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CONSTRUCTION AND SIMULATION Optimisation of the Simulation of Rubber Extrusion dies by means of the Integration of empirically determined characteristic Maps

Von Prof. Dr.-Ing. Christian Hopmann, Clemens Wiesel, Uwe Nillius, Malte Schön, Prof. Dr.-Ing. Andreas Limper, Institut für Kunststoffverarbeitung an der RWTH Aachen, Germany Prof. Dr.-Ing. Volker Schöppner, Dennis Kleinschmidt, Kunststofftechnik Paderborn, Universität Paderborn, Germany 1 min Lesedauer

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Gummiwerk KRAIBURG GmbH & Co. KG

By determining characteristic maps that describe the wall slip as a function of the compound composition and the extrusion temperature, boundary conditions in flow simulations can be determined in such a way that the effects on pressure and temperature distribution in the extrusion process are considered.

Pressure dependence of the contact area between the capillary wall and the rubber compound.(Bild:)
Pressure dependence of the contact area between the capillary wall and the rubber compound.
(Bild:)

hen designing extrusion dies for rubbers, the complex flow behaviour, which is characterised by the presence of rather high wall shear stresses leading to significant viscous dissipation and - in combination with the presence of plasticisers - a tendency towards wall slip, poses a particular challenge. This means that effects such as viscous dissipation, wall slip and swelling affect the design of the die, as these have a significant influence on the surface quality and dimensional accuracy of the extrudates. To understand these phenomena in depth, first the basics of the rubber rheology have to be discussed.