Winding problems with rotogravure jumbo-rolls

The production and conversion of jumbo rolls presents a challenge to all involved in the production process. This presentation shows that as reel dimensions continue to increase, limits are being reached with regard to engineering and production. This applies to the paper, the core and particularly to winders and printing machine unwinds. The two problems areas, on the one hand crepe wrinkles and bursts in the reel centre when rewinding and unwinding and on the other hand the danger of the core disintegrating in the winder machine unwind, which can have serious consequences, can only be solved jointly by those involved in the whole process. One effective measure will be to use 150 mm cores instead of the 76 mm core for extremely heavy jumbo reels. This will represent an initial decisive breakthrough to improve the situation. Further optimisation in paper making and converting, in core geometry, strength and stiffness as well as in the design of winders and printing machine unwinds will ensure that the manufacture and conversion of jumbo reels meet the requirements posed

Future online concept for roll and sheet production in papermaking technology and process requirements for web handling

The process of on-line converting is discussed as a chance to increase the productivity and quality in roll and sheet converting in paper mills. In this article the technical and process related prospects will be presented on the basis of an exemplary production line (WFC Paper) and transferred into realizable concepts for continuity paper converting.In the case of roll production, the segment of large rolls with standard sizes is very suitable for an on-line-production, and in the case of sheet production the segment of larger lot sizes. In both cases a new machine design with altered functions and a higher level of automation and process control is necessary.These alterations yield diverse requirements for web and sheet handling, which have to be fulfilled for a continuous and high-quality production. All fundamental technologies such as transport mechanics of webs and sheets, winding and stacking mechanics, slitting in length and cross direction as well as measurement and control techniques for the monitoring of converting processes in particular belong to this category. These technologies will be discussed and further tasks for research work will be presented

First-Order Vortex Lattice Melting and Magnetization of YBa2_2Cu3_3O$_{7-\delta}

We present the first non-mean-field calculation of the magnetization $M(T)$ of YBa$_2$Cu$_3$O$_{7-\delta}$ both above and below the flux-lattice melting temperature $T_m(H)$. The results are in good agreement with experiment as a function of transverse applied field $H$. The effects of fluctuations in both order parameter $\psi({\bf r})$ and magnetic induction $B$ are included in the Ginzburg-Landau free energy functional: $\psi({\bf r})$ fluctuates within the lowest Landau level in each layer, while $B$ fluctuates uniformly according to the appropriate Boltzmann factor. The second derivative $(\partial^2 M/\partial T^2)_H$ is predicted to be negative throughout the vortex liquid state and positive in the solid state. The discontinuities in entropy and magnetization at melting are calculated to be $\sim 0.034\, k_B$ per flux line per layer and $\sim 0.0014$~emu~cm$^{-3}$ at a field of 50 kOe.Comment: 11 pages, 4 PostScript figures in one uuencoded fil

Optimized slitting parameters for the shear slitting of paper

Due to the demand for an increasing quality of cutted or slitted products and the requirement of rising productivity in the slitting process, the optimization of mechanical slitting is gaining in importance for the converting industry.In this paper the shear slitting process is analysed theoretically on the basis of a nonlinear orthotropic material law. In a basic investigation the states of stress and strain in the compression phase of the slitting process are discussed. The following application oriented calculations investigate the influence of individual parameters and lead to the suggestion of an optimal cutting tool geometry depending on the material to be cut

Theoretical analysis of shear slitting of paper on the basis of a three-dimensional material law

The slitting and cross cutting as one of the substantial manufacturing methods in paper equipment and paper processing, are characterized in many applications by practice problems, which lead to productivity and quality losses.Analysing the knowledge of shear-slitting shows, that there are great gaps in the fundamental understanding of the slitting procedure as well as in its conversion to mechanical engineering. For this reason our institute carries out a research project to analyse the slitting procedure on a theoretical and experimental basis. The aim of this project is to clear up the correlations of shear-slitting and to derive measures for the improvement of slit quality and blade durability in practice.Because of the complex, three-dimensional state of stress during the slitting process, the problem cannot be solved analytically and the finite-element-method is used to calculate the states of stress and strain. For the modelling of the material behavior of paper, a three-dimensional material law is deduced. The influence of the material law and the cutting tool geometry on the shear slitting process is studied. The achieved results of the FEM-analysis shall be compared to experimental results in later research work