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FLEXO Magazine : June 2011
Technologies & Techniques screw thread stretched horizontally across the roll face. Es- sentially, two walls form the cell, which extends continuously across the roll face in a spherical manner. Like the quad, the trihelical offered incredible cell volumes with early engraving technology. Some attempts have been made to utilize high screen count, low volume trihelicals for ink applications with mixed results. Now, with few exceptions the trihelical cell shape has been relegated to a place in laser- engraving history. Potential applications for trihelicals, today, may be the transfer of materials with large particle sizes like varnishes or coatings for high coating weights or thicknesses. In terms of clean up, this cell shape has some advantages. 60° HEXAGONAL Often described as one of the biggest breakthroughs in laser-engraving technology, the development of the 60-degree hexagonal shaped cell changed the direction of the entire flexographic printing industry. Trying to make quad shaped cells with a round beam just doesn’t make sense. By placing the blasts of the laser beam closer together the hexagon allows more cells per square inch—15 percent more to be exact. Along with the increased cells per square inch, the hexagon is constructed with all open or obtuse angles, creating a more efficient cell shape in terms of release and clean up. Cell walls are thinner and cell depth is shallower than quad shaped cells to attain the same volume. The 60-degree hex offers the ultimate control of ink film thickness with all six walls being the same height, when made properly. Early hexagonal cell shapes were widely accepted as the best option for high quality print or transfer of inks and coatings. Despite their success they had limits in volume capability for coatings, based on available laser-engraving technology. Early UV inks and coatings with higher or extreme viscosities created issues on press, such as “ink spitting” and doctor blade hydroplaning. Large particle sizes also limit the use of 60-degree hexagon cells in relation to cell count. Today, without question, the 60-degree hexagon shaped cell, dominates the pressroom for efficient, high quality print. For water, solvent and UV ink systems the 60-degree hex is the cell shape of choice with few exceptions. Changes in UV inks, over time, have reduced viscosities eliminating early press is- sues. Current engraving technology also allows for engraving extreme volume hex shaped cells, when required. Clean up is relatively easy when done properly and when inks / coatings are wet. 30° HEXAGONAL A variation on the benefits of the hexagonal cell shape created with the round laser beam, the 30-degree hex, when specified and made properly, incorporates a channeling ef- fect allowing the flow of inks and or coatings underneath the theDiff erence! ExperiencetheDiff erence! Experience 866.282.7697 fax 800.223.6869 www.AndersonVreeland.com info@AndVre.com Fast, customized continuous web printing with exceptional color quality for short runs. pro510DW TM More and more of your customers are asking for jobs you wouldn’t handle on your high-speed web press – shor t-run quantities with variable data and variable forms. What you need is an asset that can give you a big advantage on small jobs. Protect printed materials with optional Kompac EZ Koat UV and aqueous coater. AV_9620.5_OKI_ad.indd 1 5/25/11 2:12:09 PM www.flexography.org June 2011 FLeXO 51
Sustainable Spring 2011