Lately, it seems that what we hear about the most in the R&I industry is laser engraving. There is a constant influx of information about laser engraving—new laserable materials, new applications being developed ranging from engraving photos on stone tiles to lasering gourds (yes, gourds!) and even new types of laser engraving machines entering the market. But if you ask any veteran engraver, chances are that along with that laser that’s busy engraving wooden plaques and marking messages and logos on acrylic awards, there is a rotary engraving machine humming along right with it.
There’s no question that laser engraving has many advantages. It’s a non-contact marking method, so there’s no wear and tear on tools. It creates a crisp, clean, permanent mark in many materials and it’s extremely fast for most applications. Laser engraving is an excellent method for engraving graphics and photographs, today’s equipment is exceedingly easy to operate and maintain, and it can be used to engrave a huge variety of materials and products.
But veteran engravers will tell you that rotary engraving also has many advantages. Unlike laser engraving, this method can be used to engrave on virtually any kind of bare metal and it is capable of making deep and highly precise cuts into many materials, from plastic to brass and stainless steel. Rotary or diamond drag engraving creates a beautiful “engraved” look and feel and you can use it for many specialized applications, from engraving on the backs of watches to creating ADA signage. In addition, rotary engraving equipment is typically less expensive than laser machines.
While some engravers offer both varieties and may favor one engraving technique over the other or offer only one kind, the truth of the matter is that most shops offer both varieties and both methods have their place in the recognition and identification industry. By offering both methods, these business owners cover all the bases and select the method that’s best and most profitable for the job at hand.
While laser technology often seems to take precedence, there are some applications that really require rotary engraving, and there are some applications where rotary engraving may be the better choice. In light of that, this article will highlight a few of those rotary engraving applications that could be a profitable way to get that computerized engraving machine working hard in your shop.
The trend today in architectural signage is decidedly “designer,” a look that is “a cut above” the traditional and the ordinary. There are different sign-making methods used within the industry for achieving this designer look but one that produces a truly unique look is engraved subsurface signage.
Subsurface signs are signs with lettering and graphics below the material surface—the sign’s surface is completely smooth. The appearance of subsurface engraved signage is very attractive—it is both clean and contemporary—and it looks quite different from surface engraved signage (Fig. 1). With surface engraving, you can see and feel the engraved grooves, whereas subsurface signage has the engraved image recessed below the material surface.
Multicolored signs are easy to create through subsurface engraving (Fig. 2). There are hundreds and hundreds of paint colors available and you can also have colors mixed to your customer’s specifications, e.g. to match the colors in a business logo or a company’s decorating scheme.
In addition to an attractive appearance, subsurface signage is very durable and vandal resistant. Because the engraved grooves are protected, the engraved areas cannot be damaged and if the engraved areas are paint filled, they are better protected against peeling and cracking. Subsurface signage is also popular for outdoor applications, such as golf courses and zoos, because weather elements cannot easily reach the painted letters and graphics.
Rotary engraved subsurface signage is usually created by reverse engraving either a clear acrylic blank or a two-ply plastic engraving stock containing a colored back layer and a transparent front surface. Letters and graphics are reverse engraved on the back side of the material and can be paint filled to add more color to the sign design. Other marking methods can be used to created subsurface sign-
age, including screen printing, vinyl lettering and, yes, laser engraving, but rotary engraving has a few advantages and can also provide a different “look.” What’s even better is the process is a simple one. Here are some tips to get you started.
The Materials—Engraving material suppliers offer plastic engraving stock specifically designed for reverse engraving. This two-ply material is typically made of acrylic and consists of a thick clear surface (as viewed from the front) and a thin colored layer on the back. When the colored layer is reverse engraved, the letters and graphics show through the clear base material.
Suppliers offer subsurface engraving stock in a variety of colors as well as matte and glossy finishes. Rowmark LLC, Findlay, OH, for instance, offers reverse engravable plastic lines for rotary engraving including Slickers (with a glossy finish) and Ultra-Mattes Reverse-Engravables (Fig. 3). Gravograph, Duluth, GA, offers Gravoglas 1, a reverse engravable material suitable for both interior and exterior signage applications. As another option, you can use clear acrylic blanks for subsurface signage to create unique and colorful design effects.
Job Setup—When engraving a subsurface sign, you place the sign blank on the engraving table so that the back side of the material is the surface to be engraved. In order for the sign message to be right-reading from the front of the sign, you need to “reverse” or “mirror” the layout. With computerized engraving software (and even CorelDRAW), this is as easy as a click of the mouse—you simply select the option in your software to reverse (mirror) the image. In most engraving software, you will be able to view the reversed image on the computer screen before you engrave it.
One of the advantages of rotary engraved subsurface signage is that this process allows you to achieve two different “looks.” One option is to create a “flat” look where the engraving appears flush with the material backing; this technique more closely resembles screen printing and laser engraving. The other option is to create a “dimensional” look where the engraved characters and designs are dimensional and appear to be raised. This gives the lettering and graphics a 3D look with substantial relief depth. Using a tapered cutter accentuates the 3D look.
Choosing a typestyle will depend, in part, on the look you are trying to achieve. If you are creating a sign with the flat look, consider choosing a multi-line engraving font that has square corner strokes, such as Helvetica, to provide a more contemporary sign design. If you want to create a sign where the engraved areas appear raised, a single-line style such as Gothic or Regular Block is usually a better choice because these fonts tend to accentuate the raised appearance of the characters.
Cutter Selection—If you are engraving one of the acrylic-based sign materials, select a carbide cutter designed for engraving acrylic. To achieve flat-look characters, select a cutter with a small included angle, such as a standard 60 degree cutter.
For a sign with the raised look, a cutter with a larger included angle (80-90 degree) is often a better choice because it will create a more pronounced V-shaped groove that will give the characters more dimension. You might also want to try using a ball-nose cutter, particularly when engraving single-line fonts and vectored graphics. A ball-nose cutter can create characters that have an almost 3D appearance that can be very striking on a sign.
In order to achieve a good clean cut, make sure the rotary cutter you choose is sharp and in good condition. Not only will this provide an overall clean look to the sign, but smooth, burr-free characters are much easier to paint fill.
Engraving Depth—As with front engraving, an appropriate engraving depth for reverse engraving will depend on the type font, character height and cutter angles you are using. In the case of subsurface signage, it also depends on the look you are trying to achieve.
For the flat, non-dimensional appearance you typically want to engrave just deep enough to penetrate the cap layer. A shallow depth will help make the characters look flush with the sign’s back surface.
To achieve the subsurface raised-letter look, you will want to engrave quite a bit deeper. Generally speaking, you want to achieve a relatively wide groove at the mouth of the engraved groove on the material’s back surface. If you are using a rotary cutter with a 90 degree included angle, you can calculate the groove width at the top using this simple formula: 2 x cutting depth + tip size = groove width.
Engraving Technique—There are a few tips to keep in mind to achieve the best results. First, it is a good idea to leave the protective masking on the front (clear side) of the engraving material while engraving and paint filling. This will protect the front of the sign from scratches, nicks and any stray paint. If you are engraving a clear acrylic sheet, leave the masking on the back side of the sign blank as well to protect the material from potential scratches and rub marks from the depth regulator nose. Otherwise, if you are engraving material with a colored cap, you can remove the masking material from the colored side of the material.
Swirl and dwell marks in the bottoms of engraved grooves and visible cutter strokes are potential problems to watch out for when engraving this type of material. Swirl marks are caused by the spinning action of the cutter whereas dwell marks can appear at the points where the cutter enters and leaves the material. To minimize these problems, use a high spindle speed, a slow feed rate (engraving speed) and a short dwell time.
Sometimes when engraving acrylic you may see engraved areas that appear slightly hazy through the clear portion of the sign blank. To make sure the engraved areas appear vibrant after paint filling, some engravers will coat the engraved areas with a clear acrylic spray before adding paint to smooth out cutter marks and eliminate the haze.
Finally, always use a vacuum chip removal system to remove material chips during engraving. By removing chips during engraving, you will prevent them from becoming trapped underneath the depth nose and possibly causing engraving depth variations.
Paint Filling—In order to add color to subsurface signage and produce a professional end result you can optionally paint fill the engraved characters. There are several different types of paint you can use for quality results.
Oil-based enamels are one option and although they have a relatively slow drying time and require mineral spirits or paint thinner for cleanup, these paints produce a quality, glossy finish and are very durable.
Acrylic latex paint is another option. This type of paint is water washable, so cleanup is fast and easy, and it is also durable and resistant to fading from UV light exposure. Acrylic lacquers, like the type used on automobiles, are available in liquid form or in aerosol spray cans, which can be especially convenient.
(Note: Always take precautions when working with flammable paints like oil-based enamels and acrylic lacquers as well as the solvents used for cleaning. Always work in a well ventilated area and keep them away from heat, sparks and open flames.)
Before applying any paint, make sure the sign surface and the engraved grooves are clean. To apply liquid paint, you can use a paintbrush or foam brush. Spray lacquers can be applied using aerosol spray cans or with an airless spray gun.
The number of paint coats to apply will depend on the application method and the type of paint you use. For example, only one coat is usually needed for brush-applied enamels whereas two coats are typically needed for latex paint applied with a paintbrush. In addition, you will likely need at least two light coats when applying paint in an aerosol spray can. After paint filling, carefully inspect the painted grooves for any problems, e.g. areas where the paint does not completely cover the plastic.
Vision Engraving Systems, Phoenix, AZ, offers an optional ring attachment that is compatible with their Max and Max Pro systems; the Viper GE Gift from Xenetech, Baton Rouge, LA, can also be fitted with an optional ring attachment; and Gravograph, Duluth, GA, offers the M20 Jewel engraving system that comes standard with ring engraving capabilities.
Material Type—For most badges, 1/16" or 3/32" thick flexible plastic engraving stock is the easiest material to profile. In addition to being available in a huge variety of colors, achieving smooth, clean edges around the profiled part should not be a problem with this material.
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