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All About Lasers

Copyright © 2018 by Davis Multimedia, Int'l. All Rights Reserved.
As Printed in May 2018, Volume 43, No. 11 of The Engravers Journal
 
Photo courtesy of GCC America, Inc.   Photo courtesy of Gravograph.

    Considering purchasing a new laser? Or perhaps investing in your first laser engraver? This article is intended to serve as a primer to help you become an educated buyer so that you can make the best decision for your business, your budget and your customers’ needs. Here, you can learn the terminology and options available from the various manufacturers, as well as what questions to ask.
    First, we need to define the objects of our discussion. In this article, we will consider four types of lasers: CO2, fiber, dual source and galvo lasers. Each one is different in terms of its characteristics, features, how it operates and the applications it is best suited for. These factors all need to be considered when purchasing a new laser engraver.
What is a laser?
    L-A-S-E-R stands for Light Amplification by Stimulated Emission of Radiation, meaning an infrared monochromatic beam of light which uses heat to engrave, mark or cut various materials. In layman’s terms, it is a device that generates an extremely intense single-color light beam. It then uses special gases or minerals to excite (amplify) the light. When passed through various lenses and pointed at something, this high intensity beam makes a single point of light. This highly focused beam can generate heat which can mark, engrave or cut various materials.
CO2 Lasers
    Lasers are named for the material from which their light is generated. CO2 lasers are, by far, the most commonly used lasers in our industry. Probably 95% of all lasers sold in the personalization industry are CO2 lasers. In the context of this article, we are talking about “commercial grade” CO2 lasers which are equipped with either a metal or ceramic laser tube. These lasers work by exciting the molecules of a carbon dioxide gas mixture in the tube which produces long-wave infrared light.
    The CO2 lasers in our industry use a gantry-type motion system (also referred to as “flying optics”). The motion system itself varies in design from one manufacturer to another, but the basic system is much like a plotter as the laser head moves on the X and Y axes as it engraves or cuts. The advantage to this type of motion system is that it can engrave over a very large area.
    Carbon dioxide lasers are ideal for engraving a wide variety of materials, including wood, acrylic, most engraving plastics, leather, paper, self-adhesive films, coated metals of all kinds, MDF board, rubber stamp material, glass, ceramic, marble, some stone and some brick. With the exception of metal, glass, marble, ceramic and stone, it can also cut through these materials.
    CO2 lasers can engrave most plastics although there are a few that give them problems. PVC, for instance, emits toxic fumes when engraved with a laser which can be harmful to the operator as well as the equipment itself. And ABS plastic is not recommended for laser engraving because it has a lower melting point which can cause it to warp and burn easily. Further, CO2 lasers are not suited for engraving uncoated metals (unless a laser-markable chemical coating is used) and can only mark coated metals by burning off the paint or bleaching an anodized coating.
    CO2 lasers are available in a wide variety of table sizes, starting at around 12" x 16" which is at the small end but still large enough for many awards and personalization projects. If price is your major consideration (and it should never be), then a 12" x 16" or 12" x 18" laser is an enticing option. However, the smallest table size I recommend is 12" x 24". This is mainly because the engraving plastic, engraving metal and self-adhesive films we use are typically sold in 12" x 24" sheets. Having to hack off 6" from these stock materials can result in a lot of waste and limit what we can do when ganging jobs.

 
The Speedy 360 from Trotec Laser Inc. is available as a CO2, fiber or dual-source CO2/fiber laser.   The LaserPro Spirit LS from GCC America, Inc. features pass-through ports where cabinet doors can be opened to accommodate larger items.

   Of course, lasers come in much larger sizes. For instance, 18" x 24", 18" x 32", 18" x 36", 20" x 32", 24" x 36", 24" x 48" and larger are common sizes as they allow for much larger objects or for the ganging of larger objects. Large format lasers are also available for the really big jobs with table sizes such as 59" x 32" and 66" x 32" to name just a couple.
   Of the lasers discussed in this article, CO2s are the least expensive type among commercial grade lasers with a price tag starting at about $8,000 and going up to the $20,000+ range. This is actually quite noteworthy since the early lasers started at about $25,000 and could top $125,000.
   There are a number of major manufacturers of commercial grade CO2 lasers that cater to our industry. They include Epilog Laser (Golden, CO), GCC America (Walnut, CA), Gravograph (Duluth, GA), Kern Laser Systems (Wadena, MN), Trotec Laser Inc. (Plymouth, MI), Universal Laser Systems (Scottsdale, AZ) and Xenetech Global, Inc. (Baton Rouge, LA).
Fiber Lasers
   Fiber lasers are closely related to another type of laser we don’t see much of in our industry but is common in industrial applications—the YAG or yttrium aluminum garnet laser to be more precise. Although fiber lasers differ slightly in light frequency from a YAG, they also differ a great deal in price and size. Fiber lasers are solid state lasers that allow for a much less expensive laser with many of the same capabilities—namely, the ability to mark coated and uncoated metal.
   The term “fiber laser” comes from the way the light beam is delivered to the laser’s lens. As the word implies, it uses glass fibers or tubes much like modern fiber optic phone lines use to generate short-wave infrared light. Although the common wattages used in the personalization industry are 20-50 watts, industrial fiber lasers have increased in power from about 200 watts in 2001 to over 30,000 watts today.
   Our little fiber lasers aren’t powerful enough to cut metal, but they can certainly mark it. Even a 20 watt laser can mark any metal I know of. This includes chrome, all grades of stainless steel, aluminum, gold, silver, brass and titanium. The mark generated is a near black mark that once engraved, cannot be removed. Other materials this type of laser will mark include some specialty plastics such as white ABS, polycarbonates, carbon fiber and many more industrial type plastics. One I especially like is black cast acrylic. A fiber laser marks it with a solid white mark which is great for awards. It does not, however, mark anything transparent such as acrylic or glass.
   One advantage of this type of laser is the pinpoint spot size (the size of the laser beam when it strikes the substrate). Unlike CO2 lasers which typically have a minimum spot size between .003" and .005", a fiber laser can focus down to a much smaller spot. Some report a spot size of less than .001". This allows engraving incredibly small text and details.
   Fiber lasers in our industry are available from most of the major laser manufacturers. Like CO2 lasers, fiber lasers have a flying optics motion system and are available in a variety of bed sizes starting at about 12" x 24" on up.

The PLS 6MW is a fiber laser from Universal Laser systems featuring a 37" x 23" work table. The LaserCELL from Kern Laser Systems is a large format CO2 laser with a 52" x 52" enclosed work area.

   Fiber lasers cost more than CO2 lasers with a starting price tag of about $20,000 and ranging up to $60,000 or more, depending on the size and wattage. Still, this is a long way from the million-dollar price tag for some of the big industrial lasers.
   A note of caution: The light beam generated by a fiber laser has the potential of being far more dangerous than a CO2 laser. So long as it is contained in a fiber rated cabinet, all is fine. Defeating a safety device or trying a pass-through is extremely dangerous. CO2 safety glasses will not protect you from this laser beam and fiber-rated safety glasses can run $600 or more. These are Class 1 lasers when used according to the instructions. Don’t play games with these lasers; they can blind someone no matter how far away they are from the laser.
Dual-Source Lasers
   A dual-source laser, also referred to as a “hybrid” laser, contains both a CO2 and a fiber laser in the same cabinet. There are positives and negatives to this approach that should be considered before buying one. On the plus side, this dual-source technology allows processing mixed materials in one step and can be used to engrave wood, glass, metal, leather, acrylic and more. Dual-source lasers increase the range of materials that can be processed with one piece of equipment for a single investment.
   And while with most hybrid systems you can use both lasers in the same job, you can’t use both lasers at once so if you have a job requiring a CO2 and one requiring a fiber, you must wait for one to finish before you can do the other. Although separate lasers may cost a bit more, the difference could easily be offset by the amount of time you save by being able to run multiple jobs at the same time if you do a lot of work requiring both types of lasers.
Galvo Lasers
   A galvo (short for galvanometer) laser is more about how the beam is delivered to the work piece than it is about the type of laser source. In fact, a galvo can house either a CO2 or a fiber light source.
   Galvos have been around for a long time. The advantage of the galvo delivery system is its speed—a galvo laser is extremely fast. What might take 20 minutes on a flying optics system, might only take 20 seconds with a galvo. This is due to the way the light source is delivered to the object being marked. Unlike the flying optics system used with CO2 and fiber lasers which typically uses a belt/rail to move the laser lens over the material, the galvo directs the laser beam at small mirrors which are controlled by the galvanometer. As voltage is applied to the galvanometer, the mirrors swivel and tilt in order to direct the beam to the material surface and engrave the image.

The LS100 Energy from Gravograph is a CO2 laser with a 12" x 18" table. The cylindrical attachment from Gravograph consists of two rubber grippers to hold a round item. One side rotates while the other spins free.

    In addition to their “lightning fast” speed, galvo lasers require very little maintenance because there are no pulleys, bearings, belts, etc., to deal with. A disadvantage, however, is that the engraving area is typically very small—say 6" square. This makes it perfect for engraving pens and key chains but a poor choice for larger items such as plaques. The problem, if you haven’t figured it out yet, is the angle of the light beam when it is at its extreme position. If the mirror is positioned in the center top of the cabinet and can’t move, then the extreme left or right side, top or bottom, will be much further away than the center so the beam may be striking the engraving surface at an angle of 20°-30°-40° or more. This means the beam is out of focus for the majority of the engraving and we can get away with this to some degree but if we try to stretch it too much, it loses all usable power.
    Last year, Epilog Laser introduced a pulsed fiber galvo laser system in an enclosed cabinet that features “a unique dynamic-focus lens technology.” According to Epilog, this technology enables engraving capabilities over a 24" x 24" area which is significantly larger than traditional galvos.
Purchasing Considerations
    I have used lasers made by most of the laser manufacturers in our industry and even written reviews on them, finding all to be good machines and worthy of your consideration. As for which one is best, that depends on many factors, not the least of which being what you want to do with it. Each brand comes with bells and whistles others may not offer and there are many features and options to consider, including everything from red dot pointers to air assist, but the most important factor of all is service and support!
    All these companies offer nationwide support through a U.S.-based headquarters and that’s fine, but the real issues are usually between the customer and whoever sells or installs their laser. That is the person a customer expects to live up to the reputation of the company.
    In the final analysis, it isn’t just the reputation of the laser company itself, it is the reputation of the individual salesperson so when considering a laser, check out who is going to be giving you training and support on behalf of that company. Take the time to check them out with other customers before you decide what to buy. Remember, “Service is everything!”
    That being said, there are a variety of other things to consider when purchasing a laser. Some of these considerations will apply to certain types of lasers more than others, but they are all important to consider when making a laser purchasing decision.
    Speed: Should speed be a consideration when buying a laser? Absolutely… kind of. Speed is important, but speed is only useful if you have enough laser power (wattage) to take advantage of it. Taking advantage of a super high-speed laser depends too on what you are marking or cutting. For instance, if you have a 25 watt CO2 laser and need to engrave microsurface engraving plastic, you can probably crank up the speed and achieve a good cut. This is because the microsurface material requires little power to engrave through the “micro-thin” cap layer. Change that over to deep cutting wood, and you will likely have to slow down the laser to a crawl to get any decent depth. With materials like wood, it is better to have a lot of power rather than speed. Speed is often used as a sales point to make one laser look better than others. It’s not that speed isn’t important, but it is only important when combined with the material being marked or cut and the amount of power it has to work with.

Auto focus can be accomplished in several ways. Here, Gravograph uses a removable plunger to find the surface and adjust the lens accordingly. Anyone planning on doing a lot of cutting will need a cutting grid. Shown here is a cutting grid available from Gravograph.

   Power: Unlike speed, power is one of the most important factors to be considered. The power rating of a laser is always tied closely to price, so it becomes a factor on at least two fronts, and when you consider the materials to be marked, it ties to three factors.
   Lasers are rated by wattage, typically between 25 and 150 watts for mid-sized CO2 lasers in our industry and 20-50 watts for fiber lasers. Large format lasers, like those available from Kern Laser Systems, Trotec Laser and Universal Laser, are available in a broader range of wattages, e.g. 30 to 400 watts.
   There are several things that are important to understand about wattage. Although the short answer to how much power do you need is “all you can afford,” that isn’t always the best answer. For instance, if you plan on engraving a lot of wood or plan on cutting most any material over 1/8" thick, you should consider a high-power laser—probably 100 watts or more. If, however, you plan on engraving coated metal for award plaques, anodized aluminum or acrylic, you don’t need all that power—probably 25-35 watts is plenty. If you want a general-purpose laser that can do a little of everything, a 50-60 watt laser should be considered.
   So, why shouldn’t everyone just buy a 100 watt machine and dial down the power setting? Although having lots of power is good, sometimes it’s too good. The problem with all that power is when you want to engrave something delicate like microsurface plastic or a self-adhesive film like Rowmark LaserLIGHTS. Having to tone down a very hot laser can be tricky. You may find yourself running at 100% speed and only a couple percent of power. Engraving something like paper may be almost impossible without burning it up. Sometimes having too much power is worse than not having enough. At least when you don’t have enough power, you can usually run multiple passes to make up for the lack of power.
   Remember, too, power is expensive. Lasers are typically priced according to their power rating. This means a 100 watt laser might cost three times as much as a 35 watt machine and twice as much as a 50 watt laser.
   One final thing to understand about power is that all CO2 lasers begin losing power with use and over time. Most laser tubes from industry manufacturers have a two-year warranty but, generally speaking, many engravers report a lifespan of three to six years. This, however, can vary. The point is at some point your laser will begin losing power and you will need to recharge/replace the tube.
   User Replaceable Tubes: Many modern lasers have a laser tube assembly that can be replaced by the end user. This saves considerable money when it comes time to replace an old laser tube or to upgrade to a more powerful tube. Although, tubes are generally “recharged” and reused multiple times to reduce cost, you can expect to pay $1,500 to $2,500 for a recharged or replacement metal tube.
   Table Size: The second major factor in determining the price of a laser is usually the size of the engraving table. The smaller the table, the lower the price. Although this may not always be true when comparing lasers from one brand to another, it will certainly be true within a single brand.
   One issue when considering the table size is the actual footprint of the machine and what size door is required for it to gain entry into your shop. Since many shops have a 36" doorway, this becomes a major consideration. If stairs are involved, then weight also becomes a consideration.
   Price: Price is usually our first consideration when purchasing equipment, but it shouldn’t be—especially when considering a laser. We have already talked about two of the major factors that determine price: size and power. Of course, there are other considerations as well which usually involve accessories. Some lasers come standard with expensive cutting grids while others offer them as an option. Features like internal lighting, air assist, cylindrical attachments and cameras will affect the price, so determining what is included and what is an option can make a drastic change in the bottom line.

The G2 Galvo is a galvo laser from Epilog Laser that features a 24" x 24" engraving area.

   Although price is always important, it should only be considered after you determine what you want to do with the laser. Buying a laser that is too small, either in size or power, is false economy and will only end up costing more in the long run. Don’t be too tempted by lasers that offer ridiculously low prices. Lasers cost a lot of money to build and despite what many people think, the profit margin of a laser isn’t nearly as much as you might imagine. A laser should be considered an investment. They are a tool to make money. Determine first what you are going to mark or cut and how big your jobs will be, both in size and quantity, and then determine the power and size of the laser you need to accomplish those tasks. After that, you can determine the price range that is reasonable and justifiable for your shop. If you determine that all you need is a modest 12" x 24" 50 watt laser, then fine. But don’t go with a small laser if what you really need to make money is a much larger and more expensive model. Become an educated buyer before you get out your checkbook.
   Exhaust System: Every laser requires a fairly powerful exhaust system to remove fumes and fine particles from the laser/environment that could otherwise pose health and safety risks to you and your equipment. This can be best accomplished by using a system that exhausts the airborne contaminates to the outside using a metal duct and a blower. This is the safest way to vent the fumes, at least as far as the breathability of your shop is concerned. Blowers should be completely air tight with a 4" inlet and 4" outlet and provide roughly 600cfm of air removal from the laser. The cost for a typical do-it-yourself exhaust system is about $300-$500.
   Another exhaust method that some people use is a self-contained filtration system. A few of the most common brands include BOFA, Sentry Air, Fumex and Teka. Vent-less filtration systems consist of activated charcoal and various filters to remove airborne laser byproducts from the air and vent clean air back into the work environment. These are expensive, starting at about $2,000, and are not as safe as an exhaust system that vents outdoors.
   If you do decide to use a vent-less system, be sure to take the necessary safety precautions. Be sure the filtration system is designed and sized properly for your environment and applications. Routine maintenance, such as changing the filters and recharging the activated charcoal, is extremely important. If you engrave materials like wood, make rubber stamps or cut acrylic, you will need to replace the filters much more often. Also, some materials are known to produce corrosive or toxic fumes when lasered which are hazardous to human health so it is crucial that you know precisely what you are engraving and avoid dangerous substrates.
   Air Assist: This is a must for engraving wood, making rubber stamps and cutting almost anything. The purpose is to blow down any flame-ups that might occur. This is not only a safety feature, it also protects the item being engraved or cut from excessive flame and smoke damage as well as the laser’s optics. It usually requires you to purchase an air compressor to provide a continuous air stream that is aimed at the spot where the laser beam meets the work. Like other features and options, the way that air assist works can vary from manufacturer to manufacturer. For example, on one brand air assist consists of a small tube that bends down under the lens assembly. Another pumps the air through a nozzle over the lens allowing both the laser beam and the air to exit a small hole at the bottom of the nozzle.
   Red Dot Pointer: Standard on most lasers in our industry, this visible red laser beam is intended to show the exact placement of the lasered mark on the substrate without actually engraving it. The red dot pointer allows you to see where on the material the engraving will take place, without wasting time and materials through trial and error.
   Emergency Shut-Off: Problems that are serious enough to require hitting an emergency shut-off switch are rare with a laser, but they can happen. It is usually human error that causes a fire in a laser or some other catastrophic event, but having an emergency shut-off button outside the laser can make the difference between a scare and a thousand-dollar repair. Not at the top of my list, but nice to have.

 
 
  This break-away shot of an Epilog Laser lens assembly shows the auto focus plunger (circled). It also shows the air assist delivery tube (the bent tube).  

   Internal Lighting: Although we went for decades without lights inside our lasers, we didn’t know what we were missing. Having good lighting can be incredibly helpful at times. Not all lasers have this option or feature, but it is well worth considering.
   Auto Focus: Typically, the depth of field for a laser is fairly small. With a 2.5" lens, it is about 1/4" so accurate focusing is extremely important. All lasers come with some form of manual focusing tool, but many lasers now also have auto focus as a standard feature. This doesn’t always work on substrates such as glass or clear acrylic but for most substrates, it is very accurate and is a time saver. Each manufacturer has come up with their own method for accomplishing this but it usually incorporates a sensor mechanism that will “sense” the surface and correctly set the focusing distance. With some systems, you can also input the material thickness into the driver software for auto focusing. Auto focus is a handy time-saver, but certainly is not mandatory.
   Software: Each manufacturer offers their own concept of a print driver/software. Some use a simple print driver while others offer some version of design software or job control software. For example, Epilog offers a job manager along with their driver software. Xenetech and Gravograph offer a proprietary design program with their driver while Trotec offers their own version of a job manager. All the lasers from these manufacturers can print directly from CorelDRAW, Adobe Illustrator or other graphics software.
   Fire/Temperature Sensor: A few lasers come with an internal fire suppression system that either shuts down the laser when it senses too much heat or flame and/or sprays the inside of the laser with a fire retardant should the unthinkable occur. If you plan to do a lot of cutting and you are using a high-power laser, this should be a consideration.
   Pass-Through Ports: Some lasers have a pass-through port on one or both sides of the cabinet to accommodate items too large to fit within the laser cabinet. They are commonly used to engrave things like baseball bats and golf clubs. Although these are convenient, they can also be dangerous. Lasers are required by the FCC to come with a variety of interlocks to keep users from contacting the laser beam. When you open a door on any Class 1 laser, the beam will automatically turn off. When you engrave with an open door, your laser becomes a Class 4 laser (dangerous) because the open door may allow a reflected laser beam to exit the cabinet. Should this happen, and it hit someone in the eye, they could lose the sight in that eye. Although this is highly unlikely, and I have never heard of it actually happening, it is possible. At the very least, if you take advantage of this option, everyone in the room should wear laser protective glasses at all times.
Additional Laser Accessories
   All laser companies offer a variety of additional laser accessories to make their machines more functional. These are usually not included in the base price although most companies will negotiate reduced prices on these items to close a sale. Note, too, that not all accessories are available for all types of lasers so you will need to do a little research if there are certain accessories that you want or need.
   Cutting Table: A vector/cutting table is a must for cutting wood, plastic or acrylic. A cutting table typically consists of an open honeycomb-type grid that, when placed on the laser’s worktable, allows the laser beam to pass through the material and reduces the amount of burning and smoke created as the laser beam is reflected from a solid table. A cutting table also allows air to flow beneath it as the material is cut. Vector cutting on a cutting table creates cleaner cuts and better edge finishes with less melting and burning, which are common problems when cutting certain materials. Some lasers come with the vector table integrated into the laser and connected to the exhaust system in such a way the smoke is vented through the openings and directly out of the laser. Others are designed to stand above the engraving table so smoke can be pulled from beneath the vector table and out the exhaust. Check with your laser representative for their recommendations.
   Vacuum Table: Some lasers come with a vacuum table built into the laser, while with others it is an option. A vacuum table uses suction to keep flimsy items, such as fabric, paper and ultra-thin engraving materials, flat during lasering. If you plan on marking or cutting very thin materials, these tables can be very helpful.

   Cylindrical Device: Available for most lasers, this tool allows you to engrave cylindrical objects such as wine bottles, stemware, cups and glassware. There are two basic designs for these: One is a friction driven device that consists of rollers that hold and roll the product as it engraves. The other is more like a vise which holds round items at either end and then rotates it as needed.
   If roundwork is something you want to do a lot of, there are several considerations you should keep in mind. First, the height capability of your laser is crucial to how big an object you can mark using this device. This is especially true if the object has a handle or other protruding parts. Second, you may want to consider a second lens having a larger focal length, especially if the items you want to engrave have handles. A typical 2.5" lens may not be able to engrave a coffee cup with a handle because the handle will crash into the lens while engraving. There are workarounds for this if the handle isn’t too big but a beer stein, for instance, would never work. For that you should have a 3" or 4" lens so the lens assembly is well above the body of the cup. This allows the handle to move freely under the lens assembly without crashing into it.
   Lenses: Most lasers are capable of accepting different size lenses. Size, in this case, refers to the focal length, not the physical size. Common sizes for a CO2 laser include 1.5", 2", 2.5", 3" and 4". The smaller the focal length, the smaller the beam size and the longer the focal length, the larger the beam size. The vast majority of users never buy a second lens since the lens that comes with the laser is adequate for most jobs. These other lenses are typically used for specific applications.
   Camera/Optical Recognition System: The addition of a camera to some of the higher-end lasers is new. An optical recognition system is used to find a reference point on the substrate (such as a registration mark) and then proceed to find and follow a particular line, cutting it out as it goes. This allows the user to cut out a pre-printed piece of acrylic, paper or wood product.
   Dual Head: A few manufacturers offer optional dual-head capabilities that will split the laser beam in two, 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 production booster.
Final Notes
   All of the lasers we have discussed here are air-cooled lasers. No chillers or water cooling systems are needed. All the lasers discussed here are Class 1, fully enclosed lasers with the exception of those with pass through ports that make them Class 4.
   Hopefully, this overview of lasers will be helpful to you as you consider the purchase of a new laser, be it your first or an additional one. There are a number of machines on the market for most any application. For more information about what’s available, check out EJ’s online “Laser Engraving Buyer’s Guide” at http://www.engraversjournal.com/charts.php.


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