JPH10100218A - Method and apparatus for heater temperature control of injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture stably a high quality molded product by a method wherein an operation amount corresponding to a heat quantity which is lacking due to continuous automatic molding is added to the operation amount simultaneously with start of the continuous automatic molding, and when start of a signal is detected in the continuous automatic molding, PID control is stopped for a set time which is set by a timer. SOLUTION: A detected temperature PV detected with a thermocouple 2 of an injection heating cylinder 1 is compared with a set temperature PV. Its deviation value (e) is respectively inputted to a proportional controller 4, an integral controller 5 and a differential controller 6 to carry out PID control. In this case, a switch SW2 which functions by setting a timer and turns on in continuous automatic molding id provided to an input side of the integral controller 5. Further, an FF set value of FF setting 7 is enabled to be added to an operation amount obtained by PID control operation via a switch SW1 which turns ON in continuos automatic molding. The obtained operation amount MV is outputted via a PWM(pulse width modulutor) 9 and a SSR(silicon rectifier) to control temperature of a heater of the injection heating cylinder 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for controlling a heater temperature of an injection molding machine, and more particularly to a method and an apparatus for controlling a heater temperature of a heating cylinder of an injection molding machine.

[0002]

2. Description of the Related Art Conventionally, general PID control as shown in FIG. 5 has been adopted for heater temperature control of an injection heating cylinder of an injection molding machine. Although FIG. 2 shows only one heater temperature control, the same applies to other heater zones.

In FIG. 1, a detected temperature PV detected by a thermocouple 2 of an injection heating cylinder 1 and amplified by an amplifier 3 is compared with a set temperature SV, and a deviation value e thereof is compared with a proportional controller 4 and an integral controller 5. Input to the differential controller 6 and PI
D control calculation is performed. Obtained manipulated variable (control output) M
V is input to a heater 11 via a PWM (pulse width modulator) 9 and an SSR (silicon rectifier) 10 to control the heater temperature of the injection heating cylinder 1.

FIG. 6 shows an example of a computer simulation result in the control configuration shown in FIG. The horizontal axis is time (se
c) The vertical axis is temperature (° C.).

As shown in FIG. 1, when the injection molding machine is started, the detected temperature PV is stabilized by temperature control by PID control. By the start of continuous automatic molding, plasticization and flow of the resin begin, and the amount of heat absorbed by the resin from the injection heating cylinder 1 increases. This corresponds to a decrease in the response gain of the controlled object. At this time, the detected temperature PV of the injection heating cylinder 1 becomes
Temporarily drops below the set temperature SV and returns to the set temperature SV again
, A so-called temperature undershoot phenomenon occurs. Further, even when continuous automatic molding is stopped, a temperature overshoot phenomenon occurs for the same reason.

[0006]

The conventional heater temperature control of the injection heating cylinder of the injection molding machine has the following problems because it is configured as described above.

That is, in the undershoot phenomenon described above, the time required for undershoot and return depends on the dead time and response time of the heater control system and the PID control constant. It takes about 100 seconds.

[0008] In particular, the undershoot of the temperature of the injection heating cylinder at the start of continuous automatic molding is a CD (compact disk).
In such precision molding, it may cause a defect of a molded product. In high-speed molding with a molding cycle of about several seconds, molding defects due to this undershoot become tens of sheets, resulting in a considerable number of defects.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and prevents undershoot of the temperature of the injection heating cylinder at the start of continuous automatic molding as much as possible, thereby achieving stable and high quality. An object of the present invention is to provide a method and a device for controlling a heater temperature of an injection molding machine capable of obtaining a molded product.

[0010]

The present invention has solved the above-mentioned problems as follows.

The amount of operation corresponding to the amount of heat insufficient due to continuous automatic molding of the injection molding machine is added to the amount of operation at the same time as the start of continuous automatic molding to improve the temperature undershoot. In this case, if the dead time of the heater control system is long, the integral control calculation during the undershoot causes an overshoot after the undershoot returns. Therefore, by stopping the control for a certain time, the overshoot is reduced. To prevent.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a method for controlling a heater temperature of an injection molding machine according to the present invention, an operation amount corresponding to a heat quantity deficient by continuous automatic molding is added to the operation amount simultaneously with the start of continuous automatic molding. When the rising of the signal is detected, the PID control is stopped only for the time set by the timer.

[0013] Further, when the falling of the continuous automatic molding in-process signal is detected, the PID control is stopped only for the time set by the timer. Further, it is characterized in that the integral control of the PID control is stopped only during the time set by the timer.

A heater temperature control device for an injection molding machine according to the present invention includes means for inputting a signal during continuous automatic molding, means for holding an FF set value to be added to an operation amount during continuous automatic molding, Means for holding a timer setting for the time during which the PID control is stopped, and means for stopping the PID control only for the time set for the timer when the rise and fall of the continuous automatic forming signal are detected. Features.

Further, it is characterized by having means for displaying an operation amount (control output) and means for adding the FF set value during continuous automatic molding.

[0016]

Embodiments of the present invention will be described with reference to the drawings. Parts that are the same as or equivalent to the conventional example will be described using the same reference numerals.

FIG. 1 is a block diagram showing a heater temperature control device of an injection molding machine according to one embodiment of the present invention. Although FIG. 2 shows only one heater temperature control, the same applies to other heater zones.

In FIG. 1, a detected temperature PV detected by a thermocouple 2 of an injection heating cylinder 1 and amplified by an amplifier 3 is compared with a set temperature SV, and a deviation value e thereof is compared with a proportional controller 4 and an integral controller 5. Input to the differential controller 6 and PI
D control is performed. In this embodiment, a switch SW2 which is operated by a timer setting 8 is provided on the input side of the integration controller 5. Also, the FF setting value of the FF setting 7 is added to the operation amount obtained by the PID control calculation by the operation (ON) of the switch SW1, and the obtained operation amount (control output) is obtained.
The MV is input to the heater 11 via the PWM (pulse width modulator) 9 and the SSR (silicon rectifier) 10 to control the heater temperature of the injection heating cylinder 1. The switch SW1 becomes 0N during continuous automatic molding, and the switch SW1 is turned on.
Numeral 2 is configured to be 0FF during the time of the timer setting 8 when continuous automatic molding starts and continuous automatic molding stops.

These temperature control processes are executed by a microprocessor in the heater temperature / temperature control device.

FIG. 2 shows a computer simulation result in the control configuration of FIG. The horizontal axis represents time (sec), and the vertical axis represents temperature (° C.).

In FIG. 1, a timer setting 8 is set to a value that is 1 to 2 times the control time constant time of the integration controller 5.

The value of the manipulated variable (control output) MV is always displayed on the screen of the controller. Due to the start of continuous automatic molding, the amount of heat absorbed by the resin increases, thus requiring a large amount of operation MV. Therefore, the difference between the operation amounts before the continuous automatic molding and when the operation is stabilized during the continuous automatic molding is previously checked from the screen display. In the FF setting 7, the difference between the manipulated variables before the continuous automatic molding and during the continuous molding is set.

When starting up the injection molding machine, the switch SW
The detection temperature PV is stabilized by temperature control by PID control with 1 set to 0FF and the switch SW2 set to 0N. Next, the molding is started by the start of the continuous automatic molding. At this time, the switch SW1 is set to 0N by the continuous automatic molding in progress signal, and the operation amount MV is increased by the FF set value. During the time of the timer setting 8, the switch SW2 is turned off and P
Only the integral control of the ID control is stopped. After the elapse of the timer set time, the switch SW2 is set to 0N and the PID control is started again.

As described above, by adding the operation amount corresponding to the amount of heat insufficient by continuous automatic molding to the operation amount at the same time as the start of continuous automatic molding, the temperature undershoot can be improved. In this case, if the dead time of the heater control system is long, the integral control calculation during the undershoot causes overshoot after the return of the undershoot. Can be prevented.

In the embodiment described above, as shown in FIG.
Although only the integral control was stopped during the time of the timer setting 8, as another embodiment, as shown in FIG.
6 is provided with a switch and SW2 on the input side.
W2 may be turned off to stop all PID control.

FIG. 4 shows a computer simulation result in the control configuration of FIG.

In the above-described embodiment, an example in which the FF setting is manually set has been described. However, a method of automatically calculating and setting the FF setting value is also conceivable. For example, the operation amount at the start of the continuous automatic molding is stored in the memory as the operation amount before the start of the continuous molding (A), and the difference in the operation amount at the time of the continuous automatic molding stop is stored in the memory as the stable operation amount during the automatic continuous molding (B). This can be easily realized by automatically setting the value of "BA" as a control condition for the next molding at the FF setting value when continuous automatic molding is stopped.

[0028]

According to the present invention, since the temperature undershoot at the start of continuous automatic molding can be reduced, the number of defective molded products occurring during the period can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a heater temperature control device of an injection molding machine according to one embodiment of the present invention.

FIG. 2 is a diagram illustrating a computer simulation result in the control configuration of FIG. 1;

FIG. 3 is a configuration diagram showing a heater temperature control device of an injection molding machine according to another embodiment of the present invention.

FIG. 4 is a diagram showing a computer simulation result in the control configuration of FIG. 3;

FIG. 5 is a configuration diagram showing a heater temperature control device of a conventional injection molding machine.

FIG. 6 is a diagram showing a computer simulation result in the control configuration of FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injection heating cylinder 2 Thermocouple 3 Amplifier 4 Proportional controller 5 Integral controller 6 Differential controller 7 FF setting 8 Timer setting 9 PWM (pulse width modulator) 10 SSR (Silicon rectifier) 11 Heater SW1, SW2 switch SV Set temperature PV detected temperature MV manipulated variable (control output) e Deviation value

Claims (5)

[Claims] In a method of controlling a heater temperature of an injection molding machine, an operation amount corresponding to a heat amount deficient by continuous automatic molding is added to the operation amount simultaneously with the start of continuous automatic molding, and a rise of a signal during continuous automatic molding is detected. A method of controlling a heater temperature of an injection molding machine, wherein the PID control is stopped only for a time set by a timer. 2. A method for controlling a heater temperature of an injection molding machine, wherein the PID control is stopped for a time set by a timer when a falling of a signal during continuous automatic molding is detected. 3. The integral control of the PID control is stopped only for a time set by a timer.
A method for controlling a temperature of a heater of an injection molding machine as described in the above. 4. A heater temperature control device for an injection molding machine, comprising: means for inputting a signal during continuous automatic molding; means for holding an FF set value to be added to an operation amount during continuous automatic molding;
Means for holding a timer setting for stopping PID control at the start of continuous automatic molding, and means for stopping PID control only for the time set by the timer when detecting the rise and fall of the continuous automatic forming signal. A heater temperature control device for an injection molding machine, comprising: 5. A means for displaying an operation amount (control output),
5. The heater temperature control device for an injection molding machine according to claim 4, further comprising means for adding the FF set value during continuous automatic molding.