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- Hallberg Hofstrand, Erik, et al.
(författare)
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Dynamic Measurements of Nip Force Variations during Post-Printing of Corrugated Board
- 2006
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Ingår i: Nordic Pulp & Paper Research Journal, 21(1), 111-114 (2006).
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Tidskriftsartikel (refereegranskat)abstract
- A method has been developed in order to measure nip force variations during flexographic post-printing of corrugated board. This method can be used to study the influence of the nip mechanics on the final print quality
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- Hallberg Hofstrand, Erik, 1975-
(författare)
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Flexographic Post-Printing of Corrugated Board : Contact Mechanics and Print Quality
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- As the corrugated board industry strives to produce products with a higher print quality in the converting stage, there is a need for a greater understanding of the factors influencing the final print quality and how we perceive the print. In this work, a method for quantifying the print quality of printed corrugated board is presented as well as methods that quantitatively characterize the mechanical interaction between the printing form and the corrugated board in the printing nip. The results of investigations addressing the impact of the mechanical properties of the printing form on ink transfer are also presented. A band-pass image analysis method adapted to the spatial wavelength of B-flute corrugated board was used to quantify the print quality on the board in terms of print banding. The findings were substantiated by a perceptual evaluation which showed a high correlation to the instrumental quantification. The main cause of print banding is a higher local contact pressure on the fluting tips than in the fluting valleys, which leads to a higher ink transfer to the fluting tips. A greater difference between the local contact pressure on the fluting tips than in the fluting valleys generated a higher degree of banding. The difference in local contact pressure as well as nip force variations could be measured using the proposed methods to characterize the interaction between the printing form and the corrugated board. The difference in local contact pressure was highly dependent on the mechanical properties of the components of the printing form. An increase in the stiffness in compression mode and in the bending stiffness of the printing form led to a smaller contact area in the printing nip and consequently a higher external pressure on the ink, resulting in an overall higher ink transfer but also a higher degree of banding. The influence of the mechanical properties of the printing form components was supported by the results of numerical simulations of the contact between the printing form and the corrugated board. Contact area, pressure level and texture of the local contact pressure were compared with measurements of local contact pressures for different printing forms and the results showed a high degree of agreement. Numerical simulations could thus predict the print quality achieved with different printing forms under different printing conditions.
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- Hallberg Hofstrand, Erik
(författare)
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Print Quality of Post-Printed Corrugated Board
- 2004
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The use of printed corrugated board as a packaging material has evolved from a brown box with This Side Up stamped on it to an advertiser efficient in the customerÕs critical moment of purchase. The demand for quality printing of post-printed corrugated board is growing.The purpose of this study was to gain a better knowledge of post-printing of corrugated board and quantification of banding on printed corrugated board. Post-printing trials which also included measurements of pressure variations in the printing nip were performed. B-flute corrugated board and several differently designed printing forms, belonging to the so-called thin-plate technology, were used in the trials. The evaluation of the results was focused on the contact mechanics of the ink transfer in the nip; between the ink-covered printing form and the corrugated board. The influence of the mechanical properties of the printing forms on print quality and lateral pressure variations in the printing nip were investigated. It was shown that the compressibility modulus and the bending stiffness of the printing form affected the pressure variations and ink transfer. The properties thus affect the print quality. Furthermore, a proposal for the instrumental evaluation of banding on printed B-flute corrugated board is presented. A good correlation was found between the instrumental results and the perceptual ratings.
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- Hallberg Hofstrand, Erik
(författare)
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Research Summary: Banding on Flexographic printed corrugated board : Important clues to solve an annoying problem
- 2006
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Annan publikation (populärvet., debatt m.m.)abstract
- Summary of research results based on the articles Quantification of banding on printed corrugated board using spatial frequency analysis by Erik Hallberg, Astrid Odeberg Glasenapp and Magnus Lestelius in Packaging Technology and Science 18, 89-95 (2005) and Dynamic measurements of nip force variations during post-printing of corrugated board by Erik Hallberg Hofstrand, Magnus Lestelius and Peter Rättö in Nordic Pulp and Paper Research Journal 21(1), 111-114 (2006)
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