Abstract
This paper researches the issues related to the print quality in flexography, especially the influence of the print run and inadequate printing settings on dot deformation. Dot deformation can lead to inconsistencies in print quality, such as a loss of highlight tones or an unpredictable increase in tonal value. This research was conducted on two concrete examples of flexible packaging printed on transparent films. All significant parameters of dot deformation were evaluated, including dot coverage, dot sharpness and the uniformity of the ink density. The increase in the coverage values in the midtones was linear throughout the entire print run, while in the light tones, it was more logarithmic. The overall percentage deviations from the reference value were 6.3% in the midtones and 52.6% in the light area. The increase in dot coverage was due to the wear of the polymer plate, which caused the side shoulders of the dot to become a part of the printing surface. An analysis of the ink density showed a much more homogeneous shape of the dot at the beginning of the print run. The correct ratio of the anilox roller line screen to the line ruling of the printing plate is important in order to ensure a minimum dot size in print.
Highlights
The development and progress of flexography is constantly increasing, and it can be said that the developments and trends in food packaging are responsible for such great expansion of this printing technique
The entire print run was printed under the same conditions of the printing process, which included the settings of the printing machine, anilox rollers, pressure during printing and printing plates
Experiment 1 involved the influence of a print run size on the dot deformation in the print
Summary
The development and progress of flexography is constantly increasing, and it can be said that the developments and trends in food packaging are responsible for such great expansion of this printing technique. Due to the elastic printing plates, this printing technique makes it possible to print on a variety of absorbent and non-absorbent printing media, such as thin films, flexible and rigid foils, almost all papers, cardboards of various thicknesses and weights and rough surface packaging materials [7]. PLA films, as non-absorbent materials, require modification of the surface before the printing process in order to improve the wettability of the substrate and to obtain proper ink adhesion to the substrate [8]. Dot deformation is a term that refers to the quality of halftone dots, such as dot sharpness, edge smoothness and the uniformity of the density across dots, as influenced by different characteristics of the printing process [9]
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