JPH08103922A - Mold for injection molding and injection molding method - Google Patents

Abstract

PURPOSE: To obtain a molded form which is easily removed from a mold for injection molding and has a through hole or a non-penetration hole by providing a pin for forming a hole at the font in the cavity of the mold and providing a specific gap between the side face of a movable die and the inner surface of the mold. CONSTITUTION: The gap 9 of the degree in which molten resin is not introduced is provided between the inner surface 2a of the cavity 2 for slidably supporting the movable die 3 of molds 1, 1' and the side face 3a of the die 3. The entirety or a part of the inner surface 2a of the cavity of the gap range is so formed with a mirror surface or an embossed surface as to obtain a molded form having an excellent external surface without bringing the inner surface 2a of the cavity into contact with the side face 3a of the die 3. A blank plug 7 which becomes a stopper when the die 3 is retreated is provided at the opposite surface to the cavity, and a pin 4 for forming a hole at the molded form is provided at the plug 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding die and an injection molding method, and more specifically, an injection molding die used for molding a molded product having through holes or non-through holes at appropriate positions. A mold and an injection molding method using the same.

[0002]

2. Description of the Related Art Conventionally, in order to manufacture a shaft such as a mechanical pencil or a ballpoint pen, a test tube or the like, a product having a hole having a through hole or a non-through hole at an appropriate position has been formed. Therefore, these molded products were molded using a mold having a structure in which the fixing pin 4 as shown in FIGS. 6 and 7 was fixed in the cavity of the mold. However, when molding is performed using this mold, as shown in FIG.
As shown in Fig. 7, the pressure when the molten resin is injected tilts the pin 4 fixed in the cavity, and as a result, the hole position of the molded product is displaced as shown in Fig. 7, and it becomes difficult to remove it from the mold. There was a problem. Further, if the product thickness around the hole is non-uniform, welds will occur in the thin part, and the mechanical strength will decrease.

In order to solve these problems, there is provided a mold having a cylindrical movable part around the hole forming fixed pin, the surface of which moves in contact with the molten material in response to the injection of the molten material into the mold. There has been proposed a method of forming a product with a hole that penetrates or does not penetrate in an appropriate position. However, in this method, since the cylindrical movable part and the cylindrical mold surface (cavity inner surface) rub against each other, the cylindrical mold surface forming the external surface of the molded product is scratched and the product surface is It could not be applied to the field where processing such as mirror surface or textured surface is required.

Therefore, according to the present invention, the external surface of the molded product has an excellent mirror surface or textured surface without scratches, and there is no displacement of the hole position and it is easy to take out from the mold. An object of the present invention is to provide an injection molding die and an injection molding method capable of obtaining a molded product having a non-through hole.

[0005]

The present inventors have arrived at the present invention as a result of intensive studies to achieve the above object.

That is, the present invention relates to an injection molding die for molding a molded product having through holes or non-through holes at appropriate positions, wherein the molded product is placed in the cavity of the injection molding mold. A pin for forming a hole is provided, and a movable mold moving by a molten resin injected around the pin is slidable, and a side face of the movable mold and a mold inner face forming a cavity. Between 20 and 100 μm
And a mold for injection molding, in which a molten resin is injected into the mold, and the movable mold is formed by the injected molten resin. Injecting molten resin into the cavity while gradually retracting the pressed movable mold along the pin for forming a hole in the molded product, and the injection molding method is characterized by molding. is there.

The present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of an injection molding die used to obtain a molded product having a through hole or a non-through hole. In the figure, 1 and 1 ′ are molding dies,
The cavity 2 is formed in this. A movable die 3 is provided in the cavity 2 so as to be slidable. At one end of the movable mold 3, a collar 3 serving as a stopper is provided.
b. In addition, the movable molds 3 of the molding molds 1 and 1 '
A step 6 is formed in the cavity 2 for slidably supporting the mold 3, and the step 3 is engaged with the collar 3b of the movable mold 3 so that the end of the movable mold 3 substantially coincides with the end surface of the cavity 2. Further, between the inner surface 2a of the movable mold 3 and the mold inner surface 2a of the cavity 2 that slidably supports the movable mold 3 of the molding dies 1 and 1 ', a gap 9 that does not allow molten resin to enter. Is provided. Mold inner surface 2a of the cavity in this gap range
The whole or a part of the mold is processed such as a mirror surface and a textured surface so that the mold inner surface 2a of the cavity and the side surface 3a of the movable mold 3 do not touch each other and a molded product having an excellent appearance is obtained. Has been done. The gap 9 is 20 to 100 μm
Is preferable, and more preferably 30 to 80 μm. If the spacing of the gap 9 exceeds this range, the molten resin is likely to enter the gap 9, while if it is narrower than this range, rubbing easily occurs and a molded product having no scratch and excellent appearance cannot be obtained. Further, a blind plug 7 which is a stopper when the movable mold 3 retracts is provided on the surface of the molding dies 1 and 1 ′ opposite to the cavity. The blind plug 7 is provided with a pin 4 for forming a hole in the molded product. The pin 4 is slidable in the hole of the movable mold 3. A coil spring 8 as an elastic means is inserted between the blind plug 7 and the movable mold 3 to constantly press the movable mold 3 toward the cavity 2. Movable mold 3
Is generally formed in a cylindrical shape, but may be changed to a hexagonal shape, a quadrangular shape, an elliptical shape, or the like, if desired.

Next, an example of an injection molding method for obtaining a molded product having through holes or non-through holes at appropriate positions using the above injection molding die will be described. FIG. 2 is a diagram for explaining an example of an injection molding method of a molded product having a non-through hole. First, in molding, FIG. 2 (a)
As described above, the upper surface of the pin 4 for forming the non-through hole and the upper surface of the movable mold 3 are aligned, and then the molten resin 5 is injected into the cavity 2 as shown in FIG. The movable mold 3 is pushed back by the pressure of the injected resin,
After the state of FIG. 2C, the state of FIG. 2D is reached, and the collar 3a of the movable mold 3 enters until it contacts the blind plug 7. Then, the injection of the molten resin is stopped and the mixture is cooled and solidified. If this is taken out from the molding dies 1, 1 ', a resin molded product having a non-through hole at an appropriate position as shown in FIG. 3 and at the same time having a mirror surface or a textured surface on the outer periphery of the molded product can be obtained. Since this resin molded product is formed by the resin entering by the gradual retraction of the movable mold, no weld is generated, and since the pin 4 is supported by the movable mold 3, the bending stress applied to the pin 4 is small, The displacement of the position is also suppressed. On the other hand, when molding a molded product having a through hole, as shown in FIG. 4, the pin 4 penetrates the movable mold 3 and is positioned so as to be in contact with the inner surface of the mold of the cavity 2, and then melted. It can be obtained by injecting and molding a resin.

[0009]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

The transfer state of the surface of the molded product in the resin molded product molded by the molding die of the present invention and the resin molded product molded by the conventional molding die was observed. The molded product used was obtained with the mold and molding conditions shown below, and had the dimensions shown in FIG. Two types of molding materials used were Diapet (registered trademark) 3001 (ABS resin) and Acrypet (registered trademark) VH (acrylic resin) (both manufactured by Mitsubishi Rayon Co., Ltd.).

Mold and Molding Conditions (1) Mold Used Mold of the present invention: A mold having the structure shown in FIG. 1 was used.
The gap between the movable mold and the inner surface of the cavity was 50 μm, and the inner surface of the cavity was mirror-finished. Conventional mold: A mold having the structure shown in FIG. 1 was used. The gap between the movable mold and the inner surface of the cavity was 10 μm, and the inner surface of the cavity was mirror-finished. (2) Molding conditions As a molding machine, IS-50EP manufactured by Toshiba Machine Co., Ltd. was used. The molding conditions were set as shown in Table 1 below.

[0012]

[Table 1]

The transferability of the surface of the obtained injection-molded article was observed. Table 2 shows the results.

[0014]

[Table 2]

[0015]

EFFECTS OF THE INVENTION According to the present invention, a molded product having an excellent appearance such as a mirror surface or a textured surface without scratches on the outer surface of the molded product and having a through hole or a non-through hole at an appropriate position where the hole position is not displaced. Can be obtained. In addition, by using the injection molding method of the present invention, it becomes possible to perform texturing and character processing on the surface of the molded product, which was not possible by extrusion molding, and the degree of freedom in designing the product is expanded. Molding,
For example, the mechanical axis of a mechanical pencil or a ballpoint pen can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of an injection molding die of the present invention.

FIG. 2 is a diagram for explaining the injection molding method of the present invention.

FIG. 3 is a cross-sectional view showing the shape of a resin molded product having a non-through hole obtained by the injection molding method of the present invention.

FIG. 4 is a diagram for explaining a molding method of a resin molded product having a through hole.

FIG. 5 is a diagram showing dimensions of molded test pieces used in Examples and Comparative Examples.

FIG. 6 is a diagram for explaining a displacement of a hole position that occurs in a conventional injection molding die.

FIG. 7 is a diagram for explaining a shift in hole position of a molded product obtained by using a conventional mold.

[Explanation of symbols]

 1, 1'Molding mold 2 Cavity 3 Movable mold 4 Pins 5 Molten resin 6 Steps 7 Blind plug 8 Coil spring

Claims (3)

[Claims] 1. A mold for injection molding for molding a molded article having through holes or non-through holes at appropriate positions, comprising:
A pin for forming a hole in a molded product is provided in the cavity of the injection molding die, and a movable die moved by a molten resin injected around the pin is slidable and An injection-molding die, characterized in that it is arranged so that a gap of 20 to 100 μm is formed between the side surface of the movable die and the inner surface of the die forming the cavity. 2. The whole or a part of the inner surface of the mold of the cavity is subjected to a surface treatment such as a mirror surface or a textured surface in the range of the gap between the side surface of the movable mold and the inner surface of the mold constituting the cavity. The mold for injection molding according to claim 1. 3. Using the mold according to claim 1 or 2,
Molten resin is injected into the mold, the movable mold is pressed by the injected molten resin, and the pressed movable mold is gradually retracted along pins for forming holes in the molded product. An injection molding method, which comprises filling a cavity with a molten resin and molding the resin.