JPH0726071Y2 - Mold for powder molding - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention uses an upper punch and a lower punch fitted in a through hole of a die to form a recess on the surface of the lower punch. The present invention relates to a powder molding die for molding a green compact.

“Prior Art” Conventionally, for example, a hollow green compact 1 as shown in FIG. 2 and FIG. 3, that is, having a central hole 1a in the central portion and a large number of small holes 1b in the peripheral portion. A compact 1 having a disk-shaped main body 1c formed and a cylindrical portion 1d integrally formed with the main body 1c, and a recess 1f formed in a lower surface 1e of the main body 1c.
In the case of powder-forming, the powder-molding die as shown in FIGS. 4 and 5 is used.

This powder molding die has an upper surface of the green compact 1 in a through hole 2a of a die 2 for forming the outer periphery of the main body 1c of the green compact 1.
An upper punch 5 consisting of 1 g of a first upper punch body 3 forming a portion corresponding to the recess 1f and a second upper punch body 4 forming an upper surface 1g of the green compact 1 other than the portion, and a main body Bottom of 1c
1e and an outer lower punch body 6 forming the outer peripheral surface of the cylindrical portion 1d and an inner lower punch body 7 forming the lower surface of the cylindrical portion 1d, an inner core rod 9 forming a center hole 1a, and a small punch. The green compact 1 is molded by being fitted into the outer core rod 10 forming the hole 1b.

The first upper punch body 3 vertically penetrates the second upper punch body 4, and the inner lower punch body 7 vertically penetrates the outer lower punch body 6. . Further, the inner core rod 9 vertically penetrates the inner lower punch body 7 and the second upper punch body 4, and the outer core rod 10 vertically penetrates the outer lower punch body 6 and the second upper punch body 4. It has become.

[Problems to be Solved by the Invention] By the way, in the case of molding the green compact 1 using the above-mentioned conventional powder molding die, as shown in FIG. 4, inside the through hole 2a of the die 2. The lower punch 8 and the inner and outer core rods 9,
In a state where 10 is mounted and the raw material powder is loaded in the die cavity, first, the first upper punch body 3 is lowered so that the protrusion 6a of the outer lower punch body 6 and the protrusion 6a are formed before the compression step. After the powder between the first upper punch body 3 having a size is released to the surroundings, the second upper punch body 4 is fitted into the die 2, and the raw material powder in the die cavity is compressed to form the green compact 1. I am trying to do it. In this case, when the compression is completed, 0
1st upper punch body 3 and 2nd upper punch body 4 in the range of ~ 0.15mm
A step d occurs due to a mismatch with (see FIG. 5).

If the step d is present, the green compact of the step portion expands toward the inner wall surface 4a of the second upper punch body 4 when the compression is completed. Friction resistance acts between the inner wall surface 4a and the green compact of the step portion, and a peeling 11 phenomenon as shown in FIG. 6 occurs.

On the contrary, when the step d is 0, burrs are generated due to the powder entering the fitting portion between the first upper punch body 3 and the second upper punch body 4, and the burrs are lifted when the upper punch 5 moves up. The peeling 12 shown in FIG. 7 occurs. in this way,
In the past, peeling 11 and 12 were generated in the green compact 1, so cutting work to remove these peeling 11 and 12 is indispensable.
Those that require cutting and grinding have a problem that the machining allowance increases.

The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent peeling that occurs in a green compact, and to omit the cutting work that has been conventionally performed due to peeling. An object of the present invention is to provide a mold for powder molding which can be manufactured and can reduce the manufacturing cost.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the powder molding die of the present invention uses an upper punch and a lower punch fitted in the through holes of a die to form the lower punch. A die for molding a powder compact having a recess formed on its side surface, wherein the upper punch forms a portion corresponding to the recess on the upper punch side surface of the green compact. The first upper punch body is divided into a second upper punch body and a second upper punch body that forms a portion other than the above portion, and the first upper punch body slides in a through hole formed in the second upper punch body. The second upper punch body is freely fitted inside, and when the compression molding is completed, the end surface of the second upper punch body on the green compact side is closer to the green compact side than the end surface of the first upper punch body on the green compact side. Is displaced to the end face on the green compact side and the first
The through hole which is positioned with respect to the first upper punch body so as to form a step between the upper punch body and the end surface of the upper punch body on the green compact side, and which is formed through the second upper punch body. It is characterized in that a draft or a rounded portion corresponding to the step is formed at the edge portion on the side of the green compact.

[Operation] In the powder molding die of the present invention, the end surface of the second upper punch body on the side of the powder compact is pressed more than the end surface of the first upper punch body on the side of the powder compact when the molding is completed. Since it is displaced toward the powder side and a step is formed between the end surface of the green compact side and the end surface of the first upper punch body on the green compact side, the first upper punch of the green compact is formed. In the portion formed by the body, a step portion that protrudes from the surface of the portion formed by the second upper punch body of the green compact is formed.

This prevents burrs from being generated in the green compact due to the end surface of the first upper punch body and the end surface of the second upper punch body being flush with each other, and thus the burrs are lifted when the upper punch is lifted. It is possible to prevent peeling from occurring on the surface of the upper punch side.

Further, since the draft angle or the rounded portion corresponding to the step is formed at the edge corner portion of the through hole penetrating the second upper punch body on the green compact side, the green compact of the formed green compact is formed. Since the outer peripheral edge portion of the step portion is thickened to increase its strength, it is possible to prevent the outer peripheral edge portion from being peeled off when the upper punch body is raised.

[Embodiment] An embodiment of the present invention will be described below with reference to FIG.
In the present embodiment, parts having the same configurations as those of the conventional example shown in FIGS. 4 and 5 are given the same reference numerals to simplify the description.

As shown in FIG. 1, the powder molding die of this embodiment is provided with a new upper punch 20 in place of the upper punch 5 of the conventional powder molding die.

The upper punch 20 is a first upper punch body that forms a portion of the green compact 1 facing the protrusion 6a of the outer lower punch body 6.
21 and a second upper punch body 22 for molding the other part of the green compact 1 and the first upper punch body 21.
Is slidably fitted in a through hole 22a penetrating the second upper punch body 22.

When the compression molding is completed, the end surface 22b of the second upper punch body 22 on the green compact 1 side is displaced toward the green compact 1 side more than the end surface 21a of the first upper punch body 21 on the green compact 1 side. The green compact 1
Side end face 22b and the end face 21a of the first upper punch body 21 on the green compact 1 side.
Is positioned with respect to the first upper punch body 21 so as to form a step d between 0.05 and 0.15 m.

Further, the green compact 1 in the through hole 22a of the second upper punch body 22
A draft or rounded portion 22c corresponding to the step d is formed at the side edge corner.

In order to mold the green compact 1 using the powder molding die configured as described above, the lower punch 8 is placed in the through hole 2a of the die 2.
With the inner and outer core rods 9 and 10 mounted, and the raw material powder loaded in the die cavity, first, the first upper punch body 21 is lowered and positioned and fixed at a predetermined position. Projection of outer lower punch body 6
The powder between 6a and the first upper punch body 21 is released to the surroundings. Then, the second upper punch body 22 is fitted into the die 2, and the step d is formed between the end surface 22b of the first upper punch body 21 on the green compact 1 side and the end surface 22b of the first upper punch body 21. The raw material powder in the die cavity is compressed by displacing it to the position where
To mold. Then, the green compact 1 thus formed is taken out of the die 2 by raising the upper punch 20.

It should be noted that the second upper punch body 22 can be easily lowered, for example, by using a backward movement press device after the first upper punch body 21 is lowered and positioned at a predetermined position.

As shown in FIG. 1, when the compression molding is completed, the end face 21a of the first upper punch body 21 on the side of the green compact 1 and the end face 22b of the second upper punch body 22 on the side of the green compact 1 are formed. Since the step d is formed between the first step 1 and the second step 1,
A step portion 1h is formed in which the portion formed by the upper punch body 21 projects from the surface of the portion formed by the second upper punch body 22 of the green compact 1.

Thereby, it is possible to prevent burrs from being generated on the surface of the green compact 1 due to the end surface 21a of the first upper punch body 21 and the end surface 22b of the second upper punch body 22 being flush with each other. It is possible to prevent the peeling from occurring on the surface of the green compact 1 on the upper punch 20 side by lifting the burr when the punch 20 is raised.

Further, since the draft angle or the rounded portion 22c corresponding to the step d is formed at the edge corner portion of the through hole 22a penetrating the second upper punch body 22 on the green compact 1 side, molding is performed. The outer peripheral edge portion of the stepped portion 1h of the compressed green compact 1 is increased in thickness and its strength is enhanced, so that the outer peripheral edge portion of the stepped portion 1h is prevented from peeling when the upper punch 20 is raised. can do.

[Advantages of the Invention] As described above, the powder molding die of the present invention uses the upper punch and the lower punch fitted in the through holes of the die to form a recess on the surface of the lower punch. And a first upper punch body, wherein the upper punch forms a portion corresponding to the recess of the upper punch side surface of the green compact. The second upper punch body is divided into a second upper punch body forming a portion other than the above portion, and the first upper punch body is slidably fitted in a through hole formed in the second upper punch body. And the second upper punch body,
When the compression molding is completed, the end surface on the side of the green compact is the first
Displaced to the green compact side from the green compact side end face of the upper punch body, and between the green compact side end face and the green compact side end face of the first upper punch body. Positioned with respect to the first upper punch body so as to form a step, and the green powder side edge corner portion of the through hole penetrating the second upper punch body corresponds to the step. Since the draft or the rounded portion is formed, the end surface of the first upper punch body on the green compact side and the end surface of the second upper punch body on the green compact side are formed at the completion of compression molding. By making the surface flush, it is possible to prevent burrs from being generated on the surface of the green compact, and thus to prevent the burrs from being lifted when the upper punch rises so that peeling does not occur on the surface of the green compact on the upper punch side. Not only is it possible to form the first upper punch body of the green compact and the second upper punch. It is possible to increase the thickness of the outer peripheral edge portion of the step portion formed between the portion formed by the chi body and increase its strength, and thereby to prevent the outer peripheral edge portion from being peeled off when the upper punch body is raised. .

As a result, it is possible to omit the conventional cutting process to remove the peeling that occurs in the green compact, and for those that require grinding, use only the grinding process without cutting. And the processing cost can be reduced,
Therefore, the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIGS. 2 and 3
The figure shows an example of the target green compact, FIG. 2 is a cross-sectional view, FIG. 3 is a bottom view, and FIGS. 4 and 5 show a conventional powder molding die. FIG. 4 is a cross-sectional view, FIG. 5 is a cross-sectional view of a main part, FIG. 6 is a cross-sectional view showing an example of a peeling phenomenon that has occurred in a green compact, and FIG. It is sectional drawing which shows an example. 1 ... green compact, 1e ... bottom surface (one surface), 1f ... recess,
1g: top surface (other surface), 2 die, 2a, through hole,
8: lower punch, 20: upper punch, 21: first upper punch body, 21a: end face on the compact side, 22: second upper punch body, 2
2a ... through hole, 22b ... end face on the side of green compact, 22c ... draft or rounded portion.

Claims (1)

[Scope of utility model registration request] 1. A powder molding die for molding a green compact having a recess on the surface on the lower punch side, using an upper punch and a lower punch fitted in the through holes of a die. And the upper punch is divided into a first upper punch body forming a portion corresponding to the recess on the upper punch side surface of the green compact and a second upper punch body forming a portion other than the portion. In addition, the first upper punch body is slidably fitted in a through hole formed in the second upper punch body, and
When the compression molding is completed, the upper punch body is displaced toward the green compact side from the green compact side end surface of the first upper punch body, and the green compact is moved toward the green compact side. Is positioned with respect to the first upper punch body so as to form a step between the end surface on the side of the first upper punch body and the end surface on the side of the green compact of the first upper punch body, and is further provided through the second upper punch body. A die for powder molding, wherein a draft or a rounded portion corresponding to the step is formed at an edge corner portion of the through hole on the green compact side.