JP3466008B2 - Control method of injection molding equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an injection molding apparatus, and more particularly to a method for controlling an injection molding apparatus for molding a molded article having a hollow portion. . 2. Description of the Related Art Conventionally, after a molten resin is injected into a cavity, a predetermined amount of pressurized gas is injected into the molten resin to form a hollow portion inside the resin, and a certain amount of resin is formed. There is known a method and an apparatus for obtaining a molded article having a hollow portion by cooling the interior of the hollow portion to a predetermined pressure state until the surface layer obtains self-supporting property and thereafter releasing the gas in the hollow portion. . As a technique using such a technique, for example, Japanese Patent Publication No. Hei 4-31853 discloses that a gas is continuously supplied into a mold space while a flow of a plastic material is continuously introduced into the mold space. Accordingly, a configuration is disclosed in which plastic and gas are evenly injected into the mold space, and a gas injection groove having a substantially constant diameter is formed in the injection molded product. Further, in Japanese Patent Application Laid-Open No. 4-31853, in such a gas injection technique, a pressure sensor is provided in a gas pressure line from a gas supply source to a mold, and a cylinder controlled by the pressure sensor is used to control the pressure in advance. A configuration for controlling a gas supply source to supply a set high-pressure gas is disclosed, so that an appropriate gas pressure in the cavity is maintained. [0005] Among the above-mentioned gas injection techniques, in particular, in the latter conventional technique, the gas pressure can be maintained at an appropriate value after gas injection. When the gas pressure is abnormal, the abnormality of the molding can be detected. However, in this technology, even if an abnormality is detected, the production of the molded product is continued as it is, and the defective molded product molded at the time of the abnormality is not processed at that time, so the defective product is regarded as a good product They are carried out together. Therefore, in this case, remove the defective molded product in the post-process,
Alternatively, the machine operation must be stopped when an abnormality occurs. In addition, the investigation into the cause of the gas pressure abnormality and its countermeasures require manual intervention,
There is also a problem that it takes time and effort. The present invention has been made in view of the above points, and when an abnormality occurs in gas injection, it is possible to automate the investigation of the cause and to cope with the abnormality. It is an object of the present invention to provide a control method of an injection molding apparatus which can automatically sort out an image. [0007] In order to achieve the above object, a method for controlling an injection molding apparatus according to the present invention comprises: a mold for forming a hollow portion inside a molded product; An injection molding machine for injecting a molten resin into the inside thereof, a gas injection device for supplying gas to a portion where a hollow portion is to be formed, and a gas passage to be formed in the mold from the gas injection device. Using an injection molding apparatus equipped with a gas pressure detecting means for detecting the pressure of the injected gas installed in the apparatus and a selecting means for selecting a defective molded product, an output from the gas pressure detecting means, An abnormal pattern of the gas pressure change indicated corresponding to each cause of the abnormality in the gas injection and a normal pattern indicating the normal gas pressure change in the gas injection are stored in the memory in advance, and the output from the gas pressure detecting means is stored. Above normal pattern It is determined whether or not the injection molding machine or the gas injection device is a cause of the abnormality so that the output from the gas pressure detecting means conforms to the normal pattern. It is characterized by controlling according to the above and driving the above-mentioned selecting means so as to sort out a molded article molded at the time of an abnormality as a defective article. When the gas pressure is abnormal, the injection molding machine or the gas injection device is controlled according to the cause of the abnormality, and the gas pressure automatically conforms to the normal pattern. . Further, defective products formed at the time of this abnormality are automatically selected and can be processed separately from non-defective products. Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of an injection molding apparatus suitable for use at that time. In this example, an injection molding apparatus includes a mold 1 capable of forming a hollow portion inside a molded product, and an injection for mounting the mold 1 and injecting a molten resin into the mold 1. A molding machine 2, a gas injection device 3 for supplying gas to a portion where a hollow portion is to be formed, a selection means 9 for selecting a defective molded product, and a gas injection device 3 from the gas injection device 3 to the inside of the mold 1. Gas pressure detecting device 10 for detecting a gas pressure injected into a gas passage formed therebetween and detecting an abnormality of the gas pressure.
And a control unit 11 for controlling the injection molding machine 2, the gas injection device 3, and the sorting means 9 based on the output from the gas pressure detection device 10. First, the gas pressure detecting device 10 comprises a pressure sensor 4, a memory 7, a timer 6, a discriminating unit 5, and an alarm output unit 8. The pressure sensor 4 is installed in at least one place in the gas injection device 3 (4a), in a pipe connecting the gas injection device 3 to the mold 1 (4b), or in the cavity of the mold 1 (4c). Have been. The pressure sensor 4 converts the detected gas pressure into an electric signal. The output signal is an analog voltage signal having an output waveform whose voltage changes in proportion to the gas pressure as shown in FIG. It has become. The pressure sensor 4
Performs continuous and intermittent detection in the operation of the gas injection device 3 from the start of gas injection to gas degassing. A voltage signal output from the pressure sensor 4 is sequentially stored in the memory 7, and a voltage signal indicating an abnormal pattern of gas pressure change indicated for each cause of an abnormality in gas injection. A voltage signal indicating a normal pattern indicating a normal gas pressure change in gas injection is stored in advance. The determination unit 5 compares the voltage signal output from the pressure sensor 4 with a voltage signal indicating a normal pattern and its voltage waveform to determine whether an abnormality has occurred. In this determination, a normal voltage range indicated by the voltage waveform in the normal pattern is set, and it is determined whether or not the voltage signal output from the pressure sensor 4 is within the normal voltage range. Note that a voltage comparator is used as a specific means for performing this determination.
In this voltage comparator, a range of voltages to be compared can be determined by setting an upper limit voltage and a lower limit voltage. The timer 6 has a configuration synchronized with the gas injection device 3 and the injection molding machine 2, whereby
For example, the timing of gas injection such as the start of gas injection, the start of gas holding pressure, and the time of gas degassing, the operation timing of the injection molding machine, and the like are set, and the timing for performing determination is given. Here, for example, when the gas holding pressure start signal is output, the timer 6 starts, and after a predetermined time has elapsed, the above-described determination operation is performed on the gas pressure detecting device 10. The alarm output section 8 outputs alarm information so that when an abnormality occurs, the abnormality can be confirmed visually or audibly. For example, the abnormality is notified by lighting a patrol light or an alarm sound from an alarm speaker. Further, when it is determined that the above determination result is abnormal, the control unit 11 controls the gas injection device 3 and the injection molding machine 2 when it is determined that the abnormality is abnormal. For the gas injection device 3, factors that influence the gas inflow amount, such as gas pressure, gas inflow amount, gas inflow speed, and inflow timing, are controlled. On the other hand, for the injection molding machine 2, factors that influence the weight of the molded article, such as the measured value of the molten resin injected from the injection molding machine and the injection pressure, are controlled. Further, when an abnormality occurs, the control section 11 drives a selection means 9 for selecting a molded article molded at the time of the abnormality as a defective product. As an example of the sorting means 9, for example, as shown in FIG. 6 (a), after molding, automatic removal is performed, and when an abnormality occurs in a state where the molded product is placed on a conveyor, a gas pressure detecting device is used. 61, an NG signal indicating an abnormality is output from the product conveyor 63.
Is input to the controller 62 that drives the. With this NG signal, the controller 62 operates the product conveyor 63 in the reverse direction. As a result, defective products flow in the opposite direction to non-defective products, and only defective products can be sorted out. In addition to the above-described structure, when an abnormality occurs, the sorting means 9 drives the unloader so that the molded product is removed from the mold and placed in a place different from the non-defective product. For example, there is a method of driving an arm robot for repelling a defective molded product placed thereon. The hardware configuration of the gas pressure detecting device 10 and the control unit 11 described above is based on a computer. In the determination, a method performed for each shot,
There is a method of making a determination based on the tendency of the voltage waveform stored in the memory 7 from several shots before to the determination time. Hereinafter, these methods will be described in detail. In the former method, abnormality can be determined by comparing the waveforms of the shots, and further, what kind of symptoms can be predicted. When the gas injection is normal, a voltage waveform as shown in FIG. 4A is obtained.
Depending on the molded article, this voltage waveform may take various shapes, but will have substantially the same shape. Therefore, it is possible to determine the abnormality by storing this shape and comparing the voltage waveforms in each shot. In this determination, FIG.
(B), the voltage waveforms at the time of abnormality shown in FIGS. 4 (c) and 4 (d) are stored as patterns, and each voltage waveform corresponds to the cause of the abnormality. Therefore, the abnormality can be determined and the cause can be determined. As an example of a voltage waveform pattern when an abnormality occurs, FIG. 4C shows a case where a gas injection nozzle or a pipe shown in FIG. 4B is clogged.
In the case where gas leakage occurs during gas injection shown in FIG.
There is a voltage waveform when a gas leak occurs during the gas holding pressure shown in (d), and the voltage waveform is used as a reference pattern for abnormality determination. FIG. 2 is an example of an algorithm in this method. Note that the waveforms A, B, C, and D in the figure are equivalent to the waveforms A, B, C, and D shown in FIG. The determination as to whether or not there is an abnormality in the gas pressure is performed at the time when the gas injection is started and when the gas injection is completed and the gas pressure holding is started. First, when the gas pressure deviates from the normal range at the start of gas injection and the value is low, the voltage waveform of the pattern of the waveform C is shown, and there is a possibility of gas leakage. Control the gas injector.
When the value is high, the voltage waveform of the pattern of the waveform B is shown, the possibility of clogging of the nozzle is high, and the gas injection device is controlled to further increase the gas pressure. This removes this clog. If the gas pressure deviates from the normal range at the time when the gas holding pressure is started, the voltage waveform of the waveform D is shown, and gas leakage may have occurred. Control the gas injector. When the gas is injected upon sensing such an abnormality, the gas is injected while monitoring the voltage waveform so that a normal voltage waveform is obtained. On the other hand, changes in the temperature of the surroundings and cooling water, physical / chemical variations in the material pellets, and the like are conceivable. For some reason, as shown in FIG. At the same time, the gas pressure may decrease. In such a case, appropriate measures can be taken by applying the latter method. That is, by examining what kind of change has occurred in the voltage waveform, it is possible to predict the cause and suppress disturbance to the injection molding machine. FIG. 3 is an example of an algorithm in this method. If there is a change compared to the reference waveform,
It is determined whether or not the recent several shots have the same tendency. If there is no similar tendency for the latest several shots, the following determination is performed as feedback limited to this shot. In addition, the following determination is similarly performed when there is the same tendency. First, if gas is difficult to enter, and if not, an abnormality in the weight is determined. If there is an abnormality in the weight, feedback is performed to the injection molding machine to adjust the weight of the molten resin. Also, when gas is difficult to enter,
If there is no abnormality in the weight, the injection timing of the gas is accelerated. As a result, if the state does not become normal, the injection speed of the resin is increased until the state becomes normal. If the gas is not difficult to enter and there is no abnormality in the weight, the gas injection timing is delayed until the gas becomes normal. As described above, by controlling the injection gas pressure, it is possible to detect the instability of molding, and when an abnormality occurs, apply appropriate feedback to the injection molding machine or gas injection device. Thereby, good quality of the molded article after the shot or the next shot can be secured.
In addition, since a series of these steps are performed automatically, there is no need for mechanical adjustment or the like by an operator, so that labor and time can be saved and efficiency is improved. Hereinafter, a specific example of the control method of the injection molding apparatus will be described with reference to an example of an apparatus actually used. FIG. 6 (a) shows the application of this method.
FIG. 6B is a diagram showing a main configuration used, and FIG.
FIG. 7 is a diagram schematically illustrating a configuration of a gas pressure detection device illustrated in FIG. FIG. 7 is a flowchart showing an algorithm of a control method performed using these devices. Hereinafter, the present method will be described with reference to these drawings. First, the configuration of this device is such that the gas pressure from a gas pressure detecting device 61 and a pressure sensor (not shown) for detecting the pressure of the injected gas are converted into a gas pressure signal. And a simple press kit 60 for outputting to the user.
Here, when the molded article 66 is taken out of the mold, it is placed on the product conveyor 63 and moves to a predetermined place. The direction of the operation of the product conveyor 63 can be reversed by the controller 62. When the controller 62 receives an NG signal indicating that an abnormality has occurred from the gas pressure detecting device 61, the controller 62 controls the direction of the operation of the conveyor to be reversed. Configuration. The gas pressure detecting device 61 includes a power lamp 72, a gas pressure display unit 73 for displaying gas pressure, and a gas pressure setting button 7 for setting a normal gas pressure range.
4. a timer 75 for setting the timing of the determination;
Power switch 76, alarm cancel switch 77,
It is provided with a patrol light 71 for visually confirming the alarm and an alarm speaker 78 for notifying the alarm by sound. The alarm speaker 78 is provided with a volume knob and a timbre changeover switch, and is appropriately set according to use conditions. The display setting unit of the gas pressure in the gas pressure display section 73 is kg / cm ² , and the display setting unit of the timer 75 is 0.1 second. The gas pressure setting button 74 is set to a gas pressure range in which quality can be guaranteed. Hereinafter, a control method using the apparatus having this configuration will be described. First, after turning on a power switch 76 of the gas pressure detecting device 61, an appropriate gas pressure range is set by a gas pressure setting button 74, and a timer 75 is set. Since counting starts from the start, a gas holding time minus 1 second is set. The simple press kit 60 has an injection gas pressure (0
Gas pressure signal (0 to 10 kg / cm ² )
V) is output to the gas pressure detecting device 61. The gas pressure detection device 61 takes in the gas pressure signal and determines whether the gas pressure based on the gas pressure signal is within a preset gas pressure range. Therefore, if it is within the range, the manufacture of the product is continued. However, if it is not within the range, an NG signal is transmitted to the controller 62, and
The patrol light 71 is turned on, the alarm speaker 78 is activated, and an alarm is issued. The controller 62 that has received the NG signal reverses the direction of the product conveyor 63 from the direction toward the box for collecting non-defective products to the direction toward the box for collecting defective products.
As a result, defective products can be sorted out from non-defective products. In the example described here, the portion for detecting an abnormality in the process after the gas injection is completed and the gas holding pressure is started is limited. However, the present invention is not limited to this.
As described above, the abnormality can be similarly determined in the detection after the start of gas injection. When an abnormality occurs, its cause can be known from the gas pressure, and feedback is given to an injection molding machine or a gas injection device so as to eliminate each cause. As described above, according to the control method of the injection molding apparatus of the present invention, the output from the gas pressure detecting means and the gas pressure indicated for each cause of the abnormal occurrence in the gas injection are indicated. An abnormal pattern of change and a normal pattern indicating a normal gas pressure change in gas injection are stored in a memory in advance, and it is determined whether or not the output from the gas pressure detecting means conforms to the normal pattern. Is determined to be abnormal, the injection molding machine or the gas injection device is controlled according to the cause of the abnormality so that the output from the gas pressure detecting means conforms to the normal pattern, and the molded article molded at the time of the abnormality is inspected. Since the selection means is driven to select good products, if an abnormality occurs in gas injection, it is necessary to automate the investigation of the cause and its countermeasures. Thus, the occurrence of defects can be suppressed, and efficient manufacturing can be achieved. Furthermore, when an abnormality occurs, defective products formed at the time of the abnormality can be automatically selected, so that defective products are not mixed and quality is guaranteed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a configuration of an injection molding apparatus applied to an embodiment of the present invention. FIG. 2 is a diagram showing an example of an algorithm of the embodiment of the present invention. FIG. 4 is a diagram showing another example of the algorithm according to the embodiment of the present invention. FIG. 4 is a diagram showing a voltage waveform pattern indicating gas pressure in gas injection. FIG. 5 is a diagram showing a voltage waveform pattern indicating gas pressure in gas injection. FIG. 6 shows the main part of the apparatus applied to the embodiment of the present invention. FIG. 7 shows the algorithm of this embodiment. Injection molding machine 3 ‥‥ Gas injection device 9 ‥‥ Selection means 10 ‥‥ Gas pressure detection device 4 圧 力 Pressure sensor 5 判別 Judgment unit 7 ‥ Memory 11 制 御 Control unit

Claims (1)

(57) [Claims] (1) A mold for forming a hollow portion inside a molded article, an injection molding machine for mounting the mold and injecting a molten resin into the inside, A gas injection device for supplying gas to a portion where a part is to be formed, gas pressure detection means for detecting a pressure of an injection gas provided in a gas passage to be formed in the mold from the gas injection device, Using an injection molding apparatus equipped with a sorting means for sorting out the molded products,
The output from the gas pressure detecting means, the abnormal pattern of the gas pressure change indicated for each cause of the abnormal occurrence in the gas injection, and the normal pattern indicating the normal gas pressure change in the gas injection are stored in the memory in advance. Then, it is determined whether or not the output from the gas pressure detecting means conforms to the normal pattern, and if not, it is determined that the output is abnormal, and the output from the gas pressure detecting means conforms to the normal pattern. Controlling the injection molding machine or the gas injection device according to the cause of the abnormality, and driving the selection means so as to select a molded product molded at the time of the abnormality as a defective product. Method.