JPH0453694B2 - - Google Patents

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.) for molding molten plastic materials. In order to achieve especially high-quality molding, a main flight and a barrier flight (sub-flight) are provided on the screw that extrudes and melts the material, and a barrier is created in which a solid groove and a melt groove are formed between the barrel inner surface and the barrel. This invention relates to a precision control method for an extruder using a shaped screw.

[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 amount of molten material to the next process. . For this reason, in the early stages, the pressure and temperature of the molten material in the screw head were controlled at fixed values. 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 disintegration of solid unmelted material, but the solid material passes through the feeding section, compression section, and metering section in the groove of the screw, and gradually becomes molten material. This indicates an unstable state of melting that occurs during the melting process as the temperature changes. In order to avoid such a phenomenon, barrier-type screws have 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 and molten components. The improvement effect of this new barrier-type screw was worth seeing, but
The following diagnostic control system further expands this effect.

That is, the present applicant has previously discovered that the solid bed can be prevented from breaking up and other instability 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. Automated melting process that detects the pressure 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. We proposed a diagnostic control system and filed a patent application as Japanese Patent Application No. 81369/1983. Further, the concurrently filed "Control method for an extruder, etc." provides a barrel temperature control zone near the melting promotion section based on the pressure in the melt groove after the melting process is determined to be normal in the automatic diagnostic control system. The main objective is to control the barrel temperature setting and to control the melt groove internal pressure to a constant value.

[Problem that the invention seeks to solve]

However, conventional control methods for extruders, etc.
If the melting process is normal, the barrel setting is closely related to the melting heat amount of the melting promotion section, that is, the melting speed indicating the speed of movement from the solid material to the molten material, based on the pressure in the melt groove of the melting promotion section. The pressure inside the melt groove changes not only due to the melting speed, but also due to the change in the pressure in the head section caused by clogging of the filter installed in front of the head section of the screw. It also changes due to the influence of molten material pressure. Therefore, if an attempt is made to correct the barrel temperature setting by detecting only the melt groove internal pressure, very good results may not be obtained. For example, even though the pressure in the melt groove has increased due to a clogged filter, it is inappropriate to take corrective action to lower the barrel temperature setting because the melting heating amount is excessive, assuming that the melting rate has increased. It is an action. FIG. 3 is a qualitative characteristic curve diagram of the screw, showing the relationship between the barrel setting temperature, the melting rate, and the screw rotation speed Ns.
In FIG. 3, when the screw speed Ns increases at a constant barrel set temperature, the melting rate increases, but gradually becomes saturated and becomes constant above a predetermined barrel set temperature. Further, FIG. 4 is an explanatory diagram of state changes and corrective operations due to filter clogging and changes in melting rate. In FIG. 4, in the event category, "single" indicates that filter clogging and a change in melting rate occur independently, and "combined" indicates that both occur simultaneously. In the item of state change, reference symbol P ₁ indicates the pressure in the melt groove, P ₂ indicates the molten material pressure in front of the filter, and P ₃ indicates the molten material pressure behind the filter. The arrow indicates increase, decrease, rise, or fall depending on its slope. An asterisk indicates an indeterminate state. Also, Figure 4 shows
This shows one example, and although the temperature of the molten material in the head section is actually related, this is omitted to avoid complexity. In the above example, in the single event shown in Figure 4, the increase in melt groove internal pressure P ₁ due to filter clogging is mistakenly assumed to have increased due to the melting speed. This indicates that it is necessary to detect the molten material pressure _P3 .

Therefore, an object of the present invention is to control an extruder having a barrier-type screw not only by constant value control based on the pressure in the melt groove, but also by detecting the pressure in the melt groove and the pressure of the molten material in front and behind the filter. The present invention provides a precision control method for an extruder, etc., which can perform control that correctly responds to filter clogging, and can always stably maintain the extrusion amount within a certain range.

[Means for solving problems]

Therefore, the method for precisely 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 having a main flight and a barrier flight. In this method of controlling an extruder or the like for extrusion molding, injection molding or blow molding a predetermined extrusion amount of molten material that has been extruded and melted, the melt groove internal pressure P ₁ and solids from the first pressure sensor in the melting promotion part of the screw are controlled. A pressure signal indicating the pressure in the groove, and a pressure of the molten material in front of the filter provided in front of the head of the screw from the second pressure sensor.
a pressure signal indicating the molten material pressure P ₂ behind the filter from a third pressure sensor; and _a temperature signal indicating the molten material temperature TR behind the filter from the temperature sensor; The signals that are sequentially selected and input through the respective signal processors are input to the CPU as sampling data through the A/D converter, and the position signals indicating the positions of the barrier flight and the main flight from the position sensor are directly input to the CPU.
The data is input to the CPU, processed, and stored in the memory, and based on these data, the CPU controls the melting process when the deviation D ₃ of the molten material pressure P ₃ from the target pressure increases and the extrusion rate increases. lowering the barrel set temperature corresponding to the part corresponding to the deviation D ₃ , the deviation D ₃ decreases, the deviation D ₂ of the molten material pressure P ₂ from the target pressure increases, and the extrusion amount decreases;
When the filter is found to be clogged, the rotational speed of the screw is increased to correspond to the difference between the deviations D ₂ and D ₃ , and as the deviation D ₃ decreases and the deviation D ₂ also decreases, the pressure inside the melt groove P decreases. If the deviation D ₁ from the target pressure of ₁ also decreases and the melting heat is insufficient due to filter clogging, the barrel set temperature should be adjusted to match the sum of the deviations D ₁ , D ₂ , and D ₃ . The extrusion rate is controlled so that the extrusion rate is always stably maintained within a certain range.

[Effect]

According to the precision control method for 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 diagnostic control system detects the abnormality and takes emergency measures such as outputting an alarm and slowing down the vehicle. In the recovery process, if the pressure waveform returns to normal, constant value control is performed based on the pressure within the melt groove. The pressure waveforms shown here indicate respective amounts of change over time based on sampling data.

Furthermore, not only the melt groove internal pressure P ₁ in the melting promotion part of the screw, but also the molten material pressures P ₂ and P ₃ in front and behind the filter, and the molten material temperature TR behind the filter are measured. Using the sampling data obtained from these measurements, if the extrusion rate increases, it will be determined that only the pressure P ₃ increases, and if the extrusion rate decreases and the filter is clogged, the pressure P ₂ will increase. This corresponds to a case where the pressure _P3 is decreasing even though it is increasing.If the extrusion rate decreases and no filter clogging is observed, it corresponds to a case where both pressures _P1 and _P3 are decreasing. (See Figure 4). Therefore, if the precision control method for an extruder, etc. according to the present invention is implemented based on the elucidation of such phenomena, control will be implemented that correctly responds to filter clogging, and the extrusion amount will always be stabilized within a certain range. and can be maintained.

〔Example〕

Next, examples of the method for precisely 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 configuration diagram showing an embodiment of an extruder for carrying out the precision control method for an extruder, etc. according to the present invention. In FIG. 1, reference numeral 10 indicates a barrel, into which a screw 12 is inserted and disposed. A T-die 14 serving as an extrusion mold is provided at the head portion of the screw 12. Further, the base of this screw 12 is connected to the reducer 1
6 to a drive motor 18. Also,
A heater 20 for heating is provided on the outer periphery of the barrel 10.
is mounted, and temperature sensors are appropriately installed near it, and these are temperature controllers 21, 22, 23,
The barrel temperature control zone is divided and controlled by 25 and 27. A fan 24 for external cooling is appropriately provided for the heater 20, 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 portion of the screw 12 that has these two types of flights is
, the barrel 10 corresponding to this part
A first pressure sensor 26 for detecting the pressure in the melt groove and the pressure in the solid groove is provided,
Furthermore, in order to detect the pressure of the molten material in front and behind the filter 13 provided in front of the head portion of the screw 12, a barrel 10 corresponding to this member is used.
A second pressure sensor 29 and a third pressure sensor 31 are provided at the barrel 1, and a temperature sensor 28 for detecting the temperature of the molten material behind the filter 13 is provided at the barrel 1.
Set to 0. Further, a position sensor 30 for detecting 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. First, second and third pressure sensors 26, 29 and 31, and temperature sensor 28
The detected signals are processed by signal processors 32 and 32, respectively.
Multiplexer 3 via 34, 35 and 37
6 selectively supplied to the A/D converter 38,
This becomes sampling data and is input to the 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 various input data are stored in internal memory 44. Eventually, these input data are compared with previously stored target values or reference pressure waveform data. CRT display 46 for CPU 40
An output device such as a printer 48, an input setting device such as a keyboard 53, and an external memory such as a floppy disk 50 are connected as appropriate. Also, CPU4
A buzzer 54 that issues an abnormality alarm via an output interface 52 when the
7 is connected.

Next, a method for precisely 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 fed. Next, the sampling data is sent to the CPU 40 by various sensors.
is stored in the memory 44 via the CPU 40
If it is determined that there is no abnormality in the melting process and no filter clogging, the extrusion rate will be maintained within a certain range. It goes without saying that the automatic diagnostic control system described above is used to determine abnormalities in the melting process. The operation of this system will be omitted. Measures against filter clogging will be explained with reference to the flowchart shown in FIG. Figure 2 is the first
1 is a flowchart showing an example of a program for the extruder shown in the figure. Step a is initialization, step b is a determination as to whether or not to start interrupting the measurement process, and step c is a process of switching connections with the first, second and third pressure sensors and temperature sensor using the multiplexer 36. Step d is the timing to start inputting pressures P ₁ , P ₂ and P ₃ and temperature TR from each sensor, step e is sampling data input processing, step f is timing to end data input from each sensor, and step g is This is to check the presence or absence of the measurement point, and in this way, the measurement,
Sampling is now complete. These sampling data are processed in step h,
Then, it is displayed graphically on the CRT display 46. In step i, a change in the extrusion rate is determined, that is, when an increase in the extrusion rate is determined based on an increase in the deviation _D3 between the pressure _P3 and the target pressure, the process moves to step m, and the melting promotion section is Decrease the corresponding barrel set point temperature commensurate with the deviation D ₃ . In FIG. 1, CPU 40 drives multiplexer 51 to output a correction signal to temperature controllers 21 and 22 via output interface 52 that reduces the barrel set point temperature by the deviation D ₃ . In addition, in FIG. 2, when it is determined that the extrusion amount has decreased due to a decrease in the deviation D ₃ , the process moves to step j, and the deviation D ₂ of the pressure P ₂ from the target pressure is determined.
If it is determined that the filter is clogged due to the increase in , the process moves to step n, and the screw rotational speed Ns is increased to correspond to the difference between the deviations D ₂ and D ₃ . In Figure 1, CPU 40 is output interface 5
2, a correction signal is sent to the drive motor 18 to increase the rotational speed Ns of the screw so as to correspond to the difference between the deviations _D2 and _D3 . The relationship between the rotational speed Ns of the screw and the melting speed is as shown in FIG. In addition, in Figure 2, it is determined that the extrusion amount has decreased due to the decrease in the deviation D ₃ ,
If it is determined that the filter is not clogged due to a decrease in the deviation _D2 , the process moves to step k, where it is determined whether the amount of melting heat is insufficient. i.e. pressure
If the deviation D ₁ from the target pressure of P ₁ also decreases, it is clear that the amount of melting heat is insufficient, so proceed to step 1, and change the barrel set temperature corresponding to the melting promotion part, for example, by adjusting the deviation D ₁ and D ₂ and D ₃ . In FIG. 1, the CPU 40 drives the multiplexer 51 and outputs a correction signal to the temperature controllers 21 and 22 via the output interface 52 to increase the barrel set temperature in proportion to the sum of the deviations D ₁ , D ₂ , and D ₃ . do. Referring again to FIG. 2, when the deviation D ₃ becomes zero or increases in step k, a message is displayed on the CPU display 46 or a buzzer 54 is sounded to alert the operator that there is an abnormality in the melting process. This is step p. When such correction processing is completed, the process moves to step q and waits for the reaction of the extruder. Although the reaction speed of temperature control is slow,
The amount of extrusion from the extruder will gradually fall within a certain range.

〔Effect of the invention〕

As is clear from the embodiments described above, according to the precision control method for an extruder, etc. according to the present invention, abnormalities in the melting process are judged and processed, and not only constant value control based on the pressure in the melt groove by the first pressure sensor, but also By measuring the pressure of the molten material in front and behind the filter using the second and third pressure sensors, it is possible to perform control that correctly responds to filter clogging and to maintain the extrusion amount stably within a certain range. can.

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

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an extruder for implementing the precision control method for an extruder, etc. according to the present invention;
Figure 2 is a flowchart showing an example of the control program for the extruder shown in Figure 1, Figure 3 is a characteristic curve diagram showing the relationship between barrel set temperature, melting rate, and screw rotation speed Ns, and Figure 4 is a filter diagram. FIG. 3 is an explanatory diagram of state changes and corrective operations due to clogging and changes in melting rate. 10... Barrel, 11... Hotspa, 12... Skrill, 13... Filter, 14... T-die, 1
6... Reduction gear, 18... Drive motor, 20... Heater, 21, 22, 23, 25, 27... Temperature controller, 24... Cooling fan, 26, 29, 31
...Pressure sensor, 28...Temperature sensor, 30...
Position sensor, 32, 34, 35, 37, 42...
Signal processor, 36, 51...Multiplexer, 3
8...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 light.

Claims (1)

[Claims] 1. Plastic solid material supplied in portions into temperature-controlled barrels is extruded and melted by rotation of a screw equipped with a main flight and a barrier flight, and a predetermined extrusion amount of the extruded and melted material is In a method for controlling an extruder or the like for extrusion molding, injection molding or blow molding a molten material, a pressure signal indicating the melt groove internal pressure _P1 and the solid groove internal pressure from a first pressure sensor in the melting promotion part of the screw; Molten material pressure in front of the filter provided in front of the head of the screw from the second pressure sensor
a pressure signal indicating the molten material pressure P ₂ behind the filter from a third pressure sensor; and _a temperature signal indicating the molten material temperature TR behind the filter from the temperature sensor; The signals that are sequentially selected and input through the respective signal processors are input to the CPU as sampling data through the A/D converter, and the position signals indicating the positions of the barrier flight and the main flight from the position sensor are directly input to the CPU.
The data is input to the CPU, processed, and stored in the memory, and based on these data, the CPU controls the melting process when the deviation D ₃ of the molten material pressure P ₃ from the target pressure increases and the extrusion rate increases. lowering the barrel set temperature corresponding to the part corresponding to the deviation D ₃ , the deviation D ₃ decreases, the deviation D ₂ of the molten material pressure P ₂ from the target pressure increases, and the extrusion amount decreases;
When the filter is found to be clogged, the rotational speed of the screw is increased to correspond to the difference between the deviations D ₂ and D ₃ , and as the deviation D ₃ decreases and the deviation D ₂ also decreases, the pressure inside the melt groove P decreases. If the deviation D ₁ from the target pressure of ₁ also decreases, and the melting heat is insufficient due to no filter clogging, the barrel set temperature is increased to match the sum of the deviations D ₁ , D ₂ , and D ₃ . A precision control method for an extruder, etc., characterized in that the extrusion amount is controlled so as to be always stably maintained within a certain range.