Heat conditioning modelling of thermoforming process: comparison with experiments
Résumé
The goal of this study is to improve the efficiency of infrared heating ovens used in the thermoforming process. The heat conditioning of thermoplastic sheets before forming consists in heating up thermoplastic sheets above the glass transition temperature of the polymer. The thickness distribution of the final product is strongly dependent on the initial temperature distribution inside the sheet. Well-calculated process parameters during the heat conditioning step will allow improvements in, for example, cycle-time reduction. For that, we use different electric heaters that operate in different infrared ranges as: long, medium and short infrared wavelengths respectively. Thermoforming machines are generally equipped with ceramic heaters that operate in long infrared wavelengths. Recently, halogen lamps that are short wavelengths heaters have started to be employed in thermoforming applications. So, an experimental infrared heating setup has been developed in order to compare the different kinds of heaters and the efficiency of lamp reflectors. The temperature of each infrared heater in the oven is controlled independently in order to optimise the surface temperature distribution of the thermoplastic sheet. For that, an 880 LW AGEMA infrared camera has been used to measure the temperature distribution of different thermoplastic sheets. We have chosen in this study the most commonly employed polymers in thermoforming which are: ABS and PP used for thin gage sheets. Numerical simulations using software based on control-volume method have been performed and compared with experimental data.
Domaines
Génie des procédés
Origine : Fichiers produits par l'(les) auteur(s)
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