By Noel Ward, Editor@Large
Taking the jackets off your offset presses is the first advantage of adding LED-UV dryers to your press. After that, things get even better, putting an end to conventional drying methods while eliminating environmental concerns associated with old-school UV curing.
Back in the day—and much of that day is still here—drying inks after printing required hot air or heat lamps. Forward-thinking printers who opted for UV inks had to add mercury-arc UV lamps because the UV inks changed the process from drying to curing, a chemical reaction called polymerization, which turned the wet UV inks into a solid. This shortened drying time but the high temperature of the lamps limited the range of substrates that could be used. The lamps also produced ozone, requiring exhaust systems to meet air quality standards. But now LED technology, not unlike that used in the latest crop of flashlights and car headlights, offers a more efficient way to cure UV inks for a wide range of commercial printing.
Consider the typical 4/4 offset press, a fixture in nearly any commercial print shop, that dries printed pages with either hot air or heat lamps. That changes with LED-UV curing. On a simplex press, for example, UV inks are cured instantly when exposed to the bright white-blue light of LED-UV arrays. Work can be cut, stacked or rewound with zero chance of offsetting or rub-off. On a perfecting web press, one side can be printed, instantly cured , then turned and immediately printed and cured on the other side and be ready for immediate use. Have a larger press? No worries: The same process works equally well on 8-color presses.
In contrast, many printers rely on traditional heat drying, which works well but requires protective jackets on the rollers after printing along with high temperature drying units. It is not uncommon for busy shops to have work in process that sits for hours or even days before it can be completed and shipped because of the extended ink drying times required on some substrates. Although heat drying increases energy requirements it is still very effective for areas with high ink coverage and on thicker substrates, such as some packaging applications. Even in packaging, though, LED-UV is increasingly being used in tandem with heat lamps to help lower energy requirements and move jobs through a plant faster.
“Throughput is a huge issue for most printers,” notes Chris Travis, Director of Technology at KBA North America, based in Dallas, Texas. “The KBA VariDry LED-UV curing system allows jobs to seamlessly move from printing directly to post press. That means more work can be done in less time.”
“One of the greatest advantages is the increased range of substrates that can be run when using LED-UV,” says Travis “Because the inks dry almost instantly there’s less penetration into the paper. This, along with the absence of heat, enables printing on heat-sensitive materials such as plastics, as well as on substrates that don’t readily absorb ink, such as highly calendered papers. Having more substrate latitude makes it easier for printers to say ‘yes’ to more jobs which expands their capabilities and provides a competitive advantage. The fast curing inks also tend to increase detail and brightness providing a lift in print quality.”
KBA’s VariDry LED-UV curing units can be retrofitted onto existing presses from KBA or another press maker. “We can retrofit LED-UV curing onto all our KBA Rapida presses from the 75 to the 205 models,” notes Travis.
Whichever press is involved, improved workflow and throughput are the immediate advantages but LED-UV curing adds still more value, he explains. “VariDry LED-UV lamps can last up to ten times longer than traditional UV lamps and require much less energy, so operating costs are lower. And because the lights are just LEDs, heat, ozone and mercury are eliminated, making pressrooms safer for workers and reducing the environmental impact. UV inks are also solvent-free so there is no release of VOCs (volatile organic compounds) that can be expensive to control and manage.”
VariDry LED-UV is a relatively new process, but its adopters are already seeing the advantages. “There are a few limitations with respect to some coatings and areas of heavy ink coverage,” states Travis, “and for now those can be mitigated using conventional heat drying or mercury lamp UV curing. Still, for anyone with a 4/4 press it's a no-brainer. Whether you buy a press from KBA or have the curing units retrofitted, just go to LED-UV curing. And don’t look back.”