphics that really stand out, similar to the look created by laser engraving.
Troubleshooting Tips
     Here are a few more tips to keep in mind when rotary engraving acrylic:
• If swirl marks are a problem in the bottoms of engraved grooves, try increasing the spindle speed and/or reducing the feed rate.
Dwell marks (circular dots at the beginning and ending of character strokes) can usually be minimized by shortening the dwell time or, if your system has this feature, by “ramping” the cutter into and out of the material.
If cutter strokes are visible between character strokes, try using a faster speed and/or a slower feed rate.
If the depth nose is creating scratches and shadows around the characters, be sure you’re using light downward pressure and that the depth nose you are using is in good condition. Another option for minimizing shadow images is to use a plastic depth nose instead of a metal one.

 
   
Mirrored accents add color to acrylic blanks. Photo courtesy of Acrylic Idea Factory. Acrylic blanks can be mounted onto different bases to create an interesting look. Photo courtesy of Acrylic Idea Factory.    

Cutting Acrylic
     A major advantage of rotary engraving is that it can also be used to profile acrylic. This technique can be used to create hole cutouts in products such as control panels or to cut out special shapes for custom badges, key tags and other merchandise. For the best results, you will need to modify your standard engraving technique somewhat. Here are a few tips:
• Use fast spindle speeds and slow feed rates.
• Always use a sharp, preferably carbide, cutter. A half-round cutter will work, although a better option might be a quarter-round cutter or a helical end mill, both of which tend to be stronger and produce better cuts.
• Use a tapered cutter for beveled edges and a parallel cutter for straight edges.
• Make sure the work is securely held on the table.
• If excess heat is a problem (if the plastic gums, sticks, stretches, tears, melts, etc.) try using a coolant. A good option for acrylic is dishwashing detergent mixed with water at a ratio of 10% detergent and 90% water.
• If the edge finish isn’t smooth enough, perform a finishing cut at full depth with a high spindle speed, e.g. 20,000 rpm.
AcryliPrint
     One of the most recent innovations in personalizing acrylic products is AcryliPrint, a color imaging process introduced by Acrylic Idea Factory (AIF), Norcross, GA. What’s unique about this process is that it allows you to incorporate bright, vivid full-color photographs and graphics onto clear acrylic blanks to create truly stunning gifts and awards.
     Previously, AcryliPrint products were only available through AIF’s in-house services where you sent them the artwork and they shipped your finished products. AIF still offers services for the trade but the company has since released its FusionProcessor and, more recently, the Junior FusionProcessor that allow you to bring the AcryliPrint process into your shop. The original FusionProcessor is a floor model unit that features a large 18"x24" production table whereas the Junior FusionProcessor is a scaled-down tabletop version with a smaller table (it can handle pieces up to 9"x12") and a smaller price tag.
     In simple terms, the FusionProcessor is a sophisticated heat press. You simply create artwork using an inkjet printer (you can also use other types of printed artwork) and position it on the acrylic blank. AIF sells specially-coated, self-adhesive FusionBlank acrylic blanks and sheet stock designed specifically for this process.
     After trimming the graphic, simply place it in the processor which fuses the artwork to the acrylic in about 11/2 minutes. The results are beautiful and colorful, and the crystal clear acrylic provides a unique dimensional quality. This process is well-suited for a variety of applications including photographs, gifts, awards, sign-
age, name badges, desk plates, promotional products, coasters, puzzles, key tags, point-of-purchase displays, clocks, etc. For more information, be sure to read “A Look at AIF’s AcryliPrint FusionProcessor” in the Feb. 2011 issue.

 
   
  Accents can be added to acrylic pieces to create a unique look. Photo courtesy of Marco Awards Group.   Johnson Plastics, Minneapolis, MN, offers a line of Frosted Acrylics which are an ideal alternative to glass substrates for signage applications.

Cleaning & Polishing Acrylic
     The brilliance and quality of acrylic can really shine through when the piece has been cleaned after engraving and before presenting it to your customer. Special care must be taken when cleaning acrylic awards, however, because it is possible to damage the piece during the cleaning process.
     First, never use paper towels to clean or wipe acrylic. The fibers in paper towel act like fine sandpaper that can scratch the surface and turn it cloudy. When dusting and cleaning acrylic, use a soft, lint-free cloth, preferably one that is designed specifically for acrylic (Fig. 6).
     As for cleaning solutions, do not use household cleaners such as Windex, 409, Fantastik or any other alcohol- or ammonia-based cleaner. Many of these cleaners can dull or craze the surface of the acrylic with fine cracks. If the piece requires more than dusting, wash it in warm water mixed with a small amount of mild liquid soap, such as Ivory, rinse and dry. There are also cleaners available designed especially for acrylic that gently clean the plastic without scratching, leaving a lustrous shine that repels dust and eliminates static.
     Small scratches can sometimes occur from handling the acrylic during engraving. Special polishes are available to remove fine scratches and abrasions. There are also polishes available for removing deeper scratches. For very deep scratches you may need to sand and/or polish the surface with a buffing wheel. Novus, Savage, MN, manufactures an entire line of acrylic cleaning products, including cleaners, scratch removers, polishing cloths and buffing kits that are available through distributors such as LaserBits, Phoenix, AZ. Johnson Plastics, Minneapolis, MN, also offers products for cleaning and polishing acrylic.
Acrylic Can Be Profitable
     Laserable acrylic products are available in all shapes, sizes and colors, making them perfect for all occasions. Displaying quality examples of new and classic acrylic awards and gifts in your showroom can show your customers just how beautiful these products are.
     Both laser engraving and rotary engraving can be used to produce exquisitely customized acrylic pieces quickly and easily. Cutting and fabricating acrylic sheet stock is also an excellent profit center when you take into account the capabilities of lasers and rotary systems.
     Your engraving equipment is the right tool for creating profits with quality engraved and cut products. Acrylic products could very well climb to the top of your best sellers list in no time!


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