Airing Out the Options
There is a large selection of air-drying equipment available; which to choose depends greatly on the application.
by Kate Tomlinson, Associate Editor
NO MATTER WHAT you are printing, be it tags and labels, flexible packaging, folding cartons, or corrugated, a dry web is a basic essential. Drying technologies are plentiful, but choosing the right method for your application plays a crucial part in the end product’s success. Unfortunately, air-drying equipment comes with a bit of fine print. And as long as you can answer a couple quick questions (types of inks/coatings/adhesives and typical substrates), suppliers are more than willing to spell out the pros and cons of each type of machinery.
“Simply put, the web-coating process involves applying a diluted solution to the paper, film, or metal substrate and drying the solution,” says Matt Litzler, marketing manager at C.A. Litzler. “Continuous web dryers are used to evaporate the coating from the web’s surface. The evaporation of the coating depends on heat transfer, vapor transfer, and removal of the vaporized diluent.”
Converters producing coated web products are turning to air flotation dryers because of their efficiency, final product quality, and relatively low-cost operation versus roll support dryers.
Litzler explains that the moving coated web in a flotation dryer is supported on a cushion of heated air emitted from a series of airbars above and below the web. Stable flotation is achieved because the positive pressure pad of the nozzles reacts against the vertical components of web tension and weight. “Staggered air bars form a sine wave in the web, which eliminates edge curl while providing web transport without contact,” he concludes.
Bob Narang, presient of Radiant Energy Systems, adds that flotation dryers are good when the web is coated on both sides or with very delicate substrates. He says they are more expensive than other drying technologies but offer advantages including shorter equipment lengths and heights, while boasting the same line speed capabilities as impingement dryers.