19 July 2018 Digital Printing Technologies

Lettershop takes inkjet to the next level

The Kodak Prosper inkjet press at The Lettershop Group is printing litho quality on offset papers. Digital printing can now match the quality of conventional printing at much higher volumes and does so cost effectively.

The big question for digital colour printing has been when can it replace offset litho printing? For very short runs, below the economic viability window of litho printing, the question has been answered. But this is sufficient only to replace a limited part of print. Twenty-five years after digital printing arrived, it has no more than 20% of the market by value, far less than this by volume.

Digital colour printing has been hampered by its cost, its limited speed and most of all by quality. That litho printing was able to adapt to shorter runs, higher speeds and quality has increased the barrier that digital has had to climb, and personalisation, that great pot of gold at the end of digital print’s rainbow, has not materialised.

Consequently, digital printing has not grown as anticipated. It has proved impossible to achieve the trio of quality, cost and productivity with digital printing. At least until now. Inkjet has been knocking on the door, almost but not quite there. Now the door is opening.

At The Lettershop Group in Leeds a Goss M4000 32pp press towers over a Kodak Prosper 6000C. But it is the Prosper that is running, dropping printed sheets into the delivery at a rate equivalent to a B1 press running at 14,000sph. It is running a paper familiar to the offset press and delivering a quality that is perceptually no different to most litho print.

However, this is no simple drop in replacement for the dark grey web offset beast.TLG has been on a long journey to reach this point, Kodak likewise. The Leeds company, now part of the YM Group, was an independent direct mail operation when it started to mount Kodak inkjet printheads for personalisation on Scheffer special products mailing lines.

In 2008 when Kodak had introduced the Prosper printhead as a mono imprinting unit at that year’s inkjet Drupa, Simon Cooper saw the potential of running it with colour inks.

A small batch of ink was discovered and sent from Dayton to Leeds. Four printheads were rigged above the web on one of the Scheffer line and TLG proved it was possible to print variable content in blank spaces alongside content printed on a web offset machine. Any quality difference was acceptable to the customer. Mail pieces gained an added relevancy to the recipient at a speed and cost that no longer ruled out large print runs.

There are now two Scheffer lines in the factory able to offer this kind of hybrid print, something that has exploited the company’s skills at engineering solutions to production problems. These are lines that split and twist webs, add perforation, glue spots and bring the webs together again to create a single piece mailer that will engage the consumer.

This means that the lines will take a while to makeready and that digital print is an essential part of the process, not a replacement for litho. Inkjet is replacing toner printing.

TLG’s engineering heritage is evident too in the centrepiece of the factory, the Prosper 6000C. This is Kodak’s flagship inkjet press, capable of 300m/minute speed and aimed at high volume, litho substitution print. Given the volume the press is capable of, Kodak is not selling many. It is expensive and most would rather stick with the litho they know than risk a devil they don’t.

But Kodak’s strategy has changed and it no longer aims to sell Prospers in volume. Instead Kodak wants to work on projects where it can address specific needs. A classic example of this, says Kodak’s Graham McLachlan, is Zumbiel Packaging, the first user of the Prosper S, the single-sided version of the machine.

The ink heads are incorporated into a production line for packaging including flexo units either side of the inkjet heads. These can print the static elements of a box, leaving the inkjet to print the variable content; each technology is used on the task that it is best suited to.

“Our inkjet is about high volumes,” McLachlan says. “Many customers do not have that need. The question we have to ask is ‘How much volume can really be migrated from offset?’.

“Only then can you talk about adding value – we can’t build a business case on possibilities. Our technology is not the right choice where companies want to run the press for a few hours then let it stand at rest for a few more hours. It needs to be running.”

Various users attest to this attribute of inkjet technology, something that is not unique to Kodak – the more they run, the happier the heads are and the more consistent the quality. The continuous inkjet technology that Kodak uses is particularly stable in this regard, says McLachlan. It is also very stable in colour.

“It is alway a challenge to achieve a consistent red,” he says, this being a colour that the human eye is particularly sensitive to. “We have checked with one US user over 18 months’ operation and in that time there was a delta E shift of less than 2 in red. That’s big measure of what we are capable of.”

For TLG it means a consistency from first print to last through a reel and from reel to reel and across many months of a campaign. It creates flyers for a major supermarket, tying in a promotion for the opening of a new supermarket producing a flyer including store details and a picture of the store manager.

Previously it would be printing a standard piece of collateral on the heatset press, without the variable elements. Flyers can now be created for each outlet with a selection of offers and products specific to that store. These can run in their tens of thousands on a press without stopping, and when the target switches to another store, the change is instantaneous. This is not personalisation of every sheet, but customisation.

Where the job would otherwise require four or more plate changes on the 32pp web press, it is more cost effective to print on the inkjet press. The cost of eight 16pp plates, the waste associated with start up and time lost while the press is not working, are all eliminated using the digital press. “There are high fixed costs associated with printing litho,” says TLG managing director Simon Cooper. “And print runs are becoming shorter. Customers want more versions.”

They also want a faster response. The marketing community has become used to the speed of setting up and implementing a digital campaign. There is no stomach for waiting the many weeks it can take to implement a print and mail campaign, or a print and door drop campaign which will need to be booked in with Royal Mail weeks in advance.

“With digital, marketers can leave the marketing message until days before the message goes into the mail, with litho everything has to be decided weeks in advance,” says Cooper.

Digital also offers opportunities to consolidate different mailings for different customers into a single mail run, creating economies of scale and discounts that running separated campaigns could not address. Each day the Prosper handles a run of letters for different clients as a single file in this way, everything pre-sorted digitally before printing to obtain the best price for a customer.

The advantages of working digitally are still not about highly targeted, personalised print. Ten years or more on, the data that brands hold and can use to drive a personalised print campaign is not really there. “If we were relying on digital to work like this, we would be hard pushed to drive the volume through the press,” he explains. The volume instead comes from replacing litho: the same work but produced in a better way.

Most with high speed inkjet technology are printing transactional documents on to uncoated papers with limited requirement for quality. Others are printing mono books, again not always the most challenging in terms of print quality. “But we are not in transactional printing, but in marketing where quality has to be litho quality,” Cooper says.

Print also has to be on the same papers that litho presses use. There is a financial benefit to this as specialist inkjet papers carry a substantial premium and are subject to a lengthy order period. It can be difficult to predict how much paper will be needed on the day if that paper has to be order almost three months in advance.

And while inkjet optimised papers can hold the ink on the surface of the paper to deliver a higher perceived quality than on uncoated papers, the coating that the mill applies is different to a standard silk or coated paper. The paper has a similar appearance, but it feels different. If TLG or any printer wants to move work from offset to inkjet, it has to be able to use the same papers.

The answer, in Leeds at least, is to apply an overall coating solution to the paper, creating a barrier to prevent the ink interacting with the paper’s coating, exactly what a mill does to produce an inkjet optimised paper.

But where the mill has to apply a generic finish, TLG can be specific. “The papers designed for inkjet do not suit all the inkjet presses, consequently the results were not as good as preparing and optimising the paper for ourselves,” says Danny Lynan, the former studio manager who has been able to make the inkjet press sing.

He was transferred to the Prosper when the company realised that the only real difference between the workflow to produce an Epson proof and set of plates and the workflow to run the Prosper was one of scale.

The studio manager understands what can and must be done to optimise quality while balanced with being cost effective. Files are optimised for production in the studio, many submitted through TLG’s online portal, and head for the press where colour management is applied to each job during the Ripping stage.

The operator has access to all areas of the Prosper through the monitor, showing the condition of print heads, dryers and position of the job. Stroboscopic lighting shows the job in progress. The Rip itself is capable of processing 100,000 A4 pages in 25 seconds.

TLG designed and built a coating unit that now sits inline with the press. The paper is cleaned, coated and dried before reaching the inkjet heads. Different papers will get different coating weights to deliver the optimum result when printed.

Assessing the level of coating to apply to which paper is a matter of experience and judgement, says Lynan. This approach works so well that Kodak reckons that TLG could sell the technology to other users. Nevertheless it is not a free for all. TLG will steer customers to certain papers that it knows from experience will work. While it can run on with standard offset papers, some restriction is good for sanity and as well as profitability.

The coater is not the only innovation the printer has applied to its Prosper press. There is a reel changing unit to at the start the line, an Amal unit adapted from a reel stand designed for an eight page web press.

Few inkjet web presses yet have automated reel changing, a legacy of the transactional printer’s set up where inkjet has replaced electrophotographic printing rather than the replacing a high speed web offset press where on the fly reel changing is taken for granted.

There is a web cleaner ahead of the coating unit. A buffer controls the tension of the paper going into the inkjet zone. The Prosper design has dryers after each colour is applied. This minimises distortion on the paper caused by application of water based ink to paper. Cameras manage colour consistency and spot the telltale signs of a blocked nozzle.

Kodakhas a camera system ahead of the black print unit which can be instructed to fire a fill in droplet – black is less obvious in a print area than a white streak.

At the end of the press TLG can either re-reel or sheet, using an old Vits sheeter that again has been adapted to run on the inkjet press. There is also space for TLG to wheel in additional units, a perforating drum, embossing and so on that it has built for its other lines.

What the company has is a very effective production line regardless of the technology used to print. Clients are shown Epson proofs against the litho and inkjet samples. On examination with a loupe the different dot structures become apparent, but not to the untrained eye. The challenge is to achieve this sort of quality and response with minimal levels of ink.

McLachlan explains that the digital file can be parsed to calculate exactly how much ink will be used for a job and to create an acute estimated cost. This is never done for offset. A file might be checked to monitor whether the TAC level exceeds the percentage the printer is comfortable with, but the cost of the ink is negligible, saving 5% will not make a material difference. Not so with inkjet.

A job might originally be estimated at €20 a time he says. At this price the customer will walk away. But by chipping away at the ink usage, applying grey component reduction in an intelligent way and adjusting the resolution of what can be printed, the price can come down.

There will be a quality threshold at which point the client will say that too much has been done and the loss of quality is now too great, but the price will be lower. At €11 instead of €20, the job can be approved for inkjet printing.

This is where the repro expertise is brought to bear. “We need to understand how much ink we can take out of a job before losing visual quality,” says McLachlan. “And that visual quality is representative of the litho job in terms of lines per inch.

"We reduce the cost by reducing the amount of ink, then reducing the resolution, increasing the throughput speed and then switching to offset papers. When we get to €11/1,000 the customer can justify the migration cost.”

TLG is in this position. It can talk with customers about projects that were beyond the flexibility of its 32pp offset press. There is the potential in paper wraps for subscription copies of the magazines that are printed elsewhere in the YM Group.

TLG has had the technology to create a paper wrap for many years. The pressure to move away from polywrap is providing a new opportunity for this equipment, coupled with the ability to print in high quality on the envelope, addressing the subscriber with a personal message or tailored ad.

First comes the existing work and the possibilities that this technology opens up for a client like the operator of a chain of corner shops. Currently this customer is using the digital press “like litho”, says Cooper.

“We have converted them to inkjet as a replacement for litho printing. Now we are on a journey: we can start changing pricing; the products stocked in each store with a different offer on the front page.

“In future the franchises will be able to create the content and offers that apply to their store. It’s about taking customers away from the mindset of litho and moving them along on the journey.”

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Simon Cooper

Simon Cooper

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