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FLEXO Magazine : November 2013
TeChNOLOGIES & TeChNIQUES optimizing Color-gamut With 4-Color Process Density Tonal range, Control Can be Improved by Paul Lancelle Today, we live in a world where exceptional print quality with flexo is no longer considered a “premium”—it is a given expectation of our customers. So, the real chal- lenge lies in providing these expected quality levels by the most cost-efficient and productive means available. Histori- cally, our most common approach in achieving consistency and stability has been with the application of spot colors. This approach, however, does little to contribute to our goals of efficiency and productivity. One of the alternatives related to combining enhanced quality with cost efficiency has been the application of Ex- panded Color Gamut (ECG) printing: A 4-color process com- bined with RGB or OGV (depending on how one prefers to phrase it). It has certainly been demonstrated that, under the right conditions, this can be a very effective direction. We’ve seen more and more end users adopt and mandate this ap- proach. Mark Samworth and Mark Mazur both provided very informative presentations at FTA Forum 2013 that indicated that the use of ECG in flexible packaging may, in fact, be reaching the “tipping point.” An eCg Primer At its basis, the primary benefit derived from the applica- tion of ECG in flexo lies in expanding the gamut through the use of additional colors. Some users have demonstrated a 40 percent to 60 percent increase over a straight 4-color process. It’s been proven that upward of 80 percent to 90 percent of the Pantone formula guide can effectively be replicated with spot color simulation through the use of a 7-color process. And, while that’s a great benefit, it’s a bit of a misconception to think that it begins and ends there. The real advantage to the printer in the application of a 7-color ECG comes from the cost and productivity benefits: • Reduced makeready and changeover times, even a more critical factor these days in trying to remain profitable as run lengths get shorter and shorter • Less ink consumption due to the capability to create recipe color simulation of spot colors with higher line count, lower volume anilox rolls • The capability to “gang” different SKUs on the same web, leading to even greater efficiencies • And the capability to create a “fixed color palette” that, when implemented all the way upstream to the design stage, creates meaningful opportunities for product uni- formity and consistently meeting color expectations Workflow tools have been developed and exist in the mar- ket today that have transformed the complexity of file prepa- ration and color correction for a 7-color process into a much more simplified and highly automated functionality. Proofing and color matching have also taken great strides in the adap- tion of ECG moving past the “tipping point” in flexo. But, with all that said, the fact remains that the applica- tion of ECG isn’t for everyone. The true benefits really can’t be realized without volume. In conversations with several flexible packaging converters over the past couple years on this subject, the response more often than not comes back to something along the lines of: “The whole concept makes perfect sense to me, but what I need is enough volume from one customer or enough customers willing to take the path in order to be able to dedicate one press to it and go from there.” That is a legitimate concern. The “build it and they will come” approach can prove to be a risky proposition. True success with ECG is usually driven from the top down and requires total buy-in by all players involved. A couple of other factors that come into play are that, in flexible packaging where most of the success with ECG has been demonstrated to date, a 10-color press is required in or- der to successfully implement the 7-color process approach. There’s usually a white plate involved and, no matter how dedicated we are to a fixed color palette, there is still going to be the occasional brand color or special effect color that needs to be incorporated into the mix. CoST & beneFiTS With that being the case, realizing the potential benefits from printed gamut extension in flexo need not necessarily require an “all or nothing” approach. Obviously, the concept of spot color simulation through the use of a 4-color process is nothing new in our world. What has historically limited true success with this approach in flexo, however, has been some of the inherent limitations associated with the process itself. Just to name a pair: • Reduced overall tonal range capability as a result of viscous inks • Absorbent or repellant substrates and relief printing plates, in general What has changed in recent years, however, is a number of combined technological advancements that have contributed to overcoming some of these limitations in the flexo reproduc- tion process: • Printing press and anilox engraving technologies • Ink metering and formulations • Process control features • Most notably, advances in prepress and plate technologies These have resulted in the concept of extending the gamut, with 4-color process becoming a viable alternative for some printers. The effects of these combined technologies have resulted in three key factors that provide for optimizing the printable gamut with flexo: • Higher solid ink densities • Extended tonal range capabilities • Improved control, consistency and repeatability in the process Whereas the ECG approach is largely about expanding the gamut through the application of additional colors, the “new look” 4-color process approach is based more on utilizing advancements in existing technologies as a path toward gamut extension. The results of one print trial analysis utilizing some of these advanced prepress and plate technologies demonstrated that, with 4-color process in flexo today, we can exceed the gamut model standard for Specifications for Web Offset Publi- cations (SWOP), provide comparable results to the General Requirements for Applications in Commercial Offset Lithog- raphy (GRACoL) standard and come close to that of even the current European Gravure standard model. These types of results are being achieved through the ap- plication of one or more of a number of advanced prepress and plate technologies: • Laser optics technology and higher resolution output that provide better definition and faithfully replicate more of the original gray levels • Digital flat-top dot technology that reduces or eliminates the negative effect of oxygen inhibition in the UV expo- sure stage 7-COLOR ECG • “Gang” multiple SKUs on the same web, leading to even greater efficiencies • Reduce makeready and changeover times, a critical factor when trying to remain profitable as run lengths are made shorter and shorter • Create a “fixed color palette” that, when implemented throughout, affords meaningful opportunities for product uniformity and consistency in delivering color expectations • Consume less ink due to the ability to create recipe color simulation of spot colors with higher line count, lower volume anilox rolls NEW LOOK 4-COLOR • Exceed SWOP standard gamut model • Comparable results to GRACoL • Advance screening • Enhanced ink transfer • Surface texturization • Three key factors provide for optimizing the printable gamut with flexo: - Higher solid ink densities - Extended tonal range capabilities - Improved control, consistency and repeatability in the process FiRsT OF TWO PaRTs 50 FLeXO NOVEMbEr 2013 www.flexography.org www.flexography.org NOVEMbEr 2013 FLeXO 51