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FLEXO Magazine : August 2014
• ere were no web breaks because of an extremely hot UV housing • Printing on shrink lm was possible, which has never done before • Total yield improvement rose 4 percent In spite of the many (apparent) advantages of LED UV, there are many questions that still remain, some of which include actually testing the LED UV product to verify that the conference proceedings were accu- rate. Testing needs to be done in order to display unbiased results for the industry's disposal. It is a very new technology that is not used in the graphic communication industry simply because mercury vapor ultraviolet light is an industry standard. e following analysis of hard data shows the exographic industry comparison between the current industry standard, mercury vapor UV and LED UV. RESEARCH METHODS & PROCEDURES e purpose of this study was to provide data related to the di er- ences between conventional UV exographic ink curing and LED UV exographic ink curing. is study examined the print quality and system e ectiveness of conventional UV exo and LED UV exo curing methods. e variables were tested on an industry standard narrow web exographic press using both LED UV curing lamps and conventional UV lamps, and were evaluated in order to compare the two systems. e results are meant to allow companies to make decisions concerning implementation of curing systems based on their current needs. e variables tested along with the methodology used for testing were as follows: • Tone & Color Reproduction » TVI Tone blocks were measured using an X-Rite 530 model spectrodensitometer in order to determine the accuracy of the printed dot size » Color Gamut L*a*b* values were measured using an X-Rite 530 model spectrodensitometer and delta E values were cal- culated in order to determine whether there was a di erence in color reproduction when using the two di erent UV curing systems • Print Process Capabilities » Positive & Negative Type e positive and negative type test on the print test sheet was examined using a Beta Flex to see how well positive and negative type is reproduced in the various runs » Slur e slur target on the print test sheet was examined using a Beta Flex in order to see if there were any problems with slur in any of the printruns » Solid Ink Density (SID) e SID was examined on the vari- ous runs using a Beta Flex to better understand how well the ink was laid down on the substrate » Tr a p e trap e ectiveness was studied using a Beta Flex • Ink Curing Speed & E ectiveness » A pass/fail test was used to determine whether the ink was fully cured or not at high and low press speeds • Substrate Temperature Under Both Lamps » An infrared thermometer was used to measure the tempera- ture of the substrate under the lamp during printing • Types of Substrates & Distortion » A print rule was measured with a ruler to determine whether any distortion of the substrate occurred due to exposure to the UV curing system • Cost of Ink » Ink costs were compared, based on the list price, type of ink and ink mileage • Additional Information Outside of Designed Experiment » A separate test was run to investigate the e ects of UV curing on a shrink lm substrate RESULTS Natalee Consulo, Lena Haidar and Mark MacManus, graphic com- munication students at California Polytechnic State University, San Luis Obispo under the advisement of Professor Colleen Twomey, designed and conducted the experiment in September of 2013 at the Flint Group's Center for Technical Excellence in Plymouth, MN. e Flint Group facility provided industry standard press conditions. e equipment provided by the Flint Group included a Mark Andy 4150 narrow web exographic press and conventional UV and LED UV curing systems. All experiments and processes were monitored and evaluated by the researchers. e press was run by Scott Shutt, an experienced exo press operator at Flint Group. e designed experiment tested di erent combinations of variables using eight pressruns. e constants included 0.020-in. 3M 1015H (medium density) stickyback for the plates. Following Flexographic Image Reproduction Speci cations & Tolerances (FIRST) recommen- dations, DuPont Cyrel DFR 0.067 digital photopolymer plates with a relief of 0.022-in. were used. Each color station was equipped with the following anilox rollers: • A 1,200 cpi (cells per inch) anilox with 1.29 bcm (billion cubic microns) volume on the yellow print station • A 1,200 cpi anilox with 1.25 bcm volume on the magenta print station • A 1,200 cpi anilox with 1.29 bcm volume on the cyan print station • A 1,000 cpi anilox with 1.25 bcm volume on the black print station Stainless steel chambered doctor blades were used in this experiment. In order to validate the original pressruns, two control test runs were performed. e rst control test was printed on paper using conven- tional UV curing at a slow press speed. e second control test was 34 FLEXO | AUGUST 2014