JP2000141441A - Injection molding method and injection control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the mold release characteristics of a a sprue and gate part while the generation of a stress in a molded product during injection molding is suppressed. SOLUTION: A gate part is shut off under such a state that an injection retaining pressure is applied to a molten resin 52 packed in a molding cavity 34 by injection under a first injection pressure. Further a second injection pressure which is set independently of the first injection pressure and the injection retaining pressure is made act upon a sprue and gate part 54 by applying the second injection pressure without influencing the second injection pressure to the interior of the molding cavity 34.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for injection-molding a molded article such as a disk substrate, and more particularly to a novel injection pressure control method capable of continuously and stably molding a disk substrate or the like. The present invention relates to an injection molding method and an injection control device that can be provided.

[0002]

2. Description of the Related Art Generally, disk substrates used for manufacturing optical disks, magneto-optical disks, and the like are manufactured by injection molding (including injection compression molding) using a resin material. Specifically, for example, after injecting and filling a molten resin from a gate portion through a sprue hole provided in one of the dies, for a molding cavity of a disk substrate formed on a mold mating surface of a pair of dies, By moving the gate cutter provided on the other mold toward the one mold to block the gate portion, and separating the sprue hole and the gate portion from the molding cavity of the disc substrate, Are formed independently of the sprue and gate portions.

[0003] After the disk substrate is cooled and solidified, the mold is opened and removed from the mold. At the same time as the release of the disk substrate, the sprue and the gate portion are also taken out of the die, and then the pair of dies are re-matched and subjected to the next molding, so that the disk substrate is continuously formed. Molded.

Meanwhile, there is a high demand not only for dimensional accuracy but also for quality of disk substrates and the like. Therefore, in order to achieve the required quality, for example, it is conceivable to set the injection holding pressure at the time of molding the disk substrate to be low to avoid the generation of excessive internal stress in the resin filled in the molding cavity. Can be

However, the present inventors have studied and found that
When the injection holding pressure is set low, the quality of the molded product such as a disc substrate can be improved and stabilized.However, at the time of opening the mold or releasing the mold, the sprue portion and the gate portion are separated so that they can be torn apart. As a result, it has been found that only the gate portion may be released, and the sprue portion may remain in the mold. When a part of the sprue and the gate part remains in the mold, continuous molding operation must be temporarily interrupted in order to remove the remaining part from the mold. This has the consequence of having a significant adverse effect on the cycle. Therefore, when trying to secure stable continuous moldability, the degree of freedom in setting the molding conditions becomes very narrow, and for example, it is difficult to set the injection holding pressure low enough to obtain a sufficient quality improvement effect. It was.

[0006]

Here, the present invention has been made in view of the above-mentioned circumstances, and a problem to be solved is to stably secure the releasability of a sprue and a gate portion, It is an object of the present invention to provide a novel injection pressure control technique capable of freely setting a resin pressure applied to a molding cavity over a wide range.

[0007]

In order to solve such a problem, the invention according to claim 1 shuts off the gate portion after injecting and filling molten resin from a gate portion into a molding cavity through a sprue hole. Thus, when forming a molded product in the molding cavity by separating it from the sprue and the gate portion, an injection molding method in which after shutting off the gate portion, a second injection pressure is applied to the sprue and the gate portion, It is assumed that.

According to the method of the present invention, in the cooling step after injection filling of the molten resin, the second injection pressure is effectively applied only to the sprue and the gate. Therefore, the second injection pressure is set to an appropriate level, and when the sprue and the gate portion are cooled and solidified, a sufficient pressure is applied to the sprue and the gate portion, and thereby, the sprue and the gate portion are applied to the mold. By ensuring the adhesion, the hardness and the cooling property of the sprue and the gate portion are improved, and it is possible to stably obtain an integral and good releasability of the sprue and the gate portion. In addition, since the second injection pressure does not affect the resin filled in the molding cavity, the injection pressure exerted on the molded product is not restricted by setting the pressure value for ensuring the quality of the molded product. And the second injection pressure without special consideration of the mutual effect
Since they can be set independently of each other, the quality of the molded product can be advantageously secured in addition to the good releasability of the sprue and gate portions.

In the method of the present invention, the first injection pressure at the time of injection filling of the molten resin into the molding cavity is set to an injection holding pressure smaller than the first injection pressure after the injection of the molten resin into the molding cavity. In addition, the injection molding method of switching the injection holding pressure to the second injection pressure after shutting off the gate portion is preferably adopted. According to such an injection molding method, the filling of the molding cavity is ensured while ensuring the filling property of the molten resin into the molding cavity under the first injection pressure, and the injection holding pressure is set low. An effective second injection pressure can be applied to the sprue and gate portions while suppressing the generation of large internal stress in the resin, so that the sprue and gate can be maintained while maintaining the quality of molded products such as disk substrates. It is possible to improve the releasability of the part and realize stable continuous moldability. In the method of the present invention, after the gate portion is shut off, the injection holding pressure is released once,
Thereafter, it is also possible to apply a second injection pressure.

In the method of the present invention, the second injection pressure may be set at a predetermined delay from the time when the gate section is completely shut off during the cooling step of cooling and solidifying the molten resin filled in the molding cavity. It is desirable to start the operation from the time when the time has elapsed, and to end the operation before the completion of the cooling step. Thereby, the effect of the second injection pressure on the resin filled in the molding cavity can be avoided, and the second injection pressure can be more stably applied only to the sprue and the gate portion.

Furthermore, in order to solve the above-mentioned problem, the invention according to claim 4 is to shut off the gate portion after injecting and filling a molten resin from a gate portion into a molding cavity through a sprue hole. In the injection molding apparatus for separating a sprue and a gate portion from a molding cavity to form a target molded product, the injection control device controls the injection pressure of the molten resin, and (a) First pressure setting means for setting a first injection pressure applied during injection filling of the molten resin,
(B) holding pressure setting means for setting an injection holding pressure applied after filling the molten resin into the molding cavity; and (c) a second pressure applied to the sprue and the gate portion after the gate portion is shut off. And a second pressure setting means for setting the injection pressure.

In the injection control apparatus having the structure according to the present invention, the second injection pressure set to a value different from the first injection pressure and the injection holding pressure applied to the molten resin filled in the molding cavity. Can be applied only to the sprue and the gate portion without affecting the molten resin filled in the molding cavity. Moreover, the first injection pressure and the injection holding pressure can be set in consideration of the quality of the injection molded product, and the second injection pressure and the injection holding pressure can be set without being restricted by the set values of the first injection pressure and the injection holding pressure. The injection pressure can be set freely to affect the sprue and gate parts. Accordingly, the achievement of the desired requirements such as the quality of the intended injection-molded product, and the improvement of the mold release of the sprue and the gate part accompanying the improvement of the hardness and the cooling property of the sprue and the gate part are achieved at the same time. And therefore,
The improvement of the quality of the molded product to be manufactured and the stable continuous moldability can be realized in a highly compatible manner.

In this injection control apparatus, for example, the holding pressure setting means sets the injection holding pressure to a value smaller than the first injection pressure and sets the second pressure setting means to an appropriate value. At the time of molding a substrate or the like, reduction of internal stress in the molten resin forming the molded article and improvement of continuous moldability due to improvement of the releasability of the sprue and the gate portion can be achieved at the same time.

Further, in the injection control device having the structure according to the present invention as described above, for example, the injection holding pressure is changed from the injection holding pressure to the second injection pressure with reference to the operation start time of the gate cutter for shutting off the gate portion. Timer means for setting the switching timing is preferably employed. By employing such a timer means, the timing of switching from the injection holding pressure to the second injection pressure can be advantageously set to a substantially constant time after the gate is shut off, and further stabilization of the molding operation is advantageous. It becomes feasible. The reference to the operation start time of the gate cutter refers to the timing of switching to the second injection pressure with reference to the start time of operation of the gate cutter. The switching to the pressure can also be realized by, for example, timing a common time as a reference time. That is, it is only necessary that the time between the start of operation of the gate cutter and the time of switching to the second injection pressure can be set.

Further, in order to solve the above-mentioned problems, the present invention provides (α) an injection step of injecting and filling a molten resin from a gate portion through a sprue hole into a molding cavity during injection molding by an injection molding machine. A first pressure setting process for setting a first injection pressure to be adopted; (β)
Holding pressure setting processing for setting an injection holding pressure that is applied after filling the molten resin into the molding cavity,
(Γ) In the course of the cooling step of cooling and solidifying the molten resin filled in the molding cavity, the second injection pressure employed after the sprue and the gate portion are separated from the molding cavity by shutting off the gate portion, A second pressure setting process to be set, by causing a computer to execute each, a computer-readable recording medium that records a program that enables the second injection pressure to be set to a value larger than the injection holding pressure. Are also features.

By employing such a recording medium according to the present invention, an injection control device having a structure according to the present invention as described above can be advantageously realized. Note that the setting of the first injection pressure in the first pressure setting process, the setting of the injection holding pressure in the holding pressure setting process, and the setting of the second injection pressure in the second pressure setting process are each independently performed from the outside. Although it is possible to perform the operation by an input command signal, the relative relationship among the first injection pressure, the injection holding pressure, and the second injection pressure is set in advance by an arithmetic expression or the like, and the relative pressure is set. Based on the relationship, automatically set another set value from one set value, or
It is also possible to automatically set each set value based on other injection molding conditions. In this case, the relative magnitude relationship between the first injection pressure, the injection holding pressure, and the second injection pressure is not particularly limited, and can be freely determined.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, in order to clarify the present invention more specifically, embodiments of the present invention will be described in detail with reference to the drawings.

First, FIG. 1 shows a hardware configuration of a disk substrate injection molding system including a control device 10 according to one embodiment of the present invention. Such an injection molding system includes a mold clamping device 14 and an injection device 16.
And a known injection molding machine 18 having The mold clamping device 14 includes a mold clamping mechanism 20 such as a hydraulic type or an electric type.
The fixed mold 22 and the movable mold 24 are opened and closed by each other to form a molding cavity of the disk substrate between the mold mating surfaces.
Is provided. On the other hand, the injection device 16
An in-line screw type injection device having a heating cylinder 28 in which an injection screw is inserted and arranged, wherein a resin material supplied from a hopper 26 is guided into the heating cylinder 28, and the injection screw is rotated by a driving mechanism 30 such as a hydraulic motor. The resin material is heated and melted by driving, and is sent forward while applying a back pressure. Then, the driving mechanism 32 such as a hydraulic cylinder drives the injection screw in the axial direction so that the molten resin material is injected from the nozzle. It has become.

That is, as shown in an enlarged cross section of the main part in FIG. 2, the fixed die 22 and the movable die 24 are mated to form a disk between the mating surfaces of the two dies 22 and 24. A molding cavity 34 for the substrate is formed. A sprue bush 38 is inserted into a mounting hole 36 penetrating through the center of the fixed mold 22 supported in a fixed position by the mold clamping device 14. It is assembled so that it cannot escape. In the stationary die 22 shown in FIG. 2, the annular shim 42 is prevented by interposing the shim 42 in the axial direction between the sprue bush 38 and the stationary die 22,
Thus, the sprue bush 38 is fixedly attached to the fixed mold 22, and the axial movement of the sprue bush 38 is prevented. Then, when the nozzle 44 of the heating cylinder 28 of the injection device 16 is brought into nozzle contact with the axial outer surface of the sprue bush 38, the molten resin 52 injected from the nozzle 44 passes through the center hole of the sprue bush 38. Through 46, it is led to the molding cavity 34.

On the other hand, a male cutter 48 having a rod shape as a gate cutter is provided at the center of the movable mold 24 so as to be movable in the axial direction. The ejector sleeve 56 is disposed so as to be movable in the axial direction independently of the male cutter 48 in a state of being externally inserted into the cutter 48. Such a male cutter 48 is
The distal end surface is positioned so as to protrude toward the fixed die 22 side from the cavity forming surface of the movable die 24, and the outer peripheral edge of the protruded distal end portion is positioned with respect to the peripheral edge of the opening of the mounting hole 36 in the fixed die 22. The outer peripheral edges of the male cutters 48 and the fixed mold 2
An annular gate 50 located at the center of the molding cavity 34 of the disk substrate is formed between the two mounting holes 36 facing the peripheral edge of the opening. In short, the molten resin 52 guided from the injection device 16 into the molding die through the center hole 46 of the sprue bush 38 is guided through the annular gate 50 to the molding cavity 34 of the disk substrate to be filled. It is.

The male cutter 48 of the movable mold 24 is driven forward / backward in the axial direction by a drive mechanism (not shown), and the male cutter 48 is closed when the dies 22, 24 are closed. Is advanced toward the fixed mold 22 so that the tip of the male cutter 48 is fixed to the fixed mold 2.
2 is fitted into the opening of the mounting hole 36. Therefore, as shown in FIG. 3, by injecting the molten resin 52 into the molding cavity 34 of the disk substrate and then operating the male cutter 48 to project, the annular gate 50 is shut off, and the disk substrate is molded. The cavity 34 is separated from the sprue and gate portion 54;
Thus, a target disk substrate is formed.

Further, the ejector sleeve 56 mounted on the male cutter 48 in an externally inserted state forms a part of the forming surface of the molding cavity 34 of the disk substrate by its axial front end surface. The mechanism is configured to be driven forward / backward in the axial direction independently of the male cutter 48. As described above, after the disk substrate is formed and the fixed mold 22 and the movable mold 24 are opened, the ejector sleeve 56 is driven forward and protruded in the axial direction, so that the movable mold 24 is moved toward the movable mold 24. The disk substrate as a molded product is taken out by projecting the held disk substrate and releasing it from the movable mold 24.

An injection molding system including such an injection molding machine 18 having the mold clamping device 14 and the injection device 16 is a mold clamping control device for controlling the operation of the mold clamping mechanism 20 of the mold clamping device 14. 58 and the drive mechanism 3 of the injection device 16
The control device 10 including the injection control device 60 for controlling the operation of the control devices 0 and 32 is operated, for example, in accordance with the time chart shown in FIG. Becomes As the control device 10, for example, a conventionally known controller for an injection molding machine can be adopted.
The CPU includes a PU, a ROM, and a RAM, and uses a value externally input by the set value input device 62 and various types of data set in advance and stored in the RAM, according to a program stored in the ROM. , The mold clamping mechanism 20 and the driving mechanisms 30 and 3 are operated so that the desired injection molding operation of the disk substrate is realized.
An operation control signal such as 2 is output.

An operation mode when the disk substrate is injection-molded by the injection molding machine 18 of the present embodiment having the above-described structure will be described with reference to a time chart shown in FIG.
This will be described more specifically below.

That is, first, the fixed mold 2 of the mold clamping device 14
2 and the movable mold 24, while keeping the injection device 16 in nozzle contact with the mold clamping device 14, the mold clamping mechanism 20 is operated in the mold clamping device 14 to reduce the speed from the high speed mold closing operation to the low speed. The mold cavity is formed by closing the movable mold 24 and the fixed mold 22 through the mold closing operation shown in FIG. In parallel with such a mold closing operation, in the injection device 16, the driving mechanism 30 rotates the injection screw to melt one shot of the resin material, and sends the resin material to the front of the injection screw for storage. Then, the mold clamping device 14
In the above, the fixed mold 22 and the movable mold 2 are
After increasing the pressure exerted on the injection screw 4 to apply the mold clamping pressure to clamp the mold at a high pressure, the drive mechanism 32 applies an injection pressure (first injection pressure: P1) to the injection screw of the injection device 16, and the injection screw is pressed. By driving forward, the molten resin material is injected and filled into the molding cavity 34 of the mold clamping device 14. Note that injection compression molding can be performed by increasing the mold clamping pressure in the mold clamping device 14 substantially at the same time as or slightly after the forward movement of the injection screw.

Next, during the injection step, after filling the molten resin into the molding cavity 34, the injection pressure in the injection device 16 is changed from the first injection pressure: P1 for injection-filling the molten resin into the molding cavity 34, Injection holding pressure: lower than P _R , and the molding cavity 3
The molten resin 52 filled in 4 is held under a predetermined holding pressure. Furthermore, after the filling of the molten resin material into the molding cavity 34 is completed, in other words, almost simultaneously with or slightly after switching to the injection holding pressure in the injection device 16,
The cooling of the fixed mold 22 and the movable mold 24 is started, and the cooling of the molten resin 52 filled in the molding cavity 34 is started.

The molding cavity 34 of the molten resin material
After the completion of the filling, the male cutter 48 is driven forward with a predetermined delay time T1 from the start of cooling, and the male cutter 48 is inserted into the mounting hole 36 of the fixed mold 22 as shown in FIG. By maintaining the fitting state, the molding cavity 34 and the sprue and gate portion 54 are separated from each other and maintained in a state of being separated and independent. This allows
The center hole of the disk substrate is formed, and the annular gate 5 is formed.
0 is closed to prevent movement of molten resin 52 between sprue and gate portion 54 and molding cavity 34.

Further, after the annular gate 50 is closed, the injection pressure (injection holding pressure: P
_R ) is once released or directly switched without being released, thereby setting the injection pressure of the injection device 16 to the second injection pressure: P2 and keeping the same. As a result, the molding cavity 34 and the sprue and gate portion 54 are separated from each other by closing the annular gate 50, so that cooling of the molding cavity 34 proceeds while substantially maintaining the injection holding pressure: P _R. On the other hand, cooling of the sprue and gate portion 54 proceeds while the second injection pressure: P2 is applied. The operation start point of the second injection pressure: P2 is set after the annular gate 50 is shut off by the advancement of the male cutter 48. For example, a timer incorporated in a microcomputer constituting the injection control device 60 is used. Alternatively, prepare a separate timer and use the cooling start time as the measurement start point,
Delay time for outputting forward start signal of male cutter 48: T1
With a delay time greater than T2, a signal that causes the once released injection pressure to be applied again by the second injection pressure or a control mechanism that outputs a signal that directly switches the injection pressure from the injection holding pressure to the second injection pressure is output. Two injection pressures: P
2 can be advantageously set. Further, the second injection pressure: P2 can be applied until the cooling step is completed. However, when the cooling and solidification of the sprue and the gate portion 54 have progressed to some extent, the second injection pressure: P2 may be used at a point before the cooling step is completed. To complete its operation, and thereafter, the injection device 16
May be released, or an injection pressure smaller than the second injection pressure: P2 may be applied until the completion of the cooling step. The operation time of the second injection pressure: P2 can also be set by, for example, a timer.

Then, when the cooling step is completed and the molten resin 52 filled in the molding cavity 34 is cooled and solidified, a depressurizing step of releasing the injection pressure in the injection device 16 is performed if necessary. In the clamping device 14, the movable mold 24 is moved away from the fixed mold 22 by the mold clamping mechanism 20 to open the mold, and then the ejector sleeve 56 of the movable mold 24 is driven forward, so that the disk substrate as a molded product is moved. Release and remove. At the same time,
The fixed type 2 is held in a fixed state on the tip end surface of the male cutter 48.
The sprue and gate portion 54 extracted from 2 are also released from the male cutter 48 by releasing the mold. Then, by taking out the molded product of the disk substrate and the sprue and gate portions 54 from the injection molding machine 18, the molding of one shot of the disk substrate is completed.

In the control device 10 of the present embodiment, the first injection pressure: P1 and the injection holding pressure: P _R and the second injection pressure: P2 applied to the molten resin 52 in the injection step and the cooling step. Can be set independently of each other, and the drive mechanism 32 of the injection device 16 is controlled according to each set value. A specific example of the control mode of the injection pressure will be described with reference to a flowchart shown in FIG.
This will be described below.

First, at the start of the disk substrate molding operation by the injection molding system, in step S1, the number of shots, that is, the number of disk substrate moldings, is set. In the subsequent steps S2 to 4, the first injection pressure:
The respective values of P1, injection holding pressure: P _R , and second injection pressure: P2 are set to appropriate values. The set of these values is set by the setting value input device 6 in the control device 10.
2 At the same time as this setting, for example, the delay time T1, T2, etc., of the male cutter advance start time based on the cooling start time or the switching time to the second injection pressure may be set to an appropriate value. good.

Then, in these steps: S2 to S4
After completing the data setting work, the injection molding system
The molding operation is started, and first, the mold clamping control device 58
The mold clamping mechanism 20 is operated to close the mold in the mold clamping device 14.
In addition to the operation and mold clamping operation by pressure increase, the injection control
The driving mechanism 30 is operated by the device 60 to
Melts or measures the resin material. Also,
Step: In S5, the completion of mold clamping of the molds 22 and 24 was confirmed.
Then, in the following step: In S6, the injection control device 60
By operating the moving mechanism 32, the injection device 16
In the first injection pressure: P1, the molten resin
Is injected into the molding cavity 34 of the disk substrate.
Subsequent step: In S7, the first injection pressure: Injection hold from P1
Holding pressure: P _RSwitching signal (holding pressure switching signal)
Judge whether the signal is input or not.
Step: Proceed to S8 to inject the injection pressure in the injection device 16.
Holding pressure: P_RTo maintain the pressure and cooling process
to go into. In addition, the delay time is set based on the cooling start time.
Initiate the aging of the ima.

Further, in step S9, it is determined whether or not a gate cut signal has been input. If such a signal has been input, in step S10, the male cutter 48 is driven forward, and Ring gate 5
Block 0. Note that, as the gate cut signal, for example, a signal (forward drive signal) output when the delay time: T1 elapses from the cooling start time using the elapse of the delay timer can be used.

Subsequently, in step S11, it is determined whether or not the elapsed time of the delay timer has reached a preset start time of the action of the second injection pressure. injection holding pressure injection pressure in the injection device 16: switching to P2: P _R from the second injection pressure. Thereafter, in step S13, it is determined whether or not the elapsed time of the delay timer has reached a preset end time of the action of the second injection pressure. If the end time has been reached, the injection device 16 is determined in subsequent step S14. Is released (second injection pressure: P2), and the mold clamping state is maintained until the cooling completion signal in step S15 is input. After the gate cut by the male cutter 48 is completed, the injection holding pressure: P _R is temporarily released, and after the second injection pressure: P2 reaches the operation start point, the injection pressure (second injection pressure) is increased again. May act. Further, after reaching the end point of the operation of the second injection pressure, it is possible to continue to apply the appropriate holding pressure to the sprue and the gate portion 54 without releasing the injection pressure until the cooling completion signal is input. is there.

If the cooling completion signal is input in step S15, the pressure in the injection device 16 is released by the injection control device 60 if necessary in step S16. Then, the mold opening operation of the mold clamping device 14 and the removal operation (release operation) of the molded product by the ejector sleeve 56 are performed, and the disk substrate, the sprue, and the gate portion 54 which are the formed molded product are taken out.
Thereafter, in step S17, it is determined whether or not the number of shots has reached the number set in step S1, and the operations in steps S5 to S16 are repeated until the number of shots reaches the set number of times. The disk substrate is continuously formed, and then the process is terminated.

In the molding of the disk substrate by the injection molding system as described above, the molten resin is injected and filled into the molding cavity 34 of the disk substrate under the condition of the first injection pressure: P1, and then the molding cavity is formed. Injection holding pressure: P _R for molten resin 52 filled in
There is caused to act, the injection holding pressure: under the action state of the P _R, the cooling step is performed. On the other hand, in the sprue and gate portion 54, as in the molding cavity 34,
The first injection pressure: P1 is actuated and then switched to the injection holding pressure: P _R. However, after the cooling process is started and the sprue and gate portion 54 are separated from the molding cavity 34, the second injection pressure: P1 is released. The second injection pressure: P2 is applied, and under the operation state of the second injection pressure: P2,
A cooling step is performed.

[0037] Therefore, in the disc substrate molded by the molding cavity 34, a small injection holding pressure: Set the P _R, while suppressing the generation of internal stress, and than can be molded, following Te, birefringence Thus, it is possible to stably manufacture a disk substrate having excellent quality.

Further, since the sprue and gate portion 54 can be cooled under the action of the second injection pressure P2 after being shut off from the molding cavity 34, the sprue and gate portion 54 can be tightly attached to the mold. It is advantageously solidified and improved in strength by improving the cooling performance, etc.,
Breaking of the molds 22, 24 when the molds are opened can be prevented, and interruption of continuous molding due to the sprue and the gate portion 54 remaining partially in the stationary mold 22 (mistake) can be advantageously avoided. Thus, it is possible to stably and continuously form the disk substrate.

Further, the present inventor has studied and found that the sprue and the gate portion 54 are also improved in the breakage of stringing when the sprue and the gate portion 54 are taken out from the fixed mold 22. This effect is considered to be due to the improvement of the cooling effect caused by the large second injection pressure acting on the sprue tip.

Although the embodiment of the present invention has been described in detail above, this is merely an example, and the present invention is not to be construed as being limited by the specific description in the embodiment.

For example, the present invention relates to CD, DVD, MO,
It is particularly preferably used when molding various disk substrates such as PDs, but also when molding various resin products other than disk substrates, especially when quality such as dimensional accuracy and resin characteristics is regarded as important. Can be advantageously employed over a wide range. At that time, depending on the quality and the like required for each product, in consideration of the type of resin material, etc., for example, the injection holding pressure is higher than the first injection pressure, or the second injection pressure is lower than the injection holding pressure. Or, the second injection pressure higher or lower than the first injection pressure, can be appropriately set,
The relative magnitude of each pressure can be set freely according to various requirements.

In the above embodiment, the sprue bush 38 is fixedly mounted on the fixed mold 22. However, as is conventionally known, the sprue bush 38 is fixed to the fixed mold 22. A sprue bushing slide mold that is mounted movably in the axial direction and moves the sprue bush 38 in the direction in which the gate cutter projects when the gate cutter projects. The present invention is also applicable to the case of injection molding using.

In addition, although not enumerated one by one, the present invention
Based on the knowledge of those skilled in the art, various changes, modifications, improvements, and the like can be made, and unless such embodiments depart from the spirit of the present invention.
Both are included in the scope of the present invention,
Needless to say.

[0044]

As is apparent from the above description, according to the present invention, the second injection pressure is applied to the sprue and the gate portion without being limited by the injection pressure applied to the molded product during the injection molding. Can be done. Therefore, regardless of the magnitude of the injection pressure and the like exerted on the molded article, which is limited by the quality and the like required for the product, the second injection pressure of an appropriate magnitude is applied only to the sprue and the gate portion,
It is possible to advantageously and stably obtain the removability of the sprue and the gate portion from the mold at the time of release from the mold.
As a result, the quality of the molded product and the stability of the molding
At the same time, both can be obtained at a high level.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a disk substrate injection molding system configured to include an injection control device as one embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part for explaining a molding operation of a disk substrate by the injection molding system shown in FIG. 1;

3 is an enlarged sectional view of a main part showing a molding operation state of the disk substrate by the injection molding system shown in FIG. 1 which is different from that of FIG. 2;

FIG. 4 is a time chart showing a specific example of a molding operation of a disk substrate by the injection molding system shown in FIG. 1;

FIG. 5 is a flowchart showing a specific operation control example when molding a disk substrate by the injection molding system shown in FIG. 1;

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 control device 14 mold clamping device 16 injection device 18 injection molding machine 20 mold clamping mechanism 22 fixed mold 24 movable mold 30, 32 drive mechanism 34 molding cabidi 38 sprue bush 48 male cutter 50 annular gate 52 molten resin 54 sprue and gate part

Claims (5)

[Claims] 1. A molded product in a molding cavity is separated from a sprue and a gate portion by injecting and filling a molten resin from a gate portion through a sprue hole into a molding cavity and then closing the gate portion. In this case, after shutting off the gate portion, a second injection pressure is applied to the sprue and the gate portion. 2. The method according to claim 1, wherein the first injection pressure at the time of injection filling of the molten resin into the molding cavity is switched to an injection holding pressure lower than the first injection pressure after the injection of the molten resin into the molding cavity. The injection molding method according to claim 1, wherein the injection holding pressure is switched to the second injection pressure after the part is shut off. 3. The method according to claim 1, wherein the second injection pressure is changed from a point in time when a predetermined delay time elapses from a point in time when the gate section is completely shut off during a cooling step of cooling and solidifying the molten resin filled in the molding cavity. Let the action start,
3. The injection molding method according to claim 1, wherein the operation is completed before the completion of the cooling step. 4. After injection molding and filling a molten resin from a gate portion into a molding cavity through a sprue hole, by closing the gate portion, the sprue and the gate portion are separated from the molding cavity to obtain a desired molded product. In an injection molding device to be formed, an injection control device for controlling an injection pressure of the molten resin, wherein first pressure setting means for setting a first injection pressure applied when the molten resin is injected and filled into the molding cavity. Holding pressure setting means for setting an injection holding pressure to be applied after filling the molten resin into the molding cavity; and setting a second injection pressure to be applied to the sprue and the gate portion after shutting off the gate portion. And a second pressure setting means. 5. The injection control according to claim 3, further comprising timer means for setting a timing of switching from the injection holding pressure to the second injection pressure based on a start time of an operation of the gate cutter for shutting off the gate section. apparatus.