Influence of Substrate and Screen Thread Count on Reproduction of Image Elements in Screen Printing

The printing plate and its characteristics in the conventional printing techniques have a significant impact on print quality and image appearance. In screen printing, a weave of screen mesh i.e. a number of threads per cm, is the most important characteristic of the printing plate, hence the most relevant factor which defines printing quality. Print quality itself is a complex term that includes desired colour reproduction and satisfactory reproduction of image elements. In this paper focus was centred upon the reproduction of text and basic image elements (lines and dot structure) when printing on non-absorbent and absorbent substrates with different screen thread counts. The image element analysis led to the conclusion that using mesh with higher thread count does not significantly improve the reproduction of image elements. However, it is a very important parameter for text reproduction since low thread count may result in poor readability

Influence of Substrate and Screen Thread Count on Reproduction of Image Elements in Screen Printing

The printing plate and its characteristics in the conventional printing techniques have a significant impact on print quality and image appearance. In screen printing, a weave of screen mesh i.e. a number of threads per cm, is the most important characteristic of the printing plate, hence the most relevant factor which defines printing quality. Print quality itself is a complex term that includes desired colour reproduction and satisfactory reproduction of image elements. In this paper focus was centred upon the reproduction of text and basic image elements (lines and dot structure) when printing on non-absorbent and absorbent substrates with different screen thread counts. The image element analysis led to the conclusion that using mesh with higher thread count does not significantly improve the reproduction of image elements. However, it is a very important parameter for text reproduction since low thread count may result in poor readability

Influence of the surface roughness of coated and uncoated papers on the digital print mottle

Many factors influence the occurrence of print mottle in prints. In printing process three main components are involved: printing press, substrate and toner. They can be considered as separate components, but in most cases their interaction influences the quality of the print. The goal of this work was to examine the influence of surface roughness of different types of paper (coated and uncoated on print mottle of electrophotographic digital prints. We set up a hypothesis that print mottle will be more apparent on rougher surfaces. In the experimental part we printed four different substrates with different surface properties on electrophotographic printing press. Morphology of the papers surface was analysed using atomic force microscopy (AFM) from which surface properties were calculated. For print mottle characterization Gray level co-occurrence matrix (GLCM) method was used. Based on the measurements and results we can conclude, contrary to the initial hypothesis, that uncoated papers with rougher surfaces produce smaller print mottle values

Texture Evaluation of Automotive Coatings by Means of a Gonio-Hyperspectral Imaging System Based on Light-Emitting Diodes

Sparkle and graininess are textural effects that appear as intrinsic spatial features of coatings containing goniochromatic pigments, whereas others such as mottling are undesired outcomes. In this study, we present new methods for the evaluation of sparkle, graininess and mottling of automotive coatings through images acquired with a novel gonio-hyperspectral imaging system based on light-emitting diodes with extended spectral sensitivity beyond the visible range (368–1309 nm). A novel analysis of sparkle that considered the amount of sparkling spots was used. Graininess was quantified through a novel statistical descriptor based on the energy descriptor computed from the histogram. A new index was proposed for an enhanced detection of mottling based on the analysis of striping, which was better observed and quantified in the infrared range. Spectral assessments showed a strong relationship with color and spectral reflectance for graininess and mottling. In conclusion, the results showed that these new spatial and spectral methods are a suitable, alternative and potential approach for the assessment of these textural features.Ministerio de Ciencia e Innovación (MICINN, DPI2011-30090-C02-01) and Ministerio de Economía y Competitividad (MINECO, DPI2014-56850-R); and the European Union

Visual quality of printed surfaces: Study of homogeneity

International audienceThis paper introduces a homogeneity assessment method for the printed versions of uniform color images. This parameter has been specifically selected as one of the relevant attributes of printing quality. The method relies on image processing algorithms from a scanned image of the printed surface, especially the computation of gray level cooccurrence matrices and of objective homogeneity attribute inspired of Haralick's parameters. The viewing distance is also taken into account when computing the homogeneity index. Resizing and filtering of the scanned image are performed in order to keep the level of details visible by a standard human observer at short and long distances. The combination of the obtained homogeneity scores on both high and low resolution images provides a homogeneity index, which can be computed for any printed version of a uniform digital image. We tested the method on several hardcopies of a same image, and compared the scores to the empirical evaluations carried out by non-expert observers who were asked to sort the samples and to place them on a metric scale. Our experiments show a good matching between the sorting by the observers and the score computed by our algorith

INVESTIGATION OF HALF-TONE MOTTLE IN COATED PAPERS BY VARYING GRAVURE PROCESS PARAMETERS

Half-tone mottle is due to uneven ink transfer and ink penetration, which generates an inhomogeneous image to the human eye, thereby affecting the saleability of the product. Design of Experiments (DOE) was done with gravure process parameters such as line screen, ink viscosity, press speed, ESA (Electrostatic Assist) voltage and the air gap at varying levels to evaluate the effect of these process parameters on half-tone mottle. The Stochastic Frequency Distribution Analysis (SFDA) algorithm was used to measure surface properties of paper and half-tone mottle. The experimental data were analysed through ANOVA, main and interaction plot. The results revealed a reduction in mean halftone mottle by 90.48% and 91.25% for 50 GSM and 65 GSM C1S paper respectively. The regression models were developed and validated by conducting additional runs. The results hence obtained shall help to optimize ink transfer and identify the key process variables minimizing half-tone mottle; thereby enhancing the print quality

Washing treatment impact on print quality of screen printed knitted fabrics

The surface of textile materials is highly textured, commonly in non-uniform ways. Because of this texture effect, textile surface appears rougher and more porous than other printing substrates, which can cause excessive ink penetration during printing process. Next, washing process is very important factor because it influences ink characteristics on printed samples as well as structural changes of the textile substrate. The aim of this paper is to determine the influences of washing process and different mesh tread count used for printing on print quality. This will be obtained by using spectrophotometric analysis, and GLCM image processing method for print mottle estimation. The results of this research show that increasing number of washing processes leads to higher color differences reproduction color in comparison to printed materials before washing. It also shows that textile surface texture has a great influence on print mottle as well as that number of washing treatment series can generate variations of solid-tone print uniformity. Keywords: cotton, different thread count, GLCM, spectrophotometric analysis, series of washing process

An Analysis of the factors influencing paper selection for books of reproduced fine art printed on digital presses

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