Over the past several decades, various high-performance screws have been developed to optimize the extrusion process for output and melt quality. Due to their complex geometries, however, some of these high-performance screws are still not properly understood and their current designs offer potentials for optimization. This research project investigated the operation of so-called wave-dispersion zones that were implemented to allow the extruder to operate at higher output rates without causing excessive temperatures and irregularities in the discharge. The term wave-dispersion screw refers to extruder screws with functional zones consisting of two or more parallel screw channels that oscillate cyclically in depth over a plurality of cycles (Figure 1). The adjacent channels are separated by a barrier flight that has a constant clearance in the case of double-wave screws. For energy-transfer screw, in contrast, the barrier flight is selectively undercut relative to the main flight to allow the dispersion of solid polymer fragments and molten polymer. This special design allows the high-performance screw to provide better melting, metering, and mixing characteristics as compared to conventional extruder screws.
Forschungs-