Effect of design and process parameters on nip width of soft calendering

Abstract

Calendering is well known operation in which a material is run between rolls to thin it in to sheets or to produce smooth or glossy finish. An attempt has been made in this investigation to remove the drawbacks in the model of Meijer's and applicable directly to soft calendering, also to make nip mechanics model generalized and applicable, So that it can be applicable where there is roll to roll or roll to plate contact. Also the effect of various design and process parameters on results of soft calendering has been discussed using the data taken from paper industry.

Analysis of Nip Mechanics Model for Rolling Calender Used in Textile Industry

“…Nip mechanics i.e. the speculations of rolling contact mechanics is necessary for a variety of calender geometries (Kanth et al 2016). The benchmark solution for calculating nip width for two homogeneous bodies in contact was firstly given by Hertz (Johnson 1982).…”

“…The contact width for two homogeneous cylindrical bodies in contact according to Hertz is given by (Johnson 1982, Kanth et al 2016…”

“…In the process of calendering, the substrate is pressed between two or more rolls (Hall 1966, Jokio 1999. Calendering is a high speed ironing process which firstly imparts luster that is the final pre-treatment of the textures in the final cycle (Kanth et al 2016). The fundamental rule of calendering is to portrayal the texture with the combined impact of dampness, warmth, and weight until the point when the textured surface turns out to be extremely smooth and light and obtains good quality luster (Hall 1966, Kopitar et al 2014.…”

“…Smoothness and gloss of the texture depend upon the temperature of the rolls and texture, linear load applied, bonding time, the speed of roll, soft roll material and a number of nips (Enomae et al 1997, Kanth et al 2016. The smoothness and gloss of substrate expanded with the increment in the hardness of the roll, as harder roll do not deform in nip width area.…”

Analysis of heat conduction inside the nip of a machine calender for the same and different roll temperatures

“…Dwell time in the nip is determined from the machine speed and nip width. The required smoothness, thickness, and gloss value of paper are obtained through pressure control in the nips and by adjusting the temperature of the heated rolls, thereby making the pressure effect more efficient. Heat transfer between the paper web and calender roll is governed by the thermal conductivity of the paper web and its contact resistance with a solid surface .…”