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Direct digital printing on rigid containers

German ingredient maker Döhler was among the first to take advantage of direct digital print on both glass and PET bottles. New technology now emerging in this space is impressive.

The infeed and discharge carousels of the DecoType C are prominent features of the machine.
The infeed and discharge carousels of the DecoType C are prominent features of the machine.

Editor’s note: Direct digital print on rigid containers is being explored aggressively by at least four major machinery builders: Krones, Till, KHS, and Tonejet. But with two exceptions, customers using these technologies on a commercial basis have been reluctant to be identified. Exception #1 is KHS, whose Direct Print Powered by KHS is being used by Martens Brewery in Belgium (see pwgo.to/3409). Martens installed a next-generation version of KHS’s Direct Print technology some time in 2016. Exception #2 is Krones and its DecoType technology. A prototype of this system is up and running at Döhler, a German maker of natural ingredient systems and flavorings for the food and beverage industry. Presented here is a look at Döhler’s DecoType application followed by a peek at how Krones plans to expand this technology along with partner Till GmbH, a German company that is 51% owned by Krones.

Headquartered in the German city of Darmstadt, Döhler not only produces natural ingredients for the global food and beverage industries but also develops new recipes and complete solutions for the trendy foods and beverages of tomorrow. The innovative formulations are then filled in sample bottles, either glass or PET, and dispatched to Döhler’s clients. These sample bottles had always been given simple labels applied manually by the lab staff, and the labels made no atttempt to provide anything more than fundamental technical data. From the viewpoint of Christian Bazlen, who works in marketing at Döhler, this approach left room for improvement, primarily because it was so boring.

“In the rest of our business we’re all about creating an added value for our customers and partners,” says Bazlen, who is also responsible for corporate design at Döhler. “We wanted the sample bottles to look more visually appealing, and we also wished to have an option for telling customers a bit more about the product inside. Not to mention that we wanted to be able to show them what their products of the future might look like in a bottle.”

The solution Döhler opted for was digital printing directly on its bottles by way of a DecoType C digital printing system from Krones. Described by Krones as a “lab machine,” it’s been up and running in the Darmstadt plant since mid-2015.

“When a customer orders a product,” says Bazlen, “the staff chooses the appropriate container types and places them in one of the 21 pockets of the DecoType’s infeed carousel. The DecoType is given the printing order for every single bottle by our materials management system, whereupon printing is started.” A run is typically anwhere from five to ten bottles.

A central bottle starwheel picks bottles from the infeed carousel by their necks. The starwheel completes one full 360-degree rotation so that bottles can be pretreated and cooled. The pretreatment is done by way of flame for glass and Corona treatment for PET.

The Konica Minolta digital piezoelectric ink-jet print heads deployed by the DecoType C contain the four basic colours of classical four-color printing, comparable to a standard ink-jet office printer: cyan, magenta, yellow, and black. Two additional printing heads supply white and a transparent primer, which serve to enhance adhesion. White can be used for either printing pure white areas or for combining white areas with four-color printing. The inks used were developed by Krones in conjunction with the Marabu company.

Printed bottles pass through a UV-curing compartment and then the central bottle starwheel deposits the bottles into the pockets of a discharge carousel closely resembling the infeed carousel. From there the operator takes the printed sample containers and prepares for the next run. The DecoType C lab machine can handle up to 112 bottles an hour.

“This system renders us highly flexible when it comes to bottle design,” says Bazlen, a media designer and communication specialist by trade. “What’s particularly innovative is the fact that we can print on both solid glass material and on soft, flexible PET with just one inking system—and this we can do without having to modify the machine, i.e. without any make-ready times. Moreover, digital printing is, of course, significantly less costly than screen or pad printing.”

On the DecoType C, Döhler handles commercially available 0.5-L PET containers as well as three different glass bottle varieties: a 0.33-L long-neck, a 0.5-L NRW (Nord-Rhein Westfalen, the area where this classic German bottle originated), and a 0.33-L “mini” bottle. “We’re making full use of all the design options available, depending on what the bottle is required to look like later on,” says Bazlen. “Here, we can give free rein to our creativity, ranging from very generic to extremely specific and goal-driven designs.”

Döhler customers are delighted with the graphics they now receive on their bottles, so the Döhler marketing people feel they’ve found just what they were looking for when they set out to improve upon the hand labeling approach they used to take. “The design work only has to be done once, i.e. when the marketing department creates the labels on the computer,” says Bazlen. “Except for metallic effects, we have the same options as those offered by conventional printing methods.”

Bazlen is a big believer in the future of digital container printing. “We wanted to break new ground in regard to sampling, and with the DecoType we’ve hit the bullseye. I think that in the future it will be possible to use digital printing for decorating any kind of container—not just round ones but also concave, convex, or thermoformed bodies, just about any special-shaped containers for that matter. Digital printing provides customized package designs with a clean printed image. The technology of the kind that Krones has implemented for us in the DecoType C lab machine can also be employed for higher-speed machines, and could likewise be used in any beverage bottler’s normal production operation.”

The DecoType Family
Döhler’s use of its lab-sized DecoType C system is interesting enough in its own way. But between its installation in 2015 and the recent DrinkTec 2017 in Munich, a number of improvements have been made in Krones’ approach to digitally printing directly onto rigid containers. Also, since Krones acquired 51% of Till GmbH in 2014, it’s now an approach that has two distinctly different prongs. While both Krones and Till rely on piezoelectric ink-jet technology when it comes to delivering ink on a bottle, they take two very different approaches to bottle handling. As Krones and Till bring these technologies to the marketplace, they do so as two companies having one product portfolio called the DecoType Family.

The best way to view all of this is in Figure 1. Among the high-output options in the DecoType Family is DecoType Select. Though designed primarily for oval-shaped containers as opposed to the round ones printed at Döhler, and though it offers far greater output than the lab system operating at Döhler, it shares the same fundamental method of bottle handling used at Döhler and relies on the same piezoelectric ink-jet print heads from Konica Minolta. The other three products in the DecoType family, which are more suitable for round bottles, use the bottle-handling technology developed by Till and rely on piezoelectric ink-jet print heads from Xaar. In the following descriptions of each of the four offerings in the DecoType family—and in the video links provided—the difference between the two approaches to bottle handling should become clear.

We begin with DecoType Select. One of the most conspicuous features of the DecoType Select is that it measures nearly eight ft across, though Krones indicates that a next-generation version will be more like six ft. Bottles enter and exit the machine on conveyors that are just inches apart, and the system can be designed to operate with or without pucks. In Figure 2, it’s the conveyor on the left that is the infeed conveyor (see video embedded in this article).

A central star wheel grabs bottles by the neck and hands them off to a second star wheel that places each bottle on one of 60 platforms that occupy the main carousel. An inspection system ensures that each bottle is properly centered. If a bottle is off-centered, the machine stops and an alarm is sounded. Bottles then are pre-treated by means of a PYROSIL® process. Essentially it’s a deposition of amorphous silicon dioxide that ensures ink adhesion.

Now bottles rotate past two Konica Minolta print heads for two bumps of white followed by four more stations that deliver yellow, magenta, cyan, and black. Then come two stations that can be used for custom colors, after which bottles are rotated 180 degrees so that the back of the oval-shaped bottles can pass through white, yellow, magenta, cyan, and black print stations.

One notable feature designed in is that every platform on which each bottle sits has a servo motor that causes it to rotate ever so slightly. This ensures that the extreme left and right edges of the oval-shaped bottle remain as close to the print head as the much flatter central panel. “Without that slight rotational element you’d be throwing the ink a little further than you really want in the areas where the bottle’s curve takes the surface away from the print heads,” says Krones’ Mike Soloway, who manages the DecoType portfolio in the U.S. “This way we keep the entire substrate nice and close for crisp print resolution right up to the left and right edges of the container.”

Bottles exit the main carousel by way of two star wheels that mirror the star wheels responsible for feeding bottles in. All that remains is a UV curing station. Worth pointing out is that included in each of the print stations is an operation called “pinning” wherein UV light cures the freshly deposited ink enough so that it won’t bleed or smear as subsequent colors are applied. Only in the final UV curing station are the inks fully hardened to ensure not only scratch and abrasion resistance but also low ink migration.

The Till technology
Unlike DecoType Select, the other three members of the DecoType family identified in Figure 1 emerged not from the geniuses at Krones but rather those at Till. And while DecoType Select is aimed more at products in the personal care or health and beauty categories, where oval-shaped bottles are plentiful, Till’s technology is designed for cylindrical bottles commonly found in soft drinks and other beverages.

Till’s SmartPrint technology differs from the Krones technology in one fundamental way. Bottles don’t receive yellow at one print head, cyan at the next, magenta at the next, and black at the next. Instead, each bottle gets fully enclosed in a SmartPrint print head. As the bottle rotates on its platform, the Xaar digital print head delivers up to eight colors and eight shades of gray with a resolution of up to 720 DPI. To understand how each print head operates, see pwgo.to/3419.

As Figure 1 shows, the three Till-designed systems in the DecoType family—Performance, Compact, Lab—are designed to provide customers whatever throughput they need. At the low-speed end, the DecoType Lab is largely manually fed. The intermittent-motion DecoType Compact is linear in nature where five containers at a time are fed in, printed, and discharged. The continuous-motion, rotary-style DecoType Performance, on the other hand, is built for speeds even higher than the DecoType Select: up to 36,000 PET bottles/hr. Despite their dramatically different throughput capabilities, each of these Till-designed machines relies on the same SmartPrint print head technology.

The DecoType Performance system is worth a closer look. First, it’s highly modular in nature. It has its SmartPrint print stations mounted in two-station modules on a rotary carousel. The diameter of the carousel is constant, but the number of modules can vary. So a customer looking to minimize capital outlay could order a DecoType Performance system with nine modules, i.e. 18 print stations. Then, if greater throughput is required, additional modules can be added.

A DecoType Performance system capable of 36,000 bottles/min has a rotary carousel holding 48 SmartPrint print heads mounted on 24 print modules. Like all DecoType Performance systems, it does not rely, as does the DecoType Select, on the interplay of feedscrews and starwheels to bring bottles in and out of the print heads on the main rotary carousel. Instead, it takes advantage of HepcoMotion’s PRT2 track system, which features XTS linear servo motor technology from Beckhoff. Watching the movers operate on this oval-shaped component is a vivid reminder of how much potential there is in the packaging machinery sector as linear servo motors, still relatively new, begin making their presence felt. To understand how it works see pwgo.to/3420.

Bottles can range from 47 to 98 mm in dia and stand 100 to 350 mm tall. Fed in on a single-file conveyor, each bottle is picked by a mechanical gripper mounted on one of the 48 movers that slide freely along the oval-shaped PRT2 track system. Each gripper delivers a bottle to a print station and then repeats the cycle. Then at the discharge where printed bottles emerge, the grippers take bottles out of the print stations and place them on a takeaway conveyor.

Why did Till specify paired PRT2 track systems mounted in parallel one above the other for both infeed and outfeed? Because at maximum speed the movers run at 4m/s with a load of 1.5 kg, creating centrifugal forces of up to 1 g per mover on the curves. With a single-track system, the movers would be overloaded. Connecting two track systems one above the other and separated by about 150 mm produces greater stability and allows the movers to accommodate higher loads.

To minimize weight, each mover uses three V-bearings per slide rather than the typical configuration of four. By reducing the number of bearings, a significant reduction in weight could be achieved, thus reducing the load on the guidance and drive systems. The inclusion of bleed lubrication in the slides to provide sufficient lubrication meant that lubrication blocks could be omitted, providing further reduction in weight.

The integrated bleed lubrication system in HepcoMotion’s track system ensures smooth running while extending the useful life of the equipment. Lubricant is dispensed from a cartridge through bores in the slide. The lubricant is carried around the system by the bearings, ensuring an even and constant film of lubricant on the running surface. In this application, a food-compatible lubricant is used.

A key contribution made by the PRT2 track system is that its movers are “smart” enough to populate only those print heads that the control system dictates. So when scheduled maintenance requires that a print station in a given module be taken out of service for an automatic Clean-in-Place cycle, the movers won’t put a bottle in that station until the system’s main controller signals that the station is good to go. This capability, clearly illustrated in this video link (pwgo.to/3420), would simply not be feasible if the infeed took a more conventional starwheel exchange approach like the one found on the DecoType Select.

When pressed to identify commercial users of the machines in the DecoType family other than Döhler, Krones and Till indicate that confidentiality agreements prevent such information from being divulged. It’s a pity, since the commercial user’s experience is often the most revealing when it comes to gauging the impact of any new technology. All the same, anyone interested in the future of digital print for packages will want to stay tuned as these impressive technologies continue to mature.

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