JP2002316297A - Powder molding die made of sintered hard alloy making lower punch reutilizable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder molding die consisting of dies and upper and lower punches made of sintered hard alloys reduced in a cost. SOLUTION: The cylindrical part of the lower punch is previously provided with a projecting part 5 in such a manner that the lower punch 2 can be reused as an upper punch after the punch comes to the end of its life and the inside surface part of the die is provided with a clearance 4 in such a manner that the projecting part does not come into contact with the inside surface part when a green compact is drawn out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold used for compression-molding powders of metals, ceramics, synthetic resins and the like.

[0002]

2. Description of the Related Art Cemented carbides having excellent wear resistance are often used for powder molding dies, but since cemented carbides are expensive, cost reduction or weight reduction is required. Usually, a cemented carbide tip is often used by brazing the tip of a steel punch. However, when the molding pressure is used at a high pressure of several ton / cm ² or more, such as tablet molding of a resin for semiconductor encapsulation, the brazing layer is plastically deformed,
Since there is a problem of peeling off soon, it is common practice to manufacture the entire punch with a cemented carbide.

[0003]

In the above case, the abrasion of the punch usually proceeds faster than the die, and when the abrasion of the punch occurs, the punch is re-ground and used repeatedly. There is a limit due to the wear of the punch and the side of the punch. Also,
If there is a problem with the rigidity or accuracy of the molding machine, the tip of the punch may be damaged due to contact with the inner surface of the die at the time of molding, and may become unusable. Since a cemented carbide is a material that is more expensive than tool steel or the like, there is a problem that it is difficult to reduce the molding cost of a workpiece by using such a mold.

[0004]

According to the present invention, in order to solve the above-mentioned problems, the lower punch can be recycled as the upper punch after the end of the service life of the cemented carbide punch. . That is, in the conventional mold, in order to prevent the frictional resistance between the die and the punch from increasing due to the powder entering the gap between the die and the punch, as shown in the sectional views of FIGS. In the trunk other than the vicinity of the part, the reliefs 3 and 4, which are slightly smaller in size than the pressing part, are provided, so that the punch which has reached the end of its life cannot be reproduced into a shorter length punch. A convex portion is provided in advance on the body of the lower punch so that the lower punch can be reused as an upper punch, and a relief is provided on the inner surface portion so that the convex portion does not contact the inner surface portion of the die when the green compact is extracted. It is something to keep.

[0005]

FIG. 3 is a cross-sectional view of a cemented carbide powder molding die according to the present invention, and FIG. 4 is a cross-sectional view of only the lower punch 2 of FIG. Usually, in order to remove the green compact from the die after molding, it is necessary to push up the lower punch 2 or push down the die 6 so that the pressing surface of the lower punch 2 reaches the upper end position of the die 6. The length of the upper punch 1 is slightly longer than the length of the die 6, while the upper punch 1 does not have such a restriction and has only to be long enough to compress the powder. The length is made shorter than the lower punch 2. The body portion of the upper punch 1 and a lower punch 2, 3, 4 relief respectively provided, of L ₁ equal to the length of the upper punch 1 is the body of the lower punch 2, as shown in FIG. 4 The projection 5 is formed from the position. To ensure the machining margin for recycling by processing the upper punch the lower punch after the length L ₃ to the upper end of the convex portion 5 the upper punch 1
Slightly longer than L ₂ in its outer dimensions kept equal or slightly larger and inner dimensions of the die. FIG.
FIG. 3 is a cross-sectional view of only the die shown in FIG. 3, but in order to extract the formed green compact from the die,
A relief 7 is provided on the inner surface below the die so that the protrusion 5 of the lower punch does not contact the inner surface of the die 6 when the lower punch is moved to the upper end position. After the end of the life of the punch, the upper portion of the lower punch protrusion is cut, processed into a predetermined size of the upper punch, and used in combination with a new lower punch.

[0006]

As described above, in a powder molding die, conventionally, a punch whose life has expired had to be discarded. However, according to the present invention, a lower punch can be recycled as an upper punch. In addition, die costs can be reduced and resources can be saved. In particular, in the case of a punch having a molding pressure as high as about 10 ton / cm ² and a concave pressing surface, such as a tablet molding die of a semiconductor sealing resin, the load acting on the outer edge of the pressing surface is higher. The present invention is particularly effective because the punch has a short life because the outer edge portion is easily worn due to wear or chipping.

[Brief description of the drawings]

FIG. 1 is a sectional view of a conventional mold.

FIG. 2 is a sectional view of only a lower punch of FIG. 1;

FIG. 3 is a sectional view of a mold according to the present invention.

FIG. 4 is a sectional view of only the lower punch 2 of FIG. 3;

FIG. 5 is a sectional view of only the die of FIG. 3;

[Explanation of symbols]

 1 Upper Punch 2 Lower Punch 3 Relief of Upper Punch 4 Relief of Lower Punch 5 Protrusion Provided on Lower Punch 6 Die Made of Carbide 7 Relief Provided on Die 8 Steel Die Case

Claims (2)

[Claims] In a powder molding die comprising a cemented carbide die and upper and lower punches, a convex portion is previously formed on a body portion of a lower punch so that the lower punch can be reused as an upper punch after the end of the life of the punch. And a relief provided on the inner surface of the die so that the protrusion does not contact the inner surface of the die when the formed green compact is extracted. 2. The mold according to claim 1, which is used for tablet molding of a resin for semiconductor encapsulation.