Malo, A., Benrabah, Z., Thibault, F., and Bardetti, A., "Numerical Modeling of Preferential and In-Line Heating of Semi-Transparent Thin Polymers in Stretch Blow Molding and Thermoforming Processes," SAE Technical Paper 2013-01-1393, 2013, doi:10.4271/2013-01-1393.
The heating stage is of primary importance in stretch blow molding and thermoforming processes. Computational methods using the finite element technique for modeling the radiation heating stage of thick gauge plastic preforms and thin gauge, roll-fed plastic sheets are presented and discussed. The theoretical approach as well as the experimental validation are also presented.For stretch blow molding, the energy absorbed by the preform is adjusted by accounting for the selective heating process. An oriented preform is heated from two sides on a mandrel with a pre-defined pattern. This results in a controlled, optimized and uniform material distribution on the bottle which is essential to meet the growing needs of the packaging industry. For this purpose, preferential heating combined with the use of universal preforms produces a range of standard bottles having excellent aesthetic features without sacrificing the physical properties.For thermoforming, the proposed approach takes into account the dynamic effects of sag and the displacement of the sheet inside the oven. The volumetric energy absorption representing a heat generation term, which is critical in the case of semi-transparent materials, is also integrated by using Beer's absorption law.