Anilox

In printing, anilox is a method used to provide a measured amount of ink to a flexo printing plate An anilox roll is a hard cylinder, usually constructed of a steel or aluminum core which is coated by an industrial ceramic whose surface contains millions of very fine dimples, known as cells.

Depending on the detail of the images to be printed, the press operator will select an anilox roll with a higher or lower line screen. Low line screen rolls are used where a heavy layer of ink is desired, such as in heavy block lettering. Higher line screens produce finer details and are used in four-color process work such as reproducing photographs. Often a job will require a different line screen for each color to be printed. Experienced press operators are skilled at determining the appropriate rolls for a given print job. Depending on the design of the printing press, the anilox roll is either semi-submerged in the ink fountain, or comes into contact with a so-called metering roller, which is semi-submerged in the ink fountain. In either instance, a thick layer of typically viscous ink is deposited on the roll. A doctor blade is used to scrape excess ink from the surface leaving just the measured amount of ink in the cells. The roll then rotates to contact with the flexographic printing plate which receives the ink from the cells for transfer to the printed material.

Anilox rolls were originally made using a diamond pecking machine, but modern rolls are laser engraved. The characteristics of an anilox roll determine the amount of ink that will be transferred to the plate: angle of the cells, cell volume, and line screen. A 60 percent angle ensures maximum density in a given space. Lower volume makes for less ink. Low line numbers will allow for a heavy layer of ink to be printed, whereas high line numbers will permit finer detail in printing. Both cell volume and line screen are closely correlated.

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