Analysis of Heat Transfer in PVC Profiles during the Extrusion Calibration/Cooling Step

Abstract

Abstract The external vacuum calibration of extruded thermoplastic materials is a complex process, which may hinder the production and even the quality of the parts. Process control requires a thorough knowledge and a deep analysis of the heat transfer phenomena between both the part and the calibrator during the cooling phase. This paper initially presents a detailed description of the experimental setting used to qualify and quantify the heat transfer modes. The experimental specimen is a 100-mm wide PVC strip, which represents one of the three sides of the U-profile. The development of physical models to predict plastic part thermal history during the forming process is a major industrial concern because it can reduce tooling development times and costs significantly. In the extrusion processing field, the external vacuum calibration stage often hinders productivity. The present study has been conducted to examine strip cooling phase so as to propose some thermal models for both global and detailed analyses of heat transfer modes. First, a transparent wall calibrator is used to view the behaviour of the extrudate inside the calibrator for a better understanding of the thermal phenomena at work. A second calibrator equipped with temperature sensors makes it possible to assess, using an inverse calculation method, the heat flux transferred from the extruded material to the calibrator as well as the temperature pattern throughout the tool.