Determination of minimum aspect ratio for rigid PVC pipe die

Abstract

In this treatise, an effort is made to determine a minimumaspect ratio for a rigid PVC pipe die. In pursuing that objective,the mechanisms whereby extruders work and how plastics flow throughdies are presented. Following this introduction is a review of thevarious extrusion methods. Next comes a discussion of material datanecessary for the design of a die. In an attempt to link practicewith theory, a theoretical foundation for die design is also considered.A design methodology is then laid down for a rigid PVC pipe die andclarified with an example. Lastly included is an interpretetion oftests run on pipe samples which were extruded on the dies implementedin accordance with the calculations.It is shown that the extrusion volume and the mechanicalproperties of a rigid PVC pipe are related to and can be controlledby the land length. It is also deduced that a minimum die aspectratio exists below which the properties of a pipe deteriorateunacceptably.