JPH04308719A - Injection process control method and device for injection molding machine - Google Patents

Abstract

PURPOSE:To enable automatic changeover to pressure feedback control and attain an easy and reliable molding operation when an established hydraulic pressure value is attained especially even during injection speed feedback control. CONSTITUTION:In an injection process control method of an injection molding machine where injection filling closed control is performed through a control part 10 obtained by connecting a speed setting apparatus 12 and pressure setting apparatus 14 with each other by making an accumulator 24 into a hydraulic pressure source, the control method is constituted so that actual hydraulic pressure is detected during a speed feedback control, when the actual hydraulic pressure is not attained to an established hydraulic pressure value, speed feedback control is performed by an established speed value established by the foregoing speed setting apparatus 12, when the foregoing actual hydraulic pressure attains to the foregoing established hydraulic pressure value, pressure feedback control is performed by the foregoing established hydraulic pressure value.

Description

[Detailed description of the invention]

The present invention relates to an injection process control method and device for an injection molding machine, and in particular, it is possible to automatically switch to pressure feedback control even during injection speed feedback control when a set hydraulic pressure value is reached, and to easily and reliably control the injection process. This invention relates to novel improvements for achieving efficient molding operations.

0002

2. Description of the Related Art Conventionally, the method shown in FIG. 3 is generally used as a method and apparatus for controlling the injection process of this type of injection molding machine. That is, what is indicated by the reference numeral 1 in FIG. 3 is the first mold part 2 and the second mold part 3.
The mold 1 is provided with a cylinder 5 having a screw 4, and this screw 4 is connected to an injection ram 7 provided in an injection cylinder 6. has been done.

A hydraulic motor 8 is connected to the injection ram 7, and the injection cylinder 6 and the injection ram 7 constitute an injection drive section 16. , are connected to the speed comparator 11 of the control section 10 to which the speed setter 12 is connected.

The speed comparator 11 is connected to a switching device 13, and a pressure comparator 15 to which a pressure setting device 14 is connected is connected to the switching device 13. , a pressure detector 17 connected to the injection drive section 16 is connected.

An external forced speed control signal 18 and an external forced pressure control signal 19 are input to the switching device 13, and a switching output 13a of this switching device 13 is input to the controller 2.
A servo valve 21 connected to the injection drive unit 16 via 0
The controller 20 and the servo valve 21 constitute a servo main body 22.

The servo valve 21 is connected to an accumulator 24 via a switching valve 23, and this switching valve 23 is connected to a hydraulic power source 26 and a safety valve 27 via a check valve 25.

Therefore, in the injection process using the conventional injection filling closed control using the accumulator 24 as a hydraulic source, the set speed value 12a set by the speed setter 12 and the actual speed 9a from the speed detector 9 are compared to the speed comparator. 11, and feedback control is performed by the control unit 10 and a speed control circuit (not shown) so that the speed follows the set speed value 12a. During the control described above, the holding pressure switching position at which the injection process is completed is compared with a screw position detector (not shown) and a holding pressure switching position (not shown) set manually in advance. When the set position and the actual measured position coincide with the advance of the molded product, the process switches to the holding pressure process, which is a process for correcting cooling shrinkage of the molded product. In this process, the set hydraulic pressure value 14a set by the pressure setting device 14 and the actual hydraulic pressure value 17a from the pressure detector 17 are compared by the pressure comparator 15, and the hydraulic pressure is made to follow the set hydraulic pressure value 14a that has been set. Feedback control is performed by a pressure control circuit (not shown) of the control unit 19 so that

As described above, up to the manually set pressure holding switching position, speed feedback control is performed using speed and a target, and after the pressure holding switching position, pressure feedback control is performed using pressure as a target.

[0009]

[Problems to be Solved by the Invention] In the case of the above-mentioned conventional method, the injection filling hydraulic pressure may act more than normal due to some abnormality during continuous molding, such as foreign matter clogging the gate part 1A of the mold or poor gate balance. When the filling speed is attenuated by Based on this judgment, the controller 20 instructs the servo valve 21 to open more to reach the set speed value 12a. At this time, the injection filling hydraulic pressure becomes the accumulated pressure in the accumulator 24, and the molten resin in the cylinder 5 is pushed forward by the excessive hydraulic pressure and is filled into the cavity 1a of the mold 1. As a result, the cavity 1a is complicated due to clogging of the gate 1A of the mold 1 or poor gate balance, and some of the cavities 1a that are easy to enter among the multiple cavities 1a are overfilled with molten resin, resulting in overpacking and molding. Mold 1 is damaged. In addition, when starting up molding or trying out a new mold, it is necessary to set speed conditions so that the injection filling load does not become too high, requiring operators to spend time and effort setting the conditions and to operate carefully. was.

The present invention has been made to solve the above-mentioned problems. In particular, even during injection speed feedback control, when a set oil pressure value is reached, automatic switching to pressure feedback control is possible, It is an object of the present invention to provide an injection process control method and apparatus for an injection molding machine that achieves easy and reliable molding operations.

[0011]

[Means for Solving the Problems] An injection process control method for an injection molding machine according to the present invention uses an accumulator as a hydraulic pressure source and performs injection filling closed control via a control section to which a speed setting device and a pressure setting device are connected. In the injection process control method for an injection molding machine, the actual oil pressure is detected during speed feedback control, and when the actual oil pressure does not reach the set oil pressure value, the set speed value set by the speed setting device is set. In this method, speed feedback control is performed by the above-described method, and when the actual hydraulic pressure reaches the set hydraulic pressure value, pressure feedback control is performed using the set hydraulic pressure value.

The injection process control device for an injection molding machine according to the present invention includes a control section to which a pressure setting device for setting a set hydraulic pressure value during the injection process and a speed setting device for setting a set speed value during the injection process are connected. a pressure detector that detects the actual oil pressure during the injection process; a pressure comparator and a pressure control switch that compare the actual oil pressure and the set oil pressure value; and a pressure control switch that detects the actual speed during the injection process. a speed detector, a speed comparator and a speed control switch for comparing the actual speed and a set speed value, a switch connected to each of the switches, a servo valve connected to the switch, and a servo valve connected to the switch; It includes an accumulator and a hydraulic power source connected to the valve, and an injection drive unit connected to the servo valve, the pressure detector, and the speed detector, and the servo valve is controlled by speed feedback control or pressure feedback control by the switching device. The configuration is such that it can be switched to

[0013]

[Operation] In the injection process control method and device for an injection molding machine according to the present invention, even during speed feedback control, the filling oil pressure is detected at the same time, and when the detected actual oil pressure reaches the set oil pressure value, the filling oil pressure is detected at the same time. , it is possible to automatically switch from speed feedback control to pressure feedback control within the control unit even without a control state switching (velocity feedback control←→pressure feedback control) signal from an external device.

Therefore, during injection speed feedback control,
If the injection filling load hydraulic pressure increases due to some abnormality,
Since the control unit automatically switches to pressure feedback control based on the preset oil pressure value, there is no need to worry about overfilling the mold cavity with molten resin and damage to the mold, and at the same time, during continuous molding, Even when starting up molding or trying out a new mold, the hydraulic pressure does not exceed the preset value, so the operator does not have to worry about the injection/filling load hydraulic pressure and can operate with peace of mind. In addition, not only the filling speed in the injection filling process but also the filling oil pressure can be set freely, which widens the range of molding conditions and allows anyone to easily operate it.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the injection process control method and apparatus for an injection molding machine according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration, and FIG. 2 is an explanatory diagram showing the control process. What is indicated by the reference numeral 1 in FIG. 1 is a mold that is constituted by a first mold part 2 and a second mold part 3 and has a gate part 1A.
is provided with a cylinder 5 having a screw 4, which is connected to an injection ram 7 provided on an injection cylinder 6.

A hydraulic motor 8 is connected to the injection ram 7, and the injection cylinder 6 and the injection ram 7 constitute an injection drive section 16. A speed detector 9 provided on the injection drive section 16 , are connected to the speed comparator 11 of the control section 10 to which the speed setter 12 is connected.

The speed comparator 11 is connected to a switching device 13, and a pressure comparator 15 to which a pressure setting device 14 is connected is connected to the switching device 13. , a pressure detector 17 connected to the injection drive section 16 is connected.

Furthermore, the speed detector 9 and the speed setter 12 are connected to a speed control switch 30 connected to the switch 13, and the pressure detector 17 and the pressure setter 14 are
It is connected to a pressure control switch 31 which is connected to the switch 13 .

An external forced speed control signal 18 and an external forced pressure control signal 19 are input to the switching device 13, and a switching output 13a of this switching device 13 is input to the controller 2.
A servo valve 21 connected to the injection drive unit 16 via 0
The controller 20 and the servo valve 21 constitute a servo main body 22.

The servo valve 21 is connected to an accumulator 24 via a switching valve 23, and this switching valve 23 is connected to a hydraulic power source 26 and a safety valve 27 via a check valve 25.

Next, the case where injection control is actually performed in the above-described configuration will be explained. First, high oil pressure is accumulated in the accumulator 24 due to oil pressure supplied from the oil pressure source 26 . In the above-mentioned state, a signal indicating that the injection process is in progress is received from another controller system not shown in FIG. and is supplied to the cylinder chamber 6a of the injection cylinder 6. The screw 4 moves forward (to the left in the figure) under the action of the oil pressure, and the molten resin in the cylinder 5 is filled into the mold 1.

The moving speed of the screw 4 is detected by a speed detector 9.
The actual speed 9a is detected by the speed comparator 11. The speed comparator 11 compares the set speed value 12a from the speed setter 12 and the actual speed 9a from the speed detector 9, and the compared comparison signal 11a is input to the switch 13. At the same time, the speed detector 9 is also connected to the speed control switch 30.
and the actual speed 9a from the speed setter 12 and the set speed value 12a.
The speed control switch 30 also sends a control signal 30a to the switch 13.

At this time, the hydraulic pressure in the cylinder chamber 6a of the injection cylinder 6 is detected by the pressure detector 17, and the actual hydraulic pressure 15a is sent to the pressure comparator 15. This pressure comparator 15 receives a set hydraulic pressure value 14a from the pressure setting device 14.
and the actual oil pressure 17a from the pressure detector 17, and the compared comparison signal 15a is input to the switch 13. At the same time, the pressure control switch 31 also receives the actual oil pressure 17a and set oil pressure value 14a from the pressure detector 17 and pressure setting device 14.
The pressure control switch 31 also sends a control signal 31a to the switch 13.

The speed setting device 12 and the pressure setting device 14 are constructed so that the operator can set them freely. When the pressure control switch 31 determines that the actual hydraulic pressure 17a detected by the pressure detector 17 is smaller than the set hydraulic pressure value 14a set by the pressure setting device 14, the switch 13 switches to pressure control. The switching device 31 switches to the speed side, the set speed value 12a set by the speed setter 12 is input to the controller 20, and the servo valve 21 is controlled by speed feedback so that the moving speed of the screw 4 follows the set speed value 12a. , proceed with the injection filling process.

The pressure control switch 31 is the pressure setting device 14.
pressure detector 1 than the set hydraulic pressure value 14a set in
When it is determined that the actual hydraulic pressure 17a detected by the pressure control switch 31 has been reached, the switching device 13 is switched to the pressure side by the pressure control switching device 31, and the set hydraulic pressure value 14a set by the pressure setting device 14 is input to the controller 20. Then, the servo valve 21 is controlled by pressure feedback so that the hydraulic pressure in the cylinder chamber 6a of the injection cylinder 6 follows the set hydraulic pressure value 14a.

Thereafter, when the pressure control switch 31 determines that the actual hydraulic pressure 17a detected by the pressure detector 17 is again smaller than the set hydraulic pressure value 14a set by the pressure setting device 14, The switch 13 is set to the speed side by the pressure control switch 31, and performs speed feedback control on the servo valve 21.

The switch 13 can also forcibly switch between the speed side and the pressure side in response to a signal from another controller not shown in FIG. It is also possible to do this.

[0028] The above-mentioned pressure feedback control priority is advantageous for pressure holding process control which corrects cooling shrinkage of the molded product after the injection process is completed.

Note that the above-mentioned injection process control is illustrated as follows:
As shown in Fig. 2, the control state is shown when the servo valve 21 is switched to speed control and pressure control in the injection process, and the set speed value 12a and set hydraulic pressure value 14a are set at various levels, and the external maintenance At the pressure switching point, it is shown that the pressure is switched to the holding pressure control of the holding pressure process.

[0030]

Effects of the Invention The method and apparatus for controlling the injection process of an injection molding machine according to the present invention are constructed as described above, and therefore the following effects can be obtained. In other words, even during injection speed feedback control, when the set filling oil pressure, that is, the set oil pressure value, is reached, the control unit automatically switches to pressure feedback control, so during continuous molding,
When the speed decreases due to mold gate clogging, poor gate balance, mold temperature drop, etc., the molten resin is concentratedly filled into a complex cavity or several cavities out of multiple cavities due to the accumulated pressure in the accumulator. There is no need to worry about mold damage, and at the same time, there is no need to worry about the filling load hydraulic pressure when starting up molding or trying out a new mold, making it easy for both experienced molding workers and amateur workers. Molding operations can be performed quickly and with peace of mind. Moreover, for this purpose, automated operation of injection molding can be realized.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a method and apparatus for controlling an injection process of an injection molding machine according to the present invention.

FIG. 2 is an explanatory diagram showing a control process.

FIG. 3 is a block diagram showing a conventional injection process control method and apparatus for an injection molding machine.

[Explanation of symbols]

9 Speed detector 9a Actual speed 10 Control section 11 Speed comparator 12 Speed setting device 12a　　　　　set speed value 13 Switcher 14 Pressure setting device 14a Set hydraulic pressure value 15 Pressure comparator 17 Pressure detector 17a Actual oil pressure 21 Servo delivery 24 Accumulator 26 Hydraulic source 30 Speed control switch 31 Pressure control switch

Claims (2)

[Claims] Claim 1: An injection molding machine that uses an accumulator (24) as a hydraulic pressure source and performs injection filling closed control via a control unit (10) to which a speed setting device (12) and a pressure setting device (14) are connected. In the injection process control method, the actual hydraulic pressure is detected during speed feedback control, and when the actual hydraulic pressure (17a) does not reach the set hydraulic pressure value (14a), the speed setting device (12) sets the actual hydraulic pressure (17a). set speed value (
12a), and when the actual hydraulic pressure (17a) reaches the set hydraulic pressure value (14a), pressure feedback control is performed according to the set hydraulic pressure value (14a). Injection process control method for injection molding machine. [Claim 2] Set hydraulic pressure value during injection process (14a)
A control unit (10) connected to a pressure setting device (14) for setting a pressure setting device (14) and a speed setting device (12) for setting a set speed value (12a) during the injection process;
17a), a pressure comparator (15) and a pressure control switch (31) that compare the actual hydraulic pressure (9a) and the set hydraulic pressure value (14a), and the injection process a speed detector (9) that detects the actual speed (9a) inside, a speed comparator (11) and a speed control switch (30) that compare the actual speed (9a) and the set speed value (12a);
A switching device (13) to which each of the switching devices (30, 31) is connected
), and a servo valve (21) connected to the switching device (13).
), an accumulator (24) and a hydraulic power source (26) connected to the servo valve (21), and the servo valve (21).
), the pressure detector (17) and the speed detector (9)
an injection drive unit (16) connected to an injection molding machine, wherein the servo valve (21) is switched to speed feedback control or pressure feedback control by the switching device (13). Process control equipment.