JPH0390502A - Die for powder forming - Google Patents

Abstract

PURPOSE:To enable press forming for thin powder metallurgical parts without uneven thickness by adjusting depth in cavity through a stopper set between lower part of a core rod supporter and a lower ram base plate. CONSTITUTION:Raw material powder is packed into the cavity C formed with a die 1, lower punch 3 and core rod 4, and by descending an upper punch 7, compressed forming is executed between the upper punch and the lower punch 3 to obtain the thin powder metallurgical parts having center hole. In a metallic mold 40 for powder forming in the above forming apparatus, the stopper 25 is set between the lower part of supporter 8 for supporting the above core rod 4 and the lower ram base plate 11. This stopper 25 is vertically shifted through a worm wheel 22 having female screw 23 engaging with the male screw 24 thereof and a worm 21 to vary the height thereof. By this method, cavity depth H between the upper face 1a of die 1 and the upper face 4a of core rod 4 is set to the depth according with the shape of forming body to prevent the development of uneneven thickness in the obtd. formed body.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a powder compacting apparatus, and more particularly to a powder compacting mold for forming thin-walled powder metallurgy parts having a central hole.

[Conventional technology]

In powder metallurgy, powder is molded into a predetermined shape and then processed through processes such as sintering or sinter-forging to create a product, but the molding is generally performed using a mold method, and molded bodies of various shapes are produced. Produced using molds. Among these, a powder molding die 40 as shown in FIG. 7 has been generally used as a molding apparatus for a cylindrical thin-walled part having a center hole. In the figure, the Goui plate 2 is connected to a base plate 11 attached to a lower press ram 16 via a guide bar 14, and is linked to the movement of the lower press ram. The pressure plate 15 is fixed to a press bed (not shown) and does not move with the movement of the lower press ram, and the lower punch 3 is fixed to the pressure plate 15. The die 1 attached to the gou plate 2 is the lower punch 3
and core rod 4 to create a cavity (recess)
He is disciplining C. The raw material powder is filled into the cavity C from a feeder 6 that reciprocates on the goo plate 2, and an upper punch 7 and a lower punch 3 that operate in conjunction with an upper press ram (not shown).
compression molded between. After compression molding, press lower ram 1
6 moves downward, the base plate 11 also moves downward, and the die plate 2 connected to these by the guide bar 14 moves downward in conjunction with this, and the spring 5 and the pressure plate 15 move together. Since the core rod 4 and its supporter 8 extend downward from the contact surface as a starting point, the core rod 4 and its supporter 8 move downward together with the base plate 11 due to the biasing force of the spring 5.

At this time, since the pressure plate 15 is stationary, the lower punch 3 fixed on the pressure plate 15 is also stationary, and therefore the compact compressed in the cavity C is pushed out of the die 1 by the lower punch 3. It is pushed up and punched out from the mold.

Japanese Utility Model Publication No. 58-143837 discloses a means for preventing galling of the core rod by the molded body during this drawing, which reduces the life of the mold.

[Problem to be solved by the invention]

The molded body obtained by the above method may have uneven thickness in the direction of reciprocating movement of the feeder 6. That is, assuming that the direction in which the feeder 6 reciprocates is A-B as shown in FIG. 8, which is a partially enlarged view of FIG. 7, the hollow cylindrical molded body 30 as shown in FIG. , in the A-B direction, the wall thickness of the R section is 1. There may be a difference between the thickness t2 of the R2 portion and the thickness t2 of the R2 portion. Therefore, in order to prevent this, various measures have been taken, such as examining the size of the feeder 6 with respect to the die 1, examining the stop position of the feeder, and installing an auxiliary plate inside the feeder.

However, in the part shape shown in Fig. 9,
It is difficult to prevent uneven thickness in parts with thin walls.

The following points can be considered as the main reasons why uneven thickness cannot be prevented in this thin-walled part.

(1) As the parts become thinner, the lower bunch 3 also becomes thinner to match the shape of the part, so that when filling the cavity C with raw material powder, it is difficult to enter the cavity.

(2) The density of the raw material powder that has entered the cavity is somewhat coarser than that of ordinary parts, so when the raw material powder is scraped by the return movement of the feeder 6 after supplying the raw material powder, In the A-B direction of Fig. 8, the raw material powder is transported from the B side to the A side, and the space between the cavities 01 and 02 becomes dense and dense, and after compression molding, as shown in Fig. 9. In this case, the area between the R7 part and the R2 part of the part becomes dense.

As mentioned above, for parts with thin walls, it is difficult to eliminate uneven thickness during powder molding using conventional technology, so after pressing, it is necessary to add machining to the compact to correct the deflection. This results in an increase in costs.

In view of the above-mentioned problems, an object of the present invention is to provide a powder molding mold that does not cause uneven thickness even when molding thin-walled parts.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a forming apparatus for thin-walled powder metallurgy parts having a center hole, in which a stopper is provided between the lower part of the supporter supporting the core rod and the lower ram base plate. The depth of the cavity between the top surface of the die and the top surface of the core rod is set to a predetermined depth depending on the shape of the molded body by changing the height of the stopper. A mold for powder molding is provided.

[For production]

When the height of the stopper provided between the lower part of the supporter that supports the core rod and the lower ram base plate is changed by a predetermined value, the depth of the cavity between the top surface of the die and the top surface of the core rod changes as described above. It changes by an amount equal to the amount of change in the height of the stopper.

The height of the stopper is finely adjusted and set to be equal to the depth of the cavity, which has been set in advance according to the shape of the molded object, and the thickness deviation is less likely to occur. get.

〔Example〕

When powder molding a thin cylindrical part having a center hole, the die 1 is
After investigating the relationship between the depth H of the 9 cavities from the top surface to the top surface of the core rod 4 and the thickness unevenness described above, it was found that thickness unevenness can be prevented by changing the dimension of the depth H. .

An example of the results of this investigation is shown in Figure 6.

In the figure, the vertical axis shows uneven thickness (tl-t2) mm (
(see FIG. 9), and the horizontal axis represents the depth of the cavity (hereinafter simply referred to as cavity depth) between the top surface of the die and the top surface of the core rod, Hmm. In the figure, curve I: t, 10 = 0.25-0.40 curve II
: t, /D=0.13-0.15 curve III:
tl/D=0.10~0.13 curve ■: t,/D=
0.05 to 0.10, and the thickness deviation -8 curves differ depending on the shape of the molded product, that is, the range of 1+10. Also, according to this, the I curve, that is, the wall thickness is t+/D=
For those of 0.25 to 0.40, H=0 to 0.4
Within the range of , the deflection (t+ t2) is t+ ta=0
The maximum thickness is about 0.01 mm around the center, and at this level, there is no need to perform machining to correct the uneven thickness as described above.

However, when the wall becomes thinner and reaches the range of thin-walled parts targeted by the present invention, which is represented by curves After that, as H increases, the thickness deviation decreases, and at a certain value of H, the thickness deviation becomes O<zero.Thereafter, as H increases, the negative thickness deviation tends to increase. As a practical matter, the tolerance range for thickness deviation that does not require machining for correction after processing is ±0.03 to 0.04.
As long as it falls within the range of mm, we can think of it the other way around and fit each of the curves ■ to ■ within this range.
The range in which the depth H of the cavity should be maintained during processing can be determined from the diagram in FIG. 6.

For example, according to FIG. 6, in the case of curve (2), in order to keep it within this range, the value of H should be approximately within 0.05 to 0.3D+nm. Therefore, in order to set the depth H that does not require correction of uneven thickness, it is necessary to set the depth H from 0 to 0.4 m.
0.01 m for cavity depth H within m
It is desirable to be able to make fine adjustments in m increments.

In order to satisfy the above conditions, a mold that allows fine adjustment of the depth H of the cavity as described above is required. Examples of molds that satisfy these conditions will be described below.

A first embodiment is shown in FIGS. 1 and 2. In the figure, the same names and numerals are given to the 0 parts common to those in the above-mentioned FIG. 7, and detailed explanations are omitted. 1 is the die, 2 is the die plate, 3 is the lower punch, 4 is the core rod, 5 is the spring,
7 is an upper bunch, 8 is a core rod supporter, 11 is a base plate, 14 is a guide bar, 15 is a pressure plate, and 16 is a press lower ram.

This embodiment differs from the conventional example in that a mechanism for adjusting the depth H of the cavity C is provided between the core rod supporter 8 and the base plate 11. This uses a worm gear that combines a worm 21 to pass through and a worm wheel 22 as shown in the figure, and a female thread 23 is provided at the axial center of the worm wheel 22, and a male thread 24 is screwed into this.
A stopper 25 having a diameter is engaged with the center of the worm wheel 22. The upper end surface 25a of the stopper 25 is in contact with the lower end surface 8a of the core rod supporter 8. Handle 2
0 rotates the worm 2■, which rotates the worm wheel 22, which causes the stopper 25 to move up and down via the screw mechanism, which moves the core rod 4 up and down via the core rod supporter 8, thereby causing the cavity C to move up and down. Adjust the depth H. For example, if the depth of the cavity C is H when the height from the base plate top surface 11a to the stopper top surface 25a is Hl, if you want to make this H slightly deeper, for example by Δh+++m (H-+H
+Δh), turn the handle 20 to lower the height Hl of the stopper 25 by Δhmm (H).

→H1-Δh). In this way, according to this mechanism, the depth H can be minutely and continuously adjusted by the combination of the worm gear and the screw mechanism, and the sixth
The shape of the molded object at that time, using the diagram shown in the figure,
In other words, depending on the values of t and /D, the deflection range (±0.03 to 0.0
41TIm), and the vertical position of the core rod 4 is appropriately set using the height adjustment mechanism of the stocker 25 so that the depth H is within the range of 41TIm).

Next, a second embodiment is shown in FIGS. 3 to 5. In this case, it is not necessary to change the value of the depth H continuously as in the first embodiment, but it is sufficient to set an arbitrary value stepwise, for example, every 0.10 mm. The structure is simpler than that of the first embodiment. As shown in FIG. 3, this is fixed to the base plate 11 by a spacer 27 and a stopper 28 at a position where the spacer 27 sandwiches the stopper 28. The height Ha of the spacer 27 is the thickness Hl of the stopper 28
The stopper 28 has various heights, for example, 0.10 m, in stages corresponding to the depth H of the cavity C.
It is prepared every m. This stopper 28 of various heights
A stopper 28 having a height H8 that matches the required depth H of the cavity is selected from among the stoppers 28, and the stopper 28 is attached to the core rod supporter 8 and base plate 11 as shown in FIG.
By inserting between
is set. This depth H is further increased to, for example, 0.10 m.
If you want to make it deeper by m (H-Hl 0.10 mm), slide and remove the stopper 28 of the previous thickness Hl. At this time, since the core rod supporter 8 is urged downward by the spring 5, it moves downward by (L Ha), and the supporter 8 directly hits the spacer 27 as shown in FIGS. 4(a) and 5(a). The lower end surface 8a of is in contact with the lower end surface 8a. Next, a stopper 28a with a thickness of Hla" (Hlo, 10) mm
4(b) and 5(b), push the wedge-shaped tip under the core rod supporter 8 between the spacers 27, and then tighten the stopper 28 with the stopper pin 29.
Fix a.

In this state, the supporter 8 has a thickness of l11. = (H, -0
, 10) mm, thereby making it possible to change the depth H of the cavity C from the top surface of the die 1 to the top surface of the core rod 4 to )Ia=(Hl0.10) mm.

As a conventional method for changing the depth H of the cavity from the top surface of the die 1 to the top surface of the core rod 4, which does not involve the above method, for example, when the center hole of the part is a simple circle,
The total length r of the core rod 4 may be arbitrarily set to 4 and replaced, but in this case, it is necessary to remove the core rod 4 for alignment, which increases the time required to change mold setups and reduces productivity. Therefore, it is not realistic.

By using the mold according to the embodiment of the present invention, it becomes possible to easily prevent thickness unevenness of thin-walled powder metallurgy parts having a center hole without the above-mentioned effort, and machining is omitted. Cost reduction can be achieved. In addition, the adjustment time for preventing uneven thickness can be kept to a few minutes, and adjustments can be made without reducing productivity.

Note that the structure for changing the height of the stopper is not limited to the structure described in the above embodiment. For this purpose, not only a mechanical mechanism but also a mechanism using electromagnetism, fluid pressure, etc. may be used as long as the height of the stopper can be easily finely adjusted.

〔Effect of the invention〕

Implementation of the present invention provides the following effects.

(1) It is possible to easily prevent uneven thickness during press working of thin powder metallurgy parts having a center hole, and machining to correct uneven thickness can be omitted, resulting in cost reduction.

(2) Productivity is improved because the settings of the device for preventing uneven thickness can be adjusted in a short time according to the various dimensions of the molded product.

(3) The quality of the product is improved because the above adjustment allows fine adjustment with high precision.

[Brief explanation of drawings]

Figure 1 is a front view of the entire mold of the first embodiment of the present invention, and Figure 1 is a front view of the entire mold of the first embodiment of the invention.
The figure is a partial side view of Figure 1, Figure 3 is a front view of the entire mold of the second embodiment, and Figure 4 is a partial side view of the mold showing the operation of inserting the stopper in the second embodiment. , (a) is before insertion, (
b) shows the state after insertion, and FIG. 5(a) shows the state after insertion.
), FIG. 5(b) is a partially enlarged perspective view of FIG. 4(b), and FIG. 6 is a partial enlarged perspective view of FIG. Diagram showing the relationship between the parts, Fig. 7 is a front view of the entire mold of the conventional example, Fig. 8 is a partially enlarged view of Fig. 7, and Fig. 9 is a hollow cylinder formed by the mold of the conventional example. The forming feature is shown. 1...Gui, 1a...Top surface of die, 4
...Core rod, 4a...Top surface of core rod, 8...Core rod supporter, 11...Base plate, 25.28, 28a...Stopper, 30...Molded object, 40...For powder molding Mold, C...cavity, H...cavity depth.

Claims (1)

[Claims] 1. A molding device for thin-walled powder metallurgy parts having a center hole, in which a stopper is disposed between the lower part of the supporter supporting the core rod and the lower ram base plate, and the height of the stopper is changed to mold the die. A mold for powder molding, characterized in that the depth of the cavity between the upper surface and the upper surface of the core rod is set to a predetermined depth depending on the shape of the compact.