JPH03207627A - Method for controlling injection molding machine - Google Patents

Abstract

PURPOSE:To stably mold a superior product by forming the temp. curve at every shot in a heat sensor arranged region on the basis of the measured data from the heat sensor arranged in the vicinity of the resin filling part in a mold by a microcomputer and reflecting the same in the control of molding. CONSTITUTION:A microcomputer 1 taking charge of the control of the whole of an injection molding machine executes the control of the whole of a molding process such as the opening and closing of a mold, injection, pressure holding, charging or cooling and various operational processings such as the statistical operational processing of measured data. At the time of trial shot operation, the microcomputer 1 controls a solenoid control valve so as to turn the same off or to throttle the flow rate thereof in order to rapidly bring the temp. of a mold to a stable region. After the completion of the trial shot operation, continuous molding operation for molding a product is taken. Even when a temp. curve slightly shows irregularity at every shot, an injection process is started by an injection drive source at the point of time becoming the temp. optimum to the start of injection.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a method for controlling an injection molding machine, in particular, by grasping the temperature curve at a position as close as possible to the mold cavity.
This invention relates to a control method for an injection molding machine that reflects this in molding control.

[Conventional technology] When performing molding work using an injection molding machine in automatic operation, it would be meaningless if the molded products ended up in a pile of defective products. Molding operating conditions are carefully set. Then, the microcomputer (hereinafter referred to as microcomputer) that controls the entire molding machine executes automatic operation by referring to the measurement data from various sensors based on the preset molding operation condition values, and continuously molds the molded product. It has become quite imposing.

By the way, the mold temperature, which is one of the above-mentioned molding operation conditions, has not been given much consideration in the past. The only controls were to measure the temperature and keep it constant. [Problem to be solved by the invention] As is well known, in an injection molding machine, mold opening/closing, injection/pressure holding, charging/cooling are repeated in each cycle.
Within one shot cycle, the temperature of the cavity portion of the mold is repeatedly increased and cooled, and this portion draws a certain temperature curve for each shot. However, with conventional injection molding machines, l
Although the mold surface temperature, which has almost no temperature change throughout the shot, is measured, no consideration has been given to the temperature curve for each shot. For this reason, even if various molding conditions such as injection speed, injection pressure, and heating cylinder temperature are precisely controlled, if there are variations in the temperature curve for each shot as described above, this will adversely affect the quality of the high-profile product. was there.

Incidentally, research has shown that Q. The variation factor that causes the dimensional difference in Qlmm is 3 to 3 for the heating cylinder temperature.
It is said that the variation is 6°C, and the variation in injection resin pressure is about 20kg/(d, while the variation in mold temperature is 3°C.

In addition, in conventional injection molding machines, no consideration is given to the temperature rise time of the mold at the start of operation (during test shots), and it takes 140 to 1
A large number of shots, 50 shots, were required.

The present invention has been developed in view of the above points, and its purpose is to detect the temperature near the cavity of the mold, recognize the temperature curve for each shot of this area, and use this to control molding. It is an object of the present invention to provide a control method for an injection molding machine that can stably mold good products without variation. Another object of the present invention is to provide a control method for an injection molding machine that can significantly shorten the time it takes for the mold temperature to reach a stable range at the start of operation (during a test shot). be.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention uses a microcomputer to drive and control each part of the molding machine based on each set operating condition value and measurement information from each sensor. In a method for controlling an injection molding machine equipped with the above-mentioned
a thermal sensor disposed at a remote location), a valve means for turning on/off or controlling the flow rate of a cooling medium flowing into the mold, and a medium temperature control means for controlling the temperature of the cooling medium. The microcomputer creates and monitors a temperature curve (inside the mold) for each shot during continuous molding operation based on the measurement information from the heat sensor, and starts injection when the temperature monitoring area reaches a predetermined temperature. be instructed. Further, the microcomputer compares the temperature curve for each shot during continuous high-speed operation, and controls the temperature of the cooling medium by the medium temperature control means so that the temperature curve for each shot is stable over a long period of time. It is made to have variable control. Further, the microcomputer controls the valve means to turn off or reduce the flow rate so that the mold temperature quickly reaches a stable region during a test shot at the start of operation.

[Function] Figure 2 is a diagram showing a temperature distribution simulation of the main parts in the mold, where l1 is the mold, 12 is the molded product (resin) in the cavity of the mold, and 13 is the temperature distribution in the mold 11. Immediately after filling, the temperature distribution of the mold l1 between the cavity and the flow path 13 becomes as shown in ■, and after 5 seconds of filling, Afterwards, the temperature distribution becomes as shown in ■, and just before the product (molded product) is taken out, the temperature distribution becomes as shown in 57
It shows a variation of ~69°C. The mold temperature at a location 1m away from the cavity surface is detected using, for example, a thermocouple, and this measurement information is sent to the microcomputer that controls the entire injection molding machine. For example, a temperature curve CT along the time axis of the temperature monitoring site (temperature monitoring site) is generated in real time as shown in the third diagram. This temperature curve C
Immediately after each shot, 'r is raised to a predetermined temperature by the amount of heat given from the molten resin, and then the heat is removed by the cooling medium and the temperature is lowered to the predetermined temperature, repeating a cycle.

According to experiments conducted by the inventors, if the conventional method is used, the temperature curve CT tends to vary from shot to shot (particularly when there is variation in the filling weight or heating cylinder temperature, or when there is a difference in time during continuous molding over a long period of time). If the injection start point is determined simply by time, the temperature at the temperature measurement point (in other words, the surface temperature of the cavity) at the injection start point will not be constant.
It has been found that this causes variations in the quality of molded products. In addition, according to experiments conducted by the inventors, it has been found that good products can be stably molded if the temperature at the temperature measurement point at the injection start timing is always kept at a suitable temperature (for example, about 57°C in the illustrated example). Ta.

Therefore, the microcomputer monitors the temperature curve CT created in real time, and instructs to start injection when the temperature at the temperature measurement point reaches a suitable temperature, thereby eliminating variations in the temperature curve CT for each shot. Even if there is, the area of the hatched region S in FIG. 3 is approximately constant, making it possible to mold good products without variation.

In addition, even if the temperature on the injection side (heating cylinder side) and the temperature of the mold cooling medium (mold temperature control medium) are constant, the temperature curve CT may change over the long term due to changes in the outside temperature, for example. It is possible that it will change depending on what you see.

For example, if the one shot period in the temperature curve CT tends to increase from the set value, or if the maximum temperature in the temperature curve CT is high, then the amount of heat Q that is removed per shot period compared to the amount of heat QIN given to the mold. . It is thought that LIT tends to be close to QIN>QoU1. Therefore, the microcomputer monitors the temperature curve CT for each shot over a long period of time, and uses the medium temperature control means to control the temperature of the cooling medium so that the temperature curve CT is stabilized at a predetermined value, although not in real time and gradually. Variable temperature control. That is, in the above-mentioned case (for example, if the one-shot period in the temperature curve CT tends to increase from the set value, or if the maximum temperature in the temperature curve CT is high), the medium temperature may be changed from, for example, 50°C to 49°C. change to

Furthermore, it is desirable to allow the mold temperature to quickly reach a stable region during the test shot at the start of operation, from the viewpoint of the time factor and reduction of waste of material due to test shots (dump shots). Therefore, the microcomputer controls the valve means to be turned off or the flow rate to be reduced so that the mold temperature quickly reaches the stable region during the test shot at the start of operation, thereby reducing the QIN1QOI per shot.
During this period, the JT relationship is set such that QIN>Qou7, and the mold temperature is quickly raised to a stable region. By doing this, as shown in FIG.
What used to require 40 to 150 shots can now be shortened to a few dozen shots or less, as shown by line A in the figure.

[Example] Hereinafter, the present invention will be explained using an example shown in FIGS. 1 to 5.

FIG. 1 is a block diagram showing the mold temperature control system of the injection molding machine. In the figure, 1 is a microcomputer that controls the entire injection molding machine, and controls the entire molding process such as mold opening/closing, injection/holding, charging/cooling, etc., as well as various calculation processes such as statistical calculation of measurement data. Execute. A predetermined storage area of the microcomputer 1 stores various molding condition values input and set in advance, and based on this setting condition data and a molding process control program created in advance, the microcomputer 1 controls the injection molding process. While referring to measurement information etc. from various sensors installed in various parts of the machine, a mold opening/closing drive source, an injection drive source, a charge drive source, etc. (not shown) are drive-controlled via a group of drivers, A series of automatic shaping steps are executed.

Reference numeral 11 denotes the mold described above, and the mold 11 is located at a position as close as possible to the cavity surface, that is, in this embodiment, one cabinet from the cavity surface (prestigious product surface) as shown in FIG. A thermal sensor 2 consisting of a thermocouple is disposed at a position separated by the same distance.

The measurement information by the thermal sensor 2 is sent to the microcomputer 1, and the microcomputer 1 creates and recognizes the temperature curve CT of the area where the thermal sensor 2 is installed, as shown in FIG. 3, for example. It has become so. Also, mold 1
A cooling medium supplied from a pump 4 driven by a motor 3 flows through the cooling medium (water, oil, etc.) passage 13 provided in the cooling medium 1 through a heater 5 and an electromagnetic control valve 6. During continuous molding operation in a stable state, the cooling medium that has passed through the mold 11 is returned to the bomb 4 via the check valve 7.

The electromagnetic control valve 6 has an ON/FF control function and an aperture function, and is controlled by the microcomputer 1 via a driver 8. Note that the electromagnetic control valve 6 is
When performing FF control, the cooling medium does not pass through the mold 11 but returns to the pump 4 via the check valve 7. Reference numeral 9 denotes a thermal sensor consisting of a thermocouple disposed in the flow path between the heater 5 and the electromagnetic control valve 6. Temperature information of the cooling medium measured by the thermal sensor 9 is sent from the microcomputer 1. The command value is input to the servo amplifier 10 that drives the heater 5,
The servo amplifier 10 drives and controls the heater 5 so that the temperature of the cooling medium matches the temperature instructed by the microcomputer 1.

In addition, in FIG. 1, 14 is a control valve used when releasing the cooling medium to the tank 15.

In the above-described configuration, at the start of operation when the mold temperature is not warmed by heat from the molten resin, that is, during test shot operation, the microcomputer 1 controls the electromagnetic control valve so that the mold temperature quickly reaches a stable region. 6 is turned off or the flow rate is controlled to cut or limit the amount of cooling medium supplied to the mold 11. As a result, the amount of heat Q IN is given to the mold 11 from the molten resin per shot, and the amount of heat Q is taken away by the cooling medium. Regarding the relationship with LIT, Q. ．． >Q. The mold temperature is quickly raised to a stable range so that υ〒. Therefore, first
As explained using the diagram, compared to the conventional method, the mold temperature is in a stable region (for example, a region where the lowest temperature in the temperature curve CT is approximately 57°C and the temperature curve CT is approximately uniform for each shot). It is possible to significantly reduce the number of test shots required to achieve the desired result, significantly reduce the start-up time, and also greatly reduce wasted material due to test shots (discarded shots).

After the above-mentioned test shot is completed, the continuous molding operation for molding the product is started. FIG. 5 shows a detailed pattern of the (mold) temperature curve C'r at the temperature measurement point for one shot (one cycle) during this continuous molding operation,
It is an explanatory view showing a screw tip resin pressure curve Ps, an injection speed curve Vs, and an in-mold resin pressure curve Pm at the same time. In the figure, the vertical axis is -1 for the resin pressure at the screw tip.
0.00~70. OOkg/cffl, 0.00 to so. at mold temperature. oo℃, -1 at injection speed
The range of 0.00-100.0 in/sec and the resin pressure in the mold is -100.0-700.0 kg/all, respectively, as full scale. In addition, in the same figure, the product to be shaped is a disk, and the cooling medium (
The measurement data is shown when the temperature (mold temperature control medium) is 50±0.5°C.

In this embodiment, even if the temperature curve CT shows some variation for each shot, the microcomputer 1 constantly monitors the temperature curve CT, and the mold temperature at the temperature measurement point becomes, for example, 57+0.5°C. At this point (when the temperature reaches the optimum temperature for starting injection), an injection drive source (for example, an injection cylinder) not shown is used to start the injection process.
FIG. 5 shows that this injection start time Ts is 0 on the time scale.
Indicated by OO. By doing this, as explained earlier using FIG. 3, the area of the hatched area S in FIG. It is possible to keep the temperature rise characteristic line, which is important for control, constant, and it is possible to stably mold good products. There is no problem).

Further, the microcomputer 1 stores the data of the temperature curve C7 of each shot, and performs statistical calculation processing on this stored data to determine whether the temperature curve data changes in the direction of overheating in a considerable period of time as seen from the setting data. We are monitoring whether there is a trend or a transition trend towards cooling. That is, for example, if the temperature curve data shows a tendency to transition toward overheating as seen from the setting data, the amount of heat Q that is removed per shot period relative to the amount of heat QIN given to the mold. IJT, Q. N
＞Since it is thought that there is a tendency towards QoIJT, microcontroller 1 is not real-time and is slow, but
In order to stabilize the temperature curve C7 at a predetermined value, the temperature of the cooling medium is adjusted from 50° C. to 49° C., for example, by the heater 5.
variably controlled so that By doing so, it becomes possible to control the temperature curve CT to show a generally stable and uniform change in the long term.

[Effects of the Invention] As described above, according to the present invention, the temperature near the mold cavity is detected, the temperature curve for each shot in this area is recognized, and this is reflected in molding control to ensure stability without variation. In addition, it is possible to provide a control method for an injection molding machine that can significantly shorten the time it takes for the mold temperature to reach a stable range at the start of operation (during a test shot). As an impressive seed injection machine, its industrial value is enormous.

[Brief explanation of drawings]

The drawings all relate to embodiments of the present invention; Fig. 1 is a block diagram showing the mold temperature control system of an injection molding machine, and Fig. 2 shows the temperature distribution of main parts in the mold over time. Explanatory diagram, Figure 3 is an explanatory diagram showing temperature curves in successive shots, Figure 4 is an explanatory diagram showing temperature curves in consecutive shots.
The figure is an explanatory diagram showing how the mold temperature transitions to the stable region at the start of operation. Figure 5 shows the detailed pattern of the temperature curve for one shot during continuous molding operation, including the screw tip resin pressure curve, injection speed curve, It is an explanatory view shown in comparison with an in-mold resin pressure curve. 1...Microcomputer (microcomputer), 2
...Thermal sensor, 3...Motor, 4...
... Bomb, 5 ... Heater, 6 ...
・Solenoid control valve, 7...Check valve, 8...
...Driver, 9...Thermal sensor, 1o...
...Servo amplifier, l1...Mold, 12...
...Majestic item, l3...Flow path.

Claims (4)

[Claims] (1) In an injection molding machine equipped with a microcomputer that drives and controls each part of the molding machine based on each set molding operation condition value and measurement information from each sensor, the microcomputer controls the resin filling in the mold. The injection method is characterized in that a temperature curve is created for each shot at the part where the heat sensor is installed based on measurement information from a heat sensor placed near the part, and the temperature curve is reflected in molding control. How to control a molding machine. (2) In claim 1, the microcomputer monitors the temperature curve for each shot during continuous molding operation, and instructs to start injection when the temperature monitoring area reaches a predetermined temperature. How to control an injection molding machine. (3) In claim 1, the microcomputer is provided with a valve means for controlling ON/OFF or flow rate of a cooling medium flowing into the mold, and the microcomputer is configured to control the mold temperature during a test shot at the start of operation. A method for controlling an injection molding machine, comprising controlling the valve means to turn off or reduce the flow rate so as to quickly reach a stable region. (4) In claim 1, the microcomputer further comprises medium temperature control means for controlling the temperature of the cooling medium flowing into the mold, and the microcomputer is configured to control the temperature curve for each shot during continuous molding operation over a long period of time. 1. A method of controlling an injection molding machine, characterized in that the temperature of the cooling medium is variably controlled by the medium temperature control means so that the temperature of the cooling medium is stable over a period of time.