JPH04308713A - Pressure control method and device for counter pressure method device - Google Patents

Abstract

PURPOSE:To control especially freely a foaming degree of a molded product irrespective of size of a thickness by controlling gas pressure within a cavity by corresponding to a position of a screw. CONSTITUTION:The title device is constituted so that gas pressure is controlled by controlling a solenoid proportional pressure valve 5A based on a screw position signal 10a of an injection molding machine, in a pressure control method and device of a counter pressure method device which is constituted so that molten resin is cast into a cavity 2 and the gas pressure is made to change under a state where the gas pressure is applied to the inside of the foregoing cavity 2 of a mold 1 connected with the foregoing injection molding machine 3a.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a pressure control method and device for a counterpressure method device, and particularly to a method and device for controlling the pressure in a cavity according to the screw position.
This invention relates to a novel improvement for freely controlling the degree of foaming of a molded product, regardless of its wall thickness.

0002

2. Description of the Related Art Generally, a method shown in FIG. 5 is adopted as a counterpressure method device connected to an injection molding machine and used to control the gas pressure inside a cavity. That is, what is indicated by the reference numeral 1 in FIG. 5 is a mold consisting of a pair of mold parts 1a and 1b, and a cavity 2 formed between each of the mold parts 1a and 1b is provided with an injection molding machine (not shown). The nozzle 3 is connected to the nozzle 3.

A conduit 6 is connected to the cavity 2, to which a pressure gauge 4, a solenoid valve 5a, valves 5b, 5c, and a pressure regulating valve 5d are connected, and a buffer tank 7 is connected to the conduit 6. A gas pressure generation source 8 consisting of a compressor is connected through it.

[0004] A case in which injection molding is actually performed using a counterpressure method apparatus in the above-mentioned configuration will be explained. As shown in FIG. 4, in the mold clamping process in state a, after the mold 1 is clamped and the nozzle 3 is connected to the mold 1, 15 ~
A gas pressure of 20 kg/cm2 is applied. Next, in the injection process in state b, injection starts and the molten resin enters the cavity 2.
As the cavity is filled, the space in the cavity decreases and the internal gas pressure increases. In order to maintain the initial pressure, the solenoid valve 5c is opened and the gas is released to the atmosphere via the pressure regulating valve 5d. The pressure adjustment at this time is constant and is performed by manual adjustment of the pressure regulating valve 5d. In addition, injection is continued while the pressure is removed through the electromagnetic valves 5b and 5c at the approximately 80% volume position of the injection process.

Next, in the foaming and cooling step in state c, the pressure is lowered by opening the solenoid valve 5b in order to reduce the pressure to atmospheric pressure. Next, in the mold opening and removal process in state d, each mold part 1a, 1b is opened, and the molded product 1
Extract 0.

[0006]

[Problems to be Solved by the Invention] Since the pressure control device of the conventional counterpressure method device was constructed as described above, the following problems existed. In other words, during the injection process, gas is released from the relief valve at a constant pressure to maintain pressure, but if the thickness of the molded product is uneven, a constant pressure will cause a difference in the degree of foaming inside the thick wall (core layer). It was supposed to happen. For example, thick-walled parts are easy to foam, while thin-walled parts are difficult to foam.In such cases, it may not be possible to obtain the necessary strength for products where the strength of the molded product is important. Inconveniences have arisen, and it has been impossible to control the degree of foaming well regardless of the wall thickness.

The present invention was made to solve the above-mentioned problems, and in particular controls the gas pressure inside the cavity according to the screw position, thereby controlling the degree of foaming of the molded product regardless of the wall thickness. An object of the present invention is to provide a pressure control method and device for a counterpressure method device that allows free control of pressure.

[0008]

[Means for Solving the Problems] A pressure control method for a counterpressure method device according to the present invention includes injecting molten resin into a cavity of a mold connected to an injection molding machine while applying gas pressure to the cavity. In the pressure control method for a counterpressure method device that changes the gas pressure, the gas pressure is controlled by controlling an electromagnetic proportional pressure valve based on a screw position signal of the injection molding machine.

The pressure control device of the counterpressure method device according to the present invention injects molten resin into the mold cavity while applying gas pressure into the cavity of the mold connected to an injection molding machine. In a pressure control device of a counter pressure method device that changes pressure, a screw position detector for detecting the position of the screw of the injection molding machine and a screw position signal from the screw position detector are input. The present invention is configured to include an electromagnetic proportional pressure valve for controlling the gas pressure, and a gas pressure generation source that generates the gas pressure and is connected to the electromagnetic proportional pressure valve, and controls the electromagnetic proportional pressure valve based on the screw position signal.

0010

[Operation] In the pressure control method and device for a counterpressure method device according to the present invention, as shown in FIGS. 2 and 3, the initial gas pressure (15 to 20 kg/cm ), the gas is released from the electromagnetic proportional pressure valve, and when the injection reaches the thin part B, the screw position is detected by the screw position detector set in advance, and the pressure is increased by the electromagnetic proportional pressure valve to, for example, 10 kg. /cm2. Therefore, the gas pressure is changed based on the screw position signal according to the wall thickness of the molded product (not limited to the two steps mentioned above, but three steps as necessary).
(sometimes in four stages), and the degree of foaming can be freely controlled.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the pressure control method and apparatus for a counterpressure method apparatus according to the present invention will be described in detail below with reference to the drawings. Note that the same or equivalent parts as in the conventional example will be described using the same reference numerals. 1 to 3 show a pressure control method and device for a counterpressure method device according to the present invention. FIG. 1 is a block diagram, FIG. 2 is a gas pressure characteristic diagram, and FIG. 3 is a configuration diagram showing a molding state. It is.

In FIG. 1, the reference numeral 1 indicates a mold consisting of a pair of mold parts 1a and 1b, and a cavity 2 formed between each mold part 1a and 1b has a screw 3a. It is configured to be connected to the nozzle 3 of the injection molding machine 3A.

A conduit 6 is connected to the cavity 2, to which a pressure gauge 4 and a plurality of electromagnetic valves 5a, 5b, 5c are connected. A gas pressure source 8 is connected.

An electromagnetic proportional pressure valve 5A is connected to the electromagnetic valve 5c, and a screw position signal 10a from a screw position detector 10 for detecting the screw position of the screw 3a is sent via a pressure setting device 11 to the electromagnetic proportional pressure valve 5A. Proportional pressure valve 5
It is input to A. Furthermore, a gas pressure generation source 8 is connected to the electromagnetic valve 5a via a buffer tank 7.

Next, a case will be described in which injection molding is carried out using the pressure control of the counterpressure method apparatus according to the present invention in the above-mentioned configuration. First, after the mold 1 is clamped and the nozzle 3 is connected to the mold 1, when the solenoid valve 5a is opened, gas pressure from the gas pressure generation source 8 is applied inside the cavity 2, and at this time Pressure is 15-20kg/c
It is m2.

Next, with the start of injection, as shown in FIGS. 2 and 3, the initial gas pressure (15~
20 kg/cm2), and when the injection reaches the thin part B, the screw position of the screw 3a is detected by the screw position detector 10. The electromagnetic proportional pressure valve 5A performs an on/off valve operation via the pressure setting device 11 in response to the screw position signal 10a from the screw position signal 10a, and changes the pressure to a preset value, for example, 10 kg/cm2.

Therefore, the gas pressure inside the cavity 2 is changed based on the screw position signal 10a according to the wall thickness of the molded product (not limited to the two steps described above, but may be three steps or four steps as necessary). The degree of foaming can be freely controlled.

[0018]

Effects of the Invention Since the pressure control method and device for a counterpressure method device according to the present invention are constructed as described above, the following effects can be obtained. In other words, since the gas pressure can be freely controlled according to changes in the wall thickness of the molded product, the degree of foaming during molding can be freely controlled, and foaming can be performed freely even in areas where strength is required. The degree of molding can be controlled and the quality of molded products can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a pressure control method and device for a counterpressure method device according to the present invention.

FIG. 2 is a characteristic diagram of gas pressure within the cavity.

FIG. 3 is a configuration diagram showing a molding state.

FIG. 4 is a process diagram showing a conventional molding process.

FIG. 5 is a block diagram showing a pressure control method and device for a conventional counterpressure method device.

FIG. 6 is a characteristic diagram of gas pressure within a conventional cavity.

[Explanation of symbols]

1 Mold 2 Cavity 3A Injection molding machine 3a Screw 5A Solenoid proportional pressure valve 10 Screw position detector 10a Screw position signal

Claims (2)

[Claims] Claim 1: While applying gas pressure to the cavity (2) of a mold (1) connected to an injection molding machine (3A), molten resin is injected into the cavity (2), and the gas is injected into the cavity (2). In a pressure control method for a counter pressure method device that changes pressure, an electromagnetic proportional pressure valve (5A) is opened and closed based on a screw position signal (10a) of the injection molding machine (3A) to control the gas pressure. A pressure control method for a counterpressure method device, characterized in that: 2. Inject the molten resin into the cavity (2) of a mold (1) connected to an injection molding machine (3A) while applying gas pressure, and reduce the gas pressure. In a pressure control device for a counter pressure method device that changes the injection molding machine (
a screw position detector (10) for detecting the position of the screw (3A);
10) for inputting the screw position signal (10a) from the electromagnetic proportional pressure valve (5A), and a gas pressure generation source that generates the gas pressure and is connected to the electromagnetic proportional pressure valve (5A), A pressure control device for a counter pressure method device, characterized in that the electromagnetic proportional pressure valve (5A) is controlled based on a screw position signal (10a).