Polymer Engineering Center > Research > Axial Flow Between Eccentric Cylinders

In plastic pipe manufacturing, when polymer melt is extruded from a concentric annular die, the pipe wall thickness is not uniform, and specifically, is thicker on the bottom. This is because of the gravity flow of the molten plastic occurring during the long residence in the cooling chamber inside the pipe. For this reason, the die centerpiece (mandrel) is intentionally displaced eccentrically downward , so that the extrudate entering the cooling chamber is thicker at the top. In manufacturing curved hose, the hose is suspended freely from the die. Its curvature is caused by making the die centerpiece eccentric. The extrudate bends away from the thicker side. To obtain a particular hose shape, the die eccentricity must be specifically programmed. This research project results in analytic models for the plastic pipe and curved hose engineers to help control their processes.