Effect of Sheet Temperature on Thickness Distribution of the Thermoformed Hemispherical Dome

The thermoforming process is being used to process polymer sheets into numerous components for decades. A polymer sheet is first transformed into a rubbery state by the provision of heat and then deformed it into the required shape by the application of load (pressure, vacuum and contact thermoforming). Among all processing parameters, sheet temperature is the crucial one governing the material behaviour during the processing. However, many researchers have simplified the process by assuming no change in the thermal state of the process during the deformation. Since polymer behaviour is highly temperature-dependent, the assumption of isothermal deformation is not adequate. There is a need to investigate the effect of sheet temperature on process output. The presented study aims to study the effect of sheet temperature on the thickness distribution of the thermoformed product. Numerical investigations on contact thermoforming of transparent hemispherical domes of height 55 mm were simulated. Two processing conditions were simulated, one with constant material properties and other with temperature-dependent material properties. It was found that temperature dependency has a significant effect on the process output and must be incorporated for realistic results.