Xaar maps a future beyond ink: X-jet

Inkjet has now firmly established itself as a viable, flexible digital print technology in key niche markets, particularly in outdoor signage where screen printing has traditionally dominated.

It has achieved mainstream adoption and recognition in wide and grand format printing, and in coding and marking, but not yet in the broader commercial print markets that remain dominated by offset litho, flexography or, for variable data, the electrophotographic digital processes.

Can inkjet technology become a serious threat to offset and further displace traditional screen and other printing processes? In our opinion the answer to this question is yes, but it won’t happen overnight.

As a printing process, inkjet is still maturing and has a great deal of scope for future development, unlike offset or flexo where future improvements are likely to be incremental.

Here at Xaar we can say that our printhead technology has been a major influence in the development of commercial and industrial inkjet printing to date, and our latest products are about to change the world again!

Where we are today
Today there are three main inkjet technologies:

1. Continuous inkjet is the dominant process in coding and marking and transaction billing.
2. The drop-on-demand (DoD) thermal/Bubble-jet inkjet technology dominates the office and domestic market for office and low-volume photographic printers. This was simultaneously invented by Canon and HP in the late 1970s and cross-licensed to each other.
3. Piezoelectric drop-on-demand inkjets were invented after thermal, with a lot of the pioneering work being carried out by David Paton and Steve Temple at UK-based Cambridge Consultants Limited (CCL) in the early 1980s – the pair went on to become founder directors of Xaar in 1990 and helped to produce the commercialised printheads that sustain the company today. Xaar-licensed technology is also used by OEMs such as Toshiba Tec, Konica Minolta and Seiko (SII Printek Inc).

Production printing
Digital production printing is already out there in the commercial printing industry, mainly in the form of the electrophotographic dry toner-based processes used, for example, by Xerox with its DocuColors, Canon with its imagePRESS and Xeikon with its reelfed single-pass duplex printers.

Today these toner digital printers are occupying niches where their short-run, fast-turnaround and/or variable data abilities are unique, but they can’t compete with offset’s economy of scale for runs above a few hundred or at best a few thousand copies. They certainly can’t match the abilities of flexo or screen process to print economically on a huge range of substrate materials and weights, and they struggle to even approach conventional offset in this regard. For digital printing to revolutionise the industrial print segment it needs to offer flexibility in more than just image reproduction.

Inkjet is the answer: it can print more fluids onto a greater range of substrates than any other conventional or digital process. However the fundamental limitation is that while it’s relatively easy to achieve either high quality or high throughput from inkjet, as soon as you try to get both in the same printer then the costs go through the roof.

We see primary packaging and direct product printing being key adopters of inkjet technology today and for the foreseeable future. Looking out towards the end of this decade we can see many new applications poised to mirror these trends.

There is a range of machines that exists today – from wide and grand format machines and coding and marking machines where Xaar has shipped over 100 million nozzles – to newer industrial strength print machines such as the Agfa M-Press (for screen printers) and PAT’s Varstar (inkjet UV coater/finisher) as well as the Copytrax CD printer. They all deliver value and differentiation in flexibility and productivity from traditional processes, while matching and sometimes exceeding current print quality.

What's needed from inkjet
These are four key aspects that are needed by an industrial strength inkjet:

1. Long Life: High Resolution requires a high number of actuations or drops fired, whether small drop binary or greyscale. It also requires shear mode actuation for longevity.
2. High native resolution (for single-pass): This demands a high nozzle count (ie nozzles per inch) which is enabled by shared wall technology.
3. High print quality: Fine detail through to full coverage, which requires variable-sized droplets (greyscale).
4. Reliability: This includes sustainability and selfrecovery and requires an acoustic firing mode. The combination of shear mode and shared wall patented technologies has allowed Xaar and our licensees to produce piezo-electric heads that deliver industrial-strength life. The key active part within a piezo printhead is the actuator and we’ve operated this beyond 10 million million (1012) actuations with no failure. Duty cycles within normal print are around 20%, so this typically means over four years of life.

Through-Flow allows single-pass
The latest Xaar TF Technology takes significant steps forward towards running inkjet systems reliably for a full shift with minimal maintenance. This looks likely to lead to reliable fixed arrays built to the full width of the printing area, that can run very fast indeed - thousands of square metres per hour. These may even be suitable for very fast wide format printers in future, because they would not need multi-pass printing to compensate for missing jets. Today's fixed arrays are confined to fairly narrow web formats and mainly used for variabledata transaction print.

Xaar's new Hybrid Side Shooter head technology allows Through-Flow (TF) operation. In our original 'End Shooter' heads we triggered an acoustic wave which fired the drop out of the nozzle at the end. The Achilles heel of end shooter designs is that nozzles can fail, either by particulate blocking or because air bubbles form. A failure then requires a wipe/purge maintenance routine to re-prime the nozzles, so you've got to stop the printer.

In the Hybrid Side Shooter (HSS) approach, the ink is flowing right past the back of the nozzle. Two acoustic waves moving through the channel meet in the middle and cause pressure changes which fire a drop out of the side of the channel. Air or particles are moved away from the nozzles, keeping the channel primed and operational. Any nozzles that are lost due to a knock or whatever will quickly self-recover without stopping.

We have just opened a ground-breaking new fac tory in Huntingdon, close to our headquarters in Cambridge, to build these HSS heads. The first model to reach OEMs is the Xaar 1001 head and already printers such as the Nilpeter Caslon digital label imprinter are being commercialised.

The long view
So, that’s the history and present status of inkjets and Xaar’s involvement. So, what’s next for inkjet? Applications for page-wide HSS arrays could include imprinters that can keep up with high speed web offset, flexo or gravure print lines, with higher quality than today’s systems, or complete digital colour presses.

HSS also has the significant advantage of being able to jet what were previously regarded as unstable suspensions and metallics, where normally the particles would settle out and block the nozzle. This is where we move from inkjet to ‘X-jet,’ where X is any fluid, not just ink. In nearly all cases the Xfluid is not an ink, but either a conductive metallised fluid, a polymer or even a human skin cell.

In commercial print HSS is suitable for white and other high-pigment UV-cured inks, or decorative packaging applications such as metallics. Industrial applications could include silver conductive tracks for printed circuits such as RFID antennas, plus emerging technologies such as PLED flexible display screens, flexible circuit boards, smart packaging and labels, 3D objects and medical applications such as skin grafts and, eventually, replacement organs.

In conclusion, whatever the application, there is likely to be an inkjet solution to fit it, either today or in the future. Xaar has already influenced the past, we deliver leading-edge technology in the present and we will continue to change the world in the future!

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