JP2001252957A - Controller for injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller which can stabilize a mold inner pressure by an easy operation. SOLUTION: An mold inner pressure setting part 14 has a storage part for storing the detection pattern of a mold inner pressure sensor 11 as a mold inner pressure setting value in advance when a conforming article is obtained by conditioning by feeding back a detected value from a pressure sensor to an injection/dwelling pressure set value from an injection/-dwelling pressure setting part 13. In actual molding, by feeding back a detected value from the pressure sensor and adjusting the injection/dwelling pressure setting value from the injection/dwelling pressure set part by feeding the difference between the mold inner pressure setting value stored in the storage part and the detected value from the mold inner pressure sensor, mold inner pressure feedback is done with an injection/dwelling pressure feedback loop made as a minor loop to adjust the command value of injection/dwelling.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an injection molding machine, and more particularly to a control device for stabilizing an inner pressure of a mold in an injection / pressure keeping process.

[0002]

2. Description of the Related Art In injection molding, the internal pressure of a mold greatly affects the quality of a molded product. Therefore, control for stabilizing the in-mold pressure has been proposed. For example, there has been proposed a method in which the in-mold pressure control and the injection pressure control are connected in cascade, and the injection pressure is adjusted by changing the set value of the injection pressure based on the set value and the detected value of the in-mold pressure.

[0003]

In this method, the setting of the injection pressure and the setting of the in-mold pressure must be performed simultaneously when setting the conditions. However, the response of the injection pressure to the injection pressure feedback system has a very large time constant, so it is not easy to know how to change the injection pressure and how to set the injection pressure. is there.

In practice, the behavior of the mold inner pressure often becomes as shown in FIG. 2, and in order to obtain a non-defective product, it is necessary to set the wave shape as shown in FIG. Delivery is even more difficult.

An object of the present invention is to provide a control device capable of stabilizing the mold inner pressure by an easy operation.

[0006]

According to the present invention, there is provided an in-mold pressure sensor for detecting a resin pressure in a mold cavity or a flow path, a pressure sensor for detecting an injection / holding pressure, and Injection / holding pressure setting means, in an injection molding machine having a mold internal pressure setting means, the mold internal pressure setting means,
The detection pattern of the in-mold pressure sensor when a non-defective product is obtained by feeding back the detection value from the pressure sensor with respect to the injection / holding pressure set value from the injection / holding pressure setting means and performing condition determination. It has a storage unit that stores in advance as an in-mold pressure set value, and feeds back the detected value from the pressure sensor during actual molding, and sets the in-mold pressure set value and the in-mold pressure sensor stored in the storage unit. By adjusting the injection / holding pressure set value from the injection / holding pressure setting means by feeding back the difference from the detected value, the injection / holding pressure feedback loop is used as a minor loop to perform the mold pressure feedback to perform injection.・
There is provided a control device for an injection molding machine, wherein a command value for holding pressure can be adjusted.

In the present control device, a plurality of types of detection patterns may be stored in advance in the storage section of the in-mold pressure setting means for each type of molded article so that the patterns can be arbitrarily selected.

In the control device, a plurality of the detection patterns may be obtained for one molded product, and an average of the plurality of the detection patterns may be stored in the storage unit as a set value of the in-mold pressure.

In the control device, the sampling for obtaining the detection pattern may be performed in a predetermined time zone within one shot.

[0010] In the control device, further, the injection / holding pressure set value from the injection / holding pressure setting means may be set according to the following.
Feedback of the difference between the detection pattern stored in the storage unit and the detection value from the in-mold pressure sensor may be performed only in the predetermined time period within one shot.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a control device according to the present invention will be described with reference to FIG. This control device
Applied to the injection / holding process of injection molding, the control target is an injection motor in the case of an electric injection molding machine. In FIG. 1, the control device includes an in-mold pressure sensor 11 for detecting a resin pressure in a cavity or a flow path of a mold, and an injection / injection sensor.
It includes a pressure sensor 12 for detecting a holding pressure, an injection / holding pressure setting unit 13, and an in-mold pressure setting unit 14.

The injection / holding pressure set value from the injection / holding pressure setting unit 13 is calculated by a calculator 15 for giving a first-order lag.
The speed command value is given to the injection motor via an adder 16, a subtractor 17, and a calculator 18 functioning as a limiter.

A switch SW1 is connected between the mold pressure sensor 11 and the mold pressure setting section 14. As will be described later, the in-mold pressure setting section 14 has an arithmetic function and has a storage section (not shown) for storing the in-mold pressure set value. The in-mold pressure set value from this storage unit is
9, arithmetic unit 20 for giving a gain, switch SW2
To the adder 16 via Mold pressure sensor 11
Are also provided to a subtractor 19. As described later, the switch SW1
Is turned on in condition setting, and the switch SW2 is turned on in actual molding.

The detection value from the pressure sensor 12 is subtracted by a subtractor 17.
To form an injection / holding pressure feedback loop.

Next, the operation will be described. First, conditions are set. This condition setting is performed by the switches SW1 and SW
2 are both turned off. That is, the detection value from the pressure sensor 12 is fed back to the injection / holding pressure set value from the injection / holding pressure setting unit 13 to determine the condition. And when you can get good products,
When the switch SW1 is turned on, the detection pattern of one shot of the mold pressure sensor 11 when a good product is obtained is stored in the storage unit as the mold pressure setting value.

At the time of actual molding, the switch SW1 is turned off and the switch SW2 is turned on. In the actual molding, the detected value from the pressure sensor 12 is fed back to the subtractor 17, and the difference between the set value of the mold pressure stored in the storage unit and the detected value from the mold pressure sensor 11 is calculated by the subtractor 19. The calculated difference is given to the adder 16 via the computing unit 20 and the switch SW2. As a result, the injection / holding pressure set value from the injection / holding pressure setting unit 13 is adjusted by the above difference. This means that mold injection pressure feedback is performed using the injection / holding pressure feedback loop as a minor loop, which means that the command value to the injection motor is adjusted.

As described above, in actual molding, by turning off the switch SW1 and turning on the switch SW2,
By comparing and calculating the set value of the mold pressure stored in the storage unit and the detected value of the mold pressure from the mold pressure sensor 11 and performing mold pressure feedback using the injection / holding pressure feedback loop as a minor loop, the mold pressure at which a good product can be obtained. Can be stabilized with high accuracy. Therefore, it is possible to easily set the mold internal pressure which must be complicated, and to perform stable injection molding.

The present control device may be implemented as follows. In the first example, a plurality of types of detection patterns are stored in the storage unit of the in-mold pressure setting unit 14 for each type of molded article,
In other words, a plurality of different types of mold inner pressure set values are stored in advance depending on the type of the molded product. This is because the injection molding machine changes the molding conditions as needed to mold various molded products. Therefore, conditions are set in advance for each expected molded product, and the detection pattern from the in-mold pressure sensor 11 when a good product is obtained for each molded product is stored. When the type of the molded article is changed, a set value of the internal pressure corresponding to the change is selected from the storage unit, called up, and used as the set value of the internal pressure in the actual molding.

In the second example, a plurality of detection patterns when a good product is obtained for one molded product are obtained, and an average of the plurality of detection patterns is stored in the storage unit as a set value in the mold. . For this purpose, the in-mold pressure setting unit 14 has the calculation function described above. That is, the in-mold pressure setting unit 14 performs sampling for one detection pattern and stores the sampling value. By averaging a plurality of sampling values at the same sampling timing in a plurality of detection patterns, an average of the plurality of detection patterns can be obtained.

A third example is that sampling for obtaining a detection pattern is performed not in the entire time per shot but in a part of a predetermined time zone. this is,
For example, the in-mold pressure changes in a wave shape as shown in FIG. However, the time zone in which the molten resin has fluidity is shown in FIG.
Is not the whole area of the time zone T, but is particularly the area of the time zone T in the first half. This means, in other words, that the above-described control of the present invention effectively operates in the time zone T of FIG.
In consideration of this, the above-described sampling is performed only during the time period T in FIG. 2, and the detection pattern in the time period T is stored as the mold internal pressure set value.

In this case, the feedback of the difference between the detection pattern stored in the storage unit and the detection value from the in-mold pressure sensor 11 may be performed only during the predetermined time period T in one shot.

[0022]

As described above, according to the present invention, the injection / holding pressure feedback loop can be used as a minor loop to perform the mold internal pressure feedback, so that the mold internal pressure which can be obtained as a good product can be accurately and stably maintained. Can be done. Therefore, it is possible to easily set the mold internal pressure which must be complicated, and to perform stable injection molding.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a control device according to the present invention.

FIG. 2 is a diagram showing an example of a change in an in-mold pressure in one shot.

[Explanation of symbols]

 11 type internal pressure sensor 12 pressure sensor 13 injection / holding pressure setting unit 14 type internal pressure setting unit 15, 18, 20 arithmetic unit 16 adder 17, 19 subtractor

Claims (5)

[Claims] 1. An in-mold pressure sensor for detecting a resin pressure in a cavity or a flow path of a mold, a pressure sensor for detecting an injection / holding pressure, an injection / holding pressure setting means, and a mold. In the injection molding machine having an internal pressure setting means, the mold internal pressure setting means feeds back a detection value from the pressure sensor with respect to an injection / holding pressure set value from the injection / holding pressure setting means to determine a condition. Has a storage unit that stores in advance the detection pattern of the in-mold pressure sensor when a good product is obtained as an in-mold pressure set value.In actual molding, the detected value from the pressure sensor is fed back, and The difference between the mold internal pressure set value stored in the storage unit and the detection value from the mold internal pressure sensor is fed back to adjust the injection / holding pressure set value from the injection / holding pressure setting means. It allows the controller of the injection molding machine, characterized in that to be able to adjust the command value of the injection-holding pressure injection-holding pressure feedback loop performing mold internal pressure feedback as a minor loop. 2. The control device according to claim 1, wherein a plurality of types of detection patterns are stored in advance in the storage unit of the in-mold pressure setting means for each type of molded article, and can be arbitrarily selected. A control device for an injection molding machine. 3. The control device according to claim 1, wherein a plurality of the detection patterns are obtained for one molded product, and an average of the plurality of the detection patterns is stored in the storage unit as the in-mold pressure set value. A control device for an injection molding machine. 4. The control device for an injection molding machine according to claim 1, wherein sampling for obtaining the detection pattern is performed in a predetermined time zone within one shot. . 5. The control device according to claim 4, wherein the detection pattern stored in the storage unit and the detection pattern from the in-mold pressure sensor with respect to the injection / retention pressure setting value from the injection / retention pressure setting means. A control device for an injection molding machine, wherein feedback of a difference from a detected value is performed only in the predetermined time period within one shot.