A comprehensive method for the assessment of the thermoformability of thermo plastic sheets is presented in this paper. The method, which can be considered as being applicable towards a needed standard, includes the characterization of extruded sheets, the heating phase, and the forming stage plus the study of formed parts. A key feature of the method is the use of a cylindrical negative cavity mold with a movable bottom plate; the device is referred to as a VARIMOLD. An exploratory experimental analysis conducted on sheets of high impact polystyrene (HIPS) in terms of material displacement and deformation illustrates several aspects of the method.
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