JPH106367A - Injection mold and injection molding method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the molding cycle of a molded product by cooling and solidifying a molten resin within a short time and to reduce molding inferiority by forming an air hole permitting air to pass to a core pin so as to pierce the same in its axial direction. SOLUTION: The high pressure air supplied from an air supply source passes through the air hole 8 of each core pin 7 to flow in a resin passage 4 from a gap and removes the heat of the core pin 7 heated by a molten resin when passes through the air hole 8 or flows in the resin passage 24 to directly remove heat from the molten resin to flow out of a mold from the gap between a core block 4 and a cavity 21. Therefore, the molten resin injected into the resin passage 24 is cooled and solidified within a short time. By passing high pressure air through the air hole 8 to enhance a heat exchange ratio, the molten resin injected into the resin passage 24 can be cooled and solidified within a short time and, therefore, the shortening of the molding cycle of a molded product can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to injection molding of a molded product, and more particularly, to molding of a molded product by cooling and solidifying a molten resin by passing air through a core pin provided in a mold core. The present invention relates to an injection molding mold to be molded and an injection molding method using the mold.

[0002]

2. Description of the Related Art Conventionally, molding of a molded product using an injection mold is performed by inserting a core 53 having a core pin 52 into a molding cavity of a cavity 54 and closing the core 53 as shown in FIG. 53, core pin 52 and cavity 5
4, a resin passage 56 corresponding to the shape of the molded product is formed, a molten resin is injected into the resin passage 56 and filled, and then the filled molten resin is cooled and solidified.

As a method of cooling and solidifying the molten resin injected into the resin passage 56 as described above, as shown in FIG. 4, a cooling hole 60 formed in a core pin 52 is formed by a separator 61 (plate). By circulating the cooling water through the divided cooling passages 62 and 63, the core pin 52 is cooled, and the molten resin is cooled and solidified. by the way,
In order to circulate the cooling water, the diameter of the cooling hole 60 formed in the core pin 52 is minimized within the range of 8 to 10 mm, and the diameter of the core pin 52 for forming the hole 60 is 18 mm or more. Things are used. in this way,
The limitation of the diameter of the cooling hole 60 with respect to the core pin 7 is as follows.
If the diameter is reduced (less than 8 mm), it becomes difficult to flow due to the viscosity (viscosity) of the cooling water, and if the diameter is increased (10 mm or more) to flow the cooling water, the diameter becomes 1
In the case of a core pin 7 having a diameter of 8 mm or less, a cooling hole 6 having a diameter of 10 mm
This is because at the time of machining 0, the machining hole meanders, breaking the side surface of the pin 7 or causing the core pin 7 to have a reduced strength, and the core pin 7 falls down due to the pressure of the injected molten resin.

[0004]

However, in the conventional method of circulating cooling water to cool the molten resin (core pin 52), if the diameter of the core pin 52 becomes smaller than 18 mm, the above-described reason is obtained. The hole 60 through which the cooling water is circulated cannot be formed in the core pin 52. Therefore, in order to cool and solidify the molten resin injected into the resin passage 56, the core pin 52 that contacts the molten resin is required.
And other commonly used metal materials (eg,
S55C) has a life equivalent to that of S55C), and is changed to one having excellent thermal conductivity, so that the core block 5 in contact with the core pin 52
In this case, heat is transmitted to the molten resin 1 to cool and solidify the molten resin.

In order to cool and solidify the molten resin injected into the resin passage 56, the core pin 5 of the molding die X
2 and other commonly used metal materials (eg, S55C)
Therefore, if the metal material is changed to a metal material having the same life and excellent thermal conductivity, the unit price of the material is high, the processing is difficult, and the cost of the injection molding die X is remarkably increased.

The method of changing the metal material of the injection molding die X and propagating heat to cool and solidify the molten resin is different from the method of circulating the cooling water to cool and solidify the molten resin. Since the cooling efficiency is poor, the molding cycle of the molded product is prolonged. Furthermore, if the cooling time is shortened and the cooling water is circulated and the cooling cycle is set to be the same as the molding cycle, a part that cannot be cooled and solidified in the molded product remains locally, secondary foaming or the mold temperature ( Since the temperature of the core block 51, the core pins 52, and the cavities 54) is high, the amount of gas generated from the molten resin increases, and the gas cannot be completely removed from the resin passage, so that the gas remains and the molten resin is sufficiently filled in the resin passage 56. However, there was a fear that molding defects such as short shots were caused.

[0007] The present invention has been made to solve such a problem, and allows air to pass through a core pin,
By cooling and solidifying the molten resin in a short time, the molding cycle of the molded product is shortened and molding defects are reduced.

[0008]

In order to solve the above-mentioned problems, an injection molding die of the present invention and an injection molding method using this die are characterized in that, in the injection molding die of claim 1, a core pin is provided. A molding die having a core and a cavity, and forming a resin passage corresponding to the shape of a molded product inside the core and the cavity when the core and the cavity are closed. An air hole that penetrates and allows air to pass therethrough is formed, and the air hole is closed at the time of the closing so that low-pressure air having a predetermined pressure or less passing therethrough does not enter the resin passage. is there. By injecting the low-pressure air into the air holes when injecting the molten resin into the resin passage, the low-pressure air enters the resin passage from the closed air hole, or the molten resin in the resin passage enters the air hole. Is blocked. Also, when high-pressure air is supplied to the air holes after the surface of the injected molten resin is cooled and solidified, the blockage of the air holes is released by the high-pressure air, and the high-pressure air is released from the mold through the air holes and the resin passage. Since it flows to the outside and the high-pressure air passing through the air holes and the resin passage deprives the core pin and the molten resin of heat, the heat exchange rate can be improved, so that the molten resin can be cooled and solidified in a short time.

In the injection molding die according to the second aspect,
The diameter of the core pin is 18 mm or less, and the diameter of the air hole is in the range of 3 to 5 mm. As a result, the diameter of the core pin becomes 1
High pressure air for cooling and solidifying the molten resin can be passed through the air holes without reducing the strength of the core pin, even if the diameter is 8 mm or less.

According to the third aspect of the present invention, there is provided an injection molding die.
The air hole is connected to an air supply source for switching between low-pressure air and high-pressure air, and the switching of the air supply source is performed by control means for executing a molding cycle of the molded product. Is controlled. As a result, in accordance with the effectiveness of the molding cycle of molded products,
Switching between low-pressure air and high-pressure air supplied to the air holes of the core pin can be automatically performed.

According to a fourth aspect of the present invention, there is provided a molding method having a core having a core pin and a cavity forming a resin passage corresponding to the shape of a molded product by closing the core, and penetrating the core pin in the axial direction thereof. Providing an injection mold having an air hole formed therein, a step of passing low-pressure air through the air hole, closing the core and the cavity, forming the resin passage, and forming the air hole. A step of closing the resin passage so that the low-pressure air does not flow, a step of injecting the molten resin into the resin passage, and a hardness at which air does not enter the surface of the molten resin injected into the resin passage. After solidifying the air, the air passing through the air holes is switched from low-pressure air to high-pressure air, and the high-pressure air passing through the air holes cools the molten resin. And solidifying opens the said cavity preparative and the core, are those which comprise a step of taking out the molded products molded. By injecting low-pressure air through the air holes when injecting the molten resin into the resin passage, low-pressure air enters the resin passage from the closed air hole, or molten resin in the resin passage enters the air hole. Is blocked. Also, when high-pressure air is supplied to the air holes after the surface of the injected molten resin is cooled and solidified, the blockage of the air holes is released by the high-pressure air, and the high-pressure air is released from the mold through the air holes and the resin passage. Since it flows to the outside and the high-pressure air passing through the air holes and the resin passage deprives the core pin and the molten resin of heat, the heat exchange rate can be improved, so that the molten resin can be cooled and solidified in a short time.

In the injection molding method according to a fifth aspect, the low pressure air passing through the air hole is added to the one according to the fourth aspect.
The pressure is controlled within the range of 1.5 to 2.0 kg / cm ² , and the high-pressure air passing through the air holes is controlled to 4.0.
The pressure is controlled within the range of 5.0 kg / cm ^{2 to} 5.0 kg / cm ² . Thus, by applying a low pressing force to the core pin, the air hole can be closed while preventing the core pin from falling down, and the air hole can be released with the pressure of the normally used high-pressure air.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a mold for injection molding of the present invention,
An injection molding method using this mold will be described with reference to the drawings.

First, a molding die Y of the present invention is shown in FIG.
A description will be given based on FIG. 1 and 2, an injection mold Y (hereinafter simply referred to as "molding mold Y") includes a movable mold 1 that is movable and a fixed mold 2 that is fixed. Have been.

The movable mold 1 includes a core 4 fixed to a core mount 3 connected to an actuator (eg, a hydraulic cylinder) of an injection molding machine (not shown), and a fixed mold 2.
And a core block 5 attached to the core 4 so as to protrude to the side. Two mounting holes 6 penetrating in the vertical direction are formed in the core block 5 in parallel with each other, and a core pin 7 is arranged in each mounting hole 6. The core block 5 is formed in a convex shape corresponding to the shape of the molded product.

Each of the core pins 7 is press-fitted into each of the mounting holes 6 and protrudes from the fixed mold 2 by a predetermined amount.
Further, inside each core pin 7, an air hole 8 penetrating in the axial direction is formed.
Through the communication hole 9 formed in the movable die 1. Here, the diameter d of the air hole 8 depends on the size of the small-diameter projection formed on the molded product. In particular, when the diameter D of each core pin 7 is 18 mm or less, the air passage And the processing is easy and the strength of each core pin 7 is not impaired.
5 mm. Note that the diameter d of the air hole 8 is not limited to the above numerical value, and is preferably a diameter that maximizes the contact area between the air and the core pin 7 without impairing the strength of each core pin 7.

The communication hole 9 of the core 4 is connected to an air supply source 10. The air supply source 10 includes two solenoid valves 11 and 12 that are separately connected via a pipe to a compressor (pump) 13 that discharges air at a constant pressure, and a downstream side (core 4) of each of the solenoid valves 11 and 12. (The side of the communication hole 9).
Each of the pressure reducing valves 14 and 15 is connected to the communication hole 9 of the core 4 via a pipe, and reduces the pressure of the air discharged from the compressor 13 to high-pressure air and low-pressure air. Is supplied to the inside of the air hole 8. Each of the electromagnetic switching valves 11 and 12 is connected to a controller 17 that executes a molding cycle of a molded product.
FF ". Reference numeral 16 denotes an on-off valve disposed between the compressor 13 and each of the solenoid valves 11 and 12. Here, the pressure reducing valve 14 reduces the pressure of the discharge air from the compressor 13 to low pressure air within a range of 1.5 to 2.0 kg / cm ² , and the pressure reduction valve 15 reduces the pressure of the discharge air from the compressor 13. The pressure is reduced to high-pressure air within a range of 0 to 5.0 kg / cm ² , and low-pressure air or high-pressure air is supplied to the air holes 8 of each core pin 7 by turning on the solenoid valves 11 and 12. The air pressures of the low-pressure air and the high-pressure air are not limited to the above values, but may be appropriately changed according to the size of the molding die Y and molding conditions.

On the other hand, the fixed mold 2 has a cavity-side mount 20 fixed to an injection molding machine (not shown) and a cavity 21 fixed to the cavity-side mount 20 opposite to the core block 5. It is configured. The cavity 21 is formed with a concave molding cavity 22 which is open to the core block 5 side. At the bottom of the molding cavity 22, two small-diameter holes 23 for molding a small-diameter projection of a molded product are formed. Is formed. The cavity 21 is closed with the core block 5 as shown in FIG.
When each of the core pins 7 is inserted into the molding cavity 22 (within the small-diameter hole 23), a resin passage 24 corresponding to the shape of the molded product is formed between the core block 5 and each of the core pins 7. .

The molding die Y of the present invention is constructed as described above. Next, a method (procedure) of molding a molded product using the molding die Y will be described with reference to FIGS. It will be described with reference to FIG. For convenience of explanation, the movable mold 1
As shown in FIG. 1, it is assumed that the fixed side mold 2 is opened (mold open) and the on-off valve 16 is opened.

First, the controller 17 executes a molding cycle and outputs a drive command to the compressor 13 of the air supply source 10 and a switching command to the solenoid valve 11. As a result, air discharged by driving the compressor 13 is introduced into the pressure reducing valve 14 through the electromagnetic valve 11 in the “ON” state. Then, the low-pressure air (1.5 to
2.0 kg / cm ² ) is passed through the air holes 8 of the core pins 7 through the pipes and the communication holes 9 of the core 4 so as to be ejected to the outside of the molding die Y (step 1 shown in FIG. 3).

Next, the controller 17 drives the actuator of the molding machine, moves the movable mold 1 to the fixed mold 2 and moves the core block 5 into the cavity 21.
By inserting the core pins 7 into the small-diameter pin holes 23, as shown in FIG.
The core block 5 (core 4) and the cavity 21 are closed (mold cloth) while forming the resin passage 24 corresponding to the shape of the molded product. At this time, each core pin 7
Is pressed against the bottom of each small-diameter pin hole 23 at such a pressure that the low-pressure air passing through the air hole 8 does not enter the resin passage 24 and is closed (step 2 shown in FIG. 3).

As described above, the core block 5 (core pin 7
When the resin passage 24 is formed by the cavity 21 and the cavity 21, the controller 17 drives an injection molding machine (not shown) to inject and fill the molten resin kneaded from the nozzle into the resin passage 24 (see FIG. 3). Step 3). At this time,
As described above, the air hole 8 of each core pin 7 is
Since the small diameter pin hole 23 is closed at the bottom, the molten resin injected into the resin passage 24 does not flow into the air hole 8 or the low-pressure air in the air hole 8 does not flow into the resin passage 24. .

Then, in a closed state (mold cloth) between the core 4 and the cavity 21, the molten resin in the resin passage 24 is cooled for a predetermined time (1-2 minutes), and the surface thereof is
It is cooled and solidified to such an extent that high-pressure air (4.0 to 5.0 kg / kg / cm ² ) does not enter the molten resin. (FIG. 3
Step 4).

After cooling and solidifying the surface of the molten resin in the resin passage 24 as described above, the controller 17 cancels the switching command of the air supply source 10 to the solenoid valve 11 and outputs "OF"
F ", and outputs a switching command to the solenoid valve 12 to bring it into the" ON "state. Thereby, the air discharged from the compressor 13 is introduced into the pressure reducing valve 15 via the electromagnetic valve 12, and the high pressure air (4.0
５5.0 kg / cm ² ) is supplied to the air hole 8 of each core pin 7 through the communication hole 9 of the pipe and the core 4. And
When high-pressure air is supplied to the air hole 8 of each core pin 7, each core pin 7 is slightly moved to the core 4 side by the pressure of the high-pressure air, and the tip of each core pin 7 and the bottom of each small-diameter pin hole 23 are moved. A gap is formed between them (step 5 shown in FIG. 3).

Thus, the high-pressure air supplied from the air supply source 10 passes through the air holes 8 of each core pin 7, flows into the resin passage 24 from the gap, and melts when passing through the air holes 8. Each core pin 7 heated with resin
Of the core block 4 and the cavity 21 and flows out of the molding die Y while removing the heat of the molten resin directly from the molten resin by flowing into the resin passage 24. The injected molten resin is cooled and solidified in a short time (step 6 shown in FIG. 3).
Further, as described above, the surface of the molten resin is cooled and solidified in advance to such an extent that high-pressure air does not enter, so that even if high-pressure air flows into the resin passage 24, entry into the molten resin is prevented. You.

When the molten resin injected into the resin passage 24 is completely cooled and solidified to form a molded product, the controller 17 drives the actuator of the injection molding machine to move the movable mold 1 to the fixed side. The core block 5 (core 4) and the cavity are opened (mould open) as shown in FIG. 1 by moving in the direction away from the mold 2.
(Step 7 shown in FIG. 3), the cavity 21
The molded product is taken out of the cavity 21 by an ejector pin (not shown) provided at (step 8 shown in FIG. 3), and the molding cycle for molding the molded product is completed.

The controller 17 does not release the switching command to the solenoid valve 12 until the molding cycle of the molded product by the molding die Y (steps 1 to 8 in FIG. 3) is executed again. Air hole 8 for each core pin 7
High-pressure air is passed through the inside (step 9 shown in FIG. 3) to ensure that each core pin 7 after molding is cooled.

As described above, according to the present invention, even if the diameter of each core pin 7 becomes 18 mm or less, air (high-pressure air) is passed through the air hole 8 to reduce the heat exchange rate as compared with the related art. By improving the temperature, the molten resin injected into the resin passage 24 can be cooled and solidified in a short time, so that the molding cycle of the molded product can be shortened. Further, since the molten resin injected into the resin passage 24 by air (high-pressure air) can be cooled and solidified, the molding die Y is made of a generally used metal material (for example, S55C) to reduce the cost. Can be. Furthermore, since the molten resin injected into the resin passage 24 by air (high-pressure air) can be cooled and solidified reliably in a short time, there is no need to deliberately shorten the cooling time unlike the conventional method, and the molded product is cooled. A portion that cannot be solidified remains locally, and molding defects such as secondary foaming and short shots do not occur, and a molded product of good quality can be molded.

[0029]

As described above, according to the injection mold of the present invention and the injection molding method using the mold, claim 1
In the injection molding die, when injecting the molten resin into the resin passage, the low-pressure air passes through the air hole, so that the low-pressure air enters the resin passage from the closed air hole.
Alternatively, the molten resin in the resin passage is prevented from entering the air hole. Also, when high-pressure air is supplied to the air holes after the surface of the injected molten resin is cooled and solidified, the blockage of the air holes is released by the high-pressure air, and the high-pressure air is released from the mold through the air holes and the resin passage. Since it flows to the outside and the high-pressure air passing through the air holes and the resin passage deprives the core pin and the molten resin of heat, the heat exchange rate can be improved, so that the molten resin can be cooled and solidified in a short time. As a result,
By shortening the cooling time of the molten resin and improving the heat exchange rate, it is possible to shorten the molding cycle of the molded product, and there are local areas where the molded product cannot be cooled and solidified due to the shortened cooling time as in the past. It is possible to prevent molding defects such as secondary foaming and short shots, and to mold a high quality molded product.

In the injection molding die according to the second aspect,
In addition to the above effects, even for a core pin having a diameter of 18 mm or less, high pressure air for cooling and solidifying the molten resin can be passed through the air holes without reducing the strength of the core pin. As described above, there is no need to change the core pin or the like that comes into contact with the molten resin to a metal material having excellent thermal efficiency, and it is possible to reduce the manufacturing cost of the injection mold.

According to the third aspect of the present invention, there is provided an injection mold.
In addition to the above-mentioned effects, it is possible to automatically switch between low-pressure air and high-pressure air that are supplied to the air holes of the core pin in accordance with the effectiveness of the molding cycle of the molded product. Therefore, the molding cycle can be further shortened.

In the injection molding method according to the fourth aspect, when injecting the molten resin into the resin passage, the low-pressure air is passed through the air hole so that the low-pressure air enters the resin passage from the closed air hole, or Is prevented from entering the air holes. Also, when high-pressure air is supplied to the air holes after the surface of the injected molten resin is cooled and solidified, the blockage of the air holes is released by the high-pressure air, and the high-pressure air is released from the mold through the air holes and the resin passage. Since it flows to the outside and the high-pressure air passing through the air holes and the resin passage deprives the core pin and the molten resin of heat, the heat exchange rate can be improved, so that the molten resin can be cooled and solidified in a short time. As a result, by shortening the cooling of the molten resin and improving the heat exchange rate, it is possible to achieve a shortening of the molding cycle of the molded product, and due to the shortening of the cooling time as in the past,
Areas that cannot be cooled and solidified remain locally in molded products,
Prevent molding defects such as secondary foaming and short shots,
High quality molded products can be molded.

According to the injection molding method of the fifth aspect, in addition to the effect of the fourth aspect, by applying a low pressing force to the core pin, it is possible to close the air hole while preventing the core pin from falling down, and it is usually used. Since the blockage of the air hole can be released by the pressure of the high-pressure air, a high-quality molded product can be economically formed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the overall configuration of an injection mold according to the present invention.

FIG. 2 is an enlarged sectional view showing a state in which a core and a cavity of an injection molding die of the present invention are closed.

FIG. 3 is a time chart for explaining the injection molding method of the present invention.

FIG. 4 is an enlarged sectional view showing the configuration of a conventional injection mold.

[Explanation of symbols]

 Y Mold for injection molding 4 Core 5 Core block 7 Core pin 8 Air hole 10 Air supply source 17 Controller 21 Cavity 24 Resin passage

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[Procedure amendment]

[Submission date] September 3, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0022

[Correction method] Change

[Correction contents]

[0022] (including the core pin 7) core block 5 as described above and to form a resin passage 24 in the cavity 21, the controller 17 the kneaded molten resin from the nozzle by driving the injection molding machine (not shown) Resin passage 24
Is injected and filled (step 3 shown in FIG. 3). At this time, since the air hole 8 of each core pin 7 is closed at the bottom of the small-diameter pin hole 23 of the cavity 21 as described above,
The molten resin injected into the resin passage 24 flows into the air holes 8 or the low-pressure air in the air holes 8
It does not flow inside.

Claims (5)

[Claims] 1. An injection mold comprising: a core having a core pin; and a cavity, wherein when the core and the cavity are closed, a resin passage corresponding to a shape of a molded product is formed inside the core and the cavity. The core pin is formed with an air hole that penetrates in the axial direction and allows air to pass therethrough. The air hole is configured such that, when the air hole is closed, low-pressure air that is lower than a predetermined pressure that passes through the inside of the air hole enters the resin passage. A mold for injection molding characterized in that the mold is closed so as not to be closed. 2. The injection mold according to claim 1, wherein the diameter of the core pin is 18 mm or less, and the diameter of the air hole is in a range of 3 to 5 mm. 3. The air hole is connected to an air supply source that switches between low-pressure air and high-pressure air, and the air supply source is switched by control means that executes a molding cycle of the molded product. The injection mold according to claim 1, wherein the mold is controlled. 4. A core having a core pin, and a cavity forming a resin passage corresponding to the shape of a molded product by closing the core, wherein an air hole is formed in the core pin in the axial direction thereof. A step of passing low-pressure air through the air hole, closing the core and the cavity to form the resin passage, and connecting the air hole to the resin passage. The step of closing the low-pressure air so as not to flow thereinto, the step of injecting the molten resin into the resin passage, and the step of solidifying the surface of the molten resin injected into the resin passage to a hardness that does not allow air to enter, Switching the air passing through the air holes from low-pressure air to high-pressure air; cooling and solidifying the molten resin with the high-pressure air passing through the air holes; Opening the core and the cavity and taking out a molded product. An injection molding method, comprising: 5. The low-pressure air passing through the air hole,
The pressure is controlled within the range of 1.5 to 2.0 kg / cm ² , and the high-pressure air passing through the air hole is controlled to 4.0 to 5.0.
5. The injection molding method according to claim 4, wherein the pressure is controlled within a range of kg / cm < ² >.