| 摘要 |
PURPOSE:To moderate mechanical precision required for a mold and mold a disk base with a high precision by a method wherein resin is injected into a cavity of the disk base mold, a columnar movable member is inserted thereafter to the middle in the direction of thickness, and after release, a resin piece left in the part is removed, so as to form a center hole. CONSTITUTION:The fore end of a sprue bush 5 of a mold is made to project into a molding cavity 4 and a metal plate fitting recession is formed in a disk base by a fore end face 5a. A circular recession 5b is formed on the fore end side of the sprue bush 5. A ring-shaped core 11 for molding a bulging part, which has a larger diameter than the sprue bush 5, is disposed at a somewhat recessed position in the central part of a movable half 3, and/on the inner circumference side thereof, a columnar movable member 12 having an outside diameter corresponding to the inside diameter of the center hole is provided movably forward and backward. A stamper 7 is fitted to a fixed half 2, and after resin is injected, the movable member 12 is made to advance to a position just a little before its coming into contact with the sprue bush 5. After release, a resin piece 22 covering the center hole 21 is removed by cutting. |
