Thermal analysis of the heating stage of the thermoforming process

Abstract

Thermoforming is one of the most utilized polymer processing technique, where heated sheet polymer sheets are transformed into useful products. These sheets are usually deformed at a temperature higher than the glass transition temperature of the polymer sheet. The physical and mechanical properties of the sheet change significantly at this temperature. Therefore, forming temperature is the key parameter governing the process output, and by monitoring it, process parameter can be decided for higher quality output and minimum rejections. Temperature monitoring usually carried out using sensors and thermal imaging system, which demands open access of the surfaces to be monitor. In the case of closed forming setups use temperature, monitoring devices are favorable. In order to cope with the mentioned scenario present study proposed to use finite element analysis for temperature monitoring. The objective of the present study is to investigate the heating stage of the thermoforming process for Poly methyl methacrylate (PMMA) sheet just prior to deformation carried out in close forming setup. Numerical studies were performed to study the temperature distribution across the sheet during its heating. In order to validate the proposed numerical model, experimental investigations were carried out, and good agreement was found between simulated and experimental result. The results obtained from the present study could be useful to determine the required process parameters such as deformation pressure. Moreover, the heating stage could be optimized to reduce energy consumption and cycle time.