By Patrick Henry, WhatTheyThink
As every printer knows, a skid of still-wet sheets on the pressroom floor is a pile of paper that can’t turn into a stack of profit until the job is dry enough to be trimmed, folded, finished and shipped to the customer. That can take time – and time when nothing other than drying is happening is the opposite of productive in a busy offset plant. Hence, the appeal of instant drying by curing specially formulated inks and coatings with ultraviolet (UV) radiation. There are two ways to do it: with traditional mercury-vapor UV lamps and with exposure units that use light-emitting diodes (LEDs) as the radiation source.
There also are two ways for offset printers to add the capability: by buying a new press fully equipped for UV at the factory or by retrofitting an existing press with either a traditional UV or a UV LED system. This report examines the retrofitting option, starting with an overview of what vendors of UV technologies are hearing from their customers as they ponder stepping into the invisible spotlight of ultraviolet curing.
Errol Moebius, president/CEO, IST America Corporation, believes customers should begin by defining how they intend to apply UV curing now and in the future. This includes working with their consumables suppliers and their designers to determine what will and will not work. For example, says Moebius, “Does it work with that substrate? Is UV really necessary on that product? How suitable is UV for food migration? They have to understand what their applications are. They have to be clear on the differences between traditional UV and UV LED. We all need a little bit more education.”
Live Long And Prosper
According to Moebius, what most customers typically want to know about UV LED is how much money and energy it will save them compared with the older, lamp-based process. The operating life of a UV LED system – up to 10 times that of a 2,500-hour traditional UV unit – is another point of comparison in its favor. ROI, safety and manufacturer support also loom large in customers’ thinking.
Moebius says that owing to health and safety regulations governing the uses of traditional UV, the process “has significantly improved over the years. It’s not the bad ogre it used to be,” in terms of reputation. “People have obviously got more comfortable with it.”
“Conventional UV is a very mature approach and arguably, so is LED,” observes Gary Doman, international sales manager, Sheet-fed, GEW. He sees two trends of adoption running in parallel. He says that one is a migration from traditional UV to UV LED among packaging producers. The other, occurring in the commercial market, is a growing uptake of UV LED by printers with no previous use of traditional curing.
The main reason for the shift to UV LED in packaging is the savings in energy, according to Doman. “If you go from a traditional UV system to an all UV LEDsystem, your energy savings are going to be about 70%,” he says. “So, if you’re spending $100,000 a month on electricity, you’re going to cut that to $30,000.” These are actual savings that GEW has documented by measuring the electrical consumption of its UV LED systems over time, Doman adds.
As Doman sees it, adoption in the commercial market is being driven in part by printers’ desire to make their offset presses more efficient for the kinds of small-format, short-run work they have largely shifted to their digital equipment. The key to achieving this, he explains, lies in the instant drying that UV LED makes possible.
Keeping Up with Digital
He says that when customers ask themselves how they can match the throughput speed of digital printing, they find the answer is that sheets cured on a conventional offset press can go straight to the postpress department for finishing and delivery. This often leads them to conclude that it’s cheaper overall to put small runs on the offset press as long as that press is equipped for UV LED. Another driver of adoption among commercial printers is their movement into packaging, with some plants transitioning completely. These printers, says Doman, “have really cut their teeth on UV LED because it is a really simple and cost-effective way to get UV.”
Stacy Hoge, Phoseon marketing manager, Excelitas Technologies, says that because offset printing presses have used mercury arc UV curing for many years, there are fewer gaps in printers’ knowledge about it than is the case with UV LED, a newer technology. One of the knowledge gaps for UV LED has to do with its capability. As Hoge explains, “Users commonly think that UV LED systems are not powerful enough to support offset applications, but these systems now have the high intensity needed to deliver the required production speeds for both sheet-fed and web offset printing.”
She says that other questions on prospective adopters’ minds include deciding whether to retrofit an existing press with UV or to buy a UV-equipped new one, determining total investment cost and ROI, and understanding the sustainability benefits of integrating UV.
Why Traditional Stays That Way
Like others serving the UV printing market, these vendors offer both traditional lamp-based and UV LED-curing solutions. UV LED is a newer technology than traditional UV, but it isn’t being positioned as a replacement for the older process. The vendors agree that in some offset printing applications, traditional UV remains the preferred approach as UV LED finds opportunities of its own.
Moebius notes that while much progress has been made in UV LED, the technology has limitations that aren’t always recognized. He says these factors could make it less desirable than traditional UV for jobs requiring complex ink sequences, heavy coverage, robust scuff and scratch resistance, and special effects. He explains that because the traditional process cures with stronger ink adhesion in a wider range of the UV spectrum than UV LED, it’s suitable for a correspondingly wider mix of substrates. These include non-paper materials such as foil board, synthetics and plastics, often employed in high-end packaging for cosmetics and liquor.
Doman says that for packaging and other types of work with more than four colors plus coating and varnishing, it’s possible to hybridize the curing with interdeck UV LED units and traditional UV lamps in the extended delivery after the coater, sometimes next to an IR system for drying conventional coatings. That way, he explains, the varnishing step can be done with traditional UV fluids that are less expensive and available in more varieties than their LED counterparts.
Doman also notes a lingering but now outmoded perception that UV LED varnishes tend to yellow after they’re applied. He says this would be an issue only in very specific types of packaging – for instance, pharmaceutical boxes in which the white board “has got to be perfectly white.”
Hoge sees traditional UV as the preferred option for low-cost, short-lifecycle commercial printed matter that can be sent directly to postpress as fully dried sheets.
Where UV LED Excels
Moebius says that the demand for UV LED is strongest in four-color commercial work on paper substrates with limited use of matched colors. He notes that in this type of production, post-cure adhesion is supported by the absorption of ink into the substrate. Demand also is picking up in narrow-web work on non-paper substrates without heavy ink coverage and overloading of color by trapping.
UV LED is a must for printing on plastics that could be distorted by the heat of exposure to traditional UV, according to Doman. “UV LED runs much, much cooler” than the lamp-based process. “For commercial printers who want to print plastic, there really is only one way, and that’s UV LED, the ability to cure those special inks through the machine,” he says.
As for adhesion, Doman agrees that there are certain applications on specific materials where traditional UV will be preferable. But in others, UV LED has the edge: for example, when printing white on clear plastic. He explains that because the titanium dioxide pigment in white ink reflects UV radiation, curing with the traditional process would require installing a special lamp to raise the peak wavelength of the UV output. Operating naturally at the high end of the exposure range, UV LED has a distinct advantage for this type of work.
According to Hoge, demand for UV LED curing is growing fastest in web-to-print commercial printing applications and in labels and packaging. This especially is true for heat-sensitive or special materials such as PET (polyethylene terephthalate) and PP (polypropylene), as well as foil.
Moebius says that because UV LED units cure without the heat of traditional lamps, they’re appropriate for synthetics and other heat-sensitive substrates. Eliminating the buildup of heat also reduces general wear and tear on the equipment. Unlike lamps, emitters inside UV LED units can be switched on and off selectively to support different curing formats. The long-life expectancy of UV LED units represents a significant cost savings for commercial offset printers, Moebius adds.
Spray Powder Begone
Doman points out that because UV LED units don’t require the cooling and ozone extraction of traditional UV, they are much simpler to install. By doing away with the need for offset spray powder, they also eliminate the risk of spray powder contamination and the cleanup chores that come with it.
What sometimes isn’t fully appreciated, according to Doman, is the role that UV LED plays in reducing the frequency of reprints. Too often, he says, a job that has been printed and finished with care will be rejected by the customer because of incomplete drying, the appearance of scuff marks or traces of spray powder in the print. Printers that have spent hundreds of thousands of dollars on reprints can make that unwanted expense disappear by switching to instant-drying, damage-resistant UV LED curing, Doman advises.
Hoge says that among the list of attractions for UV LED curing are printing with sharper dots and more vibrant colors for a higher-quality finished product; solvent-free inks and coatings without the environmental impact of solvent-based consumables; the ability to print on nearly all types of substrates, including non-absorbent materials such as plastics; and eliminating concerns about mercury, which UV LED emitters do not use.
Fair Comparison
A question that usually occurs to prospective adopters is whether a legacy press retrofitted for UV will be as efficient in terms of curing as a new press with the UV technology built in. According to Moebius, there’s no meaningful difference in performance between a retrofitted UV unit and a system built into the press from day one. “The legacy machine would get a new system on it, and the system would output the UV rays at the same amount” as a comparable unit running organically on a newer press, he says.
Any difference would lie in the integration capabilities and the overall productivity of the legacy machine to which UV is added, Moebius explains. Its running speed, the consumables and solvents that it uses, as well as its heat, air and exhaust management systems all play into how productive the legacy press would be compared with a newer one. But from a UV-curing standpoint, “absolutely they should be the same,” Moebius says.
“Many of our systems go onto quite old machines,” with good results, says Doman, noting that a customer that invests in a UV retrofit instead of a whole new UV press “gets a machine that does everything a brand new press can do,” in terms of curing. Doman acknowledges that while the speed of output might not be as high, “the benefits are the same. There’s no difference. If I put UV on a 10-year-old machine and I want to diversify my products, it will just get more efficient.”
If a press is retrofitted correctly and the UV-curing process has been successfully defined, the legacy press should operate as efficiently as a new press,” Hoge states. “However, newer presses may offer faster press speeds and other advanced features than the older press for higher productivity.”
Roadmap for Retrofitting
Moebius says that adding UV to an existing press would involve changing to UV-compatible consumables and replacing some of the machine components they come into contact with – for example, rubber offset blankets and the diaphragms inside the washup trays. If the installation is traditional UV, safety modifications on catwalks and side frames would be in order. Retrofitting a press with traditional UV can be “a little more complicated” than adding UV LED because of the heat-management considerations of the lamp-based process, Moebius notes. With low-heat UV LED, “you have a cassette that, as long as it’s the right height, you bolt it in place and move on.” A mercury-bulb UV system, on the other hand, needs not only correct placement but also airflow, water cooling and shielding to make it safe to operate.
Doman says that because new presses are built to be UV-ready, retrofitting them with traditional UV or UV LED systems is relatively easy. For customers with older equipment, GEW starts the process by taking 3D measurements of the press for designing the lamps, shielding, fittings and other components that will be needed for integration. Then, at the customer’s site, “it’s really a case of just bolting the lamp into the machine, hooking up the power supply and off they run.” For most customers, “within two and a half days, they’ll be back in production.”
Integration Was ‘Beautiful’
Doman adds that GEW recently installed UV on a ‘beautiful’ manroland 800 sheet-fed press that has been in service for 50 years. “The integration was no problem at all. I would say that if you could do that machine, you could do anything,” he observes.
Hoge reminds prospective adopters that adding UV to a press means paying attention to more than just the UV components. “Retrofitting requires working closely with the printer OEM, ink company and UV supplier,” she advises. “The initial challenge with UV is getting the inks and chemicals right. The inks and coatings need to cure at the correct wavelength for the technology. Regardless of whether traditional UV or LED is used, the ink and coating chemistries are ultraviolet-based and need to be compatible with the light source.”
Reprinted with permission from WhatTheyThink (www.whattheythink.com).
