An investigation into plate deformation in flexographic printing

Deformation of the flexographic printing plate is an important factor in determining the quality of the printed image. A numerical model of the individual dots has been developed and used to examine the deformation of the plate under a range of printing conditions and image characteristics. Two mechanisms have been identified for the deformation of the image on the plate: expansion of the dot surface and dot barrelling. These results have been combined with those from an experimental study to apportion the dot gain due to ink spreading and physical deformation of the dot. The results have shown the low-coverage dots at high line rulings to be particularly affected by the effect of variation in the impression pressure. This has significant implications for the ability of the process to reproduce high-resolution images that combine both highlight and shadow regions successfully and consistently. Ink spreading has been identified as the major cause of dot gain, except at low coverages, where the deformation of the dots makes a significant contribution.