None more so than a new method of curing currently being introduced to the UK by Wilmington, Massachusetts firm Energy Sciences Inc. Electron beam curing, or ebeam as it’s more popularly known, is a curing technology that is relatively widely used in the US, but little known here. Energy Sciences’ sales and marketing manager Rick Sanders explains the basic technology.
“Ebeam uses the power of electrons to change an ink, a coating or an adhesive from a liquid to a solid without heat or light,” he says. “I liken it to passing a tray of water through your freezer – the water freezes. Ebeam does exactly the same, except of course the ink doesn’t melt afterwards.”
The process is a little more involved than Sanders’ analogy allows, but nonetheless it’s a simple principle. Electrons are generated by a high voltage applied to a set of tungsten filaments in a vacuum (similar in principle, if not in size, to the average domestic lightbulb). The electrons are propelled out of the vacuum chamber and through a titanium foil to accelerate them. They then strike the sheet or web passing underneath the ebeam unit and initiate a cross-polymerisation process in the ink, coating or adhesive printed on that stock. “The molecular change cures the wet surface instantly,” says Sanders.
Within the flexo sector, ebeam offers printers a means of moving away from solvent-based printing – with its attendant difficulties of storing hazardous chemicals and operator/environmental hazards in terms of emissions – but not in the direction of UV. In this, ebeam may suffer some resistance from its main target user-base, “who are all very switched-on to UV flexo, which is seen as the big thing in that sector,” Sanders admits. One significant step forward for ebeam was achieved two years ago, when the US Food & Drug Administration added the process to its approved list for food packaging. “That did open the door to a lot of interest,” adds Sanders.
Technologically speaking, the ebeam process is similar to UV curing in that it works by triggering a chain reaction that results in the cross-polymerisation of the ink’s molecules; both processes are more or less instant, and therefore allow faster production speeds and greater productivity. But as Sanders points out, ebeam scores heavily over UV in several respects.
Cost-effective
Crucially, too, ebeam costs comparatively little to run. At Drupa, Energy Sciences showed a Comexi 10-colour CI flexo press running its ebeam curing unit, and collected energy draw data from the machine. Analysing the data afterwards, it was found that the ebeam unit cost less than $20 per running hour to operate. “A standard drying oven costs maybe three or four times that,” Sanders says, “and ebeam performs consistently better than UV because there isn’t the same problem with the age of lamps and their declining power output over time. You have to keep reflectors clean on a regular basis to optimise their performance, too, which doesn’t happen with ebeam.” He also points out that the trigger generated by a UV curing system – the process element that kick-starts the cross-polymerisation process – is a photoinitiator, “and that’s relatively unhealthy from an operator’s point of view,” he says.
That said, there are mutterings in the industry about the nitrogen that ebeam units consume – it’s used to optimise the speed of curing by minimising oxygen in the curing area. But nitrogen “rings alarm bells and our competitors love to exaggerate it,” says Sanders. “There is a real misperception here. But most of what we breathe is nitrogen – it’s only 18-20% oxygen. It is an inert gas as far as human beings are concerned.”
The UV process is also inherently wasteful in a way that ebeam is not. Analysis carried out by Energy Sciences recently across a range of UV lamp types showed that on average, of every pound spent paying for energy that powers a UV lamp, around 50-60 pence is spent on what Sanders calls “unusable energy”. Which translates as heat and light generated as by-products of the UV photoinitiator generation. “So only about half to a third of your energy pound is spent on UV bandwidth,” Sanders says. The ebeam process, by contrast, is relatively efficient: all the energy goes into creating electrons, and while the voltage draw is high, it is also highly targeted and therefore more efficient in its use than energy drawn to power UV lamps.
One-process production
But it’s not just about cost savings. Ebeam varnishes, in particular, offer the food packaging print sector some significant benefits. Sanders cites the case of Skittles, the fruit-flavoured sweets made by UK confectioner Mars – until two years ago sold in a bag made up of a printed OPP film that was then overlaminated for strength and scuff resistance and to prevent flavour and odour escape. Now, Skittles are sold in the same printed OPP film that’s surface-printed with an ebeam-cured overprint lacquer. “All the properties that used to be gained from the laminate, have been formulated into the chemistry itself, which means it’s now a one-process production run,” Sanders says, “and another great thing from the manufacturer’s point of view is that an ebeam varnish doesn’t add the same weight as a laminate, so the pack costs less to handle and distribute.”
While at the moment its main success has been in the flexo sector, ebeam has bright prospects in offset too. Drupa was the launchpad for a new ebeam unit for offset, shown at the exhibition attached to a DrentGoebel VSOP narrow web press. Energy Sciences has also produced an ebeam unit for gravure – as yet, it can’t cure inks, but it has been used successfully in US trials for curing coatings.
Like UV, the ebeam curing process calls only for an ebeam unit on the press. Energy Sciences’ units comprise four elements: the electron generator, the accelerator, the high-voltage power supply unit which is either connected by cable or sits on the press if there’s room enough, and an operator’s terminal for controlling the device. Right now, the unit is too big, “and probably too expensive” to attach to a sheetfed press, but Energy Sciences is working on new low-cost versions of its unit to tap into a wider offset market. “The potential for offset is wide,” Sanders remarks. “Right now, the bulk production of web presses shows the quickest return on investment. But there is no technological reason why those benefits shouldn’t extend to commercial sheetfed printers too.”
So if the US is an enthusiastic adopter of ebeam, why not Europe? Sanders thinks it’s down to the fact that, in the US, run lengths are longer and the relatively high cost of the ebeam technology is more easily justified. “It will head downwards in price,” he adds. “As more people get switched on to it, and see its advantages, more units will be produced, and the cost will come down.” Drupa, he says, was “a real European launchpad – we had an enormous amount of interest. We even sold a couple of units straight off the stand to European printers. The age of ebeam,” he states, “is here.”
EBEAM CURING AT DRUPA
At Drupa, Energy Sciences demonstrated the fruits of its five-year partnership with SunChemical – a new flexo ebeam-curing ink system known as WetFlex. The particular glory of WetFlex is that it can print wet on wet, curing once only for all colours when passing underneath a single ebeam curing unit at the end of the press. This avoids the costs and the operating energy draw of UV lamps, which work on an interdeck basis, with a lamp sitting after each unit. The partnership with SunChemical has also produced a system of ebeam-curing varnishes, including varnishes to run on gravure presses. In November last year, Energy Sciences announced its first sale of an ebeam curing unit for a gravure press, to be installed at US company Amgraph Packaging on a Rotomec MW80 gravure press. Italian flexo press manufacturer Comexi ran an EZCure unit on its new 10-colour concept press, the common impression iF2 Icube, where the EZCure worked with SunChemical WetFlex UniQure inks at 70line/cm screen rulings. The first model was sold from the Drupa stand to German packaging printer Schulz. Other flexo presses have already made sales with EB curing units: Fischer & Krecke has sold a CI flexo press, the 16S WetFlex, to another German packaging printer, Uniprint Knauer. On the DrentGoebel stand, Energy Sciences’ EZCure unit was attached to a 33in six-colour VSOP offset narrow web press, and was used to demonstrate printing onto film for wraparound labels, shrink-sleeves and flexible packaging and board for folding cartons.
Read the original article at www.printweek.com.
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