JPH06190888A - Method and machine for injection compression molding - Google Patents

Abstract

PURPOSE:To reduce the dispersion in resin amount and to control the dispersion in wall thickness and warpage of molded products by controlling the pressure difference between injection and mold fastening pressures. CONSTITUTION:The detection signals of an injection pressure sensor 13 and a mold-fastening pressure sensor 8 are input instantly to CPU 23, where the injection and mold fastening pressures are operated on the basis of the detected values. The CPU 23 obtains the pressure difference by subtracting the mold- fastening pressure determined from the injection pressure. Moreover, the CPU 23 compares the pressure difference with data on reference pressure differences stored in ROM 24 and outputs a control signal to a servo-relief valve driving circuit 27 as a corrective value to make the difference equal to the reference pressure difference. A servomotor changes the set-up pressure of the servo-relief valve installed in the hydraulic circuit of a mold fastening cylinder so that the hydraulic pressure, i.e., the mold fastening pressure, is changed by the difference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to injection compression molding in which a mold is opened according to a relationship between an injection pressure and a mold clamping pressure when a raw material resin is filled in a mold cavity, and then the resin in the mold is compressed. The present invention relates to a method and an injection compression molding machine.

[0002]

2. Description of the Related Art In injection compression molding, as shown in FIG. 5, a mold is first clamped at a low pressure, and then a heat-plasticized raw material resin is filled. Then, the mold is opened a little due to the relationship between the injection pressure and the mold clamping pressure at the time of filling, and after the mold cavity is gate-sealed, the mold clamping pressure is increased to close and compress the mold. Mold and cool the inside of the cavity. After that, the mold is opened and the molded product is taken out.

[0003]

However, conventionally, when the raw material resin is filled in the cavity of the mold, there are variations in the injection pressure and the clamping pressure. It changed every time I did it.
Therefore, the amount of resin entering the cavity of the mold varies, which causes a problem that the thickness of the molded product varies. Further, since the resin pressure when flowing into the molded product changes, distortion remains in the resin and warpage becomes large.

The object of the present invention is to eliminate the above-mentioned problems. By controlling the differential pressure between the injection pressure and the mold clamping pressure, the variation in the amount of resin is reduced and the thickness of the molded product is reduced. Another object of the present invention is to provide an injection compression molding machine and an injection compression molding method capable of suppressing variations in warpage.

[0005]

The method of the present invention uses an injection compression molding machine provided with a mold clamping cylinder for driving the mold to be clamped and an injection cylinder for injecting resin into a cavity in the mold. In the method of injecting and filling resin into the cavity in the mold, opening the mold after filling, and then closing the mold again to perform compression molding of the resin, start injection of resin in the mold To a reference pressure consisting of difference data between the mold clamping pressure and the injection pressure at the time of injection into the mold during the injection compression molding period from the closing of the mold to the compression molding of the resin. The gist of the invention is to control at least one of the mold clamping cylinder and the injection cylinder during injection compression molding based on the difference data to perform injection compression molding.

According to a second aspect of the present invention, there is provided an injection compression molding machine comprising a mold clamping cylinder for driving the mold to drive the mold, and an injection cylinder for injecting resin into a cavity in the mold. Mold clamping pressure detecting means for detecting the hydraulic pressure of the hydraulic circuit to be driven, injection pressure detecting means for detecting the hydraulic pressure of the hydraulic circuit to drive the injection cylinder, hydraulic circuit for driving the mold clamping cylinder and hydraulic circuit for driving the injection cylinder. A servo hydraulic pressure adjusting means provided on at least one of the above, and a mold clamping pressure of the mold during the injection compression molding period from the start of the injection of the resin in the mold to the compression molding of the resin by closing the mold. Storage means for storing reference pressure difference data consisting of difference data between the injection pressure at the time of injection into the mold and the value at that time, and the current detection result of the mold clamping pressure detection means and the injection pressure detection means. Based on the mold clamping pressure and the injection pressure, the differential pressure at that time is calculated, and compared with the reference pressure difference data stored in the storage means, and the servo hydraulic pressure adjusting means is controlled based on the comparison result. The gist is that it is provided with a control means.

[0007]

With the above construction, the invention of claim 1 injects and fills the resin into the cavity in the mold, opens the mold after filling, and then closes the mold again to compress the resin. During molding, the mold clamping pressure and the injection pressure during injection into the mold during the injection compression molding period from the start of resin injection in the mold to the compression of the resin by closing the mold. At the time of injection compression molding, at least one of the mold clamping cylinder and the injection cylinder is controlled to perform the injection compression molding based on the reference pressure difference data which is the difference data of the respective values.

According to the second aspect of the invention, the mold clamping pressure detecting means detects the hydraulic pressure of the hydraulic circuit for driving the mold clamping cylinder during the injection compression molding. Further, the injection pressure detecting means detects the hydraulic pressure of the hydraulic circuit that drives the injection cylinder. Then, the control means calculates the mold clamping pressure based on the current detection results of the mold clamping pressure detecting means and the injection pressure detecting means, and the differential pressure at that time based on the injection pressure, and further stores it in the storage means. The servo hydraulic pressure adjusting means is controlled based on the comparison result compared with the reference pressure difference data.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 2, the injection compression molding machine 1 is composed of a mold clamping device 2, an injection device 3, and a control device 4 (see FIG. 4).

The mold clamping device 2 includes a mold clamping cylinder 7 that drives the movable mold 6 to open and close relative to the fixed mold 5. Further, the mold clamping cylinder 7 is provided with a mold clamping pressure sensor 8 for detecting the hydraulic pressure in the mold clamping cylinder 7.

As shown in FIG. 2, the injection device 3 is provided with a raw material measuring device 9, a raw material heating plasticizing device 10, and an injection drive mechanism 11. The raw material metering device 9 measures the raw material and supplies the raw material to the raw material heating and plasticizing device 10.
The raw material heating and plasticizing device 10 heats and plasticizes the raw material sent from the raw material measuring device 9. Injection drive mechanism 11
Has an injection cylinder 12. Then, the injection cylinder 12 drives a ram (not shown) so that the raw material plasticized in the raw material heating and plasticizing device 10 is inside the cavities (not shown) of the molds 5 and 6 provided in the mold clamping device 2. It is designed to shoot at. Injection cylinder 1
An injection pressure sensor 13 that detects the hydraulic pressure in the injection cylinder 12 is provided at 2.

The hydraulic circuit of the injection compression molding machine 1 will be described with reference to FIG. The mold clamping cylinder 7 of the mold clamping device 2 is a double-acting cylinder, and for the hydraulic pump 14, a servo relief valve 15 and a solenoid switching valve 16 as servo hydraulic pressure adjusting means.
Connected through. The hydraulic pump 14 is driven by an electric motor 17 to generate hydraulic pressure. The servo pressure of the servo relief valve 15 can be analog-adjusted by a servo motor 18. The solenoid switching valve 16 has 4 ports 2
This is a position switching valve, and the circuit is switched and controlled based on a control signal output from the control device 4 so that the mold clamping cylinder 7 can reciprocate.

The injection cylinder 12 of the injection drive mechanism 11 is a double-acting cylinder and is connected to a hydraulic pump 19 via an electromagnetic relief valve 20 and an electromagnetic switching valve 21. The hydraulic pump 19 is driven by an electric motor 22 to generate hydraulic pressure. The electromagnetic relief valve 20 controls the hydraulic pressure by exciting the solenoid.
The electromagnetic switching valve 21 is a 4-port, 3-position switching valve, and controls the circuit switching based on a control signal output from the control device 4 so that the injection cylinder 12 can reciprocate.

Next, the electrical construction of the control device 4 in the injection compression molding machine 1 will be described. A central processing unit (hereinafter referred to as CPU) 23 is connected to the mold clamping pressure sensor 8 as shown in FIG. 1, and inputs a hydraulic pressure detection signal from the mold clamping pressure sensor 8. The injection pressure sensor 13 is connected to the CPU 23, and the hydraulic pressure detection signal from the injection pressure sensor 13 is input. CPU
23 is a read-only memory (hereinafter, R
24 readable and writable memory (hereinafter referred to as R)
AM) 25 is connected. The ROM 24 stores various control programs and various setting data for controlling the injection compression molding machine 1. Further, the reference pressure difference data δ is stored in the ROM 24. The reference pressure difference data δ is data of the difference between the injection pressure and the mold clamping pressure at the time when the most suitable molded product is obtained in the injection pressure molding process period (see C in FIG. 4). It consists of a series of data from the "filling" stage of the injection compression molding process, that is, from the injection start time t in FIG. 4 to the "mold opening" stage in FIG.

Further, the RAM 25 has a storage area serving as a working memory for performing various calculations, a storage area for storing the data set by the setter 26, and the like. CPU2
A servo relief valve drive circuit 27 for driving the servo relief valve 15 is connected to 3 and drives and controls the servo motor of the servo relief valve 15 based on a control signal output from the CPU 23. Although not shown, the CPU 23 is connected to a drive circuit of a controlled device such as the raw material metering device 9 that constitutes the injection device 3 and a drive circuit of the electromagnetic switching valves 16 and 21 in addition to the drive circuit 27. ing.

Now, the operation of the injection compression molding machine 1 configured as described above will be described. CPU 2 of control device 4
Reference numeral 3 controls the mold clamping device 2 and the injection device 4 based on the injection compression molding control program stored in the ROM 24. That is, when low pressure mold clamping is performed in the injection compression process shown in FIG.
Outputs a control signal to the servo relief valve drive circuit 27,
The servomotor 18 is driven to reduce the hydraulic pressure in the hydraulic circuit. As a result, the servo relief valve 15 is driven,
The hydraulic pressure is maintained on the low pressure side. Next, the CPU 23 switches the electromagnetic switching valve 16 from the normal position in FIG. 3 to the offset position in order to drive the ram of the mold clamping cylinder 7 of the mold clamping device 2 in the mold clamping direction. As a result, the ram of the mold clamping cylinder 7 is driven in the mold clamping direction, and the mold clamping is performed.

Next, after the mold clamping is completed, the CPU 23 drives and controls the injection device 3. That is, in order to drive the injection cylinder 12, the electromagnetic switching valve 21 is switched from the neutral position to the right offset position shown in FIG. As a result, the injection cylinder 1
Since the ram No. 2 is driven in the injection direction, the raw material resin plasticized by the raw material heating plasticizing device 10 is filled in the cavities in the molds 5, 6.

From this injection start time (t shown in FIG. 4), the CPU 23 inputs the detection signals of the injection pressure sensor 13 and the mold clamping pressure sensor 8 from time to time, and the injection pressure A ( (See FIG. 4) and the mold clamping pressure K are calculated. Then, the CPU 23 subtracts the mold clamping pressure K from the obtained injection pressure A to obtain the pressure difference D. Furthermore, CPU2
Reference numeral 3 compares the reference pressure difference data δ stored in advance in the ROM 24 with the pressure difference D, and the difference (δ-D) is used as a correction value in the servo relief valve drive circuit so as to be equal to the reference pressure difference δ. Output a control signal. Therefore, since the servo motor 18 changes the pressure setting of the servo relief valve 15, the hydraulic pressure, that is, the mold clamping pressure is changed by the difference (δ−D). The CPU 23 controls the hydraulic pressure setting of the hydraulic circuit of the mold clamping cylinder 8 from the "filling" stage to the "mold opening" stage in FIG.

As a result, the actual mold clamping pressure B is controlled based on the reference pressure difference data δ as shown in FIG.
The mold clamping pressure is as shown in B of FIG. Therefore, in this embodiment, by controlling the setting of the hydraulic pressure of the hydraulic circuit of the mold clamping cylinder 7, the waveform of the difference between the injection pressure and the mold clamping pressure is always constant, so that the inside of the cavities of the molds 5 and 6 are kept. The pressure applied to the resin is the same for each shot.

The present invention is not limited to the above embodiment, but may be as follows. (1) Although the reference pressure difference data δ used a suitable actual value in the above-mentioned embodiment, it may be an experimental value or a theoretical value. (2) A servo solenoid valve may be provided in the hydraulic circuit of the injection cylinder 12 to control the hydraulic pressure by the CPU 23, or the hydraulic pressures of the hydraulic circuits of both the mold clamping cylinder 7 and the injection cylinder 12 may be controlled.

[0021]

As described above in detail, according to the present invention, since the waveform of the difference between the injection pressure and the mold clamping pressure is always the same, the pressure applied to the resin in the cavity can always be the same for each shot. . Therefore, by controlling the differential pressure between the injection pressure and the mold clamping pressure, it is possible to reduce variations in the amount of resin, and it is possible to suppress variations in wall thickness and warpage of molded products.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of an injection compression molding machine according to an embodiment of the present invention.

FIG. 2 is a front view of the injection compression molding machine.

FIG. 3 is a hydraulic circuit diagram of the injection compression molding machine.

FIG. 4 is a characteristic diagram showing injection pressure and mold clamping pressure.

FIG. 5 is a flowchart showing the steps of injection compression molding.

[Explanation of symbols]

1 ... Injection compression molding machine, 2 ... Mold clamping device, 3 ... Injection device, 4
... Control device, 5 ... Fixed mold, 6 ... Movable mold, 7 ... Mold clamping cylinder, 8 ... Mold clamping pressure sensor as means for detecting mold clamping pressure, 11 ... Injection drive mechanism, 12 ... Injection cylinder, 13 ...
Injection pressure sensor as injection pressure detecting means, 14 ... Hydraulic pump, 15 ... Servo relief valve as servo hydraulic pressure adjusting means, 16 ... Electromagnetic switching valve, 17 ... Electric motor, 18 ...
Servo motor, 19 ... Hydraulic pump, 20 ... Electromagnetic relief valve, 23 ... Central processing controller (CP) as control means
U), 24 ... ROM as storage means, 25 ... RAM,
27 ... Servo relief valve drive circuit.

Claims (2)

[Claims] 1. An injection compression molding machine comprising a mold clamping cylinder for driving a mold to drive a mold and an injection cylinder for injecting resin into a cavity in the mold, wherein the cavity in the mold is used. A method of injecting and filling a resin, opening the mold after filling, and then closing the mold again to perform compression molding of the resin, in which the mold is closed and the resin is compressed after the injection of the resin in the mold is started. Based on the reference pressure difference data consisting of the difference data between the mold clamping pressure during the injection compression molding period until molding and the injection pressure at the time of injection into the mold,
An injection compression molding method characterized by controlling at least one of a mold clamping cylinder and an injection cylinder during injection compression molding to perform injection compression molding. 2. An injection compression molding machine comprising a mold clamping cylinder for driving a mold to drive the mold, and an injection cylinder for injecting resin into a cavity in the mold, wherein the hydraulic pressure of a hydraulic circuit for driving the mold clamping cylinder is controlled. At least one of the mold clamping pressure detecting means for detecting, the injection pressure detecting means for detecting the hydraulic pressure of the hydraulic circuit for driving the injection cylinder, and the hydraulic circuit for driving the mold clamping cylinder and the hydraulic circuit for driving the injection cylinder. Servo oil pressure adjusting means provided and the mold clamping pressure and injection into the mold during the injection compression molding period from the injection start of the resin in the mold to the compression molding of the mold by closing the mold. Storage means for storing reference pressure difference data consisting of difference data between the injection pressure and the current value of the mold, and the mold clamping pressure based on the current detection results of the mold pressure detecting means and the injection pressure detecting means. And a control means for calculating a pressure difference at any given time based on the injection pressure, comparing it with the reference pressure difference data stored in the storage means, and controlling the servo oil pressure adjusting means based on the comparison result. Injection compression molding machine.