| 摘要 |
PURPOSE:To control generation of a defective molded product effectively by preventing generating of gas accumulation between a core and cover, by a method wherein the tip of a pin is brought close to the core by inserting a vent pin advanceably and retreatably into a vent hole and the pin is pulled out of the cover material directly before completion of injection of a cover molding material. CONSTITUTION:Vent pins 13 whose diameters are a little smaller than the inside diameters of vent holes 12 bored at the deepest part of a cavity 2 are inserted advanceably and retreatably into the vent holes. When a cover material resin 5 is injected within the cavity 2 after a core 3 has been held by holding pins 4 and the vent pins 13, the resin 5 is converged upon the circumference of the vent pin 13. Then when the pin 13 is pulled out of the resin up to the inside of the cavity simultaneously with completion of the injection of the resin 5, gas 10 left within the inside communicates with the outside and the resin flows from a part close to the core 3 so as to fill out a space left after pulling out of the pin 13. Consequently, the gas can be vented completely from the cavity 2 without clogging the vent hole 12 by the resin itself. |
