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Title: An investigation into quality improvements in flexographic printing
Author: Bould, David
Awarding Body: Swansea University
Current Institution: Swansea University
Date of Award: 2001
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An investigation has been undertaken to examine the role of the printing plate on tone gain in flexographic printing. Experimental techniques have been combined with finite element models of individual dots to quantify plate deformation as it passes through the printing nip. Dot profiles for three line rulings and two plate thicknesses have been quantified, which showed that dot area on the plate is generally less than the nominal coverage. Dot depth decreased as coverage and line ruling increased, indicating that the line ruling affects the shoulder angle of the dot. Finite element techniques revealed two mechanisms of plate deformation, which were the expansion of the dot surface and barrelling of the dot shoulder. Engagement had the greatest effect on plate gain, with line ruling being the second most important parameter. Coverage had no individual effect on plate gain, although it interacted with line ruling, dot depth and engagement. Results from the experimental investigation showed that total tone gain was significantly higher than results from the numerical investigation, due to ink spreading on the substrate: For high engagements, the difference in tone gain was small, as there was only a finite volume of ink present, restricting its ability to spread. Comparison of experimental and numerical results showed that plate deformation accounted for the majority of total gain for low coverages due to the low volume of ink present for the relatively large dot perimeter. For mid-tone coverages, the proportion of total gain due to plate deformation was approximately one fifth. This increased slightly for coverages approaching the solid as the available perimeter decreased, reducing the ability of the ink to spread .. This investigation has improved fundamental understanding of the role of the plate in flexographic printing. Use of numerical models has enabled exploration of parameters, which cannot be investigated experimentally .
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available