Effect of printing parameters on delamination of board in sheet fed offset printing

Delamination of board in sheet fed offset printing has become a frequent source of complaints. Both printing parameters and structural properties of board affect delamination tendency however little attention has been given to the printing parameters. The purpose of this study was, through printing trials and physical simulation, to find out the effect of printing parameters on delamination. High printing speed promotes delamination. Similarly, high ink viscosity at low shear rate, among other ink and printing parameters, had an obvious effect on delamination. Both printing speed and ink properties affect the maximum ink tack in ink splitting. The force at the delaminating interface is proportional to this ink tack. Other printing parameters which contributed to delamination of board to a certain degree were printing press configuration, number of dry backtrap nips, ink density, printing blanket compressibility, blanket smoothness, nip pressure, nip indentation, and fibre-orientation in the printing sheet.