Injection molding method

Details Injection molding method Injection molding method

1994-08-09

1995-09-19

Heitbrink, Jill L.

Plastic and nonmetallic article shaping or treating: processes

Mechanical shaping or molding to form or reform shaped article

Shaping against forming surface

26432813, 425589, B29C 4556

Patent

active

054513634

ABSTRACT:
An improved injection molding method comprising, tightening an injection molding die with a die tightening force lower than that corresponding to a conventionally rated pressure, injecting a molten resin in a die cavity with an injection molding pressure of which intensity is determined corresponding to the die tightening force so that a gap is formed so as to permit only gas to flow outside of the die cavity via the gap, after completion of injecting temporarily interrupting injection molding so as to release a part of the injection molding pressure from the die cavity so as to maintain the reduced injection molding pressure in the die cavity in the uniformalized state, and raising the die tightening force up to a level corresponding to the rated pressure, and moreover, raising the injection molding pressure in the die cavity. Since a molten resin is injected in the die cavity with a low intensity of injection molding pressure with a low corresponding die tightening force, and moreover, the injection molding pressure is held in the die cavity in the uniformalized state before it is retained in the die cavity, a molded article having a small thickness and a large projected area can easily be produced without any occurrence of a malfunction such as warpage or the like.

REFERENCES:
patent: 4707321 (1987-11-01), Segawa et al.
patent: 5002706 (1991-03-01), Yamashita
patent: 5176859 (1993-01-01), Leffew
patent: 5354525 (1994-10-01), Fujimoto

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