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Past, Present, and Future

The Evolution of UV Flatbed Technology

By Thomas Franklin

When UV flatbed printers first debuted, they weren’t treated to the same media-drenched hype that follows other mainstream technology introductions. However, it’s fair to say the promise of the technology tantalized. The value proposition was simple—save labor costs by printing directly to substrate, eliminating the need to mount and laminate. UV would allow print shops to open new markets by printing on a range of media. It would ease the production environment by reducing—not eliminating—noxious fumes and volatile organic compounds associated with solvent printing. That was the promise, at least. When UV flatbeds trickled out onto the production room floors of print shops, they were characterized by many of the same limitations that bedevil most technologies at launch—lack of efficiency, iffy image quality, onerous maintenance, and steep prices.


Océ North America, an early entrant to the market, initially launched a UV flatbed printer to “bring a more environmentally friendly approach to direct to rigid printing. The company enjoyed modest market success, due to limited productivity and image quality well below the aqueous printers of the same era,” observes Jeff Edwards, international product marketing manager, Océ.


UV did have its share of hype when it was introduced into the market, admits Karla Witte, VP of business development, INX Digital International Co., but it steadily narrowed the gap between its promising potential and real world performance.


“The most common initial limitation was probably gloss matte banding,” remarks Terry Amerine, segment manager, wide format, graphic systems division, Fujifilm North America. “Another limitation of UV printing was that originally matte was the only finishing option.”


“We used to say, ‘we can print on anything’ when UV technology was introduced,” recalls Michael Wozny, strategic marketing manager, EFI. “However, we learned the hard way, that wasn’t quite the case. We now say that UV flatbeds can print to a wide—and still growing—assortment of media.”


Nearly a decade since its introduction, it is safe to say UV flatbed technology has overcome most of its early growing pains. Today, UV flatbeds are available for a fraction of the price they previously commanded, while printing on a greater range of substrates and at speeds that are increasingly attractive alternatives to analog workflows.


The Need for Speed

The most significant advancement in UV flatbed technology is in the realm of production speeds, says Chris Howard, sales and marketing VP, Durst Image Technology US LLC. “The speeds of the first generation technology were about 300 square feet per hour (sf/h) or about six to eight boards an hour. Now, we’re in the many thousands of sf/h or up to 100 boards per hour.”


“While no one ever thinks their printer is fast enough, UV flatbeds have come a long way since their introduction,” seconds Sandy Gramley, portfolio manager, Hewlett-Packard (HP).


Speed boosts are coaxed from every element of the printer design—from the mechanics of media handling to minimizing vibration to ensure accurate drop placements.


“Since our earliest efforts in flatbed UV-curable ink printing we have achieved print speed increases of almost 1,000 percent,” says Edwards. According to vendors, UV flatbeds can and will still get faster.


“These machines will never be speed demons, but they are already fast enough for many,” adds Steve Urmano, marketing manager, Mimaki USA, Inc.


One fertile area for improvement is the attendant workflow. “Depending on your business profile, there could be bottlenecks at different points. HP is trying to reduce those bottlenecks by providing better uptimes for the machine, smoother color management, and better cutter technology,” explains Gramley. “It’s really no longer enough to say, ‘I’m going to make a faster printer,’ you have to look at productivity from end to end.”


Still, some vendors do insist further speed gains can come from a UV flatbed. “There are no technology barriers to increased printing speeds in UV-curable flatbeds as there are with solvent or latex inks, so expect printing speeds to continue to double every two to three years as piezoelectric printhead nozzle density increases and the cost per nozzle decreases,” shares Edwards.


As UV printers continue to make productivity gains, they’ve begun to penetrate analog markets, being adopted by screenprinters. While it’s steadily closing, there’s still a speed gap, which in part explains why digital technology has only converted about 20 percent of the analog industry, adds Wozny. “Screen presses are doing 300 boards an hour. Screenprinters not only want the speed but a low cost per board. It has to be looked at from the standpoint of the total cost of ownership,” he explains.


Ink, Media Advancements

While the technology may have edged past the quantum leap phase of advancements, there is still plenty of research and development being performed. “There are some ink formulations that once you lock down, they become standard without many changes being made to them. When it comes to UV, there is still a lot we can do for a variety of industry segments,” admits Witte. One particular focus is expanding the safety of UV inks in relation to packaging that may come in contact with food or pharmaceuticals.


People often overlook the advancements made in UV ink, but it is just as critical to advancing the range of substrates the technology is capable of tackling. Not to mention the color gamut and reliability of printer performance. “We’re constantly seeking to increase the range of substrates that we print on, doing so at a wider color gamut with greater quality and higher reliability. The ink is a very important part of that,” observes Wozny.


One area with significant improvements is ink flexibility. “You can print on cardboards and do a 180 degree bend and the ink won’t crack. Thermo forming is also now done with UV ink up to a point,” explains Howard.


At the time of UV’s introduction, vendors had a limited amount of raw materials to use in digital inks, observes Larry Hettinger, product marketing manager, graphic inks, Fujifilm. “Now, as the UV market has grown, the range of raw materials is much broader.”


Thank to UV ink’s improvements in adhesion to rigid and flexible substrates, in particular thin vinyl films, UV printer owners are able to tackle market opportunities previously serviced by solvent and eco-solvent systems, says Jennifer Greenquist, inks/warranties business manager, 3M Graphics Market Center.


Packaging is one such application that has much promise, says David Cich, sales and marketing VP, CET Color. “The ability to quickly print to almost all packaging substrates, make corrections, and reproof at a low cost opens up design opportunities that never existed before in the packaging market. The only limitation is with some types of stretchable plastics, which cannot be UV cured and stretched, as the UV light melts the plastic.”

Getting Ahead

It’s impossible to discuss the evolutionary progress of UV flatbeds without touching on printhead developments. From speed to image quality, cost, and reliability, printheads drive much of the advancements in UV performance.


The development of UV-capable printheads was a key factor in the improvement of image quality. “When flatbeds were first introduced, UV-curable inks were limited by the available printheads,” observes Moshe Zach, CEO, Bordeaux Digital PrintInk Ltd. “As a result, large droplet UV-curable ink featured a smaller color gamut and a more matte finished look than comparable prints created with solvent-based inks. The innovation of newer printheads provided the ability to heat the inks. The viscosity could be dialed in to produce smaller droplets, thus improving the overall appearance of the output on rigid substrates.”


Smaller, in the printhead world, is unquestionably better from an image quality standpoint. “Smaller droplet sizes more than any other factor, are the primary driver in the development of this market segment,” explains Edwards. “The decision to incorporate variable-droplet piezoelectric technology enabled direct to rigid printers to market quality that meets or exceeds aqueous printers.”


For many present day UV applications, the quality that contemporary machines have achieved is sufficient, but there’s still room for improvement before the technology can encroach on other platforms, such as litho. “This is an area that UV can’t compete with from a quality standpoint,” admits Howard.


Reliability is another element of printhead advancements driving flatbed technology. “The initial printheads found on flatbeds were not as reliable as they are now,” shares Wozny. Printers needed back-up nozzles for redundancy in the event of failures or to cover up for flaws. When cost per nozzle decreased, it allowed for improved quality and more reliable and accurate printheads.


“There are printheads for UV-curable inks that produce six picoliter ink drops, in conjunction with the ever increasing speed of the equipment,” says Zach.


According to Edwards, inkjet manufacturers in the 1990s adopted six-color printing to substitute lighter colors for darker counterparts in highlights and quarter tones. “This tonal substitution technique was implemented to help overcome visual graininess inherent in fixed dot, large droplet inkjet technology. The added colors helped produce smoother quarter- and mid-tones and smoother, less-grainy gradients,” he explains. While this method eventually became a quasi-standard, it was complicated and expensive.


Variable dot printing, argues Edwards, “renders six-color printing obsolete. The ability to vary the drop size to as little as six picoliters produces sharp images with smoother gradients and quarter tones by placing a small and varying amount of ink at every pixel location without completely filling the space with color. The ability to jet larger droplets up to 42 picoliters enables the printer to saturate the entire pixel space for the production of uniform, solid colors.”


Green Envy

UV technology’s popularity is aided by the increasing push from businesses and print buyers for “greener,” more sustainable solutions. Direct-to-substrate printing eliminates landfill waste, while the UV inks themselves have proven less noxious than their solvent competitors.


“The increased global focus on sustainability and green practices has given UV a substantial boost in acceptance and popularity,” says Greenquist.


A UV printer will never be “office friendly,” jokes Gramley, but it is able to deliver better indoor air quality over solvent. Improvements are still needed in some of the constituent parts of the UV ink system, such as the flushers and cleansers to make them greener, she notes, but research continues.


Wonder What’s Next

According to vendors, UV flatbed technology continues to make gains in speed and image quality, while expanding the range of compatible substrates.


Zach agrees with analysts who predict that UV ink technology will continue to penetrate new printing applications such as flexible packaging, coating technology, electronic fabrication, and trickle into the mass printing segment occupied by offset.


LEDs are increasingly a focus because the heat generated by the UV lamps isn’t just a power drain, it can “make the ink too crispy and warp the media,” says Urmano. He cites this an one area that will evolve in future generations of UV.


For UV flatbeds to evolve, they’ll require reliability and additional speed gains. “Single pass printing is really the Holy Grail of the industry. Whoever delivers that technology would make a quantum leap in print speeds,” shares Howard. Giant leaps aside, UV technology continues to make significant strides.

Jan2011, Digital Output

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