Details:
Summary:
The dynamic nip pressure in a flexographic printing press has been studied. The nip pressure was measured by means of thin load cells. The measurements were made in a running full-scale flexographic central impression cylinder press. The aim was to measure and estimate the dynamic nip pressure at different press speeds and different impressions, using different printing plate materials and to assess its consequence for print quality.
The printing trials were performed on a liquid packaging board with a regular water-based cyan ink. Dynamic nip measurements and ink transfer were studied in the same printing unit. Press speed and impressions were varied as well as the printing plate material.
The results showed that measured dynamic nip pressure was a good indicator of the average dynamic pressure during the press pulse in the nip. The dynamic pressure was affected only by the level of impression. Neither the plate material used nor the press speed influenced the measured dynamic nip pressure.
The print quality was evaluated as print density, dot gain and amount of ink transferred to the substrate. The print quality parameters were all affected by press speed, impression and type of printing plate. It was possible to record the dynamic nip pressure in the flexographic printing press using the arrangement with the thin load cells. The "soft" printing plate gave higher ink transfer, a higher print density and less dot gain than the "hard" printing plate.