When Single Pass Took Flight
Though it has become the talk of the industry only fairly recently, single-pass inkjet printing goes back 20 years to a system that demonstrated the enormous potential of the technology.
In our special Innovation Issue, we present a collection of expert essays on an important technology in the industry today. Here, we take explore the development of single-pass inkjet.
You can sum up the pioneer era of inkjet with a twist on a cliché: (lack of) speed kills. The earliest inkjet units marketed for graphic-arts applications in the early ’90s weren’t really industrial machinery at all, accomplishing in an hour what could be done in seconds on a conventional press. Even accounting for prepress and setup savings, only the shortest run lengths could justifiably be done. And the biggest disconnect for potential buyers: the printhead carriages that traversed back and forth across the substrate, one painstaking row at a time, instead of imaging the full width of the sheet at once as analog presses did.
Continuous inkjet technology was already being used for single-pass coding and marking, but its potential for graphic-arts applications was minimal. By ’96, hints of parallel drop-on-demand piezo inkjet technology began to appear with new machine configurations that used full-width arrays instead of traversing printheads. First came the Idanit-162 Ad, with an unusual drum-based design that could image 5 x 8-foot sheets of vinyl and other flexible stocks for applications such as fleet markings. That same year, Tektronix unveiled the Phaser 600, a 48-inch rollfed printer designed for promotional graphics that used solid wax inks.
But the breakthrough of a true full-color, single-pass print engine using drop-on-demand heads was still four years away. And it would come from a familiar name that was not yet associated with printer manufacturing.
A Wrench in the System
The Belgian company Barco Graphics was known for its high-quality film imagesetters as well software and other prepress solutions. In the early ’90s, Barco developed a digital front end called PrintStreamer for electrostatic print engines, which then had more market traction in specialty printing than inkjet and other digital technologies.
“I saw the potential of PrintStreamer, but also the shortcomings of dry-toner digital printing for the markets we were serving,” says Rob Haak, who managed Barco’s digital printing division. “We started to study piezo drop-on-demand technology, and decided to move forward with plans to build a single-pass, full-color inkjet system using UV inks for the markets we knew and had already served. We knew how to feed and master the data streams for full-speed digital presses, so it was a logical step for us.”
In April of ’98, Haak approved plans to develop a single-pass, roll-to-roll system tentatively named Ramses that could be adapted for a variety of industrial applications. Among the key partners brought in for the project were Metronic, a German manufacturer of roll-to-roll systems for flexo printing that built the substrate transport system, and the UK firm Cambridge Consultants, which worked on the printhead array (known as the Single Pass Inkjet Color Engine, or SPICE). Barco, in addition to integrating the project, developed the front end technology including the RIP.
The touch-screen control panel was designed with a simple user interface.
Ambitiously, the partners set out to unveil their new single-pass technology at drupa 2000, then only 25 months away. “The schedule was quite compressed,” remembers Will Eve, who worked for Cambridge Consultants then and led the project. (He’s now director of technology for Inca Digital Printers.) “It was all quite new. We could see that it should be possible to put together wide systems using multiple printheads, and we knew that drop on demand was much simpler than continuous inkjet. What, as they say, could possibly go wrong?”
Well, a lot of things. The team would soon encounter the formidable hurdles to single-pass printing that continue to challenge inkjet developers to this day, not least of which is banding. It turned out that drop-on-demand machines used traversing heads for a reason: Without the redundancy of those overlapping passes, defects from clogged nozzles or printheads that weren’t uniform or in perfect alignment with one another were glaringly apparent. Other challenges included keeping the ink stable at such rapid deposition speeds and understanding the drop-on-drop interactions after jetting.
“I think we were all quite naïve and had expectations of how it was all going to come together quickly. We wildly underestimated how hard it would be. And that’s just as well,” Eve says, laughing, “because we never would have started if we had known.”
Then, just weeks before the show, the team learned that the printheads it had planned to use in the system would not be available in time. “The drupa timeline was under severe pressure, so we decided to combine two Xaar 500 binary heads together in one cartridge,” Haak explains. “After initial testing with one color, we moved on to a CMYK version that was narrower than we had planned because we wanted to be ready for the drupa 2000 technology demonstration.”
Eve remembers preparations going literally down to the wire. “The machines were delivered to drupa without the printheads – and that wasn’t a precaution of any kind. It was because we didn’t have the printheads,” he says. “We only got delivery of the printheads during the [setup] of the show, so that was fairly panicky. When they finally did arrive, we put them in and got things working. It was miraculous, really.”
Just under the wire, the.factory was demonstrated at drupa 2000 with a commercial launch two years later.
The printer, renamed the Dot Factory (quirkily spelled “the.factory”), was one of the most talked-about technologies at the show, even though the demonstration fell short of Haak’s expectations. The speed and width were just fractions of what he had hoped. “Finally, we were jetting UV inks on different industrial substrates in a single pass, but the speed was limited. Due to inkflow issues, we could only run between 5 to 10 meters a minute at 14 centimeters wide.”
Take Heed of the Times
With the positive reception at drupa behind them, the team set out to refine the.factory in preparation for a formal product launch at IPEX 2002. The printer would be offered in four- and six-color versions in widths up to 24.8 inches and with a maximum print speed of 79 linear feet per minute, or about 10,000 square feet per hour – a speed unheard of at that time. It used 300-dpi, eight-level grayscale printheads from Toshiba. The transport system featured a web-tension roller designed to accommodate a range of substrate thicknesses; the nitrogen UV curing system enhanced adhesion to plastics to address a greater range of applications. Underscoring this versatility, the first beta placement was at the Belgian company Chiyoda, a manufacturer of laminated flooring and other décor products that planned to use the.factory for proofs, samples, and short-run customized work. In late 2001, Barco decided to spin off the digital printing division as a separate company called Dotrix, with Haak as the president and CEO.
Following IPEX, Haak remembers a steady stream of potential buyers coming to the Dotrix facility to test the machine for a wide range of applications – laminates, sports equipment, packaging, folding cartons, plastic tubes, and more. “Our demo unit was running day and night to accommodate the specific jobs, on all kind of materials,” he says. “We were really being evangelists for inkjet, as we had to prove the short-run printing advantages and break-even point with different conventional printing technologies (screen, flexo, gravure, and offset), over and over again. And imagine: We were talking about UV inks that were priced at 150 euros per liter!”
Two more field units were placed at display graphics facilities, including the first North American installation at RockTenn Merchandising Displays (now WestRock), which used the.factory to print P-O-P displays and cash wraps. Tom Cooper, R&D manager of digital printing for WestRock, faced similar obstacles as Barco in conveying the benefits of the new technology to customers. He remembers one cosmetics company in particular where the buyer felt that the high gloss of the UV ink cheapened the brand’s image. “The next thing you knew, all these other people around the table were nodding and saying, ‘Oh, yes, I agree – it does cheapen our image.’
“Later, we did a demonstration with that same group of people. We showed them two displays. One was offset and the other was from the Dotrix. We said, ‘You tell us which one is offset and which one is Dotrix.’ And they all thought the Dotrix was the offset print.”
Momentum appeared to be building. The company announced an OEM relationship with flexo press manufacturer Mark Andy and placed additional units in more typical commercial applications. Meanwhile, as Haak notes, the buzz about single-pass printing was beginning to spread beyond Dotrix. The Spanish companies Cretaprint (purchased by EFI in 2012) and Kerajet were using single-pass print engines to decorate ceramic tiles. Other technology developers including Aprion Digital and Memjet began making announcements leading up to drupa 2004.
High-capacity ink reservoirs allowed for continuous operation.
Then, shortly before the show, Agfa purchased Dotrix from Barco for a reported 6 million euros. “We felt we had overcome the difficult integration issues for several markets and were sure to take advantage of the power of Agfa’s worldwide distribution,” says Haak, who left to form an inkjet consultancy the following year. “However, Dotrix ended up in ‘parking’ mode and lost valuable time to market.” Among other revisions, Agfa changed the printheads and inks, and in 2009 launched a redesigned version called the Dotrix Modular, ultimately discontinuing the brand in 2012.
The Future is Now
In hindsight, it’s striking how far ahead of its time the Dotrix was. There would be other stepping stones in the slow progression of single-pass technology. Inca, for example, pursued the corrugated board market in the late 2000s with the FastJet, while companies such as Fuji and Xerox began showing early single-pass systems for labels and commercial applications around 2008. The flurry of major single-pass technology demonstrations at drupa and ITMA in 2015 in applications ranging from textile printing to corrugated board manufacturing underscore that the potential of the technology may soon be fully realized.
But even with the intense expectations surrounding the single pass today, ceramic tile printing is the only sector where it has achieved market dominance so far. Haak points to technologies that needed to catch up with the concept. Inks with better viscosities and jetting behavior were needed for extremely high-speed printing, for example. He also cites the breakthrough of printheads with ink recirculation architecture at the nozzle plates, which emerged five years ago.
A closeup of the original SPICE engine, using two Xaar 500S printheads, completed just days before its unveiling at drupa 2000. Barco switched to Toshiba grayscale heads by the formal launch.
Cooper notes that as the resolution and speed of single-pass technology have increased, so has the challenge of managing data, going far beyond RIP processing to how information flows through the entire plant. With no makeready time, for example, the pressure on job staging becomes enormous. “You have to keep those machines fed,” he says. “They’re basically white sharks chewing the files up. Machines are getting faster; printhead technology is maturing. But it really gets down to information management and reducing the number of touches that people have.”
Eve remains optimistic about single pass, but believes that each application presents a different challenge and adoption curve. He points out that it’s not unusual for technologies to appear many years before they gain widespread acceptance, drawing a parallel with digital cameras, which were available long before the inevitable replacement of silver-halide film. “When industries do start taking in a new technology, it often moves quicker than people were expecting,” he says. “There’s often a very long lead-in where not much seems to be happening, and then in quite a small number of years, things flip.”
Cooper is also bullish, noting that WestRock’s Dotrix Modular press is still in operation today. “That machine spawned a lot of other designs as you look at the systems in the label industry and some of the others that are out there today,” he says. “It gave us a really strong foreshadowing to what’s coming. Single pass is the future; there is no question about it.”
Read more from Screen Printing's December 2017/January 2018 Innovation Issue.