These were taken up for digital processes, especially inkjets, but adoption has only been sporadic for conventional, ‘analogue’ print processes. But today we are on the verge of easily accessible extended colour gamut (ECG) print for offset litho and flexography. 

We’ve spoken to two of the press makers that are making a particular push for each process, Bobst in flexography and Heidelberg in sheetfed litho. Both have adopted seven-colour process ink sets of CMYK plus green, orange and violet (or optionally Reflex Blue from Bobst). Using the same colour set for nearly every job, rather than swapping spot inks in and out, include reduced washup times, less ink waste and faster makereadies. Interestingly both companies also say that a big impetus for developing ECG has been the need to match digital inkjet presses in future. 

Federico D’Annunzio, Bobst’s strategic products and marketing director for the flexible materials business unit, explains: “Most digital inkjet presses are using ECG because they cannot print spot colours. In the future, the colour space is going to be ECG, because if you produce a short run or a customised run with digital, then you cannot oblige the brand owner to make a totally different colour for a totally different analogue process, in terms of a workflow and quality checks.”

Two into one

Pantone spot inks are solid, ECG inks are transparent, he points out. “The level of measurement, the sensors used to make the measurement, every single detail is different and they are not compatible. In the future these two colour spaces must somehow go to only one colour space, which is going to become the standard of the graphic industry.”

Extending gamuts by using standard sets of process colours is called ‘fixed-palette printing’. This is especially relevant to labels and packaging where special brand colours are common, but previously the advantages of fixed palettes instead of spot colours was outweighed by disadvantages that could be summed up as ‘too fiddly’.

Now new halftone screens, closed-loop colour and automation technologies, and, in Bobst’s case, new anilox roller technologies too, are why ECG is now practical and accessible without huge operator effort, Heidelberg and Bobst claim. 

Bobst’s ECG efforts are the result of a multi-vendor development alliance called Revo Digital Flexography. Apart from Bobst this includes Esko (pre-press workflows), DuPont (flexo plates), X-Rite (colour measurement instruments), AVT (verifying job consistency to show to customers), Apex International (anilox rollers) and Flint Group (inks). The ‘Digital Flexo’ tag refers to digital control of all aspects of the printing for colour and quality consistency, and validation data to customers

 “We started Revo just after LabelExpo 2013 but before that we had to convince people,” says D’Annunzio. “Years earlier there was Opaltone, which didn’t have a lot of success. And before that there was Hexachrome, also not having a lot of success. The concept is good but Opaltone and Hexachrome were not really end-to-end print practices. 

“So we got together the players in the flexo industry and we made sure that nobody was saying ‘this is your problem, this not our problem’. We worked together and everybody put on the table their R&D and research skills, and their marketing skills.

“Now we have several Revo customers who have adopted the process and they are very happy and getting a lot of profitability out of it. At the same time the perception is growing in the label industry and also in flexible packaging.”

Flexo success

Bobst has implemented Revo-derived ECG on its inline M5 flexo presses (for narrow width labels) and its M6 mid-web flexible packaging presses, which use UV-cured inks. These are built by Bobst Firenze in Italy and feature automatic on-the-fly job plate cylinder changeovers, without stopping the press. “With what we call digital flexo automation, you get instant changeovers and low waste comparable with a digital press,” says D’Annunzio. 

The new 20Seven central impression cylinder flexo press built by Bobst Bielefeld in Germany was also designed from the start to use the Revo systems. This uses water- and solvent-based inks. The separate THQ FlexoCloud project from Bobst Lyon uses wide-gamut CMYK inks and special Graphilabel-produced plates for sheetfed corrugated print. 

D’Annunzio says that consistent quality is as much a benefit as the time and cost savings. A lot of this is down to newly developed anilox rollers together with a high speed, low turbulence ink feed that Bobst calls smartFlo. “We developed, with Apex, systems which means all the anilox rollers give the same quantity of ink. Anilox rollers used to give 5% or 10% difference between each roller. Now you get a maximum 1% difference. We can get perfectly consistent inking and today’s plates are also now much more forgiving, with the new screening technologies.”

Heidelberg’s ECG equivalent for its offset presses is all its own work, which it calls Prinect Multicolor. This combines an all-Heidelberg workflow from pre-press Pantone or LAB value conversion and new hybrid AM/FM screening within its Prinect workflows, with a seven-colour ink set sold under Heidelberg’s Safira label, plus the closed-loop colour consistency and automation of the Inpress controls for its current presses. It can match 95% of Pantone colours, Heidelberg claims.

“We’ve been working with this since about 2014,” says Matt Rockley, marketing and product executive for sheetfed B1 & B2. “The main customer base we’re focusing on has been the packaging market, more notably the pharmaceutical market.” These printers may use anything between two and five or six colours, with different spot colours for each job, he says. “The problem is that roughly 35%-40% of their manned working hours are spent washing the machine up to change from colour to colour. Typically, it’s a third making ready, a third washing up and only a third printing.

“What we found by putting this system into those pharma printers is that they cut out the washup time almost immediately, then makereadies are halved in time because the complexity has been removed.” There will still be some need for spot colours, he says, but about 90% of jobs can be handled by Multicolor. 

Efficiency savings apart, Rockley says that like Bobst, another motivation for the ECG process inks is for compatibility with jobs produced on digital presses. In particular Heidelberg’s own Primefire B1 inkjet press, for carton work, uses the same seven process colours (CMYKGOV) plus white, as does the Labelfire 340 inkjet label press from Heidelberg subsidiary Gallus. “So with Multicolor we’re offering conventional litho companies the opportunity to have an early adoption into digital workflows in terms of colour reproduction.”

The Multicolor system is particularly suited to Heidelberg’s Speedmaster Anicolor presses, available in B2 and B3 formats, he says. Anicolor uses keyless anilox inking rollers instead of conventional roller chains, so it shares much the same advantages of closed-loop responsiveness and consistency as the Bobst flexo systems. 

“We are selling B2 Anicolors with eight units, with specials such as golds, metallics or white on the first or the last unit,” says Rockley. “That’s something that digital has not been able to do at a price or quality you’d want. If you have a colour that is unachievable in Multicolor, on an eight-colour press we can drop it in as a spot and still not exceed the 20 minute makeready. It’s brilliant, it’s making a litho machine digital!”

Multicolor is also available for larger Speedmaster XL 105 and XL 106 presses, commonly used for carton work. Rockley says there is commercial interest too, pointing to Orchard Press in Tewkesbury which is using Multicolor with its 10-unit Heidelberg Speedmaster XL 106 for its commercial seven-colour offering that it calls Rainbow. 

Screen time

Halftone screening plays a big part in both the Revo and Heidelberg systems. In the 1990s the original concepts for six- and seven-colour sets led to the development by pre-press developers of frequency modulated (FM) screening, with semi-random dot patterns that don’t cause moiré. These have since been refined. 

Heidelberg uses AM screens for CMYK and FM for GOV. They are generated by the Prinect Screening Editor module and are unique to Heidelberg, Rockley says. The Screening Editor can also predict the accuracy of the colour match from the customer file. 

Bobst has now adopted a new type of screen, called Digitally Modulated Screening (DMS) by its developer, Hamillroad Software of Cambridge. The flexo screening version is called Bellissima and has just won the 2018 Technical Innovation Award from the Flexographic Technical Association. Hamillroad’s Screening Raster Box system takes unscreened output from a pre-press system (typically Esko), rips it, then generates DMS screens to send to a flexo platesetter (such as the Esko CDI series). It creates screens equivalent to 350-450lpi, which is going some for flexo. 

D’Annunzio says in summary that the quality and efficiency gains are only part of the reason for the revival of interest in ECG. “In the past ECG needed top flexo operators who were the masters of the printing machine. Now it’s much more easy. You could use ECG five years ago and get fantastic printing. 

“Now what we have achieved is absolute consistency and repeatability but without special skills needed. The operators don’t need to worry about achieving quality, now they can concentrate on productivity.”