An investigation of initial polymer sheet heating processes during intelligent thermoforming

The current investigation focused on the heating model development of precision thermoforming concept related to the zone-heating technique. During the study, the numerical model was developed to predict the heated polymer sheet temperature distribution. Two improvements of model accuracy from the previous works were made. First, the energy lost from a heated polymer sheet to the surrounding environment via radiation was taken in to account. Therefore, the net radiation method was applied to determine the incident radiant energy on the polymer sheet. Second, the new comprehensive view factor was applied in the new model. The view factor simplifications embedded in previously developed models are of limited applicability to the target precision thermoforming concept. The numerical results from the newly developed model showed the accuracy improvement in comparison to the previously developed model that neglected the energy lost to the surrounding environment.;The numerical model was tested with four heater setting patterns. The heater patterns were consisted of a quarter heater symmetric, x-axis heater symmetric and non-symmetric settings. In addition, the infrared camera was used for the temperature measurement. The comparisons between the numerical and experimental results were presented. The numerical results showed very good agreement with the experimental results.;Optimization cases involving desired uniform and non-uniform sheet temperature distribution examples were presented and compared to the experimental results It was also shown that the orientation and the number of heater elements could significantly influence the ability to realize a desired sheet temperature distribution.