CAMERA/OPTICAL RECOGNITION SYSTEM: One of the really neat and relatively new technologies available is the ability to print something with one system and cut it out with another. For example, you could use a UV printer or sublimation to print custom key chains onto a sheet of acrylic and then use your laser to cut them out.
There are many different applications for this process. You can precisely vector cut items that have been preprinted, such as sheets of digitally printed transfers, labels, membrane switches, signs, name badges, models, decals, puzzles, cards, boxes, novelties and stationery. What these optical recognition systems do is provide pinpoint accuracy in the recognition of the two images even if the printed image is inconsistent or skewed on the material.
Using an optical recognition system on your laser allows you to do this with ease. These are now being offered by all of the major laser manufacturers, and the beauty of this technology is that it pretty much automates the laser cutting process which can save you loads of time.
The process begins with a substrate that has been printed with an image. There are, of course, a variety of technologies that you can use to print full-color images onto sheets of material. For instance, UV printers do a great job of printing full-color images and photographs on all kinds of substrates including wood, plastics, acrylic, leather and paper. Sublimation is another full-color printing technology. Sublimated materials such as hardboard, fiberglass reinforced plastic, sublimatable plastics like DyeFlex and sublimatable acrylic can be cut out with a laser, as can items that are screen printed. Things printed with regular off-the-shelf inkjet and laser printers which might include card stock, paper, foils or decals can also be cut with a laser.
Once your items are printed, you can use your laser’s vector cutting capabilities and an optical recognition system to cut them out. The specifics of how these systems work will vary somewhat depending on the manufacturer, but they all work on the same basic concept.
||Laser manufacturers, such as GCC America, Inc., offer optical recognition systems for cutting preprinted items with a laser.
You start by creating the artwork to be printed and then add in standard laser cut lines (.003" line thickness) around the shapes to be cut and a number of registration marks, depending on the complexity of the job. After placing the printed material on the laser bed, you send the cut lines/registration marks portion of the art to the laser and the camera automatically reads the registration marks and applies the cutting data to create a cutting path to precisely cut out the shapes in a way that provides perfect image registration with the surface-printed graphics. Since the camera and computer are doing the work, it doesn’t matter where or how the material is placed in the laser. In other words, even if the sheet of material is deliberately skewed in the laser, the optical recognition software will adjust the cutting path of the vector cut to provide perfect image alignment.
The benefit of using a camera system is that it completely automates the laser cutting process. If you are doing a lot of this type of work, it is definitely an option to consider.
BEAM COLLIMATOR: Some laser systems now have a feature known as a beam collimator. To understand this device it helps to understand that almost all light sources create a beam of light that diverges as it travels away from the source. In other words, the light rays spread apart so the spot it projects grows in diameter but also diminishes in intensity as it travels from the light source.
A beam collimator is an optical lens assembly that gathers and redirects divergent or convergent incoming light rays and produces relatively parallel light output. Improving the directionality of the laser beam produces a laser spot that is more consistent in size, shape and laser wattage over greater distances. Because the laser power varies over the table’s area, providing more power closer to the laser source than farther away, a beam collimator is especially desirable on lasers with a larger table size doing large coverage areas.
FIRE/TEMPERATURE SENSOR: Some laser manufacturers offer fire or temperature sensors as an extra safety measure to protect you, your building and your equipment. Some materials, such as acrylic, can catch fire easily, particularly during cutting. A fire or temperature sensor generally utilizes a photocell to detect flames or a temperature that exceeds a critical value and then shuts down the machine or emits a warning sound to alert the operator. With some, the sensor is adjustable to set it just beyond the threshold of the material and can be turned off when engraving some materials that inherently produce flames during engraving. Either way, it’s a good option to have for safety’s sake.
LASER POWER METER: Laser tubes are generally rated at plus or minus 10 percent of their rated output. This almost always swings to the high side of the scale with a new tube, meaning that a 30 watt (rated) tube typically puts out from 30 to 33 watts. Some 30 watt tubes have even higher power output. There is no hard and fast rule on how much power a tube may put out, just that it will be at least the rated power.
A laser tube’s effective wattage can fluctuate over time and tends to go down as the tube ages. Monitoring the output may be important. Also, some shops have multiple lasers and measuring the output can help to balance the settings from one laser to the next. For example, if you have two 50 watt systems and one is putting out 50 watts and the other is at 58, you’ll have to fine tune your speed and power settings to get similar results. There may also be occasions when you want to troubleshoot a potential or real problem with your system.
|Laser markable coatings like CerMark allow you to engrave bare metal with a CO2 laser. Photo courtesy of Epilog Laser.
||The best way to measure your laser power output is by using a laser power meter.
||An exhaust system is a must for laser engraving. Shown here is an exhaust fan available from Johnson Plastics Plus.
If you want to know how much power your tube is really putting out, you can measure it using a laser power meter. There are two types of laser power meters available: a digital meter and a heat sink type which looks like an aluminum block with a special thermometer. Both will work but the digital meter is what most laser system and tube manufacturers use and it has been proven to be very reliable. You can use the meter to make reading points to determine the power available on your laser system. Typically, you will make two measurements. The first and most accurate will be measured as the laser energy exits the tube. The second and easiest to measure is the power on the table after the beam has reflected off the mirrors. Although the latter may not be the closest value to the rated output of the laser, it can indicate beam alignment problems or some other problem in the optical path. In any case, a laser power meter can be a very handy tool to have.
VACUUM TABLE: Some lasers come with a vacuum table, 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 to produce more accurate engraving and cutting. If you plan on marking or cutting very thin materials like Rowmark Lights or thin engraving plastic, paper or card stock, these tables can be very helpful.
INTERNAL LIGHTING: Some lasers come with internal lighting (usually LED) to provide good illumination during the setup and to help view what is being engraved. This is an extremely helpful option.
EXHAUST SYSTEM: All lasers require a fairly powerful exhaust system to rid the laser/environment of fumes and other particles that can pose health and safety risks to you and your equipment. This can best be accomplished by using a system that exhausts the airborne contaminates to the outside using a metal duct and a blower, much like a big vacuum cleaner. This is likely the safest way to vent the fumes, at least as far as the breathability of your shop air is concerned. There are many sources for these exhaust systems to the outdoors, but most are very similar. Quality One Engravers, Rancho Cucamonga, CA, Johnson Plastics Plus, Minneapolis, MN, and most laser manufacturers offer a system or you can design and create your own using components available locally.
Another option is to use a self-contained system like the ones offered by BOFA Americas, Staunton, IL, a company that specializes in laser extraction. These air filtration systems use a series of filters and activated charcoal to eliminate odors and remove particles of smoke. Although the vast majority of people still use a blower that exhausts all the laser fumes to the outdoors, there are some people who are switching to a self-contained unit for a variety of reasons. Some retail facilities don’t allow you to cut a 4" hole in the wall or roof for the exhaust vent. Some larger communities have outlawed any exhausting of gases into the environment and still others use their lasers either as a portable unit or in places like shopping malls where outside venting is impossible.
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. Note, too, that how often you should perform maintenance such as replacing the filters will depend on what you are engraving. If you engrave wood, make rubber stamps or cut acrylic, then you will need to replace the filters much more often.
It is important to note that these filtration systems are designed to remove smoke, odors and particles. However, some materials are known to produce corrosive or toxic fumes when lasered which are hazardous to human health. Therefore, it is crucial that you know precisely what you are engraving (no PVC or other toxic materials).
For a more in-depth look at air filtration systems, read “What You Should Know About Laser Filtration Systems,” Sept. 2010.
|Photo software, such as 1-Touch Laser Photo from Universal Laser Systems, can help you process photos for lasering.
HOMEMADE JIGS: Lasers offer a huge advantage over rotary engravers in that they don’t actually need to “grip” whatever they are marking. This means that most objects don’t have to be clamped down to be engraved or cut. Still, some items do need to be held in such a way as to hold it still (cylindrical items) or held in a way the object can be positioned, removed and repositioned in the same exact spot. This is also helpful when engraving multiple items of the same shape so one product can be removed and another inserted in the same exact position. Homemade jigs can be made of almost anything: Silly Putty, sculpting clay, the core of a roll of tape, a fabric bag filled with sand or rice, or custom jigs cut out of a piece of wood or plastic. In the March 2017 issue of EJ, I reported a list of homemade jigs in the article “Laser Tip: Making Your Own Jigs.”
RACK STAR: The Rack Star is a special table/fixture for lasers which is sold by Rowmark distributors. It contains a frame with pointed crossbars to hold objects while they’re being engraved along with an insert that turns it into a cutting grid. It also comes with jigs to hold glassware or a variety of other objects, both flat and odd-shaped. The Rack Star comes in several sizes to fit most lasers and custom jigs are also available.
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. These tables usually have about 1/2" depth with square or hexagonal spaces that range from 1/4" to 3/4". 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 underneath the vector table and out the exhaust. Check with your laser representative for their recommendations. An independent source for these tables is www.cuttinggrid.com.
PROOF TAPE: This is a unique product that when applied to an object, allows you to laser engrave it (the tape) to ensure accurate positioning without actually engraving the object. Available from Quality One Engravers, just apply the tape, laser with low settings and you can see exactly where the engraving will appear.
LASER MARKABLE COATINGS: Although these can be used with all types of lasers, they are most commonly used with CO2 lasers to mark various uncoated metals. Laser markable coatings are available in at least two brand names including CerMark/TherMark and LBT (Laser Bonding Technology). These chemicals can be applied to steel, chrome and a number of other uncoated metals to achieve a black mark on metal the laser would otherwise not mark. The idea with these coatings is once the coated item has been lasered, you can rinse the unlasered coating away using water.
Not all metals mark as well as steel so testing is advisable for marking brass, aluminum, tin, zinc, etc. There are also chemicals available for marking ceramic and glass both in black and colors. CerMark/TherMark can be purchased from Johnson Plastics Plus or JDS Industries, Inc., Sioux Falls, SD, while LBT can be ordered direct at http://www.laserbondingtech.com/order.html or from Marco Awards Group.
DARKENING AGENTS (Fiber Lasers Only): Darkening agents, like those commonly used when rotary engraving brass or aluminum, are also helpful when laser engraving coated brass with a fiber laser. Although the laser will produce dark marks on metal, engravers brass can often be further enhanced by using a darkening agent to make the mark black as opposed to the dark brown made by the laser. Most suppliers like Johnson Plastics Plus offer the chemical.
LACQUER THINNER: This is a highly flammable chemical, but it is the only thing I have found for removing the haze that results when lasering most colored metals (except black), especially colored aluminum. Applying lacquer thinner to coated metal can damage some brands so it must be done quickly. Metal with the color baked on does the best job of resisting chemicals.
MR. CLEAN MAGIC ERASERS: These work great for cleaning laser cut plastics that have smoke damage as well as wood and other materials. Excessive moisture should be avoided when being used on wood.
As you can see, there is a variety of accessories available that can enhance your laser engraving capabilities, allowing you to quickly and easily complete jobs and boost your production. Also, take a look at the sidebar accompanying this article for some suggestions for handy tools for your shop. Chances are you will find a tool, or several tools, that will make your job a lot easier! And be sure to watch for part 2 of this article series which takes a look at accessories for your sublimation and UV printing equipment.