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Nip Mechanics, Hydrodynamics and Print Quality in Flexo Post-Printing
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics. (Fibre-based Material Technology)
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Sundsvall: Kopieringen , 2010.
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:miun:diva-11347OAI: oai:DiVA.org:miun-11347DiVA, id: diva2:302324
Public defence
(English)
Supervisors
Projects
Nip Mechanics and Hydrodynamics of Flexo Post-Printing and Print Quality
Available from: 2011-01-14 Created: 2010-03-05 Last updated: 2011-01-14Bibliographically approved
List of papers
1. Nip Mechanics of Flexo Post-Printing on Corrugated Board.
Open this publication in new window or tab >>Nip Mechanics of Flexo Post-Printing on Corrugated Board.
2007 (English)In: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 41, no 17, p. 2129-2145Article in journal (Refereed) Published
Abstract [en]

A finite element model of a flexo printing press has been developed and the material and geometrical properties of the sustem has been investigated. The results showed that it is the photopolymer and the top liner that have the biggest impact on the printing pressure variations.

Keyword
Flexo, Striping, Corrugated Board
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-311 (URN)10.1177/0021998307074135 (DOI)000249099200007 ()2-s2.0-34547522828 (Scopus ID)
Available from: 2008-12-11 Created: 2008-12-11 Last updated: 2017-12-13Bibliographically approved
2. Striping of Corrugated Board in Full-tone Flexo Post-Printing
Open this publication in new window or tab >>Striping of Corrugated Board in Full-tone Flexo Post-Printing
2008 (English)In: Appita journal, ISSN 1038-6807, Vol. 61, no 1, p. 35-40Article in journal (Refereed) Published
Abstract [en]

Striping is a print defect that is often seen in flexo post-printing on corrugated board. It appears as lines parallel to the flutes of the corrugated medium (fluting). These lines are generally thought to be print density and/or print gloss variations. The objective of this Paper is to obtain fundamental understanding of the striping mechanism. Print density and print gloss have been determined as a function of printing pressure. Typical printing pressure variations have also been determined by a non-linear finite element method. A 2D reflectance mapping has been performed for printed corrugated boards. The results showed that striping is dominated by print density variations for uncoated board, and the print density variations are, in turn, caused by the printing pressure variations. The extent to which the pressure variations appear as print density variations depends on the ink transfer characteristics of the liner board.

National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-312 (URN)000252686700007 ()2-s2.0-38349104629 (Scopus ID)5138 (Local ID)5138 (Archive number)5138 (OAI)
Projects
Nip Mechanics and Hydrodynamics of Flexo Post-Printing and Print Quality
Note
VR-ChemistryAvailable from: 2008-12-10 Created: 2008-12-02 Last updated: 2017-12-13Bibliographically approved
3. Print Uniformity of Corrugated Board in Flexo Printing: Effects of Corrugated Board and Halftone Dot Deformations.
Open this publication in new window or tab >>Print Uniformity of Corrugated Board in Flexo Printing: Effects of Corrugated Board and Halftone Dot Deformations.
2008 (English)In: Packaging technology & science, ISSN 0894-3214, E-ISSN 1099-1522, Vol. 21, no 7, p. 385-394Article in journal (Refereed) Published
Abstract [en]

Print non-uniformity problems are a major concern for flexo post-printers. Many of these non-uniformities are suspected to be caused by the corrugated board structure itself. Striping is the most obvious one, but also other print quality problems might be structure-related. This work focuses on how deformations of the board might lead to print non-uniformities, and if the deformation of halftone dots is the mechanism behind striping in halftone flexo post-printing. The problems were analysed by using finite element models to simulate deformed board and halftone dot compression in the printing nip. Distortions of the board due to non-uniform hygro-thermal strains were shown to be a potential cause of print non-uniformities. Striping in halftone prints was found to be caused by differences in dot gain between ridge and valley areas above the flute structure.

Keyword
corrugated board, dot gain, flexo, halftone, striping, warp
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-313 (URN)10.1002/pts.816 (DOI)000260649100002 ()2-s2.0-55649096951 (Scopus ID)5139 (Local ID)5139 (Archive number)5139 (OAI)
Projects
Nip Mechanics and Hydrodynamics of Flexo Post-Printing and Print Quality
Available from: 2008-12-11 Created: 2008-12-11 Last updated: 2017-12-13Bibliographically approved
4. Simulation of two-phase flow with moving immersed boundaries
Open this publication in new window or tab >>Simulation of two-phase flow with moving immersed boundaries
2011 (English)In: International Journal for Numerical Methods in Fluids, ISSN 0271-2091, E-ISSN 1097-0363, Vol. 67, no 12, p. 2062-2080Article in journal (Refereed) Published
Abstract [en]

A two-dimensional model for immiscible binary fluid flow including moving immersed objects is presented. The fluid motion is described by the incompressible Navier-Stokes equation coupled with a phase-field model based on van der Waals’ free energy density and the Cahn-Hilliard equation. The immersed boundary method has been utilised to handle moving immersed objects and the phase-field boundary conditions have been adapted accordingly. Numerical stability and execution time was significantly improved by the use of a new boundary condition which implements minimisation of the free energy in a direct way. Convergence toward the analytical solution was demonstrated for equilibrium contact angle, the Lucas-Washburn theory and Stefan’s problem. The proposed model may be used for two-phase flow problems with moving boundaries of complex geometry, such as the penetration of fluid into a deformable, porous medium.

Keyword
fluid-structure interaction, immersed boundary, moving boundary, two-phase flow
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-10571 (URN)10.1002/fld.2484 (DOI)000297736100018 ()2-s2.0-83255186838 (Scopus ID)
Projects
Nip Mechanics and Hydrodynamics in Flexo Post-Printing and Print Quality
Available from: 2009-12-07 Created: 2009-12-07 Last updated: 2017-12-12Bibliographically approved
5. Transfer of a microfluid to a stochastic fibre network
Open this publication in new window or tab >>Transfer of a microfluid to a stochastic fibre network
2011 (English)In: Journal of Fluids and Structures, ISSN 0889-9746, E-ISSN 1095-8622, Vol. 27, no 7, p. 937-946Article in journal (Refereed) Published
Abstract [en]

The transfer of a microscopic fluid droplet from a flat surface to a deformable stochastic fibre network is investigated. Fibre networks are generated with different levels of surface roughness, and a two-dimensional, two-phase fluid-structure model is used to simulate the fluid transfer. In simulations, the Navier-Stokes equations and the Cahn-Hilliard phase-field equations are coupled to explicitly include contact line dynamics and free surface dynamics. The compressing fibre network is modelled as moving immersed boundaries. The simulations show that the amount of transferred fluid is approximately proportional to the contact area between the fluid and the fibre network. However, areas where the fluid bridges and never actually makes contact with the substrate must be subtracted.

Keyword
fibre network, flexo, fluid-structure interaction, fluid transfer, moving boundaries, two-phase flow
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-11295 (URN)10.1016/j.jfluidstructs.2011.06.003 (DOI)000295300900004 ()2-s2.0-80052260413 (Scopus ID)
Projects
Nip mechanics and hydrodynamics of flexo post printing and print quality
Available from: 2010-02-19 Created: 2010-02-19 Last updated: 2017-12-12Bibliographically approved

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Citation style
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Output format
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