JPH08318553A - Injection compression molding method - Google Patents

Abstract

PURPOSE: To eliminate the irregularity of the injection filling quantity in a mold cavity by allowing a resin to flow back toward an injection screw while applying mold clamping force thereto and closing a shut-off valve when a movable mold reaches a set position. CONSTITUTION: The front and rear positions of a screw 11 are detected by a screw position detection part 31 to prescribe injection filling quantity. After mold clamping rising pressure reaches a set value, an oil pressure control valve 16 is controlled through an injection control part 21 while an oil pressure value is detected by an injection pressure detection part 22 to drive a reversible motor 13 and the piston of an injection cylinder 12 to perform the injection filling into the cavity part 35 formed by a movable mold 2 and a fixed mold 3. The movable mold 2 is moved in the direction separated from the fixed mold 3 by the balance of the pressure of a resin and the mold clamping force applied by a mold clamping cylinder 6 accompanied by injection filling. Simultaneously with the completion of injection, dwelling force is applied to the resin charged in the cavity part 35 while the advance limit position of the screw 11 is held.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection compression molding method.

[0002]

2. Description of the Related Art Conventionally, in a high-pressure injection molding machine, as shown in FIG. 3, when an injection screw is moved forward and a resin stored in the front part of the screw head is injected and filled into a cavity,
The injection screw is completed slightly before the advance limit of the injection screw, and the resin injected and filled in the cavity shrinks as it cools and solidifies. The filling control was performed such that the shut-off valve was closed after the holding pressure was applied to the resin for a certain period of time by pressing against. In such a conventional high-pressure injection molding method, injection is generally performed in a state where the measured resin amount is larger than or equal to the filling amount.

Further, in the conventional low-pressure injection compression molding method, as shown in FIG. 4, the mold cavity is clamped by applying a mold clamping force to the movable mold and the fixed mold, and the mold cavity is closed. The molten resin was injected and filled in, the movable mold was retracted by the compression allowance, the holding pressure was applied at the forward limit of the injection screw, and the shutoff valve was immediately closed. . In such a conventional injection compression molding method, generally, the measured resin amount is almost equal to the filling amount, and the entire amount is injected and filled in the mold cavity.

[0004]

However, in the former high-pressure injection molding method, since the volume of the measured resin which is larger than the volume of the cavity formed between the clamped molds is injected and filled, both molds are injected. There was a problem that molding defects such as burrs and overpacks were likely to occur from the parting line.

However, in a molding method for molding a molded product having a generally thin product thickness by injection compression molding, a method similar to the above-described high-pressure injection molding method is used to insert the molding material into the mold cavity from the injection side. Since the holding pressure cannot be applied to the injection-filled resin, the total amount of resin measured equal to the filling amount is advanced to the limit of the injection screw, and the injection-filling amount of resin varies in order to injection-fill the cavity. However, there is a problem in that the dispersion of the resin at the time of measurement is directly reflected in the dispersion of the filling amount, resulting in the dispersion of the weight of the molded product, which lowers the yield of the molded product.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide an injection compression molding method which eliminates the variation in the injection filling amount in the mold cavity.

[0007]

In order to achieve the above object, according to the present invention, a molten resin is injected and filled in a state where the movable mold is in contact with a fixed mold so that the movable mold has a desired compression amount or more. When retracted, the amount of movement of the movable mold is detected by the position sensor, and the holding pressure applied to the resin by the forward movement of the injection screw is made smaller than the mold clamping force, and the resin is applied while applying the mold clamping force. The shutoff valve was closed when the movable mold was brought to the set position by backflowing to the injection screw side.

[0008]

The function of the movable mold moved by being pressed by the resin pressure and moved by injection-filling under the condition that the amount of the resin melted in the injection device is greater than or equal to the amount injected and filled in the mold cavity. By controlling the mold separation distance δn to be smaller than or equal to the initially set mold separation distance δ0 and closing the shut-off valve when δn ≦ δ0, the injection filling amount There is no variation.

[0009]

EXAMPLES Specific examples of the injection compression molding method according to the present invention will be described in detail below with reference to FIGS.

FIG. 1 is a conceptual diagram of control according to an embodiment of the present invention,
FIG. 2 shows a control flow chart at the time of injection molding according to the embodiment of the present invention.

The fixed mold 3 is attached to a fixed platen 5 fixed to one end of a machine base (not shown), while the movable mold 2 is provided at the other end of the machine base so as to face the fixed platen 5. It is attached to the movable platen 4.

A mold clamping cylinder 6 is provided on the rear surface of the movable platen 4.
The movable platen 4 is fixed to the piston 6a that moves back and forth inside and the tip of the piston rod 6b of this piston 6a, and the movable platen 4 is movable back and forth by introducing pressure oil before and after the piston 6a. There is. Reference numeral 35 indicates a cavity portion.

Reference numeral 10 denotes an injection device, which is composed of a screw 11, an injection cylinder 12, a forward / reverse rotation motor 13, a hopper 14a and a barrel 14.

A screw 11 is rotatably provided in a barrel 14, a resin raw material in a hopper 14a is heated and compressed in a supply zone and a compression zone, melt-measured in a measuring zone, and injected into a nozzle 15 through an injection zone. It is configured to be.

A heater for externally heating the resin raw material is provided on the outer peripheral surface of the barrel 14, and the resin raw material is sent forward by the rotation of the screw 11 while being melted. Reference numeral 11a indicates a screw head.

Reference numeral 12 is an injection cylinder, 12a is a piston, and 13 is a forward / reverse rotation motor, which is directly connected to the screw 11 and rotates the screw 11 forward and backward.

Reference numeral 17 denotes a control unit, which is a position sensor 7, a mold position detection unit 18, a reference point setting unit 19, a comparison control unit 20,
Injection control unit 21, injection pressure detection unit 22, mold clamping pressure control unit 23, mold clamping pressure detection unit 24, input / output interface 2
5, an arithmetic processing unit 26, a storage unit 27, an input keyboard 28, a display unit 29, and a shutoff valve control unit 30.

The position sensor 7 is connected to a mold position detector 18. A reference point setting unit 19 that sets the position of the movable mold 2 before injection filling as a reference point by the position sensor 7.
And the mold position detection unit 18 are connected, and the set value of the reference point setting unit 19 and the detection signal of the mold position detection unit 18 at the position of the movable mold 2 during the compression process are compared by the position sensor 7. Comparison control unit 2 for outputting a correction signal for the injection filling amount
0 is connected, and the comparison control unit 20 is connected to the input / output interface 25.

The injection control section 21 connected to the hydraulic control valve 16 for controlling the drive of the injection cylinder 12 and the forward / reverse rotation motor 13 and the injection pressure detection section 22 for detecting the oil pressure of the injection cylinder 12 are respectively provided. It is connected to the input / output interface 25.

The mold clamping pressure detector 24 is connected to a hydraulic control valve 8 for controlling the drive of the mold clamping cylinder 6, and the mold clamping pressure controller 23 is connected to an input / output interface 25.

The mold clamping pressure detector 24 for detecting the hydraulic pressure of the mold clamping cylinder 6 is connected to the input / output interface 25.

Reference numeral 31 is a screw position detection unit 31 provided for notifying the injection start position and the injection completion position, and this screw position detection unit 31 is connected to the input / output interface 25.

On the other hand, the mold clamping cylinder 6 and the injection cylinder 12
And an input / output interface 25 for inputting and outputting a control symbol to be output to each drive unit of the shutoff valve 32, a storage unit 27 for storing the setting condition, and a calculation for comparing the set value and the detection symbol and outputting a control signal. A processing device 26 is provided. Reference numeral 28 indicates an input keyboard, and 29 indicates a display unit.

The storage unit 27 has a mold compression force,
The holding pressure input value is stored as a set value.

A control method using the injection compression molding apparatus described above will be described.

In this embodiment, a low-pressure injection compression method will be described in which the molds 2 and 3 which have been closed in advance are filled with a molten resin, and then compression is performed on the mold clamping side.

First, in the first embodiment shown in FIGS. 1 and 2, pressure oil is introduced into the mold clamping cylinder 6 to move the movable mold 2 forward toward the fixed mold 3.

After the movable mold 2 and the fixed mold 3 are touched, the hydraulic pressure control valve 8 is controlled by the hydraulic pressure value detected by the mold clamping pressure detector 24 to send the pressure oil to the mold clamping cylinder 6, The movable mold 2 is fixed to the fixed mold 3 so that the mold clamping force set to the initial value is obtained.
Press to the side to increase the mold clamping pressure.

Here, the detection signal from the position sensor 7 is received by the mold position detection unit 18, and the reference point setting unit 1 is used as a reference point.
Set to 9. In this case, the reference point is set at a predetermined retracted position of the movable mold 2 after the mold clamping pressure is increased.

On the other hand, the injection filling amount is defined by detecting the forward / backward movement position of the screw 11 by the screw position detection unit 31. Then, after the mold clamping pressure increase reaches the set value, the injection control unit 2 detects the hydraulic pressure value with the injection pressure detection unit 22.
1, the hydraulic control valve 16 is controlled to drive the forward / reverse rotation motor 13 and the piston of the injection cylinder 12 to inject into the cavity portion 35 formed by the movable mold 2 and the fixed mold 3. Fill. Along with the injection filling, the movable mold 2 moves in a direction away from the fixed mold 3 due to the balance between the resin pressure injected and the mold clamping force applied by the mold clamping cylinder 6 (mold opening behavior). Then, at the same time as the injection is completed, the holding pressure is applied to the resin filled in the cavity 35 while keeping the forward limit position of the screw 11.

At this time, the holding pressure applied to the injection cylinder 12 is set according to the following equation with respect to the setting of the mold clamping force applied to the mold clamping cylinder 6.

[0032]

[Equation 1]

The position sensor 7 detects how much the movable mold 2 is separated from the fixed mold 3 by a position sensor 7, and the mold position detector 18 injects it into the cavity 35. In order to judge whether the filling amount was appropriate,
The comparison control unit 20 performs a comparison calculation with the mold separation distance setting value δ0 input to the reference point setting unit 19 in advance.

If the result of this comparison operation is δn> δ0,
The holding pressure to the injection cylinder 12 and the mold clamping force to the mold clamping cylinder 6 are continuously applied, the position of the movable mold 2 is detected by the position sensor 7, and the detection signal is received by the mold position detector 18 to set the reference point. Compared with the set value of the section 19, the comparison operation is repeated until δn ≦ δ0.

Since the molten resin injected and filled in the cavity 35 is set as shown by the above-mentioned formula, it is pushed back to the injection device 10 side through the nozzle 15.

If δn> δ0 as a result of this comparison calculation, the mold clamping pressure detection unit 24 detects the hydraulic pressure value so as to slightly increase the hydraulic pressure value on the mold clamping cylinder 6 side, and then the mold clamping pressure control unit 23 is detected. Issue a command.

The increase of the mold clamping force (mold clamping hydraulic pressure × projection area of the piston for the mold clamping cylinder) restricts the retreat limit of the movable mold 2. In this way, the position of the movable mold 2 in which the backward limit is restricted is detected again by the position sensor 7, and the detection signal is received by the mold position detecting unit 18, which is again compared with the set value of the reference point setting unit 19 to move the movable mold. The separation distance δn between 2 and the fixed mold 3 is δn ≦
It is repeatedly corrected until it reaches δ0.

Since the mold clamping force of the molten resin injected and filled in the cavity 35 is increased until the injection condition is satisfied so that δn <δ0, the cavity 35 is temporarily
The resin injected and filled into the injection device 1 through the nozzle 15
Pushed back to the 0 side.

In this way, when the mold separation distance of δn ≦ δ0 is satisfied and the molten resin in the cavity 35 becomes appropriate, a command from the input / output interface 25 is issued to the shutoff valve control unit 30 to shut off the shutoff valve. Three
2 is rotated by 90 degrees, and the cavity 35 and the resin on the injection device 10 side are shut off from each other.

Thereafter, on the injection device 10 side, when the forward / reverse rotation motor 13 is rotated while introducing pressure oil to the left side of the piston 12a in FIG. 1, the screw 11 is rotated and retracted, and the screw head 11a. The molten resin is stored in front of.

On the other hand, on the molds 2 and 3 side, the cavity 35 is formed.
For the resin injected and filled in, the movable mold 2 is pressed again toward the fixed mold 3 by the mold clamping pressure of the mold clamping cylinder 6, and the compression process is performed on the mold clamping side. In this case, the mold clamping force generated by the mold clamping cylinder 6 continues the mold clamping force set before injection filling.

After the completion of the compression process on the mold clamping side, the hydraulic control valve 8
Is controlled to remove the mold clamping pressure of the mold clamping cylinder 6 and take out the product, but the compression force from the mold clamping side is continued until the molten resin filled in the cavity 35 is cooled and solidified. There must be.

In the embodiment, the so-called low pressure injection compression molding in which the movable mold 2 is pressed and retracted by the pressure applied by the resin is described, but the movable mold 2 was retracted from the beginning by the compression margin of the resin. It is also possible to perform injection press molding in which resin is injection-filled in the state.

[0044]

As is apparent from the above description, in the present invention, molten resin is injected and filled in a state where the movable mold is in contact with the fixed mold and the movable mold is retracted more than a desired compression margin. At this time, the moving amount of the movable mold is detected by the position sensor, the holding pressure applied to the resin by the advance of the injection screw is made smaller than the mold clamping force, and the resin is injected while applying the mold clamping force. The amount of resin injected into the cavity can be controlled by backflowing to the screw side and closing the shutoff valve when the movable mold reaches the set position. It is possible to stably produce extremely high quality products. Further, by injecting a resin having a volume larger than the cavity volume during injection filling, the resin can be filled and adjusted in the die cavity with a lower mold clamping force, and a good product can be stably supplied.

[Brief description of drawings]

FIG. 1 is a control conceptual diagram according to an embodiment of the present invention.

FIG. 2 is a control flow chart at the time of injection compression molding according to the embodiment of the present invention.

FIG. 3 is a flow chart of a conventional normal injection molding method.

FIG. 4 is a flow chart of a conventional injection compression molding method.

[Explanation of symbols]

 2 movable mold 3 fixed mold 4 movable plate 5 fixed plate 6 mold clamping cylinder 6a piston 6b piston rod 7 position sensor 8 hydraulic control valve 10 injection device 11 screw 11a screw head 12 injection cylinder 13 forward / reverse rotation motor 14 barrel 14a hopper 15 nozzles 16 hydraulic control valve 17 control unit 18 mold position detection unit 19 reference point setting unit 20 comparison control unit 21 injection control unit 22 injection pressure detection unit 23 mold clamping pressure control unit 24 mold clamping pressure detection unit 25 input / output interface 26 Processing unit 27 Storage unit 28 Input keyboard 29 Display unit 30 Shut-off valve control unit 31 Screw position detection unit 32 Shut-off valve 35 Cavity unit

Claims (1)

[Claims] 1. A position sensor that measures the amount of movement of the movable mold when the movable mold is injected and filled with the movable mold in contact with the fixed mold and the movable mold is retracted beyond a desired compression margin. Detected by, the holding pressure applied to the resin due to the advance of the injection screw is made smaller than the mold clamping force, the resin is made to flow back to the injection screw side while applying the mold clamping force, and the movable mold is set at the set position. The injection compression molding method is characterized in that the shut-off valve is closed when the temperature becomes low.