JPH0577300A - Pressure filling controlling device of injection molding machine - Google Patents

Abstract

PURPOSE:To improve accuracy in the shape of a molded item. CONSTITUTION:When a pressure filling mode is selected (S1), actual filling pressure command value X actual injection speed = constant is set (S2) and filling pressure limit set value is set (S3), a speed control is performed by V=a/P (S4) to decide actual filling pressure >= filling pressure limit value or NO (S5). If actual filling pressure < filling pressure limit value, S4 is repeated, and if actual filling pressure >= filling pressure limit value, a pressure filling control is performed (S6). Next, V-P changeover position or NO is decided (S7) and if NO, S6 is repeated and if YES, a dwelling control is carried out (S8). If a speed filling mode is selected (S1), a speed control is performed using a set value (S9), and whether it is V-P changeover position is decided (S10). If NO, S9 is repeated and if YES, a dwelling control is performed (S8).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric injection molding machine, and more particularly to a pressure filling control device for an injection molding machine suitable for controlling an injection process.

[0002]

2. Description of the Related Art Conventionally, an injection molding machine injects measured, melted, and kneaded resin into a mold at a high pressure with an injection screw, so that an internal pressure orientation is generated in a molded article, and the internal orientation becomes a residual stress. Since it is released during the cooling process of the molded product, cooling distortion may occur and the molded product may be warped. That is, during resin filling, the filling pressure gradually increases as the resistance inside the mold increases, and when the filling is completed, a peak pressure is generated, and as a result, high pressure acts in the cavity and this remains as internal stress. After that, it is released with cooling and appears as a sled.

Therefore, as described in, for example, Japanese Patent Laid-Open No. 178014/1990, a speed process / filling process in an injection process is performed.
Control so that the pressure-holding process is switched according to the filling state of the raw material resin, or the filling resistance of the molten resin at the time of switching from the filling process to the pressure-holding process as described in JP-A-62-207622, for example. An electric injection molding machine and a hydraulic injection molding machine have been developed aiming at improving the shape accuracy of a molded product, such as control to reduce the injection speed.
In this case, as a general hydraulic injection molding machine, for example, as shown in FIG. 7, a hopper 1, a heating cylinder 2, an injection screw 3, an oil motor 4, an injection cylinder 5, a position sensor 6,
A pressure sensor 7, a supply solenoid valve 8, an injection solenoid valve 9, a flow rate proportional valve 10, a pressure proportional valve 11, a control device 15 having an input / output unit 12, a sequence controller 13 and a process controller 14, and a setting / display device 16 were provided. There is something.

[0004]

However, the conventional injection molding machine as described above has the following problems.
In the case of a hydraulic injection molding machine, due to the characteristics of hydraulic control,
There is a characteristic that the injection speed becomes slow when the value is close to the value set as the filling pressure, and this may bring about a good result in the shape accuracy of the molded product. On the other hand, in the case of an electric injection molding machine, injection molding is performed by controlling the injection speed and the injection pressure so that the injection speed and injection pressure are as specified. However, depending on the type of molded product, it corresponds to the mold internal pressure. By changing the injection speed, the surface finish and shape accuracy of the molded product are improved. However, the conventional electric injection molding machine has a problem that the control for improving the shape accuracy of the molded product has not been realized regardless of the type of the molded product. The development of an electric injection molding machine capable of manufacturing

The present invention has been made to solve the above-mentioned problems. The injection molding achieves an improvement in the shape accuracy of a molded product by performing control such that the injection speed is reduced as the actual filling pressure approaches the filling pressure limit value. An object is to provide a pressure filling control device for a machine.

[0006]

The present invention comprises an injection screw for filling a mold with molten resin, an injection motor for driving the injection screw, and a pressure sensor for detecting the actual filling pressure. In the injection molding machine, the setting means for setting a filling pressure limit value and an arbitrary value with which the product of the actual filling pressure and the actual injection speed is constant, and the actual filling pressure detected by the pressure sensor in the filling step, Speed control means for controlling the injection speed so that the product of the actual injection speed and the constant value set by the setting means, an actual filling pressure detected by the pressure sensor in the filling step and a filling pressure set by the setting means A pressure control means for judging the magnitude of the limit value and performing the filling control while canceling the speed control and holding the pressure constant when it is judged that the actual filling pressure has reached the filling pressure limit value. The features. Further, the present invention determines whether the actual filling pressure detected by the pressure sensor in the filling step and the filling pressure limit value set by the setting means are large or small, and the actual filling pressure reaches the filling pressure limit value. When the determination is made, the function of performing the filling control while releasing the speed control and keeping the pressure constant can be selected by the selection means.

[0007]

According to the present invention, in the filling step in injection molding, the injection speed is controlled so that the product of the actual filling pressure and the actual injection speed becomes a constant value, and the actual filling pressure becomes the filling pressure limit value. When it reaches, the speed control is released, and the filling control is performed while maintaining the pressure at a constant state. As a result, it becomes possible to improve the shape accuracy of the molded product as compared with the conventional case.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing an injection screw drive mechanism and a control system of an electric injection molding machine according to this embodiment. The injection screw drive mechanism is a heating cylinder 21 for heating and melting resin supplied from a hopper, and the heating cylinder 21. An injection screw 22 which is arranged inside and applies pressure to the molten resin by moving in the axial direction of the heating cylinder, a pressure sensor (load cell) 23 which is arranged at the rear end of the injection screw 22 and detects the filling pressure, and an injection screw drive Ball screw 24.2 mounted on the mechanism
4. Pulley 25.2 attached to the end of the ball screw
5. Servo motor 2 for driving the injection screw 22
6, a belt 27 wound around the output shaft of the servo motor 26 and the pulley 25, and a pulse generator 28 for detecting the rotation speed of the servo motor 26.

On the other hand, the control system of the electric injection molding machine is configured to include a setting section 29, a controller 30, and an AC servo amplifier 31. From the setting unit 29, the filling pressure limit set value S1, the actual filling pressure command value × the actual injection speed (=
a (constant) set value S2, speed set value S3, holding pressure set value S4, V → P switch position set value S5 (P: actual filling pressure,
V: actual injection speed) is set. The controller 30 includes a comparator 32, a pressure filling controller 33, a V = a / P controller 34, a speed controller 35, a pressure controller 36, a comparator 37, a speed → position converter 38, and a sequence unit 39. , A switching contact 40, a switching contact 41, and a switching contact 42. The comparator 32 is
The filling pressure limit set value set by the setting unit 29 is compared with the actual filling pressure output from the pressure sensor 23, and a switching signal is output when the actual filling pressure ≧ filling pressure limit setting value. .. The pressure filling controller 33 includes a filling pressure limit set value set by the setting unit 29 and the pressure sensor 2.
A pressure filling control signal is output based on the actual filling pressure output from 3. The V = a / P controller 34 uses the actual filling pressure command value set from the setting unit 29 ×
Based on the actual injection speed (= a set value) and the actual filling pressure P output from the pressure sensor 23, the injection speed control signal V calculated by the formula V = a / P is output. The speed controller 35 outputs a speed control signal based on the speed set value set by the setting unit 29 and the speed pulse output from the pulse generator 28. The pressure controller 36 outputs a holding pressure control signal based on the holding pressure set value set by the setting unit 29 and the actual filling pressure output by the pressure sensor 23. The comparator 37 uses the V set by the setting unit 29.
The V → P switching position signal is output based on the → P switching position set value and the position pulse converted by the speed → position converter 38 from the speed pulse from the pulse generator 28. The sequence unit 39 outputs a switching signal corresponding to the pressure filling mode in accordance with the operation / operation signal from the input / output unit (limit switch, lamp, push button, etc.) 43.

Further, the switching contact 40 is outputted from the pressure filling control signal outputted from the pressure filling controller 33 or the V = a / P controller 34 based on the switching signal outputted from the comparator 32. One of the injection speed control signals V is selectively output to the switching contact 41.
The switching contact 41 is one of a signal output from the switching contact 40 and a speed control signal output from the speed controller 35, based on the switching signal corresponding to the pressure filling mode output from the sequence unit 39. Switch contact 42
Selective output to. The switching contact 42
Is a signal output from the switching contact 41 or a pressure control signal output from the pressure controller 36 to the AC servo amplifier 31 based on the V → P switching position signal output from the comparator 37. It is designed to output selectively. The AC servo amplifier 31 outputs a speed command to the servo motor 26 based on the signal output from the switching contact 42.

The control of the AC servo amplifier 31 will be described below. When the position command value is output to the position command unit 45 of the AC servo amplifier 31 by the control of the sequence program / servo program based on the output of the pressure sensor 23 from the controller 30, the position command unit 45 outputs the movement amount to the deviation counter 46. It is designed to output. The deviation counter 46 calculates the movement amount output from the position command unit 45,
The droop pulse of the servo motor 26 is output to the speed command point 47 based on the position feedback value output from the pulse generator 28 via the speed → position converter 50. At the speed command point 47, the accumulated pulse output from the deviation counter 46 and the pulse generator 2
The speed command is output to the servo motor 26 via the servo amplifier unit 49 based on the speed feedback value output from the control unit 8 via the interface unit 48. Further, the controller 30 includes an operation panel 51 having a changeover switch for setting the pressure filling mode or the speed filling mode, and a CRT 5 for displaying various data.
2. A printer 53 for printing various data is connected.

FIG. 2 shows injection speed / injection pressure waveforms at the time of general standard molding. In the electric injection molding machine, the speed mode and the pressure holding mode are clearly controlled, and in the hydraulic injection molding machine. The hydraulic pressure setting during filling is set high so that the injection speed is the set value (A in the figure). Further, FIG. 3 shows injection speed / injection pressure waveforms at the time of molding when the hydraulic pressure setting during filling is set lower in the hydraulic injection molding machine, which has characteristics peculiar to the hydraulic system. When the hydraulic pressure setting of B is set to a value shown by B in the figure, the characteristic that the injection speed decreases as the actual injection pressure approaches the set value may act in the direction of improving the shape accuracy of the molded product.
The electric injection molding machine of this embodiment is characterized in that it has characteristics close to those shown in FIG. 3 in order to improve the shape accuracy of the molded product. In this case, the electric injection molding machine is generally controlled to operate at the set speed in the speed control mode, and the injection speed does not change even if the mold internal pressure (injection resistance) changes as the resin is filled. Since, for example, the injection speed is maintained by increasing the drive current of the servo motor when the mold internal pressure rises, it is normally performed as shown in FIG.
The characteristics as shown in FIG. 2 cannot be obtained, resulting in the characteristics shown in FIG. Therefore, in order to obtain the characteristics of FIG. 3, the filling pressure limit value can be set to an arbitrary value so that when the filling pressure limit value is reached during filling, the injection speed control mode changes to the injection pressure control mode. It suffices to perform switching control and perform filling at a constant pressure. By the way, since the injection speed is accurately protected by the filling pressure limit value only by the mode switching control, the pressure at the time of rising the injection pressure / shifting to the injection pressure control mode becomes extremely sharp and adversely affects the shape accuracy of the molded product. May be affected. Therefore, in the electric injection molding machine of the present embodiment, in order to improve the above points, an arbitrary value is set so that the actual filling pressure × the actual injection speed is constant, and the injection is performed while detecting the actual filling pressure. If the speed is controlled, the injection speed will decrease with the increase of the filling pressure, so that the characteristics close to those of FIG. 3 are obtained.

Next, the pressure filling control process of the electric injection molding machine of the present embodiment having the above-mentioned configuration will be described with reference to FIG.
The operator selects either the pressure filling mode or the velocity filling mode by operating the changeover switch on the operation panel of the injection molding machine (step S1). When the pressure filling mode is selected, steps S2 → S3 → S4 → S5 → S6 →
While the process from S7 to S8 is performed, when the speed filling mode is selected, the process from step S9 to S10 to S8 is performed. First, when the pressure filling mode is selected in step S1, the setting unit 29 displays “actual filling pressure command value ×
The actual injection speed = constant value ”(a = P × V) is set in the controller 3
While setting and inputting 0 to the controller 30 (step S2), the filling pressure limit setting value is set and inputting to the controller 30 (step S3). As a result, the following filling control / pressure holding control is started. That is, the controller 30 performs speed control with V represented by the equation V = a / P (step S4), and then determines whether or not the relationship of actual filling pressure ≧ filling pressure limit value is satisfied (step S4). S5), if it is determined that the actual filling pressure <the filling pressure limit value, the process returns to step S4 and the speed control is performed at V = a / P, while if it is determined that the relationship of the actual filling pressure ≧ the filling pressure limit value is established. Pressure filling control is performed (step S6). Next, the controller 30 determines whether or not it is the filling-holding pressure switching position (step S7), and if it is determined not to be the filling-holding pressure switching position, the process returns to step S6 to perform pressure filling control, while filling-holding pressure is performed. When it is determined to be the switching position, pressure holding control is performed. On the other hand, when the speed filling mode is selected in step S1, the controller 30 performs speed control with the set value (step S9), and then the filling-
It is determined whether or not it is the holding pressure switching position (step S10), and if it is determined that it is not the filling-pressure holding switching position, the above step S
Returning to step 9, speed control is performed with the set value, while pressure holding control is performed when it is determined to be the filling-pressure holding switching position (step S
8).

[0014]

As described above, according to the present invention, the effects of the following items can be obtained. The electric injection molding machine of the present invention has a control characteristic that the injection speed decreases as the actual filling pressure approaches the filling pressure limit value. It is possible to manufacture a molded product having improved properties. As described above, it is possible to accurately cope with the production of various types of molded products and to significantly improve the performance of the injection molding machine.

[Brief description of drawings]

FIG. 1 is a block diagram of an injection screw drive mechanism and a control system of an electric injection molding machine according to an embodiment of the present invention.

FIG. 2 is a general injection speed / injection pressure waveform diagram during standard molding.

FIG. 3 is an injection speed / injection pressure waveform diagram during MIRS molding.

FIG. 4 is a flowchart of a pressure filling control process of this embodiment.

FIG. 5 is a block diagram of a general hydraulic injection molding machine.

[Explanation of symbols]

 21 injection screw 23 pressure sensor 26 servo motor (injection motor) 29 setting unit (setting means, selection means) 30 controller (speed control means, pressure control means) 31 AC servo amplifier

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[Procedure amendment]

[Submission date] July 25, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Fig. 3] Injection speed when the filling hydraulic pressure is set low
It is an injection velocity waveform chart.

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

Claims (2)

[Claims] 1. An injection screw for filling a mold with molten resin, and an injection motor for driving the injection screw,
In an injection molding machine comprising a pressure sensor for detecting an actual filling pressure, a setting means for setting a filling pressure limit value and an arbitrary value at which the product of the actual filling pressure and the actual injection speed is constant, Speed control means for controlling the injection speed so that the product of the actual filling pressure detected by the pressure sensor in the filling step and the actual injection speed becomes a constant value set by the setting means, and detected by the pressure sensor in the filling step The actual filling pressure and the filling pressure limit value set by the setting means are judged to be larger or smaller, and when it is judged that the actual filling pressure reaches the filling pressure limit value, the speed control is released and the pressure is kept constant. A pressure filling control device for an injection molding machine, comprising: a pressure control means for performing filling control. 2. The size of the actual filling pressure detected by the pressure sensor in the filling step and the filling pressure limit value set by the setting means is determined, and it is determined that the actual filling pressure has reached the filling pressure limit value. 2. The pressure filling control device for an injection molding machine according to claim 1, wherein the function of performing the filling control while releasing the speed control and keeping the pressure constant when the above is possible is selectable by the selecting means.