METHOD OF CONTROLLING THE THICKNESS OF AN EXTRUDED PLASTIC ARTICLE

摘要

A method for monitoring and controlling the wall thickness of an extruded profile (12) of heated polymeric material that issues from an extrusion die (18). The die (18) includes a plurality of discrete sectors each having a controllable heat source and a temperature sensing means, and the temperature at each particular sector is controlled and adjusted in order to change the measured thickness corresponding with that particular sector as necessary to provide a desired wall thickness distribution. A characteristic curve for the particular material is provided as an input quantity and involves the relationship between a change in extrusion temperature versus the corresponding change in wall thickness, and that relationship is utilized to effect rapid adjustment of thickness by means of temperature change in order to provide a finished article having the desired thickness profile and without excessive material, to thereby reduce the weight and cost of the extruded article.