Best Practices: Flipping the Switch on LED
Just a few years ago, UV LED curing technology was not a viable solution for most package printers and converters. Though the technology was purported to offer several benefits, including increased uptime, the ability to cure dense colors and substantial energy savings, LED compatible ink had not yet broken onto the scene.
Now that LED ink availability is of minimal concern, more converters are looking into adding this breakthrough curing method. But before switching out traditional UV arc lamps for LED, converters should be aware of exactly what to expect when making the change, and whether LED is right for them.
One of the biggest detractors to traditional UV curing is that the moment an arc lamp is switched on for the first time, its output immediately begins to degrade. LED on the other hand, provides a consistent output over many years of operation.
Similarly, with traditional UV lamps, there is a waiting period for the lamps to reach full strength once they are turned on. LED technology is at full power the second the switch is flipped.
“[LED] doesn’t have a warm-up period,” Sara Jennings, senior technical marketing engineer for Phoseon, says. “An operator, if they’re working with traditional UV, will start up the press in the morning and then go get their coffee while all the arc lamps warm up. There is none of that with an LED system. It is immediately ready to use.”
Because of the instant on and off capabilities of LED lamps, converters installing this technology are seeing substantial energy savings after making the switch, as energy isn’t wasted as UV lamps sit in an idle state.
Steve Metcalf, president and CEO of Air Motion Systems (AMS), explains that instant on and off also creates a time savings for converters.
“Most UV lamps will sit there and idle, and they’ll burn up to 40 to 50% of the power that they would normally consume just waiting for you to restart the machine,” Metcalf says.
“The flip side of that is it’s just faster change time. You can start and stop the process without having to restrike lamps or worry about web breaks. There’s an operational speed savings.”
From a quality standpoint, there are areas where LED shines over traditional UV. One area in particular, Jennings says, is in the curing capabilities LED has for dense black and opaque white areas in a print job.
“For the very dense blacks and opaque whites, including rotary screen first down white, the longer wavelength of the LED system is better at penetrating those colors and provides a better quality of cure,” Jennings says.
Plus, LED curing does not generate heat in the same way traditional UV lamps do, which can be beneficial when running thin substrates.
Metcalf points to an AMS customer that before installing LED, was struggling with thin stocks it was attempting to run under traditional UV.
“They were having so much trouble running those stocks under traditional UV light sources because of the heat built up on the web,” he says. “Despite chill rollers — despite everything you throw at it — it’s really difficult, especially at faster speeds, to produce this without some kind of a problem like registration issues and those sorts of things.”
Once the decision is made to make the LED change, a converter is generally faced with three options. He or she can either completely retrofit an existing press with LED curing, only changeover part of the press to LED or opt for a new LED-outfitted press altogether.
Jennings explains that when a converter opts for a retrofit, the air dryers or traditional UV cassettes can be removed along with the air exhaust manifold and be replaced by the LED light source. The converter will also receive a new user interface touchscreen to be mounted on the press.
If a customer is not ready to commit to a full retrofit, Jennings says Phoseon can install LED in some portions of the press, also leaving the traditional UV system intact to serve as a comfort or failsafe for a converter who is accustomed to that technology.
Similarly, Metcalf says that AMS offers a two-lamp starter package, which can be inserted on the press in a specific area where LED curing could be advantageous.
“[This] is a way we’ve seen quite a few converters start the process with us,” he says. “We’ll typically put those units on a white and on a black, where they’re potentially having the biggest trouble curing.”
While retrofitting either part or the entirety of an existing press can be a good option for some converters, John Crammer, general manager of Best Label, opted to go full speed ahead with a new press outfitted with LED. He explains that he had been eyeing the technology for a few years, but wanted to wait until an ink company came on board with a full set of LED compatible inks.
Crammer says that when Flint Group announced it had 100% of the Pantone colors available in UV LED wavelength curing, bringing the technology into his Union City, Calif., plant was the obvious move. In February, Crammer received installation of a brand new Nilpeter FA-4* flexo press complete with LED curing from GEW.
“The LED technology is very sustainable,” he says. “It really makes its own argument. It’s a no-brainer when you look at LED from the standpoint of cost of operation. The instant on/instant off is huge, and when you take out the fact that you have no movable parts, no shutter mechanisms and no bulbs, that really makes it a cost effective technology that can’t be ignored.”