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FLEXO Magazine : January 2014
TECHNOLOGIES & TECHNIQUES Optimizing The Flexo Color Gamut Process Control Remains Key By Paul Lancelle In outlining the process control parameters involved in optimizing the color gamut for flexo print reproduction, it was stated in Part 1 of this series that “the path forward involves the commitment to a stringent process control plan... from prepress and proofing, through platemaking and on to print reproduction. ” In practice, however, the path is actually reversed. True success with process control implementation begins at the press and is applied downstream from there. The same methodology applies in the determination of the appropriate print standard or specification that a particular printer may choose to adhere to. Without a solid under- standing of the capabilities achievable from a set of print conditions, the entire process can easily evolve into a “tail chasing the dog” scenario. STANDARDIZATION What makes the determination and application of a general “ flexo print standard” so challenging is the wide and varying range of print conditions that exist within the market segment. Varying press formats, substrates and ink systems all contrib- ute significantly to achievable process print gamut capability. Therefore, the age old mantra of benchmarking and character- ization from a given set of print conditions, with optimization as an ongoing goal, remains as the basis in laying the foundation for any successful process control program. Arguably, the most critical keys to establishing color conformity and consistency in flexo remain in the choice of ink system and choice/condition of anilox rolls. Determining the “best” choice of ink system in optimizing the process color gamut, whether through the use of a 4-color process or expanded color gamut (ECG), is not an arbitrary decision. It must primarily be based on properties required for end use application, followed by what produces the largest gamut volume under the given set of print conditions. Maintaining ink WHAT CAN BE AUTOMATED? • Ink viscosity and pH • Impression and registration • Anilox cell depth and condition • Film surface treatment and tension • Color variance throughout a run Ink pigment selection plays a critical role in determining achievable gamut volume under a given set of print conditions. This graph illustrates the printable color gamut achieved using FIRST recommended process ink pigments. (Photo credit: FIRST 4.1) SECOND OF TWO PARTS www.flexography.org JANUARY 2014 FLEXO 55 Figure 4.8 YELLOW 14 RED 57:1 BLUE 15 RED O/P GREEN O/P BLUE O/P