By Debbie Thorp
The article was first published in “Screen Printing” magazine, June/July 2017 issue

The digital revolution has its sights on a new challenge, and decorating three-dimensional objects offers no shortage of puzzles or possibilities.

Product decoration using inkjet technology isn’t new – systems have in fact been on the market for many years. But recent developments have made decorating three-dimensional objects (not to be confused with 3D inkjet or additive manufacturing) one of the most talked-about segments in the industry.

Sales of small-format flatbed printers designed for decorating promotional items are increasing; more vendors are entering the market and the systems feature new capabilities. Also, we’ve seen significant developments in the mid- to high-end range of production printers. Systems that were demonstrated at tradeshows a few years ago are now proving themselves in real production environments.

Market drivers

From medical devices to consumer goods, the possibilities for direct to ...From medical devices to consumer goods, the possibilities for direct-to-object decoration are vast. Courtesy of EPSPersonalisation and engagement are buzzwords that have been permeating marketing campaigns and social media in recent years with companies vying for “likes” on Facebook and developing ever more innovative ways of enticing us to buy their products. Numerous fast-moving consumer goods companies are now using digital printing technologies to add value to their brands and increase the “user experience.” What arguably started with Coca Cola’s “Share a Coke” campaign has exploded into personalised Nutella jars, Heinz soups, My Heineken bottles, and even customized dog food with Purina’s Just Right range – and there are many, many more examples.

The benefits and drivers for using digital printing technologies are well-known, including cost-effective short runs; just-in-time production; design freedom; no screens, clichés, pads, or time-consuming setup costs; and variable-data capability offering the potential for every product to be different. Then there are the particular advantages that inkjet technology brings as a noncontact technology that can print onto different product shapes – not only flat objects, but also tubes, conical shapes, and even tubs. Inkjet can also print onto structured surfaces, creating unusual visual and haptic effects, enabling decoration in areas not possible with labels. In short, inkjet can potentially operate in the same space as screen, dry offset, and pad printing – and yet offer the additional high-value benefits of a digital print technology.

Inkjet product decoration is not a new phenomenon. As mentioned, small flatbed inkjet systems have been on the market for many years, successfully decorating promotional items such as lighters, mobile phone cases, and USB sticks. But recently, we’ve seen several new vendors enter the market, offering both small- and medium-sized systems that are more advanced both in productivity and capability. Some of these units can print bigger items than before; however, most significantly, we’re seeing that many systems are now capable of printing onto curved objects – tubes, cylinders, and bottles – opening up new opportunities in product customization and personalization at a low entry cost.

Although most inkjet printers designed for product decoration cannot compete with the productivity and cost-effectiveness of screen and pad printing, the latest generation of production inkjet systems go beyond the short-run argument for adopting digital. Today, some of these systems can print 15,000 bottles per hour and have the capability to reach up to 36,000 bottles.

Interestingly, a couple of surprising names have entered the market. One was Xerox, which drew crowds at drupa last year printing personalised bottles on its Direct to Object (DTO) printer. Heidelberg drew similar crowds at InPrint 2015 in Munich with the launch of its Omnifire 250, printing onto footballs for show attendees. Heidelberg showed the unit in the US for the first time at the InPrint 2017 show in Orlando; last year at InPrint in Milan, the company unveiled a larger, full-colour version, the Omnifire 1000. Whether large or small, printers and converters now have many options when considering whether inkjet technology fits into their product decoration services.

Breaking Down Technology Barriers 

Printing onto spheres, cylinders, and uneven surfaces is a challenge ink...Printing onto spheres, cylinders, and uneven surfaces is a challenge inkjet developers have happily embraced. Courtesy of Roland DGAThe increasing adoption of inkjet technology for product decoration demonstrates the market’s acceptance that it’s a reliable technology capable of being used not only in small systems, but also implemented in true industrial environments – even in high-throughput, 24/7 manufacturing lines. Achieving this level of reliability and robustness is the result of many years of innovative system design, process development, advances in ink formulations and curing technologies, and data processing software to enable variable-data printing at high speed and high resolution.

Inkjet inks (typically UV LED-curable) must adhere to a wide range of substrates including glass, metal, and a multitude of plastics. Different substrates require different pre-treatment processes such as alcohol, flame, plasma, corona, or coating primers. Post-print varnishes and protective top coatings may also be needed. System developers are beginning to incorporate these processes. For example, the Xjet from Inkcups Now offers the DigiBond Primer for printing onto metal; Apex Machine provides an optional inline pre-treatment station for their DB1000 and DRT2000 Digital systems; and Engineered Printing Solutions (EPS) offers pre-treatment and vision system options for its XD070 and XD060 systems.

Certain substrates benefit from a base coat of white ink to make the overprinted colours brighter, but matching the opacity of a screen printed white is a challenge for inkjet. Multiple printheads or passes may be needed to jet an acceptable layer of ink. Many system vendors now offer an optional white ink station; in larger production systems, white is standard. However, an alternative to using inkjet for the white base coat is to take a hybrid approach and combine the strength of screen and inkjet technologies in a single line. This has been shown by KBA-Kammann in its latest K20 series. The company has taken the approach that the inkjet stations must fit within the system architecture of its K20/K15 series screen printers, with no loss of speed – so that, according to job requirements, users can produce hybrid technology decorated products. For example, they could use the screen stations for the white precoat and spot colours and inkjet to print CMYK.

One of the often-cited benefits of inkjet is that it is a noncontact technology. Industrial inkjet printheads have been designed to print onto flat surfaces with an optimal throw distance between the printhead and substrate of less than 1 millimetre for small drops. Such small drops decelerate quickly as they travel to the surface; if the throw distance is too great, then the drops may not land in the intended place and image quality deteriorates. Larger drops can jet further (up to approximately 5 millimetres), but compromise the graphical image quality. Printers are finding they can mitigate this through careful selection of images, using inkjet to great effect to decorate objects with textured or contoured surfaces where it would have been impossible to apply a label. Krones, a major beverage machinery supplier, took this approach when they launched the Decotype R at Drinktec in 2014. At the show, they printed shampoo bottles with shaped surfaces, creating interesting visual and haptic effects that not only replaced the label, but also surpassed it with effects that would have otherwise been impossible. The technique has been widely applauded: Cycling bottles from Krones won a 2015-2016 A’Design Award, and the shampoo bottles were awarded an Oscar dell’Imballaggio by the Italian Packaging Institute in 2015.

We’re also seeing more systems that can accommodate larger or taller objects. The FJet XL from EPS, for example, can take items up to 5.9 inches high; the Azon UV Matrix can print on products up to 7.9 inches high; and Mimaki’s UJF-3024 HG (High Gap) unit can accommodate objects up to 5.9 inches high. German company Ritzi has the first installation of the Heidelberg Omnifire 1000 to decorate large automotive components, such as trim strips, switches, dashboards, and other finished components as part of their production process.

Designing inkjet systems that print well onto flat surfaces is challenging enough, requiring a multidisciplinary approach – including, but not limited to, mechanical, electrical, electronic, fluidic, and software engineering; image processing; colour management; and system control. Building an inkjet system to print directly onto a bottle or tube requires all of the same disciplines, but with the added complexity of the third dimension. In order to create a good quality print, the developers must consider the curvature of the object to be printed, the orientation of the printhead, and the time of flight of each drop from each nozzle.

When thinking about printing onto objects, it can be useful to imagine that shape as being flat. For example, if you take a tube, cut it lengthwise, and lay it flat, it becomes a square or rectangle, depending on its height. The shape is now a familiar one for inkjet printing; the “flat” image just needs to be wrapped around the tube.

Developers use different positioning options for the printheads, depending on the overall configuration of their system. Some want to ensure that inkjet fits seamlessly into an existing process or product-handling mechanism, and this can dictate the way the heads are positioned. Typically, printheads jet downwards, and this is well-suited to systems using mandrels to move the products, but in some systems, items such as beverage containers may be gripped by the neck and presented vertically to the printheads, which means that the heads must be positioned in “skyscraper” mode, jetting sideways onto the object.

A number of systems are now available for printing onto tubes or cylinders. Among the small-format flatbed printers, Mimaki introduced the Kebab option for its UJF series, Roland markets the RotaPrint attachment, EPS offers the Bottlejet, Direct Color Systems has the EasyCyl attachment for its 1024 printers, and AzonPrinter offers the Rotax. Other production tube decoration systems include the Michelangelo KX48P from Martinenghi, launched at MetPack 2013, and the new ServoJet from OMSO introduced at last year’s K Show.

An increasing number of systems can now print not only onto tubes, but also onto conical or tapered shapes as well, which are far more challenging. If you cut a cone lengthwise and lay it flat, you would create a shape that looks like a section of a circle. During printing, as the cone narrows, the resolution changes, as does the speed of rotation under the printhead. In order to print an image successfully onto the whole circumference of a conical object, you must use image compensation software that employs special screening and/or colour management techniques to correct for the changes in dot gain. Differences in drop time of flight, nozzle misalignment, and density changes all need to be corrected as well in order to produce a fully compensated image with minimal image artefacts.

The Helix from Inkcups Now uses patented technology to print onto straight-walled and tapered cylinders at up to 1200 x 1200 dpi and up to four pieces per minute depending on image/product size and print quality settings. The DigiCup from Polytype can print not only onto cones, but also onto more complex shapes such as tubs. Systems from Machines Dubuit and KBA-Kammann have also demonstrated the capability to print conical shapes as well as tubes and cylinders.

Regulatory issues present a further challenge for the adoption of inkjet in some applications, but significant strides forward have been made in the development of low-migration, low-odour UV curable inks by companies such as Agfa, Sun Chemical, and Kao Collins. These inks enable direct-to-shape printing on products such as medical syringes and PET beverage bottles. Further ink innovation is expected, which will open up more applications for inkjet in product decoration. In the field of PET beverage bottles, KHS – another giant in the beverage filling and packaging industry alongside Krones – also introduced an inkjet system at Drinktec in 2014. NMP Systems, a wholly-owned subsidiary of KHS, is now responsible for the inkjet technology, which is marketed as Direct Print Powered by KHS. The company collaborated extensively with Agfa during the development of the system (originally called the Innoprint) and achieved regulatory approval for direct printing of PET beverage containers with their low-migration UV inks while achieving full recyclability of the printed product – an important factor in sustainability. An early success for the direct print technology, widely covered by the media, was the printing of PET beer bottles by the Belgium brewery Martens Brouwerij in 2015 for a special film promotion. The campaign incorporated augmented reality via a smartphone app so that the characters printed on each bottle could interact with each other, making them “talk.”

Production Capable

Krones cycling bottlesKrones cycling bottlesThe question that users often ask when considering a digital technology centres on throughput: Can it match the existing analogue printing system and be incorporated without slowing the whole production process? The answer, of course, depends on what is being compared, and whether inkjet should even be considered in this way. Is inkjet a replacement technology or a complementary one? When evaluating the systems available today, the answer, perhaps surprisingly, is both.

Several systems on the market today can meet demanding throughput expectations. Printhead technology has advanced considerably in terms of print speed and resolution. This is evident in the single-pass industrial systems for flat/semi-flat objects that are now part of production manufacturing lines – for example, the Digapex series from Apex Machine, which offers inline pre-treatment and a variety of automatic loading, unloading, and product handling options. Systems dedicated to the production of specific objects have also been shown. Sacmi has developed the ColoraCap, and EPS recently showed a version of its XD070 for plastic bottle tops at the K Show 2016 – systems that both incorporate full variable-data capability. In the mid-range, Machines Dubuit offers the 9150 (up to 800 pieces per hour) and the 972 (up to 4000 pieces per hour).

And inkjet is capable of even higher productivity. Plastic beverage container decoration lines typically run at 36,000 units per hour. NMP’s Direct Print industrial printers can be integrated into PET bottle filling and packaging lines running at 12,000, 24,000, or 36,000 bottles an hour. The design of the systems is modular, with each colour typically printed by a separate rotating carousel containing 12 printheads. The Krones Decotype R can print up to 24,000 specially shaped units per hour and up to 15,600 cylindrical containers per hour in six colours. At the next Drinktec show scheduled for September 2017, both companies are expected to show the next generation of these production systems.

In most installations at converter sites today, inkjet plays a complementary role. However, the German company Ritter – the first user of the D240 from Hinterkopf – has taken a radical step and decided to replace its existing screen printing lines with inkjet. Ritter has installed two D240 units to print photorealistic images with variable data onto plastic cartridges at their site in Germany. CEO Ralf Ritter has commented that “one D240 machine delivers the same output as three screen printing lines.” The company has also benefited from an energy savings of more than 450,000 kilowatt-hours per year and reduced carbon dioxide emissions by 270 tons since implementing the inkjet systems.

Next Steps
Inkjet has conquered the challenges of printing onto a wide range of flat and semi-flat products plus tubes, cones, and even tubs – so what will be next? The answer, naturally, is more complex shapes. Software development is underway to print an image covering the whole surface area of a sphere. A parallel step is decorating complex, undulating, or non-uniform curved surfaces, such as industrial components. Implementing advanced, multi-axis robotics will be critical for this next stage of inkjet’s development, together with vision systems and innovative software for dynamic surface mapping and compensation. Further innovation in ink technology and process development will also be critical to opening new market opportunities, in systems both large and small. We also expect to see further exploration of hybrid technology devices that maximize the strengths of inkjet and screen printing together. At both the low and high ends of the market, the choices for printers and convertors will continue to expand, creating new opportunities to add value through product decoration.

Debbie Thorp from Global Inkjet Systems will hold a presentation during DCP 2017: “Inkjet printing onto spheres”.