Online real-time acquisition for transient temperature in blow molding

Abstract

In blow molding, the temperature is an important parameter which influences the process, cycle times, and part properties, etc. In the current work, a PC-based temperature acquisition system, including hardware and software, was developed to measure the transient temperatures of an extrusion blow-molded part during its cooling and solidification, and of a reheated preform in stretch blow molding (SBM). Two issues were addressed. Firstly, the thermocouples in the acquisition system were specially designed by the authors to allow for their penetration into the wall of the cooling part or reheated preform. Secondly, in order to measure the temperature of reheated preform as it rotates, a special brush mechanism was designed. The acquisition system was tested through a series of experiments on industrial blow-molding machines under different conditions, such as die temperature, blowing pressure, and blow mold material in extrusion blow molding, and the kind of heating lamps and their voltage settings in SBM. The ability of fast and repeatable online measurement of transient temperature profiles using the acquisition system should prove to be helpful to better understand the molding phenomena, to validate the numerical simulation results and to derive optimum processing parameters for blow molding.