JPS6331730A - Control of extruder or the like - Google Patents

Abstract

PURPOSE:To permit the optimal control of a barrel setting temperature, by providing an automatic diagnosis control system with respect to a pressure in a melt promoting unit. CONSTITUTION:An extruder extrudes and melts the solid material of plastic, supplied into a barrel 10, whose temperature is controlled dividedly, by a screw 12 equipped with a main flight 60 and a barrier flight 62, there after, molds by extrusion through a T die 24, for example. Pressure waveforms, formed by a pressure in a melt groove 58 and a pressure in a solid groove 56 in the melt promoting unit of the screw 12, are measured by a pressure sensor 26 in a relation with respect to respective positions of the barrier flight 62 and the main flight 60 and, further, samplings are effected. When a melting process is judged as normal from the data of the sampling, a difference between the pressure in the melt groove 58 and an objective value is obtained. When the difference has exceeded a pressure allowable value, the barrel setting temperature of the temperature regulating meters 22, 23 of a barrel temperature control belt near the melt promoting unit is controlled whereby the pressure in the melt groove 62 is maintained within a given range.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for controlling an extrusion molding machine, an injection molding machine, and a blow molding machine (hereinafter collectively referred to as extruders, etc.) that mold molten plastic material. In order to achieve especially high-quality molding, the screw that extrudes and melts the material is equipped with a main flight and a barrier flight (sub-flight).
The present invention relates to a method of controlling an extruder, etc. that uses a barrier-type screw that has a solid groove and a melt groove formed between it and the inner surface of a barrel.

[Conventional technology]

The goal of controlling an extruder, etc. is to use an appropriately designed extrusion screw, set the barrel temperature appropriately, and uniformly and stably supply a predetermined extrusion amount of molten material to the next process. . For this reason, in the early stages, constant value control of the pressure and temperature of the molten material in the screw head was performed.

However, it has been found that this control alone has its limits and sometimes has the opposite effect of promoting melting instability. In other words, this is due to the phenomenon of solid bed breakup, which generally means the breaking up of solid unmelted material, as the solid material passes through the feeding section, compression section, and metering section in the groove of the screw. This shows an unstable state of melting that occurs during the melting process where the material gradually changes to molten material. In order to avoid such a phenomenon, a barrier-type screw has a new barrier flight installed in the melting promotion section, which occupies the longest part of the screw, as a shelf to separate the solid component and the molten component. The improvement effect of this new barrier-type screw was noteworthy, but what expanded this effect even further was the following diagnostic control system.

That is, the present applicant previously solved the problem of other instability, including break-up of the solid bed, by using signals from a pressure sensor provided in the melting promotion section and a position sensor provided at the drive end of the screw. Automatic diagnosis of the melting process that detects the waveform, compares and contrasts it with predetermined standard data, calculates the correlation statistics, determines whether it is normal or abnormal, and performs additional tests in the event of an abnormality. He proposed a control system and filed a patent application as Japanese Patent Application No. 81369/1983.

[Problem that the invention seeks to solve]

However, in the automatic diagnostic control system,
There is no clear control over the barrel temperature setting, which is important for determining abnormalities. Conventionally, the value of the melt groove internal pressure could not be determined uniquely, and varied depending on the structure of the screw, the characteristics of the material, the rotational speed of the screw, etc., and could not be considered as a guideline for control. However, the diagnosis result of the automatic diagnosis control system has since become clear that once the above-mentioned parameters are selected, the pressure within the melt groove is almost constant during the normal melting process. Further, according to the above diagnosis results, a model diagram showing the molten state in the screw groove shown in FIG. 8 can be considered. In FIGS. 8(a), (bl 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,
58 indicates melt grooves, respectively.

Fig. 8 [a] shows a state of insufficient melting, where the melt components are not filling the melt groove 58, and it is felt that it is necessary to raise the barrel temperature setting, but it is difficult to increase the pressure inside the melt groove unnecessarily in order to increase the extrusion amount. If this operation is performed, an excessive melting state as shown in FIG. 8(C) will occur, and breakup of the solid bed will occur, resulting in 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 pressure in the melt groove, the better the result. This is the facultative molten state shown in FIG. 8(b). It has also become clear that this small range in which it is difficult to judge is a state in which the pressure waveform of the automatic diagnostic control system is judged to be normal.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to confirm that the barrel temperature in the melting process of an extruder having a barrier type screw is normal by using the automatic diagnostic control system, and then to control the temperature in the melt groove. It is an object of the present invention to provide a control method for an extruder, etc., which can clarify a target value of pressure and optimize this target value as a reference pressure.

[Means for solving problems]

Therefore, the method for controlling an extruder, etc. according to the present invention involves extruding and melting a plastic solid material supplied into a barrel whose temperature is controlled in parts by rotating a screw equipped 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 a molten material that has undergone a melting process, a pressure waveform consisting of a melt groove internal pressure and a solid groove internal pressure in the melting promotion section of the screw is controlled by the barrier flight and the solid groove pressure. Measurement and sampling are performed in relation to the position of each main flight, 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 determined, and this deviation is the pressure tolerance value. If the temperature exceeds the melting point, the barrel temperature control zone in the vicinity of the melt promoting section is controlled to maintain the pressure within the melt groove within a certain range.

Further, in the method for controlling the extruder, etc., pressure signals indicating the melt groove internal pressure and the solid groove internal pressure from the pressure sensor are selectively inputted via a signal processor and sampled via an A/D converter. The data is input to the CPU, position signals indicating the positions of the barrier flight and the main flight from the position sensor are directly input to the CPU, and when it is determined that the melting process is normal by comparing the pressure waveforms, the melt Calculations are performed to update the barrel temperature so that the deviation in the groove pressure does not exceed the pressure tolerance, and the updated temperature signal is output via the output interface to the temperature controller in the barrel temperature control zone near the melting promotion section. Configure it to do so.

In addition, in the method for controlling the extruder, etc., the temperature of the molten material in the screw head section is further measured to determine the deviation between this temperature and the set temperature, and if this deviation exceeds the temperature tolerance, the head section is Preferably, the temperature of the molten material in the head section is maintained within a certain range by controlling the barrel temperature in a barrel temperature control zone adjacent to the barrel temperature control zone.

[Effect]

According to the method for controlling an extruder or the like according to the present invention, if any abnormality occurs in the melting process of the extruder or the like that is normally operating, the pressure waveform based on the sampling data from each sensor will be abnormal. The automatic diagnosis control system detects the abnormality and takes emergency measures such as g91 output and slowdown. During the recovery process, if the pressure waveform returns to normal, the pressure inside the melt groove and the temperature of the molten material at the screw head are both determined to be deviations from the target values, and this deviation is maintained within the permissible pressure and temperature ranges. In this way, the barrel temperature control zones in the barrel temperature control zones that are close to the melting promotion section and the head section of the screw are controlled to optimal values. In this way, it is possible to ascertain the setting of the pressure in the melt groove, which has been difficult to judge in the past, in a short period of operation, and to perform control using this as a guide or guide, thereby improving the overall performance of the extruder to its maximum.

〔Example〕

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

FIG. 1 is a schematic diagram showing an embodiment of an extruder for implementing the method for controlling an extruder, etc. according to the present invention. In FIG. 1, reference numeral 10 indicates a barrel, and a screw 12 is inserted and disposed inside this barrel 1o. This screw 1
The head portion of No. 2 is provided with a T-die 14 as an extrusion mold. Further, the base of this screw 12 is connected to the reducer 1
6 to a drive motor 18.

Further, a heater 20 for heating is provided on the outer periphery of the barrel 10.
is installed, and temperature sensors are appropriately installed near it, and these are connected to temperature controllers 21, 22, 23, 25 and 2.
7 and are controlled separately. This heater 2o
A fan 24 for external cooling is appropriately provided for the screw 12, and a hopper 11 for supplying solid plastic material is provided on the base side of the screw 12. The screw 12 is provided with a main flight 60 and a barrier flight 62, and the place where these two types of flights are provided is the melting promotion part of the screw 12,
A pressure sensor 26 for detecting the pressure in the melt IJ 58 and the solid groove 56 shown in FIG. 8 is provided in the barrel 10 corresponding to this portion. Furthermore, screw 1
A temperature sensor 28 for detecting the temperature of the molten material is provided in the barrel 1o corresponding to the head portion of No. 2. Furthermore, a position sensor 3o is provided at the base end 12a of the screw 12 to detect the positions of the main flight 60 and the barrier flight 62. The signals detected by the pressure sensor 26 and the temperature sensor 28 are selectively sent to an A/D converter 38 by a multiplexer 36 via signal processors 32 and 34, respectively.
The data is supplied to the CPU 40 as sampling data. - On the other hand, the signal from the position sensor 30 is input directly to the CPU 40 via the signal processor 42. These various input data are stored in the internal memory 44. Eventually, these pressure waveforms and temperatures are compared with reference pressure data and target temperature stored in advance. The CPU 40 is appropriately connected to output devices such as a CRT display 46 and a printer 48, an input setting device including a keyboard 53, and an external memory such as a floppy disk 50. Also, C
For the PU 40, there is a buzzer 54 that issues an abnormality alarm via an output interface 52, and a multiplexer 51.
Temperature controllers 21, 22, 23, 25 and 27 are selectively connected via.

Next, the detailed relationship between the pressure sensor 26 and the screw 12 is shown in FIG. 4 (al and (bl). In FIG.
2 rotates, the pressure sensor 26 detects the pressure in the groove of the melt groove 58 from the barrier flight 62 to the main flight 60, and as it rotates further, the pressure sensor 26 detects the pressure in the groove of the solid i56 from the main flight 60 to the barrier flight 62.

In addition, the position sensor 30, as shown in FIG. 5 (al),
It is provided opposite to a signal generating collar 64 attached to the screw end 12a, and generates a flight position signal as shown in FIG. 5(b) in accordance with its rotational deviation. Therefore, as the position sensor 30, for example, a proximity switch can be suitably used.

Next, a method for controlling the extruder configured as described above will be explained based on its operation.

First, the barrel temperature is raised to a predetermined set temperature, the rotational speed of the screw 12 is maintained at a predetermined rotational speed, and the plastic solid material is supplied.

If there is no abnormality in the melting process, the pressure sensor 26 measures the internal pressure of the melt groove and the internal pressure of the solid groove in relation to the barrier flight position and the main flight position, and performs sampling. Furthermore, the temperature of the molten material at the head portion of the screw 12 is also measured by the temperature sensor 28 . These sampling data are processed in time series and are processed as pressure waveforms by the CPU.
40 and stored in internal memory 44.

Next, statistical calculations are performed to set acceptable limits, a graphical display of the pressure waveform is performed as shown in Figure 6, and a comparison calculation between the measured pressure waveform and the normal waveform is performed as shown in Figure 7. be done. Next, it is determined whether it is normal or abnormal.

In the case of an abnormality, first it is determined whether it is stable over time. Next, it sequentially compares with various abnormal waveforms and selects the waveform with the highest similarity. In this way, the cause of the abnormality can be confirmed. If there is no highly similar waveform, it is memorized.

This is a kind of follow-up test for test results, and is effective as a diagnostic method for phenomena with complex causes. In this way, once the abnormality has been resolved and the state has returned to normal, the deviation of the pressure in the melt groove from the target value is determined, and the temperature of the adjacent barrel temperature control zone is adjusted so that this deviation is within the pressure tolerance. Total 22
And 23, the barrel temperature setting is corrected. In order to correct this barrel set temperature, a calculation is performed to update this barrel set temperature, and an updated temperature signal is output to interface 5.
2 and multiplexer 51, it is selectively output to temperature controllers 22 and 23. It is considered that such a change in barrel temperature during the melting process will definitely affect the melted material in the head portion of the screw 12, so the temperature is detected by the temperature sensor 28 in the head portion as in the past.
The barrel temperature setting of the temperature controller 27 in the barrel temperature control zone near the 7th and 7th points is updated.

2 and 3 are flowcharts showing example programs for the extruder shown in FIG. 1. In FIG. 2, step a is initial setting. Step b is to determine the timing of sampling, and starts sampling when a position signal indicating the position of the barrier flight shown in FIG. 6 is present in the AND gate. Then, in step C, the pressure waveform is sampled. In step d, sampling is terminated when a 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 and data processing performed as necessary. Step h performs statistical calculations and comparison calculations on the sampling data of the pressure waveform, determines abnormal waveforms, determines whether the time series data sampling is stable in the case of abnormality, and sequentially compares with various abnormal waveforms. The most similar waveform is selected, the cause of the abnormality is determined, and repair processing is performed. Step i indicates that after confirming that the melting process is normal, the process moves to constant value control of the pressure in the melt groove from step j onward. The flowchart in FIG. 3 shows that after the program shown in FIG. 2 is completed, constant value control of the temperature of the molten material in the screw head portion after step n is executed.

〔Effect of the invention〕

As is clear from the above embodiments, according to the method for controlling an extruder, etc. according to the present invention, the state of the melting process, which was difficult to judge in the past, can be clarified by the automatic diagnostic control system, and the setting of the pressure inside the melt groove can be made clear. This can be easily determined in a short period of operation, and the barrel temperature setting can be optimally controlled based on this. Furthermore, by adding temperature control to the molten material in the screw head, the overall performance of the extruder can be maximized. can be done.

It goes without saying that various design changes can be made without departing from the spirit of the invention.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an extruder that implements the method for controlling an extruder, etc. according to the present invention, and FIGS. 2 and 3 show an example of a control program for the extruder shown in FIG. 1. The flowchart shown in FIG. 4(a), (bl is an enlarged cross-sectional view and vertical cross-sectional view of the main part showing the installation state of the pressure sensor shown in FIG. 1, and FIG. 5(al), (BL is the same as in FIG. FIG. 6 is an enlarged side view of the main parts showing the installation state of the position sensor and an output characteristic line 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. are explanatory diagrams showing comparative display examples of pressure waveform reference data and measured data;
C1 is a model diagram showing the molten state inside the screw groove. 10, Barrel 11. ,,Hopper 12),
, screw 14. ,, Tgui16, ,
, 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 Patent Applicant Toshiba Machine Co., Ltd. FIG, '3(a'> FIG, 5(b) B digit FIG, 6 FIG, 7 PQ5.04SensorIIl) L No C0ell-c
I! n1IJICOIrllll(ILlutlFIG,
8

Claims (4)

[Claims] (1) A solid plastic material supplied into a barrel whose temperature is controlled in parts is extruded and melted by the rotation of a screw equipped with a main flight and a barrier flight, and the molten material that has gone through this extrusion melting process is extruded and injection molded. In a method for controlling an extruder or the like for molding or blow molding, a pressure waveform consisting of a melt groove internal pressure and a solid groove internal pressure in the melting promotion part of the screw is measured in relation to the respective positions of the barrier flight and the main flight. Then, sampling is performed, and when the melting process is determined to be normal based on the sampling data, the deviation of the pressure in the melt groove from the target value is determined, and if this deviation exceeds the pressure tolerance, the melting process is determined to be normal. A method for controlling an extruder, etc., comprising controlling a barrel temperature in a barrel temperature control zone to maintain the pressure within the melt groove within a certain range. (2) In the method for controlling an extruder or the like according to claim 1, pressure signals indicating the pressure in the melt groove and the pressure in the solid groove from the pressure sensor are selectively inputted via a signal processor, and Sampling data is input to the CPU via an A/D converter, position signals indicating the positions of the barrier flight and the main flight from the position sensor are directly input to the CPU, and the melting process is determined by comparing the pressure waveforms. When it is determined that the melt groove is normal, a calculation is performed to update the barrel set temperature so that the deviation of the pressure in the melt groove does not exceed the pressure tolerance value, and an updated temperature signal is output to the barrel adjacent to the melting promotion section through an output interface. A method of controlling an extruder, etc., which consists of outputting to a temperature controller in a temperature control zone. (3) The solid plastic material supplied into a barrel whose temperature is controlled in parts is extruded and melted by the rotation of a screw equipped with a main flight and a barrier flight, and the molten material that has gone through this extrusion melting process is extruded and injection molded. In a method for controlling an extruder or the like for molding or blow molding, a pressure waveform consisting of a melt groove internal pressure and a solid groove internal pressure in the melting promotion part of the screw is measured in relation to the respective positions of the barrier flight and the main flight. Then, sampling is performed, and when the melting process is determined to be normal based on the sampling data, the deviation of the pressure in the melt groove from the target value is determined, and if this deviation exceeds the pressure tolerance, the melting process is determined to be normal. The barrel temperature in the barrel temperature control zone is controlled to maintain the pressure within the melt groove within a certain range, and the temperature of the molten material at the head of the screw is measured to determine the deviation between this temperature and the set temperature. is determined, and if this deviation exceeds a temperature tolerance value, the barrel temperature control zone in the barrel temperature control zone adjacent to the head section is controlled to maintain the temperature of the molten material in the head section within a certain range. Characteristic control method for extruder, etc. (4) In the method for controlling an extruder or the like according to claim 3, a pressure signal indicating the pressure in the melt groove and the pressure in the solid groove from a pressure sensor and a pressure signal indicating the pressure in the head portion of the screw from a temperature sensor are provided. Temperature signals indicating the temperature of the molten material are input selectively through a signal processor and sampled data are sent to the CPU via an A/D converter.
A position signal indicating the positions of the barrier flight and the main flight from the position sensor is directly input to the CPU, and when it is determined that the melting process is normal by comparing the pressure waveforms, the pressure in the melt groove is Calculations are performed to update the barrel set temperature so that the deviation does not exceed the allowable pressure value.
Outputting an updated temperature signal to a temperature controller in a barrel temperature control zone adjacent to the melting promotion section via an output interface, and further setting the barrel so that the temperature deviation of the melted material in the head section does not exceed a temperature tolerance value. A method for controlling an extruder, etc., comprising performing a calculation to update the temperature, and outputting another updated temperature signal to another temperature controller in a barrel temperature control zone close to the head section via the output interface.