JPH09277345A - Method for controlling combination type automatic flat die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a control method with a short control response time in the change of the lateral discharge distribution of a combination type automatic flat die by returning the adjustment target value of a lip clearance corresponding to the variation in discharge due to the temperature change of a die main body. SOLUTION: After the passage of time of about 5min (B point) from an adjustment starting point (A point), the discharge at a prescribed position approximately reaches a target adjustment amount by a lip part controller as shown by a solid line together with an adjustment amount given by a dotted line. With the lapse of time, a die temperature changes as the discharge indicates by a dashed line, and the adjustment target value of a lip clearance is returned gradually to an initial value so that aimed discharge distribution is being kept by adjusting both the change in die temperature and lip clearance (C point). Finally, when the temperature of a die main body reaches the adjustment target value of a set target adjustment amount, the lip clearance returns to an initial state, and the discharge is adjusted at a prescribed target value only by the change in the temperature of the die main body (D point).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a composite automatic flat die for controlling the thickness of plastic sheets or films or the profile of banks.

[0002]

2. Description of the Related Art Generally, in manufacturing a plastic sheet or film, a molten resin melt-kneaded in an extruder is molded into a sheet having a predetermined thickness by an automatic flat die and cooled and solidified by a casting roll. This automatic flat die is equipped with a device for adjusting the flow rate distribution of the molten resin flowing out from the lip. This flow rate distribution adjusting device is roughly classified into a lip gap adjusting type, a choke bar type and a resin temperature adjusting type. To be done.

The lip clearance adjusting method is a method of rotating the adjusting bolt by an electric motor or air pressure to adjust the lip clearance, or a method of thermally expanding the bolt with a heat bolt to adjust the lip clearance and controlling the outflow rate distribution. It has been known. The choke bar type is equipped with a choke bar that can change the flow passage area in the flow passage leading to the lip of the automatic flat die, and the choke bar is moved by an electric motor or air pressure to adjust the flow passage area. It is a method to control the flow rate distribution of molten resin,
In the resin temperature adjustment type, the resin temperature distribution is adjusted by the die body heater, or a dedicated lip heater is provided in addition to the die body heater to adjust the resin temperature distribution at the lip portion to control the outflow rate distribution. It has become. Further, there is also a composite type in which the lip gap adjusting type and the choke bar type are combined.

However, the lip gap adjustment type is effective for fine adjustment because the lip gap adjustment range is small, but a large profile error of a thick sheet cannot be corrected.
In the choke bar type, a flow stagnation part occurs because there is a step in the flow path, and the resin temperature adjustment type with the die body heater heats the die body and adjusts the temperature distribution in the lip width direction of the die body Since it is effective for rough adjustment, fine control of the flow rate distribution is difficult, and the one provided with a dedicated lip heater has the same drawbacks as the lip gap adjustment type.

Therefore, it has been proposed to control the long wavelength component of the sheet thickness or bank profile (hereinafter referred to as profile) by the die body temperature control device and the short wavelength component by the lip portion control device ( JP-A-6-71729).

FIG. 4 is a block diagram of a control system showing an embodiment of a sheet forming apparatus having both of the above-mentioned control devices, which is a composite automatic flat die (hereinafter referred to as a flat die).
1, a profile measurement control device 2, a die body temperature control device 3, and a lip portion control device 4. The flat die 1 is attached to the tip of the extruder 6 with the lip 5 facing downward. The flat die 1 sandwiches the resin flow path 5a reaching the lip 5 and forms a part of the die body temperature control device 3 on both sides.
The individual heaters 7 are provided in parallel with the width direction of the resin flow path 5a (direction perpendicular to the paper surface in FIG. 4) and at substantially equal intervals in the width direction of the flat die 1. The heater 7 also serves as a heat source for heating the main body of the flat die 1. The flat die 1 is designed to be cooled by a cooling device (not shown) forming a pair with the heater 7 and forming a part of the die body temperature control device 3, and between the resin flow path 5 a and the heater 7. Is a plurality of temperature sensors 8 along the width direction of the flat die 1.
Is provided. The heater 7 and the cooling device control the temperature distribution in the width direction of the flat die 1 to adjust the flow rate distribution of the molten resin flowing into the lip 5.

On one side of the lip 5, n thermoactuators 9 forming a part of the lip control device 4 are provided.
And a die bolt 10 are provided so as to be substantially orthogonal to the lip 5, and the thermoactuator 9 is provided with a temperature sensor 11 respectively. The thermoactuator 9 is cooled by a cooling device (not shown). The thermoactuator 9 and the cooling device adjust the gap of the lip 5 to adjust the outflow rate distribution of the molten resin in the lip 5.

The m heaters 7 of the die body temperature controller 3 and the n thermoactuators 9 of the lip controller 4 have a relationship of m <n. Further, the molding rolls 12, 13, 1 are provided below the flat die 1 in the discharge direction.
4 is provided, and the molten resin discharged from the lip 5 is cooled and molded to obtain the sheet 15.

As shown in FIG. 5, the profile measurement control device 2 includes a target profile setting unit 16, a comparator 17, a profile control unit 18, and a profile data processing unit 19.
And a bank sensor 20 and a thickness gauge 21.

The target profile setting section 16 measures the bank amount (the amount of molten resin accumulated in the upper portion between the molding rolls 12 and 13) from the temperature of the sheet 15 delivered from the molding rolls 12 and 13, or Thickness gauge 21
The target profile corresponding to the profile data of the bank amount or the thickness of the sheet 15 obtained from the output of is set. Then, the signal of this target profile is the comparator 17
Is input to

The profile data processing unit 19 uses the bank sensor 20 provided below the forming rolls 12, 13 or the output of a thickness gauge 21 provided on the downstream side of the forming rolls 12, 13, 14 to determine the bank amount or sheet. The signal of the thickness profile is obtained. Then, the signal of the target profile and the signal of the profile of the bank amount or the sheet thickness are compared by the comparator 17, and the profile deviation is calculated. Then, this profile deviation is input to the profile control unit 18.

The profile control unit 18 uses the input profile deviation as the long wavelength component (λl) and the short wavelength component (λ1).
s), and the new target temperatures corresponding to each are calculated and output to the temperature setting unit 22 of the die body temperature controller 3 and the temperature setting unit 23 of the lip controller 4.

The die body temperature control device 3 includes a temperature setting unit 22, a comparator 24, a temperature control unit 25, and m heaters 7.
It comprises a die body heating / cooling device 26 and a temperature sensor 8. The temperature setting unit 22 stores the set temperature pattern for each section in which the flat die 1 is sectioned in the width direction by the number m of heaters 7, and inputs it to the comparator 24. The temperature control unit 25 takes in the difference between the set temperature pattern stored in the temperature setting unit 22 and the output of the temperature sensor 8 to obtain the PID.
An operation amount for the die body heating / cooling device 26 is calculated by control or the like and is output to the die body heating / cooling device 26.

The die body heating / cooling device 26 controls the power supply to the m heaters 7 of the flat die 1 or the control of a cooling device (not shown) based on the output given from the temperature control unit 25, and the long wavelength component of the profile deviation. Adjustment corresponding to (λl) is performed. The temperature sensor 8 is provided for each section of the flat die 1, and detects the temperature of the flat die 1 and feeds back the detected outputs to the comparator 24.

The lip control device 4 includes the temperature setting unit 2
3, a comparator 28, a temperature control unit 29, a thermoactuator heating / cooling device 30 having n thermoactuators 9, and a temperature sensor 11.

The temperature setting unit 23 controls the thermoactuator 9 to cope with the short wavelength component (λs) of the profile deviation.
The set temperature pattern for each section divided by n is stored and input to the comparator 28. The temperature control unit 29 takes in the difference between the set temperature pattern stored in the temperature setting unit 23 and the output of the temperature sensor 11, calculates the operation amount for the thermo-actuator heating / cooling device 30 by PID control, etc. Actuator heating / cooling device 3
Output to 0. Thermo-actuator heating / cooling device 30
Controls the power supply to the n thermoactuators 9 or controls a cooling device (not shown) based on the output given from the temperature controller 29, and the lip 5 performs adjustment corresponding to the short wavelength component (λs) of the profile deviation. . The temperature sensor 11 is attached to each thermoactuator 9, and detects the temperature corresponding to the gap of the lip 5 and feeds it back to the comparator 28.

[0017]

However, the response time of the two control methods in the above-mentioned device is 3 to 10 minutes in the case of the lip control device, whereas it is 20 to 60 in the case of die body temperature control. Need minutes. Therefore, it takes a long time to correct the long wave component of the profile,
Problems such as sheet meandering and winding misalignment may occur before the deviation is corrected.

Since the response time of the thermo-actuator is about 3 to 10 minutes, it can be corrected only by the lip control device. There is an inconvenience such that the controllable range is exhausted and the profile cannot be corrected when the profile changes due to disturbance or the like.

In view of the above points, the present invention has an object to obtain a control method in which the control response time is short when the discharge amount distribution in the width direction of the composite type automatic flat die is changed.

[0020]

SUMMARY OF THE INVENTION The present invention provides a method for controlling a composite automatic flat die in which the discharge amount distribution in the width direction of the flat die is adjusted by adjusting the temperature of the flat die body and the lip gap. At the time of adjusting the discharge amount distribution, the target adjustment amount values of the die body temperature and the lip gap are set to values such that the predetermined discharge amount distribution can be obtained only by adjusting the die body temperature or the lip gap, respectively. After adjusting the temperature of the die body and the lip gap at the same time, and after the prescribed discharge amount distribution has been obtained, the lip amount is adjusted according to the change in the discharge amount due to the temperature change of the die body. The feature is that the target adjustment amount of the gap is returned to the initial state.

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the figure, the same parts as those in FIG. 4 are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is a diagram showing an example of a sheet thickness control system for carrying out the control method of the present invention, in which the molten resin discharged from the flat die is formed under the molding rolls 12, 13 ,. Sheet 1 cold-formed by 14
5 is obtained.

An infrared thickness gauge 21 including an infrared projector 21a and an infrared sensor 21b is provided in the middle of the moving path of the sheet 15, and the thickness signal of the sheet detected by the infrared sensor 21b is transmitted. It is input to the computer 40. On the other hand, the forming rolls 12, 13
A bank sensor 20 for measuring the bank amount is provided in the vicinity of, and a detection signal from the bank sensor 20 is also input to the computer 40. Then, according to the control signal from the computer 40, temperature control and lip gap control of the die body of the flat die 1 are performed. That is, the distribution of the ejection amount in the width direction from the die main body is adjusted by the measurement values of the thickness gauge 21 and the bank sensor 20 to adjust the thickness and the bank profile. The sheet thickness can be controlled to a predetermined value by controlling the discharge amount distribution only by the signal of the thickness gauge without the bank sensor.

Therefore, in order to adjust the sheet or film thickness and the bank profile, when changing the discharge amount distribution in the width direction from the flat die 1, the temperature of the die body and the gap between the lips in each section in the width direction are changed. And adjust at the same time.

That is, for example, the adjustment target values of the die body temperature control device and the lip portion control device for adjusting the discharge amount of the molten resin to a predetermined value at a certain point in the width direction are independent adjustments, respectively. Is set to such a value that a desired target value can be obtained.

Therefore, the adjustment of the lip gap and the die body temperature is started at the same time by changing the adjustment target value.

However, in reality, the adjustment of the lip gap can be completed in about 3 to 10 minutes by a thermoactuator or the like, whereas the temperature of the die body remains at the set temperature even if the set temperature changes. Until about 30-6
It takes 0 minutes.

Therefore, about 5 minutes after the control is started, the target discharge amount distribution can be obtained by the effect of adjusting the lip gap by the lip portion control device.

Therefore, when the desired discharge amount distribution is obtained as described above, the passage of time with the predetermined discharge amount distribution being maintained by both the lip gap adjustment and the die body temperature adjustment. Corresponding to the change in the discharge amount distribution due to the change in the temperature of the die main body, the adjustment target value of the lip gap is gradually returned to the initial state before the adjustment target value was given.

Therefore, when the lip gap is gradually returned to the initial state and the temperature of the die body reaches a predetermined target value, the predetermined discharge amount distribution can be obtained only by the temperature change of the die body.

FIG. 2 is a diagram showing changes in the thickness adjustment amount due to both controls at one point in the width direction of the sheet or the like, the solid line indicates the adjustment amount change by the lip control device, and the alternate long and short dash line indicates the die body temperature. The change in the adjustment amount by the control is shown, and the dotted line shows the change in the adjustment amount by the control of both.

That is, when about 5 minutes have passed from the start of adjustment (point A) (point B), the discharge amount at a predetermined position has almost reached the target adjustment amount as indicated by the solid line by the lip controller, and is indicated by the dotted line depending on the die temperature. The target adjustment amount is reached with the adjustment amount shown. However, with the passage of time, the die temperature changes as the discharge amount is shown by the constant chain line in FIG. 2, and accordingly, the lip gap adjustment target value gradually returns to the initial value, and the die temperature change and lip gap The target discharge amount distribution continues to be maintained by both adjustments (point C). Finally, when the temperature of the die body reaches an adjustment target value that is a set target adjustment amount, the lip gap returns to the initial state, and the discharge amount is adjusted to a predetermined target value only by changing the temperature of the die body. (Point D).

By adjusting in this way, the target adjustment amount can be obtained in about 5 minutes, and finally the adjustment amount of the lip control device returns to the almost initial state, so that the product is changed next. It can respond to time and disturbances.

By the way, the returning amount for returning the lip gap can be determined as follows. That is,
The temperature of the die body is measured by the temperature sensor 8, the change in the resin discharge amount distribution is calculated from the temperature change, and the lip gap is returned by an amount corresponding to the change. However, since the die temperature is actually measured without actually measuring the resin temperature, there is an error between the calculated value and the actual change amount. Therefore,
Further, it is preferable to correct the lip gap by the measurement value of the thickness gauge or the bank sensor.

FIG. 3 is a flow chart of a control method in which the lip gap is adjusted by adjusting the temperature of the thermoactuator. The target thickness profile of the sheet or the target bank amount profile is determined, and the die main body is determined. When the new target temperature of the die body and the new target temperature of the thermoactuator are set so that the target adjustment amount can be achieved independently by the temperature adjustment and the lip gap adjustment, The temperature control of the die body and the temperature control of the thermoactuator are simultaneously started.

Therefore, if the temperature change of the thermoactuator is detected in ST1 and the temperature change of the die body is detected in ST5, the temperature change of the die body is subtracted from the adjustment target value of the thermoactuator in ST2 (second (Points A to D in the figure). In ST3, the set temperature of the thermoactuator is changed based on the result. If there is no temperature change of the thermoactuator in ST2, the initial state is entered and normal profile control is continued (point D and after in FIG. 2). On the other hand, at the same time, the temperature change of the die body is detected in ST5, and if there is a temperature change, it is output to ST2,
In ST6, the temperature of the die body is further controlled.

In this way, when the target adjustment amount is achieved only by controlling the temperature of the die body, the temperature of the thermoactuator is returned to the initial value, and the temperature is maintained so as to be able to deal with disturbances after that, and the initial value is maintained. By using the temperature control of the thermo-actuator, it is possible to quickly reach the target adjustment amount.

[0038]

As described above, according to the present invention, until the actual thickness change of the sheet or the like due to the temperature control of the die body appears, the discharge amount distribution in the width direction is adjusted by the lip controller to adjust the die body temperature. When the change in the discharge amount distribution in the width direction due to the control appears, the adjustment by the lip control device is undone so that the discharge amount distribution in the width direction can be made uniform in about 3 to 10 minutes. And the control response time can be shortened. Moreover, since the adjustment amount by the lip control device gradually returns to the initial state, it is possible to sufficiently cope with the case where the ejection amount distribution in the width direction changes due to disturbance or the like.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a control system for implementing a control method of the present invention.

FIG. 2 is a diagram showing changes in die body temperature adjustment and lip gap adjustment amount.

FIG. 3 is a flowchart of a control method of the present invention.

FIG. 4 is a control system configuration diagram of a conventional sheet forming apparatus.

FIG. 5 is a control block diagram of FIG. 4;

[Explanation of symbols]

 1 Flat Die 7 Heater 8 Temperature Sensor 9 Thermo Actuator 11 Temperature Sensor 15 Sheet 20 Bank Sensor 21 Thickness Gauge

Claims (4)

[Claims] 1. A method of controlling a composite automatic flat die in which the discharge amount distribution in the width direction of the flat die is adjusted by adjusting the temperature of the flat die body and the lip gap, and at the time of adjusting the discharge amount distribution. , The temperature of the die body and the adjustment target value of the lip gap are set to values that can obtain the predetermined discharge amount distribution by adjusting only the temperature of the die body or the lip gap, respectively. After adjusting the lip gap at the same time, and after the predetermined discharge amount distribution is obtained, the adjustment target value of the lip gap is set to the initial state in response to the change in the discharge amount due to the temperature change of the die body. Characterized by having been put back,
Control method for compound automatic flat die. 2. The composite automatic flat according to claim 1, wherein the temperature change of the die body is measured, and the lip gap is returned to the initial state in response to the change of the discharge amount due to the temperature change. Die control method. 3. The composite automatic system according to claim 2, wherein the return amount of the lip gap is corrected by a thickness gauge for measuring the thickness of a sheet formed by a flat die or a measurement value of a bank sensor. Flat die control method. 4. The method for controlling a composite automatic flat die according to claim 1, wherein the measured values of the thickness gauge and the bank sensor are fed back when the lip gap is returned.