JPH0759357B2 - Powder molding method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a powder molding method, and more particularly to a molding method of a molded body having a hollow portion in a direction perpendicular to a pressing direction of powder. The powder molding method of the present invention can be used for manufacturing carbon products such as electric brushes, mechanical parts using sintered metal, and molding ceramic products.

[0002]

2. Description of the Related Art In powder molding, a molded product having a recess or a protrusion parallel to a pressing direction can be easily molded by providing a protrusion or a recess corresponding to a male mold. However, a molded product having a concave portion which is not perpendicular to the pressing direction cannot be taken out from the mold by providing a protrusion corresponding to the female mold. Therefore, in order to form a molded article having such a recessed shape, it was usual to form the recessed portion later by cutting.

On the other hand, Japanese Utility Model Laid-Open No. 59-43106 discloses that a movable mold is moved forward and backward in a mold space to press a molded product having a hollow shape. In such a case, the recess may have a simple shape, but in the case of a complicated shape such as a triangle, the molded body is scraped and taken out due to spring back of the molded body immediately after pressing. FIGS. 4 and 5 show an example in which the powder molding method in Japanese Utility Model Laid-Open No. 59-43106 is applied to molding a hollow having a triangular cross section.
The powder is put into a mold space defined by the female mold 02 and the male molds 03, 04, and the movable mold 05 is advanced into the mold space by the piston 07 to mold the molded body 01 (FIG. 4). Next, the male die 04 and the piston 07 are raised, the movable die 05 is retracted by the spring 06, and the molded body 01 is taken out from the die space by the male die 03.

The molded body 01 immediately after being pressed is not fired, and has a property of spreading to the surroundings when the pressure is removed. This is springback. The spring back damages the molded body 01 when it is taken out of the mold. When the tip of the movable die 05 is not a flat surface and the cross section has a somewhat complicated shape such as a triangle, a gap is opened between the movable die 05 and the molded body 01 as shown in FIG. And then scraped. The molded body 01 is mainly scraped by the lower taper portion of the hollow portion and the flat portion 08 therebelow, and is scraped by the tip of the movable die 05 and the edge 09 of the female die 02. Therefore, precise molding is difficult, and it is particularly difficult to form deep dents or sharp dents. Further, the shape of the dent is limited to a simple shape having a flat tip, and if the circumference of the dent is thinned, cracks are likely to occur, and it is difficult to mold a small component to a precise and somewhat complicated shape.

[0005]

An object of the powder molding method of the present invention is to make it possible to manufacture a molded body having a recess in a direction perpendicular to the pressing direction. The object of the method of the present invention is to provide a powder molding method capable of performing precise molding without being damaged by spring back of the powder immediately after molding.

[0006]

According to the present invention, there is provided a pressurizing step of pressurizing powder filled in a female mold by upper and lower male molds to form a molded product, and moving at least one of the male molds to form the molded product. In the powder molding method, which comprises a step of taking out from the female die, a movable die having a protruding portion and a flat portion along the lateral direction is movably provided with respect to the female die, and the pressing step is performed. In, the powder is molded along the protrusion of the movable mold, and in the extracting step, the movable mold is moved in the lateral direction,
It is characterized in that the flat part of the movable mold is exposed in the mold and the molded product is pushed up and taken out.

The operation of the present invention will be described. The movable die moves laterally after being pressed, and the flat portion appears in the die space. Therefore, the flat portion of the movable die and the surface of the surrounding female die are flush with each other, and there is no influence of the spring back of the molded body, and the expanded body is not scraped by the spring back. Therefore, it is possible to form a precision recess and to form the recess in a complicated shape, which is particularly suitable for precision molding of small parts such as molding of an electric brush.

[0008]

EXAMPLES Examples will be described below by taking as an example the molding of the electric brush 2 shown in FIG. The electric brush 2 comprises a rectangular parallelepiped molded body 34 of graphite or a mixture of graphite and copper, to which a lead wire 6 made of a twisted wire of copper or the like is fixed. A recess 38 having a shape is provided.

In FIG. 1, 10 is an upper male type, 12 is a lower male type, and the upper male type 10 is provided with a through hole for passing the lead wire 6. A movable die 46 is provided on the female die 14 so that the female die 14 can slide laterally (perpendicular to the cross section of FIG. 1) by using a connecting rod connected to a hydraulic mechanism (not shown). Reference numeral 50 denotes a protrusion of the movable die 46. When the movable die 46 is shown in FIG. 2, reference numeral 48 is a connecting rod which is connected to a hydraulic mechanism (not shown) or the like and is used for moving the movable die 46 in the lateral direction. Reference numeral 50 denotes the above-mentioned protrusion, which has a triangular cross section, 52 denotes a flat surface, and the connecting rod 48
Appears in the mold space, and the flat surface 52 is flush with the surface of the surrounding female mold 14.

First, the upper male die 10 stands still above the female die 14 leaving a gap enough to fill the raw material powder, and the lead wire 6 is pulled out by a predetermined length. After the raw material powder is filled, the upper male die 10 and the lower male die 12 move toward the center of the female die 14 and compression molding is performed. At this time, the projecting portion 50 of the movable mold 46 projects into the female mold 14, and the molding is performed along this. Although the molding is performed by the double pressing method here, other molding methods such as the single pressing method may be used.

When the pressurization is finished, the movable die 46 is pulled out laterally by the connecting rod 48, and the flat surface 52 of the movable die 46 appears on the same plane as the surface of the surrounding female die 14.
Further, the upper male die 10 moves upward and the lead wire 6 is pulled out. Furthermore, the upper male mold 10 and the lower male mold 12 move upward,
The molded body 34 is taken out. Next, the lead wire 6 is cut at an appropriate position, and the molded product 34 is transferred by a pusher (not shown) or the like. Finally, the lower male mold 12 is returned to move to the next molding.

[0012]

According to the powder molding method of the present invention, it is possible to easily mold a molded body having a recess in a direction perpendicular to the pressing direction. In this invention, in particular, the movable die moves laterally after being pressed, and the flat portion thereof appears in the die space. Therefore, the surface around the movable die on the side of the female die is a flat plane, and no recessed portion or edge is generated due to the retracting of the movable die. As a result, there is no deformation due to spring back of the powder immediately after molding,
Precise molding is possible even with indentations with complicated shapes.

[Brief description of drawings]

FIG. 1 is a sectional view showing a powder molding method according to an embodiment.

FIG. 2 is a perspective view of a movable type used in the embodiment of FIG.

FIG. 3 is a perspective view of an electric brush formed by the method of the embodiment of FIG.

FIG. 4 is a cross-sectional view showing a pressurizing step in a conventional powder molding method.

FIG. 5 is a cross-sectional view showing a take-out step in a conventional powder molding method.

[Explanation of symbols]

 2 Electric brush 6 Lead wire 10 Upper male type 12 Lower male type 14 Female type 32 Electric brush 34 Molded body 38 Recessed portion 46 Movable type 48 Connecting rod 50 Protruding portion 52 Flat surface

Claims (1)

[Claims] 1. A pressurizing step of pressurizing powder filled in a female mold by upper and lower male molds to form a molded body, and removing at least one of the male molds to take out the molded body from the female mold. In the powder molding method including a step, a movable die having a projecting portion and a flat portion along a lateral direction is movably provided on the female die with respect to the female die, and in the pressing step, the movable die is projected. Molding the powder along the part, and in the removing step, moving the movable mold laterally to expose the flat part of the movable mold in the mold, and pushing the molded product upward to remove it. A powder molding method characterized by: