JPH08281747A - Method and apparatus for controlling mold clamping of injection molding machine - Google Patents

Abstract

PURPOSE: To accurately and precisely control a mold clamping force by directly calculating the present mold clamping force, comparing it with a target set mold clamping force, and so closed-controlling a cross head position that the detected force coincides with the set force. CONSTITUTION: When a mold closing step is finished by the touch of a mold, the present mold clamping force is calculated from the detected strain amount of a strain sensor 114 mounted at a die bar 104 in the mold clamping step from a mold touching position 108b to a mold clamping complete position 108c, and compared with the set mold clamping force previously set to a setter 111. When the detected force is smaller than the set force, a controller 110 is instructed to advance a cross head 105. When the detected force is larger, the controller 110 is instructed to retract the head 105. Thus, the set force is brought into coincidence with the detected force by a closed control, and the set time is maintained. Accordingly, since the closed control is the actually generated force to be fed back, the force generated as set is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold clamping control method and a mold clamping control device for an injection molding machine.

[0002]

2. Description of the Related Art FIG. 3 is a front view and a control block diagram showing a structure of a toggle type mold clamping device of a conventional injection molding machine.
Shown in 301a is a fixed mold, 301b is a movable mold, 3
Reference numeral 02 denotes a fixed plate that holds the fixed mold 301a, 303 denotes a movable plate that holds the movable mold 301b, and 304 denotes a fixed plate 30.
2 is a tie bar that connects and fixes the mold clamping housing 306 and guides the movable plate 303 slidably, 305 is a crosshead fixed to the movable part of the drive device 307,
Reference numeral 06 is a mold clamping housing, 307 is a mold clamping housing 306.
Is a drive device in which the tip of the movable portion is fixed to the crosshead 305, and 308 is a toggle mechanism whose tip portion is rotatably connected to each of the movable platen 303, the crosshead 305, and the mold clamping housing 306, and 309 is a direct , Or from the position of the crosshead 305, or the drive device 30
7 is a position detection device that detects the position of the movable platen 303 from the rotation angle of the drive motor 7.

In the figure, reference numeral 308a indicates a mold opening position, 308b a mold touching position, and 308c a mold clamping completion position. When the cross head 305 is moved forward by the driving device 307, the movable platen 303 to which the movable mold 301b is fixed by the operation of the toggle mechanism is at a high speed in the initial stage, and the speed decreases and the mold clamping pressure increases as the completion of mold clamping approaches. Move forward, fixed mold 301a
Clamp to and clamp.

The conventional mold clamping control device stores a control device 310 for controlling the drive of the drive device 307, a setter 311 for setting the forward speed and the switching position, a geometrical positional relationship between the cross head 305 and the movable platen 303. Memory 31
2 and a comparator 313 that compares the position of the crosshead 305 detected by the position detection device 309 with the setting value of the setting device 311 and issues a switching signal to the control device 310.

From the mold opening position 308a to the mold touch position 30
During the mold closing process up to 8b, the comparator 313 controls the switching signal while comparing the position of the crosshead 305 detected by the position detection device 309 with the switching position such as the forward speed set in the setting device 311. Command the device 310,
The control device controls the drive device by the instruction of the comparator 313 to move the crosshead 305 forward.

In the mold clamping process from the mold touch position 308b to the mold clamping completion position 308c, the relationship between the crosshead position and the mold clamping force changes as shown in the graph of FIG. Comparator 313
Cross head 3 detected by the position detection device 309 at
A storage device 312 storing the relationship of FIG. 4 from the position of 05.
The cross-head 305 which has calculated the mold clamping force by and reached the mold clamping force corresponding to the set mold clamping force set by the setter 311.
At the position, the mold clamping completion signal is transmitted to the control device 310, and the control device performs open control to stop the drive device in accordance with the mold clamping completion signal.

Further, as disclosed in Japanese Patent Laid-Open No. 63-116820, as a method for obtaining an injection-molded article with high accuracy, molten resin is injected into the cavity of the mold with the mold slightly opened, Next, there is also a method of obtaining a molded product having the shape of the mold cavity by tightening the mold, but in this case also, the mold is stopped by the above-described control method at the crosshead 205 position corresponding to the slightly opened state, After injection of the molten resin, open control is performed to advance the crosshead 205 to a position corresponding to a preset target mold clamping force according to a tightening command signal from a control device of the injection molding machine body.

In the automatic mold clamping force correction method disclosed in Japanese Patent Laid-Open No. 4-161306, a mold clamping force measuring device is provided to determine a crosshead target position corresponding to the target mold clamping force, and the target mold clamping force is determined. The measured crosshead position is determined as the target crosshead position, but the drive control after the target position is determined is the open control similar to the control method described above.

[0009]

The above-mentioned conventional mold clamping control is an open control in which the target position of the crosshead is set and the crosshead is stopped at the target position. There is a problem.

1) The generated mold clamping force changes delicately when the mold thickness is different.

2) When a force for opening the mold is exerted by the cavity pressure at the time of injection, a mold holding force is generated against it, and a mold clamping force more than a set value may be generated. In general molding, it may work in a good direction against product variations, but this may be a problem in manufacturing methods that require precise mold clamping force control such as injection compression molding that has a mold compression process after resin injection. is there.

An object of the present invention is to solve these problems and to provide a mold clamping control method and a mold clamping control device that enable accurate and precise mold clamping force control.

[0013]

In the mold clamping control method of the present invention, the movable platen position of an injection molding machine having a toggle type mold clamping device is determined based on the geometrical relationship between the crosshead position and the movable platen position. In the mold clamping control method of controlling by controlling the position of the crosshead, during the mold clamping process from the touch of the mold to the completion of mold clamping, the mold clamping force detection means attached to the mold clamping device detects and calculates. The detected clamping force,
If the detected mold clamping force is smaller than the set mold clamping force, the crosshead is advanced in the mold closing direction until the two match and the detected mold clamping force is set. When the force is larger than the force, closed control is performed so that the crosshead is retracted in the mold opening direction until they match.

Further, the mold clamping process from the touch of the mold to the completion of the mold clamping is composed of a plurality of successive stages, and the preset mold clamping force for each stage is maintained for a preset time. You may set it.

In the mold clamping control device of the present invention, in the mold clamping control device of the injection molding machine having the toggle type mold clamping device, the mold clamping force detecting means attached to the mold clamping device and the mold clamping force detecting means detect the mold clamping force. Calculating means for calculating the mold clamping force from the detected value, setting means for setting the set mold clamping force, the detected mold clamping force calculated by the calculating means and the set mold clamping force set by the setting means. And a comparing means for outputting a closed control signal for making the two coincide with each other to the control means of the driving device for driving the crosshead of the mold clamping device.

Further, the setting means has a function capable of configuring the mold clamping process in a plurality of continuous stages and setting the preset mold clamping force for each stage so as to be held for a preset time. You may.

The mold clamping detection means may be a strain sensor attached to a component member of the mold clamping device which causes a distortion when a mold clamping force is applied.

[0018]

With such a mold clamping control method and mold clamping control device,
In the mold clamping process from touching the mold to completion of mold clamping, the current mold clamping force is calculated directly by the mold clamping force detection means instead of the indirect open control of the mold clamping force based on the position of the crosshead in the prior art. Since the crosshead position is closed-controlled so that the detected mold clamping force matches the set mold clamping force as compared with the set mold clamping force, accurate and precise control of the mold clamping force is performed.

Further, it is possible to cope with a change in mold clamping force caused by a change in external force at the same position of the crosshead, which cannot be dealt with in the conventional example.

The mold clamping process from the touch of the mold to the completion of the mold clamping is composed of a plurality of continuous stages, and the preset mold clamping force is set for each stage so as to be maintained for a preset time. In this case, accurate and precise control of the mold clamping force is performed at each stage.

[0021]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a front view and a control block diagram showing the structure of a toggle type mold clamping device of an injection molding machine according to an embodiment of the present invention, and FIG.
3 is a flowchart of a mold closing process and a mold clamping process according to an embodiment of the present invention.

In FIG. 1, 101a is a fixed mold, 101b is a movable mold, 102 is a fixed plate holding the fixed mold 101a, 103 is a movable plate holding the movable mold 101b.
Reference numeral 4 denotes a tie bar that connects and fixes the fixed plate 102 and the mold clamping housing 106 and slidably guides the movable plate 103, 105 a crosshead fixed to the movable portion of the drive unit 107, 106 a mold clamping housing, and 107 A driving device in which the tip of the movable portion is held by the mold clamping housing 106 and is fixed to the crosshead.
3. A toggle mechanism rotatably connected to each of the crosshead 105 and the mold clamping housing 106, and 109 is a position detection device that detects the position of the movable plate 103 from the rotation angle of the drive motor of the drive device 107. Position detection device 10
9 may be a device such as a linear encoder that directly detects the position of the crosshead.

In the figure, reference numeral 108a denotes a mold opening position, 108b denotes a mold touch position, and 108c denotes a mold clamping completion position. When the cross head 105 is moved forward by the drive unit 107, the movable platen 103 to which the movable mold 101b is fixed by the operation of the toggle mechanism is at a high speed in the initial stage, and the speed decreases and the mold clamping pressure increases as the completion of mold clamping approaches. Move forward, fixed mold 101a
Clamp to and clamp.

The mold clamping control device of this embodiment is a drive device 107.
Control device 110 for controlling the drive of the setting device, the setting device 1 for setting the forward speed, the switching position, the set mold clamping pressure and its holding time, etc.
11, a memory 112 that stores the geometrical positional relationship between the crosshead 105 and the movable plate 103, and a tie bar 104
Strain sensor 11 for measuring the strain generated by the mold clamping force
4 and the tie bar 104 detected by the strain sensor 114.
Of the mold clamping force from the amount of distortion of the crossing head 105 and the position of the crosshead 105 detected by the position detecting device 109 in the mold closing process and the set value of the setter 111 to compare the switching signal with the controller 110. In the mold clamping step, the mold clamping force calculated by the calculator 115 is compared with the set mold clamping force set by the setter 111, and a switching signal is sent to the controller 110.
And a comparator 113 for instructing to.

Next, the control method of this embodiment will be described with reference to FIGS. During the mold closing process from the mold opening position 108a (S201) to the mold touching position 108b (S209), the comparator 113 detects the position of the crosshead 105 detected by the position detecting device 109 (S202) and the setting device 1.
While comparing with the switching position such as the forward speed set in 11 (S203), a switching signal is commanded to the control device 110 (S204, S205), and the control device controls the drive device by the command of the comparator 113 to cross. Head 105 and movable plate 1
03 is advanced (S204, S205). When the current set position is reached and the mold closing process is not completed yet, the speed of the next step preset in the setter 111 (S20
7) and the set position (S208) are set as target values and repeated until the mold closing process is completed (S206), and the mold closing process is completed by touching the mold (S209).

In the mold clamping process from the mold touch position 108b to the mold clamping completion position 108c, the current mold clamping force is calculated from the detected strain amount (S210) of the strain sensor 114 attached to the tie bar 104 (S211). If the detected mold clamping force is smaller than the set mold clamping force, the controller 110 is compared with the current set mold clamping force preset in the container 111 (S212).
To move the crosshead 105 forward (S21
3) If the detected mold clamping force is larger than the set mold clamping force, the controller 110 is instructed to retract the crosshead 105 (S
214) The set mold clamping force and the detected mold clamping force are made to match by the closed control and maintained for the set time (S215). If the multi-step setting is not completed after the set time has passed (S216)
Next step time (S217) and mold clamping force (S218)
And are set as target values, and the process is repeated until the mold clamping is completed (S219).

In the above-mentioned embodiment, the driving device 107 may be of an electric type or a hydraulic type, and the set mold clamping force may be one step, or may be multiple steps such as injection compression molding. Further, the strain sensor 114 may be installed at a place other than the tie bar 104, for example, on the lever of the toggle mechanism 108, and the method for detecting the mold clamping force may be a method other than the strain sensor.

[0028]

As described above, the mold clamping control method and apparatus for the injection molding machine of the present invention compares the detected mold clamping force with the set mold clamping force in the mold clamping step and feeds back the difference. Since the closed control is performed and the strain sensor, the mold clamping force calculator, and the comparator for that are provided, the following effects can be obtained.

1) Since it is a closed control for feeding back the actually generated mold clamping force, precise mold clamping force control is possible.

2) Even when the mold thickness is different, the generated mold clamping force does not change at all.

3) Even if a force in the direction of opening the mold is applied due to the cavity pressure at the time of injection, the mold clamping force does not exceed the set value, and the generated mold clamping force as set can be obtained.

4) Even when it is necessary to change the mold clamping force in multiple stages as in injection compression molding, the mold clamping force can be precisely controlled at each stage.

[Brief description of drawings]

FIG. 1 is a front view and a control block diagram showing a structure of a toggle type mold clamping device of an injection molding machine according to an embodiment of the present invention.

FIG. 2 is a flowchart of a mold closing process and a mold clamping process according to an embodiment of the present invention.

FIG. 3 is a front view and a control block diagram showing a structure of a toggle-type mold clamping device of a conventional injection molding machine.

FIG. 4 is a graph showing a relationship between a cross head position and a mold clamping force.

[Explanation of symbols]

 101a, 301a Fixed mold 101b, 301b Movable mold 102, 302 Fixed plate 103, 303 Movable plate 104, 304 Tie bar 105, 305 Crosshead 106, 306 Mold clamping housing 107, 307 Drive device 108, 308 Toggle mechanism 108a, 308a Mold opening position 108b, 308b Mold touch position 108c, 308c Mold clamping completion position 109, 309 Position detection device 110, 310 Control device 111, 311 Setting device 112, 312 Storage device 113, 313 Comparator 114 Strain sensor 115 Computing device S1 ~ S19 step

Claims (5)

[Claims] 1. A movable platen position of an injection molding machine having a toggle type mold clamping device is controlled by controlling a position of the crosshead based on a geometrical relationship between the crosshead position and the movable platen position. In the mold clamping control method, during the mold clamping process from the mold touch to the completion of mold clamping, the detected mold clamping force detected and calculated by the mold clamping force detection means attached to the mold clamping device is preset. When the detected mold clamping force is smaller than the set mold clamping force, the crosshead is advanced in the mold closing direction until the two match, and the detected mold clamping force is compared with the set mold clamping force. If the clamping force is larger than the clamping force, a closed control is performed so that the crosshead is retracted in the mold opening direction until they match each other. 2. The mold clamping control method according to claim 1, wherein the mold clamping process from die touch to completion of mold clamping is composed of a plurality of successive stages, and a preset mold clamping force is preset for each stage. The mold clamping control method according to claim 1, wherein is set so as to be held for a preset time. 3. A mold clamping control device for an injection molding machine having a toggle type mold clamping device, comprising: a mold clamping force detecting means attached to the mold clamping device; and a detection value detected by the mold clamping force detecting means. The calculation means for calculating the mold clamping force, the setting means for setting the set mold clamping force, the detected mold clamping force calculated by the calculating means and the set mold clamping force set by the setting means are compared. And a comparing means for outputting a closed control signal for making the both coincide with each other to a control means of a drive device for driving the crosshead of the mold clamping device. 4. The mold clamping control device according to claim 3, wherein the setting means configures the mold clamping process in a plurality of successive stages, and a preset mold clamping force is preset for each stage. The mold clamping control device according to claim 3, wherein the mold clamping control device has a function that can be set so as to be held for a time. 5. The mold clamping control device according to claim 3 or 4, wherein the mold clamping detection means is attached to a component member of the mold clamping device that causes distortion when a mold clamping force is applied. The mold clamping control device according to claim 3 or 4, wherein