SHEETFED DRYING/CURING SYSTEMS -- Running Hot and Cold
BY MARK SMITH
UV rays beating down. Hot air blowing across the skin. Catching some waves. Sounds like a great day at the beach.
In the sheetfed offset printing arena, those descriptions also fit three technology options for boosting quality and speed—UV curing and drying with hot air knives or IR (infrared) energy. Market pressures are dictating that printers implement some form of drying/curing capability, but the "right" choice of technology remains an open question.
"With a multicolor machine plus coater now being the standard for modern sheetfed presses, adequate drying systems have become a must to achieve the highest quality results," notes Bill Whitehead, director of sales, sheetfed products, for Oxy-Dry Corp. in Itasca, IL.
In addition to boosting print quality, drying systems enable the faster turnaround times being demanded by print buyers, notes Margaret Bain, marketing coordinator at Accel Graphic Systems in Dallas. As an added benefit, they reduce spray powder usage and set-off or blocking, she points out.
"The fastest growing drying/curing technology is ultraviolet (UV) systems. UV inks and coatings produce bright, intense colors and extremely high gloss," Bain says.
"Today, with some form of coating specified on almost every job, dryers no longer can be considered an accessory," asserts Bill Bonallo, president of technotrans america in Corona, CA. "They are, in fact, an integral component of the press itself that can and will dictate the overall press performance, particularly in the area of running speed and press up time."
Whitehead sees the use of UV coatings, specifically, as a pivotal decision in the approach to drying/curing taken by a sheetfed printer. Sheets that are run with conventional inks need to dry or be sealed before a UV coating can be applied, which necessitates a separate pass for the coating, he points out. "Using a hybrid or full UV ink system provides the capability to UV coat in-line, while retaining the higher gloss levels and much greater rub resistance offered by the process."
UV coatings lose some gloss when applied over wet inks, agrees Elinor Midlik, president of Prime UV Systems in Carol Stream, IL. When used as recommended, though, she contends that the process offers the highest measurable gloss and resistance to chemicals and abrasion. This enhances consumer appeal for applications such as catalogs, publications and packaging, according to Midlik.
"Another benefit of UV materials is that they dry instantly when exposed to the UV dryer, so finishing can be done in-line or immediately after printing," Midlik continues. "Also, in comparison to IR dryers, UV curing is a cool process so it is recommended for use with plastic substrates of all types."
Building on the benefits already mentioned, Holger Kuehn notes that UV technology is suited to applications requiring heavy ink coverage, high-gloss spot coatings or higher brilliance on uncoated stocks. Kuehn handles sales and support for IST UV-Systems at technotrans america, which assumed responsibility (in the U.S.) for sales and service of the UV equipment for sheetfed applications.
The capability does come at a price. Printing with UV inks requires that a press be dedicated to the process. It also has an impact on the operating environment.
Kuehn counters that hybrid inks are now making it much easier for sheetfed printers to enter the UV market. As the name implies, "hybrid" systems try to bridge the gap between conventional and UV printing. The technology eliminates the need for special rollers and blankets, which means a press doesn't have to be dedicated to UV printing. In addition, the inks can be applied in a wet trapping process, which reduces the number of inter-station/inter-deck UV curing units required—in comparison to a full UV setup.
Traditional UV inks have a problem wet trapping, so inter-deck UV curing is required after each unit to prevent contamination of the cylinders downstream, explains Dave Douglas, vice president of business development at Printing Research (PRI) in Dallas. "Since hybrid inks can be wet trapped, one UV curing station after the final printing unit is able to cure up to four colors in-line before the sheet enters the coater," he adds.
Even with this reduction in curing units, the required investment and operating costs still can be a barrier to adoption of the hybrid UV process. Nonetheless, Douglas says, "Hybrid inks already are being used on practically everything being printed today."
Bonallo, of technotrans america, says he is seeing signs of the quest for high gloss and rub resistance being overtaken by interest in printing on uncoated substrates. "Everyone knows the challenges in printing on uncoated stocks with conventional inks, varnishes and water-based coatings," he points out. "The high absorbency of inks into the stock means detail and color brightness are lost as the sheet dries, and color hue can also be affected. With hybrid or full UV inks, there's far less absorbency into the stock."
The hottest topic for sheetfed printers today is hybrid UV, agrees Vince Kowalski, vice president of technical sales for Grafix LLC in Burr Ridge, IL. "We have more than 75 customers currently hosting this technology, which has taken most into market segments they only dreamed of serving prior to owning this capability."
Nonetheless, it's important for sheetfed printers to consider all of their options, adds Keith Tap, the company's vice president of operations. "We believe one of the biggest considerations printers face today is which drying/curing approach offers the opportunity to provide the best 'value-added' option to their customers," he explains. "When printers study the options available, they should work through a 'crystal ball' equation: What markets do we serve currently? What markets do we have the potential to serve? And what will we be asked to do next week, next month and next year?"
In order have the greatest flexibility moving forward, Grafix recommends installing an interchangeable system of IR/HAK (infrared/hot air knife) drying and hybrid UV curing, according to Tap.
While drying/curing systems and coating options naturally go hand-in-hand with a new sheetfed press purchase, adding capabilities to an existing machine can also make sense, the various manufacturer reps agree.
"One of the most cost-effective investments for a printer is to convert an old one- or two-color sheetfed press into a UV coater," asserts Prime UV Systems' Midlik. "The addition of UV dryers within an existing extended delivery or adding a UV conveyor extension at the end of a sheetfed press will enable the printer to apply UV coatings in-house. This easy UV retrofit can cost as little as 15 percent of the price for a dedicated UV coater."
Retrofitting is becoming very popular with the economy as it is, PRI's Douglas agrees. "Converting an existing press is expensive, but not as expensive as purchasing a new press with a UV system."
Sheetfed printers are not limited to UV technology when adding or upgrading the drying/curing capabilities of existing presses, but they may have to take physical constraints into consideration.
Adding an IR drying system to an older press can increase run speeds and cut turnaround times, thereby increasing the productivity of the press and improving print quality, says Oxy-Dry's Whitehead. "The main advantage to including a drying system as part of a new press installation is that the machine can be configured from the start to accommodate an integrated drying package, with an extended delivery allowing for sufficient dwell time."
Looking at the issue from another angle, William Fuchs—president of Fuchs-DeVries (FDV) in Mundelein, IL—contends that existing drying systems supplied with some sheetfed presses may not be adequate, even for water-based coating applications. "A substantial amount of high-volume hot air is required to set water-based coatings. Unfortunately, the systems supplied on some presses were designed with limited output of high-volume hot air," he asserts.
Inadequate drying capabilities on a sheetfed press can force a printer to reduce production speeds, rack loads to extend drying times and run with too much spray powder, in addition to limiting the type of coatings they can use and lowering the gloss levels they can achieve, Fuchs says. "These printers would clearly benefit by upgrading their existing systems."
Printers can also benefit from the direct line of communication that comes with installing drying/curing capabilities as a press upgrade, adds Midlik. "If a new press is ordered with UV capabilities, the press manufacturer is responsible for installation, startup and warranty of the UV lamp system. When ordered as a retrofit, the UV system manufacturer is responsible for installation, startup and warranty. A retrofit also gives the printer greater flexibility in specifying which UV lamp system it prefers."
Something to Consider
With upgrades—and new installs, for that matter—low-pile presses require special consideration due to the compactness of the delivery area, points out Accel's Bain. Adding IR drying can be more problematic due to the lack of space, excessive heat buildup and premature wearing of parts, she explains. "Also, many of the safety features found on larger IR units are not available on systems for smaller format presses."
Even while touting the benefits of upgrading, the manufacturer reps acknowledge that there are real advantages to specifying a drying/curing system as part of a new press configuration.
There is a huge advantage to having a drying system specified and engineered prior to a press being manufactured, advises FDV's Fuchs. "For example, newer presses allow for extended deliveries, extensions between color units and coater stub units. Press delivery extensions not only accommodate more drying systems, but also allow time for coatings to flow out across the sheet."
The actual installation process is simpler with a new press, points out PRI's Douglas. "All the power pulls and connections for the components can be made at one time," he explains. "Also, the auxiliary equipment can be neatly located around the press."
Tightly integrating the drying/ curing system with a press can do more than improve the appearance, adds Kuehn of technotrans america. "Ordering a new press equipped with a UV preparation from the press manufacturer not only allows for the space to install the system, but ensures that all sensitive components are made resistant to UV energy or protected from it."
With hybrid UV, "multiple UV inter-decks, docking stations and our approach to electrically connect these components via a central switching cabinet are just some of the suggestions we regularly make to avoid a print process roadblock later," offers Kowalski of Grafix.
"Without a doubt, installation on a new press is always the preference," says technotrans america's Bonallo. "The shear amount of square footage the enclosures occupy must be considered up front, along with power, water and air requirements. Oftentimes, UV preparation is not standard on the press and must be provided by the press manufacturer." He says the required modifications can include adding special raised guards between the print units, using special gripper/gripper bar materials in a modified design, and changing the internal wiring and plumbing, etc.
A print shop can reap internal benefits, as well, points out John Crosby, technical manager of ink and drying systems at Baldwin Americas, in Shelton, CT. "Including the drying system in the configuration of a new press means the press operators need only go through one learning curve, as they simultaneously become familiar with the press/dryer package. The drying system may also be more affordable if purchased with the press, since it can be included in the financing package."
That takes care of why and when to buy, which only leaves the decision of what to buy. To that end, the sidebar to this story offers some information about specific drying and UV curing products that can be ordered with a sheetfed offset press or installed as an upgrade.
Bringing an End to Wet Work
Print buyers continue to turn up the heat on sheetfed printers, pushing for ever faster turnaround of jobs while expanding their use of color and coatings. This has put increased emphasis on having an effective solution for drying and/or curing printed sheets. Manufacturers are responding to this challenge with hot-air, IR and UV systems that can be incorporated into new presses or installed as an upgrade.
Printing Research's patented AB ("Air Blanket") infrared drying system is said to feature a unique air management system. Incorporated within the IR drying zone is a combination of high-velocity hot air jets and a high-volume, low-pressure air extraction system. The two components speed drying by evaporating moisture from the sheet, then extracting the moisture-laden air from the drying zone.
PRI's 'Cold' UV curing system is designed to utilize chilled and deionized water to filter out the majority of unwanted heat given off by the UV lamp. The design provides a much cooler cure to the sheet, making it well-suited for use with heat-sensitive substrates.
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Prime UV Systems offers UV curing units with dual, cool-operating lamps. This design is said to increase the speed of the curing process while eliminating the transfer of heat to substrates. Its Prime Smart System 2100 control platform assists the press operator by monitoring curing parameters and adjusting UV intensity output to match the running speed of the press. It includes a dedicated computer system with I-modem to provide instant access to the manufacturer's service department.
The company also has developed a "UV Sheetfed Coater Conversion" for the sheetfed printer. The retrofit package reportedly enables a shop to quickly and easily convert an existing press into a UV coater.
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Oxy-Dry's DuoTek drying systems utilize short- and medium-wave infrared technology in conjunction with heated air knives and evacuation. The integrated, modular design of these elements is said to support effective drying of all ink colors and stock weights. The multiple cassette configuration uses Allen Bradley controls to maximize the efficiency of the system with regard to performance, power consumption and initial cost.
The company's UV/Hybrid curing systems feature super-cooled air and broadband lamp technology, with virtually instant on/off capability eliminating the need for shutters. The technology provides adjustability from 200 to 800 watts per inch per lamp for increased flexibility in system design, as well as an attractive initial capital investment.
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The Graphiset series is a new family of IR drying systems from Baldwin Technology. Depending on the model, their advanced features can include automatic temperature control, operator-friendly touchscreen panels, job memory, self-diagnostics and water-cooled reflector plates that are seamlessly integrated into the press delivery.
GraphiSet GS1 is a patented IR dryer for sheetfed presses with low pile delivery. It incorporates short-wave IR modules and water and/or air-cooling. GraphiSet GS2 is a low energy IR dryer compatible with most 26˝/28˝ presses with high pile delivery. GraphiSet GS4 is designed for sheetfed presses with a high pile delivery and coater. It features automatic temperature control.
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Accel Graphic Systems manufactures the Tempest hot air dryer, which uses PTC thermistors instead of IR elements to accelerate the drying process. Thermistors are self-regulating semiconductors that use a phenomenon called autostabilization to maintain a constant temperature without the need of a thermostat. Heat is generated when an electrical current is applied to the unit.
According to the manufacturer, this approach to drying eliminates the risk of fire because the thermistors approach, but never reach, the temperature at which they could ignite paper. This heating is combined with a flow of warm air to accelerate the drying process. The technology is said to be as effective as IR for drying inks (excluding UV) and water-based coatings.
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Fuchs-DeVries Inc. (FDV) lays claim to several industry firsts, including introducing the first "shortwave" IR dryer for the U.S. market and the first standalone hot air dryer for water-base coatings. The company combines these components with its "Heat/Powder/Ammonia" exhaust systems to create the "Total Drying System" for conventional inks and water-based coatings. All of the components can be independently adjusted by PLC/touchscreen controls.
The company plans to introduce five new products this year, including dryers for DI (digital imaging) presses, new technology and dryers for ink-jet systems, IR drying systems for web presses, an anti-offset air-type powder sprayer, and a coating conditioning system for both water-base and UV coatings.
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Grafix LLC is a supplier of IR/HAK (infrared and hot air knife) drying systems and UV curing solutions to all major sheetfed press manufacturers. The company works closely with the end customer, often via the press manufacturer that OEMs its systems, to make sure the correct drying/curing equipment and flexibility are built into a sheetfed press from the start.
It features an award-winning, hybrid UV process that allows printers to apply high-gloss UV coatings in-line without dedicating a press to only one process. The system eliminates the need for special roller compounds, blankets or fountain solution chemistry, while providing complete cure of inks and coatings to allow for immediate downstream processing or second side printing.
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technotrans america is the exclusive agent for IST UV systems for sheetfed applications in the U.S. and Canada. Tailor-made for a specific printing press, the efficiency of the systems is enhanced by use of cold-mirror reflector technology and stepless control of the lamp power. In addition, the company has brought the web printing technique of UV curing in an inert atmosphere to sheetfed applications.
The manufacturer also offers a new generation of thermal drying systems to boost drying capability at the maximum rated running speeds (16,000 iph) of sheetfed presses. The design allows interchangeability with IST UV components.
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