JPS6285920A - Control method for injection molding machine - Google Patents

Abstract

PURPOSE:To offer a high-speed, stabilized injection molding by utilizing the sensor to sense the inner mold pressure and hydraulic pressure, connecting the inner mold pressure control circuit and the hydraulic pressure control circuit in the cascade and controlling hydraulic pressure. CONSTITUTION:The inner mold pressure sensor 4 to sense the resin pressure is provided in the cavity 2 or in the flow channel of mold 1 for injection molding, and the hydraulic sensor 6 to sense the injection hydraulic pressure is provided in the injection ram 5 to sense each of the said pressure. The inner mold pressure control circuit 13 to control the output of sensor 4 and the injection hydraulic control circuit 12 to control the output of sensor 6 are connected to the cascade. By varying the set value of injection hydraulic control circuit 12 according to the sensing value of inner mold pressure, to the set value out of the inner mold pressure control circuit 13 based on the setting inner mold pressure value and to the sensing value of injection hydraulic pressure, injection, charging and dwelling, or the injection hydraulic pressure under being charged and dwelt are controlled.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a control method for an injection molding machine, and particularly to a control method that uses a mold internal pressure control circuit and an injection hydraulic pressure control circuit in a cascade. be.

<Prior Art> Conventionally, in this type of control device, control has been performed based on a detection value detected by a molten resin pressure sensor installed in a mold and a set target pressure value in the mold. In addition, in this type of equipment, regarding the response of the mold internal pressure to the injection oil pressure, the so-called dead time and time constant from the time the oil pressure rises until the resin pressure starts to change feed-pumps the output of the oil pressure sensor. It is much larger than a single control system, and has the disadvantage that the position of the sensor within the mold is limited to close to the sprue in order to reduce its influence.

Furthermore, in order to compensate for the above-mentioned delay in pressure response, methods are being considered in which a curve pattern such as a standard first-order lag in the set value of the mold internal pressure is generated temporally at an early point in time for control. .

<Problems to be Solved by the Invention> Even in the latter method described above, there is a limit to increasing the response of the hydraulic pressure as long as there is the aforementioned response delay, and in order to increase the speed, it is necessary to increase the surge pressure once. We had no choice but to take measures such as controlling the problem after it occurred. In addition, because the response of the oil pressure cannot be increased due to the above-mentioned reasons, if you try to repeat a certain pattern by that amount, the adjustment accuracy will decrease as the injection speed increases, and the injection cylinder and mold temperature will decrease. There is a drawback that it becomes impossible to control if there are large fluctuations due to factors other than pressure, such as.

The present invention eliminates the drawbacks of the conventional examples described above, and provides a control method for an injection molding machine that has high-speed response, good reproducibility, and can be controlled at a position away from the sprue without causing surge pressure or hunting phenomenon in the mold internal pressure. The purpose is to

<Means for Solving the Problems> A control method of the present invention to achieve the above-mentioned object will be explained using FIG. 1 corresponding to an embodiment. 2 or an in-mold pressure sensor 4 for detecting resin pressure in the flow path and a hydraulic pressure sensor 6 for detecting injection oil pressure in the injection ram 5 to detect the respective pressures and to The mold internal pressure control circuit 13 and the injection hydraulic pressure control circuit 12 that control the output are connected in cascade, and the detected value of the mold internal pressure and the set value from the mold internal pressure control circuit 13 based on the set mold internal pressure value and the injection hydraulic pressure are controlled. The setting value of the injection hydraulic pressure control circuit 12 is changed according to the detected value to adjust the injection hydraulic pressure during injection, filling, pressure holding, or filling and pressure holding.

Function> When molten resin is injected into the mold 1, the mold internal pressure control circuit 13 calculates the deviation between the mold internal pressure detected by the mold internal pressure sensor 4 and the set mold internal pressure value by PID calculation. The result is outputted to the hydraulic control circuit 12 as a set value from the mold internal pressure control circuit 13, and the deviation between the aforementioned set value and the detected value (output) from the hydraulic sensor 6 is calculated by PID in the hydraulic control circuit 12. The injection hydraulic pressure is adjusted and controlled by changing the set value (output) of the hydraulic pressure control circuit.

The pressure detected at two points in this way is the deviation between the resin pressure inside the mold and the set value at that moment in terms of the internal pressure of the mold.
In addition, it is possible to calculate the pressure that the hydraulic circuit should take from now on according to the deviation from the PID calculation, and the hydraulic control circuit can respond accurately and with high response to the set value from the mold internal pressure control circuit. It is possible to adjust the injection hydraulic pressure, and even if the response is high, it will not go too far as in the past. Therefore, the mold internal pressure rises rapidly at the initial stage of pressure rise, but the injection hydraulic pressure reaches the proportional band before the mold internal pressure reaches the proportional band of the mold internal pressure control circuit. The wasted time of pressure transmission, which is seen in the one-point detection method, is significantly reduced, and as a result, predictive control is performed, allowing stable injection molding without overshooting the mold internal pressure.

<Example> Embodiments of the present invention will be described based on the drawings.

FIG. 1 is a block diagram of an injection molding machine according to the control method of the present invention.

An in-mold pressure sensor 3 that detects the resin pressure in the cavity 2 or flow path of the mold 1, and a hydraulic sensor that detects the injection oil pressure in the hydraulic circuit of the injection ram 5 that injects the molten resin in the injection cylinder 4. 6 and a speed sensor 7 for controlling the speed of the injection cylinder 4, the hydraulic circuit of the injection ram 5 transfers the oil pressure to the servo pulp drive amplifier 10 via the injection speed control/in-mold pressure control switching circuit 11. The pressure is adjusted by the servo pulp 9 to a pressure proportional to the output of the injection speed setting device 1, and the speed set by the injection speed setting device 1 and the output from the speed sensor 7 are connected to the switching circuit 11 by the servo pulp 9 for controlling the speed. The input is input through the amplifier 8, and after initially operating in the injection speed control state, the output of the mold pressure sensor 3 is passed through the mold pressure sensor amplifier 15, and when the pressure reaches the pressure set by the switching pressure setting device 17, the injection speed is changed. Control - It plays a role of switching via the timing controller 16 for in-mold pressure control switching.

Further, the hydraulic servo amplifier 12, which serves as a hydraulic control circuit, receives the in-mold pressure from the servo amplifier 13 for in-mold pressure, which passes the output from the in-mold pressure sensor 3 to the in-mold pressure sensor amplifier 15, which becomes an in-mold pressure control circuit. A switching circuit 11 is configured based on the value set by the setting device 14 and the output of the oil pressure sensor 6.
The hydraulic circuit is configured to control the hydraulic circuit via the hydraulic circuit.

Next, its operation will be explained with reference to FIG. Figure 2 shows the operating waveform diagram of the mold pressure (P), where %PI is the injection speed control-mold pressure control switching pressure set value, P2 is the mold pressure set value, T is the speed control injection area, and T2 is the gold It represents the mold internal pressure controlled injection area.

First, resin is melted and measured by the injection cylinder 4 and injected into the cavity 2 of the mold 1 at a speed set by the injection speed setting device 18 .

Then, as the injection progresses and the mold internal pressure of the cavity 2 rises and reaches the pressure P1 set by the switching pressure setting device 1γ, the injection speed control/mold internal pressure control switching circuit 11 uses the mold internal pressure. Feedback control is performed.

In the feedback control operation, the output from the mold pressure sensor 3 is amplified by the mold pressure sensor amplifier 15, and the mold pressure setting device 14 is sent to the mold pressure servo amplifier 13.
It is input together with the value P2 set by. Therefore, the deviation between the set value and the detected value is subjected to PID calculation using a thick time constant, and is sent as the set value to the hydraulic servo amplifier 12. The hydraulic servo amplifier 12 calculates the deviation between the output of the oil pressure sensor 6 and the output of the mold pressure servo amplifier 13 using a small high-speed response time constant, and controls the servo pulp 9 through the servo pulp drive amplifier 10. The resin is injected into the cavity 2 by adjusting the pressure of the injection ram 5.

In this way, by controlling using one control circuit, the pressure detected at two points as described above is the same as the resin pressure in the mold at that moment and the set value for the internal pressure of mold 1. In addition, in the servo amplifier 12, which is the hydraulic control circuit, the pressure inside the mold, which is the internal pressure control circuit, can be calculated. It becomes possible to accurately adjust the injection oil pressure with high response to the set value from the servo amplifier 13.

Therefore, the mold internal pressure rises rapidly at the beginning of the pressure rise, but the injection hydraulic pressure is adjusted to the proportional band before the mold internal pressure reaches the proportional band of the mold internal pressure servo amplifier 13. , the wasted time of pressure transmission as seen in the one-point detection method is greatly reduced, and as a result, predictive control is performed, and the mold internal pressure is reduced to the level shown in Figures 3 and 4. In-mold pressure waveform diagram during high-speed injection in conventional example (
However, R, P2, Tt, and T2 represent the same conditions as in FIG. 2), and a stable region can be reached without causing overshoot a or hunting b as shown in FIG.

In addition, in the above-mentioned embodiment, the injection speed control area and the mold internal pressure control area can be set in one step or in a multi-step program, and a reference pattern can be input into the pressure and speed setting inputs from the digital memory. It is also possible to trace the waveform over the entire area, use a delay circuit, etc., or input a pattern in which settings are connected with straight lines.

<Effects of the Invention> As explained above, the present invention provides an injection molding machine with a configuration in which the mold internal pressure control circuit and the hydraulic pressure control circuit are connected in a cascade using two sensors that detect the mold internal pressure and the hydraulic pressure. By adjusting , injection molding can be performed stably at high speed without causing overshoot or hunting in the waveform of the mold internal pressure.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of an injection molding machine to which the control method according to the present invention is applied, Figure 2 is a mold internal pressure waveform diagram according to the present invention, and Figures 3 and 4 are during high-speed injection using the conventional control method. It is a mold internal pressure waveform diagram. DESCRIPTION OF SYMBOLS 1... Mold, 2... Capity, 3... In-mold pressure sensor, 4... Injection cylinder, 5... Injection ram, 6
... Oil pressure sensor, 7... Speed sensor, 8... Servo amplifier for speed control, 9... Servo pulp, 10...
- Servo pulp drive amplifier, 11... Injection speed control - mold pressure control switching circuit, 12... Hydraulic servo amplifier (control circuit), 13... Servo amplifier for mold pressure (control circuit), 14...In-mold pressure setting device, 15...
Amplifier for in-mold pressure sensor, 16... Timing controller for switching between injection speed control and in-mold pressure control, 17...
・Switching pressure setting device, 18... Injection speed setting device Patent applicant Canon Co., Ltd. ~, vJ2 diagram

Claims (1)

[Claims] 1. An in-mold pressure sensor for detecting the pressure of molten resin is provided in the cavity or passage of the injection mold, and a hydraulic sensor for detecting the injection oil pressure is provided in the hydraulic circuit of the injection ram, and the detected value of the oil pressure is provided. The setting value of the circuit that controls the hydraulic pressure is changed according to the detected value of the mold internal pressure sensor and the set internal mold pressure value to adjust the injection hydraulic pressure during injection, filling, holding pressure, or filling and holding pressure. A method for controlling an injection molding machine, characterized in that: