A network theory based approach predicting the flow through barrier screws in combination with grooved plasticizing barrels
Sprache des Titels:
AIP Conf. Proc. 2884, 110006 (2023)
Barrier screws are widely used in industry for various applications such as pipe extrusion, extrusion blow molding and injection molding. They exhibit improved melting performance compared to standard screws and are frequently used in combination with grooved feed zone barrels for increased specific throughput, resulting in higher pressures along the extruder. To reduce the pressure in the feeding zone, the grooves can be extended into the plasticizing and barrier zone, known as HELIBAR® concept. This additionally enables exchange of material between screw channels and hence leads to an improved thermal and material homogeneity of the polymer melt. Despite its industrial relevance in high performance extrusion, modeling the processing behavior of this concept has attained little attention. In this work, we present a network-theory based approach to predict the polymer melt flow and pressure distribution in barrier sections with grooved plasticizing barrels. In this approach the screw is discretized into small segments represented as elements for each of the two parallel screw channels. These elements locally describe the throughput-pressure relationship being connected via nodal points. The flow over the barrier flight and the leakage flow over the main flight is described by cross-channel elements arranged perpendicular to the main channel. Finally, to model the flow in the barrel grooves additional elements aligned in the direction of the grooves are introduced, applicable for both helical and axial barrel grooves. The obtained flow network is solved via nodal analysis. This fast-computing procedure enables, for the first time, systematic investigations of the influence of barrel grooves in the plasticizing zone on the axial pressure profile and the pressure gradient between melt and solid channel. Comparing predicted pressure profiles with experimental data proofs the suitability our proposed methodology.