Effect of lubrication on contact thermoforming: Thermal aspect

Abstract

The ability to produce the product at a high rate makes thermoforming one of the most practiced manufacturing processes. Depending upon the control required over the product, pressure and contact forming techniques are being used. It is evident that the contact thermoforming process can produce components with controlled thickness distribution. However, contact conditions are crucial in determining process output. Thermal conductance and coefficient of friction contact properties govern the thermal and structural behaviour of raw material during the process. Like other manufacturing processes, lubrications play a vital role, affecting the thermal and structural behaviour of the material during processing. For thin thermoformed products, the thermal state of raw material can be assumed to be isothermal; this is not true for thick thermoformed products. When a thick sheet product gets manufactured, there is always a temperature variation along with the raw sheet thickness, which affects the whole life cycle of the product (deformation and cooling stage). Thus, it is imperative to study the thermal aspect of thermoforming process lubrication. The objective of the presented work is a numerical investigation of thermoforming lubrication. For lubricated and non-lubricated contact conditions, contact thermoforming of hemispherical domes with a height of 55 mm was simulated. Lubrication was observed to have a significant impact on the thermoforming process. It was found that cycle time was reduced by 15 % with the application of lubrication.