Plastic and nonmetallic article shaping or treating: processes – With measuring – testing – or inspecting
Patent
1993-11-29
1995-11-28
Heitbrink, Jill L.
Plastic and nonmetallic article shaping or treating: processes
With measuring, testing, or inspecting
2643287, 425145, 425562, 425575, B29C 4570, B29C 4577
Patent
active
054705134
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a device for and a method of molding for an injection molding machine, and more particularly to a device for and a method of molding for an injection molding machine by which fluctuation in weight of an injection-molded resin product is reduced.
BACKGROUND ART
The following methods have been implemented to manufacture molded resin products by a molding device for an injection molding machine, an injection compression molding machine, and an extrusion molding machine:
(1) A method by which resin is molded by moving a screw forwardly along a specified distance to inject resin and controlling a screw drive hydraulic pressure.
(2) A method by which a resin passage is closed and molds are pressurized by a press mechanism or the like, after moving a screw forwardly along a specified distance for injecting resin.
However, in the case of molding a product with a large projection area (that is, a large compression stroke), the molded products have had insufficient strength due to insufficient density or have had variable quality due to a number of flashes, because molded products vary substantially in weight despite the products being satisfactory in dimensional accuracy. In other words, there has been a problem including the following points:
(1) A hydraulic actuator is used to move the screw forwardly and its position is controlled in accordance with information fed back from a position sensor. However, it is difficult to accurately stop the screw at a specified position because of a time lag.
(2) It takes a certain amount of time to close a resin passage and, moreover, the amount of resin fed into a mold varies with the time necessary for closing the resin passage and any fluctuation of the screw position at which the resin passage begins to be closed, and therefore, it is difficult to maintain a stable weight of molded products.
An object of the present invention made in view of the above problem is to provide a device and a method of molding for an injection molding machine capable of reducing fluctuation in weight of resin molded products and of providing stable quality.
SUMMARY OF THE INVENTION
A molding device in accordance with the present invention for an injection molding machine, having a mold clamping unit which feeds molten resin into an opened mold and clamps the mold for compression molding, an injection unit which melts, kneads and injects molten resin into the opened mold using a screw, and a gate opening/closing mechanism which stops the injection of the molten resin, comprises a mold position detecting means for detecting a position of a specified mold when it is open, a stroke position detecting means for detecting the stroke position of the screw of the injection unit, a speed control means for controlling the advancing speed of the screw of the injection unit, a pressure control means for controlling an injection pressure, a gate opening/closing means for closing a gate after a specified amount of resin is fed through it into the mold, a gate opening detecting means for detecting the amount of gate opening, and a controller for generating commands to the speed control means, the gate opening/closing means, and the pressure control means.
The molding method of the present invention is adapted to: detect the position of the mold by a mold position detecting means when the movable mold has been lowered to a specified position, start the injection of molten resin by moving the screw forwardly in response to a signal from the mold position detecting means, detect by a stroke position detecting means when the screw has advanced to a specified position, decelerate the advancement of the screw to a specified speed in response to a signal from the stroke position detecting means, detect by the stroke position detecting means when the screw has advanced to a predetermined stop position, stop the advancement of the screw in response to a signal from the stroke position detecting means, reduce the injection rate of molten resin by gate opening/closi
REFERENCES:
patent: 4846651 (1989-07-01), Matsuda et al.
patent: 5035599 (1991-07-01), Harashima et al.
patent: 5057255 (1991-10-01), Sato et al.
patent: 5108672 (1992-04-01), Sasaki et al.
patent: 5196150 (1993-03-01), Mimura et al.
patent: 5221509 (1993-06-01), Fujimoto et al.
Fujimoto Satoshi
Nogawa Makoto
Heitbrink Jill L.
Kabushiki Kaisha Komatsu Seisakusho
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