An Improvement on Design of Sheet Extrusion Dies

Abstract

On the basis of the method of representative values and the flow pattern, that is, the position of the isobars parallels to the die orifice (PIPDO), the design of dies for the sheet and annular parisons is improved in the present paper. Since this pattern includes the effects of the sloped manifold and the die design for the circular manifold are independent of flow rate and the polymer viscosity, the distribution system of a die gives better uniformity of flow. In the previous study [1] a defect is found, that is, the calculated position of the path of the island area lags behind actual position. This defect is eliminated, and the modified equation is obtained. Another flow pattern, the pressure loss on all flow path is equal (PLFPE), is introduced. The equivalency of the above two flow patterns is proved theoretically. Although the flow uniformity isn’t perfect in the simplified analytical design of dies proposed in the previous paper, this simplified design is still of advantages. Therefore, its design criterion is put forward in this paper.