Calendering Of Paper Research Articles

On the effect of paper plasticity in calenders

AbstractThe manufacturing process of paper machines consists of several steps to produce high quality papers. This is done by sequentially lined‐up machines including the head box, the drying sections, the finishing part and the wrapping systems. In the finishing part, the rollers of the paper calender compress the fibrous material involving viscoelastic and plastic deformations. Modern calenders are composed of several roller pairs, each consisting of a soft and a hard roller. The homogenization of the paper density and the refinement of the paper surface is achieved by the compression in the roller pairs. While very high values for the plastic strain occur in the first roller pair, the plastification decreases for the subsequent pairs. Therefore, the force distribution and the occurring vibrations can deviate significantly between the roller pairs. Two main vibration problems are observed in paper calenders caused by the contact and the orthotropic behavior of the paper: wear‐induced corrugation on the surface of the soft rollers and sudden instabilities going along with high vibration amplitudes. In this paper the main focus is placed on a simplified modeling of the paper plastification during the calendering process. The restoring forces are non‐smooth due to the plasticity and additional considerations have to be included for the derivation of the stability problem.

Structural optimization for the avoidance of self-excited vibrations based on analytical models

Self-excited vibrations are a severe problem in many technical applications. In many cases they are caused by friction as for example in disk and drum brakes, clutches, saws and paper calenders. The goal to suppress self-excited vibrations can be reached by active and passive techniques, the latter ones being preferable due to the lower costs. Among design engineers it is known that breaking the symmetries of structures is sometimes helpful to avoid self-excited vibrations. This has been verified from an analytical point of view in a recent paper. The goal of the present paper is to use this analytical insight for a systematic structural optimization of rotors in frictional contact. The first system investigated is a simple discrete model of a rotor in frictional contact. As a continuous example a rotating beam in frictional contact is considered and optimized with respect to its bending stiffness. Finally a brake disk is optimized giving some attention to the feasibility of the modifications for the production process.

Effect of calendering on paper surface properties

Calendering of paper is an industrial finishing process designed to smoothen its surface so as to improve gloss as well as printability. In this article, we describe how calendering affects paper roughness on both microscopic and macroscopic length scales. We also discuss how these modifications relate to the morphology of the fibers composing the paper sheets. The characterization of the surface is carried out using an optical profilometer and two different species of fibers, as well as their mixture, are used. We first show that calendering induces modifications of the surface on all length scales measured and that these modifications are related by straightforward transformations. We also show that these results hold for papers formed from a mixture of fibers.

The compressive response of a stratified fibrous structure

A model for the compressive response of an oriented fiber structure such as paper is derived in this work. The model provides a semi-quantitative description of the stress/strain behavior of a fiber structure. The model accounts for the deformation of fibers during compression, their finite fiber length, their elastic modulus, and their moment of inertia. Using a previously describe micro-indentation technique, the predicted impact of variables used in the model on the compressive response of paper is verified. Results consistent with the model are found including a strong dependence of the tangent modulus on apparent density of the sheet, and a relative insensitivity of the tangent modulus to fiber length. The three stage behavior of the paper compression described by Rodal [Soft-nip calendering of paper and paperboard. Tappi Journal 72 (5), 177–186] was also accounted for in the model.

The penetration depth and lateral distribution of pigment related to the pigment grain size and the calendering of paper

The interaction of ink and newspaper has been investigated and the specific question of penetration of ink into the paper has been addressed with a nuclear microprobe using particle induced X-ray emission. The penetration depth of the newsprint is a critical factor in terms of increasing the quality of newsprint and minimising the amount of ink used. The objective of the experiment was to relate the penetration depth of pigment with the calendering of the paper. The dependence of the penetration depth on the pigment grain size was also studied. To study the penetration depth of pigment in paper, cyan ink with Cu as a tracer of the coloured pigment was used. For the study of the penetration depth dependence of pigment size, specially grounded Japanese ink with well-defined pigment grain size was used. This was compared to Swedish ink with pigment grains with normal size-distribution. The results show that the calendering of the paper considerably affects the penetration depth of ink.

Discussion on “application op electric drive to paper calenders” (Morse) and “electric drive for paper machines“ (Henderson) Boston, Mass., June 28, 1912. (see proceedings for July, 1912)

Discussion on “application op electric drive to paper calenders” (Morse) and “electric drive for paper machines“ (Henderson) Boston, Mass., June 28, 1912. (see proceedings for July, 1912)

Application of electric drive to paper calenders

Motors have been used in paper mills for the last twenty years and have been applied with success to every machine used in the process of making paper. By means of motors it has been possible to study the power requirements of various machines and much useful information has been obtained for the manufacturer of the paper, of the machine, and of the motor. As far as the writer knows, very little of this information has been published and it is the intention of this paper to set forth facts that have been observed and state the possible laws that may be deduced from these facts. This paper is confined to the finishing department of the paper mill and more particularly to the motor drives for three types of paper calenders.

Application of Electric Drive to Paper Calenders

Motors have been used in paper mills for the last twenty years and have been applied with success to every machine used in the process of making paper. By means of motors it has been possible to study the power requirements of various machines and much useful information has been obtained for the manufacturer of the paper, of the machine, and of the motor. As far as the writer knows, very little of this information has been published and it is the intention of this paper to set forth facts that have been observed and state the possible laws that may be deduced from these facts. This paper is confined to the finishing department of the paper mill and more particularly to the motor drives for three types of paper calenders.