JPS61241124A - Automatic diagnostically controlling system for melting process of material in plastic molding machine - Google Patents

Abstract

PURPOSE:To properly control the melting process of material in a molding machine by a constitution wherein the internal pressure of molten material is detected in the relationship with the position of the flight of a screw so as to automatically diagnose the normality or abnormality from the sampling data obtained. CONSTITUTION:A first pressure sensor 26 to detect the pressure in a barrel 10 and a second pressure sensor 28 to detect the pressure at a screw head part are provided on the barrel 10 of an extruder. In addition, a positional sensor 30 to detect the position of the flight of a screw is provided on the end part 12a of the screw. The signals detected by the first pressure sensor 26 and by the second pressures sensor 28 are selectively supplied to an A/D converter 38 and, after that inputted to a CPU 40. Further, the signal detected by the positional sensor 30 is also inputted through a signal processor 42 to the CPU 40, which is so constituted as to compare said signals with the reference data memorized and stored in advance.

Description

Detailed Description of the Invention [Technical field to which the invention pertains] This invention relates to a plastic molding machine such as an extruder, an injection molding machine, a blow molding machine, etc. that has a melting process of a plastic material, and the melting rate of the material melting process, the solid This invention relates to a control system that automatically diagnoses bed changes, disappearances, melt pools, transport and mixing in the melt zone, etc.

[Prior art and its problems]

In general, plastic molding machines are required to uniformly and stably supply melt polymer to the next process.
Particularly in an extruder, a sufficient amount of melt polymer must be ensured.

In order to satisfy these demands, it is essential that the extrusion screw be appropriately designed, but in order to efficiently extrude a variety of melt polymers using seven general-purpose screws, it is necessary to adjust the operating conditions. Setting, monitoring and controlling is essential.Traditionally, such extrusion screw monitoring and control is essential.

This is done targeting the head resin pressure at the tip of the screw, temperature, screw torque, etc.

On the other hand, when an extruder is roughly divided into a solid transport section, a melting section, and a measuring section, it can be said that most of the performance is determined by the behavior of the melting section. However, in areas far downstream from the head, such as in gou, there is a delay in information such as resin pressure and temperature, and deformation occurs due to rounding or combinations, making it difficult to perform appropriate control and cause analysis. . Attempts have also been made to observe the internal pressure of the screw using an analog recorder, but quantitative analysis has not yet been conducted.

[Problem that the invention seeks to solve]

However, in general, the throughput, stability and uniformity of the material, which define the performance of the extruder, are determined by the conditions of the melting process. Various behavioral analyzes are known during the melting process of plastic materials in such extruders, but since plastic materials are a group of materials that inherently have heterogeneous and unstable characteristics, they are susceptible to disturbance factors. constantly exposed to fluctuating risks.

Possible causes of such changes in the material include (1) changes in the characteristics of the material itself, (2) changes in operating conditions, and (3) changes in the material passage over time. Next, details of the causes of these fluctuations will be explained.

(1) Changes in material properties (average properties and distribution): apparent specific gravity, thermal properties, surface hardness, friction properties.

These are changes in compression characteristics, temperature, moisture absorption, particle shape, molecular weight, crystallinity, blending ratio, etc.

(2) Fluctuations in operating conditions Barrel temperature, screw temperature (cooling), screw rotation speed, feed amount, and biting state.

Changes include filter clogging and backflow of entrained air.

(3) Changes in material passage over time These are changes in surface deposits, wear, etc.

It is assumed that these causes cause variations in the material during the melting process, and in extreme cases, break-up of the solid bed, starvation phenomenon, non-bath melting, or galling may occur. Furthermore, it is thought that the cause is often not a single cause but a combination of multiple causes.

Therefore, an object of the present invention is to measure the behavior of the material melting process in a plastic molding machine by measuring the pressure characteristics in the screw groove based on the positional relationship of 7 lights using a pressure sensor and a position detector, and to determine the measurement waveform xi and the reference waveform. 7i, the pressure distribution waveforms in the screw groove are compared and contrasted, and the deviation degree of both waveforms is calculated as
) and similarity rzy (correlation coefficient), etc., to provide an automatic diagnosis system for appropriately controlling the material melting process of the molding machine.

[Means for solving problems]

The automatic diagnosis control system for the material melting process in a plastic molding machine according to the present invention is a plastic molding machine configured to extrude and melt a plastic material with a screw, and to extrude, injection mold, or blow mold the molten material. A pressure sensor that detects the pressure in the material melting part of the screw and a position sensor that detects the flight position of the screw are provided, and the sampling data obtained from each of these sensors is compared and contrasted with predetermined reference data to determine the correlation. The present invention is characterized in that it includes an arithmetic control unit that calculates sex statistics and determines whether the statistics are normal or abnormal, and performs appropriate control in the event of an abnormality.

In the automatic diagnostic control system, the pressure sensor is configured to sample the pressure of the molten material in the solid groove of the screw and the pressure of the molten material in the melt groove in relation to the position and time of the main flight and the secondary flight. It is suitable if

Further, the pressure sensor can be constructed of a proximity sensor that generates a predetermined output signal corresponding to the position of the main flight and the position of the sub-flight of the screw in a positional relationship with the pressure sensor with respect to the rotation of the screw.

In the automatic diagnostic control system, the sampling data obtained by the pressure sensor and the position sensor is calculated and stored in percentage along with related data such as molten material pressure at the screw head, screw speed, and screw barrel temperature, and is configured to be displayed graphically. be able to.

Furthermore, the correlation between the sampling data and the reference data includes the degree of deviation and similarity of the pressure waveform pattern, and the time-series stability based on the time-series sampling data,
It can be configured to distinguish between normality and abnormality as well as to determine temporal stability during abnormality.

[Embodiments of the invention]

Next, an embodiment of the automatic diagnosis control system for the material melting process in a plastic molding machine according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is an explanatory diagram showing the structure and system configuration of a plastic extruder which is an embodiment of the system of the present invention.

That is, in FIG. 1, reference numeral 10 indicates a screw barrel, and a barrier type screw /2 is inserted and disposed inside this barrel /θ. The head of this screw saw is provided with a T-die puffer as an extrusion mold.

Further, the base of this screw /2 is connected to a drive motor / through a speed reducer /6. on the other hand.

A heater tacho θ is attached to the outer periphery of the barrel/θ, and a hopper 22 for charging material is provided on the base side of the screw 7.2. Note that an external cooling fan 24t is appropriately provided for the heater 〇. The above configuration is the basic configuration of the extruder.

However, in the present invention, the barrel/θ of the extruder
A first pressure sensor 26 for detecting the internal pressure and a second pressure sensor 2tt for detecting the pressure in the screw head are provided, and the position of the screw flight with respect to the screw end 2a is provided. A position sensor 3θ is provided to detect the position. The signals detected by the first pressure sensor 26 and the first pressure sensor 21r are selectively supplied to the A/D converter 3 by the multiplexer 36 via signal processors 32 and 317, respectively, and input to the CPU group θ. do. In addition, the signal detected by the position sensor 3θ is also
The signal is input to the CPU 9θ via the signal processor Dako. In this way, the pressure data and position data input to the CPU 4/θ are stored in the internal memory 4t4t and compared with reference data stored and held in advance. Note that CPUVθ includes output devices such as CRT display 4T6 and printer game, and floppy disk Sθ.
External memories such as the following are connected as appropriate. Further, a buzzer s<t for issuing an abnormality alarm is connected to the CPU θ via the output interface 52.

By the way, the detailed arrangement of the first pressure sensor 26 and the screw/2 for performing bath melt extrusion processing of the material is as shown in FIGS. 2 and 3. In addition, in FIG. 1 and FIG. 3, reference numeral S6 is a screw/- solid groove, 5g is also a melt groove, and 60 is a screw 7.
．． The main flight % of 2 and 6 also indicate the secondary flights. Incidentally, the No. 1 pressure sensor 21r is also attached to the screw barrel /θ in the same manner as described in ^1. On the other hand, 5 position sensor 3
As shown in Fig. 9, θ is provided opposite the signal generating collar 64t attached to the screw end/2m, and generates a flight position signal as shown in Fig. S according to its rotational deviation. Configure it to occur. Therefore, as a position sensor 3θ.

For example, a proximity switch can be suitably used.

Next, the operation of the automatic diagnosis control system of the present invention having the above configuration will be explained.

Since changes and abnormalities in the material melting process, that is, in the material melting section of the extruder, appear as internal pressure waveforms in the barrel, the CPU 4tθ performs the following arithmetic processing.

1. Sampling of internal pressure waveform The internal pressure waveform is sampled using a pressure sensor and a position sensor. In this case, it is preferable to sample the reference waveform, pressure at the screw head, screw speed, barrel temperature, etc.

(1) Sampling positions should be limited to the melted area or at multiple locations.

(2) Input the flight position data at the same time to clarify the positional relationship within the screw groove.

(3) Perform time-series sampling as necessary.

2) Storage of internal pressure waveform The data of the internal pressure waveform obtained by the sampling is stored in the internal memory 1Lt& via the CPU IIa.

In this case, related data is also stored. The storage operation is configured so that it can be executed at any time by keyboard operation via an appropriate input interface to the CPUQθ.

3. Setting of permissible limit (11rfng (Degree of deviation between measurement waveform Xi and reference waveform yi) However, the screw groove is expanded in the circumferential direction, and it is spread at a distance ti from the reference position (i = /... ... n).

(21rxy (?111 constant waveform X, and reference waveform 7iO
Similarity: Correlation coefficient) However, n σX7”, Σ(Xi-1) (Ni-7) ・・・・・・
(4) n 1 = 1 The necessary and sufficient condition for all five waveforms to match is % rms
=Q. In this case, necessarily r! , = /, θ. However, rxy''/, θ is only a necessary condition for both waveforms to completely match.

4. Graphic display of internal pressure waveform Based on the sampling data, the internal pressure waveform is graphically displayed on, for example, a CRT display (see FIG. 6).

5. Diagnosis by comparison and analysis of internal pressure waveforms (1) Compare the measured waveform with a normal waveform to identify normal or abnormal (see Figure 1).

(2) In the case of an abnormality, first determine whether it is stable over time.

(3) Next, sequentially compare various abnormal waveforms and select the waveform t with the highest similarity.

(4) If there is no highly similar pattern, record it as is.

6. Diagnostic processing (1) Alarm Message output (display, record), buzzer, etc.

(2) Control First aid for slowing down, etc. , and other stabilization controls.

A flowchart of a program for performing the above arithmetic processing is shown in FIG.

〔Effect of the invention〕

As is clear from the embodiments described above, according to the present invention,
A plastic molding machine having a screw that includes a melting process is configured to detect the internal pressure of the molten material in relation to the 7-light position of the screw, and a reference waveform that is stored in advance and stores an internal pressure waveform based on the sampling data obtained as a result. In comparison, t″L degree rm+s and similarity r
By calculating statistical quantities such as zy, it is possible to automatically diagnose whether the system is normal or abnormal, thereby easily and reliably achieving alarm generation and switching to appropriate control.

Therefore, according to the present invention, it is possible to diagnose and predict abnormal phenomena in the material melting process.

Based on this, the alarm is generated and the control is reliably shifted to appropriate control, and for example, it is possible to improve the productivity and stability of plastic films and sheets molded by an extruder, as well as to achieve high precision.

Although the preferred embodiments of the present invention have been described above, it goes without saying that various design changes can be made without departing from the spirit of the present invention.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the main parts of an extruder and the system configuration as an example of the automatic diagnosis control system for the material melting process in a plastic molding machine according to the present invention, and FIG.
Fig. 3 is an enlarged cross-sectional view of the main part showing the mounting state of the pressure sensor shown in Fig. 2, Fig. 3 is an enlarged longitudinal sectional view of the main part showing the mounting state of the pressure sensor shown in Fig. 2, and Fig. 4 is shown in Fig. 1. FIG. 5 is an enlarged side view of the main part showing the mounting state of the position sensor, FIG. 5 is an output characteristic curve of the pressure sensor shown in FIG. 2, and FIG. 6 is a characteristic curve showing a display example of the internal pressure waveform sampled by the system of the present invention. FIG. 1 is an explanatory diagram showing an example of comparative display of reference data and measured data of internal pressure waveforms, and FIG. 1 is a flowchart showing an example of a program of the system of the present invention. /θ...Screw barrel /2...Screw/G...T die /6...Reducer/to...
Drive motor θ... Heater, 2 °/° hoppers, 2 cooling fans, 16... 1st pressure sensor 21r... 1st pressure sensor 3θ...
Position sensor 3 pieces, 3 pieces...Signal processor 36...
・Multiplexer 31r...A/D converter θ...
・CPU 4t, 2...Signal processor 1l
llt... Internal memory G6... CRT display qsu... Printer 5θ... Floppy disk j2... Output interface S4I
... Buzzer j6 ... Solid groove sr ... Melt groove 6θ ... Main flight 62 ... Cutting flight 64t ... Signal generation collar

Claims (5)

[Claims] (1) In a plastic molding machine configured to extrude and melt a plastic material with a screw and extrusion mold, injection mold or blow mold the molten material, a pressure sensor detects the pressure in the material melting part of the screw; A position sensor that detects the flight position of the screw is provided, and the sampling data obtained from each sensor is compared and contrasted with predetermined reference data to calculate the correlation statistics and determine whether it is normal or abnormal. An automatic diagnosis control system for a material melting process in a plastic molding machine, characterized by comprising a calculation control section that performs proper control in the event of an abnormality. (2) In the automatic diagnostic control system according to claim 1, the pressure sensor measures the pressure of the molten material in the solid groove of the screw and the pressure of the molten material in the melt groove, and the position of the main flight and the sub-flight as well as the pressure of the molten material in the melt groove. An automatic diagnostic control system for a material melting process in a plastic molding machine configured to sample in relation to time. (3) In the automatic diagnosis control system as set forth in claim 1, the pressure sensor has a predetermined position corresponding to the position of the main flight and the position of the sub-flight of the screw in a positional relationship with the pressure sensor with respect to the rotation of the screw. An automatic diagnostic control system for the material melting process in a plastic molding machine, which consists of a proximity sensor that generates an output signal. (4) In the automatic diagnosis control system according to any one of claims 1 to 3, the sampling data obtained by the pressure sensor and the position sensor is used to determine the molten material pressure at the screw head, the screw speed, An automatic diagnosis control system for the material melting process in a plastic molding machine, which is configured to calculate, store, and graphically display related data such as screw barrel temperature. (5) In the automatic diagnostic control system according to any one of claims 1 to 4, the correlation between the sampling data and the reference data is based on the degree of deviation and similarity of pressure waveform patterns and the time series. An automatic diagnosis control system for a material melting process in a plastic molding machine, which includes time-series stability based on sampling data, and is configured to identify normality or abnormality as well as determine time-series stability during abnormality.