| 摘要 |
PURPOSE:To prevent the deformation of an article to be formed and the accuracy defects of an outer configuration by providing an outer peripheral groove which enables the complement of a resin material equivalent to the molding contract rate in a large diameter part of the article formed in the central part of a cavity wherein a large contract rate occurs during the period of molding. CONSTITUTION:On the outer peripheral surface of a center pin 9, an outer peripheral groove 9a is formed, which has a volume equivalent to the molding contract rate of a resin material of a central part 5b at the large diameter part of a truncated cone in the central part of a cavity 5 in a state of clamping, and on the tip part, an extension pin 11 is formed which comes into the inside of a sprue part 8. When a resin material is injection supplied in the cavity 5, there is formed a turboimpeller 1 having a plurality of blades 1a, a central part 1b, and a cylindrical recess 1c and a truncated conical sprue 1d. During the period of molding, even when the contract rate becomes large in the large diameter part of wall thickness of the turboimpeller 1, since the resin material in the inner part of the outer peripheral groove part 9a serves to complement the contracted quality, thereby preventing accuracy defects due to the enlargement in the inner diameter of cylindrical recession 1c of the turboimpeller 1. |
