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FLEXO Magazine : July 2012
A simple example follows: If 80 percent of spot color green is overprinted by 40 per- cent of spot color red (red on top of green) then, what is the resulting color on a flexo press? Answer: We don’t know. The underlying science to predict this behavior has been missing. There have been various methods of guessing, and some methods are better than others, but behind all of the ad- vanced color management marketing, we lack a proven color methodology that works reliably. Consider the unique information needed to accurately predict the overprint behavior of two custom spot colors on a given flexo press, with a given anilox, at a given line screen, with food grade inks. To solve this problem requires a method of accurately modeling the process behavior, identifying the significant process variables and then finding a way to gather the necessary data that hopefully does not “break the bank” in the process. FINGERPRINTING—CURE OR DISEASE? Historic color management methods have required mea- suring the behavior of each unique condition of a specific press on the actual substrate (fingerprinting). This method of predicting press behavior works well for CMYK offset on standard paper substrates. However, this process is clearly broken for packaging applications, where the colors in the file are arbitrary, the print rotation on press is non-standardized and the ink formulas change. And, let’s not forget about the interaction of a host of other variables in the production run. Extended gamut press fin- gerprinting is very expensive, unreliable, and often produces useless profiles. To address the needs of packaging, a new approach is required. SOLUTION—MODEL & MEASURE A completely new methodology has been introduced that predicts actual ink behavior, on a specific substrate for each press setup—without the rigors of proprietary, chart-based press fingerprinting. This technology uses groundbreaking process modeling algorithms, coupled with spectral ink mea- surement that analyze the ink pigments within each ink color, as well as the substrate’s colorimetric properties. Within the software, the measured ink and substrate infor- mation is applied to a specific printing process—flexo, offset, gravure. Then some process specific information is added, such as, ink rotation, line screen, dot gain, etc., and the final press condition is simulated without requiring a traditional fin- gerprint. This underlying technology is flexible and does not require rigid spot color charts or proprietary input. A profile could be created with just the solid patches of the spot colors on the substrate, although better results would be achieved if multiple steps (50 percent, 30 percent, 10 percent, etc.) of the spot were measured, improving the end result. Traditional press fingerprinting charts are supported, and the new technology can use existing press characterizations to refine accuracy. The technology also allows the substitution of the substrate within the profile, when ink behavior conditions are similar. In this case, the color values of one substrate can be replaced by the values of another substrate. This avoids the GMG OpenColor is a revolutionary spot color tool for the packaging market that will greatly extend color control and repeatability in this sector. www.flexography.org july 2012 FLEXO 59