JPS5933102B2 - Injection molding control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that monitors molding process variables within a molding die and uses the information to control the amount of current supplied to a heating element to control the state of molten resin at a gate portion. It is.

In the injection molding process, various factors have a complicated relationship with each other.

Therefore, it is necessary to continuously mold stable molded products by controlling unstable factors involved in the injection molding process. In particular, factors such as the timing of switching from primary injection pressure to holding pressure in the injection filling process of molten resin and the pressure inside the mold of molten resin affect the final filling state of the molded product and have a large impact on molding quality. . For this reason, various control methods have been developed to control these factors. For example, 1) Detecting the extreme fat pressure in the mold with a pressure sensor via an extrusion press, etc.
A method of switching to holding pressure at that point when the resin pressure reaches the set value.

Ii) A method of detecting the hydraulic oil pressure of the injection cylinder and switching to holding pressure when the hydraulic oil pressure reaches a set value. 111') There is a method of detecting the amount of opening of the mold parting surface or the amount of mold displacement due to resin pressure during injection, and changing to holding pressure at that point when these physical quantities reach a set value.

In the above-mentioned method, there are a wide variety of target values to be managed, and the control amounts are all concentrated in the molding conditions of the injection molding machine, so the gate that supplies molten resin to the molded product cavity is Good results can be expected if the area is affected. On the other hand, in the case of so-called multi-cavity molding in which molded products with different shapes such as wall thickness and dimensions are simultaneously molded, or in the case of large molded products with multiple gates and molten resin supplied from multiple points simultaneously, injection In addition to the molding conditions of the molding machine, it is necessary to appropriately control the balance between these gates.

This is because, in a multi-point gate system for multiple moldings or large molded products, if the state of the molten resin at each gate changes, the quality of each molded product may vary, and burrs may occur. This is because molding defects such as short shots may occur. Therefore, the conventional control method described above, which only controls the molding conditions of an injection molding machine, cannot provide satisfactory control in a multi-gate system for multiple holes or large molded products that requires controlling the balance between gates. In view of the above-mentioned points, the present invention enables sufficient control in a multi-point gating system for multi-piece cutting or large-formed products, and allows continuous production of stable molded products. It is an object of the present invention to provide an injection molding control device that can perform molding.

The present invention measures molding process variables for each molded product cavity, compares the detected values with preset target values,
The present invention is characterized in that the amount of current supplied to the heating element is individually controlled for each gate portion in accordance with the deviation from the target value.

Hereinafter, specific examples of the injection molding control method and apparatus of the present invention will be described with reference to the accompanying drawings. First, the inventor investigated the relationship between the amount of current supplied to the hot chip tip heater and the state of the molten resin at the gate (a cavity molding process variable).

Conventionally, a control circuit shown in FIG. 1 has been employed as a means for adding a switching function to a gate section using a hot-chip heater.

That is, the heater power supply 24 supplied to the heater 21 via the temperature regulator 23 is switched by the magnetic relay 22 to adjust the power supply. The relationship between the supply current controlled by this system and the temperature at the tip of the hot chip over time has the relationship shown in FIG. 2, and the temperature at the tip of the hot chip during the period of time when the hot chip is filled with molten resin exhibits a substantially constant value. However, in order to accurately adjust the gate balance, it is necessary to be able to set it arbitrarily even during the time when the tip of the hot chip is being filled with molten resin. Therefore, the inventor of the present invention adopted a solid state relay shown in FIG. 3 and studied a means for controlling the heater supply current using a pulse signal.

As a result, it became possible to arbitrarily control the heater supply current and hot chip tip temperature. That is, as shown in FIG. 3, the above-mentioned means 3 supplies the heater supply power 24 to the heater 21 via the solid state relay 25, and sends a reference signal to the control signal input terminal 26 of the solid state relay 25. A control pulse signal is applied to the clock to control the switching of the solid state relay 25, thereby controlling the power supplied to the heater 21. As a result, the current supplied to the heater 21 became pulsed as shown in FIG. 4, and the temperature at the tip of the hot chip changed in response to the pulse signal, making it possible to obtain an arbitrary temperature pattern along the time axis. Furthermore, the inventor investigated the temperature characteristics of the tip of the hot chip using the above-mentioned system.

As a result, the correlations shown in FIGS. 5 and 6 were confirmed between the control pulse signal and the hot chip tip temperature, and between the hot chip tip temperature and the maximum mold pressure, which is one of the molding process variables, respectively. In other words, the hot chip tip temperature tends to increase as the number of pulses increases under a constant set current, and the maximum pressure inside the mold tends to increase as the hot chip tip temperature increases under constant molding conditions of the injection molding machine. It is in. Based on this basic data, the correlation between the control pulse signal and the molding process variables was examined, and the results shown in FIG. 7 were confirmed. That is, when the control pulse signal is changed while the injection molding conditions are kept constant, the molding process variables change approximately linearly. Therefore, if a deviation occurs between the molding process variable and the set value due to the influence of so-called disturbances such as changes in mold temperature, cooling water, and molten resin viscosity, the amount of correction of the control pulse signal must be output in accordance with the deviation. It is possible to correct the deviation and perform control so that it always converges to the set value. Focusing on the above-mentioned phenomenon, the present inventor observes the in-mold pressure behavior of each molded product cavity as a molding process variable, constantly compares this information with set target value data, and responds to the deviation as necessary. By outputting a corrected signal, the molding process variable always becomes the target value.

Hereinafter, one embodiment of the injection molding control device of the present invention will be described with reference to FIG.

In the figure, 1 is an injection molding machine, 7 and 8 are cavities 6a,
6b, a fixed type and a movable type.

A runner 3 constituted by a manifold 2, a hot chip 4 with small thermal inertia, and a hot chip tip heater 5 are incorporated into the fixed mold 7. The control device in the above-mentioned molding die includes an in-mold pressure transmitting pin 9 and an in-mold pressure sensor 10 that are incorporated in each cavity 6a, 6b in the movable mold 8, and a mold that is linked to the in-mold pressure sensor 10. An internal pressure transducer 11 and a digital setting device 13 for setting target values of molding process variables compare the detected value of the mold internal pressure transducer 11 with the target value of the digital setting device 13 and determine the deviation from the target value. Controller 1 outputs a control pulse signal according to
2, and a solid state relay 14 that controls the amount of current supplied from the power supply 15 to the hot chip tip heater 5 in accordance with the control pulse signal of the controller 12.

Next, a method of controlling injection molding according to the present invention using the above-mentioned apparatus will be explained. When molten resin is supplied from the injection molding machine 1, the molten resin passes through the manifold 2, runner 3, and hot socket 4 in the fixed mold 7, and enters each cavity 6a.
, 6b.

Information on the filling behavior of the molten resin at this time is measured by an in-mold pressure sensor via an in-mold pressure transmission pin 9 built into the movable mold 8, and is transmitted to the controller 12 via an in-mold pressure transducer 11. be done. On the other hand, the controller 12 compares and calculates the target value of the molding process variable inputted from the digital setting device 13 and the information on the filling behavior, converts the correction amount according to the deviation from the target value into a control pulse signal, The control pulse signal is sent to the solid state relay 14~
Output. As a result, the temperature of the hot chip tip heater 5 is set appropriately with respect to the molding process variables, and the molding state is always controlled to the target value. In this way, in the present invention, the gate state is controlled individually according to the process variables of each cavity, and the gate balance can be properly controlled in large molded products and multi-section molded products. Molding defects caused by poor balance can be completely eliminated.

Furthermore, since the molding process variables are tracked and controlled, it is possible to minimize variations in the molding state between each molding shot, making it possible to continuously mold stable, high-quality molded products. be. Note that, as in the above embodiment, if the amount of current supplied to the hot chip tip heater 5 is controlled using the solid state relay 14, there are effects such as high reliability and simple structure. .

Further, in addition to the solid state relay 14, for example, a thyristor or a power transistor may be used.

[Brief explanation of the drawing]

Figure 1 is a hot chip switching control circuit diagram using a magnetic relay, and Figure 2 is a graph showing temporal changes in the current supplied to the hot hand tip heater and the hot chip tip temperature using the control system shown in Figure 1. , Fig. 3 is a hot chip switching control circuit diagram using a solid state relay, and Fig. 4 shows temporal changes in the current supplied to the hot chip tip heater and the hot chip tip temperature by the control system shown in Fig. 3. Graphs, Figure 5 is a graph showing the correlation between the control pulse signal and the hot tip tip temperature, Figure 6 is a graph showing the correlation between the hot chip tip temperature and the maximum pressure value in the mold, and Figure 7 is the graph showing the correlation between the control pulse signal and the hot tip tip temperature. A graph showing the correlation between pulse signals and molding process variables, and FIG. 8 is an explanatory diagram showing an embodiment of the injection molding control device of the present invention. 1...Injection molding machine, 4...Hot chip, 5...Hot chip tip heater, 6a, 6
b...Cavity, 7...Fixed type, 8
......Movable type, 9...In-mold pressure transmission pin, 10...In-mold pressure sensor, 11...
・In-mold pressure transducer, 12...Controller, 1
3...Digital setting device, 14...Solid state relay, 15...Power supply.

Claims (1)

[Claims] 1. A multi-gate injection molding device for multi-cavity or large molded products, in which a pressure sensor is provided in each molded product cavity, and the pressure detected from each pressure sensor is compared with a preset target pressure. A comparison means for detecting the deviation is provided, a hot tip is provided between the runner and each cavity,
A control means for providing a heater at the tip of the hot tip, providing an electronic switch for controlling the supply current to each heater, and controlling the electronic switch using a pulse signal obtained based on the deviation detected by the comparison means. An injection molding control device characterized by being provided with.