Experimental study and numerical simulation of preform or sheet exposed to infrared radiative heating

International conference on Advances in Materials and Processing Technology, DUBLIN, IRELAND, AUG 03-06, 1999International audienceThermoplastic processing like the injection stretch blow moulding and thermoforming processes provide the heating stage with infrared oven. This is a critical stage of the process, as the final part thickness is strongly dependent on the preform or sheet temperature distribution prior to forming. Optimisation of the infrared oven is therefore necessary. Experiments have been conducted in order to characterise the heat source of the infrared emitter and the interaction between the heaters and a semi-transparent PET sheet. An 880 LW AGEMA infrared camera has been used to determine the surface distribution of the transmitted heat flux by measuring the temperature distribution on the surface of the thermoplastic sheet. In addition, numerical simulations of the temperature distribution using control-volume method have been carried out and compared with experimental data

Modeling of Infrared Heating of Thermoplastic Sheet Used in Thermoforming Process

International audienceThermoforming consists of warming a plastic sheet and forming it into a cavity or over a tool using vacuum, air pressure and mechanical means. The process begins by heating a thermoplastic sheet slightly above the glass transition temperature, for amorphous polymers, or slightly below the melting point, for semi-crystalline materials. As the final thickness distribution of the part is drastically controlled by the initial temperature distribution inside the sheet, it is very important to optimise the heating stage. In most of the thermoforming machine, this step is performed using an infrared oven constituted of long waves infrared emitters. The goal of this study is to determine the efficiency of short waves infrared emitters (halogen lamps) for the heating step. The infrared heating of thermoplastic sheets will be modelled following two steps: an experimental setup developed in our laboratory permits to measure the influence of parameters such as heaters temperature, incidence of the radiation, heat transfer coefficient ,.. An 880 LW AGEMA infrared camera is used to evaluate the surface distribution of the transmitted heat flux by measuring the temperature distribution on the surface of the thermoplastic sheet. In addition, a numerical model using control-volume method (software called PLASTIRAD) has been developed to simulate the heating stage. In particular, it takes into account the spectral properties of both heaters and plastic sheet as well as the heaters directivity. Comparisons between experimental data and numerical simulations allow validating the numerical model using different types of emitters and polystyrene (PS)

Modelling of infrared heating of thermoplastic sheet used in thermoforming process

Issu de : AMPT 2001 - International Conference on Advanced Materials Processing Technologies, MADRID, SPAIN, SEP 18-21, 2001International audienceThermoforming consists of warming a plastic sheet and forming it into a cavity or over a tool using vacuum, air pressure and mechanical means. The process begins by heating a thermoplastic sheet slightly above the glass transition temperature, for amorphous polymers, or slightly below the melting point, for semi-crystalline materials. As the final thickness distribution of the part is drastically controlled by the initial temperature distribution inside the sheet, it is very important to optimise the heating stage. In most of the thermoforming machine, this step is performed using an infrared oven constituted of long waves infrared emitters. The goal of this study is to determine the efficiency of short waves infrared emitters (halogen lamps) for the heating step. The infrared heating of thermoplastic sheets will be modelled following two steps: an experimental set-up developed in our laboratory permits to measure the influence of parameters such as heaters temperature, incidence of the radiation, heat transfer coefficient, etc. An 880 LW AGEMA infrared camera is used to evaluate the surface distribution of the transmitted heat flux by measuring the temperature distribution on the surface of the thermoplastic sheet. In addition, a numerical model using control volume method (software called PLASTIRAD) has been developed to simulate the heating stage. In particular, it takes into account the spectral properties of both heaters and plastic sheet as well as the heaters directivity. Comparisons between experimental data and numerical simulations allow validating the numerical model using different types of emitters and polystyrene (PS)

Experimental study and numerical simulation of preform infrared radiative heating

International audienceThe injection stretch-blow moulding process of thermoplastic bottles requires an heating step before forming. An amorphous preform is heated above the glass transition temperature (80°C for the P.E.T.) using an infrared oven. This step is fundamental in order to determine the thickness distribution along the preform height and then insure high quality bottles. Thus, the optimisation of the infrared oven is necessary. Various experiments have been conducted to characterise the heat source and the semi-transparent properties of the P.E.T. Measurements of air temperature inside the infrared oven and air cooling speed have been processed. These parameters have been implemented in control volume software that simulates the heating step. The surface temperature distribution of the preform has been measured using an infrared camera. Comparisons between experimental and numerical results for a rotating preform are presented

Comparison between a numerical model and an experimental approach of preform infrared radiative heating-recent results

2nd International Symposium on Advances in Computational Heat Transfer, PALM COVE, AUSTRALIA, MAY 20-25, 2001International audienceThe injection stretch-blow moulding process of thermoplastic bottles requires a heating step before forming. An amorphous preform is heated above the glass transition temperature (80 degreesC for the P.E.T.) using an infrared oven. This step is fundamental in order to determine the thickness distribution along the preform height and then insure high quality bottles. Thus, the optimisation of the infrared oven is necessary. Various experiments have been conducted to characterise the heat source and the semi-transparent properties of the P.E.T. Measurements of air temperature inside the infrared oven and air cooling speed have been processed. These parameters have been implemented in a control volume software that simulates the heating step. The surface temperature distribution of the preform has been measured using an infrared camera. Comparisons between experimental and numerical results for a rectangular sheet and a rotating preform are presented

Comparison between a numerical model and an experimental approach of preform infrared radiative heating-recent results

2nd International Symposium on Advances in Computational Heat Transfer, PALM COVE, AUSTRALIA, MAY 20-25, 2001International audienceThe injection stretch-blow moulding process of thermoplastic bottles requires a heating step before forming. An amorphous preform is heated above the glass transition temperature (80 degreesC for the P.E.T.) using an infrared oven. This step is fundamental in order to determine the thickness distribution along the preform height and then insure high quality bottles. Thus, the optimisation of the infrared oven is necessary. Various experiments have been conducted to characterise the heat source and the semi-transparent properties of the P.E.T. Measurements of air temperature inside the infrared oven and air cooling speed have been processed. These parameters have been implemented in a control volume software that simulates the heating step. The surface temperature distribution of the preform has been measured using an infrared camera. Comparisons between experimental and numerical results for a rectangular sheet and a rotating preform are presented