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Raisio, Finland

Tag C.-M.,Forest Pilot Center Oy | Tag C.-M.,Abo Akademi University | Toiviainen M.,VTT Technical Research Center of Finland | Juuti M.,VTT Technical Research Center of Finland | And 2 more authors.
Nordic Pulp and Paper Research Journal | Year: 2012

In the present study, near-infrared sensors are used to investigate moisture variations on paper in the heatset web offset printing process. The moisture content was determined from both non-image and image printed areas at multiple locations along the printing line. The amount of water based liquid (fountain solution) transferred to the two studied areas as well as the internal moisture content of the paper was investigated in terms of near-infrared absorbance response. In order to achieve absolute moisture content estimates,the sensors were calibrated for the respective measurement regions. It was found that the moisture content was higher in the areas with printing ink compared to those without. The heatset drying had a stronger moisture drying effect on the nonimage areas. The tests were performed in both a laboratory and a full-scale heatset offset printing environment.

Oksman A.,University of Eastern Finland | Kuivalainen K.,University of Eastern Finland | Peiponen K.-E.,Forest Pilot Center Oy | Tag C.-M.,VTT Technical Research Center of Finland | And 5 more authors.
Optical Engineering | Year: 2011

Gloss of a product, such as print gloss, is mainly inspected with conventional white light glossmeters both at laboratory or production facilities. However, problems occur in conventional gloss measurement when the inspected surface is vertically moved in the plane of incidence and reflection or when the measurement area is small or curved. For a partial solution to these problems, we have previously introduced diffractive optical element-based glossmeters (DOGs) for the gloss inspection in laboratories and off-line use. We present a new construction of DOG, termed μDOG 1D, for the one-dimensional on-line print gloss measurement, in the form of the reflectance determination normal to the surface. The function of the glossmeter is demonstrated by laboratory tests and on-line measurements at a heat-set web offset printing machine. It is shown that gloss (i.e., normal reflectance) and minute gloss variation of papers and prints can be measured at the printing line using the glossmeter. This glossmeter is expected to be useful in real-time monitoring of the gloss and surface-specific absorption not only in the printing industry but also in inspection of products in other industrial sectors, such as metal finishing, laminating, paper, and construction materials manufacturing. © 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

Tag C.-M.,Forest Pilot Center Oy | Rajala P.,Saimaa University of Applied Sciences | Toiviainen M.,VTT Technical Research Center of Finland | Juuti M.,VTT Technical Research Center of Finland | And 2 more authors.
Applied Thermal Engineering | Year: 2013

The aim of the study was to explain the transportation of liquid (fountain solution) during transfer to coated paper in the heatset offset printing process, together with the subsequent drying of the printed paper, by using statistical and experimental methods. A coating dispersion, applied as a single coating onto a fine paper substrate, was formulated using a narrow fine particle size distribution natural ground calcium carbonate pigment and a styrene acrylic binder. The moisture variation in the paper during printing was monitored by using online multipoint sensors based on near-infrared diffuse reflectance spectroscopy. Based on the results, a simulation model was created to determine the transfer of liquid thin films in the printing units, the evaporation in the printing units, followed by liquid absorption and evaporation in the heatset offset drying process. An accurate simulation depends on precise determination of the different process parameters that influence these factors. The absolute liquid/moisture amount transferred to the paper showed an increased trend as the paper passed through the application nips, though the proportion varied due to limited capillary absorption capacity properties of the paper. The background evaporation in the printing nips was evaluated with the simulation model as well as the drying stages in the dryer including surface and bulk condensation followed by rapid evaporation and cooling. © 2012 Elsevier Ltd. All rights reserved.

Silfsten P.,University of Eastern Finland | Dutta R.,University of Eastern Finland | Paakkonen P.,University of Eastern Finland | Tag C.-M.,Forest Pilot Center Oy | And 3 more authors.
Measurement Science and Technology | Year: 2012

Absolute reflectance data were measured with a spectrophotometer in the visible and near infrared (NIR) spectral range. The specular reflectance data in the NIR were used for the assessment of the surface roughness of magenta, yellow, cyan and black prints on paper. In addition, surface roughness data obtained from the prints with a mechanical diamond stylus, an optical profiling system and the spectrophotometer are compared with each other. The surface roughness obtained with the aid of the spectrophotometer data suggests a smoother surface than when measured with the diamond stylus and the optical profiling system. The gloss of the prints can be obtained from the absolute specular reflectance spectra in the spectral region of visible light. It is shown that specular reflection data at a fixed wavelength in the NIR are useful also in the interpretation of gloss in the visible spectral range, but using an unconventional grazing angle of incidence. © 2012 IOP Publishing Ltd.

Tag C.-M.,Forest Pilot Center Oy | Toiviainen M.,VTT Technical Research Center of Finland | Juuti M.,VTT Technical Research Center of Finland | Gane P.A.C.,Aalto University | Gane P.A.C.,Omya Development AG
Measurement Science and Technology | Year: 2010

Dynamic analysis of the water transfer onto coated paper, and its permeation and absorption into the porous structure were studied online in a full-scale heatset web offset printing environment. The moisture content of the paper was investigated at five different positions during the printing process. Changes in the moisture content of the paper were studied as a function of the web temperature, printing speed and silicone application in the folding unit positioned after the hot air drying oven. Additionally, the influence of fountain solution composition on the pick-up by the paper was investigated. The water content of the fountain solution transferred to the paper from the printing units was observed as changes in near-infrared absorbance. A calibration data set enabled the subsequent quantification of the dynamic moisture content of the paper at the studied locations. An increase in the printing speed reduced the water transfer to the paper and an increase in web temperature resulted in a reduction in the moisture content. An increase in the dosage level of the water-silicone mixture was observed as a re-moistening effect of the paper. Differences in the drying strategy resulted in different moisture profiles depending on the type of fountain solution used. As a conclusion, the near-infrared signal provides an effective way to characterize the moisture dynamics online at different press units. © 2010 IOP Publishing Ltd.

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