JPH0641603A - Press-forming machine - Google Patents

Abstract

PURPOSE:To reduce the cracks on the inner wall face of a cavity, etc., and to smoothly finish the surface of a formed body by specifying the effective length of the punch of a press-forming machine, the clearance between the punch and cavity, etc. CONSTITUTION:A powder is pressed and formed by this press-forming machine. The effective length of either the upper punch 2 or lower punch 3 is controlled to <=100mm, and the clearance between the punches 2 and 3 and a die 1 and/or the clearance between the punches 2 and 3 and a core is adjusted to 1-800mum. Consequently, the upper and lower punches 2 and 3, die 1 and core wall face are not cracked, and the surface of the formed body is smoothly finished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a press molding machine for pressing powder.

[0002]

2. Description of the Related Art Conventionally, in the production of a sintered body such as a permanent magnet, a press molding machine has been used to compact the powder to be sintered before sintering. This press molding machine has a cavity 12 formed by a die 11 as shown in FIG.
Insert the upper and lower punches 13 and 14 into the upper and lower punches 1
It has a basic mechanism in which the body 15 to be molded is compacted by 3, and 14. In this conventional press molding machine, the upper punch side surface effective portion 13a and the lower punch side surface effective portion 14a are used as slide guides when the upper and lower punches 13 and 14 are reciprocally moved in the cavity 12 to press-form the molded body 15.
Was working. In other words, the side effective part 1 of the upper punch
3a, the upper and lower punches 13, 14 while the side surface effective portion 14a of the lower punch contacts and slides on the inner side surface of the die 11.
Was reciprocating in the cavity 12.

[0003]

However, the above conventional press molding machine has the following problems. In the conventional press molding machine, it is necessary to bring the side surface effective portion 13a of the upper punch and the side surface effective portion 14a of the lower punch into contact with the inner surface of the die 11 to function as a slide guide, so that the clearance between the upper and lower punches 13 and 14 and the die 11 is increased. 16, 17
Is required to be a narrow dimension of about 1 μm. Therefore, if powder penetrates between the upper and lower punches 13 and 14 and the die 11 during the powder compression molding process, the friction between the upper and lower punches 13 and 14 and the die 11 is reduced. Becomes excessively large, and the invaded powder causes galling on the side surface of the die 11 and the side surfaces of the upper and lower punches 13 and 14, and the galling scratch is transferred to the molded body 15. As a result, the obtained product becomes a product with a non-smooth surface. Was there. In other words, in the manufacturing process of powder metallurgy where the metal or oxide powder is pressed into the desired shape and then sintered into a product, the dimensions must be within the specified tolerance for the product to be unprocessed after sintering. Not only must it be contained, but the product surface must have a smooth finish without scratches. However, on the surface of the conventional product manufactured by using the above-mentioned conventional press molding machine, scratches of the upper and lower punches of the press machine and scratches of the die are transferred, and scoring scratches occur, so that a smooth and undamaged finished surface can be obtained. I couldn't. Therefore, the present invention has been made in view of the above problems in the conventional press molding machine, and can reduce the occurrence of scratches on the upper and lower punches and the cavity inner wall surface, and the surface of the molded body as a smooth finish, It is an object of the present invention to provide a press molding machine capable of improving the production efficiency and increasing the yield.

[0004]

As a result of various studies to achieve the above-mentioned object, the present inventor has found that the upper punch and / or the lower punch constituting the press molding machine, or the effective portion of both punches is 100 mm or less. It has been found that the above is effective and the present invention has been created. That is, in the present invention, in a press molding machine for pressurizing and molding powder, at least one of the upper punch and the lower punch has an effective portion length of 100 or more.
The feature is that it is less than or equal to mm. Furthermore, the present invention is characterized in that the clearance between the punch and the cavity or / and between the punch and the core is in the range of 1 μm to 800 μm in the press molding machine that pressurizes and molds the powder.

In the present invention, the upper and lower punches are firmly fixed to the molding machine to maintain the straightness of the punch by the straightness of the cylinder of the molding machine. As a result, the effective length of at least one of the upper punch and the lower punch can be set to 100 mm or less. If the effective portion length is 100 mm or more, the friction between the punch and the cavity increases, and the extraction pressure becomes high, so that it cannot be used. Further, it is not necessary to shorten the effective portion for both the upper and lower punches, and only the upper punch or only the lower punch may have a shorter effective portion. At that time, the object of the present invention can be achieved by shortening the effective portion of the punch on the side where the molded product is removed from the press machine.

Further, the clearance between the upper and lower punches and the cavity is set in the range of 1 μm to 800 μm. A clearance of 800 μm or more is not preferable because the material passes through the gap between the punch and the cavity. The clearance is 1 μm
In the following, if powder material enters between the upper and lower punches and the die in the powder compression molding process, the friction between the upper and lower punches and the die becomes excessive, and the invaded powder material causes galling on the side surface of the die and the side surface of the upper and lower punches. However, as a result of the scratches being transferred to the molded body, there is a problem that the obtained product has a non-smooth surface, which is not preferable. Further, in a press having a structure in which a hole is formed at the center of the punch and the core penetrates, the clearance between the core and the upper and lower punches is still in the range of 1 μm to 800 μm, and the frictional force is the smallest and good.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the press molding machine of the present invention will be described with reference to the drawings. In the press molding machine shown in FIG. 1, the upper and lower punches 2 and 3 which are inserted into the die 1 are firmly fixed by using a large number of bolts 5 and the like with respect to a cylinder 4 which moves forward and backward in the direction of arrow A in the figure. Further, the effective portion lengths 2a and 3a of the upper and lower punches 2 and 3 which are firmly fixed in this way are set to 3 mm in this embodiment.
Therefore, according to the press molding machine of this embodiment, the straightness of the upper and lower punches 2 and 3 is guaranteed by the straightness of the cylinder 4. Therefore, since it is not necessary to guarantee the straightness of the upper and lower punches 2 and 3 by the die 1, it is possible to form a certain clearance between the die 1 and the upper and lower punches 2 and 3. The clearance is preferably set to 1 to 800 μm, and in this embodiment, the clearance is set to 70 μm. Therefore, according to the press molding machine of the above-mentioned embodiment, even if the material enters between the upper and lower punches 2 and 3 and the die 1 in the process of compression-molding the molded body 6 with the upper and lower punches 2 and 3, it is caused by it. As a result, no scratches are formed on the side surface of the die 1 or the upper and lower punches 2 and 3, and no scratches are transferred to the obtained molded body, and the surface becomes smooth.

FIG. 2 shows a press molding machine according to another embodiment of the present invention. In the press molding machine of this embodiment, the molded body 6 is formed into an annular shape, the lower punch 7 has the core 8 integrally, and the upper punch 9 has the insertion hole 10 for the core 7 of the lower punch 7. . The clearance between the insertion hole 10 and the core 8 is 1
It is preferable that the thickness is 700 μm to 700 μm in this embodiment.
It was m. Therefore, according to the press molding machine of the above embodiment, even if the material enters between the upper and lower punches 9 and 7 and the die 1 in the process of compression-molding the molded body 6 with the upper and lower punches 9 and 7, As a result, no galling is formed on the side surface of the die 1 or the upper and lower punches 9 and 7, and no galling is transferred to the obtained molded body.
The surface becomes smooth. Further, since there is a certain clearance between the wall surface of the insertion hole 10 of the upper punch 9 and the core 8, the wall surface of the insertion hole 10 and the core 8 are compressed in the process of compression-molding the molded body 6 with the upper and lower punches 9, 7. Even if the material enters between the cores, the wall surface of the insertion hole 10 and the core 8 will not be scratched due to it, and the inner surface 6a of the ring of the obtained molded body will not be scratched. No scratches will be transferred. Therefore, the obtained molded body 5 has a smooth surface.

FIG. 3 shows the galling of the side surface of the molded body obtained when press molding of powder is carried out using the press molding machine of the present invention and the conventional press molding machine with various clearances between the upper and lower punches and the die. The results of an investigation of the number of flaw occurrences are shown below. As shown in the figure, scoring on the side surface of the molded product occurs when the clearance between the upper and lower punches and the die becomes smaller, and when the clearance between the upper and lower punches and the dies is less than 1 μm, the scoring occurs significantly.

FIG. 4 shows an annular molded body obtained when press molding of powder is carried out by setting various clearances between the upper and lower punches and the core using the press molding machine of the present invention and the conventional press molding machine. The results of an investigation of the number of bite marks generated on the inner surface of the circle are shown below. As shown in the figure, scuffing on the inner surface of the ring occurs when the clearance between the upper and lower punches and the core becomes smaller, and the clearance between the upper and lower punches and the core becomes 1
When it is less than μm, the occurrence of galling becomes remarkable.

[0011]

As described above, according to the press molding machine of the present invention, in the press molding machine for compressing and molding powder, at least one of the upper punch and the lower punch has an effective length of 1 or less.
By setting the clearance between the punch and the die and between the punch and the core within the range of 1 μm to 800 μm, scratches on the upper and lower punches, the die and the core wall surface are suppressed, resulting in a smooth finish of the molded body. It is possible to significantly improve the quality and increase the yield.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a press molding machine according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a press molding machine according to another embodiment of the present invention.

FIG. 3 is a diagram showing the number of scuff marks on the side surface of a compact obtained when the powder is press-molded by using the press molding machine of the present invention and the conventional press molding machine with various clearances between the upper and lower punches and the die. The results of the survey are shown below.

FIG. 4 is an annular ring of an annular molded body obtained when press molding of powder is performed by using the press molding machine of the present invention and a conventional press molding machine to set various clearances between the upper and lower punches and the core. The results of an investigation of the number of scratches on the inner surface are shown.

FIG. 5 shows a schematic sectional view of a conventional press molding machine.

[Explanation of symbols]

 1 Die 2, 9 Upper punch 4 Cylinder 5 Bolt 3, 7 Lower punch 3 2a, 3a Effective part length 6 Object to be molded

Claims (2)

[Claims] 1. A press molding machine for pressurizing and molding powder, wherein at least one of the upper punch and the lower punch has an effective portion length of 100 mm or less. 2. A press molding machine for pressurizing and molding powder, wherein the clearance between the punch and the die or / and the punch and the core is in the range of 1 μm to 800 μm.