| 摘要 |
PURPOSE:To certainly perform undercut treatment and to miniaturize a mold by a method wherein a core forming an undercut to the inner peripheral surface of a molded product is constituted of a plurality of core pieces to be formed into a cylindrical shape and the respective core pieces are made inwardly movable so that one core piece can be received in the other core piece. CONSTITUTION:The core inserted in a cavity is constituted of core pieces 6, 16 and fine groove parts for fanning, for example, shading limes to the inner peripheral surface of a molded product are formed to the outer surfaces of the core pieces 6, 16. Tapered protruding surfaces 6b, 16b are formed to the outer surfaces of the core pieces 6,16 and recessed parts 16e are formed to the inner surfaces of the core pieces 16. At the time of release, first ejector pins are brought into contact with the protruding surfaces 6b to move the core pieces 6 inwardly and subsequently separated. Second ejector pins are brought into contact with the protruding surfaces 16b and the core pieces 16 are moved inwardly while the core pieces 6 are received in the recessed parts 16e. Therefore, the movement in an axial direction is eliminated and the dimension in the axial direction can be reduced. |
