In-line Insights

Flexographic printers lead the charge toward in-line coating and laminating system installations.

By David Luttenberger

Running a press can be a big enough job in itself. Add in-line coating/laminating capabilities, and the classic "if one process is down, the whole line is down" scenario rears its head. Still, a number of package printers have taken on this in-line process's responsibilities with gusto.

Matt Tielkemeier, VP/GM at Dri-Tec, reports that most of his company's in-line coating/laminating units currently in the field are installed behind 6- to 8-color flexo presses printing flexible packaging.

The vast majority of these systems, he elaborates, apply laminating adhesive to the primary substrate, dry it, and then laminate a second barrier material to the primary substrate. However, he reports growing enthusiasm for adding a second pattern coater to the line for in-register application of cold seal adhesive, or in-register printing of game rules or coupons on the inside of packaging such as candy bars, soda bottle labels and hamburger wrappers.

The sudden surge of interest in cold seal can be directly attributed to product purchasing trends. Tom Jacques, marketing strategist for Paper Converting Machine Company (PCMC), cites time-pressed consumers' burgeoning demand for snack bars, granola bars and other individually wrapped foods eaten on-the-go. Cold seal permits temperature-sensitive products like chocolate to be wrapped on packaging machines under low temperatures, preserving the product's structural integrity.

The added benefit of registered cold seal is precise placement of the adhesive for low usage and waste levels, which in turn helps create a crisp-looking package, Jacques adds.

Flexographic presses have led the charge toward in-line installations, primarily because setting up a coating/laminating unit for flexo is easier and cheaper than for a gravure press, and the flexo process offers more flexibility in the face of changeovers. Gravure in-line coating/laminating units are more often dedicated to one job, observes Tielkemeier.

Suppliers collectively confirm that gravure adhesive applicating technology is still employed most often in-line. Hans Deamer, senior vice president at Windmoeller & Hoelscher, says a gravure applicator is the traditional choice for conventional solvent or water-based adhesive lamination, as well as for cold seal emulsions. In-register flexo stations take precedence, he says, for most lacquer coating for UV-cured, water-based or solvent-based lacquers, such as those used on high quality paper bags for pet food.

Multiroll application principles take over for solvent-free lamination, Deamer explains, to apply a relatively thin coating of a 100 percent solids, solvent-free adhesive, which can be either moisture cure or two-part polyurethane chemistry.

Installation line-up

In-line coating/laminating units have taken up residence in a fairly even mix of new and existing press lines. Whether a press is initially ordered with a coating station, or space in the floor layout is left for adding an outboard station in the future, the needs of a specific product most commonly motivate the addition of this capability, says Jacques.

Tielkemeier emphasizes a retrofit will progress most seamlessly on a press that consistently runs smoothly, because the coating/laminating unit's speed and tension will follow those of the press. In some cases, desired specs such as register tolerances have had to be downgraded to compensate for less-than-solid press operations.

In-register coating is achieved with electronic line shafting using encoders built into servo and AC vector drives, Tielkemeier explains. The encoder is mounted inline on the existing (or new) press to follow line speed, and then a dancer is positioned between the press and the coating/laminating unit to fine-tune any discrepancies in velocities or tension. A load cell provides information feedback. "Continued advances in servo motors and drives will increase both speeds and register accuracy," he predicts.

Prior to a venture into in-line coating/laminating, printers will need to gather several sets of specs for suppliers' review. To Deamer, it's essential to know which materials will be run, what the tolerances will be on critical items such as register for print or in-register coatings, what type of adhesives are required for laminations, and what kind of tolerances are expected from the finished product.

Tielkemeier notes substrate information is critical to appropriate web handling arrangements. He stresses that tension is the most important determining factor in the success of a system. With lighter materials that require lighter tensions, standard idler rolls, load cells and web guides may not be effective.

If multiple substrates are planned to be run on the unit, providing an approximate range of tensions required is helpful. If separate web paths are needed for widely ranging, heavy and light substrates, the cost of the installation could rise significantly. "The more a printer can dedicate to a range of tensions the better," he says. "The more you compromise, the more you spend."

In-line or off-line?

In contrast to the heightened activity surrounding in-line's technical development and applications, Deamer paints a flat installation landscape, contending that the ratio of conventional flexo presses to those with in-line coating/laminating capabilities hasn't changed for 20 years.

Of course, printers need to look beyond overall trends and into individual facility and job characteristics to determine in-line's true appeal for their business. "Whether printers should run a product with laminating in-line on a flexo press or out-of-line is really dependent on run lengths," Deamer states, "and, frankly, with a trend towards smaller orders it may make more sense to have separate operations for printing, lamination and coating."

"In the last few years, some brave companies have even installed in-line extrusion lamination systems with flexo presses, but, again, this is really only viable for relatively long run lengths."

Tielkemeier contributes a few more situations where printers may hedge on the in-line decision, such as running an uncommonly expensive substrate, or high turnover of unskilled operators. In addition, he notes, if an in-line coating and laminating unit is already on a press, but printing is done on the line less than fifty percent of the time, an off-line coater/laminator might be the more cost-effective option.

Roll-to-roll could also be preferable if an off-line coater/laminator can achieve faster speeds than the presses at a particular plant. In this case, Tielkemeier says it may be more financially sound to funnel all coating/laminating work through the off-line machine than to add multiple in-line units