JPH0816241B2 - Powder compression molding method for molded article having boss and flange - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for forming a molded product by compression molding metal powder, and more specifically, to the compression of a molded product having a boss and a flange among the molded products. It relates to a molding method.

[Prior Art] In order to form a gear or the like by so-called powder sintering, it is necessary to form metal powder into a desired shape such as a gear. In order to mold the metal powder into a desired molded product, conventionally, as shown in FIGS. 4 to 8, the press machine 1 was used for pressing.

The press machine 1 includes an upper mold 2 and a lower mold 3. The upper mold 2 has an upper ram 2a that is driven up and down, a partition 2a1 that defines the inside of the upper ram 2a into upper and lower chambers R1 and R2, and the upper chamber R1 that is defined by the partition 2a1 penetrates the partition 2a1. And the upper inner punch 2b driven up and down and the upper ram
It is composed of an upper outer punch 2c which is installed in the lower chamber R2 of 2a and which is driven vertically by fitting the upper inner punch 2b into the center. An air flow path L1 for driving the upper inner punch 2b up and down is formed in a lower portion of the top plate portion 2a2 of the upper ram 2a so as to communicate with the compression chamber R0. In addition, the partition 2a1 has an air flow path L communicating with the upper chamber R1 and the lower chamber R2.
2 and L3 are formed respectively. Below the lower chamber R2,
The compression chamber R3 is defined. The side wall of the upper ram 2a is provided with a ventilation path L4 communicating with the atmosphere side.

The lower die 3 includes an upright under inner punch 3b,
It is composed of an under-outer punch 3c which is vertically driven by fitting the under-inner punch 3b, and a die 3a which is vertically driven by fitting the under-outer punch 3c. At the bottom of this die 3a, fork 3a
1 is attached. A roller 4 which is movable in the horizontal direction is provided at the lower end of the fork 3a1. The roller 4 moves to move the under outer punch 3c.
Is designed to be lowered.

In order to mold the molded product 5 using such a press machine 1, as shown in FIG. 4, first, the lower mold 3 is filled with a predetermined amount of the metal powder P. Then, the entire upper die 2 is lowered by hydraulic pressure or the like. In this case, open the flow path L1 for air and set the flow paths L2 and L3.
From the above, air of a predetermined pressure is sent to the upper chamber R1 and the lower chamber R2 to lift the upper inner punch 2b and press the upper outer punch 2c downward. In parallel with this operation, the lower outer punch 3c is lowered. At this time, the lower end of the upper outer punch 2c and the lower outer punch
The distance from the top of 3c is constant. This is FIG.

Next, the compression process is shown in FIGS. 5 and 6. In this compression step, the upper mold 2 is further lowered to compress the metal powder P. At this time, the die 3a also descends as the upper die 2 descends. At the final compression position (bottom dead center) shown in FIG. 6, air of a predetermined pressure is sent from the flow passage L1 and the flow passage L3 to the compression chamber R0 and the lower chamber R2, and the air is discharged from the flow passage L2 so that the upper inner The punch 2b and the upper outer punch 2c are pressed to obtain the desired shape and size of the molded product 5.

Next, in order to extrude the molded product 5 from the mold, as shown in FIG. 7, the die 3a of the lower mold 3 is first lowered while gradually raising the upper mold 2, and the roller 4 is moved horizontally by the fork 3a1. Under outer punch that works with this
Lower 3c. When the molded product 5 is extruded, the molded product 5 behaves due to vertical movement of a punch or the like. Therefore, in order to suppress this behavior, a cylinder (not shown) provided inside the upper ram 2a causes the upper outer punch 2c to move. Always pressed downward. Then, with the behavior of the molded product 5 subsided, the upper mold 2 may be further raised to take out the molded product 5.

[Problems to be Solved by the Invention] When the molded product is extruded, the upper mold 2 is in the upward process, but as shown in FIG. 8, when the molded product 5 is a gear having upper and lower bosses 5a. In order to suppress the behavior, the lower end of the upper outer punch 2c is always in contact with the flange 5b of the molded product 5 during the extrusion process, and the lower chamber R2 is
Also in this pushing step, air of a predetermined pressure is sent to constantly push the upper outer punch 2c downward, so that the flange 5b is often broken immediately before raising the upper die 2 as shown in FIG. There was a problem of doing. As a result, the yield of the molded product 5 is poor, which is one of the causes of hindering cost reduction.

The present invention has a problem in that the flange of the molded product having the boss and the flange is broken by the downward pressing of the upper outer punch during extrusion.

[Means for Solving Problems] According to the present invention, a lower die is filled with metal powder, and the upper die is lowered to compress the metal powder filled in the lower die by an upper inner punch and an upper outer punch of the upper die. Then, in the powder compression molding method of a molded product having a boss and a flange that are formed by extruding the molded product, the downward pressing of the upper outer punch is released when the molded product is extruded. It is a thing.

[Embodiment] FIGS. 1 to 3 show the steps of one embodiment of the present invention. The press machine 1 has a flow path L5 which communicates from the outer periphery of the upper ram 2a of the upper mold 2 to the compression chamber R3. Is different from the conventional one in that it is formed separately from the ventilation path L4.

FIG. 1 corresponds to FIG. 6 showing a conventional process,
At the final compression position (bottom dead center), channel L1 and channel L3
Blows air of a predetermined pressure into the compression chamber R0 and the lower chamber R2
By bleeding air from R1 and the lower chamber R2, the upper inner punch 2b and the upper outer punch 2c are pressed downward, and the metal powder P is compression-molded to obtain a molded product 5.

At the time of extruding the molded product, the air of a predetermined pressure is blown into the compression chambers R0 and R3 from the flow paths L1 and L5, and the air in the upper chambers R1 and R2 is evacuated from the flow paths L2 and L3. The upper outer punch 2c is raised while pressing the punch 2b downward (FIGS. 2 and 3).

As a result, the behavior of the molded product 5 at the time of extrusion can be suppressed, and the flange 5b of the molded product 5 does not hit the lower end of the upper outer punch 2c to press the flange 5b downward unlike the conventional case. Therefore, the flange 5b is not damaged.

In the above embodiment, the flow path L5 is formed in the upper ram 2a, but without forming such a flow path L5, air is simply blown from the flow path L1 to form the flow path L2 and flow. You may make it bleed air from the path L3. Even in this case, since the upper outer punch 2c is not pressed at least downward, there is no risk of damaging the flange 5b.

[Advantages of the Invention] According to the present invention, the downward pressing of the upper outer punch is released when the molded product is extruded. Therefore, it is possible to prevent the flange from being damaged when the extruded product is extruded. It is possible to improve the product yield and reduce the cost.

[Brief description of drawings]

1 to 3 show one embodiment of the present invention,
FIG. 1 is a sectional view showing the final compression position of the upper die, and FIGS. 2 and 3 are sectional views showing the movement of the upper outer punch during extrusion. FIG. 4 to FIG. 8 are cross-sectional views of a conventional press machine, showing the movement of the upper die and the lower die in each step. 2 …… Upper die, 2b …… Upper inner punch, 2c …… Upper outer punch, 3 …… Lower die, 3c …… Under outer punch, 5 …… Molded product, 5a …… Boss, 5b …… Flange, P …… Metal powder.

Claims (1)

[Claims] 1. A lower die is filled with metal powder, and the upper die is lowered to compress the metal powder filled in the lower die by an upper inner punch and an upper outer punch of the upper die, and then a molded product is extruded. In a powder compression molding method of a molded article having a boss and a flange adapted to be molded by
The upper outer punch and the lower outer punch of the lower die form a flange for the molded product, and the downward pressing of the upper outer punch is released when the molded product is extruded. Powder compression molding method for molded articles.