INJECTION MOLDING METHOD USING VOID INSERTION PIN AND MOLD FOR INJECTION MOLDING

Japanese Patent JP3437214

B2

PURPOSE: To obtain by injection molding a resin molded article having an excellent appearance wherein a defect such as a shrink mark due to shrinkage of resin is not made on the surface of a large-thickness part, and made up of the large-thickness part and a small-thickness part.
CONSTITUTION: A void insertion pin 40 in the fore end of which a gas releasing part 44 tapered to be pointed is provided is provided at least at one place of a cavity 30 corresponding to a large-thickness part wherein a phenomenon of a shrink mark tends to occur. After molten resin 50 is full-shot into the cavity 30, a pressure gas is sent into the molten resin 50 from a pressure source 60 through the fore end of the void insertion pin 40, so as to induce a void neucleus 51. The void neucleus 51 grows to a void 52 of dimensions corresponding to the amount of the shrinkage of the molten resin 50 accompanying cooling and setting thereof. When the inside of the void 52 is made to communicate beforehand with the open air by operating a selector valve 64 on the occasion, the air is sucked into the void 52 by a negative pressure caused by the shrinkage. Since the shrinkage of the volume of the molten resin 50 is absorbed by the growth of the void 52, a defect such as the shrink mark does not occur on the surface and a resin molded article having little internal stress is obtained.

JPS5812714	CONTROLLER FOR TEMPERATURE OF MOLD
JP2699189	PROBLEM TO BE SOLVED: To reproduce or impart contrast of a squeezed pattern

Kinzuka Iizuka
Hiroshi Aida
Hisato Sato

JP13619393A

August 18, 2003

June 07, 1993

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Nippon Steel Chemical Co., Ltd.

B29C33/38; B29C45/00; B29C45/17; B29C45/26; B29C45/34; (IPC1-7): B29C45/00; B29C45/26

JP59220338A
JP63165114A
JP5293854A
JP516177A
JP447517U
JP619126B1

Wataru Ogura

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