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FLEXO Magazine : February 2010
26 FLEXO FEBRUARY 2010 www.flexography.org The final numbers are in after nearly two years of research and analyses on the quality characteristics of Performance Enhancing Cylinders (PEC). This study compared the PEC plating package against conventional printing cylinders and involved both North Carolina A&T and Appalachian State Universities. More than 240 press samples were taken with various operator skill levels ranging from experienced industry pressmen, to educators, to fledgling student pressmen. Both the Nov. and Dec. 2007 issues of FLEXO recorded the planning and initiation of this research effort. The final analyses were completed this past fall and results written in a paper titled, "Performance Enhancing Cylinders versus Con- ventional Plate Cylinders: A Comparative Analysis of Flexo- graphic Print Quality." The information was subsequently presented at "The 2009 International Conference of Graphic Communication Arts and Sciences" in Pan Ciao City, Taiwan, in Nov. 2009. This article will give a brief review of the previously pub- lished materials, an update of research activities, and a sum- mary of results. INTRODUCTION OF THE PROBLEM Banding, also called gear marking, is an age-old problem within the flexographic printing industry. Over the years, there have been as many proposed solutions for banding as there have been causes --- still, the problem persists. Some of the frequently accused culprits of banding include: plate durom- eter, improper cushion tape, over/under impressed cylinders, speed of the press, misaligned drive train, worn or damaged gears, low viscosity of ink, excessive total indicated runout (TIR) of cylinders, die cutter vibration, etc. The reality of the situation is there are usually two or more of the above listed problems combining with a negatively acting synergy that destroys print quality. The diversity of possible contributors of banding makes it nearly impossible to isolate the exact source of the problem. Press operators can sometimes lessen it by eliminating one of the variables, but are often unable to totally eliminate banding. Regardless of the source, the result is a slight difference in the speed of the surface of the plate against the surface of the substrate during the point of impression --- thus an area of slurred dots, resulting in a dark band. Some years ago the advent of servo-driven flexographic presses offered a solution to gear marking for those who could afford them. However, many companies can not afford to upgrade, which leaves the flexographic industry with thousands of geared press- es, still in production, that have not been retro-fitted with servos. They continue to have problems with gear marking and many managers are looking for economical methods of eliminating or greatly reducing the occurrence of the problem. The development of PEC promises to eliminate the occur- rence of banding. This is achieved by creating a flexographic plate cylinder that is cutback to accommodate a .375in. poly coating. This proprietary coating is designed to absorb and dissipate the vibrations within the print system responsible for the slurring image and resulting banding. The flexographic plate is adhered to the poly coated plate cylinder by a .005in. tape --- there is no cushion tape involved in this plating package. The manufacturer claims the Performance Enhancing Cyl- inders (PEC) not only eliminate banding, but also have other key advantages, such as: • Greater operator latitude when setting impression • Decreased make-ready time and increased press speed • Increased tonal range • Reduced dot gain • Ability to Hold tiny reverses open and clean Performance Enhancing Cylinders Results of a Two-Year Study By Dr. E. Dean Gilbert FIGURE 1. Performance Enhancing Cylinders print with less tonal value in- crease than conventional flexographic printing cylinders. TECHNOLOGIES & TECHNIQUES • Press: 7in. Comco Cadet press. • Ink: Cyan water-based ink. • Substrate: Avery-Dennison high-gloss, pressure- sensitive • Press Speeds: 150fpm and 250fpm press speeds. • Trials run by experienced operators, educators and students.