This is the third article in our series on inkjet in packaging markets, exploring corrugated printing. Although an unlikely market for inkjet at first impression, inkjet presses rapidly gained popularity . This two-part article will look at drivers, technologies and presses available and include some considerations for investing in inkjet presses for corrugated.

More boxes, more corrugated

Packaging is moving into shorter runs, just-in-time production, reduction of stock and increased branding. The containers in which many products are delivered are no exception. Like in many other packaging markets brand owners are looking into digital printing processes to facilitate that shift. Considering the large sizes of box flats, inkjet is the digital print technology of choice.

There are more arguments in favour of inkjet. The simplicity of digital print is streamlining and shortening the production processes. Digital print also offers the opportunity to add variable tracking and identification information in one pass – even security features based on variable data print are possible.

The demand and opportunities are even increasing rapidly, as the Covid-19 pandemic drove up parcel volumes. Germany reported a 17% increase in parcel volumes for 2020 and the Royal Mail even 31% for the UK.  The lockdowns and shopping restrictions also required all kinds of businesses to ship goods. Even smaller companies that had no online ordering options before are forced to ship goods nowadays.

Sometimes corrugated board (or other bulky boards) is used for in-store displays and POS material as well. Here the demand for short runs and high-quality graphics is even more pronounced.

Corrugated printing

Corrugated products are ubiquitous and many of them are printed. The European Federation of Corrugated Board Manufacturers reports that around 70% of all board shipped is printed. The printing processes used remain somewhat under the radar, however.

There are two approaches for printing on corrugated. In the post-print process printing is done on the flat corrugated boards. Traditionally the majority is printed using flexography. This offers a fairly low quality as the image needs to be transferred onto an uneven surface without squishing the flutes. The most recent presses do a much better job in terms of quality, but the output of the majority of flexo presses in use is basic. Some corrugated grades can be printed in offset, but offset is only suitable for thinnest grades of corrugated.

A second option using offset is preprint. In this case the top liner is printed separately and before the corrugating (in which the flute layer and back liner are added) and converting operations. Alternatively, the printed sheet is laminated on top of the board. In pre-print using a smooth, even surface during print allows for much higher quality. However, the process requires two steps, has additional costs and is traditionally more used for long runs.

Inkjet solutions are available for both, pre-print and post-print.

A Challenging substrate

Historically corrugated board is selected for two reasons: cheap & sturdy. The trend towards more branding on boxes is not changing these paradigms entirely, although quality levels are improving somewhat.

This leaves some challenges for inkjet. The performance of inkjet is very substrate dependent. The cheapest and most widespread corrugated boards have a brownish, coarse, and very absorbent surface. Short runs tend to have higher value, so users are more likely to use boards with a white top liner for better quality. Still providing the right ink is challenging, especially since the costs should be low and coverage can be high, which make ink costs an important consideration.

There are more challenges post-print corrugated is posing. Boards are large, requiring wide inkjet arrays. The board surface is often wavy and dusty, which requires some safety distance for the inkjet heads. The bulky board is causing air disturbances, which are affecting print quality as well. Environmental conditions are typically harsh in plants printing corrugated and a printer needs to perform in those - as not all plants are willing to (or able to) create clean areas for an inkjet press.

Fortunately, the quality expectations for printing on boxes are not as high as in graphic arts. While there are post-print inkjet solutions capable of printing a very high quality, even presses with a moderate resolution can achieve results superior to traditional flexo printing.

Preprint can offer a very high quality by using graphic arts grade liner paper. However, as a two-step process preprint is more costly and less flexible.

Types of inkjet presses

Broadly speaking there are three different types of pagewide inkjet corrugated presses. Almost all devices available fall into the post-print high-end segment. All presses can print runs of one and (theoretically) runs of millions, but the automation, productivity and general set-up makes certain types of presses most suitable for certain run length and volume bands.

The first inkjet presses have been installed for a while now and vendors start rolling out their second-generation devices. This testifies that the technology has matured, and users will find a lot more tried and tested devices now.

There are many multi-pass inkjet printers (aka wide format printers) available on the market and most flatbed models allow for printing on corrugated. The slow speed and lack of sheet transport automation make them only suitable for the shortest runs only, as test prints, proofs and mock-ups. They can be a good way to dip a toe into corrugated print, however moving into full production presses will require in different economics, skills and workflow.

Pre-print presses

HP is the only provider of inkjet pre-print presses. Initially HP provided a single sided version of the PageWide T400 as the T400S for linerboard printing. The first installation took place 2014 in Czechia. While the T400 has an impressive web width of 1m (42 inch) the market was looking for an even wider solution. In 2016 HP launched in cooperation with Koenig & Bauer the T1100 with a web width of 2.8 metres (110 inch) and a speed up to 183 metre/min to produce up to 30,000 sqm/hour. That line-up was extended in 2018 with the launch for the six-colour models T1170 and T1190, the latter with a higher production speed of 305 m/min. Obviously the T1100 is not for low volume players. However, large players in corrugated are gearing up and offer more short run print. In 2021 Georgia-Pacific acquired its 3rd HP PageWide T1100-Series press.