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FLEXO Magazine : July 2009
Expanded-Gamut Ink Decks: Pinpoint the optimum colors to add to traditional four-color process to maximize the gamut in the areas that most benefit the graphics of the job. Here again you need to find the optimum ink formulation, anilox roll configuration, and mounting tape for each expanded gamut ink deck. This will result in printing clean reverses, minimizing dot bridging and dot gain and maximizing the color gamut on the given substrate. QUESTIONS & ANSWERS You now know the questions, but how do you determine the answers? Once you have determined the print variables to test, you need to develop an optimization test plan. The test plan identifies the print variables to evaluate, the method to evaluate, and the test elements to use to determine which combination is optimal. The type of graphics that will be printed on each print deck (process, line, screen, solid, combination) will determine the test elements needed to properly evaluate the print variables included in the test plan. In addition to the test elements, you may also choose to include sample graphics from the trial job. For your new customer trial job, the team develops the following optimization test plan: For the Specialty Ink Deck: The goal is to print as high a coating weight as possible of the strongest ink formulation possible while still being able to efficiently dry/cure the ink at production speed and hold the graphic detail required by the design. The anilox supplier makes engraving suggestions based on its experience. A banded anilox design with four engravings is created. In addition to the four test engravings, the anilox supplier provides a 1in. to 2in. band on either end of the roll with identical engraving specifications to facilitate press setup (impression settings, inking, etc). The ink supplier suggests two possible formulations of the specialty ink varying the pigment load and dry/cure rate. The plate supplier suggests two possible plate types that will maximize ink transfer while holding up to the abrasive pigment particles in the ink. The test plan includes varying the anilox engraving (four bands), the ink formulation (four formulas), and the plate type (two plates). All other press variables will be held constant including the substrate, dryer temperature, airflow, tension settings, mounting tape, doctor blade angle, etc. Press variables that are not included in the test design will be set at normal operating conditions. The team designs the test form to include a large solid wrapping around the cylinder in each band that includes larger type and line weights in both serif and sans serif fonts, including both positive and reverse type to determine minimum type capability in case type is added using the specialty ink. The primary variables that will be evaluated include: solid ink coverage, pinholes, mottle, and drying capability as well as the ability to achieve the special effect (fluorescent glow, pearlescent shine, or metallic sheen). These variables will be evaluated www. f le xography. org JULY for each combination of anilox engraving, ink formulation and plate type. The optimum combination will be determined based upon this evaluation. For the Expanded Gamut Ink Decks: The anilox supplier suggests possible engravings to minimize dot gain while achieving a strong solid (to maximize the potential gamut). A banded anilox design is created. The ink supplier suggests two different ink strengths that can be used for the expanded gamut inks. Two mounting tapes are evaluated to determine which one will minimize dot gain while achieving the necessary solid ink coverage required by the design. The team designs the test form to include tone scales, a large solid block, minimum positive/ reverse type size test element, two large vignettes (in two different line screens) and the applicable bar code in three 2009 FLEXO 19
Sustainable Spring 2009