Laser Specifications
(View Laser Specifications chart online at www.engraversjournal.com/charts07)
     The next chart includes features directly related to the laser beam. The beam is the actual cutting tool, so this is an important part of any laser engraving system.
     The first column in the chart, Beam Power, indicates the power or intensity of the laser’s beam, a very important feature of laser engravers. The intensity of the laser beam is commonly expressed in terms of wattage (per square centimeter). Generally speaking, the higher the wattage the more powerful the laser beam. In simple terms, more power means the laser can engrave faster and/or deeper in a given amount of time. Keep in mind, however, that how fast/deep a laser can engrave depends on other factors as well, including the material being engraved.
     The laser wattage listed in the Beam Power category indicates the minimum rated wattage guaranteed by the laser manufacturer. Laser tubes can vary in the amount of wattage they actually output. A laser rated at 25 watts, for example, might actually output 30-32 watts or even as much as 40 watts; actual wattage will vary from one laser tube to the next from the same manufacturer. In other words, if you purchase a 25 watt laser, you will probably receive a laser with slightly more power. In this case, the 25 watt rating is merely the minimum output level guaranteed by the manufacturer.
     Note, too, that the power of a laser is also dependent on the type of laser (mentioned in the Laser Unit Specifications chart). For example, the light coming from a diode-based YAG laser is approximately 10 times more efficient than the light coming from a YAG with a flash lamp or a thermal light bulb. And a fiber laser can be up to 50 percent more efficient than an Nd:YAG or CO2 laser. It is possible for a 12 watt diode laser to mark faster than a 120 watt flash lamp laser because the diode laser has higher energy density at the workpiece.
     Today, most manufacturers offer the ability to upgrade a system’s power without having to purchase an entirely new system (noted by Wattage Upgrades in the online chart). On some machines, changing to a higher wattage laser can be as simple as loosening a few screws and replacing the fully modular laser unit. You can either do this yourself or, if required, send your equipment to the factory for the upgrade (the chart lists these options).
     Being able to upgrade your laser greatly increases the versatility of the machine and can be a fantastic cost-saving benefit. For instance, some engravers initially purchase low-powered lasers to save money and/or because they didn’t need a lot of power for the type of engraving they were doing at the time. If, however, down the line they find that they want or need more power, an upgrade is much easier and much less expensive than replacing the entire machine.
     Beam Motion, the next listing in the chart, describes the way the laser beam moves while engraving an image. Vector movement on laser systems is the same as the table and spindle movements found on most computerized engraving machines, i.e. simultaneous X,Y movement creating a “cutter path” capable of following a shape. Vector engraving is extremely efficient for engraving certain images such as a border around a plaque or character outlines. Additionally, vector motion is necessary in order to do any cutting/profiling with the laser. Because this type of laser is capable of simultaneous X,Y movement, borders and outlines are engraved in one continuous motion.
     Raster motion describes a back-and-forth movement of the laser head. During engraving, the laser beam carriage moves from the top to the bottom of the work area while the beam oscillates left to right, i.e. it is a back-and-forth scanning motion starting at the top of the item and moving toward the bottom. As the beam moves from left to right, it is turned on and off to engrave the image. Raster scanning works very similar to the way a picture is formed on a black-and-white TV set, where a series of lines are drawn on the screen that collectively form the TV picture.
     Today, unlike a few years ago, all of the systems that use this type of beam motion are capable of both vector and raster engraving capabilities. However, a third type of laser beam motion, one that utilizes a galvanometer, has become much more prevalent in this industry. With conventional engraving lasers, the motion control system typically consists of a belt/rail that moves a small lens over the material to be engraved. This is commonly referred to as a “flying optics” motion control system. With galvanometer-based systems, the laser beam is directed at small mirrors which are controlled by the galvanometers. As voltage is applied to the galvanometer, the mirrors swivel and tilt in order to direct the beam to the material surface and reproduce the image. As a simple analogy, imagine holding a mirror and reflecting sunlight off of the mirror onto a wall, then swiveling your wrist, allowing you to “draw” a character on the wall with light. A laser with a galvanometer works in a similar manner.
     A major advantage of these so-called “galvo” lasers is speed; essentially, they are “lightning fast.” Galvanometer lasers support both vector and raster engraving, which means users can achieve the same type of engraving in less time. It is estimated that vector engraving with a galvanometer laser is 75 to 100 times faster than vector engraving with conventional flying optics motion technology while raster engraving is at least two times faster. What’s interesting about raster engraving with this technology is that instead of scanning across an entire piece of material and engraving small pieces of each image, a laser with galvanometer motion control will actually engrave images
separately, eliminating unnecessary motion.
     Another advantage of this technology is the fact that it requires very little maintenance. Conventional laser motion works with pulleys, bearings, belts, etc. that need to be maintained and periodically replaced, whereas a galvanometer system basically has no maintenance except for the lens.
     The down side to Galvanometer-based lasers is that they cost more than conventional lasers. They also have a relatively small maximum working area (area that can be engraved in one setup) of up to 8" x 8".
     In addition to wattage, another factor determining the power of a laser is the spot size of the beam. As described earlier, a laser beam is typically focused and concentrated to a pinpoint size through a special lens which determines how much light is present in a specific area. For example, 40 watts of light distributed over a .002" diameter spot has substantially higher energy density (power) than 40 watts of light distributed over a .006" area.
     Most manufacturers offer interchangeable lenses for their equipment, enabling you to vary the spot size from around .003" on up, as shown in the chart under Standard Lenses.               
     Typically, you receive one type of lens with the laser and others are optional. (Note that some manufacturers have described their lenses in terms of focal length, nominally the distance from the lens to the material being engraved, e.g. 1.5", 2", etc.)
     In addition to affecting the laser’s energy density, the ability to vary the spot size of the beam is analogous to using different cutter tip sizes in rotary engraving. Smaller beam sizes provide the ability to achieve intricate detail such as very small type, e.g. 5 point type, rubber stamps and halftone photographs. On the other hand, larger spot sizes enable the machine to rout out large image areas more quickly since fewer cutting passes are needed.
     Several manufacturers have introduced Special Lenses, including high resolution lenses and lenses for engraving uncoated metal with a CO2 laser. High resolution lenses typically focus the lens to an extremely small, consistently-shaped spot; the result is extremely detailed engraving. The “uncoated metal” lens refers to a new lens developed by manufacturers to allow a CO2 laser to mark uncoated metal for applications such as marking barcodes and UID Data Matrices.
     The optical system is an area within the laser industry that continues to see improvements. For instance, Epilog introduced the new Radiance Optics feature this year as a standard feature on several of its systems. According to the company, this new feature produces a smaller spot size and a rounder, more consistent beam for better engraving and cutting across the entire work area. It also produces a higher power density which allows users to mark on some bare metals.
     One characteristic you might want to consider when purchasing a new machine is the way in which you focus the laser prior to engraving. Focusing involves positioning the lens at a specified distance (focal length) away from the material surface to be engraved. The distance will vary with the focal length and the spot size of the lens you are using. On most units, focusing is accomplished by adjusting the table position with the help of a motorized height adjustment (“manual” in the chart), a feature which automates the table movements and allows you to quickly adjust the table position.
     Today, most units also offer automatic focusing as a standard feature. Automatic focusing usually incorporates a sensor-type mechanism that will “sense” the correct focusing distance. (Others work based on a material thickness that you enter into the software.) All you have to do is place the material on the worktable and the machine automatically positions the table so that the workpiece is the correct distance beneath the lens. This feature is very convenient and can be a real time-saver.
     Another time-saving feature, at least for some jobs, is a Beam Splitter. Many manufacturers now offer optional dual-head capabilities that will split the laser beam into two separate beams, allowing you to engrave two identical pieces simultaneously. For example, on a 100 watt machine you can use the dual-head option to create two 50 watt beams. If you have a large order for identical or nearly identical items, this feature can be a great production-booster since you can use one laser to engrave two items at once.

The XLE 2436 is a freestanding CO2 laser system from Xenetech Global, Inc. capable of engraving speeds of 75 ips.				The Laser Cylindrical Attachment is an optional accessory with Xenetech's XLE 2436, which allows engraving on mugs, glasses & other round items.

Trotec Laser’s Fine Marker Hybrid contains both CO2 and YVO4 lasers in one unit.				HSE (High Speed Engraving) is the newest gantry design from Kern Electronics and Lasers Inc., combining fast engraving speeds with consistent beam power and quality across the entire tabletop.

Laser Marking Features
(View Laser Marking Features chart online at www.engraversjournal.com/charts07)
     The final chart in this Guide describes each system’s Laser Marking Features. These are typically operator-definable features that allow you more control over the laser engraving process.
     As shown in the chart, many of the computer-controlled lasers have a feature known as Proportional Power. This control automatically changes the power of the laser beam by linking the laser’s pulses with the speed of engraving. For example, in vector mode the laser operates at full speed when engraving straight lines, but slows down when cutting a curve. Without proportional power, this action would result in deeper cuts when cutting curves than when cutting straight lines. The proportional power feature increases/decreases the laser power as necessary, e.g. power is decreased when engraving curves and/or increased when engraving straight lines. This feature is very useful as it eliminates variations in depth and line widths.
     Raster-Only Mode is a software setting that instructs the laser to only engrave in raster mode and ignore any vector lines in the image. This is primarily used when lasering clip art. CorelDRAW clip art, for example, is known to have “hidden” vector lines in many images. When these lines are engraved as vectors, the result is usually very unattractive—the image is often distorted and, in general, it looks odd to have “stray lines” within an otherwise rastered image.
     Another feature associated with raster engraving is called Optimized Raster Engraving. Laser engravers with this time-saving feature will automatically optimize the engraving speed, i.e. the laser engraves in the areas where an image exists and then skips the blank spaces between image areas. This feature can substantially reduce engraving time since the laser “scans” only those areas to be engraved rather than the entire layout.
     Memory Buffer is a feature found on most laser systems that enables users to download several jobs to the engraving unit in order to free up space on the host computer. With some systems, the buffer will also display information such as the selected laser power and engraving speed for the job.
     File Compression is another handy feature because it automatically “compresses” files before they are downloaded to the laser. This reduces the amount of time it takes to send a job to the engraver while also reducing the amount of memory the file takes up in the buffer.
     Auto Halftones is a software feature that is typically built into a laser system’s driver software. It’s designed to automatically generate halftone images from artwork and photographs. In order to laser engrave a photograph, it must first be converted into a halftone (a series of various sized dots that the laser can engrave). This usually involves importing the image into a separate software package and applying a “halftone screen” to create the dots. Automatic halftoning eliminates this step by automatically applying a halftone screen based on the engraving resolution selected by the user.
     Some lasers also feature a sort of “halftoning” option known as “dithering.” Instead of applying a traditional halftone screen to a photographic image, the dithering technology applies a random dot pattern, which looks more like lines as opposed to dots, creating a more realistic rendering of the photo. This is an especially useful feature to have on your laser if you do any type of photo engraving.
     Indicator/Spotting Beam, briefly mentioned earlier, is a convenient feature that allows users to visually check the position of their layout on the workpiece without actually lasering. The feature is essentially an indicator light that shows up on your work so that you can see where on the material the engraving will take place, without wasting time and materials through trial and error.
     The specifics of how this feature actually works will vary among systems. For example, on some units, you can direct the indicator beam to different areas on the workpiece and display (e.g. on a LED readout) exact X,Y coordinates. On others, you can put the laser through a “dry run” with the cabinet door open, causing the beam to simulate the engraving or cutting job. (The inclusion of this feature may require additional safety precautions. Check with the manufacturer for specific details regarding this feature.)
     Many lasers have a set origin, i.e. the reference position on the laser’s worktable. For instance, many lasers in this industry use the upper-left corner as the point of origin. Relocatable Origin, the next feature in the chart, is used for changing the origin position. This is helpful when you’re engraving odd or non-square items, e.g. where’s the upper-left corner of an obelisk? In a case like this, changing the origin to the center, for example, can greatly simplify the setup process.
     Automatic Focus/Material Thickness is a sophisticated tool that causes the laser to continually focus during engraving (similar to a Z-probe/sensor on a computerized engraving machine). This prevents any depth variations in uneven materials. In essence, it allows users to engrave materials/items that are purposefully uneven in shape, e.g. a tapered glass or a bumpy surface, with no variations in engraving depth.
     Software-Adjustable Table Height is a new feature that represents some of the innovative technology available today. This feature will automatically adjust the table height/focal distance between engraving passes, e.g. to automatically cut through thick material.
     A newer laser engraving feature, called Bottom-Up Engraving, gives laser users the ability to engrave a job from bottom to top as opposed to the traditional method of engraving from top to bottom. This feature was developed for engraving materials that generate excessive smoke, e.g. rubber stamps, since it greatly reduces the amount of smoke that’s drawn over the already-engraved area, ultimately saving you cleaning time. It’s also useful for lasering colored materials, such as white plastic with a bright red core, where red soot could be dragged over the white plastic causing discoloration.
     The last feature in the chart is 3D Engraving. In laser engraving as in mechanical engraving, 3D effects are accomplished by varying the depth of cut. This is achieved by raster scanning an area and then firing the laser at different power settings at each X,Y position. Greater wattage provides a greater degree of relief. Also, the more depth variation you have, the greater the three-dimensional effect.
     The last column in this chart lists any specialized features the manufacturer chose to highlight. This is an area where manufacturers can highlight newly added and special features available on their systems that are not listed in any other categories. Contact the manufacturer directly for more information about special features.
Conclusion
     “As in almost any industry, laser systems will continue to expand at both the low and the high end,” says Epilog’s Mike Dean. “To satisfy the myriad types of applications, manufacturers will need to offer more system sizes and wattages, more price points and more types of laser devices. That is, instead of just a CO2 system, manufacturers will need to offer fiber, YAG and other types of lasers. For the industrial market, the ability to incorporate laser systems into highspeed production lines will become more and more prevalent as laser technology is adopted by the industrial world.”
     When it comes to laser engraving, one thing is for certain – it has made its mark in the industry and it’s here to stay. Each year we have seen new improvements and a better selection of equipment. Manufacturers continue to step up to the plate by offering the types of equipment that retailers need to get the job done. There’s no doubt that laser engraving continues to be a profitable adventure.