Gary Doman makes the Benny Landa prediction two-thirds of the way through the round table on LED UV printing. “In five years every commercial printer will be running LED UV. In packaging it will be ten years,” he says.
Like Benny Landa’s prediction forecasting the death of offset litho, Doman will be wrong. But about the date, not about the direction the technology is headed. LED UV printing for litho printers offers many, many advantages and few drawbacks. It will become the way that most printers operate.
Currently the take up of the technology is nowhere near this point, although the printers that have made the switch have not turned back to conventional litho printing. It was to understand why, what these barriers are and what the benefits can be that Print Business pulled experts from across the spectrum to a round table.
Present were Nick Sawyer, worldwide product manager for plates from Kodak; Ian Firman, technical sales consultant from VanSon representing the ink manufacturers; Robert Rowe, M Partners sales manager representing RMGT, the most successful LED UV press producer; and Gary Doman, international sales manager of GEW, flying the flag for the LED curing technology.
Light emitting diodes have a long history in print, being used in digital printing and as the laser in platesetters. These operate at the red end of the spectrum. For many years it was impossible to produce diode that produced blue light or UV energy for curing. In 2008 this changed, as Rowe explains.
“We showed it a Drupa on a B3 press. The print looked very flat and the quality was not great. People used the line ‘as good as digital’. And at the time that’s what it was.
“The technology did not take off in the UK because of the recession, while it became a hit in Japan because of the lower power usage. Our first RMGT went in in 2014 and it has been a gradual process since. But as printers need to produce with faster and faster turnaround times, they want instant drying. Now over the last five years 90% of what we build in Japan is fitted with LED for commercial and packaging printers.”
GEW has more than 30 years’ experience in supplying conventional UV curing technology to narrow web flexo printers which have come to adopt LED curing because it does not add heat to the substrate when curing, so can print on thinner and heat sensitive materials. In 2018 GEW saw the opportunity to move LED UV into commercial printing.
Says Doman: “In Japan it has been popular because space is at a premium. There is simply no room for a five-colour plus coater press, so a four-colour press with LED UV has become the standard format and 500-600 machines have been installed with factory fitted LED UV.
“And that doesn’t count for the machines that have been retro fitted. The UK has five-colour machines with coaters because printers have traditionally had to seal the sheet in order to get it through post press.”
The technology has moved on enormously since that initial outing at Drupa. The lamps are more powerful and the systems around them are much better understood. It is possible to retro fit an LED system into pretty well any press, he says, citing the example of an Indian printer that had chosen to convert a 25-year-old Speedmaster 72 to print playing cards on a plastic material.
“Curing distance is not the problem it might have been,” he adds. “Lamp designs are much improved. The more you learn, the better you get.”
Firman works for VanSon, a Dutch ink maker with a proud heritage in offset inks. But the company was simply too small to begin making UV inks. Until last year that is, when T&K Toka, one of the major Japanese ink producers stepped in to acquire the company for its reputation and presence in Europe and the US.
“There has been a major challenge because all ink formulations must change in Europe to meet Eupia requirements,” he says. “We first saw UV being used in Komori’s H-UV presses for special added value applications, say lenticular printing or drip off varnishes. It appealed to printers that wanted to do something different, but there is only a certain amount of this work to go around. Now we are having real conversations with commercial printers.”
According to Sawyer, it is easy to ignore the plate. “A lot of printers just do not ask the question about which is the best plate to use. They believe that their existing plate will work with UV, but this is not always the case.
“In conventional UV, people will bake the plate to make it resilient enough to withstand the harsh UV print environment. Then there was the need for new chemistry and for ozone extraction and the heat build up. All are characteristic of traditional UV.” And these hallmarks do not exist in LED UV.
The traditional UV uses broad spectrum mercury vapour lamps. These generate energy across the UV range and also heat energy. This can be useful as the broad UV both delivers a deep cure and cures on the surface, so is widely used in carton printing.
The alphabet soup of intermediate technologies, H-UV, HR-UV, LE-UV and more, are using a tuned version of the arc lamp which produces a narrower swathe of UV energy. The lamp is a consumable that being analogue will lose effectiveness over time and is always on in use because of the warm up and cool down times needed. The LED by contrast is a digital technology. The upfront cost is higher, but the lamp is only on when needed and energy directed to producing UV on the substrate. Excess energy results in heat in the unit itself and is easily conducted away, not to the substrate.
Kodak set about the R&D to create a process plate for the new technology, initially with a trade off in performance, increased consumption of processing chemistry. The real benefits of the cleaner printing process would come with a process-free plate which has arrived with Sonora X. “We are leading the way with the process-free plate for LED UV,” says Sawyer. It can carry the image for 75,000 impressions without baking according to the spec sheet. Many printers exceed this. “We believe we are conservative with the specifications, one customer regularly achieves double the run length,” he says.
However, Sawyer stresses that in terms of plate and on press chemistry, this is not a drop in technology. Printers need to think in terms of a process or system he explains, which once it is place should not be tinkered with. The operating parameters on LED UV ink water balance are tighter than with conventional printing.
It means too that the plate Kodak delivers has to be produced to much tighter tolerances. “We are having to optimise the graining and coating system with far greater process control. We used to control the temperature of the cleaning baths to within 5ºC and concentrations of the acid within 10,000 litres. Now those are ten times tighter with a temperature fluctuation of 0.2ºC.
“The improvements in quality control has led to lot more stable plate products. We have to ensure there is no variation from batch to batch with process-free plates. We have to control the production environment.” This also lays down a 2 micron coating with the strength to cope with UV inks and founts.
The run length restriction is scarcely a problem for most printers that run LED UV. In commercial printing runs have tumbled and 5,000-15,000 is the average says Doman. “But printers will need to change the rollers, though not their platesetter,” says Sawyer.
RMGT supplies each new press with a combi roller compound and a set of wash, fount and Toyo ink, a combination that the company knows will work. It also has enough customers with different set ups to know what works when advising a new customer. This recalls Komori’s approach when introducing H-UV. The company stressed that the customer was purchasing a system.
Not every supplier is as well versed as Komori, RMGT or those represented around the table. Many printers will prefer to stick with the chemistry supplier they know, who may assure them that they have a suitable fount or blanket wash. But such arrangements are more frequently the cause of problems than the road to success.
In these instances printers will blame the ink, that they have paid a high price for, or the lamps as these are the elements that have changed. “We had one of these complaints,” says Doman. “The printer said the lamps were not working and that he had not changed anything – but then admitted he had put a new batch of ink on.”
The process delivers better quality printing. Rowe says that some customers have found that LED results in a sharper dot, creating some issues in matching back to the original print or balancing print across conventional and LED printing. This means adjusting exposure at the platesetter to compensate he says.
Sawyer agrees: “The operating latitude for UV is tighter, with the need to achieve good distribution of the ink across the plate. It will show up any bad habits that printers have picked up and relied on chemistry or the operating latitude of inks and plates to cover these up. With LED that latitude is not there.”
To some extent greater levels of automation on press are able to take away some of the pressure, rollers dropping into position at the press of a button says Rowe. He adds this does mean that the rollers need to be set correctly and checked, a housekeeping issue for all printers.
The inks remain the most contentious part of the LED transition. These need to be sensitive to the very narrow band of energy that the UV diodes create, requiring specific photoinitiators. The supply of those has been disrupted this year, forcing ink makers to change their recipes. Then there is the cost of the ink in the first place. Without question this is the most widely discussed and possibly least understood aspect of UV printing.
“We always come up against the cost of the ink. But look at its place in the total cost of a job, the press, people, paper, building and so on. Perhaps the smallest factor is the ink. It’s almost insignificant at 3% of the total job cost,” says Doman.
Later the same concern appears when talking about the environmental benefits of LED UV. Can the ink be recycled? It almost does not matter because it amounts to a 2 micron film attached to the substrate.
“This will break down as fast as the substrate it is on,” says Firman. Newer recycling techniques do not have an issue and newer ink formulations will result in an ink that is easier to recycle than a standard litho ink.
In part this is because the ink does not dry through absorption. And this is undoubtedly one of the key benefits of printing with LED UV. “Some people like the washed out and faded look that you get when printing on recycled and uncoated papers which is cased by the ink going into the paper,” says Firman. “Most don’t.”
Rowe agrees, pointing out that what have been problem substrates are no longer causing problems. “Most printers are struggling with tight margins and want to offer added value. We try to educate people about these possibilities, showing them print on foiled papers, for example.
“Printers get hung up on the cost of the ink, but they rarely look at the throughput and the amount of work that is around waiting to go to finishing.”
“If you have eight jobs booked in for one day, you know that eight jobs will go straight to the bindery. Printers can plan their production,” says Firman. “And online printers can offer a same day service,” says Rowe. “If it’s printed by 2pm, it can be delivered by 4pm.”
Doman adds: “We agree that for a company with LED UV, it’s as if they have a very fast digital press. When one customer received the call that ‘we must have a job delivered tomorrow morning’, it always went on the digital press. Now they can print on the LED press for next day delivery and can charge the job as if it is a digital job and get twice the margin. Their digital press is virtually redundant except for a little bit of personalisation print.”
“And we have people who used to run 500-1,000 sheets on the digital press that now print this on the LED. It’s a question of picking the machine that makes you the most money,” says Rowe.
“We have a printer that talked to us about how much higher his ink bill had become, until his partner pointed out ‘We are printing twice the work now’.”
Which approach makes the most return comes down to a range of benefits that move away from simple cost equations into areas of soft as well as hard costs. If the ink costs more, this is set against the absence of spray powder and the lack of aqueous seals. When investing in new, a four-colour press will suffice as there is no need to seal the sheet after printing. “And no printer has ever been able to charge for a coating,” he says.
There is a saving in terms of energy used. Rowe quotes power rates: LED at 10-12kWh, IR alone at 80kWh and IR plus hot air at 160kWh, a considerable saving in the electricity bill. The production benefits extend into finishing. Not only is scheduling improved, there is less marking on the sheet and no spray to find its way into every possible crevice. On the press itself, the lack of powder means there is no need for the delivery to be cleaned out every week or so, creating time that can be used for production.
Sawyer points out that as press manufacturers have pushed the technology to faster speeds and to reduce make ready to the point that a press can be running in just 50 sheets, the job still needs to sit for the same four hours before it can be cut or folded.
“When I am in the US, I can always spot the printer with LED UV because there is no work in progress on the floor,” says Doman. “A printer here can have £10,000-£15,000 tied up in work in progress as jobs are waiting several days to be finished before they can be invoiced. That is cash tied up in the business that affects cashflow.”
Sawyer says that this is something that Kodak makes part of its argument for process-free plates, as this removes the need for processors and baking lines. “We build a value proposition story around the floorspace that is no longer tied up. With less inventory on the floor, you can either reduce the size of building that you need or make better use of the space.
“We had a customer that used to have four plate lines taking up so much space that when he removed them, he was able to sublet the room as an office, providing a new untapped revenue stream.”
A further soft gain, like cleaning out the delivery, is that inks can be left in the duct and on the rollers overnight because they do not dry through oxidation. In contrast there may be a small impact on the life of the rollers, which may need more frequent attention and deglazing.
There are issues that need sorting still. The best known is the tendency of a duct-applied varnish to appear yellow, the result of photo initiators used. This is no longer a problem when using a varnish in a coating unit says Doman, citing experience from North America.
“There is also an issue with special colours which can be difficult and expensive to obtain,” he adds. “Metallic colours are still an issue,” says Firman. VanSon can import these from Japan bypassing the need to have the inks meet Eupia standards which applies to inks manufactured in Europe. The company is working to normalise these inks. Likewise an opaque white is on its way.
Some white ink is already here, Rowe points out, naming a customer in the Netherlands that has become a specialist in plastic printing thanks to the installation of an LED UV press.
Likewise LED UV is definitely here to stay, if not fully mainstream in the UK. The breakthrough has clearly happened in Japan and it has taken place in the US, according to Doman. “In the US, if RMGT sells a press it’s not even a question whether it’s LED. It is simply printing and that is how it will be here in five years.
“One of the biggest changes to offset printing was the arrival of automated plate changing in 1988. Then came CTP. LED is the same effect. In five years this will be fully normalised, some people will choose conventional, most will choose LED. This is a change that is happening now.”
Representatives from lamps (GEW), plates (Kodak), presses (RMGT) and inks (VanSon) convened in the library of St Bride's Institute in the City of London for the LED UV round table.
The discussion was to answer questions such as:
Who is UV printing for?
What do printers need to be aware of?
What are the benefits of UV printing?
Where is its place in the future of print?
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Doman has been head of sales for M Partners and spent 16 years at Manroland GB.
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After the Matthew Boulton School of Printing in Birmingham, Firmin enjoyed a long career in printing before joining VanSon in 2001.
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Rowe previously spent 14 years at Apex Digital Graphics before it was bought by M Partners and before that had nine years at Heidelberg.
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