Surface Buzz
Flexibility—via stretches in compatibility and power—is the most sought-after surface treatment.
by Susan Friedman
How physically fit is surface treating technology? Package printers continue to find out, as suppliers heed the push to achieve higher power, higher treatment levels, and increased configuration flexibility.
Jeff Opad, V.P. of sales and marketing at Pillar Technologies, confirms converters' demand for a flexible corona treating approach—particularly in the form of "convertible" or "universal" systems—solidly outweighs extruders' demand.
Marc Nolan, sales manager at Sherman Treaters, views the convertible unit—one that affords transitioning between a bare roll and a covered roll system—as a practical system for converters having to deal with many variations in their converting process. In systems that include a "true dual dielectric," however, he believes the corona can be weakened because the corona power has to pass through two insulating materials and the web itself.
Nolan encourages package printers to ask questions and obtain specifics. "Hype attached to terms like ‘convertible' and ‘universal' can create confusion, leading customers to believe a treater magically adjusts to whatever is required," he comments.
Augie Ray, Enercon's director of corporate communications, also emphasizes the importance a bit of explanation plays in the consideration of these systems. With Enercon's Universal Roll System, it's made clear to customers they're getting a roll which functions similarly to a bare roll, but also has a non-conductive ceramic coating—not a ceramic covering as a traditional covered roll would, says Ray.
The system's coated roll and covered electrode split the heat load, allowing the roll to run cooler so more power, and hence higher levels of treatment, can be applied. Adjustments aren't needed, Ray explains, because the system is configured ahead of time for the toughest-to-treat substrates on a printer's agenda.
Pillar's Universal corona treater is so named for its ability to run bare roll, covered roll, or dual dielectric by changing electrode magazines—components originally developed to facilitate cleaning. The electrode gap can be set on the fly, and the treater station can be rotated 180 degrees to treat the opposite side of the web.
Opad sees the universality trend carrying over into the realm of power supplies, which are under pressure to match different treater load conditions. Power supplies are also required to operate at the bare minimum and still produce an even corona across the gap, commonly referred to as turn down ratio, he explains. For tougher-to-treat materials requiring higher treatment levels, Opad adds those same power supplies must be capable of delivering maximum output power.
Higher power has set off changes in electrode materials. Opad cites a shift away from aluminum in favor of less corrosive, stainless steel finned electrodes, which provide a smoother, softer corona.
Increased power requirements are a product of faster line speeds—and this requirement combination has grown requests for ceramic dielectrics on covered roll systems, especially on coating and laminating lines, observes Jan Westerheim, president of Solo Systems.
"For small, low-power applications, ceramic isn't so cost-effective," Westerheim states. "But for larger rolls, ceramic requires much less surface energy to handle higher power levels. A 12" ceramic roll would have to be 24" if Hypalon, epoxy, or another standard dielectric was used."
Taking standards further
Converters aren't always eager to rock the boat if they've gotten comfortable with a certain surface treating approach. "Loyalty is one school of thought in surface treating," Westerheim muses. "Some converters like to standardize with repeat orders because their operators already know how to use a certain piece of equipment."
Solo Systems' case in point is its EasyThread corona treater, based on a 25-year-old design featuring a drop-through threading approach and still the company's best-selling model.
That said, converters should stay current on continual improvements in standard treater designs. Take bare roll technology. Almost all new presses are configured with these treaters, says Nolan, because a bare roll unit provides the greatest flexibility for treating a variety of substrates without adjustments or changes.
Improvements in efficiency and design have extended bare roll's already wide spectrum of substrates. One upgrade to consider is Sherman's 3C-MP bare roll treater, which features three ceramic electrodes within the electrode cartridge, increased corona dwell time, and 50 percent more power in a compact, multi-positional design. A convertible electrode allows the unit to be used as a bare roll or a covered roll unit.
In response to the rising complexity of multiple laminations, SOA has expanded the functionality of its corona treating unit to include surface cleaning and static elimination. As the material enters the cleaning head, a high velocity air flow, coupled with a rotating brush system and an air jet nozzle, removes all foreign particles. The second head of the unit contains a high voltage electrode system capable of delivering a maximum power density of 50 watts/sq. m./min. Conductive and non-conductive materials can be treated without adjustment.
Corotec's standard approach to narrow-web corona treating—its self-contained Uni-dyne technology—has become a proving ground for serving the needs of other converting segments.
Most recently, Corotec applied Uni-Dyne technology to its sheet treater product line. "We're seeing sheet treating following narrow web's lead by progressing from paper into more exotic substrates such as polycoated board, PVC, polypropylene, and polyethylene because of demands for a more ‘high-tech' product appearance," says V.P. of Sales Ron Seaman.
"Surface treating is a whole new concept for stack presses from the likes of Heidelberg and Komori which, historically, have never run anything but paper, and are now facing increased use of UV- and water-based inks," he elaborates. Extra vigilance to treatment levels may be necessary, Seaman cautions, because sheet printed items such as milk cartons, if overtreated, won't heat seal.
Generally speaking, Seaman expects narrow-web corona treating features to continue to spill into wide-web; Corotec is already taking their narrow-web cantilever design to 30" with a 5 kilowatt power supply.
Pillar's Universal corona treating system utilizes an interchangeable electrode system available with four separate electrode styles, including stainless sheet shoe, ceramic tube, stainless steel tube or finned.
The TL-MAX II Sided Treater Station introduced by Enercon is available in bare roll, covered roll, and dual dielectric styles for double-sided treatment in 10", 14", 18", and 22" widths.
Sherman's 3C-MP treater includes a convertible electrode, allowing the unit's use as a bare or covered roll treater.
The Uni-Dyne sheet treating system from Corotec combines the power supply with a durable sheet treater and a self-contained drive system for treatment widths up to 48".
