JPS615916A - Controlling method of thickness of plastic sheet and the like - Google Patents

Abstract

PURPOSE:To reduce wasteful time and to bear high frequency variation in the control of thickness by moving a thickness gauge in the width direction of a sheet, inputting measured values into a moving average computing element to calculate the mean value of reciprocating times in the width direction and feeding it back to control the thickness. CONSTITUTION:Thickness gauges 14, 15 are moved to the running sheet 10 extruded by the die 12 and run in the width direction of the sheet 10 to measure the thickness and a wasteful time compensating circuit considering the distance between the die 12 and the thickness gauges 14, 15 are equipped to control the thickness of the sheet. In this case the thickness gauges 14, 15 are moved in the width direction of the sheet 10, the sampled results are inputted into the moving average computing element to calculate the moving average of a reciprocation in the width direction of the sheet 10, this average is compared with the target value set and feedback signals are outputted to control the thickness.

Description

[Detailed Description of the Invention] ・Technical Field> The present invention applies to a plastic sheet, etc. (hereinafter simply referred to as a sheet, etc.) that is discharged from a die and runs while displacing a thickness gauge in the width direction of the sheet, etc. The present invention relates to an improvement in a method for controlling the thickness of sheets, etc. (hereinafter referred to as MD control) for adjusting the thickness in the machine direction.

<Prior Art> Conventionally, it has been required for product management to measure the thickness distribution (generally referred to as profile) in the width direction of sheets etc. that are continuously manufactured using an extrusion molding machine. For example, to measure such a profile, we will use a scanning transmission type thickness gauge that is equipped with a measurement head that moves back and forth in a part of the product conveyance path. 1
To explain with reference to the drawings, numeral 10 in FIG. 1 indicates a sheet etc. that is continuously extruded from a forming die 12 attached to an extruder 11 and manufactured through a forming roll I3 driven by a motor 26. A pair of light projector 14 and light receiver 15 are provided on a part of the conveyance path of the sheet etc. 10 and reciprocate in the width direction thereof.
A transmission type thickness gauge 16 is provided with a measuring head consisting of. The transmission type thickness gauge 16 also includes 1.
A scanning motor 17 is provided for reciprocating and scanning the board in the width direction of the sheet, etc., and this scanning motor 17 is controlled by an external controller to be described later.

However, the external controller that controls the scanning motor 17 controls the speed regulator 18, the motor controller 19, the position setting device 2o, and the measurement head position signal X obtained from the transmission thickness gauge 16. Input converter 21 and comparison calculator 22
It consists of

Therefore, in the comparator 22, the feedback position signal x5 of the measuring head obtained via the converter 21 is
and the position signal for setting the turning point of the measuring head set by the position setting device 2o, and the signal obtained by the comparison calculator 22 and the speed adjustment signal from the speed adjuster 18 are sent to the motor controller. 19 to supply a predetermined motor control signal C8 to the scanning motor 17.

Incidentally, from the transmission type thickness gauge 16, 10 thickness signals 1s such as 7 totes are taken out along with 5 position signals of the measurement head. This thickness signal 1. is connected to a recording device 2 such as a converter stem via a conversion amplifier 23 and a small food changer 24.
5, position data and thickness data are stored and held in correspondence with each other. The recording device 25 includes a CPU 27, an internal storage device 28, peripheral devices 29, a timer 30, and the like.

However, this device does not use a transmission thickness gauge 16 due to the long distance from the die 12, which is the molding part, to the thickness gauge 16, and the scanning period of the thickness gauge that moves in the width direction. Even if the detected results are fed through the recording device 25 to the drive motor 31 of the extruder 11 or the motor for driving a die port (not shown) for adjusting the lip of the die part, the distance between the sheet etc. Parts are not adjusted. That is, only during this period, even though the die lip is adjusted, its effect does not appear. Kneading is called wasted time.

Conventionally, Smith's method is known as a dead time compensation circuit for control to correct this dead time.

This method (According to After the measuring head of the measuring device reaches the turning point, the measurement signal of the average thickness is calculated and output as a periodic average. As the measuring head moves from point A-B-C-4D, the changed thickness is
When the measuring head reaches point A, which is the end point of 1 zone, calculate the thickness 11, assuming the thickness of Sl as Y average, and when the measuring head reaches point B, which is the end point of 82 zones, as the average thickness of 82 zones. 12 is calculated, and 13...1o is calculated in the same manner. This average thickness 13,1□...io appears as a discontinuous step-like graph b. Therefore, the measurement results cannot be determined while the rad is moving in the width direction of the sheet, etc., and cannot be determined until it reaches the turning point.

In addition, for items with large thickness changes, that is, items expressed by high frequencies, the results will not appear until the measurement head reaches the turning point, so the response will be delayed, and by the time one phenomenon is fed back, other phenomena are already reflected. This is a situation where a phenomenon has occurred and another feedback signal is required.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned problems and provides an MD control method that eliminates dead time as much as possible and adjusts the thickness of a sheet etc. so as to cope with high frequency fluctuations. It is about providing.

<Structure of the Invention> In order to accomplish this purpose, the inventors used an MD control method that includes a dead time compensation circuit, and also moved a thickness sensor that measures the thickness of a sheet, etc. in the width direction of the sheet, etc., and sampled the results. is input into the moving average calculator, calculates the moving average of one round trip in the width direction of the sheet, etc., constantly compares it with a preset target setting value, and outputs a feedback signal.
An object of the present invention is to provide a thickness control method that performs MI) control.

<Example> Next, the present invention will be explained in detail with reference to FIGS. 3 and 4. Items having the same numbers as those in FIG. Only the equipment will be explained. 31 is shown in FIG. 3 41) Controller 32;
This is a control circuit consisting of a dead time compensation circuit 33 and a target thickness setter 34 for setting a predetermined target thickness. 3′
Reference numeral 5 denotes a moving average calculator which manually inputs the thickness signal 1 detected by the thickness gauge 16 and the detected position signal
The output signal is applied to the output signal. Here, the moving average calculator 35 is placed separately from the storage device 25 such as a computer/stem, but it is not limited to this and may be placed in the same device 25. 36 indicates a process and detects the thickness of a sheet, etc. A speed meter 263 (not shown) that detects the speed of the thickness gauge 16 and the motor 26 detects the thickness and speed of the sheet, etc., respectively.

The method of the present invention is constructed as described above.9 Next, the operation and action of the method of the present invention will be explained with reference to the flowchart of FIG. N pieces every 1 an (N, , N2.N
5-N,) and its thickness +(+,,I,,,+3=+
, ). Next, move C to measure the thickness gauge, and then determine whether or not the position signal N has changed (for example, whether it has changed from N1 to N2 and is 7), and if YT/:S, move. In the example of inputting the thickness signal with ゛ and calculating the moving average with d, the average calculator adds 1/N of the thickness data just input to the current moving average, and calculates the thickness data of J cycles ago. 1/
Determine the moving average value by subtracting /N (・Determine the new moving average value of the lever, then update the memory contents not shown in the diagram with f. Go to measurement with g, cross the width of the sheet, etc. It is determined whether or not it has passed the turning point in order to cross the width of the sheet, etc. again, and h is used to determine whether the measuring head is moving in the opposite direction from the current 1. .3・
The measuring head, which has moved forward n, now changes direction and moves forward n (
n-l) ・Reverse as shown in 3.2.1 and repeat
).

<Effects of the Invention> Tests performed as described above]-results, Fig. 6 (a), (mouth j, ←ri, * and Fig. 7 (a), (river,
Assuming that the change in the thickness of the sheet etc. in the direction of the running force becomes a 5-inch curve as shown in (A), as shown by Kamoya, the conventional device has an average thickness of 1 in each direction as shown in (C). At the turning point in the opposite direction, it turned into a staircase, but this can be understood by the method of the present invention. Similarly, FIG. 6 shows an example of a high frequency case, where, as in the previous embodiment, the conventional method is represented by a stepped average value, and the method of the present invention is represented by a smooth continuous curve.

In this way, the present invention eliminates the drawbacks listed at the beginning, and allows the average thickness of the sheet, etc. at each position to be expressed as a smooth continuous value, making it possible to perform accurate thickness adjustment control with no dead time. It became so.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a thickness adjustment control device according to a conventional method. FIG. 2 is a graph showing the average thickness of sheets, etc., obtained using a conventional device. 3 and 4 are diagrams of an apparatus showing one embodiment for carrying out the method of the present invention, and FIG. 3 is an overall view. Figure 4 is a detailed diagram. FIG. 5 is a flowchart showing the operation in the embodiment of the present invention. FIGS. 6 and 7 are graphs showing the test results of calculating the average thickness of sheets, etc. using the method according to the present invention.

Claims (1)

[Claims] Thickness control for sheets, etc., in which the thickness of the sheet, etc. in the flow direction is adjusted by displacing a thickness gauge in the width direction of the sheet, etc., with respect to the traveling plastic sheet, etc. discharged from a die equipped with a dead time compensation circuit. In the method, the thickness at a predetermined location on a sheet, etc. is sampled using the thickness meter, the sampled value is input to a moving average calculator, and the moving average of the thickness of one round trip in the width direction of the sheet, etc. is calculated. A method for controlling the thickness of a sheet, etc., in which the calculated value is always compared with a preset target setting value, and the result is fed back to a drive source such as a motor for controlling the thickness of the sheet, etc.