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Under the Hood

Jet Press 750S

With Fujifilm dubbing the Jet Press 750S as the ‘fastest 4 colour B2 digital press’ available, Brian Sims dissects the new and impressive third-generation B2 inkjet machine

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The Fujifilm Jet Press 750 was launched in Brussels, Belgium last year

The fast and the furious

DRUPA 2008 saw Fujifilm give a technology insight by demonstrating the first of a kind, the J Press 720: it was heralded as the first true B2 inkjet press. At the time, inkjet technology had never been upscaled quite so far and the claims this press would be able to match lithographic quality seemed equally as bold as the press itself.

Watching the press produce a finished product at the time, I must admit I was impressed with what I had seen. However, having been involved with major manufacturers and what sometimes sits behind these technology insights, the path to seeing this equipment earning a living on a shop floor can take some time, if they actually make it all.

Fujifilm had the courage of its convictions and confidence in the B2 inkjet printer it revealed in Düsseldorf; in 2011 the Jet Press 720 (Mk I) was commercially available.    

From the outset the Jet Press 720 showed that it was capable of sitting very comfortably between the digital and offset markets, specifically where Fujifilm pitched its product. The press was able to print the offset standards it claimed in 2008 and the ability of not needing make ready times and harnessing the benefits of digital equipment combining neatly into this press.


Roll forward to 2019 and the success of the Jet Press has been significant with over 150 installations worldwide

Roll forward to 2019 and the success of the Jet Press has been significant with over 150 installations worldwide and following one incremental update to design, the Jet Press 720S (Mk II), Fujifilm has now decided to bring a step change to its inkjet printer and have launched the Jet Press 750S.

At the heart of this press, you will still find the well-proven superstructure of a traditional offset lithographic press. You will find four double circumference cylinders with a combination of grippers to physically hold the leading edge of the sheet and a vacuum system to provide additional rigidity of the sheet to ensure the ink droplets can match the pressure imposed lithographic dots.

Fujifilm says that the Jet Press 750S is the ‘fastest 4 colour B2 digital press’ available

As the press bridges digital and lithographic machine designs, it is of no surprise to see the Jet Press 750S has a feeder system virtually the same as a lithographic press. It has a pile hoist and feeder head using vacuum and air separation, a feeder table with furniture, a vacuum belt to shingle feed the paper and sheet register system equally as home on a traditional press.

Returning later to the imaging and drying system, to follow on with the theme of lithographic press design, the post drying cooling station has gripper bars leading to the delivery with everything you would expect to find should you be printing on a Heidelberg, Komori or any other lithographic press.

So, what makes this new generation of Jet Press interesting to lift the covers and see what makes it tick?

The engine room

Firstly Fujifilm rely on its tried and tested anilox roller coating system to lay down a full sheet ultrathin layer of Fujifilm’s Rapid Coagulation Primer (RCP). The purpose of this primer is when the ink droplet hits the sheet, instead of it migrating and ‘growing’ on the sheet, the reaction between water-based ink and primer holds the ink which is why the dot can be reproduced with such accuracy and repeatability matching any offset production.

The engine room of the Jet Press 750S is the new generation of Samba printheads


The engine room of the Jet Press 750S is the new generation of Samba printheads. These printheads have been upgraded and redesigned to increase the jetting frequency from 25 kHz to 33 kHz. This has been done to allow the increase in single sheet pass to 3,600 sheets per hour which is an improvement of 33%. Obviously this increase requires more droplets to match the high paper speed, hence the change in jetting frequency and no loss in dot quality and maintaining a native resolution of 1,200 x 1,200dpi.

All of the above gives assurance the reproduction of the dot is maintained to offset print quality and the gamut of colours and accuracy of reproduction also being paramount. To this extent, the new Samba printheads use VersaDrop technology that allows the size and shape of each droplet to be controlled. By doing this, you can increase the resolution from the Jet Press 750S by the production of four greyscale levels.

The new printheads have a clever system to ensure they stay clean at higher speed by something Fujifilm call Overflow Cleaning. The main issue with inkjet heads is the small particles that start to build up around the outlet of the nozzle. The dried ink starts to – not block the nozzle as such – but initially it either deflects the ink as it is ejected, or it obstructs the ink itself. Both interruptions cause the same outcome, an incomplete dot which means reduced print quality.

What Overflow Cleaning does, is to remove these small dried ink particles by secreting an above production volume of ink which dislodges unwanted ink particle. The action is then reversed before the larger droplet is allowed to leave the nozzle and the wet and dry ink is taken back into the print head. The recirculation of the ink then breaks down the dried ink and hence removes it from the system; very clever.

The inner workings

To finally ensure the Samba heads maintain the highest of quality post imposition the printed substrate passes under the In-Line Sensor system (ILS). The ILS will adjust the inkjet map and how the ink is discharged from the printheads to make up for any discrepancies that have been detected. This automatic nozzle control system ensures the corrections needed are all taking place in real time.

A further change from the Jet Press 720S on the 750S is the change in position and redesign of the closed loop quality control system, ImageConfidence. In the 720S Fujifilm needed a mirror in the design which required periodic maintenance. By removing the mirror the Jet Press 750S not only has increased up time but also the resolution of the ImageConfidence scanning system. This has the functional resolution doubled and now uses a proprietary AI algorithm to ensure each sheet matches the pre-approved image on-the-fly.

Along with the new Samba printheads, Fujifilm now has an updated set of Vividia water based inks. These CMYK colours have been developed to produce the widest range of colours possible with ink grains as small as 0.5 trillionths of a litre in size.  Not only do these inks provide the large colour gamut, they also have excellent drying and ink rub-off quality.

One of the issues any lithographic printer faces is the Pantone range of spot colours normally needs a fifth or sixth unit. Fujifilm’s Vividia inks and its XMF ColorPath system means the Jet Press 750S can print nearly 90% of the 1872 colours within a ?E of 3 or less, matching that of an offset press.

Closing on the principle changes in this new press, the larger sheet size (750 x 532mm is now 750 x 582mm) is dried on a brand new drying system. To cope with the higher press speeds, this new dryer uses both a heated belt and hot air to dry the printed sheet. But considering the environment as any responsible manufacturer now should, the actual power consumption of the dryer is reduced by 23%.


Clearly the new Jet Press 750S is a generation leap from the 2008 release

Clearly the new Jet Press 750S is a generation leap from the 2008 release, and this press truly does match expectation and plants a foot fully in both lithographic and digital camps.



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


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