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FLEXO Magazine : June 2014
An example of this can be il- lustrated by a recent banded roll test. A test was done to determine if a better alterna- tive is available to a 600 lpi, 4.0 bcm, 60 degree cell used by a customer for combi- nation process/line work/ solids printing and a 900 lpi, 2.6 bcm, 60 degree cell used for process print. To enable us to utilize a more durable, lower linescreen engraving without sacrificing print cleanliness, it was necessary to also decrease the cell volume as we decreased the linescreen. Eight engravings were tested: • Combination print » 600 lpi and 4.0 bcm » 550 lpi and 3.8 bcm » 500 lpi and 3.6 bcm » 450 lpi and 3.4 bcm • Process print » 900 lpi and 2.6 bcm » 850 lpi and 2.5 bcm » 800 lpi and 2.4 bcm » 750 lpi and 2.3 bcm The end result (See Image 3) was that by reducing both linescreen and volume, all four engravings in each category produced nearly identical density and dot gain results. The advantage of utilizing the lower linescreen and volume engraving is the cell surface is much smoother and it will transfer its volume more consistently. In addition, we believe engravings used with steel doctor blades should be diamond film polished mechanically after engraving, to re- move the nodules and create a flat, smooth surface that is resistant to wear. All of our engravings used with steel doctor blades receive this process. Lower cell count and volume ratios allow this process to be done with much more successful and repeatable results. Cell walls are flatter, smoother and narrower, allowing for greater durability, without sacrificing ink transfer and performance. The anilox’s “job” is to transfer a precise, predictable and consistent ink film to the printing plate. The ink film is determined by the cell volume, not the linescreen. It may be time to rethink the specifications of this important tool for greater long term printing performance, consistency and durability. n About the Authors: John Rastetter joined Pamarco Global Graphics as vice president of sales and marketing in August 2013 after more than 20 years in the print industry. His primary responsibilities are to manage sales, set strategies and execute plans for sales in North America, Canada, Central, South and Latin America. A graduate of Rochester Institute of Technology, a member of FTA, an author of articles in FLEXO® and presentations at the FPPA, his contributions to the print industry have proven his ability to remain on the cutting edge to help printers maintain quality and efficiency in print. He can be reached at 404-691-1700 or via email at firstname.lastname@example.org. John Bingham has been working with Pamar- co Global Graphics as a technical sales represen- tative for more than 10 years and has helped the company develop an impressive customer base in the Midwest region of the U.S . John has con- tributed to several FTA presentation theatres, as well as technical articles to various publications throughout the print industry. His work with Pamarco’s latest engraving technology, EFlo, over the past few years has helped countless printers improve their processes. He can be reached at 630-879-7300 or via email at email@example.com. Image 3: This table shows the results of the highest and lowest lpi for each application. Please note the lpi, bcm, density and dot gain results for each. Rastetter Bingham 60 FLEXO | JUNE 2014