| 摘要 |
PURPOSE:To contrive to prevent a sinkmark from developing and consequently to shorten the time required for correcting a mold to a far greater extent by a method wherein gas such as compressed air or the like is forcibly fed in a cavity at the contrived timing during molding. CONSTITUTION:After a molten plastic material is filled into a cavity 3, gas is fed through a passage made in a core pin 4 from the tip of the core pin 4 into the plastic material so as to cool a mold and to contrive to solidify the plastic material in order to be able to mold a molded item equipped with a boss part 10. In the molded item as mentioned above, no sinkmark develops on the surface of the boss part. If the temperature of the gas which is forcibly fed from a gas feeding device 6 to the passage of the core pin 4 is controlled so as to contrive to cool the core pin 4, the shortening of the molding time also results. The timing for forcibly feeding the gas in the passage 8 of the core pin 4 is after the filling of the plastic material. Further, the optimum protruding length of the tip part of the core pin 4 is determined in accordance with the conditions of the molded item such as wall thickness and the like. |
