Study of the influence of the anilox roller characteristics on the quality indicators of flexographic imprints

Experimental studies are carried out in the production conditions of the company Poly Pak Ltd (Lviv). In the research process, a set of anilox rollers of different lineature and ink capacity with a ceramic surface coating, an engraving angle of 600 and a hexagonal cell shape is used. AniCAM 3D microscope and software from the British company Troika Systems are used to analyze the surface of anilox rollers.

DuPont Cyrel DPR photopolymer printing plates with the thickness of 1.14 mm are used in the experimental work. Fisher&Krecke 10DF eight-color flexographic printing machine is used for the printing process. Alcohol-soluble printing inks of the Polistar Metoks series and РФЛ solvent (Fleksores, Ukraine) are used in the printing process. Printing is performed on pearl white polypropylene film with the thickness of 35 μm (Treofan Group). The quality characteristics of imprints are assessed using an eXact spectrodensitometer (X-Rite Pantone).

As a result of experimental studies of anilox rollers with different technological characteristics and imprints obtained with their use, the dependency of the imprint optical density on the cell volume of anilox rollers of different lineature is established, and it is determined that a proportional increase in the volume of anilox rollers has a more significant effect on the optical density of highly linear rollers. The influence of the anilox lineature on the optical density of imprints is established and it is determined that an increase in the lineature of anilox rollers at an unchanged cell volume proportionally reduces the optical density of imprints – an increase in the lineature by 20 lin/cm corresponds to a decrease in optical density by approximately 0.1 c.u. The dependency of the dot gain on the imprint on the cell volume of anilox rollers is established and it is determined that for a roller with the lineature of 200 lin/cm, an increase in volume by 2.4 cm3/m2 increases dot gain by 4-7%, and for a roller with the lineature of 340 lin/cm when the volume increases by 3.6 cm3/m2, dot gain increases by 3-4%. The dependency of the dot gain on the imprint on the anilox roller is established, and it is determined that for rollers with the cell volume of 5.5 cm3/m2, a change in the lineature from 200 to 340 lin/cm leads to a decrease in the dot gain by 5-7%. The dependency of the color deviation index on the imprint on the color transfer of the anilox roller (the thickness of the ink layer) for some triad and pantone printing inks is established.

The results of the experimental studies have made it possible to develop practical recommendations for the optimal use of anilox rollers in the technological need to change the optical density, characteristics of tone reproduction or color reproduction on flexographic imprints.

Keywords: flexographic printing, anilox roller, anilox lineature, ink transfer, optical density, dot gain, packaging.

doi: 10.32403/0554-4866-2023-1-85-145-154