JPH07304079A - Control device of injection molding machine - Google Patents

Abstract

PURPOSE:To automatically obtain the good waveform of injection speed suppressed in the overshoot or undershoot of filling pressure. CONSTITUTION:The filling pressure during the filling of an injection device 2 is detected by a pressure detection part 12 and the pressure achieving ratio to a preliminarily inputted holding pressure value of the filling pressure and pressure change quantity are calculated by a pressure operation part 13. On the basis of the pressure achieving ratio and the pressure change quantity, a speed alteration ratio is calculated using fuzzy inference in an inference part 15 and, further, an injection speed command value is calculated on the basis of the speed alteration ratio and the preliminarily inputted held speed value in a speed operation part 16. A control valve 3 is controlled on the basis of this speed command value to control injection speed. By the control of this control device 1, a sudden pressure change is suppressed at the time of the transfer from speed control to pressure control and the good waveform of injection speed suppressed in the overshoot or undershoot of filling pressure is automatically obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a controller for an injection molding machine which controls an injection speed during filling and controls a filling pressure after completion of filling.

[0002]

2. Description of the Related Art The injection process by an injection molding machine is roughly classified into a filling process of filling a resin in a mold and a dimensional accuracy of a molded product, that is, transferability, by applying a holding pressure after completion of the filling. There is a packing process.

The flow rate, injection speed, and filling pressure in the filling process are influenced by the shape of the gate, the viscosity of the resin, the temperature of the mold, etc., and are not in a proportional relationship. Regarding the flow rate, the injection speed, and the filling pressure in the pressure holding process, the pressure changes in proportion to the change in the flow rate, but the speed hardly occurs.

For example, as shown in the waveform diagram of FIG. 5 (a), at the start of filling, the pressure is low and the speed is controlled by the controller so that the holding speed value is set in advance, and the filling is approached. And the pressure rises sharply. When the pressure reaches a preset holding pressure, the pressure is controlled by the control device so as to reach the holding pressure.

The above-mentioned velocity waveform and pressure waveform greatly change depending on the holding velocity value and holding pressure value set at the beginning, the shape of the gate, the viscosity of the resin, the temperature of the mold, etc., and appropriate injection control is performed. If this is not done, as shown in FIG. 5A, the pressure will overshoot and burr will be generated on the molded product when the speed control is switched to the pressure control. Alternatively, as shown in the waveform diagram of FIG.
If the pressure reaches the holding pressure value before the completion of filling, the speed is rapidly reduced due to the transition to pressure control at that point, the pressure undershoots, and a short shot (insufficient filling) occurs in the molded product. It causes it to occur.

Therefore, conventionally, in order to prevent such overshooting and undershooting of the pressure, a skilled worker must check the type of molded product, the mold shape, the type of gate,
Considering the resin to be used, determine the injection conditions such as holding pressure value, holding speed value, and measured value, and the injection speed waveform during filling based on past experience, and set those values in the control device. I was controlling it. In order to determine such injection conditions and the injection speed waveform during filling, a skilled worker performs test molding and confirms the molded product and the speed waveform and pressure waveform displayed on the display of the control device. Then, the quality is judged and the injection condition and the injection speed value are changed. Then, this process is repeated many times to determine each best value.

[0007]

As described above, in the control device of the conventional injection molding machine, by repeating the test molding a large number of times, the injection speed can be controlled so as not to cause overshoot or undershoot of the filling pressure. The waveform has to be determined and set, which takes a considerable amount of time even for a skilled worker, and is a very difficult work for an inexperienced worker.

The present invention has been proposed in order to solve such a problem, and controls an injection molding machine capable of automatically obtaining a favorable injection speed waveform while suppressing overshoot and undershoot of the filling pressure. The purpose is to provide a device.

[0009]

A control device (1) according to the present invention is an injection condition input means for inputting a holding speed value to be held at the start of filling and a holding pressure value to be held after completion of filling. (7, 10), injection condition storage means (11) for storing the holding speed value and the holding pressure value input by the injection condition input means, and pressure detection for detecting the filling pressure during filling of the injection device. Means (12), and a pressure achievement rate of the filling pressure value by the pressure detecting means with respect to the holding pressure value at a predetermined sampling time,
A pressure calculation means (13) for calculating a pressure change amount, and a speed change rate calculation means (15) for calculating an injection speed change rate based on the pressure achievement rate and the pressure change amount by the pressure calculation means. A speed calculation means (1) for calculating an injection speed command value based on the injection speed change rate by the speed change rate calculation means and the stored storage speed value by the injection condition storage means.
6) and the speed control means (3, 5, 1) for controlling the injection speed based on the injection speed command value by the injection speed calculation means.
7) and.

[0010]

In the control device (1) having the above structure, the filling pressure is monitored by the pressure detecting means (12) even during filling, and the pressure achievement ratio of the filling pressure to the holding pressure value by the pressure calculating means (13). Since the injection speed is changed by the speed change rate calculation means (15), the speed calculation means (16) and the speed control means (3, 5, 17) based on the pressure change amount and the pressure change amount, the speed control is changed to the pressure control. A sudden pressure change is suppressed at the time of transition. Therefore, a waveform with a good injection speed can be automatically obtained without overshooting or undershooting the pressure.

The reference numerals in parentheses are for the purpose of comparison with the drawings, and do not limit the structure of the present invention.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an entire injection molding machine equipped with a control device according to the present invention.

As shown in the figure, the control device 1 electrically controls the injection speed and the filling pressure of an injection device 2 such as a screw pre-plastic type via a control valve (speed control means) 3. The control valve 3 controls the injection speed and the filling pressure by adjusting the flow rate of oil from a hydraulic unit (speed control means) 5 that drives a plunger (not shown) in the injection device 2. is there. The hydraulic unit 5 is also a drive source of the mold clamping device 6.

The control device 1 includes a keyboard (injection condition input means) 7 for inputting injection conditions and a display (display means) for displaying the input injection conditions, injection speed waveforms, filling pressure waveforms, and the like. 9 and an NC power source (injection condition input means) 10 which is a main control unit, and an inter-NC input / output section (injection condition storage means) 11 having a memory function and a filling pressure during filling of the injection device 2. A pressure detection unit (pressure detection unit) 12 having a sample hold amplifier and an A / D converter for detection, a pressure calculation unit (pressure calculation unit) 13 for calculating a pressure achievement rate and a pressure change amount, which will be described later, and calculation thereof. An inference unit (speed change rate calculation means) 15 for calculating an injection speed change rate based on the calculated pressure achievement rate and pressure change amount, the calculated injection speed change rate, and the stored injection rate. A speed calculator (speed calculator) 16 for calculating a speed command value based on the speed value, and a control command having a D / A converter for controlling the injection speed during filling based on the calculated speed command value. An output unit (speed control means) 17 is provided. Further, a pressure control unit 19 for converting the pressure command value for controlling the filling pressure after completion of the filling from the holding pressure value stored in the NC input / output unit 11 and sending it to the control command output unit 17 is provided. ing. Based on the pressure command value from the pressure control unit 19, the control command output unit 17 also controls the filling pressure after the completion of filling.

In addition, the injection device 2 is provided with a rotary encoder 20 for detecting the injection speed, and a signal from the encoder 20 is sent to the NC power source 10.

Next, the control operation of the control device 1 having the above configuration will be described with reference to the flowcharts of FIGS. 1 and 2.

In performing the control, the NC power source 10
Injecting the holding speed value to be held at the start of filling, the holding pressure value to be held after the completion of filling, the holding pressure time, the type of resin, the type of mold, the type of gate, etc. from the keyboard 7 in advance by the operator. A condition is input, and each condition value is stored in the NC inter-input / output unit 11 and displayed on the display 9. The NC power source 10 functions as an interface for injection conditions and at the same time performs mold opening / closing control, temperature control, I / O processing, waveform processing, and the like.

When the control is started at the same time as the start of filling, the pressure calculation unit 13 first causes the predetermined sampling time (1 to 10).
Every 0 msec), the holding pressure value stored in the NC input / output unit 11 is loaded, and the filling pressure value detected by the pressure detection unit 12 and A / D converted is loaded (S).
1, 2). Then, the pressure calculation unit 13 calculates the pressure achievement rate Prat and the pressure change amount Pdval from the holding pressure value Pset and the filling pressure value Pral that have been taken in (S3, 4).

As for the pressure achievement rate Prat, the filling pressure value Pral, which is the pressure currently being injected, is determined by the holding pressure value Pset.
It is expressed by the ratio of Pat = Pral / Pset × 100 (1), and is obtained by the equation (1).

The pressure change amount Pdval indicates how much the pressure change is within the sampling time from the filling pressure value Pral currently being injected and the filling pressure value Pold at the previous sampling. Then, Pdval = K (Pral-Pold) (2) K: coefficient. The filling pressure value Pral currently being injected and the filling pressure value Pold at the immediately preceding sampling are stored in the memory area of the pressure detection unit 12 and updated every sampling.

Subsequently, the inference unit 15 calculates the speed change rate Vdrat based on the pressure achievement rate Prat and the pressure change amount Pdval calculated by the pressure calculation section 13 as described above. In the case of the present embodiment, the inference unit 15 calculates the speed change rate Vdrat as follows according to the type of resin, the type of mold, and the type of gate stored in the NC input / output unit 11 in advance. Calculate using fuzzy reasoning (S5-
7).

In FIG. 3A, four areas PB, PS, N
Membership function of pressure achievement rate (%) divided into S and NB, membership function of pressure change amount (kg / msec) divided into four regions PB, PS, NS, and NB in FIG. 3 (c) has five areas PB, PS, Z, NS,
The membership function of the speed change rate (%) divided into NBs is shown. The ten rules are shown below.

1. If the pressure achievement rate is PB, or the pressure change amount is PB, the speed change rate is PB.

2. If the pressure achievement rate is PS and the pressure change amount is PS, the speed change rate is PS.

3. If the pressure achievement rate is PS and the pressure change amount is NS, the speed change rate is Z.

4. If the pressure achievement rate is PS and the pressure change amount is NB, the speed change rate is NS.

5. If the pressure achievement rate is NS and the pressure change amount is PS, the speed change rate is Z.

6. If the pressure achievement rate is NS and the pressure change amount is NS, the speed change rate is NS.

7. If the pressure achievement rate is NS and the pressure change amount is NB, the speed change rate is NB.

8. If the pressure achievement rate is NB and the pressure change amount is PS, the speed change rate is NS.

9. If the pressure achievement rate is NB and the pressure change amount is NS, the speed change rate is NB. 10. If the pressure achievement rate is NB and the pressure change amount is NB, the speed change rate is NB.

In the above rule, for example, rule 1 means that "the rate of achievement of pressure is low, so the state may be the same as it is when the rate of change of pressure is low, so there is almost no need to change the speed." Is. Rule 6 states, "When the achievement rate of pressure is quite high and the amount of change in pressure is also large,
Change the speed considerably. "

Depending on the type of resin, the type of mold, and the type of gate, optimal inference cannot be performed with only one type of membership function and rule, so the membership function and rule for inference are used in advance. A plurality of and are stored in the memory area of the inference unit 15, and optimal inference can be performed by switching the membership function and rule according to the type of resin, the type of mold, and the type of gate. To do.

Subsequently, the speed calculation unit 16 calculates the speed change rate Vdrat calculated by the inference unit 15 as described above and N
The holding speed value Vs stored in advance in the C input / output unit 11
The speed command value Vcot is calculated based on et and (S
8). This speed command value Vcot is obtained by the equation (3) of Vcot = Vset- (Vset * Vdrat / 100) (3).

The control command output unit 17 D / A converts the speed command value calculated by the speed calculation unit 16 into a speed command voltage until the filling pressure reaches the holding pressure value. Output to the control valve 3 (S9, 1
0). This controls the injection speed. That is, the control valve 3 controls the injection speed of the injection device 2 by adjusting the flow rate of the oil sent from the hydraulic unit 6 according to the speed command voltage.

After the filling pressure reaches the holding pressure value and the filling is completed by such control of the injection speed, the pressure control unit 1
9 sends the pressure command value converted from the holding pressure value to the control command output unit 17, and the control command output unit 17 D / A converts the pressure command value into a pressure command voltage and outputs it to the control valve 3. Thereby, the filling pressure is controlled and maintained at the holding pressure value.

As described above, in the control device 1, the filling pressure is monitored also in the control of the injection speed during filling, and based on the pressure achievement rate of the filling pressure with respect to the holding pressure value and the pressure change amount. Since the injection speed is changed, even if the preset holding speed value and holding pressure value are not optimal, a rapid pressure change can be suppressed when the speed control is switched to the pressure control.

Therefore, for example, as shown in the waveform diagram of FIG. 4, a waveform having a good injection speed without overshooting or undershooting the pressure is automatically obtained. The waveform of the injection speed and the waveform of the filling pressure are displayed on the display 9 so that the operator can confirm.

In this embodiment, the speed change rate is calculated by using the fuzzy inference, but the pressure achievement rate P calculated by the equations (1) and (2) is used without using the fuzzy inference.
A preset speed change rate may be selected according to the rat and the pressure change amount Pdval.

[0041]

As described above, according to the control device of the present invention, it is possible to automatically obtain a favorable injection speed waveform in which the overshoot and undershoot of the filling pressure are suppressed. Even if it is not an operator, it is possible to easily carry out injection molding without causing burrs or short shots in a molded product in a short time.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of an entire injection molding machine including a control device according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a control operation of the control device.

FIG. 3 is a diagram illustrating fuzzy reasoning used in the control device, in which (a) is a membership function of pressure achievement rate,
(B) shows the membership function of the pressure change amount, and (c) shows the membership function of the speed change rate.

FIG. 4 is a waveform chart showing an example of a waveform of an injection speed and a waveform of a filling pressure obtained by the control of the control device.

5A and 5B are waveform charts showing examples of a waveform of an injection speed and a waveform of a filling pressure under the control of a conventional control device.

[Explanation of symbols]

 1 Control Device 2 Injection Device 3 Control Valve (Speed Control Means) 5 Hydraulic Unit (Speed Control Means) 7 Keyboard (Injection Condition Input Means) 9 Display (Display Means) 10 NC Power Supply (Injection Condition Input Means) 11 NC Input / Output Unit (injection condition storage unit) 12 pressure detection unit (pressure detection unit) 13 pressure calculation unit (pressure calculation unit) 15 inference unit (speed change rate calculation unit) 16 speed calculation unit (speed calculation unit) 17 control command output unit ( Speed control means)

Claims (4)

[Claims] 1. A control device for an injection molding machine, which controls an injection speed of an injection device in an injection molding machine during filling, and controls a filling pressure of the injection device after completion of filling. Injection condition input means for inputting a speed value, a holding pressure value to be held after completion of filling, a resin type, a mold type, and a gate type, and the holding condition input by the injection condition input means. Injection condition storage means for storing a velocity value and a holding pressure value, a pressure detection means for detecting a filling pressure during filling of the injection device, and a filling pressure value by the pressure detection means for each predetermined sampling time, Pressure calculation means for calculating a pressure achievement rate and a pressure change amount with respect to the holding pressure value, and an injection speed change rate is calculated based on the pressure achievement rate and the pressure change amount by the pressure calculation means. Degree change rate calculation means, a speed calculation means for calculating an injection speed command value based on the injection speed change rate by the speed change rate calculation means, and a memory holding speed value by the injection condition storage means, and the injection speed calculation A control device for an injection molding machine, comprising: speed control means for controlling an injection speed based on an injection speed command value by the means. 2. The control device for an injection molding machine according to claim 1, wherein the speed change rate calculation means calculates the injection speed change rate using fuzzy inference. 3. The control device for an injection molding machine according to claim 2, wherein the speed change rate calculation means switches the fuzzy inference according to the type of resin, the type of mold, and the type of gate. 4. The control device for an injection molding machine according to claim 1, further comprising display means for displaying a waveform of injection speed and a waveform of filling pressure.