JPH1086217A - Film thickness control device in inflation molding process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control a thickness of a film by automatically adjusting the number of revolutions of a screw of an extruder or a take-off speed of a take-off equipment. SOLUTION: A reduction quantity and a moving average per unit time of a raw material housed in a raw material housing section are obtained. Further, a reduction quantity per unit time during a fixed time is added up. From its result, an actual extruder output is obtained. Based on the actual extruder output, the necessary number of revolutions of a screw of an extruder or a take-off speed of a film is calculated. By the calculated numerical value, the number of revolutions of screw or the take-off speed are automatically controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film thickness control apparatus for controlling a film thickness while ensuring a predetermined production amount by automatically adjusting a screw rotation speed of an extruder or a take-up speed of a take-off machine in blown molding.

[0002]

2. Description of the Related Art Conventionally, in inflation molding of a film, a resin heated and melted by a screw of an extruder is extruded from a mold and taken up by a take-up machine. In this case, in order to stably form a film having a predetermined thickness, clogging of the screen during continuous operation of the extruder and variation in the amount of raw material supplied to the extruder per unit time occur. During the production, the thickness of the film is measured directly using a micro gauge or the like, and based on the result, the take-up speed is changed, or the rotation speed of the screw is changed to adjust the film thickness to keep it constant. Has been done.

[0003] The above adjustment work has recently been described in
An automatic adjusting device described in JP-A-13190 is proposed.

[0004]

However, in the conventional method of directly measuring the thickness of a film using a micro gauge or the like, the thickness measurement requires man-hours of a field worker, and in practice, it is required to continuously extrude the film. It is difficult to measure the thickness of a film formed and wound up by a winder during molding, and it can be measured only after the product is wound up, and cannot be adjusted in an actual extruded state.

[0005] The method of the above automatic adjusting device is a method of calculating the extruded amount from the consumption time of a certain amount of raw material from the upper limit to the lower limit in the raw material measuring section. For example, 1 kg is set as a fixed amount of raw material. Sometimes, for the first time after 1 kg of raw material is consumed, the extruded amount at the time of consumption is calculated, so that the real-time extruded amount during operation cannot be grasped.

Further, it is difficult to adjust the take-off speed with respect to the fluctuation of the consumption of the raw material less than the set constant amount, and the fluctuation of the extruding amount which occurs in a short cycle while the constant amount of the raw material is consumed. The thickness cannot be detected, and fine thickness control cannot be performed.

In the above-mentioned method of adjusting the take-off speed, although the thickness can be controlled to some extent, when the extruding amount is reduced due to clogging of the foreign matter removing screen due to long-term operation of the extruder,
There is a possibility that the production amount per hour decreases and the predetermined production amount cannot be secured.

The present invention has been made in view of such conventional problems, and an object of the present invention is to solve the above-mentioned problems and to secure a predetermined production amount while maintaining the film thickness. An object of the present invention is to provide a film thickness control device in an inflation molding process capable of performing fine control and improving the thickness accuracy of a product.

[0009]

According to a first aspect of the present invention, there is provided a film thickness control apparatus for an inflation molding step (hereinafter, the first aspect of the present invention is referred to as a first aspect of the present invention). In the inflation molding step, the molten resin heated and kneaded by the extruder is extruded from a die at the tip of the extruder, and a cylindrical film obtained by the extruder is pulled by a take-up machine. The weight of the stored raw material resin is measured at an arbitrary unit time T1, and the measured value is taken as an arbitrary continuous number to calculate an average weight value. This is repeated for each unit time to obtain a moving average value. Calculating means, and calculating the unit time weight loss amount by subtracting the moving average value calculated this time from the moving average value calculated last time to calculate and storing the weight loss amount within the unit time T1. The weights per unit time are calculated by adding the values of the weight loss amounts per unit time obtained by the above steps and the unit time, and calculating the weight loss per unit time. Means for calculating the extrusion amount of the extruder per unit, means for detecting the take-up speed of the take-off machine, means for detecting the width of the cylindrical film being formed, the detected take-up speed, the width, and Means for calculating and storing a standard extrusion rate per unit time for the thickness to match the standard value from the set standard value (thickness, density of raw resin used, etc.) of the cylindrical film; There is provided a means for outputting a speed adjustment signal to the motor of the extruder so as to make the amount coincide with the reference extrusion amount, and adjusting the screw rotation speed of the extruder.

A film thickness control device in the blown film forming step according to claim 2 (hereinafter, the invention according to claim 2 is referred to as invention 2) supplies the raw material resin stored in the raw material storage section to an extruder, The molten resin heated and kneaded by the extruder is extruded from a die at the tip of the extruder, and a cylindrical film obtained is taken out by a take-off machine. Means for measuring a weight at each arbitrary unit time T1, calculating an average weight value by taking an arbitrary continuous number of the measured values, and repeating this for each unit time to calculate a moving average value; A unit time weight loss amount calculating means for calculating and storing the weight loss amount within the unit time T1 by subtracting the moving average value calculated this time from the calculated moving average value; The weight loss per unit time is calculated by adding a plurality of sequentially obtained weight loss values per unit time during an arbitrary integration time T2, and the extruder is extruded per unit time. Means for calculating the amount, means for detecting the take-off speed of the take-off machine, means for detecting the width of the cylindrical film being formed, the detected take-off speed, width, and a preset cylindrical film. Means for calculating and storing a standard extrusion rate per unit time for the thickness to match the standard value from the standard value (thickness, density of the raw material resin to be used, etc.); Means for setting and storing the upper limit value and the lower limit value, and comparing the calculated extrusion amount and the reference extrusion amount, means for determining whether the difference is within the lower limit value,
If it is within the upper and lower limits, a means for outputting a speed adjustment signal to the motor of the take-off machine to adjust the take-up speed, and if it is out of the upper and lower limits, the calculated extrusion amount and the reference extrusion amount match. Output a speed adjustment signal to the motor of the extruder so that
It is characterized by having means for adjusting the screw rotation speed of the extruder.

[0011]

In the control device according to the first aspect of the present invention, the following operation is performed. First, the weight of the raw material resin stored in the raw material storage section of the extruder is measured for an arbitrary unit time T1 (for example, 1).
Every second), and take an arbitrary continuous number (for example, 5) of the measured values to calculate an average weight value.

Next, the old measured values are sequentially deleted every T1 hours, the new measured values are added to calculate the average value, and this is repeated every unit time to calculate the moving average value.

Every time the moving average value is obtained, the weight loss amount within the unit time T1 is calculated by subtracting the moving average value calculated this time from the moving average value calculated last time, and the weight loss amount per unit time is calculated as: Store in the device.

The number of stored values corresponding to the number (60 if T1 = 1 second) corresponding to an arbitrary integration time T2 (for example, one minute) is added to calculate a weight reduction amount per integration time. T
Calculate the exact amount of raw material reduction (consumption) per 2 hours.
The calculated value is calculated, for example, per hour (for example, T2 =
If it is one minute, multiply by 60) and convert it to the actual amount of extrusion (Q).

At the same time, the take-off speed and width during production are detected,
Based on the standard value (thickness, density of raw material resin used, etc.) of the cylindrical film to be produced, the standard extrusion amount per unit time required to form a film having the standard value thickness is calculated.

The calculation of the reference extrusion amount (QST) performed in the apparatus of the present invention 1 uses the detected take-off speed (L), the detected film width (W), and the standard value (D) of the thickness. Using the numerical value of the density (ρ) of the raw material resin, the following formula (1) is used. QST = L × W × D × ρ × K (1) where K is a proportional constant

Then, the QST is compared with the calculated extrusion amount (Q), and a speed adjustment signal is output to the motor of the extruder to change the screw rotation speed so that the two coincide with each other.
The thickness of the film is controlled while maintaining a predetermined production amount.

The operation performed by the control device of the present invention 2 is the same as that of the present invention 1 up to the calculation of the reference extrusion amount (QST). , An upper limit and a lower limit are set and stored. The upper and lower limits can be set arbitrarily depending on the tolerance of the target production amount. For example, the upper limit is + 5% of the reference extrusion amount,
The lower limit may be set to -10% of the reference extrusion amount.

Next, the calculated extrusion amount is compared with the reference extrusion amount, and it is determined whether or not the difference is within the upper and lower limits.

If the value is within the upper and lower limits, the standard value (thickness, density of raw resin used, etc.) of the cylindrical film being produced.
, A take-off speed for operating at the calculated extrusion rate is calculated. Then, a speed adjustment signal is output to the motor of the take-off machine so as to adjust the speed so that the take-up speed currently being produced matches the calculated take-up speed.

The difference between the above calculated amount of extrusion and the reference amount of extrusion is
If it is out of the lower limit, a speed adjustment signal is output to the motor of the extruder to adjust the screw rotation speed so that the reference extrusion amount and the calculated extrusion amount match as in the first embodiment.

In the film thickness control apparatus of the present invention, the unit time T1 for measuring the weight loss of the raw material, the number for obtaining the moving average value, and the integration time T2 can be arbitrarily set, and the extruder output and operating time can be set. The optimal value can be set flexibly according to the situation and the characteristics of the product to be produced, so that the variation of the electric signal conversion of the weight detection sensor, the weight detection noise due to the vibration of the sensor generated during the operation of the device, and the weight due to the screw rotation of the extruder It is possible to remove the influence of the pulsating component of the detected value. In addition, control can be finely automated compared to the prior art, and as a result, the thickness accuracy of a product to be produced is greatly improved.

Further, even when the extruded amount is reduced due to clogging of the foreign matter removing screen due to the long-term operation of the extruder, a comparison with a standard extruded amount is periodically performed, and the screw rotation speed is automatically adjusted. A predetermined production amount can be ensured without a reduction in the production amount per hit.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 and 2 of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration of an inflation molding process provided with the film thickness control devices of the present inventions 1 and 2. In FIG. 1, this molding step comprises a raw material tank 1 for storing raw resin, a hopper 2 for supplying raw resin, an extruder 3 for heating and kneading the raw resin to produce a molten resin, and a cylindrical shape. It comprises a take-up machine 4 for taking out an extruded film, a take-up machine 5 for taking up the film, and a controller 6 for controlling the operation of these.

A valve 12 is provided between the raw material tank 1 and the hopper 2, and when the raw material resin in the hopper 2 reaches a certain amount or less, the valve 12 opens to supply the raw material resin from the raw material tank 1 to the hopper 2. Is done. When the raw material resin in the hopper 2 reaches a certain amount or more, the valve 12 is closed and the supply is stopped.

The hopper 2 is provided with a weight detection sensor 7, which sends signals for starting and stopping the supply of the raw material resin, and detects the weight of the resin accompanying the operation of the extruder.

The hopper 2 is installed at the rear of the extruder 3, and a die 1 is provided in front of the extrusion direction A 1 of the extruder 3.
3 are connected. A cylindrical film 14 is extruded upward from the mold 13. The extruder 3 has a screw 15 that is driven to rotate by a motor 17 and extrudes resin. An air pump 9 is provided in the vicinity of the extruder 3, and air supplied from the pump passes through the mold 13 and is blown up to the upper direction A2 in the extrusion direction.

A cooling device 16 for blowing cooling air for cooling the extruded cylindrical film 14 is arranged above the mold 13 so as to surround the cylindrical film 14. Guide plates 18A and 18B for guiding the cylindrical film 14 are provided above the cooling device 16, and the films passing through the guide plates are composed of rollers 4A and 4B which are driven to rotate by a motor (not shown). It is taken up by the take-up machine 4 and taken up by the take-up machine 5 via the width sensor 8.

The controller 6 includes a raw material weight signal in the hopper 2 from the weight detection sensor 7, a width detection signal from the width sensor 8, a rotation speed signal from the motor of the extruder 3, and a signal from the motor of the take-off machine 4. A rotation speed signal or the like is input.

Next, the control operation of the thickness control device according to the first and second embodiments of the present invention will be described.

FIG. 2 is a diagram illustrating a method of calculating the actual extrusion amount of the extruder per unit time by moving-averaging the measured values from the weight detection sensor. Hereinafter, description will be made with reference to FIG.

1) The raw material in the hopper 2 is supplied to the extruder 3 according to the operation of the extruder, and the value of the weight signal of the weight detection sensor 7 decreases. 2) Assuming that the set unit time of the weight measurement is T1, the controller 6
, As shown in FIG. 2, measures the weight at each unit time T1, takes in and stores the measured values S1, S2, S3, S4. 3) Arithmetic averaging is performed for each number of moving averages (5 in the figure) of the measurement values taken in each unit time T1. The result is defined as AV1.

4) Next, the old measured value S1 is deleted, and the new measured value S6 is added to calculate the moving average value AV2.
Hereinafter, 2) and 3) are repeated in order, and AV3, AV4,.
Is calculated. 5) Every time the moving average value is obtained, the weight loss amounts △ W1, △ W2, △ W3, △ W4,... For each unit time T1 are obtained and stored in the controller 6. 6) From the time when △ W1 is calculated, the weight reduction amount during the set integration time T2 is calculated as △ W1 + △ W
2 + ΔW3 + ΔW4. △ W1 + found
ΔW2 + ΔW3 + ΔW4 is the weight of the raw material consumed during the integration time T2, that is, the calculated actual extrusion amount. From the obtained value, for example, if T2 is 1 minute, the extrusion rate Q1 (Kg / hr) per hour can be calculated by the following equation (2). Q1 = [(△ W1 + △ W2 + △ W3 + △ W4) ÷ T2] × 60 (2) 60 in the equation (2) is referred to as a time conversion coefficient.

In the present invention 1, the screw rotation speed is adjusted so that the obtained Q1 and the reference extrusion amount QST obtained by the above equation (1) coincide. Specifically, Q1> QST
The adjustment is performed in such a direction that the screw rotation speed is decreased when Q1 <QST, and the screw rotation speed is increased when Q1 <QST. Further, the adjustment amount may be calculated by calculating the ratio of Q1 / QST and multiplying the ratio by the current rotational speed.

As described above, in the apparatus of the present invention 1,
The number of rotations of the screw is adjusted so that the actual extrusion amount Q1, the take-off speed at that time, and the reference extrusion amount calculated from the standard value of the product coincide, and while ensuring the predetermined production amount,
Product thickness is controlled. Similarly, Q2, Q3, Q4
This operation is repeated every time... Is calculated, and the screw rotation speed is automatically adjusted at each calculation time. Therefore, while maintaining a predetermined production amount, fine thickness control is realized, and the product thickness is controlled. The variability is greatly reduced.

In the present invention 2, the difference between the obtained Q1 and the QST obtained by the above equation (1) is compared, and the difference is set and stored in advance, and it is determined whether the difference is within the lower limit. If not, the take-up speed is adjusted by the following method.

The product (film) of the target specification value (width W, thickness D, density ρ of the raw material resin used, etc.) is converted to the above-mentioned extrusion rate Q.
The take-up speed L1 in the case of production at 1 is obtained by the following equation (3).

[0039]

(Equation 1)

In this way, the optimum take-up speed L1 that matches the target product thickness at the actual extrusion amount Q1 is calculated.
Next, a speed adjustment signal is output to the drive motor of the hauling machine so that the hauling speed currently being produced is equal to L1, and the hauling speed is adjusted. Similarly, Q2, Q3, Q4 ...
L2, L3, L4,... Are calculated each time is calculated, and the take-up speed is automatically adjusted at each calculation time, so that fine thickness control is realized and the variation in product thickness is greatly reduced. Decrease.

If the difference between Q1 and QST obtained from the above equation (1) is out of the upper and lower limits, it is expected that the fluctuation of the production amount will be too large by adjusting only the take-off amount. As in Invention 1, the screw rotation speed is adjusted so that Q1 and QST coincide.

As described above, in the present invention 2, since a small change is controlled by adjusting the take-up speed and a large change is controlled by adjusting the screw rotation speed, fine thickness control is realized, and the variation in product thickness is greatly reduced. And a predetermined production amount is secured.

The control adjustment cycle of the apparatus according to the present invention 1 or 2 is determined by the unit time T1, the number of moving averages to be obtained, the integration time T2, and the like. Can be appropriately selected according to the operating conditions of the device, the characteristics of the target product, and the like.

[0044]

The structure of the film thickness control device of the present invention 1 is as described above, and the amount of reduction of the raw material stored in the raw material storage unit per unit time is obtained, and the unit is reduced for a certain time. Since the means for integrating the amount of decrease per time and obtaining the actual amount of extrusion from the result is adopted, the screw speed of the extruder can be adjusted based on the accurately calculated amount of extrusion compared with the conventional automatic controller. Since the adjustment is performed finely, the variation in the thickness of the product is greatly improved, and a predetermined production amount can be secured.

The configuration of the film thickness control device according to the second aspect of the present invention is as described above. Means for calculating the actual extruded amount from the result by integrating the reduced amount of the extruder, so that the screw speed of the extruder can be adjusted or taken over based on the accurately calculated extruded amount compared to a conventional automatic controller. Since the adjustment of the speed is performed finely, the variation in the thickness of the product is greatly improved, and
A predetermined production amount can be secured.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an inflation molding process to which a film thickness control device of the present invention is applied.

FIG. 2 is an explanatory diagram of the operation of the film thickness control device of the present invention.

[Explanation of symbols]

 Reference Signs List 1 raw material tank 2 hopper 3 extruder 4 take-up machine 5 take-up machine 6 controller 7 weight detection sensor 8 width sensor 9 air pump 12 valve 13 mold 14 cylindrical film 15 extruder screw 16 cooling device 17 extruder motor 18A, 18B Guide plate

Claims (2)

[Claims] 1. A cylindrical film obtained by supplying a raw resin stored in a raw material storage section to an extruder, and extruding a molten resin heated and kneaded by the extruder from a die at the tip of the extruder. In the inflation molding step of taking off the raw material by a take-off machine, the weight of the raw material resin stored in the raw material storage section is measured at an arbitrary unit time T1, and the measured value is taken as an arbitrary continuous number to obtain an average weight value. Means for calculating the moving average value by repeating this for each unit time, and calculating the weight loss amount in the unit time T1 by subtracting the moving average value calculated this time from the moving average value calculated last time. A unit time weight loss calculating means to be stored; and a plurality of unit time weight loss values sequentially obtained by the above means are added to a number corresponding to an arbitrary integration time T2 to obtain a weight per integration time. Means for calculating the amount of decrease in amount and calculating the amount of extrusion of the extruder per unit time; means for detecting the take-up speed of the take-off machine; means for detecting the width of the cylindrical film being formed; Means for calculating and storing a reference extrusion rate per unit time for the thickness to match the specification value from the take-off speed, width, and a preset specification value of the cylindrical film; and A film thickness control device in an inflation molding process, comprising: means for outputting a speed adjustment signal to a motor of an extruder so that the extruded amounts coincide with each other to adjust the number of rotations of a screw of the extruder. 2. A cylindrical film obtained by supplying a raw material resin stored in a raw material storage section to an extruder, and extruding a molten resin heated and kneaded by the extruder from a die at the tip of the extruder. In the inflation molding step of taking off the raw material by a take-off machine, the weight of the raw material resin stored in the raw material storage section is measured at an arbitrary unit time T1, and the measured value is taken as an arbitrary continuous number to obtain an average weight value. Means for calculating the moving average value by repeating this for each unit time, and calculating the weight loss amount in the unit time T1 by subtracting the moving average value calculated this time from the moving average value calculated last time. A unit time weight loss calculating means to be stored; and a plurality of unit time weight loss values sequentially obtained by the above means are added to a number corresponding to an arbitrary integration time T2 to obtain a weight per integration time. Means for calculating the amount of decrease in amount and calculating the amount of extrusion of the extruder per unit time; means for detecting the take-up speed of the take-off machine; means for detecting the width of the cylindrical film being formed; Means for calculating and storing a standard extrusion rate per unit time for the thickness to match the standard value from the take-off speed, width, and a preset standard value of the cylindrical film; Means for setting and storing an upper limit value and a lower limit value; means for comparing the calculated extruded amount with a reference extruded amount to determine whether the difference is within the upper and lower limit values; If the value is within the range, a speed adjustment signal is output to the motor of the take-off machine to adjust the take-up speed. Outputs the speed adjustment signal to the motor of the extruder and rotates the screw of the extruder. A film thickness control device in an inflation molding process, comprising means for adjusting the number.