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FLEXO Magazine : July 2009
PLANTS & PROCESSES Q: Q: Q: Q: Q: Q: Steele/Butler: A screened brand color is still managed using the established color standard. Depending on the availability of extra print decks, the color might be split into a line color and a screened color using two print decks. If splitting the color into two decks is not an option, the appropriate line screen is chosen based on the volume of ink required to achieve the color. Q: ment? Breitung/Dietrich: No. We have provided a recommendation but do not require it. As for inter-instrument agreement, manufacturer specs are pretty tight and if an instrument or two instruments are out of spec, we recommend they be sent to the manufacturer for calibration. How many printers do you work with? If a better spectrophotometer is found, how many must be purchased? Are they UV polarized? Chop/LaFonde: We work with 30+ printers/converters for our North American business. We specify two instruments that all qualifi ed vendors must use to ensure instrument agreement. We do not normally specify the use of a UV fi lter on qualifi cation of new color standards. You mentioned “standardizing the background for color measurement.” What standard are you using for that backing? Steele/Butler: Coca-Cola procured and distributed a standardized ceramic white tile to each of the separators, printers and quality labs that are a part of our supply chain. All nonopaque materials are measured over this tile. Should spec-trial data be the only way to communicate color to a vendor to get drawdowns produced for customer approval? Chop/LaFonde: No. Having upfront knowledge of the available pigments/colorants and chemistry of the ink on a standardized substrate, we can establish realistic and achievable standards. A verifi cation of these standards must be done via drawdowns, etc. How might you handle screened brand colors? What is the acceptable tolerance between different substrates for a spot/brand color? Chop/LaFonde: Theoretically we would love this number to be zero, but understanding that this is not real world we do not set an overall ΔE between substrates. We focus more on the ΔE of the hue angle, which we strive for zero. When creating DNA color standards across substrates, the analytical is important but there is a fair amount of subjectivity here when creating cross-substrate standards. Do you prefer to measure color colormetrically or densitometrically? Why? Steele/Butler: Coca-Cola North America’s preference is to measure color colormetrically, so that we can evaluate all aspects of a color and understand what needs to be done to get a particular color closer to the established standard. Do you standardize on a specifi c spectrophotometer? If not, how do you handle inter-instrument disagree- Q: Q: Q: What do you see as the most limiting substrate and/or platform? Breitung/Dietrich: There are many that present their own unique challenges. Low dyne, low surface tension, transparent, shrink and off-white substrates, as well as packaging that require distortions, all fall on the list. How do you prefer to measure dot gain? Steele/Butler: Traditionally, we have measured dot gain using the Murray Davies formula, but more recently, we are evaluating the use of colorimetric dot gain measurement. When you select a printer or printers, do you consider the previous process capabilities of the printer as part of the contracting process? Breitung/Dietrich: Sourcing printers involves many considerations. Cost, quality, existing partnerships, standards compliance, audit approvals and food safety requirements are just a few. Q: Q: Q: Q: What type of qualifi cations do you require when evaluating a printer/converter? Chop/LaFonde: Qualifying new vendors is a fairly involved process that requires RFI information and a minimum of two onsite audits. Spot color standardization is a complex process under any circumstances, whether produced fl exo, offset or gravure. Have you tinkered with the digital printing process? What are its advantages and challenges? Where does it fi t with traditional printing processes? Breitung/Dietrich: Indigo digital presses can run spot colors and can be held to the same tolerance as conventional printing. If spots are built with the standard digital ink set, they are generally within 3.0 ΔE of the target and print with less variance within the run than conventional printing. Since color is vital, how do you see offset quality as a competitor to fl exo quality? Chop/LaFonde: Specifi cally focusing on color, from our experience, fl exo has absolutely no issues achieving the color standard targets. But, in many of the fl exo applications, color control from the beginning of the run to the end of the run is much more challenging then what we experience with offset. Are there printing challenges (color or substrate) not being met by current print technologies? Breitung/Dietrich: Yes, although we are not at liberty to discuss innovation projects we are working on with our supply base. Editor’s Note: As of June 8, Dan Dietrich has accepted the position of vice president, North America with Polywest USA. www. f le xography. org JULY 2009 FLEXO 37
Sustainable Spring 2009