Sheetfed Drying/Curing — A Cure-All for UV Inks

Hot air and infrared (IR) dryers, like their cousin, the UV curing system, play an important role in the print production process, much like a field goal kicker for a football team.

Think about it. When everything is going right, no one pays much attention to the kicker. But in critical situations, a missed field goal or botched extra point quite often results in dire consequences.

Likewise, a sheetfed press’ drying/curing system generally doesn’t garner any attention, unless it doesn’t perform the task at hand. Instead of boos from 50,000 people, the result is screams from one unhappy customer.

“I have always taken the position that a drying or curing system is not just an add-on accessory to the press, but actually an integral part of the press that can and will dictate its ultimate performance,” notes Bill Bonallo, president and CEO of technotrans america. “With sheetfed press running speeds ever increasing—exceeding 18,000 iph—the performance of the drying or curing system is even more critical.”

Drying Dilemmas

There are a number of factors influencing the way hot air and infrared dryers, along with UV curing systems, are manufactured. Bonallo notes several, including system integration into the press, how the addition of a dryer impacts sheet control, and dryer module interchangeability with other components.

Managing heat transfer to both the substrate and press components is another important variable, Bonallo stresses, as water cooling of both dryer and press components (like the delivery sheet guide plates) is generally necessary.

“With infrared and hot air, it is not just the power of the drying system relating to kW output, but how well the energy is transferred to the substrates that also needs to be considered,” he says. “Obviously, the continuous exchange of air in the drying zone is a critical factor in the drying process when a water-based coating is involved. Air flow must be balanced relative to sheet control in the delivery, which clearly can affect the ability to deliver sheets at fully rated press speeds.”

The technotrans america sheetfed division is the exclusive representative for IST Metz UV curing systems for sheetfed applications in the United States and Canada. The company also offers a thermal drying system that doesn’t limit press running speeds and is well balanced with the press delivery to assure optimum drying performance, sheet control and heat management.

IST Metz has introduced several new features and options to its UV curing system offerings. The Cool Cure system allows the UV curing process to take place in an oxygen inert environment. By replacing the oxygen with nitrogen, the efficiency of the UV curing process is increased, resulting in lower required power outputs and significantly reduced temperatures to the substrate.

In UV applications, three factors are of vital importance, according to Bob Sweetman, president of UVDoctors. Two deal with the UV lamps—power and heat management. A third is the ink and coating chemistry, particularly with hybrid ink technology.

“Power and heat management are competing factors,” Sweetman says. “In general, the higher the power level, the greater the need for more sophisticated heat management technology. Faster production speeds on the newer sheetfed presses dictate higher power levels,” he adds. “You need to balance power level with cost—cost increases as the maximum power level of the UV system increases.”

Avoid Drying Damage

Managing heat is critical, according to Sweetman, particularly to avoid heat damage to the sheets and to press components around the lamp. Long print runs result in heated press components, thus altering registration as the components expand. Similarly, elevated pile temperatures can negatively impact substrates. Water cooling and dichroic ‘cold mirror’ reflectors are two prominent heat management technologies.

UVDoctors’ latest offering is a water-cooled shuttered lamp system offering power levels of up to 600 watts per inch. Available reflectors include UV-enhanced aluminum and dichroic ‘cold mirror’ units. Lamps are controlled via an operator touch panel, and an optional mechanical chiller is available for water cooling.

The demand for multicolor work, high-quality printing and faster turnaround time is impacting the design of hot air and IR dryers, according to Margaret Bain, sales and marketing coordinator for Accel Graphic Systems. Drying systems reduce spray powder usage and ink setoff or blocking.

“The compactness of the delivery area in low-pile presses makes IR drying more problematic because of space, excessive heat and premature wearing of parts,” Bain points out. “Many of the safety features found on larger IR units are not available on smaller format presses.”

Positive Alternative

Accel Graphic Systems manufactures the Tempest hot air dryer, which uses PTC (positive temperature coefficient) thermistors instead of IR elements to accelerate the drying process. Heat is generated when an electrical current is applied to the thermistor. Thermistors are self-regulating semiconductors that use a phenomenon called autostabilization to maintain a constant temperature without the need of a thermostat.

This approach to drying eliminates the risk of fire because the thermistors approach, but never reach, the temperature where they could ignite paper. This is combined with warm air to accelerate the drying process. Bain says it is as effective as IR for drying inks (excluding UV) and water-based coatings, and is much safer.

Minimizing press downtime is a serious issue that manufacturers need to address, according to Elinor Midlik, president of Prime UV Systems. “The printer must look for drying and curing systems that offer the latest in computer-controlled platforms that provide superior system control—including on-screen system diagnostics, wiring diagrams and manuals—as well as offsite service capabilities that reduce downtime and lower both operating and maintenance costs,” she says.

Prime UV highest-intensity sheetfed curing systems are guaranteed to increase the speed of all sheetfed presses, adds Midlik. The company features double-cool UV lamps that increase the speed of the curing process while eliminating heat to the substrate. In addition, the new Prime sheetfed inner lamp housing design surrounds the UV bulb chamber on three sides, greatly reducing the radiant energy that is released into surrounding press parts. This, in turn, reduces excessive ambient temperatures under the catwalks—a common cause for troubles with sheetfed presses.

The Prime Smart 2100 control platform assists the press operator by monitoring curing parameters and matching UV output intensity to the speed of the press. Downtime is greatly reduced with Smart 2100 on-screen diagnostics, real-time monitoring of all lamps and a dedicated computer system with I-modem for instant access to the Prime UV service department. High-intensity curing systems are available to cure UV inks interdeck and high-gloss UV coatings in the extended delivery of all sheetfed presses.

Keith Tap, vice president of operations for Grafix USA, underscores the importance of integration with the press, to the extent that the conventional drying or UV curing system doesn’t appear or operate as an add-on accessory.

“Harmonizing the areas of mechanical design for mounting the equipment and electrical interfaces using CAN-bus technology, so the press operator doesn’t face multiple monitors and operating platforms to do his or her job, has to be paramount,” Tap says.

Grafix offers conventional drying (IR and HAK) systems and full or hybrid UV drying systems for all high-pile sheetfed presses. Interdeck and cylinder extension drying systems for hybrid UV and twin coater presses are also available.

It is critical for drying and curing equipment manufacturers to provide gear that exceeds customer expectations while carrying a modest initial cost, notes Jack Karas, vice president of Oxytech Systems. This goes hand-in-hand with a low annual operating cost, and the equipment must also be user-friendly.

“This leads manufacturers to provide the industry with equipment that utilizes cutting-edge technology,” Karas says. “In the case of UV, (this means) high-efficiency digital ballasts, high-output broadband lamp technology, and compact shutterless irradiators combined with self-diagnostics and automated features. In the case of infrared for aqueous, (examples are) high-efficient heated air knives, balanced evacuators, short wave IR and high-energy medium wave IR.”

Oxytech offers short- and high-output medium wave IR combo dryers, short wave IR and medium wave IR dryers. Other options include aqueous drying systems with short wave, medium wave, heated air knives and evacuators. Oxytech’s UV products feature long wave, broadband, 800-watt output and instant on/off technology.

A drying/curing system is critical for printers as they seek to differentiate themselves from their competition, and that system should provide printers the opportunity to create new products and market ideas, according to Gene Van Horn, advertising manager for PRI Technologies.

“Technology isn’t really driving the manufacturing process. It does, however, drive the design process,” Van Horn notes. “Computer technology has come a long way in being able to offer touchscreen capabilities and new ways of monitoring the system while it is in operation. This has made what could be very complex operations as simple as a touch of a button.”

PRI Technologies offers several systems. Its latest, the Zone UV curing system, brings UV capabilities to smaller shops looking to get into the hybrid printing market.

The key feature to this system is the ability to “zone” the UV output so that it is used only where it is needed rather than unnecessarily blanketing an entire sheet. Another product, the ‘cold’ UV curing system, uses a refrigerated water cooling system to keep the lamp housing cool and allow UV inks and coatings to be applied to heat-sensitive substrates.

Infrared Options

For IR applications, PRI offers the Air Blanket infrared drying system. It features touchscreen control and zoned operation and can be used in conjunction with its UV systems. The Quik Dry IR drying system addresses the small- to mid-range litho market and is designed for ink-only applications.

FDV Inc. engineers and manufactures custom-designed drying systems, according to William Fuchs, president. Among the considerations that have impacted the manufacture of these systems are space limitations for installation and new technology that enhances drying/curing output (potentially with greater energy efficiency).

Among the latest offerings from FDV: IR dryers for web and flexo applications, interstation dryers for sheetfed offset, UV curing systems and dryers for glue applicators.

Also available are Baldwin Technology’s GraphiSet IR drying systems. This complete line of IR and hot air drying systems utilize short-wave IR drying modules to dry inks and water-based coatings on presses from low-pile through large-format double coater configurations.

Finally, Adphos-Eltosch North America provides UV interstation solutions for placement after a print unit or over a perfecting unit. Systems feature a compact design and water-cooled shutter/reflector. They are available with dichroic reflectors and stepless power control.

Ketchup or Catsup?

You’ve narrowed the selection down to two or three drying/curing systems that fit your application. But what are the key factors that prompt you to choose one system over another? Our manufacturer panel weighs in on the crucial differentiators to consider before making the purchase.

Bill Bonallo, technotrans america: “Is the person representing the system knowledgeable and experienced? Is the drying/curing system factory approved by the press manufacturer? How many customers have purchased more than one system from the same supplier over a period of time?”

William Fuchs, FDV Inc.: “We highly recommend that your research is completed prior to making a firm commitment or decision. Create a team that consists of your key personnel, and scrutinize and interview possible material suppliers and manufacturers. Now is your opportunity to investigate, not after the equipment is purchased and installed.”

Elinor Midlik, Prime UV: “Speed of cure and system reliability are two factors that should always be considered. A well-designed UV curing system is designed to cure UV inks and UV coatings, but not all UV curing systems are equal and cure at the highest speeds.”

Keith Tap, Grafix USA: “Look at the level of technology. Will the drying/curing system perform at the top rated press speed? Is the system built to last with minimal consumable costs? If these two questions still result in system parity, then we ask customers to consider the important intangibles behind the organization. These include the level of field service, technical phone support, process application support with hands-on demonstration, to name but a few.”

Gene Van Horn, Printing Research: “Take the ‘money’ glasses off. The differences between systems really is more than just the sticker price. Look at all the features, benefits and advantages of each system. You may find a cheaper system, but you may end up regretting that you didn’t take the extra step when the ROI doesn’t pan out.”

Jack Karas, Oxytech Systems: “Things to look for include available power output, annual operating costs, ease of operation, ease of maintenance and availability of field service and parts support.”

Robert Sweetman, UVDoctors: “Cost is certainly a factor, but it should be tempered with an evaluation of how the potential supplier addresses the operating modes of the press. For example, if the press stops, does the lamp go off or is there a shutter mechanism that closes to block the light? A shutterless system is cheaper, but requires several minutes of warmup each time the lamp is started. This can be very frustrating during makeready.”