Details:
Summary:
The flexographic printing plate undergoes deformation during the printing process that is dependent on the engagement, plate characteristics and the image. Previous work has shown that the individual dot, particularly in the highlight region experiences two forms of distortion that both result in tone gain. These are expansion of the surface of the dot and "barrelling", where the compression of the dot by the pressure in the printing nip causes the shoulder to make contact with the printed surface. This paper examines the influence of geometry (dot size and shape) on tone gain behaviour.
A model of the dot structure was created using a finite element modelling system. The model allowed the study of the deformation of the dot with time as a load is applied simulating its passage through the printing nip junction. Numerical experiments were designed and used to establish the influence of the geometric characteristics with the minimum number of calculation runs. An L16 orthogonal array investigation was carried out where the dot geometry was derived from interferometer measurements on plates having different line rulings, dot depth and plate thickness. The simulations were run over a range of engagements and this also allowed the interaction of these parameters to be studied. The results highlight the importance of the dot structure on the plate and its likely impact on tone gain during printing.