Modelling the feeding and delay section of single screw extruders with non-isothermal models based on viscosity

When designing single screw extruders to meet high quality requirements, the most important parameters are output and temperature. To be competitive, machine manufacturers must guarantee the production of high-quality products at high output rates with a broad processing window in terms of materials and processing parameters. A single screw extruder must fulfil at least three basic functions: solid conveying, melting, and metering. In the solid conveying section, polymers are fed into the screw via a hopper, compacted into a tightly packed bed, and conveyed. When the melt film thickness exceeds the screw clearance, the melting section starts, and the melt is scraped off the barrel and collected in a melt pool. Calculating the solid conveying capacity of single screw extruders is a subject of international research. The solid conveying models can be divided into two basic classes: friction-based and viscosity-based models. The presentation, will display the non-isothermal calculation of a solid conveying section based on viscosity, using viscous shear forces instead of frictional forces. The advantage of this model is that it does not require a frictional coefficient, which depends on temperature, pressure, velocity, and granular shape, and is difficult to determine in the extruder. Furthermore, a modified drag-induced melt removal model that builds upon that by Tadmor[1], and allows the delay section of a single screw extruder will be presented.