Digital reel printing: Will commercial printers be seduced?

While waiting for drupa and its wave of innovations, the editorial team of Caractère magazine takes stock of this technology primarily based on inkjet printing. It has been said that sheet-fed offset printers would never transition to reel printing. However, today, digital reel printing chains are becoming increasingly enticing. drupa is expected to once again be the global stage for innovations. Previously limited to specific market segments, such as transactional or monochrome book printing, inkjet reel printing, accompanied by associated finishing systems, is opening new doors. Print quality has significantly improved in recent years among numerous manufacturers. The range of papers usable on these systems has also expanded. As a result, inkjet reel printing has access to a much wider range of applications. While transactional and direct marketing prints are declining due to the digitization of administrative documents, invoices, and promotional communications by major retail brands, inkjet reel printing is finding new opportunities in color book printing as well as in commercial printing, particularly in web-to-print.

In areas such as photo albums, web-to-print, or newspaper printing, digital reel printing is increasingly seen as the right solution, whether to replace offset with a more flexible and cost-effective process or to surpass sheet-fed digital presses whose productivity is no longer sufficient. This trend has been growing stronger over the past three years. On average, an inkjet reel press produces 160 million A4 equivalents per year, whereas a sheet-fed press produces an average of 60 million. In short, while it was once anticipated that offset presses in the 74 format could be pushed aside by sheet-fed digital printing in the B2 format - following the trend seen in the 52 format, inkjet reel printing now seems better positioned as an alternative to offset printing.

Achieving successful inkjet printing requires paper preparation. In simple terms, it involves creating roughness on the paper surface to facilitate ink adhesion. This is particularly true when printing on coated papers, as now permitted by reel presses. To allow printers to work with the same papers as in offset printing, digital press manufacturers offer the application of a primer before printing. Several formulas are possible. With its ColorGrip technology, accompanying the ProStream 1000 presses, Canon applies primer to the entire page surface. HP adopts a similar approach, depositing a droplet of primer where an ink droplet will be placed. By limiting the primer to the printed areas of the page, they aim to reduce consumable consumption and avoid matting a glossy paper.

An alternative is to use inkjet-treated paper (approximately 10% more expensive than regular paper), which already incorporates the primer. With Ricoh, the primer is optional. Available on the VC70000e, this option optimizes print quality through the application of full-surface duplex priming. Screen, on the other hand, integrates the primer directly into the inks, eliminating the need for separate application. In almost all cases, with or without inkjet-treated paper, there is some form of primer in the printing process. Printers will be able to form their own opinions by visiting various booths at the upcoming drupa exhibition. 

Beyond media, printers interested in conducting a comparative study should also consider the inkjet printheads used in reel digital presses. Here, two schools of thought exist. The majority of manufacturers have opted for piezoelectric heads, where the ejection of ink droplets is triggered mechanically. HP, however, stands as an outsider with thermal heads. Here, the ejection of ink droplets is caused by an increase in temperature. The main difference is that HP considers thermal heads as consumables. The heads are said to be changed every 100 to 300 liters on average, meaning two to three head replacements per week. In contrast, piezoelectric heads are changed much less frequently but require intervention. However, they are more expensive. In terms of budget, though, the costs reportedly balance out. It remains to be seen whether drupa will mark the entry of new players or the arrival of groundbreaking technology, opening up new possibilities for finishing system manufacturers, who will also showcase their latest innovations at drupa 2024.

Finishing is an area that deserves particular attention when it comes to reel printing. Each printer has their own solution. Several levels of integration are possible to cater to printers with different approaches to automating the production chain. In the case of offline finishing, operations take place on a separate chain from printing - or even on multiple separate elements corresponding to different finishing stages. The equipment connected to the press typically includes an unwinder at the input - optionally with a media mixer to supply the press from two reels - and a rewinder at the output, capable of creating rolls of a given diameter and transitioning to a new reel without interrupting the flow. The printed reels are then transported to a separate finishing line. This approach allows the digital press to operate at its nominal speed without downtime.

The most common online finishing includes the steps required to produce either mail-ready transactional documents or books and catalogs before binding. Such a configuration generally includes a buffer at the press's output, allowing for a certain length of printed web to accumulate, absorbing the few seconds of downtime required for the cutter to operate. This is followed by a slitter for longitudinal cutting of the printed web, a cutter for page-size cutting, and a stacker for stacking the pages in the correct order. The ready-to-bind book blocks are then conveyed away. Additionally, folders can be integrated at the end of the line for cross-folding. For transactional printing, the press directly feeds a dynamic puncher that micro-perforates the web for accordion folding or detachable coupons. Lateral punching (binder holes) is also possible. If necessary, the web passes through a buffer, cutter, and folder. Most configurations stop at producing documents ready for binding, possibly with pre-gluing. "In general, printers prefer to perform the remaining operations on offline equipment, as the speed differences between book block production cycles and binding operations can vary," explained a spokesperson from Hunkeler. Nevertheless, the manufacturer offers a solution to connect their book block or signature production systems with partner finishing systems through a conveyor. "For printers who wish, we can integrate a saddle stitcher online, allowing signatures to be accumulated on a saddle and stitched together. This solution is interesting for brochures or magazines. We can also integrate a binder for bookbinding," explained a spokesperson from Hunkeler. Lastly, it should be mentioned that automated production lines can continue beyond binding, with a robot handling palletizing of the printed works. The wrapped pallets then exit the line, ready for delivery.