Prediction of wall thickness distribution in thermoformed mouldings

Polystyrene, polyethylene, polyvinyl butyral and PVC sheets have been vacuum formed into conical and truncated cone shaped moulds in an attempt to predict the variation in wall thickness in the mouldings. It has been found that, for conical moulds, the thickness distribution can be predicted accurately using previously published analysis; for the more practical truncated cone shapes, it was necessary to develop a special equation. This equation predicted wall thicknesses in good agreement with the measured results in four different moulds and could also be used to predict the results reported by other workers.