How Corrugated Converters are Maximizing Print Quality

Those living under a proverbial rock may not have noticed what has been happening to the print quality of corrugated packaging and displays in recent years, but the steady improvement hasn’t escaped the attention of brands.

Emma Schlotthauer, chief marketing officer of prepress technology provider Miraclon, says that brands now expect corrugated to create the same kind of “active advertising” for their products as any of the other forms of packaging that they use.

She notes that advances in decorative techniques for corrugated board have helped the medium broaden its repertoire of applications from simple shipping containers to shelf-ready packaging. This gives brands more ways to save time and money while assuring them of the top-quality look they insist on, Schlotthauer says.

Today, buyers of packaging can count on corrugated for quality characteristics that would have been challenging for printers and converters to guarantee even 10 years ago. As Blake Bennett, business process manager at Bennett Packaging, a corrugated printing company near Kansas City, Mo., says in a written response, “Your high-end graphics customers are expecting sharp, clean dots, tight registration, and the highest resolution that you can consistently offer.”

While the demand for high-end color and imagery in corrugated is rising, it isn’t necessarily universal. According to Jeff Wettersten, president of Karstedt Partners, a packaging industry consulting and research firm, the pandemic-driven upsurge in online ordering has left many harried shippers saying, “I don’t care what the package looks like — just get it there.” If the box won’t be going onto a shelf once it arrives, “plain is fine.”

And, continues Wettersten, if graphic quality truly is a differentiator for corrugated, printers and converters then have to ask themselves how they will leverage it. He says this can be done either by gaining market share at competitive prices, or by charging the premium that any other type of high-end packaging would command.

Perennial Penchant for ‘Pop’

The new interest in high-graphic corrugated is nothing new at Sutherland Packaging, says Eric Stanton, the company’s creative and technical director.

Customers have always demanded “graphics that pop, and colors that pop,” and for a long time, the company’s carefully fingerprinted flexographic presses have been able to deliver it. The difference now, according to Stanton, is that flexo platemaking and other aspects of prepress have caught up with what the presses are capable of.

Sutherland Packaging embraced digital print for corrugated by installing an HP Scitex 15500 corrugated press, pictured here. Front row: Edwin Chudkowski, plant manager; Ada Diaz, CSR manager; Arnie Stern, office administration; Manny De Barros, VP of sales. Back row: Galaye Faye, logistics manager; Paul Yost, CFO; Kevin Donahue, controller; Eric Stanton, creative director. Image courtesy of Sutherland Packaging.

Color and graphics can be added to corrugated in several ways, depending on what the quality requirements are. Litho labeling — laminating an offset-printed sheet or label to the top sheet of a corrugated board — is still widely regarded as the highest-quality method of decorating corrugated packaging and displays.

But, advances in prepress have enabled direct printing (a.k.a. post-print, both conventional and digital) and preprinting on linerboard or paperboard to close the quality gap with litho-lam, overcoming many of the limitations that used to mark corrugated as a low-end option for printed packaging.

“Board quality is by far the limiting factor,” says Daniel J. Fry, portfolio manager for corrugated at MacDermid Graphics Solutions. He cites the surface-ridging effect of corrugated fluting and the breakdown of repeatedly recycled fibers as among the drawbacks that typically limited direct-to-board flexographic printing on corrugated to low-resolution (65 lpi to 85 lpi) applications such as reusable shipping containers.

But now, says Fry, advances both in flexo platemaking and in flexo press design are making it much easier to keep dots sharp and stable at the finer line screens that high-graphic printing on corrugated entails.

New Gains for Platemaking

MacDermid’s contributions to this progress include LUX ITP EDGE, a flat-top dot, photopolymer plate designed to print retail-ready corrugated packaging at resolutions up to 150 lpi; and LUX ITP MELO, a thin, soft photopolymer plate that minimizes board crush and holds fine details when printing on low to medium quality board.

Miraclon, which acquired the Flexcel NX portfolio of flexographic solutions from Kodak, uses an advanced platemaking technique to create flat-top dots for consistent print quality at high resolutions.

Colten Freeze (left), creative services manager at Bennett Packaging, and Blake Bennett, business process manager, with samples of the corrugated packaging they produce with advanced equipment that includes a pair of Barberán Jetmaster digital inkjet presses. Image courtesy of Bennett Packaging.

One benefit of the even ink transfer and laydown that Flexcel NX flat-top dots make possible, says Schlotthauer, is not having to create separate plates for solids and halftones. With the flat-top dot structure, both can be combined on the same image carrier, saving stations on the press and yielding better results in direct printing to corrugated.

Another complication of flexo printing for corrugated containers is that many jobs, such as pizza boxes for example, need to be printed only in certain small areas of the substrate, meaning that only correspondingly small areas of the plate have to be imaged. The problem is magnified when jobs like these run on very-large-format flexo presses, where the non-printing areas greatly exceed the space of the sections that get printed.

In these situations, explains Mike Agness, executive VP for the Americas for HYBRID Software, it wouldn’t be desirable, nor perhaps even possible, to make plates large enough to encompass both the image and the non-image areas. He says this is one reason why with corrugated, “the complexity to get to press has always been highest. It’s a jigsaw puzzle in every job.”

Only Where Needed

The key to solving the puzzle is patching: assembling pieces of plate material for the inked portions on a carrier sheet that is then wrapped around the plate cylinder of the flexo press in lieu of a one-piece plate. This way, no costly plate material for the non-image areas needs to be included in the printing form.

Patching increases the efficiency of flexo prepress, but it can be time consuming, and it requires extreme precision of placement. HYBRID Software streamlines the task with CLOUDFLOW Patchplanner, a web-based layout system that optimizes the arrangement of printed elements in the design file so that they take up the least amount of image space. Then, with the help of an automatic mounting device, the plate elements are reassembled onto a press-ready plastic carrier sheet.

Using CLOUDFLOW Patchplanner to image corrugated flexo plates with limited graphics can save 30% to 70% of plate material in gang runs, says Agness, noting the product’s receipt of a 2020 Technical Innovation Award from the Flexographic Technical Association. (Miraclon’s Kodak FLEXCEL NX Ultra Solution for environmentally sound flexo platemaking also captured a 2020 Technical Innovation Award from the FTA.)

Preaching the Digital Gospel

Corrugated has found its newest beauty treatment in digital printing: liquid-toner and inkjet systems that combine high-end print quality with short-run cost efficiency.

Sutherland’s platform is the HP Scitex 15500 corrugated press, a flatbed device that can print corrugated boards up to 63x126˝ in six colors of UV-curable ink. Since bringing it in about a year and a half ago, says Stanton, the company has converted nearly all of its volume in litho-laminated labels for corrugated into direct-to-board printing on the 15500.

A patched flexographic printing plate assembled with HYBRID Software’s Patchplanner solution on an Optimount automatic plate mounting machine from Flexologic. Image courtesy of HYBRID Software.

Side-by-side comparisons win over even the most resistant customers, notes Manny DeBarros, Sutherland’s VP of sales. “We are preaching digital, for sure.”

Bennett Packaging committed to digital with the two Barberán Jetmaster presses it has installed over the last four years: the first a 66˝ model, and the subsequent one in a 48˝ configuration. These devices, says Bennett, represent “the most significant investments that we have made in order to break into the digital market, along with the expertise and automation software for prepress and setup.” With their help, the company has transitioned the same share of its litho-lam work to digital as has Sutherland.

Innovations like these have helped corrugated production come a long way, but printers and converters still have their work cut out for them if they want to achieve top quality in every job.

“The No. 1 struggle when printing or laminating corrugated sheets is warp,” says Colten Freeze, creative services manager at Bennett Packaging. “The beefier the board, the more problems are amplified versus lower-grade sheets that can be manipulated by gravity, guide rail systems, or vacuum systems.” But, he adds that the mills are experimenting to create boards with improved printing surfaces, particularly for digital direct-to-board applications.

Sutherland Printing obtains board as a member of a consortium that operates two corrugating machines, supplying about one dozen converters. Stanton says that the company also formulates most of its own inks from raw materials it sources from the ink manufacturers.

A Diminishing Difference

Progress in flexographic technology, combined with best practices for flexo printing, has brought corrugated as close as it probably can come to being a high-quality substitute for offset printing on paperboard. In Fry’s opinion, “these new advancements move direct print into the realm where conversions can happen.”

Agness likewise thinks that the print quality of corrugated packaging is now “more than acceptable for purchase by the consumer.”

But in all likelihood, the print quality gap between the two processes will never entirely close. Freeze allows that flexo for corrugated is catching up, “but not quite to the level of offset lithography.” And as Wettersten observes, quality in every method of printing is “highly dependent on the image and the substrate”: a fact of life that means plain brown kraft “is never going to get there” as a practical medium for high-graphic packaging.

Constraints like that won’t stop printers and converters from pushing corrugated printing to its highest level of achievable quality.

DeBarros notes that at Sutherland Packaging, where 50% to 60% of the volume is direct-to-board flexo, printing at 65 lpi looks better than what’s typically seen at that screen ruling because of the care taken with prepress and platemaking. “All that upfront presswork is vital,” he says.

Sutherland Packaging has another asset for corrugated quality in the K7 flexo rotary diecutter, manufactured by KL Carton Machinery, that it acquired two years ago. DeBarros says that this combination device, with some improvements by Sutherland technicians, can print and register three colors on the inside and the outside of a carton in one pass, diecutting the forms as well.

The company also outsources some work to a partner with an EFI Nozomi C18000 LED-inkjet press, which DeBarros calls “by far superior” for high-quality corrugated work.

One-Off, and Off We Go

Digital printing contributes not only to the quality of corrugated production, but also to its efficiency. Freeze points out that because Bennett Packaging’s Barberán Jetmasters print all volumes, large and small, at exactly the same level of quality, it’s possible to show customers exactly what they will get from the devices with a one-off print as the proof. “This solidifies expectations or assumptions that most often have to be made when printing in litho or flexo,” he says.

Bennett cites the advantage of eliminating the waste associated with litho and flexo. Digital, he says, “greatly minimizes the amount of makeready material required to start producing sellable product.”

Given everything that conventional and digital printing processes are capable of, observes Stanton, being in the corrugated business is now “more about educating customers and giving them options” for getting their corrugated jobs done.

As Wettersten sees it, this could shift the traditional attitude of the corrugated producer — “I need volume to liquidate the fixed costs in my business” — to a mindset of greater responsiveness toward shorter runs, quicker turnarounds, and high-quality output. He says that the “minimum bar or threshold” for packaging quality that brands insist on is a standard that most producers know how to meet.

But, not every producer will be flexible enough to move where the market for corrugated packaging is trending. Wettersten says the question then becomes, “does a parallel market develop for someone who is?”