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Flexo Magazine : June 2013
Industry Indicators From Art to Science: The Evolution of the Anilox Roll Demand for Better Graphics Drives innovation By Pat Kent Evolution can be described as a continuing process of change from one state or condition to another. A gradual change in characteristics developed over successive generations. This describes the flexographic engraving process, as well as changes in ink chemistry, plate technologies, substrates, graphic demands and machinery that have occurred over the past 100 years. The metering of ink once employed two rubber rolls to transfer the fluid to a rubber print die. The only adjustment was in the pressure of the rolls. It was not until 1939 that the first chemically etched roller was used to meter ink. From that time the anilox roll has experienced many changes in how the cell is formed. These changes were driven by the improvements in ink metering systems, plates, and substrates, as they evolved to meet the ever-changing requirement for better graphic quality. MECHANICAL ENGRAVING ENHANCEMENTS Mechanically engraved rolls are still in use today but are mainly used for coating and very coarse rolls for glue and starch application. The process uses an engraving tool that is pressed at high pressure into the surface of a roll. This displacement method of engraving results in the slight growth of the roll diameter. Most of these engravings are at a 45-degree angle. One significant change in the cell of a mechanical engrav- ing came with the introduction of the channeled cell. The QCH engraving is at 90-degrees and has a channel that con- nects all the cells around the roll, allowing for a very smooth lay down of ink or coating. The next innovation was the Roto-Flo engraving. The cells form a “Z ’ pattern and are engraved at 26-degrees. This engraving supported the doctor blade and virtually elimi- nated striations. Another advantage of this engraving was the TIME CAPSULE • 1930s and Earlier—Metering of ink employed two rubber rolls to transfer fluid to a rubber print die • 1939—First chemically etched roller comes into use in metering ink • 1940s-1960s—Mechanical engraving technologies advance to include channel and “Z” pattern cells • 1960s-1970s—Ceramic anilox roll debuts • 1973—Micro ceramic anilox roll gets patent • 1980-1983—Laser engraving emerges • 1980s—CO2 lasers produce anilox cells at 500 lpi • 1990s— Ablative YAG Laser makes well formed cells with little recast. Line screens of 900-1,000 are possible • 1990s—Ablative multi hit YAG and CO2 lasers continue to improve, as new optical and electronics are developed. These allow for improved cell structure and volume ranges • 2000s—Development of the Thermal Fiber Optic YAG opens the line screen options to higher than 1,200 lpi • 2000s—Major leap in thermal YAG laser technology brings increased power, new software and electronic capabilities that combine to allow for a full range of screen counts from 35 to 1,800 lpi. • Today—Hybrid screens are engraved into ceramics in a very controlled and consistent manner, offering greater graphic capability. Elongated shape of the cell and dual line screen allows for improved ink release, resulting in improved solid coverage and the ability to print screens cleanly 62 FLEXO June 2013 www.flexography.org