Analysis of color measurement uncertainty in a color managed printing workflow

Peter Nussbaum, Aditya Sole, Jon Y. Hardeberg
E-mails: peter.nussbaum@hig.no; aditya.sole@hig.no; jon.hardeberg@hig.no
Gjøvik University College, Gjøvik, Norway

Abstract

Since the recent revision of ISO 12647-2 and ISO 12647-7, specifying the requirements for systems that are used to produce hard-copy digital proof prints, the use of color measurement instruments is even more than before required in the printing industry. Currently, there are many different makes and models of color measurement instruments used in the industry. Therefore, in a modern color managed printing workflow, most of the printing houses use more than one color measurement instrument, typically one instrument in each department (pre-press, press, and post-press).

In this paper, a total of nine commercial spectrophotometers are compared in terms of measurement uncertainty, precision and accuracy, repeatability and reproducibility. The BCRA series 2 ceramic gloss tiles are used to confirm the accuracy and repeatability of these measuring instruments according to the manufacturer’s standards. We focus especially on inter-instrument and inter-model reproducibility and discuss the effect of instrument calibration and certification.

For our experimental setup, four different materials are used, one proof print, one commercial print, and one reference print, along with the BCRA series 2 ceramic gloss tiles. In a color managed printing workflow the use of more than one instrument can impair and complicate the color process control due to the color differences between different measurement devices. The effect of the colorimetric measurement errors due to large inter-instrument and inter-model variability between instruments used in different parts of the workflow (e.g. in the printing house, at the customer’s site for inspection, and for certification) is discussed and demonstrated in this paper.

Keywords: color measurement, calibration, color differences, print quality assessment, color management

JPMTR 1101 | 001 Original scientific paper
UDC 655.3.024.062

Received: 2010-10-18
Accepted: 2010-11-03

On developing methods for the identification of relevant paper properties relating to ghosting in heatset offset

Rainer Klein¹, Martina Miletić^{1, 4}, Patrick Cunningham², Gerd Meder³, Harald Großmann⁴
E-mails: rainer.klein@ptspaper.de; martina.miletic@ptspaper.de; gerd.meder@bertelsmann.de; harald.grossman@tu-dresden.de
¹ PTS Heidenau, Germany
² Former PTS, Germany
³ Mohn media arvato, Germany
⁴ TU Dresden, Germany

Abstract

The product quality that can be achieved in offset printing is determined by a multitude of contributing factors. Paper- related influencing variables are functions of the properties of the base paper and coating layer. In addition, print results are affected significantly by many interactions related to the printing process.

Due to the large number of influencing variables of individual properties and in view of their very complex relationships, attempts aimed at quantifying the influencing variables have not yet met with success. The body of knowledge relating to the precise interactions that take place during ink transfer have not yet been thoroughly clarified, and the prerequisites for a scientific solution of offset printing problems such as ghosting and vanishing dots are still lacking.

A European research project has been launched to study the paper-related effects on mechanical ghosting in greater detail. The studies are based on a printing trial in which 18 coated heatset web offset papers (50 to 100 g m^-2) were printed under identical conditions using a “ghosting” printing form, until ghosting phenomena became evident.

Ghosting was evaluated by both visual and metrological means (tool development). The different papers differed clearly in the intensity of ghosting effects. It will be demonstrated that ghosting is caused by a reduction in the area of the printed dots by as much as 10 % on the ghosting side. It will also be demonstrated that ghosting is dependent on the printed image on the non-ghosting side.

The print results form the basis on which to analyze possible interactions between ghosting and important paper properties, the initial results of which will be presented as well.

Keywords: ghosting, web offset printing, runnability, print quality

JPMTR 1103 | 002 Original scientific paper
UDC 655.344:676.22

Received: 2010-11-12
Accepted: 2011-07-05

Process parameters in flexography: effect on UV ink transfer and image quality characteristics

David Bould¹, Timothy C. Claypole¹, David Galton²
E-mails: d.c.bould@swansea.ac.uk; t.c.claypole@swansea.ac.uk; dg@asahi-photoproducts.co.uk
¹ University of Wales, Swansea, UK
² Asahi Photoproducts Ltd, Shenfield

Abstract

An investigation has been performed, whose objectives were to quantify the combined effects of process parameters on UV ink transfer and print quality in flexographic printing. This paper reports the analysis of key factors identified in a factorial designed experiment that builds on previous research into the flexographic printing process. The experiment, in the form of a press trial was performed on an uncoated paper substrate, to assess the effects of speed, plate to substrate engagement, anilox to plate pressure and ink viscosity on image reproduction. Solid density, tone gain and dot circularity were used to assess the extent to which each parameter alters the printed image. Although process parameters, such as dot circularity has been extensively researched previously, these investigations were mainly performed for the offset lithographic printing process. A search of the literature also showed that the research that has been performed into process parameters using flexographic printing, focuses primarily on polymeric or coated paper substrates, where the immobilisation of ink into the substrate is low.

As a result of the investigation, it was concluded that plate to substrate engagement had the greatest effect of all the parameters considered, as it affected all measured properties. Anilox to plate pressure was shown to affect tone gain in the midtone and shadow regions. Speed was observed to have no effect on solid density or dot circularity. It did, however, affect the highlight halftone dots, although no effect was observed for either the midtones or shadow regions. Ink viscosity had negligible effect when considered as a single parameter, but interacted with plate to substrate engagement to have an effect on tone gain in the midtones.

Keywords: flexography, UV ink, circularity

JPMTR 1104 | 003 Research paper
UDC 655.326.1.062

Received: 2010-11-24
Accepted: 2011-07-27

Variable data printing (VDP) quality aspects on fibre based packaging – an elementary print quality study on corrugated board

Marcus Rehberger^{1 ,2 ,3}, Astrid Odeberg Glasenapp¹, Xiaofan Zhang²
E-mails: astrid.glasenapp@innventia.com; xfzhang@kth.se; marcus.rehberger@tetrapak.com
¹ Innventia, Stockholm, Sweden
² Royal Institute of Technology, Stockholm, Sweden
³ Tetra Pak Packaging Solutions AB, Lund, Sweden

Abstract

Variable data printing (VDP) is a technique whereby certain information can be altered in an otherwise static layout with the help of a digital printing system, and in the packaging industry a wide range of applications are possible. Inkjet printing, due to its non-impact printing (NIP) principle, is the most suitable technique to be implemented in packaging production (van Daele, 2005). Only when printing high volumes is inkjet printing much more expensive than conventional printing (Viström et al., 2006). However, the advantages of inkjet printing could still be adopted by another approach.

At Innventia AB, the “HybSpeed Printing” project was initiated to study the combination of a conventional printing process with inkjet printing. The aim of the project is to assess the practicability of attaining high quality VDP at high speed on a variety of packaging papers for corrugated board production. The exploratory trials were conducted on a Kodak Versamark DP5240 in Örnsköldsvik, Sweden, in cooperation with the Mid-Sweden University – Digital Printing Centre (DPC). Nine different substrates, white top and pure white liner, single-coated, double-coated, kraftliner and testliner were printed at a speed of 2 m s^-1.

Rehberger et al. (2010) described in an earlier study that high-speed inkjet printing at 5 m s^-1 has only an insignificant influence on the print quality. In this article, the influence of paper properties is discussed and it is shown that the paper quality has a considerable influence on the print quality. All paper qualities led to an acceptable print result at a medium print resolution. Speed is the most important factor for inline implementation of inkjet, but the tests revealed that the paper properties are most decisive for good print quality.

Keywords: hybrid printing, inkjet, variable data printing, packaging

JPMTR 1102 | 004 Original scientific paper
UDC 655.32.066.25

Received: 2010-11-02
Accepted: 2011-07-05