MOLD DESIGNING METHOD AND APPARATUS

摘要

When a molten plastic material is molded with a mold, it is necessary to open the mold after a sufficient cooling time but the amount of production per unit time is restricted by this cooling time. When a mold is opened without being cooled sufficiently, the plastic material thermally shrinks and is deformed greatly. In such a case, the deformation of the plastic material is grasped, and the mold is designed taking the deformation into consideration, whereby a molded product of designed dimensions and shape is obtained even when the cooling time is shortened. In order to grasp the deformation, a finite element method is used. The mold is designed considering the hydrostatic deformation of the molded product when a liquid material is placed in the product. In a method of designing a mold for molding a resin container, comprising the steps of molding previously estimating the deformation of a molded resin container due to the thermal shrinkage taken out from the mold, designing the mold with the estimation, and taking out the molded resin container from the mold before the resin sufficiently is cooled, in the case of a container having an in-mold label portion, the portion has a label-laminated structure, and therefore the deformation of the resin container due to thermal shrinkage cannot be estimated in the same manner as that of a resin container having no in-mold label portion. In such a case, a deformation simulation is carried out by adding parameters including at least the thermal conductivity and linear expansion coefficient to the data on the material of the label. The thermal shrinkage deformation simulation is carried out by a finite element method (FEM). This enables the amount of production per unit time to be improved, and the designing of a mold to be done not by experience.