Contact Analysis for Contact Thermoforming of PMMA Sheet

Abstract

Abstract The ability to produce products with more uniformity in the wall thickness distribution makes contact thermoforming the most suitable optical product processing method. Among all the process parameters, the contact condition significantly affects the structural strength and the optical properties of the product. Thus, it is imperative to investigate the effect of change in the contact conditions on product thickness. Hence, in this study, experimental investigations on contact conditions were performed considering poly(methyl methacrylate) as the sheet material and stainless steel 304 as the punch material. Experiments were conducted to examine the effect of temperature on the coefficient of friction (mechanical contact condition) and the effect of pressure on the thermal contact conductance (thermal contact condition). It was found that the contact conditions change significantly with changes in the operating conditions. Furthermore, numerical simulations were performed, considering isothermal processing and nonisothermal processing with constant and variable contact conditions to identify the effect of the change in contact condition on the product thickness. It was found that the change in contact condition has a considerable effect on the product thickness distribution. This study shows the importance of incorporation of the change in the contact condition for realistic simulations.