JPH0339816B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for detecting the operating state of an injection molding machine, which is suitable for use in confirming the operating state during a molding cycle.

[Prior art and its problems]

In general, injection molding machines perform molding by repeating a predetermined molding cycle, and at this time, the operating state during the molding cycle is detected for the purpose of checking the operating state, confirming the quality of the molded product, finding the optimal molding conditions, etc. ing.

The conventional detection method detects the speed and pressure at fixed intervals (for example, 20 msec (total injection time: 5.5 sec)), and uses the detected data to inform the injection molding machine of the state that changes over time. It was displayed as a graph on an attached display and stored in a storage device. In other words, the operating state was detected using time as a variable.

However, since such conventional detection methods store pressure values at regular intervals, they require a large-capacity storage device, which poses the problem of increasing the size and cost of the entire device. On the other hand, it is conceivable to increase the detection time interval in order to reduce the number of detection points, but this does not allow accurate detection of pressure changes at points (pressure switching points) that change rapidly in a short period of time.

For example, FIG. 6 shows the change characteristics of the mold internal pressure in the pressure control region of the injection process detected by a conventional detection method. As is clear from the figure, a high injection pressure is applied initially to eliminate the filling shortage due to cooling contraction of the filled resin in the mold cavity, but after that, the injection pressure is reduced to prevent residual stress. It is switched to the low pressure side and held. However, since the detection point at the pressure switching point is detected every time to, it becomes rough, and even though the change characteristic is originally (Mo), there is a large deviation, and the detection result becomes (M1), etc. , there is a problem that accurate pressure detection cannot be performed.

[Means for solving problems]

The present invention aims to provide a method for detecting the operating state of an injection molding machine that solves the problems existing in the prior art described above. Continuously detect the pressure at Zp, sequentially detect the pressure at the time when the detected pressure changes by a preset constant pressure, and set a certain time, and if the pressure does not change by the constant pressure within the time, It is characterized in that the pressure at the time when the certain period of time has elapsed is detected.

[Effect]

Next, the operation of the present invention will be explained.

According to the operating state detection method according to the present invention, since the pressure (pressure value) at the time when the detected pressure changes by a constant pressure is sequentially detected, the sampling period changes in accordance with the degree of pressure change. In other words, if the pressure changes sharply, the sampling period becomes correspondingly shorter, and if the pressure changes gradually, the sampling period becomes correspondingly longer, and the sampling time is optimal depending on the degree of pressure change. The value will be automatically set. Furthermore, in places where the degree of change in pressure is particularly gradual, pressure is detected after a certain period of time has elapsed to ensure detection accuracy.

With such a detection method, extremely highly accurate pressure change characteristics can be obtained without increasing the total number of detection points.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in detail based on the drawings. Fig. 1 is a pressure change characteristic diagram detected by the method of the present invention, Fig. 2 is a side view of an injection molding machine equipped with an operating state detection device that implements the method of the present invention, and Fig. 3 is a diagram showing the characteristics of changes in pressure detected by the method of the present invention. FIG. 4 is a block circuit diagram of the detection system to be implemented, FIG. 4 is a characteristic diagram of changes in physical quantities in the injection process, and FIG. 5 is a characteristic diagram of changes in physical quantities in the speed control region.

First, the schematic configuration of the operating state detection device and the injection molding machine will be explained with reference to FIG. 2.

The injection molding machine indicated by reference numeral 1 in the figure is roughly divided into a machine stand 2, a direct pressure mold clamping device 3 installed on this machine stand 2, a movable mold 4a attached to the mold mounting surface of this mold clamping device 3, and a fixed mold. 4b, and an in-line screw type injection device 5 installed on a machine stand 2, these constitute a known injection molding machine.
Further, the machine base 2 has a built-in molding machine controller 6 and is equipped with an operating state detection device 20.

Next, the operating state detection device 20 will be explained. First, the mold clamping device 3 is provided with a mold clamping pressure detector 21 for detecting hydraulic pressure during mold clamping, and a movable platen position detector 22 for detecting the position of the movable platen to which the movable mold 4a is attached. The mold 4 also includes an in-mold resin temperature detector 23 that detects the temperature of the resin injected into the mold cavity, an in-mold pressure detector 24 that detects the resin pressure in the mold cavity, and an in-mold resin temperature detector 24 that detects the resin pressure in the mold cavity. A mold temperature detector 25 is attached to detect the temperature. Furthermore, the injection device 5 is provided with a heating cylinder temperature detector 26 for detecting the temperature of the heating cylinder, a screw position detector 27 for detecting the screw position, and an injection pressure detector 28 for detecting the hydraulic pressure during injection.

Each of these detectors 21 to 28 is converted, corrected, amplified, and A/D (analog-digital) as necessary.
It is connected to a slave CPU 37 via amplifiers 29 to 36 having functions such as conversion. Also, slave
The CPU 37 is connected to the main CPU 39 via the RAM 38, and the main CPU 39 is further connected to the display device 4.
0, external storage device 41, detection position interval setter 4
2. Connect the detection time interval setter 43 and the molding machine controller 6.

Further, a detection system for implementing the method of the present invention in the operating state detection device 20 will be explained with reference to FIG. In this figure, the same parts as in FIG. 2 are designated by the same reference numerals. First, a pressure sensor 52 is attached to a pressure detection object 51 such as an injection cylinder or a mold cavity.
This pressure sensor 52 is connected to a detection controller (slave CPU 37,
54 (including RAM 38 and main CPU 39). A molding machine controller 6 and a pressure interval setting device 55 are connected to this controller 54, and a RAM 56 is also connected.
A display device 40 such as a CRT or plasma display;
Recording device 57 such as an X-Y recorder or printer, external memory 41 such as a floppy disk or IC card
Connect to.

Next, detection of the operating state of the injection process, which is part of the molding cycle, will be described. a speed control region Zv in which the screw moves forward and fills the resin material accumulated in front of it into the mold cavity;
It consists of a pressure control region Zp that applies a predetermined holding pressure when filling is completed and the screw is almost stopped.

First, in the speed control region Zv, the position is set as a variable. In other words, the distance Lo between each detection point
is set by the detection position interval setter 42, and time is set as a variable in the pressure control region. The time To between each detection point is set by the detection time interval setter 43. Each setting device 42, 43
The conditions set in , detection items (injection speed, injection pressure, mold internal pressure), etc. are sent from the main CPU 39 to the RAM 38.
It is sent to the slave CPU 37 via.

Now, when an injection start signal is given to the main CPU 39 from the molding machine controller 6, this injection start signal is sent to the slave CPU 37 via the RAM 38, and the slave CPU 37 starts detection. At this time, the timer built into the slave CPU 37 starts measuring time. At the same time, when the screw starts moving forward and the screw moves forward by the distance Lo set in the detection position interval setting device 42, the injection speed, injection pressure, mold internal pressure and time are detected at this detection point and the speed control area is set. Each data in is stored in RAM38. Note that the injection speed is determined by differentiating the screw position with respect to time. Then, as the screw moves forward, it detects data at detection points every distance Lo set by the setting device 42 and writes the data to the RAM 38. RAM
The data written in 38 is sent to the main CPU 39, and after predetermined calculations are performed, it is displayed in real time on the display device 40 in a graph format as shown in FIG. 4 or in a list format using digital values, etc. Is displayed. In addition, Figure 4 shows the injection stroke.
4 molded products of 75mm (80~5mm) and injection time of 5.5 seconds.
This is a graphical representation of the case where molding was performed by speed 3-pressure process control, and the detection points in the speed control area Zv were set every 0.2 mm from the injection start position.

By the way, in the speed control region Zv, since the operating state is detected using the position as a variable, the speed change point when setting the optimum molding conditions can also be easily selected. First, FIG. 5a shows the change characteristics of the injection pressure obtained by molding a mold with unknown molding conditions at a single speed and a single pressure. Note that the characteristics shown in FIG. 1A do not have burrs or shots, but they do have jetting and internal stress. on the other hand,
Assuming that the shapes of the molded product 45 and the runner branch 46 are formed as shown in Figure b, a comparison of Figures a and b shows that the rise in pressure (shift point) exists at points B and C. It will be done. Point B is the point where the pressure increases as the resin passes through the gate, and point C is the point where the pressure increases as the mold cavity is filled with resin. Therefore,
The process can be controlled as shown in FIG. 3C using point B and point C as switching positions, thereby obtaining optimal molding conditions that can reduce the initial speed and eliminate internal stress due to overfilling. Note that since these points B and C appear as position information of the screw on the change characteristic (a in the same figure), these positions can be used as the set positions as they are.

On the other hand, the screw position changes from the speed control area Zv set in the molding machine controller 6 to the pressure control area Zp.
When the speed and pressure switching position is reached, the molding machine controller 6 outputs a command signal therefor, and the molding machine moves to the pressure control region Zp.

In the pressure control region Zp, the timer function of the detection controller 54 starts measuring time, and the in-mold pressure value at the start of the pressure control region,
The elapsed time from the start point is detected and stored in the RAM 56 as first data. RAM56
The data stored in is displayed on the display device 40 and recorded by the recording device 57.

On the other hand, a detection signal of the pressure inside the mold is continuously sent from the pressure sensor 52 to the detection controller 54, and is compared with the initially detected pressure value to determine the pressure deviation Pd. On the other hand, a constant pressure Po that determines the sampling interval is set in the pressure interval setting device 55,
When the pressure deviation Pd matches this constant pressure Po, the mold pressure value and time at that time are detected and stored in the RAM 56 as second data.

Similarly, the pressure deviation is calculated by comparing the current mold pressure value and the previously stored mold pressure value, and each time this pressure deviation Pd matches the constant pressure Po, it becomes the mold pressure value at that point. , time is detected and stored sequentially. In addition, if necessary, the timer function can be used to monitor the timer's timing and prevent pressure deviation even after a certain period of time has passed.
If Pd does not match the constant pressure Po, the in-mold pressure value and time are detected and stored after the certain period of time has elapsed. By using time detection in this way,
More accurate detection can be performed. When the injection process completion signal is issued from the molding machine controller 6, the pressure inside the mold and elapsed time at that point are detected and stored in the RAM 56 as final data, and all data in the RAM 56 is transferred to the external storage device 41. The data is stored, the RAM 56 is initialized, and the timer function is reset.

FIG. 1 shows the change characteristics of the mold pressure detected by the above method. As is clear from this, compared to the conventional model (Figure 6), the number of data points is smaller (9 points compared to 23 points in the conventional model), but the number of data points at the pressure switching point is conversely larger, and the characteristic curve itself is Accuracy is improved.

Although the embodiments have been described in detail above, the present invention is not limited to these embodiments.
For example, although the injection process has been described as an example, the present invention can be applied to any process including a mold clamping process. Further, the physical quantities related to the operating state may be mold temperature, resin temperature in the mold, heating cylinder temperature, screw position, etc., and the pressure detection may be the pressure inside the mold clamping cylinder in the mold clamping process. Other detailed configurations, methods, etc. may be modified as desired without departing from the gist of the present invention.

[Effects of the Invention] As described above, the method for detecting the operating state of an injection molding machine according to the present invention continuously detects the pressure in the pressure control region during the molding cycle, and detects when the detected pressure changes by a preset constant pressure. Since the pressure value is detected, the following remarkable effects are achieved.

The sampling period changes according to the degree of change in pressure, and the optimum sampling interval is automatically and variably set each time. In other words, the sampling interval becomes denser in the part where the change is steeper.
The slower the change, the rougher the part, allowing for highly accurate, efficient, and accurate detection.

Checking the operation of injection molding machines, checking the quality of molded products,
These analyzes and the search for optimal molding conditions can be performed easily and accurately.

An appropriate storage device is sufficient and can contribute to miniaturization and cost reduction of the device.

[Brief explanation of the drawing]

Figure 1: Characteristic diagram of pressure changes detected by the present invention, Figure 2: Side view of an injection molding machine equipped with an operating state detection device for implementing the method of the present invention, Figure 3: Implementing the method of the present invention. Figure 4: Characteristic diagram of changes in physical quantities in the injection process; Figure 5: Characteristic diagram of changes in physical quantities in the pressure control region; Figure 6: Diagram of operating conditions detected by conventional methods. Characteristic diagram of changes in physical quantities. In the drawing, Zp: pressure control area.

Claims (1)

[Claims] 1. In a method for detecting the operating state of an injection molding machine having a pressure control area during a molding cycle, the pressure in the pressure control area is continuously detected, and the pressure at the time when the detected pressure changes by a preset constant pressure is sequentially detected. At the same time, set a certain time,
A method for detecting an operating state of an injection molding machine, characterized in that when the pressure does not change by the constant pressure within the time period, the pressure at the time when the certain time period has elapsed is detected.