Analysis of shrinkage by dual kriging for filled and unfilled polypropylene molded parts

This paper examines, through holding pressure, packing time, melt temperature, mold temperature and distance from the gate, the effect of molding conditins on the shrinkage of polypropylene and 40% calcium carbonate (CaCO 3 ) filled polypropylene. The shrinkage longitudinal and transvrse to the flow direction were determined using a 127 × 76 × 4 mm thick plaque with a film gate. Marks were made ont he mold cavity to measure shrinkage at various distances from the gate. The results show that holding pressure and packing time are the most significant parameters. Cooling runners, however, could significantly influence local shrinkage values. Calcium carbonate reduces the shrinkage anisotropy as well as the cycle time of the molded parts. Shrinkage models have been developed using dual kriging statistical interpolation techniques and show an excellent fit with experimetnal data.