JPH08216200A - Manufacture of molding with hollow part - Google Patents

Abstract

PURPOSE: To manufacture a hollow part in which the thickness is uniform and the formation of a rib becomes constant. CONSTITUTION: A method for manufacturing a molding with a hollow part comprises the steps of casting to fill melted resin in a cavity 3 formed of a movable mold 1 and a fixed mold 2 and inserted with a slide core 4, then retreating the mold 4 from the cavity 3 to form the hollow part, injecting high pressure air in the hollow part via an air pin 6, and then extruding the hollow part to close it by a slide mold 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a molded product having a hollow portion inside, such as a television receiver set base and a desk top plate.

[0002]

2. Description of the Related Art Conventionally, in order to manufacture a molded product having a hollow portion, there are a case of blow molding and a case of injection molding.

In the case of blow molding, it is used for manufacturing a molded product having an undercut portion, for example, a hollow container such as a PET bottle, and is made hollow by pressurizing air into a cylindrical molten resin.

In the case of injection molding, it is used for manufacturing a thick flat plate and the like, and a molten resin is injected into a mold cavity and a pressurized gas is injected to form a hollow portion (see, for example, Japanese Patent Laid-Open No. Hei 10 (1999) -242242). JP-A-2-289327, JP-A-5-3
No. 01262).

[0005]

The conventional method for producing a molded article having a hollow portion by blow molding is suitable for the production of a relatively thin-walled article or one having an undercut section, but the surface Transferability is poor, and it is difficult to manufacture a product having a complicated surface shape, thin ribs, through holes, etc. Further, the molding material used is limited and the cycle time is long.

In the conventional method for producing a molded product having a hollow portion by injection molding, the problems in the blow molding can be solved to some extent, but those having a uniform wall thickness or a thin wall thickness are preferable. There was a problem that it was difficult to mold. Also, when the movable mold is moved to form a large hollow portion and ribs are formed in the hollow portion, it is difficult to form ribs of a certain size and shape at a fixed position with good reproducibility. Since it is not reliable to use it to reinforce the strength of ribs, and the shape and position of the ribs are uneven and not uniform, the formed ribs have an adverse effect on the design if the material of the molded body is transparent. There was a problem.

Further, the cooling time is long and, in addition,
When forming the large hollow portion, it is necessary to move the movable mold having a large weight, and there is also a problem that the moving force becomes large.

The present invention has a uniform wall thickness, facilitates the formation of a thin wall, and has a hollow portion capable of forming ribs with a constant size, shape, and formation position and with good reproducibility. It is intended to provide a manufacturing method of.

[0009]

In order to achieve the above object, in the method for producing a molded product having a hollow portion of the present invention, a core mold which is formed by a movable mold and a fixed mold and is capable of moving forward and backward is inserted. A step of injecting and filling a molten resin with a molten resin, a step of retracting the core mold from the cavity filled with the molten resin, and a step of injecting a fluid into a hollow portion formed by retracting the core mold , A step of closing the hollow portion into which the fluid is injected.

Further, in the step of retracting the core mold from the cavity filled with the molten resin, the core mold may be retracted by the pressure of the fluid injected into the hollow portion.

When a rib is formed in the hollow portion,
It is effective to use a core type having a comb-shaped portion or a groove portion.

Further, it is preferable that the fluid to be injected into the hollow body is allowed to flow inside the hollow body and is cooled from the inside.

[0013]

In the method of manufacturing a molded article having a hollow portion configured as described above, the core mold is retracted from the inside of the cavity before the molten resin filled in the cavity is sufficiently cooled and solidified, Since the fluid is injected into the hollow part formed by the retraction of the core mold, the pressure of the injected fluid causes the surface of the molten resin to adhere closely to the cavity wall surface, improving the transferability, and the thickness of the molten resin depends on the cavity wall surface. Since it is determined by the core mold and the core mold, it is possible to mold thin and uniform wall thickness. Furthermore, since the fluid is enclosed in the hollow part, the molded body has sufficient mechanical properties. It will be strong.

Further, since the core mold can be retracted by the pressure of the injected fluid, it is not necessary to provide a special power source for moving the core mold, and the core mold can be smoothly retracted and the fluid is injected. It can be carried out.

Further, if the comb-shaped portion or the groove portion is formed in the core mold, it is possible to easily and reproducibly provide a rib having a desired shape and a constant size at a predetermined position.

Further, when the fluid injected into the hollow body is made to flow inside the hollow body, the molten resin is also cooled from the inside of the hollow portion, so that the cycle time is shortened.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a movable type, 2 is a fixed type, 3
Is a cavity formed by the movable mold 1 and the fixed mold 2,
Reference numeral 4 is a slide-type core mold that is inserted into the cavity 3 so as to be able to move forward and backward, and 5 is a gate that injects molten resin into the cavity 3, which is formed on the fixed mold 2. Reference numeral 6 denotes an air pin for injecting a high pressure gas such as high pressure air into the cavity 3, which is provided on the fixed mold 2. Reference numeral 7 is a push-cut slide die movably provided on the movable die 1, and 8 is an air vent vibe having a valve.

First, the movable mold 1 and the fixed mold 2 are closed to form a cavity 3, and a slide core mold 4 is inserted in the cavity 3 to inject a molten resin into the cavity 3 from a gate 5. Molten resin 9 is filled around the sliding core mold 4 (see FIG. 2A).

The molten resin 9 that has been filled begins to solidify gradually from the surface portion that contacts the wall surface of the cavity 3 and the side wall portion that contacts the slide core mold 4. The child mold 4 is retracted, and high-pressure air is injected from the air pin 6 into the hollow portion 10 formed in the molten resin 9 by the retracting of the slide core mold 4 (FIG. 2).
(B)).

Then, when the sliding core die 4 has been retracted from the cavity 3 and the hollow portion 10 is filled with high-pressure air (see FIG. 2 (c)), the push-cut slide die 7 is lowered. Then, the hollow portion 10 is opened (FIG. 2D).
Then, the molten resin 9 in the cavity 3 is cooled and solidified, the movable mold 1 and the fixed mold 2 are opened, and the resin molded body is taken out to obtain a flat resin molded body 11 having a hollow portion 10. can get.

The wall thickness of the obtained resin molding 11 is formed by the distance between the slide core mold 4 and the wall surface of the cavity 3, so that the wall thickness is the same as that of the slide core mold 4. The thickness can be made uniform and the thickness can be made uniform. By changing the size of the slide core mold 4, the size of the wall thickness can be changed, and a thin wall can be formed.

Further, since the hollow portion 10 is also cooled by the high pressure air which is press-fitted, the cooling time for solidifying the molten resin is shortened and the cycle time can be shortened. Also,
Since the molten resin 9 is pressed against the wall surface of the cavity 3 by the air pressure injected into the hollow portion 10, the sink marks and the like are eliminated and the transferability is improved. Furthermore, instead of high-pressure air, foaming of urethane or the like is performed inside the hollow portion 10. By injecting a conductive resin, a heat insulating member such as a refrigerator door can be easily formed.

Further, the tip of the sliding core mold 4 is shown in FIG.
As shown in FIG. 2, when the comb-shaped structure having the plurality of cutouts 12 is formed, the molten resin is filled in the portion corresponding to the cutouts 12. A plate-shaped resin molded body 11 having a rib 13 and a hollow portion 10 defined by the rib 13.
Is obtained (see FIG. 4).

Further, as shown in FIG. 5, a plurality of linear groove portions 14 are formed on the upper surface or the lower surface of the tip of the sliding core mold 4.
When the resin is formed, a flat resin molded body 1 having a hollow portion 10 in which a portion corresponding to the groove 14 is filled with a molten resin and a rib 15 extending to an intermediate portion is suspended or planted
1 is obtained (see FIG. 6).

In this case, the size, shape, forming position, etc. of the rib 13 formed in the hollow portion 10 are determined by the notch 12 or the groove portion 14 provided in the sliding core mold 4. The reproducibility is always constant and good, the reliability of mechanical strength is improved, and even if the resin molded body 11 is a transparent material, the internal appearance is good and the design is good.

Further, the slide-type core mold 4 can be retracted by a separately provided power source, but it can also be carried out by the pressure of the high-pressure air injected into the hollow portion 10. In this case, The relative movement of the retracting movement of the sliding core die 4 and the injection of high-pressure air into the hollow portion 10 allows the sliding movement of the sliding core die 4 and the injecting of high-pressure air to be performed smoothly. Is possible.

Further, when high-pressure air injected into the hollow portion 10 is extracted from the air vent pipe 8 to form an air flow from the air pin 6 to the air vent pipe 8 in the hollow portion 10, the molten resin is cooled by the high pressure air. Efficiency is improved and solidification time is further shortened.

[0028]

Since the present invention is constructed as described above, it has a uniform wall thickness and a large mechanical strength.
Even when the rib is formed inside the hollow portion, the size, shape, and position of the rib are constant, and a molded product having a hollow portion having a great design effect can be manufactured.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a molding apparatus used in an example of a method for producing a molded product having a hollow portion according to the present invention.

FIG. 2 is a schematic diagram illustrating the manufacturing method.

FIG. 3 is a perspective view of a main part of the molding apparatus in FIG.

FIG. 4 is a perspective view showing a part of a molded body having a hollow portion.

5 is a perspective view showing a modified example of the main part of the molding apparatus in FIG.

FIG. 6 is a perspective view showing a part of a molded product molded by using the molding device in FIG.

[Explanation of symbols]

 1 Movable type 2 Fixed type 3 Cavity 4 Sliding core type 5 Gate 6 Air pin 7 Push-cut slide type 8 Air vent pipe 9 Molten resin 10 Hollow part 12 Notch part 14 Groove part

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Claims (5)

[Claims] 1. A step of injecting and filling a molten resin into a cavity formed by a movable die and a fixed die and having a retractable core die inserted therein, and retracting the core die from the cavity filled with the molten resin. A method for producing a molded article having a hollow portion, comprising: a step of injecting a fluid into a hollow portion formed by retracting the core mold; and a step of closing the hollow portion into which the fluid is injected. 2. The method for producing a molded article having a hollow portion according to claim 1, wherein the core mold is retracted by a fluid injected into the hollow portion. 3. The method for producing a molded product having a hollow portion according to claim 1, wherein a core mold having comb-shaped portions is used. 4. The method for producing a molded product having a hollow portion according to claim 1, wherein a core mold having a groove portion formed at the tip is used. 5. The method for producing a molded article having a hollow portion according to claim 1, wherein a fluid is circulated in the hollow portion.