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Presentations 2015, 2016

iarigai Toronto 2016
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Evolutions in food packaging printing

You are here: Conferences & Events * 2010 Montreal * Abstracts * 3. Improving printing process

3. Improving printing process

3.07 Influence of gravure process on ink lifting efficiency

Soile Passoja, Asko Sneck, Yingfeng Shen, Jorma Koskinen, Robert Roozema

Electrostatic assistance (ESA) lifts gravure ink from the engraved cells before actual nip contact. This improves ink transfer. In this work the influence of ESA on ink lifting speed and height was examined with both electromechanically engraved and laser etched cells using numerical simulation and experimental studies. Ink lifting occurs quite similarly from both cell types: without ESA ink stays in the cells until the physical ink-substrate contact in the nip is formed. With ESA ring shaped ink lifting near the cell edges is noted before the nip contact. This leads to a doughnut shape contact area in the nip. Higher ESA levels lead to faster ink lifting and stronger ring shaped ink lifting in the cells. Ink lifting occurs faster from U cells than from V cells when the cells are having the same diameter and depth. This however means different ink volume in the cells. The cell geometry affects the shape of the printed dots: even and round dots are printed with cells having flat bottom. This nearly constant depth of the cell provides equally distributed ink in the cell offering also more even ink transfer.

Keywords: gravure printing, electrostatic assistance, cell geometry, ink lifting
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3.08 Using microwave drying systems in the Graphic Arts. Modern solutions for environmental industrial applications

Marios Tsigonias, Eugenia Ploumi, Anastasios Politis, George Vekinis

A large share of the cost of production in the Graphic Arts industry corresponds to the energy consumed. This is estimated at roughly 10% of total cost of the production.
The present study is a first-order investigation of the potential amount of energy that can be recovered from the replacement of conventional drying methods with microwave (MW) drying. Ambient drying methods, infrared radiation or other hot air drying methods, require a long drying period and large amounts of energy.

Besides that, conventional drying mechanisms lead to, in certain cases, insufficient drying which results in misprints and added cost.

On the other hand, with the use of microwaves it is possible to achieve satisfactory drying of various materials since microwaves have the ability to interact with polar molecules such as water and penetrate non-conductive materials to some depth heating any contained water. Because of this ability, microwaves are used in various industrial applications that require drying or desiccation. Several applications can be mentioned, such as the ceramic materials industry (hi-tech applications, bricks and porcelains), dried fruits and other foods, in the desiccation of by-products of biological waste treatment, thermal inertification of asbestos and other.

Microwave drying systems have the potential to work with all the existing printing technologies and produce a very good printing result. Additionally, they offer two important comparative advantages: energy efficiency and the effective use with water-based inks and varnishes. These potential capabilities make microwaves ideal candidates for new applications towards more environmental sustainability in printing.

Keywords: microwave drying, energy efficiency, water based inks, polar solvent based inks, green graphic arts industry
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3.09 Effect of Blanket Properties on Web Tension in Offset Printing

Merja Kariniemi, Markku Parola, Artem Kulachenko, Joonas Sorvari1, Leo von Hertzen

VTT and KCL together with several companies in the printing value chain have studied how to control web tension in different parts of a printing press. Extensive trials on printing presses, at pilot scale and at laboratory scale have yielded data for modeling work. Modeling was carried out with statistical methods and by finite element method (FEM). Results show the extent to which paper and printing blankets affect tension formation in a printing press. The main emphasis of this paper is on the effect different printing blanket types have on web tension.

It was found that printing blankets have a clear effect on web tension. The degree of tension change is affected by the type of blanket, nip pressure, distances between the blankets, moisture, paper properties and the combination of blanket types in different printing units. Depending on their feeding properties and their effect on web tension, in general, the blankets can be distinguished as negative, neutral and positive. Also the blanket’s effect on web tension is influenced strongly by the type of adjacent blankets. The interactions of fountain solution, ink, nip, blanket and paper had also an effect on the tension formation. The paper experiences a very high rate of strain inside the printing nips, which can affect the paper’s response and therefore tension after the nips. Results suggest that tension cannot be solely predicted with the elastic paper properties measured by conventional methods.

Keywords: offset printing, web tension, runnability, printing blanket, paper
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