The inkjet advantage

As discussed in Part 2, digital print is key to enabling responsive, flexible and smart print in quantities and on timescales that offset litho can’t match. But within digital print there are further options. Although electrophotographic (toner-based) print is the longer-established technology, its pricing structures and productivity levels means that it’s not always the most cost-effective option for commercial print applications, especially in direct mail or static content materials.

The alternative is inkjet, which typically delivers a significantly lower cost per copy – by as much as a factor of four – and in continuous-feed models is able to compete more effectively against offset for productivity too. As a result, work is starting to move from offset to web inkjet where declining print runs or the requirement for variable content make offset less efficient or practical.

While there has been continued development in offset presses to reduce make-ready time, plates still have to be imaged, processed and mounted and the press run up to colour. Inkjet moves the break-even point between digital and offset from around 500 copies to upwards of 2000, purely on static content jobs, without adding any of the benefits of variable content. When the extra value and effectiveness of versioned or personalised print is also taken into account, these figures rise higher, making an increasingly compelling case for offset replacement.

In a period of spiralling energy costs there is also a case for investing in the most energy-efficient technology wherever possible. As a non-contact printing technology, inkjet has an inherent advantage over both offset and toner which generate heat via friction. Offset litho also has a double transfer stage, first between plate and blanket and then from blanket to paper, while toner requires a high temperature fusing stage. Dryer design in web inkjet has also been subject to considerable progress as the need to support greater coverage on heavier stocks has increased; reducing energy consumption is an important goal in guiding that development.

There are also sheet-fed inkjet presses at SRA3 and B2 sizes, which in speed terms fall between the web machines and the high end of toner production – above about 150 A4 pages per minute – and offer the same cost structure benefits as the continuous-feed models. Although inkjets of all types generally lack the media flexibility of toner presses, a variety of approaches have been pursued to address this.

These include priming of papers, either via a flood coating process that occurs before printing, sometimes inline with the press, or by inkjetting the primer onto the paper in the areas where it’s needed. Another approach, adopted by Ricoh in its Pro VC70000 inkjet press, is to develop inks that will adhere to offset coated paper stocks and thus dispense altogether with any type of priming or additional coating. For many commercial applications, it is not necessary to use stocks of this kind and dedicated inkjet papers will serve, but it is useful to have the flexibility.

This combination of productivity and growing media flexibility means that inkjet can now disrupt the economics of the offset-versus-digital decision. Even where ganging of work on offset has enabled relatively short runs of static content materials to be produced cost-effectively, there is an organisational overhead to managing this process through workflow and separating out the ganged jobs during the finishing stage.

It is also very likely that there will still be some degree of wastage in ganged work, simply through make-ready, even if the ganged jobs are all required in exactly the same quantities. With inkjet there is also no requirement to wait until there is a sufficient number of ganged jobs to fill a B1 sheet, so turnround can be much faster too.

Cost-efficiency and speed of turnaround also benefit the timely production of materials that are time-sensitive or which require frequent updating; as well as periodical publications, this includes textbooks, manuals, directories and catalogues. Although there are digital versions of many of these, they are typically not as easy to work with, don’t offer the same comprehension or retention for readers and are less convenient or entirely impractical in some situations.

The dynamics of inkjet will also open up new applications that were never feasible via existing means, either because of the requirement for variable content, or because of the costs of alternative digital production. Increasing familiarity with data handling, coupled with flexible workflows and platforms developed to facilitate the print-to-digital media connection and tracking capabilities described here will put printers in a good position to develop new applications and encourage the market to adopt them.

Inkjet considerations

In the past there have been issues with client acceptance of inkjet print on grounds of print quality, supported paper types and, particularly, accuracy in reproduction of brand colours as inkjet presses cannot be equipped with special colours in the way that offset ones (and some toner models) can.

However, developments in inkjet-specific papers, printheads, inks and coating technologies, as well as in Digital Front End (DFE) and RIP software have come a long way to address these limitations. Ricoh has gained Fogra Validation Printing System certification for accuracy and consistency in the Pro VC70000 inkjet web press, for example, while the company’s Pro Scanner image processor, which is also available with the Pro VC60000 press, automatically checks every page during production runs for colour consistency with Fogra standards using built-in spectrophotometry.

The trend of improving quality and consistency is only going to continue, driven by growing uptake and competition between suppliers. Inkjet also has an inherent advantage that when dry, it looks and feels more like offset ink than toner does, which will help it gain acceptance from clients used to offset work.

There are also logistical considerations when planning for an inkjet web press installation, particularly in sites that have previously only run sheet-fed presses of whatever type. Foremost amongst these are the practicalities of handling and storing heavy paper rolls, including moving printed rolls from rewinder to finishing line in installations where finishing is not inline. Airflow and extraction also need planning - an experienced partner will be able to advise you on this.