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Under the Hood

Truepress Jet520HD

Brian Sims uncovers the powers of inkjet, and more specifically the Screen Truepress Jet520HD, as it tries to break into the traditional lithographic sectors

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The Truepress Jet520HD from Screen has been developed over a number of years since the initial launch of the 520

A whole different game

There are often boundaries that prevent the jumps in progress technology promises. How often have you heard, if we only could…’ meaning that if you have the answer to the imponderable technical issue, we can take yet another large step forward.

That has been the challenge facing Screen and other manufacturers of inkjet equipment seeking to break into the traditional lithographic sectors.

Inkjet technology has been around tapping on the door of lithographic markets since 2006 when Screen launched the Truepress Jet520. Over the intervening years, inkjet markets have found themselves hemmed in a little by the constraints of both ink coverage and the fact it was only possible to effectively print on either uncoated stock or invest heavily in having to pre-treat papers.

The Truepress Jet520HD in Screen’s showroom

There is a large market for mono or low ink coverage on uncoated stock, but companies like Screen eyed the traditional markets that ten years ago, were the sole preserve of litho printers.

There is a large market for mono or low ink coverage on uncoated stock but companies like Screen eyed the traditional markets

So, what did Screen do to show it was able to match the colour depth and volume of production but at a cost and level of practicality needed to break through?

It was able to develop a new series of water-based inks it brands as SC and develop the technology of the inkjet heads to be able to print on standard coated lithographic papers. This means you can call off a normal reel of paper and without any treatment of base applications and print directly on it.

There are a series of additives that have been formulated for the SC inks that makes it possible to print on coated stock, but the printheads also need to adapt to the ink and the changes to these allows for maximum advantage to be taken to allow for coated stock production. Screen has also relied heavily on its expertise with the use of Frequency Modulated (FM-stochastic) screening and the unique dot formation from their heads.

Printing on standard litho stocks was only one half of the problem; the second was the resolution and the volume of colour that is required to compete.

The Truepress Jet520HD can print at 1,200 x 1,200 dpi which means the press can produce precise 0.1pt lines and 2pt characters. Printing to this fine level of detail has traditionally been the Achilles Heel of inkjet printers, but clearly Screen has resolved this problem. This has been accomplished by the use of clever technology in the printhead, avoiding blocked nozzles, but also controlling the actual ink droplets to an amazingly small two picolitres.

Printing to this fine level of detail has traditionally been the Achilles Heel of inkjet printers, but clearly Screen has resolved this problem

The ink volumes needed to compete with lithographic presses are large, and you need to provide a large colour gamut too.

The new SC inks easily cover the range needed and in fact exceed that possible with lithographic inks.

They also have the water, rub, heat, light and chemical resistance of normal inks.

A dash of colour

The Truepress Jet520HD comes with four process colours as standard, but has the option for two special colours. The printheads themselves come with patented equipment called Smart printhead control. This device is advised from the data controller that a forth coming colour is not needed and shutters it off with a cap reducing the power needed and improve the efficiency of it.

Pouring ink on a sheet is one thing, but pouring it on accurately is a whole different game. The Truepress Jet520HD comes with a built in quality control scanner. This device scans and regularly performs checks on the output from the inkjet heads which can be susceptible to changes across the vast number of individual nozzles. If required, an option on this press, JetInspection is a specialised unit that is capable of inspecting the whole sheet in real time and make corrections to the workflow dramatically reducing the time on correcting copy or colour.

Finally to make sure the data and print is placed in the optimal position on the paper, Dynamic Nozzle Shift works with the transport system to avoid web wander and other paper position issues. Wrapped in with all the other gadgets and software, you can easily see why Screen feel it has a worthy contender to take on the lithographic market.

Volume and colour output are two sound reasons for Screen to feel it can enter this arena, but it has another string to its bow.

Market information shows that with the increase in impressions per month, as you head past the 25 million impressions mark, the equipment costs drop to less than a quarter of the entry level of five million impressions.

With paper costs actually increasing across this range, the financial benefits of the Screen equipment start to become very interesting indeed as the machine costs become of a very small part of the whole. Basically the more you print, the cheaper it becomes to own a Truepress Jet520HD. If you own one and can now print the quality and volume needed, your costs could start to tumble significantly.

Perfect performance

So what else comes in the press that makes this performance possible?

There are a number of pieces of equipment to ensure excellent copy at high speed. The press comes with a drying system consisting of heated rollers and air heating units configured to dry the SC inks at optimum rates. For more complex and demanding substrates from 40 to 250gsm, the Truepress Jet520HD can be supplied with an optional drying unit.

The drying system of the Jet520HD

To ensure the web is ready for the second side printing, there is a cooling roller between both halves of the press ensures the paper is fully normalised prior to printing for the second time.

All this hardware would be useless unless it was supported by a robust workflow system. In this case the system used is EQUIOUS v3. This powerful piece of software can process massive amounts of data in seconds making sure the press can print individual copy at up to 150m/min.

EQUIOUS can ensure the screening of image is optimised and colour profiles are also processed and applied to suit whatever production is needed. Tied in with JetInspection, maximum performance comes as standard. 

Obviously the press will find it challenging to compete in wider format web markets, but the ability to produce to the quality previously the sole domain of the lithographic press puts the Truepress Jet520HD is a very good position to flex its muscles and show the world what it can do and where it can clearly compete.

Brian Sims principal consultant, Metis Print Consultancy, www.metis-uk.eu

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