JPH03261539A - Amount of extrusion-controlling apparatus for inflation film manufacturing machine - Google Patents

Abstract

PURPOSE:To prepare stably a film with a preset thickness and width by controlling the number of rotation of a screw motor in such a way that the mean amt. of consumption of a material coincides with the aimed amt. of consumption by calculating the aimed amt. of material consumption from data on the draw-off speed of the film, the thickness, the width etc., of the film to be prepd. CONSTITUTION:A signal exhibiting the wt. of a metering hopper is output by a metering sensor and the signal is taken in a calculating means 1 calculating an amt. of material consumption at every const. time and the amt. of material consumption at every const. time is calculated by reducing the present value of wt. from the preceeding value of wt. obtd. from the signal. Then, a calculating means 2 calculating the mean amt. of consumption calculates the mean amt. of consumption per unit time from data on the amt. of material consumption at every const. time and a calculating means 3 calculating the aimed amt. of consumption calculates the draw-off speed of the film calculated from the detected signal of a pinch roll-rotating sensor 15 and the aimed amt. of material consumption from data on thickness, width etc., of the film to be prepd. The controlling means 5 controlling the screw motor controls the number of rotation of the screw motor 32 while the rotating speed of the screw is watched in such a way that the mean amt. of consumption coincides with the aimed amt. of consumption.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an extrusion rate control device used in a film manufacturing machine for manufacturing a cylindrical blown film and for controlling the amount of material extruded by a screw extruder. .

<Conventional technology> A blown film manufacturing machine continuously extrudes thermoplastic resin from an inflation die into a cylindrical film using a screw extruder, supplies gas into the cylindrical film to create bubbles, and continuously extrudes the film. This device manufactures stacked tube-shaped films while taking the blown film, and in order to keep the thickness of the blown film constant, the speed at which the film is taken is controlled.

<Problems to be Solved by the Invention> However, conventional control devices for controlling this type of take-up speed do not measure the time consumed per unit weight of material in the material hopper extruded by the screw extruder. The structure controls the consumption time (accordingly, the number of rotations of the pinch rolls that take off the film, that is, the take-up speed. Therefore, this control device cannot accurately measure the amount of resin material consumed, so extrusion There was a LI problem in that it was not possible to control the amount of material consumed by the machine, that is, the amount of material extruded, resulting in variations in film thickness and making it difficult to produce films of stable quality.

The present invention was made to solve the above problems, and it is possible to accurately control the amount of material extruded according to the amount of resin material consumed, and to manufacture a film of excellent quality with a constant thickness. #li is the extrusion rate control device for blown film manufacturing machines that can be used! The purpose is to provide

Means for Solving the Problems> In order to achieve the above object, the extrusion rate control device for a blown film manufacturing machine of the present invention, as shown in FIG. A weighing sensor 7 that measures the 0 weight of the weighing hopper to be sent and outputs a signal indicating the weight, and a signal from the weighing sensor 7 is taken in at regular intervals, and the current value is subtracted from the previous weight value obtained from the signal. A material consumption calculation means 1 for calculating the material consumption per fixed time; an average consumption calculation means 2 for calculating the average consumption per unit time from the material consumption data for each fixed time; A screw motor 32 that rotationally drives the screw of the extruder, a pinch roll rotation sensor 15 that outputs a signal with a frequency corresponding to the rotational speed of the pinch roll that rotates to cut off the film extruded from the extruder, and a pinch roll A target consumption calculation means calculates a target consumption amount of material from data such as the film take-up speed calculated from the detection signal of the rotation sensor 15 and the thickness and width of the film to be manufactured, and an average consumption amount is calculated from the target consumption amount. screw motor control means 5 for controlling the rotation speed of the screw motor 32 to match the rotation speed of the screw motor 32.

<Function> While the blown film manufacturing machine is automatically operated,
The weighing sensor 7 outputs a signal indicating the weight of the weighing hopper, and the material consumption calculation means 1 receives the signal at regular intervals and subtracts the current value from the previous weight value obtained from the signal. , calculates the material consumption amount for each fixed time.Next, the average consumption amount calculation means 2 calculates the average consumption amount per unit time from the material consumption data for each fixed time, and the target consumption amount calculation means 4, Pinch roll rotation sensor 15
The target material consumption amount is calculated from the film take-up speed calculated from the detection signal and data such as the thickness and width of the film to be manufactured. Then, the screw motor control means 5 controls the rotation speed of the screw motor 32 to match the average consumption amount to the target consumption amount while monitoring the rotation speed of the screw, thereby keeping the extrusion amount of the material constant. It is possible to stably produce a film with a set thickness.

<Example> Embodiments of the present invention will be described below based on the drawings.

FIG. 2 shows a schematic diagram of the blown film manufacturing machine. First, the outline of the blown film manufacturing machine will be explained with reference to this figure. Reference numeral 31 is a blown film extruder, which is rotatably driven by a screw motor 32 and has a built-in screw for extruding the synthetic resin material. A screw rotation sensor 33 is attached that outputs a pulse signal according to the rotation speed.

A weighing hopper 6 is disposed above the material supply port of the extruder 31 so that its weight can be measured by a weighing sensor 7 such as a load cell, and a feeder 4 for supplying the material is provided above the weighing hopper 6. A gate that is opened and closed by a material supply solenoid 35 is provided at the bottom of the feeder 34 .

A blow head 9 with a built-in die is vertically attached to the extrusion side of the extrusion tli 31 via a pipe 8, and the blow head 9 is equipped with a pump for blowing air into the extruded film to create a tube-shaped bubble. 10. Blower 11 for air ring, ie for air cooling around the bubble
is connected.

Above the blow head 9, a stabilizer plate 12 and a pinch roll 13 are disposed for sandwiching a thin film from both sides, folding it into a sheet shape, and taking it off. This pinch roll 13 is driven by a pinch roll motor 14, and the pinch roll 13 is provided with a pinch roll rotation sensor 15 that generates a pulse signal of a frequency corresponding to the rotation speed of the pinch roll 13.

The film picked up by the pinch roll 13 is sent to the second pinch roll 17 via the guide roll 16,
It is wound up on the winding m19. The second pinch roll 17 is the second
The above pinch roll 13 is driven by the pinch roll motor 18.
It is rotated at a speed that is the rotational speed of , plus a correction.

FIG. 3 shows a block diagram of an extrusion rate control device in a blown film manufacturing machine.

This control device is composed of a microcomputer as a main part, and 21 is a CPU, which executes film take-up control as described below based on control program data stored in advance in a ROM 22.

23 is a RAM that can be written to and read out at any time, and stores measurement data input from various sensors, various preset values and constants, numerical values necessary for calculations, calculation results, etc. This RAM 23 is backed up by a battery.

24 is an input/output circuit to which various sensors and actuators are connected, including a sensor amplifier, a D-A converter, and an A-
Includes D converter, motor drive driver, servo amplifier, etc. CPU21, ROM22, RAM23
, the input/output circuits 24 are interconnected via a common bus,
Data, address signals, and control signals are mutually transmitted.

The above-mentioned weighing sensor 7, screw rotation sensor 33, pinch roll rotation sensor 15, material supply solenoid 35, screw motor 32, pinch roll motor 14, and second pinch roll motor 18 are each connected to the input/output circuit 24.

Further, a group of operation switches 25 and a display 26 such as a plasma display, which are arranged on an operation panel (not shown), are connected to the input/output circuit 24. The operation switch group 25 includes a changeover switch that changes the pinch roll between manual and automatic, a changeover switch that changes the screw between manual and automatic, a metering switch that only performs weighing operation in the preparation stage, and an automatic operation switch that starts automatic operation. , a production start switch to start production, a stop switch to stop operation, a variable screw switch that gradually changes the rotation of the screw during control, a variable pinch roll switch that gradually changes the rotation of the pinch roll, various types. A switch such as a numeric keypad is provided for manually inputting set values.

In addition to the above-mentioned control system, the control device of this blown film manufacturing machine can also be provided with a frost line control device, a film width control device, and the like.

Next, the operation of the extrusion rate control device having the above configuration will be explained based on the flowchart shown in FIG.

Prior to the operation of the blown film manufacturing machine, data and setting values such as the thickness, width, and length of the film to be manufactured are manually entered into the control device using a numeric keypad or the like, and stored in the RAM 23. Then, the extruder 31 is started, and the tJ
During setup, the tube-shaped film 30 extruded from the extruder 31 is pinched from the stabilizer 12 while the screw motor 32, pinch roll motor 14, and second pinch roll motor 18 are in a state where they can be manually adjusted. It is passed between rolls 13, passed through guide rolls 16, passed between second pinch rolls 17, and led to a winder 19. During this time,
Air is sent into and out of the tube from a pump 10 and a blower 11 to create a bubble above the blow head 9.

When the weighing switch of the control device is turned on while the manufacturing machine is in preparatory operation, the CPU 21 executes step 100.
Step 120 is executed from then on, and the current material consumption is calculated based on the hopper weight data sent from the weighing sensor 7. In other words, the CPU 21
The data of the hopper weight is taken in from the weighing sensor 7 every second), and the current value is subtracted from the previous value to calculate the material consumption per second.Step 110), these data are sequentially stored in the buffer memory, and further, for example, The average consumption amount per minute is calculated every second (step 120). Furthermore, when the weight of the weighing hopper 6 becomes lighter than a certain value, the material from the feeder 34 is transferred to the weighing hopper by the operation of the material supply solenoid 35. However, when the material is introduced into the hopper 6, the measuring operation is not performed for, for example, 10 seconds.

At this stage of preparatory operation, the rotational speed of the screw pinch roll 14 and second pinch roll 18 of the extruder I+131 is gradually increased by the operator's manual switch operation. is operated, the process proceeds from step 130 to step 140 as an adjustment operation is performed, and depending on these switch operations, the rotational speeds of the screw of the extruder 31, the pinch roll 13, and the second pinch roll are set close to the actual film production operation. Adjust (speed up) until the condition is reached.

Then, when the screw rotation speed of extrusion @31 and the film take-up speed reach appropriate speeds, the automatic switch is turned on, and steps 150 to 160 and 17
Go to 0 and same as above.

The current material consumption is calculated based on the hopper weight data sent from the weighing sensor 7 (step 160),
Furthermore, for example, the average consumption per minute is calculated every second (step 170) and, in step 180, the target consumption of material (g/min) depending on the take-up speed of the film.
is calculated, and this target consumption is determined by the film take-up speed (
m/min) x 2 x film width x film thickness x film specific gravity x correction value.

Here, the film take-up speed (m/min) is determined by counting the detection signal (pulse signal) output from the pinch roll rotation sensor 15, and calculating the film take-up speed from the number of pulses and the diameter of the pinch roll. Further, the rotational speed of the screw is calculated by an interrupt process that is interrupted by a detection signal (pulse signal) from the screw rotation sensor 33, and measures the time from one pulse signal to the next pulse signal.
The average rotational speed of the screw at fixed time intervals is calculated.

Then, in step 190, control data for speed increase or deceleration is created so as to match the average material consumption calculated in step 170 with the target consumption calculated in step 180. That is, the command rotation speed is calculated from the formula: target consumption x average screw rotation speed ÷ average consumption.
The screw motor 32 is controlled and driven by outputting the control data of this command rotation speed.

Normally, at this stage, the actual average consumption is lower than the target consumption, and the screw motor 32 is controlled to increase its speed, but if the screw speed is greatly increased in a short period of time, wrinkles will occur in the film. Since such problems occur, smoothing processing is used to smoothly change the speed. That is, the control value of the screw motor 32 (for example, 0 to 1
0v voltage value) into multiple parts within a set time width,
A control signal is generated so that the speed increasing type is decelerated stepwise from the IIIJ all value to the target value. and,
This control signal is output to the screw motor 32, and the rotation of the screw is controlled so that the target consumption amount is gradually obtained.

In this automatic control mode, the rotation speed of the pinch roll 13 is constant and the pinch roll rotation speed is displayed on the display 26, but the pinch roll rotation speed can be adjusted by operating the pinch roll enable f switch. . If this pinch roll variable switch is operated, step 20
The process proceeds from 0 to 210, and outputs a speed increase or deceleration control signal to the pinch roll motor 32 to adjust the pinch roll rotation speed.

When the rotation speed of the pinch roll motor 14 is changed, the film take-up speed is changed. For this reason, the control device operates to control the screw of the extruder 31 in order to realize the target consumption amount according to the withdrawal speed, but as described above,
Hopper weight data is taken in from the weighing sensor 7 at regular intervals (for example, every second), the current value is subtracted from the previous value to calculate the material consumption per second, and these are sequentially stored in the buffer memory, Furthermore, since the average consumption amount per minute is calculated every second, it takes some time for the average consumption amount to reach the original target consumption amount.

Therefore, during such pinch roll rotation adjustment during automatic operation, all material consumption data in the buffer memory is replaced with the latest consumption data by operating a specific switch (for example, a rapid start switch). By doing so, the average amount of material consumed can be calculated quickly, and the start-up time during preparatory operation can be shortened.

After that, if the production start switch is not turned on, the process returns to step 160 and the steps 160 to 19 are repeated as described above.
0 is executed, and the current consumption amount of the material, its average consumption amount, and the target consumption amount according to the film transaction speed are repeatedly calculated, but by changing the number of rotations of the pinch rolls,
When the target consumption amount of the material changes, the rotation of the C screw is controlled to match the average consumption amount to the target consumption amount.

On the other hand, although not shown in the flowchart of FIG. 4, the rotation speed of the second pinch roll 17 located downstream of the pinch roll 13 is also controlled by this control device.
The command rotation speed of the second pinch roll 17 is the pinch roll 1
3, and the second pinch roll motor 18 is controlled to reach that rotation speed. The correction coefficient is determined, for example, from table data of correction coefficients stored in the memory in advance according to the thickness and width of the film to be manufactured. Normally, as the thickness and width of the film increase, the shrinkage of the film occurs between the pinch rolls 13 and the second pinch rolls 17. Therefore, in such a case, the rotation speed of the S2 pinch roll 17 is controlled to be 1 to 2% lower than the rotation speed of the pinch roll 13,
The correction coefficient becomes a negative value.

In this way, when the operation of the blown film manufacturing machine becomes stable and the average consumption of material reaches the target consumption, the preparatory operation is finished and the production start switch is turned on.
Start actual production operation. Here, steps 220 to 2
30 to begin measuring the production length of film 30. The length of the film 30 is the length of the pinch roll rotation sensor 1.
The number of rotations of the pinch roll sent from 5, that is, the number of pulse signals corresponding to the length of the film to be taken, is calculated and integrated.

During production operation, steps 160 to 240 are repeatedly executed, and the rotation of the screw of the extruder is controlled so that the material consumption of the extruder 31 becomes the target consumption according to the take-up speed of the pinch rolls 13. be exposed. When the rotation of the pinch rolls 13 is constant, the amount of material extruded is controlled to be constant, and a film with a constant thickness and width is stably produced.

When the production length of the film reaches the preset unit production length, a turn signal for replacing the winding core is output to the winding machine to replace the winding core, or the entire production length is If the limit has been reached, production is terminated (step 240).

In this way, the amount of material consumed per certain period of time is measured, the average amount of material consumed per unit time is calculated, and the amount of material consumed per unit time is calculated.
The target consumption amount of the material is calculated from the take-up speed according to step 3, and the drive of the screw generator 32 is controlled so that the average consumption amount matches the target consumption amount, so that films of a constant thickness and width can be stably produced. can do.

<Effects of the Invention> As explained above, according to the extrusion rate control device of the blown film manufacturing machine of the present invention, the material consumption calculation means 1 receives the signal from the weighing sensor that measures the weight of the hopper into which the material is placed. By subtracting the current value from the previous value of the weight acquired from the signal at a fixed time interval, the material consumption at a fixed time interval is calculated, and the average consumption amount calculation means 2 calculates the material consumption at a fixed time interval. The average consumption amount per unit time is calculated from the amount data, and the target consumption amount calculation means 4 calculates the film take-up speed calculated from the detection signal of the pinch roll rotation sensor 15, the thickness of the film to be manufactured,
Calculate the target material consumption from data such as width, and
Since the screw motor control means 5 is configured to control the rotation speed of the screw motor 32 so as to match the average consumption amount to the target consumption amount while monitoring the rotation speed of the screenie, it is possible to control the rotation speed of the screw motor 32 to adjust the film take-up speed. IIIJ all so that the amount of material extruded is exactly constant accordingly,
Films with preset thickness and width can be stably produced.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the present invention, Figs. 2 to 4 show examples of the present invention, Fig. 2 is a schematic block diagram of a blown film manufacturing machine, and Fig. 3 is a block diagram of an extrusion rate control device. , FIG. 4 is a flowchart showing the operation of the extrusion rate control device. DESCRIPTION OF SYMBOLS 1... Material consumption calculation means, 2... Average consumption calculation means, 4... Target consumption calculation means, 5... Screw motor control means, 7... Weighing sensor, 15... Pinch roll rotation sensor, 32...screw motor. First patent applicant ■

Claims (1)

[Scope of Claims] A weighing sensor that measures the weight of a weighing hopper that sends material to an extruder of a blown film manufacturing machine and outputs a signal indicating the weight; a material consumption calculation means for calculating the amount of material consumption for each given time by subtracting the current value from the previous value of the weight obtained from the above; average consumption calculation means for calculating the amount; a screw motor for rotationally driving the screw of the extruder; and a signal having a frequency corresponding to the rotational speed of a pinch roll that rotates to take up the film extruded from the extruder. A target consumption amount calculating means for calculating a target consumption amount of material from data such as the output pinch roll rotation sensor, the film take-up speed calculated from the detection signal of the pinch roll rotation sensor, and the thickness and width of the film to be manufactured. An extrusion amount control device for a blown film manufacturing machine, comprising: a screw motor control means for controlling the rotation speed of the screw motor so as to match the average consumption amount to the target consumption amount.