JPH0696252B2 - Injection control method of injection molding machine - Google Patents

Description

TECHNICAL FIELD The present invention relates to an injection control method for an injection molding machine, and more particularly to an injection control method for an injection molding machine for injection molding a disc such as an optical disc or a magnetic disc.

(Background Art) In molding a disc such as an optical disc or a magnetic disc, if internal stress remains in the disc, the quality thereof deteriorates. Therefore, when molding these disks,
It is necessary to prevent internal stress from remaining on the disk as a molded product as much as possible.

To prevent the occurrence of this residual stress, immediately before the filling operation of the resin material into the cavity is completed, the injection pressure is switched to a relatively low pressure, and the filling operation of the resin material into the cavity is performed at the relatively low injection pressure. It is effective to complete it. For that reason, when molding a disc such as the above-mentioned optical disc, in general,
The resin material is injected at a relatively high injection pressure until a predetermined amount of resin material is filled in the cavity, and after the resin material is filled in a predetermined amount in the cavity, the filling operation of the resin material into the cavity is completed. Until the injection pressure is set to a relatively low injection secondary pressure, the resin material is injected into the cavity at the injection secondary pressure, and at the same time the operation of filling the cavity with the resin material is completed,
The injection pressure is switched from the injection secondary pressure to the injection tertiary pressure to cool and solidify the resin material.

Thus, conventionally, the following method has been specifically adopted when molding the disk as described above.

That is, conventionally, the timing of switching the injection pressure to the injection secondary pressure is determined based on the moving position of the injection screw for injecting the resin material into the cavity, and the injection screw has a predetermined injection secondary pressure. At the same time as reaching the switching position, the injection pressure was switched to the injection secondary pressure. Until the injection screw reaches the injection secondary pressure switching position, the resin material is injected into the cavity at a relatively high injection pressure under speed control according to the moving position of the injection screw, that is, under the control of the injection speed. It was supposed to be punished.

In addition, the period during which the injection pressure is maintained at the injection secondary pressure, that is, the period from when the injection pressure is switched and set to the injection secondary pressure until the filling operation of the resin material into the cavity is completed, is set by the timer. The injection pressure is switched from the injection secondary pressure to the injection tertiary pressure when the time set by the timer has elapsed. Then, similarly to the holding period of the injection secondary pressure, the injection pressure is held at the injection tertiary pressure until the time set period elapses, and under the setting of the injection tertiary pressure, the resin material in the cavity is set. The predetermined disk was formed by performing the cooling and solidifying operation.

By molding the disc in this way, the injection secondary pressure switching position, injection secondary pressure holding time, injection tertiary pressure holding time, etc.
By properly setting each of the disks to be molded, a desired disk having a small internal residual stress and excellent quality can be manufactured relatively stably.

However, in such a conventional disc injection control method, as described above, the injection secondary pressure holding time at which the injection pressure is held at the injection secondary pressure is set by a timer in terms of time. Therefore, there is a problem that the amount of resin injected into the cavity during the injection secondary pressure holding period tends to vary due to the unstable movement speed of the injection screw and the like during the injection secondary pressure holding period. As a result, there is a problem in that the weight of the disc and the quality of the disc tend to vary.

The reason why the moving speed of the injection screw is not stable during the injection secondary pressure holding period is that the injection secondary pressure is low. To stabilize the moving speed, increase the injection secondary pressure. It is good, however, when this injection secondary pressure is increased, there arises a problem that the residual stress generated in the disk is increased. Therefore, in the conventional method of temporally setting the injection secondary pressure holding period, In order to suppress the residual stress of the disc, it was unavoidable that the disc quality varied due to the disc weight variation.

(Problem to be Solved) Here, the present invention has been made in view of such circumstances, and a problem thereof is to provide an injection molding machine capable of favorably suppressing residual stress of a disk as a molded article. It is an object of the present invention to provide an injection control method that can suppress variations in disc weight more than conventional methods, and consequently variations in disc quality due to variations in disc weight.

(Solution) In order to solve such a problem, in the present invention, the resin material in the cavity is relatively high until the resin material is filled in a predetermined amount with the movement of the injection screw. Inject at an injection pressure, then set the injection pressure to a relatively low injection secondary pressure until the operation of filling the cavity with the resin material is completed, and inject the resin material into the cavity at a relatively low pressure, After the operation of filling the cavity with the resin material is completed, the resin material is cooled and solidified in a state where the injection pressure is set to a predetermined injection tertiary pressure, and when the predetermined disk is molded, the resin material is not injected into the cavity. Until the injection screw moves to the preset injection secondary pressure switching position where it is filled with a predetermined amount,
While controlling the speed of the injection screw according to its movement position, at the same time when the injection screw reaches the injection secondary pressure switching position, the injection pressure is set to the injection secondary pressure, and the filling operation of the resin material into the cavity is performed. The injection pressure is maintained at the injection secondary pressure until the injection screw moves to the preset injection tertiary pressure switching position, and at the same time when the injection screw reaches the injection tertiary pressure switching position, the injection pressure is changed. The injection tertiary pressure is set, and the injection pressure is maintained at the injection tertiary pressure until a preset cooling / solidifying time elapses.

(Examples) In order to more specifically clarify the present invention,
An embodiment will be described in detail with reference to the drawings.

First, FIG. 1 shows an example of an injection molding machine for disk molding to which the method of the present invention is applied. Therein, 10 is an injection screw inserted in the heating cylinder 12, which is adapted to be rotationally operated by a rotary driving means such as a hydraulic motor (not shown), and is moved in the axial direction by an injection cylinder 14. It is designed to be punished. And, as is well known, the rotation operation of the injection screw 10 by the rotation drive means allows the plasticizing / measuring operation of the resin material to be performed, and the injection is performed after the plasticizing / measuring operation. Screw 10
Is moved forward by the injection cylinder 14,
A predetermined injection operation is performed. As the injection screw 10 moves forward, the resin material is injected from the nozzle at the tip of the heating cylinder 12 into the disk molding cavity 18 of the mold 16.

Here, the injection cylinder 14 is adapted to be driven by hydraulic oil supplied from the pump 20 via the electromagnetic proportional flow rate control valve 22, and its hydraulic pressure is adjusted by the electromagnetic proportional pressure control valve 24. As a result, the forward speed (injection speed) of the injection screw 10 can be adjusted based on the adjustment of the hydraulic oil inflow amount by the electromagnetic proportional flow control valve 22, and the electromagnetic proportional pressure control can be performed. The injection pressure can be adjusted based on the adjustment of the operating oil pressure by the valve 24.

The injection screw 10 is provided with a position sensor 26 for detecting the moving position in the axial direction of the injection screw 10. Then, a position signal representing the moving position (screw position) of the injection screw 10 is supplied from the position sensor 26 to the controller 28. Further, a hydraulic pressure sensor 30 is connected to the injection cylinder 14, and a signal representing the operating hydraulic pressure of the injection cylinder 14, and thus the injection pressure of the resin material during the injection operation, is supplied from the hydraulic pressure sensor 30 to the controller 28. It has become.

Here, a setting device 32 including various setting devices is connected to the controller 28, and a display device 34 such as a CRT is also connected. Then, here, the setting device 34
By using various setting devices provided on the display device 34, it is possible to set the injection control condition associated with the forward movement of the injection screw 10 while visually recognizing each set value on the display device 34. Then, the controller 28, based on the set value set by the setting device 32, arithmetically processes the detection signals from the sensors 26, 30 according to a predetermined program, and the electromagnetic proportional flow control valve 22 and the electromagnetic proportional flow control valve 22. A control signal according to the progress of the injection molding operation is output to the proportional pressure control valve 24.

Incidentally, in such an injection molding machine, an injection step after plasticizing, metering operation, like the conventional injection molding machine for disc molding, as shown in FIG. 2, A _1, A ₂ and A ₃
Is largely divided into three injection control sections, and a control section immediately after the start of the injection operation: A ₁ is further divided into a plurality of control sections (here, four control of a ₁ , a ₂ , a ₃ and a _4). Section).

Here, the control section: A ₁ is a control section for injecting the resin material into the cavity 18 at a relatively high pressure until the resin material is filled in the cavity 18 by a predetermined amount,
Each of the divided control sections: a _{1 to} a ₄ is the moving position (screw position; screw position;
Distance from the forward end position of the injection screw 10): the setting of S ₁ to S _4, is adapted to be defined (see Figure 2). Then, in those control sections: a _{1 to} a ₄ ,
The set pressure of the electromagnetic proportional pressure control valve 24 and the valve opening degree (set flow rate) of the electromagnetic proportional flow control valve 22 are set in the setting device 32 in the same manner as in the conventional case, so that the injection screw 10 is moved according to the moving position. The resin material can be injected into the cavity 18 at a relatively high injection pressure under the control of the injection speed.

That is, in those control sections: a _{1 to} a ₄ ,
As is apparent from the figure, the electromagnetic proportional flow control valve 22 is set to the valve opening (set flow rate) corresponding to the appropriate injection speed: V ₁ , V ₂ , V ₃ , V ₄ for each control section. Further, the injection pressure is sufficiently high: the electromagnetic proportional pressure control valve 24 is set to the set pressure corresponding to P ₁ . With this, in each control section: a _{1 to} a ₄ , in the state where the maximum injection pressure is limited to P ₁ , the appropriate injection speed: V ₁ to V ₁ set for the control section: a _{1 to} a ₄ Since the resin material is filled in the cavity 18 at V ₄ , when the control of the control section: a ₄ is completed, that is, when the control of the control section: A ₁ is completed, a predetermined amount of resin corresponding to the screw position: S ₄ is set. Material is cavity
It can be injected into the 18.

The control section: following the A ₁ Control section: A ₂ is a cavity
It is an injection secondary pressure holding section for suppressing or avoiding residual internal stress in the disk molded product by injecting and filling the resin material in 18 with a relatively low injection secondary pressure. The injection speed: V is maintained at a substantially constant speed: V ₅ , while the resin material is injected into the cavity 18 at a relatively low injection secondary pressure: P ₂ (see FIG. 2). .

That is, in the control section: A ₂ , the setting device 32
By the setting operation of, the electromagnetic proportional pressure control valve 24 is set to a set pressure corresponding to a relatively low injection pressure: P ₂ .
Further, the injection speed under the set pressure (P ₂ ) of the electromagnetic proportional pressure control valve 24 is substantially the same as the reference injection speed or the average injection speed: V ₅
The electromagnetic proportional flow rate control valve 22 is set to the valve opening degree corresponding to. As a result, as in the conventional case, the injection speed: V is maintained at a substantially constant speed: V ₅ , while the resin material is injected into the cavity 18 at a relatively low injection secondary pressure: P _2. It has become.

However, in such a control section: A ₂ , as described above, the electromagnetic proportional flow control valve that defines the maximum injection speed (V ₅ )
The setting pressure of the solenoid proportional pressure control valve 24 that regulates the valve opening degree of 22 and the maximum injection pressure (P ₂ ) is set as before, but the control section: A ₂ itself is regulated by the screw position. It has become. That is, here, as shown in FIG. 2, the screw position: S ₅ set by the setting device 32 defines the control end time of the control section: A _2. .

Further, the control section: A ₃ subsequent to the control section: A ₂ is such that when the resin material is cooled and solidified after the filling operation of the resin material into the cavity 18, the injection pressure P is set to a predetermined injection tertiary pressure. It is the injection tertiary pressure holding section to hold, and the timer time set by the setting operation of the setting device 32 as in the conventional case:
The control period is specified by T ₃ . Then, while the valve opening of the electromagnetic proportional flow control valve 22 is maintained in the setting state of the control section: A ₂ , the setting pressure of the electromagnetic proportional pressure control valve 24 is the pressure corresponding to the predetermined injection tertiary pressure: P _3. By changing the setting, the injection pressure: P in the control section: A ₃ becomes the above-mentioned injection tertiary pressure: P ₃ as in the conventional case.
(See FIG. 2).

If a disk is molded by such an injection molding machine, unlike the conventional case, the injection secondary pressure holding section: A ₂ is defined by the screw position: S ₅ , so the injection secondary pressure holding section: A 5 Even if the injection speed V in ₂ is not stable, the amount of resin injected and filled in the cavity 18 in the injection secondary pressure holding section A ₂ is extremely stable, and the variation in the amount of resin The disc variation due to the disc weight can be suppressed or avoided satisfactorily. Therefore, variations in the quality of the disc due to such variations in weight are suppressed or avoided, and the quality of the disc is significantly stabilized. That is, it is possible to more stably form a disc having excellent quality as compared with the conventional method in which the injection secondary pressure holding section: A ₂ is defined by the timer time.

By the way, the injection secondary pressure holding section (A ₂ ) is set to the screw position (S ₅ ).
A disk molded according to the method of the present invention defined in
By comparing the injection secondary pressure holding section (A ₂ ) with the disk molded according to the conventional method in which the timer time is defined, the disk molded according to the method of the present invention is more excellent than the disk molded according to the conventional method. 30 variations in weight
It is recognized that it will decrease by about%.

As is apparent from the above description, here, the screw position: S ₄ corresponds to the injection secondary pressure switching position, and
Screw position: S ₅ corresponds to the injection tertiary pressure switching position.

Further, in FIG. 2, S ₀ indicates the moving position of the injection screw 10 at the completion of the plasticizing / measuring operation.

Although an example of the present invention has been specifically described above, this is a literal example, and the present invention is not limited to such a specific example, and the knowledge of those skilled in the art is within the scope not departing from the spirit of the present invention. It goes without saying that the present invention can be carried out in a mode in which various changes, modifications, improvements, etc. are made based on the above.

(Effects of the Invention) As is clear from the above description, in the method of the present invention, the injection pressure is set to a relatively low injection secondary pressure at the final stage of the operation of filling the resin material into the cavity, and When suppressing the generation of residual internal stress, not only the start time of the injection secondary pressure holding period for holding the injection pressure at the injection secondary pressure but also the end time thereof is determined based on the moving position of the injection screw. Therefore, the amount of resin injected into the cavity, and thus the weight of the disk molded product, becomes extremely stable throughout the injection secondary pressure holding period, and thus the entire period of the operation of filling the resin material into the cavity. Therefore, it is possible to satisfactorily suppress the variation in the quality of the disc due to the variation in the weight and to significantly stabilize the quality of the disc.

[Brief description of drawings]

FIG. 1 is a system diagram for explaining an example of an injection molding machine for disk molding to which the method of the present invention is applied, and FIG. 2 is an injection for explaining an example of an injection control method according to the present invention. It is a setting chart of a control condition. 10: Injection screw, 18: Cavity 22: Electromagnetic proportional flow control valve 24: Electromagnetic proportional pressure control valve 28: Controller, 32: Setting device

Claims (1)

[Claims] 1. A resin material is injected into a cavity at a relatively high injection pressure until a predetermined amount of the resin material is filled with the movement of an injection screw, and then the resin material is injected into the cavity. After the filling operation is completed, the injection pressure is set to a relatively low injection secondary pressure, the resin material is injected into the cavity at a relatively low pressure, and after the filling operation of the resin material into the cavity is completed. When the injection pressure is set to a predetermined injection tertiary pressure, the resin material is cooled and solidified to form a predetermined disk, and a predetermined amount of the resin material is filled in the cavity. Until the injection screw moves to the pressure switching position, the speed of the injection screw is controlled according to the moving position, and the injection secondary pressure switching position to which the injection screw is applied is controlled. At the same time, the injection pressure is set to the injection secondary pressure, until the injection screw is moved to the preset injection tertiary pressure switching position where the filling operation of the resin material into the cavity is completed. Until the injection screw reaches the injection tertiary pressure switching position where the injection screw is applied, and the injection pressure is set to the injection tertiary pressure until the preset cooling / solidifying time elapses. An injection control method for an injection molding machine, characterized in that the injection pressure is maintained at the injection tertiary pressure.