The pace of development in drying technology since Ryobi first showed that light emitting diodes could cure print at Drupa 2008 has been staggering. In just a decade the diodes have become more powerful, more reliable and more effective at curing inks, coatings and adhesives.
In those early days the choice of diode supplier was limited. Ryobi chose to work with Panasonic and continues to do so as RMGT. Today that choice too has exploded. At the same point that Ryobi was working on LED technology, Komori had worked with a standard mercury vapour lamp to focus the energy output into a narrow, non-ozone producing wave length. As with LED technology this opened the way to instant drying to commercial printers. There would be no need for the extraction equipment that characterises UV print in carton houses.
And across the Atlantic specialist UV lamp supplier AMS spotted the potential in LED. It began to develop LED arrays that could be retro fitted to sheetfed presses to give them a new lease of life, and as in Japan, ensure that printing could satisfy local regulations around the environment.
Today LED is available as a retrofit solution from a number of suppliers and the likes of GEW and IST will enable printers to hedge their bets with the same control cabinets used for conventional and LED technology. Switching from one to the other is a matter of seconds for a label press, and not that much longer for a sheetfed litho press.
All press manufacturers are capable of supplying LED on a press as new. In Japan it is almost mandatory thanks to government legislation restricting energy use. It is popular too in France and Switzerland. If the UK has ordered fewer new presses with LED this is not affecting the interest in retrofitting the technology to existing presses.
Pat Keogh, vice president AMS-Spectral, says: “One of the reasons for the interest in retrofit is that printers are reluctant to invest in new presses because of the uncertainty over Brexit.“Putting LED on an existing press can change your whole customer offer with new products possible at a relatively inexpensive investment compared to buying a new press.”
The ideal machine is one that is five or six years old, well maintained and which in the normal course of events would be due for replacement for the latest, faster and more automated model. “People will have paid off the press and it’s relatively easier for them to extend the finance to cover the LED,” Keogh says.
The oldest press transformed in this way is a 2000 vintage Speedmaster he says. And that is not a one off. The most recent in a machine that is just a year old.
At first the limited power of the diodes meant that the array had to be placed relatively close to the surface of substrate, limiting its application. Nobody wants to the tail of the sheet to flick up and damage the equipment.That is no longer a problem. The effective throw can be as much as 200mm, the diodes are far more efficient, reaching 50% efficiency compared to 15% at the start of development and the design of the optics is much better, enabling the greater throw and able to concentrate the energy on to the ink. For most applications, the press can run at full speed, perhaps slowing for some varnishes.
The LED is a digital technology compared to a hot air or IR system. The LED responds immediately without the warming up period needed for get other systems to get full effectiveness. This means if running different width sheets, the LEDs that are not needed, can be switched off.
The diodes can also be switched off between sheets to save even more energy. An LED system rated at 10kW will replace a conventional system rated at 80kW, Keogh points out. J Thomson Colour recently claimed to have cut power consumption 80% when switching from an older style conventional litho press to a six-colour LED Koenig & Bauer Rapida.
While the LEDs are rated as consumables, they are long lived. Technology developments have increased expected life to 30,000 hours. Baldwin will guarantee 20,000 hours for the AMS Spectral UV units. This will be longer than the expected life of the press, particularly for a retrofit. No problem because the unit can be removed and installed on the next machine with only minimal cost.
“We installed an LED system on a Mitsubishi press in Japan in 2012,” says Keogh. “At the beginning of last year he was buying a new press, but did not order another LED unit to go with it, instead he moved the existing array to the new press.
“Therefore if you are a year or more away from buying a new press, install and get the benefit of using LED now on the existing press and add to the new press when you get it.”
IST UV has been a supplier to Heidelberg among others, though the IST name is not on the latest Heidelberg LED UV system. It too can build on existing experience with UV to offer LED as a retrofit. “Eighty percent of the inquiries we receive are about LED UV,” managing director, sales, Holger Kuehn said the UV Days event last year.
It used the event to show that printers can move from the established technology to the new LED technology without risk as IST can supply both and the printer can make the switch at the right time that suits him. This applies in the main to carton printers that are hanging back from investment while the situation on ink costs and low migration inks remains somewhat uncertain.
The speed of the take up is astonishing. In 2015 just 21.4% of the market was LED UV; by 2021 LED UV will address 52.5% of the market. And this is not by snatching share from the tubed lamp sector: the overall market for UV products is growing. And retrofit is there as a fast growing part of the market.
AMS Spectral UV is equally working as an OEM supplier with new presses, or presses coming over the horizon. At the same time it is working with the diode developers. These exist at the sorts of wavelengths that will offer ink manufacturers different characteristics to exploit as the diodes push into shorter wavelengths that are associated with traditional UV.
However, such diodes are painfully expensive and will last a maximum of 5,000 hours. It is not yet a practical proposition. “But the efficiency will double and the cost will improve,” Keogh says. It is not print that will drive this but the almost limitless market for sterilisation, currently dependent on standard UV lamps. When new diodes become available it will be possible to retrofit these to a retrofit LED array. “We have designed the unit to accommodate new lamps at a later point,” he says.
The retrofit market is a huge opportunity says Duncan Smith, GEW corporate communications manager. “The market is still young and the early adopters have seen the benefits of LED UV for sheetfed offset.” GEW’s first LW2 LED unit for commercial print has been installed at C&D Print in Camden on a Speedmaster 74. “The common belief that UV technology is expensive and in its infancy is being challenged. This perception has limited the use of LED UV in offset to date and many pioneering printers are beginning to invest in retrofit LED UV systems.
GEW has 25 years’ experience in UV technology with experience in the controls, chillers and optics technology as well as the lamps. It also has the experience and contacts to help an installation become a success working with partners in inks and consumables, or else in a junior role if the ink supplier is leading the installation. Smith adds: “For the majority of four-colour process work, LED UV is the perfect solution and the inks are readily available. The high intensity UV-A rays generated by LEDs are also particularly good at penetrating thick ink coats, to give more consistent curing with improved adhesion.
LED systems have proven to be especially effective for the printing of opaque whites and this process has traditionally been a bottleneck in production. LEDs enable a much faster cure because they easily penetrate the ink, with significantly less power, realising a large increase in production capacity.
“The ability to print on uncoated paper is well documented; the sheet is instantly dry, the inks sit on top of the paper giving a lift equivalent to a coated paper and with less ink used, no rub off and less dot gain.”
The future will also see LED UV spread into more areas of print. The first inroads are being made in label printing followed by installations on CI flexo presses for wider width flexo. US supplier Phoseon in June launched a retrofit offer for flexo printing, backed by Phoseon Capital Services to provide financial support for an investment.
The company has supplied UV lamps to hundreds of flexo print units on narrow web presses. The advantage of delivering cool energy at the surface of the substrate could have a huge impact on both the materials printed and on energy consumption. It also means a faster turnaround between jobs as there is no waiting while a conventional lamp warms up to its operating temperature.
The absence of heating in the substrate is key too in commercial web offset. Installations with LED UV rather than a conventional oven exist in Japan. Now there is a first European installation in Zurich. The LED array was installed ahead of the oven and proved so effective that the oven has now been removed says Keogh.
The cost of running the oven, the start up waste and pollution issues have disappeared, along with the technology needed to control the fan out of paper, the humidity levels and so on. Because the humidity level is not as important, each reel can hold more paper, reducing handling and storage requirements.
“And when printing on films this is more important. Because there is no heat, converters can use thinner films which means more material on a reel and fewer reel changes and more products per tonne of polymer.”
There remain questions around some of the food safe aspects of the inks, but if this remains work in progress this is scarcely surprising. It is little more than ten years since LED UV arrived, at the same Drupa that HP launched its inkjet web technology. Inkjet is still developing and testing new applications: no surprise that LED UV is doing the same.
GEW is starting to concentrate on retrofits for commercial sheetfed presses. Its first LW2 LED unit for commercial print has been installed at C&D Print in Camden on a Speedmaster 74.
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LED is available as a retrofit solution from a number of suppliers, enabling printers to hedge their bets with the same control cabinets used for conventional and LED technology. Switching from one to the other is a matter of seconds for a label press, and not that much longer for a sheetfed litho press.
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Pat Keogh, vice president AMS Spectral UV says that investment in a retrofit LED system makes sense when the press has been paid off. “Putting LED on an existing press can change your whole customer offer with new products possible at a relatively inexpensive investment compared to buying a new press," he says.
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