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Determining the operational settings for the heating equipment in thermoforming is still mainly done by trial and error as well as personal experience. Depending on the type of IR heating equipment, these settings can be the consumed electrical power or the desired temperature of the heating elements. In this study, a workflow is developed, applied and validated to characterize the IR heating equipment and to determine the optimal heating strategy. The workflow starts with an on-site equipment/machine characterization, which takes all machine and environment parameters into account. This approach results in the optimal heater setting and heating duration in order to obtain a through thickness temperature distribution which lies within a predefined forming range. The proposed methodology is universally applicable as it can deal with different types of sheet material and thicknesses. Moreover it can be applied to any type of IR heating element (halogen, metal foil, ceramic or quartz). Moreover, the methodology can easily be implemented in an industrial environment. Additionally, an estimate for the thermal efficiency of halogen heater equipment can be determined.

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Within the present study the elastic response of a flexible open cell polyurethane foam was studied by means of experimental compression tests and finite element (FE) modelling. The compression tests revealed a pronounced sample size effect which was taken into account using an analytical model. In order to eliminate the sample size and damage effects, a minimal sample size of at least 50 times the cell size was necessary in the case of the flexible foam. Surface evolver software was used to model the open cell foam structures. The FE unit cells are based on the well-known Kelvin cell and the more complex Weaire-Phelan cell topology. In both cases the cross sectional shape of the cell edges was completely determined by the minimisation of the surface energy. The thus build FE-models possess a good resemblance to real open cell foam structures. The influence of relative density and shape anisotropy on the elastic properties of the cellular structures was analysed using the FE-models.