Development of a scheme for the distribution of contact areas between the plate and offset cylinders

Abstract

The object of the research is the distribution of contact areas between the plate and offset cylinders. For printing impression in the offset printing process, it is necessary to ensure the transfer of printing ink from the ink unit to the printing plate, from the mold to the rubber-fabric material (deckel) of the offset cylinder and from the deckel to the printed material. At the same time, the quality of the prints is ensured by creating the necessary technological pressure between the plate, offset and printing cylinders, which also contributes to the deformation of the elastic deckel and the transfer of the ink layer in the contact zone. The transfer of illustrative and textual information from the form to the deckel of the offset cylinder occurs due to the actual touch area. Therefore, the study and calculation of the actual contact area is necessary to study the transfer of the paint layer in the contact zones. For this purpose, a review of some studies on contact problems was carried out, their advantages and disadvantages were discussed. Theoretical and experimental relations are given. It has been established that micro protrusions of the surface roughness of the printing plate significantly affect the deformation of the deckel. To study the influence of the surface roughness distribution of the printing plate on the actual deckel contact area in the contact zone, the interaction of micro protrusions of the surface roughness of the printing plate with the deckel surface, leading to additional displacements, was taken into account. A method for calculating the number of roughness protrusions is proposed to further determine the actual deckel contact area and the actual pressure in the contact zone, taking into account the surface roughness of the printing plate. Based on the parameters calculated by the proposed method with known values of the surface roughness of the printing plate in the future it is possible to determine the actual deckel contact area and the actual contact pressure the optimal values of which are necessary to ensure the required ink transfer and print quality during printing. The data obtained also contribute to the determination of the modes of the printing process when printing the entire circulation, which leads to an increase in the circulation stability of printing forms. Increasing the circulation stability of printing plates allows to save the number of consumed printing plates. In the future, according to the results obtained, it is recommended to compile reference data, which are necessary when setting up and operating the printing machine.