Beyond Substrates: Advancing Technologies, Wide Selections for Digital Printing

Digital printing is steadily encroaching on the packaging space, and before long digital presses will be expected complements to litho and flexo systems at successful printers and converters. Driving this are changes in the consumer goods market. The average supermarket has increased its SKU count about 25 percent in the last few years, even as available shelf space has remained relatively constant.

"This creates fierce competition that drives brands to test-market more new products, bring them quickly to market and remove them as end-of-life nears," says David Murphy, director of market development at HP Graphics Solutions. "Seasonal, promotional and localized versions are increasing demand for tight production and inventory management. Brand owners are realizing that digital print can positively impact operating margins with shortened supply chains, streamlined logistics, shorter run lengths, faster turnaround times, and minimized inventory." And all of this is happening right now, with some folding carton converters seeing decreases of up to 20 percent in average run lengths.

Package printers and converters are eyeing digital presses as a way to address these challenges, as are some commercial shops that are dipping their toes into packaging. Adding digital presses can deliver clear value to shops wrestling with such challenges. In shops that have made the commitment to digital printing, it's common to see conventional and digital presses queued up with jobs that take advantage of each machines' characteristics. (see cover story, Another Tool in the Box on page 10).

The advantage of digital is the ability to produce short runs—even only a few hundred pieces—profitably or to add variable content to an individual label or carton. The press may provide the operational advantage, but making it all work are the substrates.

The substrate issue

When deciding to use a digital press, two concerns usually rise to the top: is the range of available substrates wide enough to meet customers' needs, and will the ink and toner stick to the often slick-surfaced or specialized substrates used for labels and folding cartons?

In most cases the answer to both questions is yes. There are abundant substrate options for digital presses and ink or toner adhesion is just chemistry and physics. Still, the inks and toners used in digital printing are different than those used in analog printing. Their adhesion and penetration characteristics mean they interact differently with the surface being printed, requiring varying levels of heat and light to dry and bond an image to a substrate. These are not show stoppers. Thanks to continuous collaboration between press vendors and substrate manufacturers, all digital presses used for label and packaging applications can handle a wide range of substrates, in many cases the same ones used on conventional presses.

"Our presses can run vinyl, BOPP, PET, PVC, semi-gloss paper and more—substrates label printers already have in stock," says Kelly DiMarco, product manager for Jetrion's line inkjet presses, which include UV and LED options. "Customers can work directly with the same substrate suppliers they always have and use the same material they run on their conventional presses. We don't sell any substrates for label printing."

"The Epson SurePress L-4033AW and SurePress AQ ink have nearly 100 percent compatibility with standard label substrates without pre-treatments or coatings," notes Mike Pruitt, Epson SurePress product manager. "Customers can purchase materials directly through the substrate vendor."

Adaption required

It's not just substrates that have adapted to the digital presses. The presses, imaging technologies, and inks and toners have become increasingly sophisticated and offer more flexibility with respect to substrates. Inkjet presses such as those offered by Jetrion and Epson, use inks designed to work with standard label substrates. They can handle a somewhat wider variety of label-specific materials than electrophotographic (EP) presses. They are also adept at handling metalized films and very thin or heat-sensitive materials, making them attractive for applications that can be challenging to run on some EP presses. Both HP Indigo and Xeikon presses can also print on some metalized films and heat sensitive stocks. This was once considered impossible, but new toner chemistry, such as the lower fusing temperature of Xeikon's Ice toner, open the way to printing on some metallic films as well as other thinner and lighter stocks.

"For dry toner printing, there is no difference," says Filip Weymans, director of segment marketing and business development for Labels and Packaging at Xeikon. "The label and folding cartons materials used on the Xeikon press are identical to those for conventional printing." As a guide to the available choices, Xeikon offers a 21-page catalog of label and packaging substrates that have been qualified on its presses.

"In some cases, there is little or no difference between conventional substrates and digital substrates," agrees HP's Murphy. "It depends upon the type of material, coatings and other factors. Some materials intended for digital presses have added chemistry for better ink adhesion, but some conventional offset papers are engineered similarly—just with different chemistry."

Long-time flexographic press vendor Mark Andyrecently introduced a flexo and UV inkjet hybrid printing system that lets customers use both digital and analog technologies on common paper and film label stocks. "In many cases standard, non-treated substrates will provide the right level of output, but in-line priming is available if pre-treatment is required," notes Jeff Feltz, director of new business development.

When in doubt, ask

Digital press and substrate suppliers invest substantial resources to ensure compatibility between press and substrate. HP, for example, tests substrates for its Indigo presses at Rochester Institute of Technology and at its own facility in Singapore. Xerox has a long-standing testing lab on its Webster, NY, campus that can best be described as a substrate torture facility. Xeikon has technology centers in Itasca, IL, and in Lier, Belgium. Epson and Jetrion test substrates and work with customers to ensure a material will perform as required.

At these facilities, vendors conduct rigorous testing of any material that can be run through their machines. They work with substrate suppliers to help fine-tune the material to the characteristics of a given press, such as the chemistry of inks and toners, melting and fusing temperatures, and how the colorant is laid down on the surface. Both types of suppliers can guide you in selecting substrates that will work reliably on your press, and provide lists of approved or certified materials. And even when a material fails to obtain a pressmaker's seal of approval, you still may be able to use it successfully if you tap the suppliers for additional intelligence.

For example, on inkjet presses, "…some materials require a primer to aid ink adhesion or need corona treatment to pre-heat the surface immediately before the ink is applied," explains Jetrion's DiMarco. HP Indigos can be configured with a pre-treating system to prepare substrates prior to imaging. Press and substrate vendors know when these additional steps may be required, so be sure to ask when a job requires material you're not familiar with or one that isn't on the list of approved substrates. Obviously, it's important to test unknown materials in advance, so ask a substrate supplier for a sample you can test to ensure a job will run reliably.

The press vendors can get into deeper detail, too. With reasonable notice, most are able to test new or unfamiliar materials on your behalf, changing print speeds, temperature levels, web tension and other variables to determine if a substrate can reliably deliver satisfactory results. "We work with customers to certify a substrate or ensure whether one they want to use will work for the application they have in mind," affirms Weymans.

"In the case of packaging, much of the final testing is done via laboratory analysis or evaluation at a customer site," explains Murphy. "Some packaging requires a high degree of testing and analysis, so there are many components that should be evaluated by the printer or end user. Many of the tests evaluate more than just the printing and media. For example, coatings and structural integrity are also tested as part of the entire package."

Digital printing is here to stay in the packaging space and will become more important over the next few years. Taking advantage of the value it offers requires balancing imaging technology and substrate selection to achieve the best possible results. pP