Abstract
In this paper, an optimization procedure to decide layouts and shapes of cooling pipe system in plastic injection molding die is developed. Unfortunately in plastic moldings, residual stresses are remained by nonuniformity at the coagulation late and the cooling velocity of molten plastic. Residual stress causes unexpected warps and cracks in plastic products some years after molding. When the plastic materials in the gel state during the solidification process are cooled down uniformly, it is expected that the generation of the residual stress can be reduced. For this purpose, we have tried to optimize the cooling pipe system of plastic injection die, which is the most effective factor to reduce the residual stress.
