• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.32 no.2
• /
• pp.26-34
• /
• 2000

Understanding the nip geometry and heat transfer phenomena of soft nip calenders, which has been used in the production of newsprint and coated papers for many years, is very important since improper setting of soft nip calendering conditions causes deterioration of paper quality and productivity. In this study theoretical analysis on nip pressure and heat transfer phenomena in the nip of soft nip calenders has been made. The variables examined were calendering pressure, surface temperature of the heating roll, nip residence time and ingoing sheet moisture, By measuring nip widths and maximum nip pressure with Prescale film at a normal temperature, accurate line load has been obtained. With this line load, nip pressures at different temperature and nip widths were calculated. Results showed that as temperature increased, nip widths increased and nip pressures decreased. Equations derived for the heat conduction phenomena in soft nip calender nip were derived based on the semi-infinite plate and finite difference method and were used for the analysis of heat transfer within the nip. Temperature profiles in z-direction of paper within the nip were obtained. Finite difference method allowed more accurate analysis of the heat transfer in the calender nip. In this study newsprint and coated paper were considered as a single plate and two-layer plate consisted of sheet and coating layers, respectively. Heat trans-fer to paper increased as heated roll surface temperature and nip residence time were increased.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.30 no.10 s.253
• /
• pp.1328-1334
• /
• 2006

In the rolling mills for sheet metal rolling, paper rolling and etc., the impurities of roller surface have crucial effects on the surface quality of the products obtained by rolling. The Roll Cleaner is a device to remove impurities on roller surface during a rolling operation. Nip Pressure means the line pressure interacted between the roll cleaner blade and the roller surface. The nip pressure is the most important parameter which decides the performance of roll cleaner, and it depends upon several factors including the cleaner design and its blade stiffness. This study, first, analyzes the mechanism of the nip pressure generation for a roll cleaner designed commercially, which is an crucial process for effective design of roll cleaners. Second, the technique for the measurement of nip pressure is developed, which is useful to verify the performance of roll cleaners and to setup them properly at factory floor.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.37 no.4 s.112
• /
• pp.32-37
• /
• 2005

To Increase the productivity of a paper machine, the maximization of the machine speed is a kind of simple way As the machine speed increases, more intense wet pressing is required to persist the outlet consistency of press part and reduce the water removal of dryer part. With more intense pressing, there are concerns that the quality of paper will be affected. This study was carried out to evaluate the influence of wet-pressing on internal structure of paper, The nip pressure at the first and third nip in triple nip press was controlled. Paper structures, strength properties and pore properties were evaluated. As a result, first nip pressure more strongly influenced the paper structural properties than third nip pressure in triple nip pressing condition. Because of the high water content and low wet-web strength of paper web in first nip, increasing the first nip pressure induced the incipient crushing of wet-web and then caused a potential of web break during the following coating or printing processes.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.32 no.2
• /
• pp.16-25
• /
• 2000

The influence of four process parameters of soft nip calendering including calendering pressure, temperature, moisture content and nip residence time on bulk, smoothness and tensile strength of newsprints has been investigated. In addition, the effect of basis weights on calendering responses has been examined. Bulk of newsprints decreased and smoothness increased with the increase of the calendering pressure, temperature, moisture content of the sheets and nip residence time. Improvement in tensile strength was observed when low calendering pressure and high temperature of heat-ing roll were employed. Tensile strength of the newsprint, however, decreased abruptly when the calendering temperature and pressure increased above certain levels due to the rupture of sheet structure, which has been verified by SEM. SEM micrographs also showed that it would be possible to maintain the inner bulk while densifying the fibers on the outer surface of newsprint by adjusting the soft nip calendering variables properly.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.34 no.1
• /
• pp.12-21
• /
• 2002

The effect of soft nip calendering variables including pressure, temperature, nip residence time and moisture on newsprint properties was investigated. The change of bulk, opacity, smoothness, and gloss were determined. It was found that the influence of calendering pressure and temperature are more significant compare the Influence of sheet moisture content and nip residence time on newsprint properties. Calendering conditions of 16$0^{\circ}C$ of temperature, 78kg$_{f}$/cm of line load and 4ms of nip residence time were considered to be optimum conditions to obtain reasonable gloss and smoothness while minimizing the loss of bulk and opacity for newsprint.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.34 no.1
• /
• pp.37-45
• /
• 2002

The effect of soft nip calendering variables including pressure, temperature, nip residence time and sheet moisture on the properties of coated papers was investigated. The change of gloss, opacity, bulk and brightness were determined after calendering. Increase of calendering pressure and temperature increased gloss, but it decreased opacity, bulk and brightness of coated papers. Nip residence time and sheet moisture content showed similar effects on these properties. Calendering conditions of 16$0^{\circ}C$ of temperature, 146kg$_{f}$/cm of line load or less were found to provide optimum conditions to obtain reasonable gloss and smoothness while minimizing the loss of bulk and opacity for coated papers.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
• /
• 2002.11a
• /
• pp.81-90
• /
• 2002

Air entrainment of a winding roll with a nip roller was studied numerically. The amount of air entrainment between two rotating rollers was obtained by solving lubrication equation, Reynolds equation, which neglect the existence of a web. However, the numerical model of this study included the web existence, therefore it considered the two lubricating air films between a winding roll and a web and also between a nip roller and the web. The pressure profiles and gap profiles of the two films were obtained by solving lubrication equation for the two air films and force balance equation of the web. Ballooning phenomenon was examined in terms of nip force, wrap angle, web stiffness, web speed, and web tension. This ballooning phenomenon caused by the back flow of the air film blocked by the nip roller. Air entrainment of the two numerical models was compared.

• Journal of the Korean Graphic Arts Communication Society
• /
• v.10 no.1
• /
• pp.23-33
• /
• 1992

The negative pressure distribution curves of the exit of printing nip were obtained by the transducer type tackometer. As the results, found that the elasticity of rubber rollers and pastic viscosity affect to the maximum negative and positive pressure but, the gap of the printing nip didn`t affects to the tack values of ink and ink film thickness. Ink spritting is accured by negative pressure and inks viscoelasticity. And the tack value is affect by properties of the vehicle component in the inks.

• Proceedings of the KSME Conference
• /
• 2008.11b
• /
• pp.2231-2235
• /
• 2008

Thermal performance of fusing system in laser printer is determined by FPOT(First print out time) required and toner fusing quality. FPOT is influenced by the thermal resistance of fusing system between heat source and nip region. Also FPOT is depended by the heat source power and toner fusing temperature. The fusing quality of toner is decided by the temperature, pressure and duration time in nip region. In this study, I have performed thermal analysis for the toner fusing system. Computational simulation has been used to understand the effect of heat source power and printing speed etc. on the temperature distribution of the fusing system. Also in order to predict fusing quality, numerical simulation of the process that paper is continuously supplied to the nip regions were performed. In comparison with the experimental results of the fusing quality vs transferred calory to the toner layer, I could evaluate various fusing condition parameters effected on the thermal performance.

• Journal of the Korean Society for Precision Engineering
• /
• v.28 no.10
• /
• pp.1131-1140
• /
• 2011

A new rotary gravure-offset printing unit is constructed by paralleling a gravure plate cylinder, a blanket cylinder and a impression roller. A Muti-Unit Gravure-Offset Printing Press(MUGOP) equipped with a series of the 3 printing units is utilized for roll-to-roll fine printing. Its core technology is precise over-piling printing of fine patterns. The severe problems of 'slurring' and 'doubling' in typical offset printing are unavoidable, which can be eliminated by applying a soft pad-type blanket cylinder and the unique 'true rolling' technique. Nip pressure between the blanket cylinder and the plate cylinder is measured by the constant pressure control system which equipped with load cells attached on the cylinders' axes. The running circumference of the blanket cylinder is increased to reach the same circumference of the plate cylinder as the pressure increasing, so that the specifications of the blanket cylinder is determined by the relationships of its shore hardness, diameter and nip pressure. When a softer blanket is used, a blanket cylinder of smaller diameter could give higher nip pressure. Realization of the true rolling technique on the MUGOP makes multilayer printing possible as well as fine printing in printed electronics.