Comparison of surging in conventional extrusion and gear pump assisted single screw extrusion.

摘要

For several decades, process development researches have studied ways to improve extrusion output consistency. Undesirable oscillatory pressure fluctuations, known as surging, can result from several factors including screw design, process parameters or resin feeding. In this thesis work, pressure stability and extrudate dimensions from conventional single screw extrusion and single screw extrusion with a melt pump are characterized. Extrusion grade polypropylene is used as test resin for this study. Experiments were conducted at eight run full and half fractional DOEs and for each run two minutes of data was collected. The effects of melt temperature, extruder speed, die diameter, and gear pump speed were investigated.; The results indicate that according to the standard deviation values obtained, insertion of a gear pump in the extruder resulted in over 50% improvement; while the standard deviation of gear pump inlet pressure was 0.075MPa the standard deviation of the outlet pressure was reduced to only 0.034 MPa. Theoretically, lower variation in output pressure should result in lower extrudate variation. There was only a slight improvement in the consistency of the width and height dimensions of the extrudate with gear pump compared with that of conventional extrusion. Future results might be improved with higher resolution laser micrometer, efficient cooling, and precision puller.