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Web PrintingFrequently Asked Questions How much light per inch does a UV lamp give off? There is a difference between 0perating power—expressed in watts per inch—and UV energy delivered to the substrate—integrated energy and peak irradiance. Although operating power (watts per inch) and UV energy delivered to the substrate are relational, all systems do not operate at equivalent efficiencies and do not provide equivalent UV energy to the substrate for equivalent input power. Because of the technically effective lamp design, an Aetek 400 W/in UltraPak can actually deliver greater UV energy to the substrate than other 600 W/in systems. Watts per inch is operating power. The Aetek UltraPak system’s operating power is a maximum of 400 W/in (per lamp). The system has three power levels – 200 W, 300 W and 400 W—and the power level used is determined by the speed of the web (i.e., power levels change as web speed increases). UV energy delivered to the substrate is a function of optics, lamp housing and bulb dimension. The Aetek UltraPak System delivers superior UV energy to the web/substrate at any given input power level. The UV energy output is measured in milli-joules per centimeter squared (mJ/cm2) for the integrated energy (or dose) and watts per centimeter squared (W/cm2) for the peak irradiance (or focused power directly under the lamp). Each measure can be broken down into individual bandwidth (UV A, UV B, UV C, and UV V) which is used to confirm a proper bulb-to-chemistry match. Note: the integrated energy is a function of time (i.e. the longer the time exposure the more dose-energy imparted to the substrate) while the irradiance stays the same at all speeds, as it is not time dependant.
No, although all arc lamps that generate UV operate at high temperatures, proper system design includes lamp cooling, via air or water or both, to extract and exhaust the heat away from the press area. This keeps the outer lamp housing from becoming dangerously hot. Aetek’s air-cooled design relies on air flow through the lamp housing to keep the housing from emitting excessive heat. Exhaust air is generally drawn out of the facility, thereby removing the heat. Similarly, the water-cooled design relies on chilled water flow through the lamp housing to remove heat, and the heated water is passed through a closed-loop chiller. Press operators will not be subject to discomfort caused by heat from the lamp housings. Additionally, Aetek has incorporated safety interlocks into the system to prevent heat damage to the substrate should the web stop with the shutters open. In this case, the interface signal from the press will tell the lamp to go to standby power and the shutters to close.
Aetek Arc Lamps are warranted for 1,000 hours of use, and many users attain as much as 2000 hours of useful life. Actual life will depend on power levels used to cure (using only low and medium power levels will extend the life of a lamp); maintenance programs that include regular cleaning of the bulbs and reflectors (if allowed to remain dirty, the power level needed to cure must be increased, which will shorten lamp life); excessive heat in the lamp housing caused by improper airflow (i.e., the blower is not functioning, or the air hoses are damaged or blocked), which will shorten lamp life. Aetek guarantees that the system will deliver the stated integrated energy and peak irradiance as per the normal performance specifications for that lamp at a specified process speed and operating power level. Each application can be tested in our lab in the Chicago area in advance to insure proper cure will result with a sample of your chemistry and substrate and the proper lay-down required for your application. Aetek offers a two-year warrantee for its systems to provide assurance that all components will function as expected.
Current availability for systems are as follows (please check with
Aetek sales for actual system availability):
A UV system can be installed quickly (a matter of hours to a couple of days) if the preparation work is completed when the system and technician arrive on site. Typical installation time (including training and testing) is two to three days total for a standard multi-lamp system.
All Aetek service personnel are dispatched from our facility in Romeoville, Illinois (suburb of Chicago). We offer phone support without charge, and technicians can be dispatched to your site for emergency service. Your salesperson will also help and guide you through any operational problems. They are located in New Jersey, Missouri, California, and Indiana and will be available to you at any time.
No, although there is a heat emitted from the UV system, it is not an effective way to thermally cure inks or coatings. A combination dryer with hot air or IR in addition to the UV lamps is the recommended solution for those applications that require frequent switching from one type of chemistry to another.
That depends somewhat on the type and make of press, but in most cases the new UV inks are much less viscous than in the past, such that they are close to the viscosity of solvent- or water-based inks and require a change in the ink delivery system. On Flexo presses, it is common to change the anilox rolls, but again, with the newer UV inks, that is not always necessary. Additionally, it has been found that the rubber compound on some rolls is not well suited for UV inks and will give short life if not changed to a more durable UV compound rubber. Check with the press manufacturer to get a complete review of recommended changes.
Cured UV inks can be disposed of in the normal waste stream, as they are not considered to be hazardous waste. Uncured ink must be disposed of per the manufacturer’s recommendations and state or local ordinances regarding the chemical components of the ink.
Although UV inks are about twice the cost of solvent- or water-based inks, they provide more useable coverage, as they are 100% solids—that is, they require less ink to attain the same color density as a thermal-cured ink because a portion of the thermal-cured ink evaporates. Additionally, UV inks do not dry in the ink train and therefore do not require daily wash ups, and most printers are able to run at faster speeds using UV inks. The net result is that when the labor to perform wash-ups, startup time and production are factored in along with the ink usage, UV inks are actually less costly to a printing operation than solvent- or water-based inks.
The the bulb and reflector liners require regular maintenance to keep them clean, with the service interval depending on the process. Bulbs and reflector liners should be cleaned with alcohol and clean paper towels. Other maintenance items include mercury relays, pneumatic valves, filters and limit switches on a very infrequent interval.
It is hard to know for sure how many existing presses are equipped with UV. Many of the presses prior to approximately 1996 were not well arranged to accept UV. However, since 1996, most press manufactures have included a UV consideration in the design of their newer equipment. Depending on the manufacturer (some are targeted for markets that have adopted more UV usage than others), UV lamps are equipped on at least one location (usually end of station for curing of varnishes or other coatings) on over 60% of the new in-line flexo presses sold. Additionally, UV lamps are equipped in all print stations on over 30% of all new in-line flexo presses sold. The number of presses equipped with UV continues to grow each year. Note: in Europe, where more than 85% of new in-line presses sold have full UV—for performance as well as environmental advantages—the use of UV has grown faster than in the U.S. How do you know if the cure is complete? There are two common tests for completeness of cure or the polymerization process. They are a tape test to determine adhesion of the ink or coating to the substrate and a scratch test to determine that the cure is full depth. Additionally, many UV chemistries continue to cure after exposure to UV lamps—this is known as a post cure. Post cure takes place off-press and further enhances the physical properties of the ink or coating in terms of toughness and adhesion. That depends on the thickness or lay-down of the ink or coating, as well as the press speed. If thickness or press speed increases the UV power may also need to increase. This can only be determined on-press and should include sampling as per the tape and scratch tests for full cure described above. The UV process enables the press to deliver higher-quality work—better color density with very little dot gain (as low as 3%) at faster press speeds. Additionally, startup is faster and clean-up is less time-consuming, so labor is reduced. Finally, the cost of UV chemistry on a coverage basis is less expensive than with solvent- or water-based inks and coatings, and the UV curing process consumes less electrical energy than that of hot air of IR ovens to effect drying. Please see the papers “Why Use UV,” and “Quality Improvements Through the UV Curing Process” in the Tech Sheets section of the web site.
No. In fact, just the opposite. New UV systems have become even more energy-efficient and so have increased the savings of operating a UV system rather than a hot-air or IR dryer. Please see the paper “Why Use UV” in the Tech Sheets section of the web site.
This is a stigma from the past. The post-cure odor of the past was associated with the photo-initiator used to effect the polymerization of the monomers and oligimers in the UV chemistry. Current photo-initiators used in UV chemistries have little to no post-cure odor. Again, the post-cure odor is history and no longer present with newer photo-initiators.
Aetek has radiometry data for each of its lamp families—UV Pak, UltraPak and UVXL—which, while treated as confidential, is shared with prospects as a specific application is being discussed to determine the quantity of lamps needed to attain full curing of the ink or coating at the press speeds anticipated. Please contact the Aetek sales group for that review.
Absolutely. Aetek has had a number of means to abate the heat emitted to the substrate from the UV lamp and continues to advance that technology. With the UltraPak, a combination of dichroic shutters and a dichroic quartz filter allows use of filmic materials down to about 2 mil without the need for chill rolls. Aetek would be pleased to assist a prospect in running a sample of the intended film via use of demo equipment that can be fitted to the prospects’ press. Contact the Aetek sales group to arrange a demo.
Yes, adjustment can be made via the press controls or by resetting the set points in the Aetek supplied speed-ramping pickup device.
It is advisable to maintain tension control of the web so as to prevent web lift within the lamp structure when web motion resumes.
Aetek works and partners with a number of ink and coating suppliers to assist prospects with their curing needs. While no single ink or coating supplier is recommended, Aetek will work with any supplier a prospect may choose. If the application is having difficulty, Aetek will make suggestions for an alternate supplier based on experience.
No, UV chemistries require only UV to attain full cure. The use of hot air along with the UV can cause excessive heat at the substrate which will in most cases be detrimental.
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