Computer prediction of cycle times during rotational molding of plastics

A computer simulation program has been developed for the rotational molding of plastics. The predictions obtained from this program in terms of heating/cooling rates and overall cycle times have been compared with experimental molding trials with a range of plastics. It is shown that the computer model predicts accurately the real situation for a wide range of processing conditions. In particular, the program allows the effects of oven efficiency, mold material, mold wall thickness, and molded part thickness to be assessed quantitiatively. The article presents information on heat transfer coefficients that are applicable during rotational molding and typical cycle times for a wide range of process conditions.