JPH0788913A - Injection molding method and injection mold - Google Patents

Abstract

PURPOSE:To enhance the dimensional accuracy of a molded product and to suppress the generation of flash by allowing mold clamping load to act on the part on which the molding space of a molded product is projected on the other surface of a cavity die and the part on which the molding space of the molded product is projected on the other surface of a core die main body. CONSTITUTION:A cavity die attaching plate 55 is positioned at the part on which the molding space 11 of a molded product is projected on the right side surface of a cavity die 3. When the cavity die 3 and a core die main body 5 are clamped by the fixed part 19 and movable part 31 of a mold clamping device, mold clamping load can be respectively allowed to locally act on the part on which the molding space 11 of the molded product is projected on the left side surface 3a of the cavity die 5 and the part on which the molding space 11 of the molded product is projected on the right side surface 5a of the core die main body 5. The peripheral part of the molding space 11 of the molded product can be clamped from the outside by sufficient force and the dimensional accuracy of the molded product can be enhanced and the generation of flash can be suppressed to the utmost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method and an injection molding die.

[0002]

2. Description of the Related Art Referring to FIG. 5, a conventional injection molding die 1 includes a cavity die 3 and a left-right direction that approaches and separates from the cavity die 3 (left-right direction in FIG. 5).
The movable core die main body 5 is provided so as to oppose to the left and right. The cavity die 3 includes a core accommodating portion 7, and the core die body 3 integrally includes a core 9. Then, when the left side surface 3a of the cavity die 3 and the right side surface 5a of the core die body 5 are joined, a molded product molding space 11 having a U-shaped cross section is formed between the core accommodating portion 7 and the core 9. Is configured.

A guide pin 13 is provided on the core die body 5.
Is provided so as to protrude from the right side surface 5a, and the guide pin 13 is supported by a guide pin bush 15 provided in the cavity die 3 so as to be movable in the left-right direction.

A cavity die mounting plate 17 is provided on the right side surface 3b of the cavity die 3, and the cavity die mounting plate 17 is constructed so as to be attachable to and detachable from a fixing portion 19 of the mold clamping device. The cavity die mounting plate 1
A sprue bush 23 having a sprue 21 and a locate ring 25 are provided at the center of the sprue 2.
1 communicates with a molded product molding space 11.

A core die mounting plate 29 is provided on the left side surface 5b of the core die body 5 with a spacer 27 interposed therebetween, and the core die mounting plate 29 is configured to be attachable to and detachable from a movable portion 31 of the mold clamping device. is there. In addition, this movable part 31
Is configured to be movable in the left-right direction toward and away from the fixed portion 19 by the action of hydraulic pressure.

An ejector space 33 is formed between the left side surface 5b of the core die body 5 and the right side surface of the core die mounting plate 29, and an ejector space 33 is provided in the ejector space 33 for releasing a molded product from the core 9. A device 35 is provided.

Explaining the ejector device 35 in detail, an ejector plate 37 formed by joining two plates is provided in the ejector space 33, and the ejector plate 37 has an ejector pin 39 protruding rightward. The return pin 41 is integrally provided.
The ejector pin 39 is supported by a guide hole 43 provided at an appropriate position around the core 9 in the core die body 5 so as to be movable in the left-right direction, and the return pin 41 is provided at a proper position in the core die body 5. It is movably supported in the left and right directions. Here, the ejector plate 37 can be moved to the right by the action of the pushing rod 47, and the pushing rod 47 can be inserted into and removed from the through hole 49 provided in the core die mounting plate 29.

A plurality of stopper pins 51 that can come into contact with the left side surface of the ejector plate 37 are provided at appropriate positions on the core die mounting plate 29 so as to be positionally adjustable in the left-right direction. Further, between the ejector plate 37 and the core die body 5, a spring capable of biasing the ejector plate 37 to the left and an elastic body (not shown) such as rubber may be provided.

When the injection molding die 1 is used to perform injection molding with the above structure, first, the mold is opened (in this case, the return pin 41 is usually the right side surface 5a of the core die body 5).
The movable part 31 of the mold clamping device is moved to the right toward the fixed part 19. As a result, the core die body 5 is moved to the cavity die 3
Move to the right to approach the core die body 5
The right side surface 5a of the mold is joined to the left side surface 3a of the cavity die 3, and the mold clamping can be performed by the fixed portion 19 and the movable portion 31 of the mold clamping device. At this time, the mold clamping load from the fixing portion 19 acts on the right side surface of the cavity mounting plate 17 substantially uniformly, and further, as shown by a plurality of arrows in FIG.
It acts as a substantially uniform load on the right side surface 3b. on the other hand,
The mold clamping load from the movable part 31 acts as a substantially uniform load on the left side surface of the core die mounting plate 29, and the core die mounting plate 29 and the spacer 27 are attached to the core die mounting plate 29 as shown by a plurality of arrows in FIG. It acts on the left side surface 5b of the main body 3 in the vicinity of the peripheral portion.

In the mold closing step, the return pin 41 is pushed to the left by the cavity die 3 and is set in the right side surface 5a of the core die body 5.

Fixed part 19 and movable part 31 in the mold clamping device.
After the mold is clamped by, the melt plasticized material (for example, plastic, aluminum, etc.) is injected and filled into the molded product molding space 11 through the sprue 21.

After the above material is cooled in the molded product molding space 11, the movable part 31 is moved leftward away from the fixed part 19 to move the core die body 5 to the cavity die 3. Move it to the left to separate it, and open the mold. After the mold is opened, the push rod 47 is inserted into the through hole 49 to remove the ejector plate 37.
Is moved to the right with respect to the core die body 5 to move the ejector pin 39 to the right side surface 5a of the core die body 5.
The molded product is separated from the core 9 by releasing it from the core 9 (mold release).
Excuse me.

[0013]

By the way, in the case of performing injection molding with the conventional injection molding die 1, the mold clamping load by the fixing portion 19 in the mold clamping device is passed through the cavity die mounting plate 17 to the cavity die. Right side of 3
b acting almost uniformly on the core die main body 5 through the core die mounting plate 29 and the spacer 27.
Since it acts on the peripheral portion of the above, the force for tightening the peripheral portion of the molded product forming space 11 from the outside is not sufficient. On the other hand, when the melted plasticized material is injected and filled into the molded product molding space 11, the molded product molding space 11 has a very high pressure, and the molded product molding space 1 is fed from the inside of the molded product molding space 11.
A large force acts to release the tightening of the peripheral portion of 1. Therefore, the core accommodating portion 7 and the core 9 that form the molded product molding space 11 are deformed, which causes a defect in the dimensional accuracy of the molded product, and the left side surface 3 of the cavity die 3.
a and the right side surface 5a of the core die body 5 cannot be maintained in a joined state,
There has been a problem that the material in the molded product molding space 11 enters between the left side surface 3a of the cavity die 3 and the right side surface 5a of the core die body 5 to cause burrs.

Therefore, an object of the present invention is to provide an injection molding method and an injection molding die capable of clamping the peripheral portion of the molded product molding space 11 from the outside with a sufficient force.

[0015]

In order to solve the above-mentioned conventional problems, in the present invention, as a first means, one surface of a cavity die having a core accommodating portion and a core die main body having a core are provided. After one side is joined and the mold is clamped, injection molding is performed by injecting and filling a melted plasticized material into the molded product molding space formed between the core housing and the core. In the method, a mold clamping load is locally applied to a portion of the other surface of the cavity die onto which the molded product molding space is projected and a portion of the other surface of the core die body onto which the molded product molding space is projected. It is characterized by performing mold clamping.

As a second means, a cavity die having a core accommodating portion and a core die body having a core are provided so as to face each other, and when one surface of the cavity die and one surface of the core die body are joined together, the core A molding space is formed between the accommodating portion and the core, a cavity die mounting plate is provided on the other surface of the cavity die, and a spacer is sandwiched between the other surface of the core die body. In the injection molding die, a core die mounting plate is provided, and one mounting plate is configured to be attachable / detachable to / from a fixed portion in the mold clamping device, and the other mounting plate is configured to be detachably attached to a movable part. The cavity die mounting plate is located on a portion of the other surface of the molded product projected onto the molding space, and the molding is performed on the other surface of the core die body. The spacer portion the projection of the molding space is characterized by comprising configured to be located.

As a third means, in addition to the constituent features of the second means, the shape of the working surface of the cavity die mounting plate is
The shape of the working surface of the spacer is similar to the shape of the part of the other surface of the cavity die that projects the molding product molding space, and the shape of the part of the other surface of the core die body that projects the molding product molding space. It is characterized by being similar to.

Here, the working surface of the cavity mounting plate is
The surface on which the mold clamping load applied by the mold clamping device is applied to the cavity die, and the acting surface of the spacer is the surface on which the mold clamping load applied by the mold clamping device is applied to the core die body. Also,
Similarity is meant to include something similar to similarity.

As a fourth means, in addition to the constituent features of the third means, the area of the working surface of the cavity die mounting plate is
The area of the working surface of the spacer is almost the same as the area of the part of the other surface of the cavity die projected from the molded product molding space, and the area of the working surface of the spacer projects the molded product molding space on the other surface of the core die body. It is characterized in that it is approximately half or approximately the same as the area of the part.

As a fifth means, a cavity die having a core accommodating portion and a core die body having a core are provided so as to face each other, and when one surface of the cavity die is bonded to one surface of the core die body, the core A molding space is formed between the accommodating portion and the core, a cavity die mounting plate is provided on the other surface of the cavity die, and a spacer is sandwiched between the other surface of the core die body. A core die main body, comprising a core die mounting plate, one mounting plate being configured to be attachable to and detachable from a fixed portion of a mold clamping device, and the other mounting plate being configured to be detachable from a movable portion. Is provided with a pressing member that presses a portion of the other surface of the molded product projected onto the molding space toward the cavity die.

As a sixth means, in addition to the constituent features of the fifth means, the shape of the working surface of the pressing member is similar to the shape of the portion of the other surface of the core die body onto which the molded product molding space is projected. Is characterized in that.

Here, the acting surface of the pressing member means a surface on which the mold clamping load by the pressing member acts on the core die body.

As the seventh means, in addition to the constitutional requirements of the sixth means, the area of the working surface of the pressing member is almost the same as the area of the portion of the other surface of the core die main body which projects the molding space. It is characterized by being half to almost the same.

[0024]

In the above construction, under the mold closing condition, the movable part of the mold clamping device is moved in the direction approaching the fixed part, and the other mounting plate is moved in the approaching direction. As a result, the core die main body is brought relatively close to the cavity die, one surface of the core die main body and one surface of the cavity die are joined, and mold clamping is performed by the fixed portion and the movable portion of the mold clamping device. At this time, the second,
According to the third and fourth means, the mold clamping load from the fixing portion locally acts on the other surface of the cavity die on the other surface of the cavity through which the molding product molding space is projected, via the cavity mounting plate.
The mold clamping load from the movable portion locally acts on a portion of the other surface of the core die main body, which is a projection of the molding space, through the core die mounting plate and the spacer. Therefore, the peripheral portion of the molded product molding space can be tightened from the outside with a sufficient force.

According to the fifth, sixth and seventh means,
After the mold is clamped by the fixed part and the movable part in the mold clamping device, the pressing member presses the part of the other surface of the core die main body onto which the molded product molding space is projected, toward the cavity die side. As a result, the mold clamping load by the pressing member is locally applied to the part of the other surface of the core die body where the molded product molding space is projected and the part of the other surface of the cavity die where the molded product molding space is projected. Thus, the peripheral portion of the molded product molding space can be tightened from the outside with sufficient force.

After the mold clamping load is locally applied, the molten and plasticized material is injection-filled into the molding space of the molded product. Then, after the material is cooled in the molding space, the movable part is moved in the direction away from the fixed part, and the other mounting plate is moved in the direction away from the fixed part.
As a result, the core die body is relatively moved away from the cavity die, and the die is opened.

[0027]

EXAMPLE A first example will be described with reference to FIG. The injection molding die 53 according to the first embodiment has the same configuration as the conventional injection molding die 1 shown in FIG. 5 except for the characteristic portion, and only the characteristic portion will be described in detail below. In addition, about the same components as the appropriate components of the injection molding die 1 in the components of the injection molding die 53, the same reference numerals as the corresponding components in FIG. Will be omitted.

The cavity die mounting plate 55 in the injection molding die 53 according to the first embodiment is different from the cavity die mounting plate 17 in the conventional injection molding die 1 on the right side of the cavity die 3 (right side in FIG. 1). ) It is configured so as to be located at a portion of the surface 3b where the molded product molding space 11 is projected. Therefore, when the core accommodating portion 7 is provided in, for example, the left central portion of the cavity die 3, the cavity die mounting plate 55 is provided in the right central portion of the right side surface 3b of the cavity die 3.

The shape of the working surface of the cavity die mounting plate 55 is similar to the shape of the portion of the right side surface 3b of the cavity die 3 onto which the molded product molding space 11 is projected (including similar shapes). The area of the working surface 55a of the mounting plate 55 is configured to be approximately half or almost the same as the area of the projected portion. Here, the acting surface of the cavity die mounting plate 55 refers to the left side surface that applies the mold clamping load by the fixing portion 17 in the mold clamping device to the cavity die 3.

Further, the injection molding die 5 according to the first embodiment.
Unlike the spacer 27 in the conventional injection molding die 1, the spacer 57 in FIG. 5 is configured to be located in the portion of the left side surface 5b of the core die body 5 where the molded product molding space 11 is projected. Therefore, when the core 9 is provided in, for example, the right center portion of the core die body 5, the spacer 57 is provided in the center portion of the left side surface 5b of the core die body 5.

The shape of the working surface 57 of the spacer 57 is as follows.
Molded product molding space 1 on the left side surface 5b of the core die body 5
1 is similar to the shape of the projected portion (including similar shapes), and the area of the working surface of the spacer 57 is configured to be approximately half or almost the same as the area of the projected portion. Here, the working surface of the spacer 57 refers to the right side surface that causes the mold clamping load by the movable portion 31 in the mold clamping device to act on the core die body 5, and in the first embodiment, the area of the working surface of the spacer 57 is the cavity. Die mounting plate 5
The area of the working surface of No. 5 is almost the same.

As described above, the reason why the areas of the working surface of the cavity die mounting plate 55 and the working surface of the spacer 27 are set to be approximately half or almost the same as the projected portion of the molded product molding space 11 is as follows. This is because the result was taken into consideration.

That is, under a predetermined condition, the working area of the mold clamping load / the projected area of the molding space × 100 (%), i) the displacement of the inner thickness at the joint surface between the cavity die 3 and the core die body 5, ii. 3) The relationship between the displacement amount of the outer thickness of the joint surface and iii) the displacement amount of the thickness of the central portion of the molded product molding space 11 is shown in FIG. And FIG.
As shown in, the working area / the projected area of the molding space × 100
When the (%) is 50 to 100%, the displacement amount of the outer thickness on the joint surface is somewhat generated, but the displacement amount of the inner thickness on the joint surface is 0, and the molded product forming space 11
It was possible to obtain the experimental results that the amount of displacement of the thickness of the central part of the was relatively small. Here, the predetermined condition is a cylindrical cavity die 3 and a core die body 5 as shown in FIG.
Φ600 × 300, the molded product molding space 11 (molded product) has a size of φ300 × 3, the total pressure in the molded product molding space 11 is 51.5 MN, and the mold clamping load is 52 MN. Note that FIG. 4A shows a state in which the operating area / projected area of the molding space × 100 (%) is 400%, and FIG.
The state when 100 (%) is 100% is shown.

Explaining the case of performing the injection molding using the injection molding die 53, first, in the mold open state,
The movable part 31 of the mold clamping device is moved to the right toward the fixed part 19. As a result, the core die body 5 is moved to the right toward the cavity die 3 so that the right side surface 5a of the core die body 5 moves toward the cavity die 3.
Then, the cavity die 3 and the core die main body 5 are clamped by the fixed portion 19 and the movable portion 31 in the mold clamping device. At this time, as shown by a plurality of arrows in FIG. 1, the mold clamping load from the fixing portion 19 is locally applied to a portion of the right side surface 3b of the cavity die 3 where the molded product molding space 11 is projected via the cavity mounting plate 55. The mold clamping load from the movable part 31 acts on the core die mounting plate 2
9, the left side 5b of the core die body 5 via the spacer 57
It locally acts on the portion of the molded product in which the molding space 11 is projected. Therefore, the peripheral portion of the molded product molding space 11 can be tightened from the outside with a sufficient force.

After the mold clamping load is locally applied, a material such as melt-plasticized plastic is injected and filled into the molded product molding space 11. Then, after the above material is cooled in the molded product molding space 11, the movable part 31 is moved leftward away from the fixed part 19,
The core die body 5 is moved leftward away from the cavity die 3 to open the mold. Then, the ejector device 35 is appropriately operated to separate (release) the molded product from the core 9.

According to the first embodiment as described above, when the cavity die 3 and the core die body 5 are clamped by the fixed part 19 and the movable part 31 in the mold clamping device, a molded product on the left side surface 3a of the cavity die 3 is formed. The mold clamping load can be locally applied to the part where the molding space 11 is projected and the part where the molded product molding space 11 is projected on the right side surface 5a of the core die body 5, and the peripheral part of the molded product molding space 11 is outside. Can be tightened with sufficient force. Therefore, even when a large force for releasing the mold clamping is applied from the inside of the molded product molding space 11 by injecting and filling the melt-plasticized material into the molded product molding space 11, The deformation of the core housing 7 and the core 9 forming the molding space 11 can be suppressed as much as possible to improve the dimensional accuracy of the molding, and the left side surface 3a of the cavity die 3 and the core die body 5 can be improved. The right side surface 5a can maintain this joining state and suppress the occurrence of burrs as much as possible.

Next, a second embodiment will be described with reference to FIG. The injection molding die 59 according to the second embodiment is the same as the conventional injection molding die 1 shown in FIG. 5 except for the characteristic portion, and only the characteristic portion will be described in detail below. In addition, about the same components as the appropriate components of the injection molding die 1 in the components of the injection molding die 59, the same numbers as the corresponding components in FIG. Will be omitted.

The injection molding die 59 according to the second embodiment is
Unlike the conventional injection molding die 1, a pressing device 61 that presses a portion of the left side (left side in FIG. 2) 5b of the core die body 5 onto which the molded product molding space 11 is projected rightward (cavity die 3 side). I have it. This pressing device 61
More specifically, the core die mounting plate 29 is provided with a hydraulic cylinder 65 having a piston rod 63 that is movable in the left-right direction.
A pressing plate 67 that presses the projected portion to the right is provided at the tip of the. The shape of the working surface of the pressing plate 67 is similar to the shape of the portion of the left side surface 5b of the core die body 5 onto which the molded product molding space 11 is projected (including similar shapes), and the working surface of the pressing plate 67 ( Similar to the first embodiment, the area of the right side surface is designed to be approximately half or almost the same as the area of the projected portion in consideration of the experimental results shown in FIG.

The case of performing the injection molding using the injection molding die 59 will be briefly described. First, the cavity die 3 and the core die main body by the movable part 31 and the fixed part 19 in the mold clamping device under the mold open state. Perform mold clamping of 5. At this time, similarly to the mold clamping with the conventional injection molding mold 1, the mold clamping load from the fixing portion 19 is equal to the cavity mounting plate 1.
Acting on the right side surface 3b of the cavity die 3 as a substantially uniform load via the core die 7, and the mold clamping load from the movable part 31 is passed through the core die mounting plate 29 and the spacer 27.
It acts on the left side surface 5b near the periphery.

Fixed part 19 and movable part 31 in the mold clamping device.
After performing the mold clamping by appropriately operating the hydraulic cylinder 65 in the pressing device 61, the pressing plate 67 causes the portion of the left side surface 5b of the core die body 5 where the molded product forming space 11 is projected to the right side (the cavity die 3).
Side). As a result, as shown by a plurality of arrows in FIG. 2, a portion of the left side surface 5b of the core die body 5 where the molded product molding space 11 is projected and a portion of the right side surface 3b of the cavity die 3 where the molded product molding space 11 is projected. On the other hand, the mold clamping load by the pressing plate 67 can be locally applied. Therefore, the peripheral portion of the molded product molding space 11 can be tightened from the outside with a sufficient force.

After the mold clamping load applied by the pressing plate 67 is locally applied, the melt-plasticized material is injected and filled into the molded product molding space 11. Then, after the above material is cooled in the molded product molding space 11, the mold is opened and the molded product is released from the core 9.

As described above, also in the second embodiment, the same effect as that of the first embodiment can be obtained.

The present invention is not limited to the description of the above-mentioned embodiments, and for example, the cavity die 3 can be moved in the left-right direction instead of the core die body 5, or the core die body 5 can be moved in the left-right direction. The present invention can be implemented in various other modes by making an appropriate change such as making it movable in the vertical direction instead of making it movable.

[0044]

As can be understood from the above description of the embodiments, according to the present invention, when the cavity die and the core die main body are clamped, the portion of the other surface of the cavity die on which the molded product molding space is projected. The mold clamping load can be locally applied to the part of the other surface of the core die body onto which the molded product molding space is projected, and the peripheral part of the molded product molding space can be clamped with sufficient force from the outside. Therefore, by injection-filling the melt-plasticized material into the molded product molding space, even if a large force for releasing the mold clamping is applied from the inside of the molded product molding space, Deformation of the core accommodating part and the core to be formed can be suppressed as much as possible, and the dimensional accuracy of the molded product can be improved, and the one side of the cavity die and the one side of the core die body can be kept in contact with each other to prevent burrs. Occurrence can be suppressed as much as possible.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an injection molding die according to a first embodiment.

FIG. 2 is a sectional view of an injection molding die according to a second embodiment.

FIG. 3 is a graph showing experimental results.

FIG. 4 is a model diagram of experimental contents.

FIG. 5 is a sectional view of a conventional injection molding die.

[Explanation of symbols]

 3 Cavity Die 5 Core Die Main Body 7 Core Housing 9 Core 11 Molded Product Molding Space 19 Fixed Part 29 Core Die Mounting Plate 31 Movable Part 53 Injection Molding Mold 55 Cavity Mounting Plate 57 Spacer 59 Injection Molding Mold 67 Pressing Plate

Claims (7)

[Claims] 1. A molded product formed between the core accommodating portion and the core after one surface of a cavity die having a core accommodating portion and one surface of a core die main body having a core are joined and clamped. In an injection molding method of performing injection molding by injection-filling a melted plasticized material into a molding space, a portion of the other surface of the cavity die onto which the molded article molding space is projected and the core die main body An injection molding method, characterized in that a mold clamping load is locally applied to a part of the molded product in which a mold space is projected to perform mold clamping. 2. A cavity die having a core accommodating portion and a core die body having a core are provided so as to face each other, and when the one surface of the cavity die and the one surface of the core die body are joined, the core accommodating portion and the A molding die forming space is formed between the cores, a cavity die mounting plate is provided on the other surface of the cavity die, and a core die mounting plate is sandwiched by a spacer on the other surface of the core die body. In the injection molding die, wherein one mounting plate is detachably attached to the fixed portion of the mold clamping device, and the other mounting plate is detachably attached to the movable portion, the other surface of the cavity die is The cavity die mounting plate is configured to be located at a portion where the molded product molding space is projected, and the molded product molding space on the other surface of the core die body is projected. An injection-molding die, characterized in that the spacer is located in the open portion. 3. The shape of the working surface of the cavity die mounting plate is similar to the shape of the portion of the other surface of the cavity die that projects the molding space, and the shape of the working surface of the spacer is The mold for injection molding according to claim 2, wherein the shape is similar to the shape of a portion of the other surface of the core die body onto which the molding space is projected. 4. The area of the working surface of the cavity die mounting plate is approximately half or substantially the same as the area of the projected portion of the cavity on the other surface of the cavity die, and the area of the working surface of the spacer is 4. The injection molding die according to claim 3, wherein the area of a portion of the other surface of the core die body on which the molding space is projected is approximately half or approximately the same. 5. A cavity die having a core accommodating portion and a core die body having a core are provided so as to face each other, and when the one surface of the cavity die and the one surface of the core die body are joined together, the core accommodating portion and the A molding die forming space is formed between the cores, a cavity die mounting plate is provided on the other surface of the cavity die, and a core die mounting plate is sandwiched by a spacer on the other surface of the core die body. In the injection molding die, wherein one mounting plate is detachably attached to the fixed portion of the mold clamping device and the other mounting plate is detachably attached to the movable portion, the other surface of the core die body is provided. An injection-molding die, comprising a pressing member for pressing a portion of the molded product molding space projected toward the cavity die side. 6. The shape of the working surface of the pressing member is similar to the shape of the portion of the other surface of the core die body projected from the molded product molding space.
The injection molding mold described. 7. The area of the working surface of the pressing member is approximately half or approximately the same as the area of the portion of the other surface of the core die body that projects the molding space. Injection mold.