A preliminary evaluation of single screw paste extrusion

A mathematical model has been proposed for a flooded single screw that brings together paste rhelogy and a model of screw extrusion developed from methods for frictional solids flow. Here experiments have been performed to compare the results with this existing model. A Haake industrial single screw extruder with a hydraulic feeder was employed for the set of experiments. Two kinds of material were used: plasticine and pottery clay. Screw speed, hydraulic feeder pressure and the temperature of the barrel were controlled in order to measure the torque of the rotating screw and pressure of the material before entering the die zone. Plasticine and clay show markedly different responses to changes in screw rotation rate. For plasticine, increasing the rotation rate increases the pressure generated. For clay, increasing the rotation rate decreases the pressure generation. These effects are predicted by the model, although there remain problems in dealing with non-constant channel depths of screw. Future work will aim to further develop the model to deal with this important issue.