JPH0684037B2 - Extruder control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for controlling an extrusion molding machine, an injection molding machine and a blow molding machine (hereinafter collectively referred to as an extruder etc.) for molding a molten plastic material. In particular, in order to perform high-quality molding, a barrier for forming a solid groove and a melt groove between the inner surface of the barrel and a main flight and a barrier flight (sub-flight) are provided in the screw for extruding and melting the material. The present invention relates to a control method for an extruder or the like using a screw of a rectangular shape.

[Conventional technology]

The goal of control of extruders, etc., is to set the barrel temperature appropriately by using an appropriately designed extrusion screw, and to uniformly and stably supply the molten material of a predetermined extrusion amount to the next step. . Therefore, in the initial stage, constant value control of the pressure and temperature of the molten material in the screw head portion was performed.
However, it has been found that this control alone has a limit and sometimes has an adverse effect of promoting instability of melting. In other words, this is due to the phenomenon of breakup of the solid bed, which generally means the dismantling of solid unmelted material, but in the groove of the screw, the solid material gradually melts through the supply section, compression section, and measurement section. This shows an unstable state of melting that occurs during the melting process in which the material changes. In order to avoid such a phenomenon, a barrier flight is newly provided with a barrier flight as a shelf for separating a solid component and a molten component in the melting promoting portion which occupies the longest portion of the screw. The improvement effect of this new barrier type screw was remarkable, but what further expanded this effect is the following diagnostic control system.

That is, the applicant of the present invention has previously responded to other instabilities including the break-up of the solid bed by using a signal from the pressure sensor provided in the melting promoting portion and the position sensor provided at the driving end of the screw. Automatic diagnosis of melting process that detects waveforms, compares and compares them with predetermined reference data, calculates the statistics of their correlation, determines normality or abnormality, and performs additional test in case of abnormality Proposed a control system, Japanese Patent Application No. 60-81369 (Japanese Patent Publication No. 2-580)
No. 92) filed a patent application.

[Problems to be solved by the invention]

However, in the automatic diagnostic control system,
The control for setting the barrel temperature, which is essential for determining abnormalities, is not clear. Conventionally, the value of the pressure in the melt groove is not uniquely determined, and varies depending on the screw structure, material characteristics, screw rotation speed, and the like, and cannot be considered as a guide for control. However, after that, according to the diagnosis result of the automatic diagnosis control system, once the above-mentioned specifications are selected, it has become clear that the pressure in the melt groove is almost constant in the normal melting process. Further, according to the diagnosis result, a model diagram showing a molten state in the screw groove shown in FIG. 8 can be considered. 8 (a), (b) and (c), reference numeral 10 is a barrel, 12 is a screw, 60 is a main flight, 62 is a barrier flight, 56 is a solid groove, and 58 is a melt groove. In FIG. 8 (a), the melt component is not sufficiently filled, and the melt component does not fill the melt groove 58, and it is necessary to raise the barrel set temperature. When it is operated to, the excessive melting state as shown in FIG. 8 (c) is generated, and break-up of the solid bed occurs, which has the opposite effect. Qualitatively,
As long as the condition that the melt component and the solid component are clearly separated by the barrier flight 62 is satisfied, the higher the melt groove pressure, the better the result. This is the proper melting state of FIG. 8 (b). It has also been clarified that the minute range in which this determination suffers is a state where the pressure waveform of the automatic diagnostic control system is determined to be normal.

Therefore, an object of the present invention is to confirm the barrel set temperature related to the melting process of an extruder having a barrier type screw by the automatic diagnostic control system to confirm that the melting process is normal, and then to determine the melt groove pressure. The object of the present invention is to provide a control method for an extruder or the like that can clarify the target value of and optimize the target value as the reference pressure.

[Means for solving problems]

Therefore, the control method of the extruder or the like according to the present invention is such that the plastic solid material that is divided and supplied into the temperature-controlled barrel is extruded and melted by the rotation of the screw provided with the main flight and the barrier flight, and this extrusion is performed. In a method of controlling an extruder or the like for extrusion molding, injection molding or blow molding of a molten material that has undergone a melting step, a pressure waveform composed of a pressure inside the melt groove and a pressure inside the solid groove in the melt promoting portion of the screw is the barrier flight and the above. The measurement is performed in relation to the position of each main flight and sampling is performed, and when the melting process is determined to be normal based on this sampling data, the deviation from the target value of the pressure in the melt groove is obtained, and this deviation is the allowable pressure value. When the temperature exceeds the melting point, the barrel set temperature in the barrel temperature control zone close to the melting accelerator is controlled. , And maintains the melt groove pressure within a certain range.

Further, in the control method of the extruder or the like, a pressure signal indicating the pressure in the melt groove and the pressure in the solid groove from a pressure sensor is selectively input through a signal processor.
Input sampling data to CPU via A / D converter,
A position signal indicating the position of the barrier flight and the main flight from the position sensor is directly input to the CPU, and when the melting process is judged to be normal by the comparison of the pressure waveforms, the deviation of the melt groove pressure is the pressure. A calculation is performed to update the barrel set temperature so as not to exceed the allowable value, and the updated temperature signal is output to the temperature controller in the barrel temperature control zone adjacent to the melting promoting section via the output interface.

In the method of controlling the extruder or the like, the temperature of the molten material in the screw head portion is further measured to obtain a deviation between this temperature and a set temperature, and when the deviation exceeds a temperature allowable value, the head portion is It is preferable to control the barrel set temperature of the barrel temperature control zone close to the above to maintain the temperature of the molten material in the head portion within a certain range.

[Action]

According to the control method for an extruder or the like according to the present invention, in an extruder or the like that is normally operating, if any abnormality occurs in the melting process, an abnormality occurs in the pressure waveform based on the sampling data from each sensor. When this happens, the automatic diagnosis control system detects an abnormality and outputs an alarm or takes a first-aid measure for slowdown. If the pressure waveform returns to normal during the recovery process, deviations from the target values are required for both the melt groove pressure and the temperature of the molten material in the screw head, and these deviations are maintained within the pressure and temperature allowable range. As described above, the barrel set temperatures of the barrel temperature control zones near the melting promoting portion and the head portion of the screw are controlled to the optimum values. In this way, the setting of the pressure in the melt groove, which has been difficult to judge in the past, can be determined in a short time of operation, and control can be performed using this as a guide to maximize the overall performance of the extruder.

〔Example〕

Next, an embodiment of a method for controlling an extruder or the like according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram showing an embodiment of an extruder for carrying out a method for controlling an extruder and the like according to the present invention. In FIG. 1, reference numeral 10 indicates a barrel, and a screw 12 is inserted and arranged inside the barrel 10. A T die 14 as an extrusion mold is provided at the head portion of the screw 12.
The base of the screw 12 is connected to the drive motor 18 via the speed reducer 16. Further, a heater 20 for heating is attached to the outer periphery of the barrel 10, and a temperature sensor is appropriately provided in the vicinity thereof, and these are temperature controllers 21, 22, 23, 2
It is controlled separately by 5 and 27. An external cooling fan 24 is appropriately provided for the heater 20,
A hopper 11 for supplying a plastic solid material is provided on the base side of the screw 12. Main flight to screw 12
60 and a barrier flight 62 are provided, and the place where these two types of flights are provided is the melting promoting portion of the screw 12, and the melt groove 58 and the solid groove 56 shown in FIG. Pressure sensor 26 for detecting internal pressure
Is provided. Further, the barrel 10 corresponding to the head portion of the screw 12 is provided with a temperature sensor 28 for detecting the temperature of the molten material. A position sensor 30 that detects the positions of the main flight 60 and the barrier flight 62 is provided at the end 12a of the base of the screw 12. The signals detected by the pressure sensor 26 and the temperature sensor 28 are supplied to the signal processor 32 and the signal processor 32, respectively.
A / D converter 3 selectively by multiplexer 36 via 34
It is supplied to 8 and becomes sampling data and is input to CPU 40. On the other hand, the signal from the position sensor 30 is directly input to the CPU 40 via the signal processor 42. These input data are
It is stored in the internal memory 44. Eventually, these pressure waveforms and temperatures are compared with the reference pressure data and the target temperature stored and stored in advance. CPU40 has a CRT display 46
An output device such as a printer or a printer 48, an input setting device including a keyboard 53, and an external memory such as a floppy disk 50 are appropriately connected. Further, to the CPU 40, temperature controllers 21, 22, 23, 25 and 27 are selectively connected via a buzzer 54 that issues an abnormal alarm via an output interface 52 and further via a multiplexer 51.

Next, the detailed relational arrangement between the pressure sensor 26 and the screw 12 is as shown in FIGS. 4 (a) and 4 (b).
In FIGS. 4A and 4B, when the screw 12 rotates, the pressure sensor 26 detects the pressure inside the melt groove 58 from the barrier flight 62 to the main flight 60, and when the screw 12 further rotates, the pressure sensor 26 moves from the main flight 60 to the barrier. The pressure inside the solid groove 56 over the flight 62 is detected. Also the position sensor
As shown in FIG. 5 (a), the reference numeral 30 is provided so as to face the signal generating collar 64 attached to the screw end 12a, and as shown in FIG. 5 (b) depending on the rotational deviation thereof. Generates flight position signals. Therefore, as the position sensor 30, for example, a proximity switch can be preferably used.

Next, regarding the control method of the extruder configured as described above,
A description will be given based on the operation.

First, the barrel temperature is raised to a predetermined set temperature, the rotation speed of the screw 12 is maintained at a predetermined rotation speed, and the solid plastic material is supplied. If there is no abnormality in the melting process, the pressure in the melt groove and the pressure in the solid groove are measured by the pressure sensor 26 in relation to the barrier flight position and the main flight position, and sampling is performed. Also, by the temperature sensor 28,
The temperature of the molten material in the head part of the screw 12 is also measured.
These sampling data are performed in time series and are stored in the internal memory 44 via the CPU 40 as a pressure waveform. Next, the statistical calculation is performed, the allowable limit is set, the graphic display of the pressure waveform is performed as shown in FIG. 6, and the comparison calculation of the measured pressure waveform and the normal waveform is executed as shown in FIG. To be done. Next, normality or abnormality is determined. In the case of abnormality, first, it is determined whether or not the time series is stable. Then, the various abnormal waveforms are sequentially compared and the waveform with the highest similarity is selected. In this way, the cause of the abnormality is confirmed. If there is no waveform with high similarity, it is stored. This is a supplementary test of a kind of test result, and is effective as a diagnostic method for a complicated cause phenomenon. In this way, when the abnormality is eliminated and the state returns to normal, the deviation of the melt groove pressure from the target value is obtained, and the temperature adjustment of the adjacent barrel temperature control zone is performed so that this deviation is within the pressure allowable value. 22 and
Correct the barrel set temperature of 23. In order to correct the barrel set temperature, a calculation for updating the barrel set temperature is performed, and the updated temperature signal is selectively output to the temperature controllers 22 and 23 via the output interface 52 and the multiplexer 51. It is considered that such a change in the barrel temperature in the melting step necessarily affects the molten material of the head portion of the screw 12, so the temperature is detected by the temperature sensor 28 of the head portion as in the conventional case, and this head is used. The barrel set temperature of the temperature controller 27 in the barrel temperature control zone near the section is updated.

2 and 3 are flowcharts showing a program example of the extruder shown in FIG. In FIG. 2, step a is an initial setting. Step b is for sampling timing, and when the position signal indicating the position of the barrier flight shown in FIG. 6 exists in the AND gate, sampling is started. Then, in step c, the pressure waveform is sampled. In step d, sampling is terminated when the position signal indicating the position of the barrier flight appears again, and the data obtained in step e is processed. Steps f and g are temperature sampling of the screw head portion and data processing thereof, which are performed as needed. In step h, statistical calculation and comparison calculation are performed on the sampling data of the pressure waveform to determine an abnormal waveform, and when abnormal, it is determined whether the time-series data sampling is stable and sequentially compared with various abnormal waveforms. The most similar waveform is selected, the cause of abnormality is clarified, and repair processing is performed. Step i shows that after confirming that the melting process is normal, the process moves to constant value control of the melt groove pressure after step j. The flowchart of FIG. 3 shows that after the program shown in FIG. 2 is finished, the constant value control of the molten material temperature of the screw head portion after step n is executed.

〔The invention's effect〕

As is apparent from the above-described examples, according to the control method for the extruder and the like according to the present invention, the state of the melting process, which has been difficult to judge by the conventional method, is clarified by the automatic diagnosis control system, and the setting of the melt groove pressure is performed. It can be easily identified in a short time of operation, and it becomes possible to optimally control the barrel set temperature based on this, and further improve the overall performance of the extruder by adding temperature control of the molten material in the screw head. Can be made.

Needless to say, various design changes can be made without departing from the spirit of the present invention.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an extruder for carrying out the control method of the extruder and the like according to the present invention, and FIGS. 2 and 3 are respectively control program examples of the extruder shown in FIG. FIG. 4 (a) and FIG. 4 (b) are enlarged cross-sectional views and longitudinal cross-sectional views of the main part showing the mounting state of the pressure sensor shown in FIG. 1, and FIGS. 5 (a) and 5 (b) are FIG. FIG. 6 is an enlarged side view of a main part showing a mounting state of the position sensor shown in FIG. 4 and a pressure characteristic diagram of the pressure sensor. FIG. 6 is a characteristic curve diagram showing a display example of a pressure waveform sampled by the control method according to the present invention.
FIG. 7 is an explanatory diagram showing a comparative display example of the reference data of the pressure waveform and the measured data, and FIGS. 8 (a), (b) and (c) are model diagrams showing the molten state in the screw groove, respectively. 10 …… Barrel, 11 …… Hopper 12 …… Screw, 14 …… T-die 16 …… Reducer, 18 …… Drive motor 20 …… Heater, 21,22,23,25,27 …… Temperature controller 24 ...... Cooling fan, 26 …… Pressure sensor 28 …… Temperature sensor, 30 …… Position sensor 32,34,42 …… Signal processor 36,51 …… Multiplexer, 38 …… A / D converter 40 …… CPU, 44 ... Internal memory 46 ... CRT display, 48 ... Printer 50 ... Floppy disk 52 ... Output interface, 53 ... Keyboard 54 ... Buzzer, 60 ... Main flight 62 ... Barrier flight

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-53-145874 (JP, A) JP-A-58-92545 (JP, A) JP-B 2-58092 (JP, B2)

Claims (4)

[Claims] 1. A plastic solid material fed into a barrel whose temperature is controlled in a divided manner is extruded and melted by rotation of a screw provided with a main flight and a barrier flight,
In a method for controlling an extruder or the like for extrusion molding, injection molding or blow molding the molten material that has gone through this extrusion melting step,
The pressure waveform consisting of the pressure inside the melt groove and the pressure inside the solid groove in the melting promoting portion of the screw is measured and sampled in relation to the positions of the barrier flight and the main flight respectively, and the melting step is performed by this sampling data. When it is determined to be normal, the deviation from the target value of the melt groove pressure is obtained, and when this deviation exceeds the allowable pressure value, the barrel set temperature of the barrel temperature control zone close to the melting promoting section is controlled. A method for controlling an extruder or the like, characterized in that the pressure in the melt groove is maintained within a certain range. 2. A method for controlling an extruder or the like according to claim 1, wherein pressure signals indicating the pressure in the melt groove and the pressure in the solid groove from a pressure sensor are selectively input through a signal processor. And the sampling data is input to the CPU via the A / D converter, the position signal indicating the position of the barrier flight and the main flight from the position sensor is directly input to the CPU, and the comparison is made by the pressure waveform. When it is judged that the melting process is normal, the operation to update the barrel set temperature is performed so that the deviation of the pressure in the melt groove does not exceed the allowable pressure value, and the updated temperature signal is output to the proximity of the melting promoting unit via the output interface. A method of controlling an extruder or the like, which comprises outputting to a temperature controller in a barrel temperature control zone. 3. A plastic solid material fed into a barrel whose temperature is controlled in a divided manner is extruded and melted by rotation of a screw provided with a main flight and a barrier flight,
In a method for controlling an extruder or the like for extrusion molding, injection molding or blow molding the molten material that has gone through this extrusion melting step,
The pressure waveform consisting of the pressure inside the melt groove and the pressure inside the solid groove in the melting promoting portion of the screw is measured and sampled in relation to the positions of the barrier flight and the main flight respectively, and the melting step is performed by this sampling data. When it is determined to be normal, the deviation from the target value of the melt groove pressure is obtained, and when this deviation exceeds the allowable pressure value, the barrel set temperature of the barrel temperature control zone close to the melting promoting section is controlled. When the pressure in the melt groove is maintained within a certain range, the temperature of the molten material in the head portion of the screw is further measured to obtain the deviation between this temperature and the set temperature, and when this deviation exceeds the temperature allowable value. The temperature of the molten material in the head part is maintained within a certain range by controlling the barrel set temperature in the barrel temperature control zone near the head part. The method of extruder or the like, characterized in Rukoto. 4. A method of controlling an extruder or the like according to claim 3, wherein a pressure signal from the pressure sensor indicating the pressure in the melt groove and the pressure in the solid groove and a head of the screw from a temperature sensor. The temperature signal indicating the temperature of the molten material in the part is selected and input via the signal processor and the sampling data is sent to the CPU via the A / D converter.
The position signal indicating the positions of the barrier flight and the main flight from the position sensor is directly input to the CPU, and the pressure in the melt groove when the melting process is judged to be normal by comparing the pressure waveforms. The calculation of updating the barrel set temperature so that the deviation does not exceed the allowable pressure value, and outputs the updated temperature signal to the temperature controller in the barrel temperature control zone close to the melting promoting section via the output interface,
Further, a calculation for updating the barrel set temperature is performed so that the deviation of the temperature of the molten material in the head portion does not exceed the allowable temperature value, and another update temperature signal is sent to the barrel temperature close to the head portion via the output interface. A method for controlling an extruder or the like, which comprises outputting to another temperature controller in the control zone.