Impact of Screen Ruling on the Formation of the Printing Elements on the Flexographic Printing Plate

Flexography is a printing technique widely used in the packaging production. The main feature of flexography is the use of a printing plate elastically deformed during the reproduction process. The printing plate is made of an elastic material, rubber or nowadays of mainly different types of photopolymer. The elasticity of the plate enables the printing on a wide range of printing substrates, which is one of its advantages compared to other printing techniques. On the other hand, deformations of the printing plate in the printing process caused by the pressure between the printing plate and the substrate present a major limitation of flexography. Apart from the functional properties of the printing plate in the printing process, the plate making process, including photo polymerization, considerably influences the value of halftones on the printing plate, and consequently on the final product. The aim of this paper is to examine the influence of screen ruling on the formation of printing elements and the adjustment of the printing plate making process in order to achieve optimal quality of the printing plate and, therefore, the final product. The results have shown that the use of different screen rulings is of great significance in the processes of printing plate curve adjustment. It was proven that the use of different screen ruling has a considerable influence upon relief depth and a cross-section of the printing elements (3D analysis), which again have a significant impact on the quality of the final product, but cannot be detected in 2D analysis