Toasty Warm and Dry

Radiant energy and added air circulation are making infrared drying systems efficient options for many converters.

by Joy English

Today's forecast: sunny and breezy, with highs in the 80s. With weather like this, perfecting a tan is quick and easy. But with this same type of radiant energy, packaged in a different form, a tan is not all that can be accomplished quickly. For the package printing industry, infrared (IR) energy serves many converters' drying needs, especially when combined with convection. Doug Misercola, president of DRI (Port Salerno, Fla.), says, "Basically, infrared is electromagnetic energy that has been around since the beginning of time. The sun is radiant energy. Periodically, manufacturers like myself come up with different ways to focus IR energy, and with unique elements to make it more efficient for today's high speed converting." Using radiant energy with the option of combining it with air, the IR dryer is one energy source that is finding its place in the package printing industry.

Drying process

In package printing, most applications require a drying cycle. Matt Litzler, president of C.A. Litzler (Cleveland), describes this process. "Heat transfer is the application of energy into a product. Mass transfer is the removal of a solvent (or water) … Effective drying needs both heat transfer and mass transfer." Each drying system has its own way of accomplishing this.

Willie Fuchs, president of Fuchs-De Vries, Inc. (Mundelein, Ill.), explains that the IR drying system transfers heat through radiation, rather than by convection. "Convection heat energy raises the temperature of the surrounding air, and then this hot air heats the materials. This dual heating process is less efficient. IR energy passes through the air, similar to light energy flowing from the sun. Only minor energy losses are sustained during its travel."

With so much energy packed into a small space, the IR dryer is one source that is great for preheating. Litzler says, "Infrared is great for putting a tremendous amount of energy into a small space. [It] can be used as a way to increase speeds with preheating."

However, while it is great for directly heating an object, "infrared is an energy source that is not a cure-all for every drying application," says Litzler. "Infrared does a great job of heating the coating and web. Air, [though], is usually required to break the coating boundary layer and help exhaust moisture." By combining infrared with air (convection technology), Litzler says that converters get the best of both worlds.

To combine or not to combine?

Manufacturers today have taken the benefits of IR energy and combined them with air, offering converters a drying system that will not damage their products. Robert Narang, president of Radiant Energy Systems, Inc. (Hawthorne, N.J.), says, "The IR and air combination is a wonderful development, and is very beneficial for drying coatings which are heat sensitive and prone to skinning. The combination works so well because infrared energy heats the water or solvent in the coating very rapidly, and the air provides the scrubbing action to break down the vapor barrier and take the solvent away."

When deciding whether to choose an IR/air combination or simply IR, Misercola says, "Laundry will not dry in a damp basement. As an analogy, remember this statement when considering the importance of air movement relative to heating requirements. Both air movement and heat are just as important for effective drying of water-based inks and coatings." Converters should consider not only their drying requirements and what they expect from their drying system, but also all of the benefits and risks associated with IR drying systems.

Benefits abound

IR drying systems have many benefits, from precise control to high speeds. According to Jim Alimena, vice president of marketing at Glenro, Inc. (Patterson, N.J.), "It's possible to get the right amount of heat exactly where you need it in the drying process. For example, on a wide web, there can be zoning across the width of the web. This facilitates uniform drying, improving product quality." Furthermore, Alimena says that process temperatures can be reached quickly on startups, allowing production to begin immediately, as well as rapid cool down on line stops, preventing residual heat damage to the web.

Other benefits, says Litzler, include higher speeds, less required space, undisturbed product or coatings, energy efficiency, improved quality, reduced noise, and easy and efficient zoning.

Although there are many benefits to choosing an IR drying system, converters need to consider the risks involved, too. By understanding the issues that could arise with an IR dryer, converters can take steps to minimize their impact.

Len Gigantino, vice president of engineering at Glenro, says, "What infrared 'sees' is what it heats, therefore it is easier to overheat the product with infrared than with hot air." However, he offers a solution to this risk. "The ability to closely control infrared with feedback control systems, and the rapid response of the electric infrared heating elements solves this problem nicely."

Alimena recommends converters also keep web orientation in mind when selecting an IR system. "With infrared, it is often possible to reduce the footprint of the dryer by steering the web in a vertical direction, packing lots of heat in only a few feet of machine direction. Vertical orientation is also ideal for drying saturated webs and web coatings on both sides."

For wide web, zoning is also key to ensuring the product is uniformly heated. "Typically, the edge zones run at a slightly higher temperature than the center zone to compensate for edge heat losses. If the product requires uniform drying, the converter should consider having edge and center zones in the dryer," Alimena suggests.

Temperature feedback methods and line stoppage are other issues to consider. The more precise noncontact methods of temperature feedback are more expensive, Alimena points out. He also comments, "If the web stops under heaters emitting intense energy, the product can be damaged and a fire can even start. To avoid these problems, converters need to consider the types of elements they choose for their drying processes." Similarly, Glenro offers rapid-response elements that interlock with controls, turning the heaters off automatically when the line stops, cooling the elements instantly.

Often times, Litzler says, "The downside [to infrared] is when the combination system is misapplied or expectations oversold when one technology dominates a supplier's offering." C.A. Litzler works with converters, providing "unbiased drying recommendations," says Litzler. "Anytime you risk coating blemishes by drying too fast, it would be a bad application for an infrared system."

Converters knowing how they want to use IR determines whether there are downsides, notes Misercola. "There are not really any downsides, if you know what you want to use infrared for. Do you want to heat or do you want to dry? Heating does not necessarily require air, while drying, especially inks and coatings, benefit from added air flow." Once converters know their drying requirements and what they intend to use the IR drying system for, they can select the best option for their needs.

I'll take that one

"The key is to determine what role infrared should play in the overall drying scheme," said Narang. Once converters have decided this, the next thing, according to Misercola, "is to deal with a reputable supplier, someone with years of experience and expertise in the process. Cheaper is not [necessarily] better." Many knowledgeable IR suppliers have lab technicians to help converters craft a system that is well-suited for their drying needs. Most suppliers also custom-manufacture their IR drying systems.

As converters look into their drying needs, Fuchs recommends that converters keep their space allotment and design details and options in mind. Converters, he says, should always consider the cost of the operation (especially, the electrical energy costs).

Litzler also advises, "Infrared is just one part of the drying equation. Research all technologies available, and weigh the strengths and benefits of all to optimize the correct heating technology."

Infrared dryers, especially when combined with air, provide converters with numerous benefits, including increased speeds and improved cost efficiency. Infrared drying systems are also environmentally friendly.

"In fact," Alimena explains, "the radiant heat from an infrared dryer in a converting plant is no more dangerous than standing in front of a fireplace in a house. Moreover, electric infrared is a clean form of heat transfer with the environmental impact limited to the generation of the electric power required for the dryer."

Fuchs agreed, saying that with IR drying systems, no afterburners or air scrubbers are required, as they are with gas ovens or heatset applications. Infrared drying systems, without the need for special inks, eliminate VOCs. There is also no chance of explosion, making the IR drying systems environmentally safe and friendly.

So, while weather forecasters are able to predict the weather outside, converters are now able to predict the temperatures and drying conditions that their IR drying systems will deliver. With conditions like these, everyone will be smiling.