Breakthrough in Direct Digital Can Printing

Tonejet’s electrostatic drop-on-demand can printing technology has taken some time to mature since it first burst onto the scene. That makes this SoluCan installation awfully interesting.

This robot picks freshly printed cans six at a time from the vacuum conveyor discharge and places them on the infeed conveyor of the curing oven.
This robot picks freshly printed cans six at a time from the vacuum conveyor discharge and places them on the infeed conveyor of the curing oven.

In the Canadian Province of Quebec, digital direct printing on aluminum cans is taking a notable leap forward.

            Behind it all is a startup called SoluCan, which is the first company in the world other than Tonejet themselves to install a Tonejet Cyclone direct-to-pack digital beverage can printer. President Sebastien Baril says he and founding partner Jean-Francoise Gaudreault, each of whom has substantial experience in the package printing space, have been evaluating and analyzing digital direct-to-pack printing technologies for about the past five years. Eventually they put their money on Tonejet and, in a 16,000-sq-ft leased space in the town of Trois-Rivieres, are now serving the short-run decorating needs of a growing number of customers.

            “The 2019 installation went as smoothly as we could have hoped,” says Baril, who adds that the production area housing the new line is kept at a consistent humidity level and a temperature of 22 degrees C. “It’s not that the equipment is somehow fragile,” he notes, “it’s just that this is the environmental sweet spot when it comes to efficient operation.

            “We’ve had tons of interest from around the world already. The Cyclone is the backbone of SoluCan’s offering, and we consider it a total game-changer. The quality is second to none, and the ability to print using a food-safe process is key. Next we’ll work with Tonejet to expand our geographical footprint. But we couldn’t be happier with where we are right now at this point in time.

            “Technically we’re still in a beta phase, being the first commercial user of the technology and all. There’s a learning curve to preparing the digital files at the front end, for example. But being first always comes with challenges, and we’re tackling them now.”Water, craft brew, and Kombucha are beverage markets uniquely suited for direct digital print on cans.Water, craft brew, and Kombucha are beverage markets uniquely suited for direct digital print on cans.

            So what’s behind the Tonejet technology? Like all digital printing technologies, it does away with printing plates, make-ready, ink changes, and other setup costs. Every image to be printed on a container can be different than the one before it because jobs are uploaded with the Cyclone digital job manager. And, says Tonejet, the ultra-thin ink layer means lower ink costs and better flexibility and adhesion under stress compared to competing technologies.

            According to Tonejet Sales Manager Marvin Foreman, Cyclone is a digital printing system that deploys electrostatic drop-on-demand printing technology. “It combines a novel printhead architecture with proprietary ink formulations,” says Foreman. “We’ve got a charged pigment particle suspended in a carrier fluid. The pigment is jetted from ejector tips and during that process the carrier fluid evaporates, so that all we’re left with on the substrate is pigment. We then bind the pigment to the substrate with an overprint varnish, which is the same overprint varnish used widely in the aluminum can-making business.”

            This electrostatic drop-on-demand printing technology delivers a 600 dpi greyscale CMYK resolution at a speed of 60 cans/min. When asked for more detail on the ejector tips, Foreman answers this way. “It’s a four-color CMYK process, so there’s one print head for each color. Picture a series of hair combs mounted in a print head. The pigment is ejected from the tips of the combs’ ‘teeth,’ which number 150 or so in each print head. We apply a pulse voltage that governs how long each ejector will fire, and that’s how the pigment, suspended in its carrier fluid, is jetted onto the substrate. But the carrier fluid evaporates in fractions of a second, which is why the only thing left on the substrate is the pigment.”

            The nozzle-free format, combined with automated ultrasonic print head cleaning technology, provides a reliable industrial operation, one that Tonejet has used with limited success for the past two or three years. But the SoluCan installation has the potential to change everything. What makes it so notable are the systems upstream and downstream of the Cyclone printing system itself. The challenge of developing these systems, Foreman is the first to admit, is the reason why it’s taken Tonejet so long to get a truly production-ready solution to the marketplace.

            “The fundamental technology goes back some twenty years,” says Foreman. “We went into it thinking we’d just build a beverage can printing machine. But what we quickly discovered is that the aluminum cans we were trying to print on are filthy. They’re either covered in dust or they still have remnants of the lubricant used as part of the necking-in process that gives the can its shape. It was a nightmare trying to print on such a surface. So we had to devise a method and machinery to clean and prepare the surface for digital printing. Also hugely challenging is that aluminum beverage cans are incredibly flimsy when they’re empty. So that meant we had to come up with a way of gently handling the cans as they move through the process.”

            Before diving into the details of the impressive pallet-to-pallet can decorating solution that Tonejet and SoluCan came up, it’s important to note a background dynamic that makes this technology such a good fit in today’s Quebec. On February 24, Quebec's Ministere de l’Environnement et de la Lutte contre les changements (MELCC) issued a letter forbidding the sale of aluminum cans with shrink-sleeve labels or pressure-sensitive labels. Both these labeling formats have grown increasingly popular in sectors like craft beer because they make it possible to order a small number of labels for beer variety X and another small number of labels for beer variety Y without having to order preprinted cans in the enormous truckload quantities that aluminum can producers require. Unfortunately, as the number of these labels--regardless of whether they are PETG, PVC, or paper--reaching Quebec’s aluminum recycling centers has increased, they’re beginning to contaminate the previously pure stream of aluminum cans the recycling centers prefer.

            “We anticipated that this would happen, and it was certainly a driver behind our investment in the Tonejet technology and the start up of our company,” says SoluCan’s Baril. “We could see clearly that it spelled opportunity.”

            Now for the technology itself. The closed-loop nature of SoluCan’s new can-decorating operation is one of the things that makes it so impressive. (Be sure to go here  to see a video of a Cyclone production system similar to the one operating at SoluCan.) Pallet loads of bright-stock cans are automatically depalletized at one end and decorated cans get repalletized at the other end. The equipment at both ends was supplied by Ska Fabricating , the same OEM that Tonejet relied on as it built out its Cyclone demo capabilities in England. So how did equipment from a Colorado-based machine builder wind up in a facility outside the storied city of Cambridge in the UK?

            “Basically they were the only ones that would build something in the size we needed,” says Foreman. “Before we moved to our current space we were working out of an office environment, which made any conventional depalletizer too big. So we got the guys at Ska to build us a small one, and they did such a good job we’ve continued the relationship. They make good equipment.”

            Depalletized cans go from mass flow to single file by way of simple line pressure. A vision inspection unit causes any cans that are dented or out of round to be rejected. Then the cans move down from their overhead level by way of a twist conveyor that also reorients them so that they no longer sit on their bottoms but sit rather on their sidewalls. Cans now enter an enclosed cabinet that is an intermittent-motion can washing and priming system. Purpose-built by Tonejet, it’s essentially a large oval-shaped track on which are mounted multiple pairs of tools.On this oval-shaped track are multiple paired tools. Each pair grips one can from opposite sides and carries it first past a belt that wipes down each can surface. Then each can is rotated against a roller coater for application of a proprietary toner. Only then are cans ready for digital printing.On this oval-shaped track are multiple paired tools. Each pair grips one can from opposite sides and carries it first past a belt that wipes down each can surface. Then each can is rotated against a roller coater for application of a proprietary toner. Only then are cans ready for digital printing. Each pair grips one can from opposite sides and carries it through the oval-shaped circuit. Along the way, each pair of grippers pauses briefly at two stations. In the first, the can rotates so that a belt can perform a physical wipe down of the external surface of each can. A short distance later, each can stops again, this time to rotate against a roller coater for application of a proprietary Tonejet primer that gets thermally dried. “It isn’t a great deal of heat used for the drying,” says Foreman. “It’s a very quick evaporation, because the primer has to stay reasonably soft."

            A few feet away from the washer/primer sits the Cyclone digital printer, and now the cans are ready to be transferred onto one of the 20 mandrels that are at the heart of this printing system. An intermittent-motion flighted conveyor positions each can directly in front of one of these mandrels and pushes the can onto the mandrel. Each mandrel is mounted on a mover of an iTrak linear servo motor system from Rockwell. Each mover, once a can has been pushed onto its mandrel, takes its can through the iTrak’s oval-shaped track and beneath the four electrostatic CMYK print heads. Upon arrival in a print station, the can rotates on its mandrel as ink is jetted onto it. Foreman says the introduction of the iTrak technology was a big step forward in the evolution of can-handling at Tonejet.

            “In some areas of the oval-shaped track through which the cans move we need to go really fast, but in other areas we need to go slow,” says Foreman. “With the iTrak’s programmable movers, which move completely independently of each other, you can change the timing and speed in just about any way you wish. The part where we need to slow down considerably is where we have an air tunnel that evaporates the last bit of the carrier fluid from the pigment. Immediately after that we use an analog roller coater to apply an overprint varnish.”

            Thermal curing of this varnish comes next, after which the cans reach the end of the iTrak and are unloaded from the Cyclone open-end-up on a vacuum conveyor discharge that keeps each can fixed in one spot. Freshly printed cans are unloaded from the Cyclone printing system open-end-up on a vacuum conveyor discharge that keeps each can fixed in one spot, leaving no opportunity for one can to touch another and possibly mar the uncured surface.Freshly printed cans are unloaded from the Cyclone printing system open-end-up on a vacuum conveyor discharge that keeps each can fixed in one spot, leaving no opportunity for one can to touch another and possibly mar the uncured surface.“They’re not cured yet,” Baril explains, “so the vacuum conveyor ensures that they have no opportunity to touch each other and possibly mar the surface. The vacuum conveyor brings them to a robotic pickup that transfers six cans at a time onto the infeed conveyor of the curing oven. Four minutes later the cans emerge from the oven and enter the Ska Fabricating palletizer to complete their pallet-to-pallet loop.”

            Since installation last December, the Cyclone has produced hundreds of thousands of cans in batches ranging from 48 to 165,000 cans. While craft brewers are a key target market, so are the marketers of canned water, kombucha, and wine.

            In addition to the benefits this digital printing technology brings in terms of keeping labels from contaminating the aluminum recycle stream, it also dovetails nicely with today’s trend toward making the package a digital portal. SoluCan General Manager Jean-Francois Gaudreault put it this way in a recent article that appeared in the UK’s Digital Labels & Packaging: “[Digital printing allows the beverage can to be] transformed into a totally digital portal. Linking packaging to the digital world, accessible via your smartphone or laptop, is a total game-changer and provides a powerful marketing tool. In addition to using the space to promote events, marketing promotions, etc., you can include codes to link to augmented reality apps and even invisible codes and water marking.”

            When asked if the relatively slow speed of the Cyclone digital printing system, 60 cans/min, is viewed as any kind of a drawback, both SoluCan and Tonejet said not at all. “Naturally, since this is a new technology, we have a wish list of things we might like to see optimized, and speed is on the list,” says Baril. “But for now it’s not a huge priority.”

            More of a priority, he adds, are plans to install a second Cyclone system some time later this year. “Right now we’re only printing 12-oz cans,” says Baril. “The new machine will handle both 12- and 16-oz cans.”

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