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					     TECHNOLOGIES
     & TECHNIqUES




                                    Performance
                                 Enhancing cylinders
                                   Results of a Two-year Study
                                                            By Dr. E. Dean Gilbert




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

26           fLEXO            FEBRUARy             2010       w w w. f l e x o g r a p h y. o r g
                                                                                                              TECHNOLOGIES
                                                                                                              & TECHNIqUES
  • Improved consistency due to lack of                A team of experts, which included
    cushion breakdown                               representatives from ink, plate and
  • Extended life of digital plates                 anilox roll suppliers, developed a test
                                                    image that would challenge the most
   While numerous schools and compa-
                                                    experienced flexographic pressmen.
nies have tested the PEC product, no one
                                                    The image consisted of gradients, and
has completed a comparative analysis
                                                    large screened areas alongside several
between conventional plate cylinders
                                                    repeating bands of solid print. Also, thin
with .015in. cushion tape and PEC cylin-
                                                    reverse type was added to the mix to
ders with .005in. non-cushion mounting
                                                    increase the challenge. Digitally imaged,
tape. This researcher saw an opportunity
                                                    solvent-washed, 50-durometer plates
to develop a research methodology that
                                                    were produced from this image.               Dr. E. Dean Gilbert presenting at National Taiwan
would provide the flexographic industry                                                          University of Arts, Pan Ciao City, Taiwan
                                                       Samples for the study were printed
with an unbiased analysis of the quality
                                                    on a 7in. Comco Cadet press, using
improvement claims.
   This study should be of interest to any
manager, operator, researcher, student
or educator who works in narrow-web
flexography and has experienced gear
marking or banding.




FigurE 2. Performance Enhancing Cylinders print
with more print contrast than conventional flexo-
graphic printing cylinders.




FigurE 3. Performance Enhancing Cylinders print
with a larger tonal range than with conventional
flexographic printing cylinders.



METHOdOLOgy
   This study was designed to provide
comparative samples of a test image
printed with both conventional plate
cylinders and with PEC. A banded roll
test was performed to optimize for each
cylinder set-up. Once the optimal anilox
rolls for both cylinders were determined,
appropriate rolls were ordered for both
processes. This optimization process
ensured both plating set-ups were
performing at the highest possible level
and eliminated the possibility of testing
both cylinders under conditions that
favored one.


                                                    w w w. f l e x o g r a p h y. o r g   FEBRUARy             2010            fLEXO                 29
     TECHNOLOGIES
     & TECHNIqUES
     a cyan water-based ink, on an Avery-Dennison high-gloss,
     pressure-sensitive substrate. Press samples were taken at
     150fpm and 250fpm press speeds.
        Print quality was compared using dot gain, print contrast
     and tonal range as measured from the samples. A special
     target was designed to measure banding frequency and
     amplitude. Pictures of print samples and enlargements of dot
     reproduction were taken and analyzed.
        This study is a quasi-experimental design and the following
     research questions were to be answered:
        1. Do Performance Enhancing Cylinders print with less dot
            gain than conventional flexographic printing cylinders?
        2. Do Performance Enhancing Cylinders print with more
                                                                                      FigurE 4. Performance Enhancing Cylinders print with fewer occurrences of
            print contrast than conventional flexographic printing                    visible banding than conventional flexographic printing cylinders.
            cylinders?
        3. Do Performance Enhancing Cylinders print with larger
            tonal range than conventional flexographic printing
            cylinders?
        4. Do Performance Enhancing Cylinders print with fewer
            occurrences of visible banding than conventional flexo-
            graphic printing cylinders?
        5. Do Performance Enhancing Cylinders print solid 30
            percent screens with a lower amplitude of variation than
            conventional flexographic printing cylinders?

     rEsuLTs And cOncLusiOns
        Research Hypothesis 1: Performance Enhancing Cylinders
     print with less tonal value increase than conventional flexo-                    FigurE 5. Performance Enhancing Cylinders print solid 30 percent
     graphic printing cylinders.                                                      screens with a lower amplitude of variation than conventional flexo-
                                                                                      graphic printing cylinders
        Hypothesis 1 sought to provide evidence that performance
     enhancing cylinders would print with less TVI than a conven-
     tional flexographic printing cylinder configuration. As Figure                      Research Hypothesis 3: Performance Enhancing Cylinders
     1 indicates, the research did provide evidence of significant                    print with a larger tonal range than with conventional flexo-
     reduction in TVI when using PEC cylinders. Even more impor-                      graphic printing cylinders.
     tant, it was also noted that data showed that the TVI was very                      The objective of Hypothesis 3 sought to establish that
     consistent, which is an indicator of predictability.                             performance enhancing cylinders would print with a greater
        Research Hypothesis 2: Performance Enhancing Cylinders                        tonal range than the conventional flexographic printing cylin-
     print with more print contrast than conventional flexographic                    der package.
     printing cylinders.                                                                 The tonal range graphic is surprising as it shows the PEC
        Hypothesis 2 sought to establish that performance enhanc-                     package to provide significantly less tonal range than the
     ing cylinders would print with a greater print contrast than                     conventional plating system. This could be attributed to the
     the conventional flexographic printing cylinder package. The                     press used in all research samples, the Comco Cadet. While
     results for this research question were interesting because,                     the Cadet is a great press, it does not allow the operator to re-
     while PEC did have slightly higher print contrast over con-                      lease the anilox-to-plate pressure independently of the plate-
     ventional plating, the difference was not great enough to be                     to-substrate pressure. So, with PEC plates on the Comco
     significant (Figure 2).                                                          press, when you crank up the impression (a necessary proce-
                                                                                      dure with PEC) you also increase the anilox-to-plate pressure
                                                                                      far beyond necessary levels. This may cause a reduction of
                                                                                      tonal range which would not occur with other press types.
                                                                                         Research Hypothesis 4: Performance Enhancing Cylinders
                                                                                      print with fewer occurrences of visible banding than conven-
                                                                                      tional flexographic printing cylinders.
                                                                                         Hypothesis 4 sought to establish that performance enhanc-
                                                                                      ing cylinders would print with fewer occurrences of visible
                                                                                      banding than the conventional flexographic printing cylinder
                                                                                      package. The visual banding graphic in Figure 4 indicates
                                                                                      the tremendous reduction in the occurance of banding when
                                                                                      using the PEC plating package: almost non-existant.
     Dr. Mengtsung Ike Tai, National Taiwan University of Arts and Dr. XiaoXia Wan,      Research Hypothesis 5: Performance Enhancing Cylinders
     Wuhan University, Peoples Republic of China, serve as panelist and discuss the   print solid 30 percent screens with a lower amplitude of varia-
     quality aspects of PEC cylinders and how it may affect the flexographic indus-   tion than conventional flexographic printing cylinders.
     try in their respective countries.                                                  Hypothesis 5 sought to provide evidence that performance
                                                                                      enhancing cylinders would print areas of uniform 30 percent

30            fLEXO                FEBRUARy                 2010          w w w. f l e x o g r a p h y. o r g
     TECHNOLOGIES
     & TECHNIqUES
                                                                                            .5%
                                                                          100%


                                                                          99%

                                                                          98%


                                                                          97%


                                                                          96%


                                                                          95%

                                                                          94%


                                                                          93%


                                                                          92%

                                                                          91%


                                                                          90%


                                                                          80%


                                                                          75%

                                                                          70%


                                                                          60%


                                                                          50%


                                                                          40%

                                                                          30%


                                                                          25%


                                                                          20%


                                                                          10%


                                                                          8%


                                                                          6%

                                                                          5%


                                                                          4%


                                                                          3%


                                                                          2%

                                                                          1%


                                                                          .5%              100%




                                    The test image.


     screened tints with lower amplitude of variation between the low-    combined with further research on a press with independent
     est densitometer reading and the highest densitometer reading        anilox to plate impression control, sounds like a research op-
     than the conventional flexographic printing cylinder package.        portunity for some young flexographer! n
         PEC plating system removed almost all visible banding, but
     when banding did occur the variation in density between the
     bands was less than half that recorded from the conventional         ABOUT THE AUTHOR: Dr. E. Dean Gilbert is an associate
     plate cylinders.                                                     professor in the Department of Graphic Communication at
         While there are many more variables that could be                Appalachian State University. He has some 30 years of teach-
     researched concerning the PEC quality enhancements, it               ing experience at the college level. Gilbert has expertise in a
     seems obvious from this research that there are significant          wide range of graphic communication subjects, though his
     quality improvements in most of the areas tested. And, as            research and publishing interest are in packaging, flexogra-
     indicated above, PEC performance would possibly be greater           phy, and variable data printing. He holds a Bachelor’s and
     if tested on different press types.                                  Master’s degree from Appalachian State University and the
         The manufacturer has introduced a higher durometer               Ed.D. degree from Clemson University.
     coating during the time this research project was under-               Performance Enhancing Cylinders (PEC) are a patented
     taken. It claims this product will deliver the same results on       product exclusively available from Nu Tech Coatings,
     un-supported film, and other high hold out substrates, as            Johnson City, TN. For more information, contact Jim Wyman at
     their standard product delivers on paper. This potential study,      770-655-2649, jim.wyman@nutechcoatings.com.


32           fLEXO            FEBRUARy                2010    w w w. f l e x o g r a p h y. o r g

				
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