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FLEXO Magazine : June 2013
Technologies & Techniques Hybrid Anilox Rollers solve High Volume, High graphics, High Definition image Challenges By Ashley Foran Flexography remains the fastest growing printing pro- cess, thanks in great part to the flexo printer’s drive to achieve the high ink density and high graphic image quality previously reserved for offset or gravure presses. The reasons many companies have been able to switch to more efficient flexo printing over the last two decades can be credited to innovations in inks, plates, presses and anilox roll design, as well as to the improved skills and artistry of today ’s flexo press operators. As printers continue to stretch the abilities of flexography, they are learning that the innovations in anilox roll design can give them more flexibility with a wide variety of substrates and maintain greater consistency in the end product. Today ’s typical anilox ink metering roller is a steel cylin- der covered with a ceramic layer that is laser engraved with rows and rows of microscopic “ink wells” called cells. Ink, of course, needs to be sticky in order to adhere to your end product. As the relatively flat surface of the printing plate presses against those roller cells, the ink wants to “stick” to the inside of the cells, as well as to the plate, causing each microscopic pool of ink to split. (Figure 1). The ink picked up by the plate is again shared, this time with the substrate. In fact, less than one-quarter of the ink that fills the anilox cell actually makes it to the printed product. The science used to advance the design of anilox rollers in recent years gives printers the ability to deliver greater ink volume in high graphic and high definition work. In North America, ink volume is usually measured in billions of cubic microns (BCM) per square inch—a micron being one-mil- lionth of a meter. Put another way, on a roller rated at 8 BCM, it would take 25 square inches to hold the volume of ink equal to the size of one pea! That same volume of ink on a 300 lines per inch (lpi) roller would fill 2.25 million cells. HOLDING THE LINE ON HIGH VOLUME The one job of an anilox roller is to deliver to your plate a consistent, measured amount of ink at every turn of the roll—job after job. In the early years of flexo, it was fairly easy to pick the right anilox roller for the job. Most flexo work was made up of solids and lines, and if screens were involved, they were rather coarse, requiring plates with a relatively low dots ANILOX CELLS & GRAPHICS APPLICATIONS • By manipulating the way the cell is formed, greater ink volumes can be achieved for those high graphic applications that require rollers with a higher lpi specification • Because more high definition images are being created on digital plates, higher ink volumes are needed on rollers in the highest lpi ranges, in order to maintain density and clarity. • New laser technology enables anilox roller engravers to create hybrid roller cells shaped like extended hexagons • High definition anilox rolls. can greatly reduce setup time and scrap production, while maintaining quality standards on print jobs that require consistent coverage and greater density control 42 FLeXO June 2013 www.flexography.org Figure 1 Figure 2