| 摘要 |
PURPOSE:To mold a disklike molded piece such as a magnetic disk board in which a sectional shape near the radial center is scarcely formed to be recess even if a sink occurs due to a molding shrinkage by molding the radial sectional shapes of two opposite mirror faces of a cavity in recess state. CONSTITUTION:Molten synthetic resin is injected through a spool bush 6 and a central gate 7 into a disklike cavity 5 formed between mirror face bushes 3 and 4 associated in stationary and movable dies 1 and 2 from an injection molding machine. Here, the faces for forming the cavity 5 of the bushes 3, 4 associated in the dies 1, 2 are formed in smooth recess shape of radial sectional shape. The degree of the recess shape, i.e., the depth (t) of the recess face may be suitably selected according to the injection molding conditions, mold temperature, and desired board shape. A file board or a projection profile board can be obtained even if a sink occurs due to a molding shrinkage in cooling and solidifying steps in case of molding by varying the degree. |
