US 5,266,247 AGranted

Molding cycle control method of an injection molder

AssigneeKomatsu Ltd.

InventorAkira Yokota

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Abstract

A molding cycle control method of an injection molder includes a flow passage opening and closing mechanism which prevents a flow of a plasticized synthetic resin to be injected, aiming at shortening the time required for each molding cycle and the stability of weight value of molded products. The above-mentioned control method includes the flow passage opening and closing mechanism being closed under the state that the plasticized synthetic resin is injected and filled into a cavity of a mold and is applied with dwelling pressure. Thus, a dwelling process is conducted by the residual dwelling pressure at the mold side and simultaneously a measuring process for a next molding cycle is carried out at the screw side, thereby enabling the time required for each molding cycle to be shortened. Further, with the provision of the flow passage opening and closing mechanism and the check valve at the screw, a definite the predetermined value of resin pressure of the plasticized synthetic resin placed in the cylinder immediately before the injection and during the dwelling can be obtained. Furthermore, since a weight value of a molded product can be obtained through an operation, the injection molder can be controlled to keep constant the weight value of molded products constant.

A molding cycle control method for an injection molder comprising a cylinder with a screw therein and a flow passage opening and closing mechanism which is provided between the cylinder of the injection molder and a gate of a mold, the mold having a mold cavity, the opening and closing mechanism provided for the flow of a plasticized synthetic resin between the inside of the cylinder and the cavity of the mold, the method comprising the following steps:

(a) a pre-injection pressing process wherein after the synthetic resin is plasticized and measured, with the flow passage opening and closing mechanism closed to prevent the flow of the plasticized synthetic resin, a predetermined pushing force is applied to the screw to set the resin pressure value inside the cylinder equal to a predetermined value,
(b) a filling and dwelling process comprising a filling process wherein with the flow passage opening and closing mechanism open to allow the plasticized synthetic resin to flow, the screw is moved forward to inject and fill the plasticized synthetic resin into the cavity of the mold, and a dwelling process to apply a predetermined pushing force to the screw following the filling process, during which the flow passage opening and closing mechanism is closed the filling and dwelling process being conducted to fill a predetermined amount of the plasticized synthetic resin into the cavity,
(c) a measuring process wherein with the flow passage opening and closing mechanism closed to block the flow of plasticized synthetic resin, the screw is rotated and moved backward to measure a predetermined amount of the plasticized synthetic resin for a next molding cycle, and
(d) a suck-back process wherein with the flow passage opening and closing mechanism open to allow the plasticized synthetic resin to flow, the screw is moved backward to lower the pressure of the plasticized synthetic resin located between the gate of the mold and the front end of the screw at its forward movement side.

1 more element

Facts

Application

07/809,557Filed 23 Jan 1992

Priority

JP 2-13476324 May 1990

Granted

30 Nov 1993

Term ends

Not estimatedThe source records don’t support an estimate.

Classification5 codes

B29C 45/57
Means for plasticising or homogenising the moulding material or forcing it into the mould: exerting after-pressure on the moulding material
B29C 45/50
Using screws: axially movable screw
B29C 45/76
Component parts, details or accessories; Auxiliary operations: measuring, controlling or regulating
B29C 2045/5096
Axially movable screw: decompression of the moulding material by retraction or opposite rotation of the screw

Abstract

Claims10