JPS62130797A - Forming method for green compact by rubber press - Google Patents

Abstract

PURPOSE:To increase the production efficiency by forming a long sized green compact with slowly enlarging the maximum pressurizing part by facing it in the end part direction. CONSTITUTION:The rubber 10 of a rubber press device is formed by dividing into numerous small chambers 11-17 having numerous doughnut shapes. A core bar 21 is provided inside a rubber mold and a raw material powder 1 is charged in as well and after fitting a cap 22 charged into the high pressure container 4 of the rubber press device. Then, the maximum forming pressure is poured into the small chamber 14 at the center part of the rubber mold first, and the maximum forming pressure is led into the adjoining small chamber 13, 15... in order. In this case, the compacting is started from the raw material powder at the center part of the rubber mold and the air existed at the center part is expelled to the upper or lower and reaches to the upper and lower both ends. Due to the residual air being reduced by this method the breakage of the forming body due to the air expansion is eliminated and the forming time can be shortened. Consequently the production efficiency is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a molding method using a rubber press, and particularly to a method suitable for molding green compacts of elongated members such as pipes.

[Prior art 1 Ceramics are usually manufactured by a process in which raw material powder is shaped by an appropriate method and then sintered. Mud casting method (slip casting), extrusion molding, Ru, Mud casting and extrusion molding methods require a drying process after molding because a large amount of water is added to the raw powder, which prevents cracks during drying. It is difficult to control the drying shrinkage amount. Furthermore, according to the injection molding method, it is necessary to add a relatively large amount of synthetic resin, the degreasing process is difficult, and there is a limit to the molding of thick objects. The die molding method is a method in which a small amount of binder is added to powder and the powder is pressed in a die to obtain a green compact that maintains appropriate strength. According to this mold forming method, objects with fairly complex shapes can be molded with high precision, but due to the low fluidity of the ceramic powder inside the mold, pressure transmission inside the mold during pressurization is difficult. This tends to result in uneven density in the resulting green compact, which results in some distortion or deformation after firing.

According to the rubber press molding method, such drawbacks of mold pressing can be improved and a sintered body with higher precision can be obtained. This rubber press molding method I+ Yu+me I-F Chapter 1
kbshi Barney's old pipe Lψ-1栖 The capture is to obtain a green compact by applying pressure to a rubber mold through a pressure medium such as water. This rubber press molding method is roughly divided into two methods, the wet bag method (Type 21 method) and the dry bag method (dry method).

The wet bag method is a method in which a rubber mold is placed in liquid and liquid pressure is applied from the outer periphery, and the mold is directly exposed to the liquid pressure. FIG. 2 is a schematic sectional view schematically explaining the rubber press method of the wet bag method. As shown in Figure (a), first, a raw material powder is prepared and filled into a rubber mold 2.The rubber mold 2 is then covered with a lid 3 and charged into a high-pressure container 4. Reference numeral 5 indicates a liquid. After that, pressure is applied to the liquid 5 as shown in the figure (b), and the liquid pressure is applied uniformly from the outer layer of the rubber mold 2. Reference numeral F indicates this liquid pressure, and reference numeral 6 indicates the lid of the high-pressure container. After releasing the liquid pressure as shown in FIG. The powder compact 7 is obtained by taking out the mold 2 and removing M3 from the mold 2.

Furthermore, the dry bag method is a method of molding using a high-pressure container with rubber that seals against hydraulic pressure. FIG. 3 is a schematic cross-sectional view showing the schematic structure of this dry bag method. In this dry bag method, rubber mold 2
is filled with powder 1, and loaded into a high-pressure container 4 equipped with a rubber tube 8 that seals against hydraulic pressure as shown in (b), and then (C) applies hydraulic pressure to the outside of the rubber tube 8 as shown in the figure. The rubber mold 2 is pressed through the rubber tube 8 and the raw powder l is pressurized to form a green compact.Then, as shown in the diagram (C), the rubber mold 2 is taken out from the pressure vessel 4 and the green compact is formed. Get 7.

Incidentally, reference numerals 9 and 10 in the figure indicate molds, which are arranged at both ends of the rubber mold 4 as shown in the figure, and hydraulic pressure is applied from the side surfaces of the rubber mold 4.

[Problems to be solved by the invention] In the rubber press method using the wet bag method, hydraulic pressure is applied from the entire circumference of the rubber mold, so the air remaining in the rubber mold cannot be removed, and the remaining compressed air cannot be removed. Therefore, destruction may occur after molding, or sufficient pressure may not be applied.

Further, even with the dry bag method, air is not removed sufficiently and destruction may occur due to air. Particularly in elongated members whose length is, for example, In or more, air removal tends to be insufficient.

In order to prevent the molded product from being destroyed due to the expansion of air remaining in the green compact, high pressure must be applied carefully and slowly over time, resulting in poor molding efficiency.

[Means for Solving the Problems] In the molding method using a rubber press of the present invention, when molding a long green compact, the maximum pressure area is gradually expanded in the direction of the end of the rubber mold. It is characterized by

[Function] According to the molding method of the present invention, for example, the maximum pressurizing part is first set in the central part of the rubber mold, and this maximum pressurizing part gradually expands. As the maximum pressure area expands, the air gradually moves toward the end of the rubber mold, resulting in a compacted powder with very little residual air. It is possible to obtain a body.

Of course, in the present invention, the maximum pressurizing part may be first set at one end of the rubber mold, and then expanded toward the other end.

[Examples] The present invention will be described in more detail below with reference to examples shown in the drawings.

FIG. 1 is a vertical sectional view showing a schematic configuration of an apparatus used in a rubber press molding method according to an embodiment of the present invention. In this rubber press device, the rubber lO that transmits hydraulic pressure is composed of many ring-shaped parts, and small chambers 11, 12, 13
...It is divided into 17 parts. Each small room 11.12.13
...17 has a donut shape and is configured so that hydraulic pressure can be introduced separately from the adjacent small chambers. Furthermore, a partition wall 4a protruding from the inner circumferential surface of the pressure vessel 4 is interposed between each rubber lO, so that the pressure in each of the small chambers 11 to 17 is not substantially transmitted to the adjacent chamber. .

FIG. 4 is a sectional view showing the structure of a rubber mold 20 inserted into this rubber press apparatus.

In this embodiment, a pipe-shaped green compact is molded, and a core bar 21 is inserted into a rubber mold 20. Also, both upper and lower ends of the rubber mold 20 have caps 2.
It is said that it can be sealed in 2.23.

In order to mold a green compact using this rubber mold 20, first remove the cap 22, and then press the rubber mold 20.
The rubber mold 20 is charged into the high-pressure container 4 of a rubber press machine as shown in FIG. The powder 1 is pressurized by introducing hydraulic pressure into each of the chambers 11, 12, . . . , 17.

This pressurization process will be explained in detail with reference to FIG. First, hydraulic pressure is introduced into each chamber 11, 12, . . . , 17 so that the pressure is the same (FIG. 5(a)). Next, the maximum molding pressure is introduced into the small chamber (14 in Figure 1) located at the vertical center of the rubber press (see Figure 5(b)).
After a predetermined period of time has elapsed, the maximum molding pressure is introduced into the adjacent small chamber 13.15, and this procedure is repeated to sequentially increase the maximum molding pressure toward both the upper and lower ends of the rubber mold 20 (Figs. 5(c) and 5(d)). )reference). When such pressure molding is performed,
Consolidation starts from the raw material powder located in the vertical center of the rubber mold 20, and the air that existed in the center is forced upward or downward by the maximum molding pressure, and finally the rubber mold reaches both the upper and lower ends of 20. After introducing the maximum molding pressure to the small chambers 11 and 17, it is maintained for a predetermined time, and then each chamber 11, 12...1
Release the molding pressure in step 7. Then, the rubber mold 20 is taken out from the rubber press device, the cap 22 or 23 is removed, and the green compact 24 is taken out.
The figure is a sectional view showing the state when the rubber mold 20 is taken out of the rubber press apparatus, and FIG. 7 is a perspective view showing the shape of the green compact 24 taken out from inside the rubber mold 20.

As shown in FIG. 5, in this embodiment, the maximum molding pressure is first introduced into the small chamber 14 in the central portion of the rubber mold, and then the maximum molding pressure is introduced into the adjacent small chambers 13, 15, etc. There is. However, in the present invention, the maximum molding pressure may be introduced into the small chambers 11 or 17 at the upper end or the lower end, and then the maximum molding pressure may be introduced into the upper or lower chambers in sequence. The air inside is sequentially forced from the upper end or lower end toward the lower end or upper end. However, in the present invention, it is preferable to first introduce the maximum molding pressure to the central portion as in the embodiments described above, since the distance traveled by the air within the rubber mold is small and the molding time is also short.

Further, in the above embodiment, uniform pressure is first introduced into each of the small chambers 11, 12...17, and then some of the small chambers (for example, 14
), but *-PI3-k乍1〆1191. % Yin cup mt-4171% #
L l l? .

Furthermore, a pressure slightly lower than the maximum molding pressure is introduced into the small chamber 14, and a molding pressure slightly lower than the maximum molding pressure is sequentially introduced into the adjacent small chamber 13.15 and up to the small chamber 11.17, and then the small chamber 14 The maximum molding pressure may be introduced into the small chambers, and the maximum molding pressure may be sequentially introduced into the adjacent small chambers.

Further, although in FIG. 5, equal pressure is first introduced into each of the small chambers 11-17 (FIG. 5(L)), molding may be started without introducing such equal pressure.

The molding method of the present invention is applicable not only to pipe-shaped moldings as shown in the figure, but also to cylinder-shaped moldings and container-shaped moldings as shown in FIG.
etc. can also be molded.

In the present invention, as the material constituting the rubber mold, in addition to rubbers such as natural rubber, urethane rubber, and neoprene rubber, synthetic resins having appropriate flexibility may also be used.

In addition to water, oils, organic substances such as glycerin, or low melting point metals such as mercury may also be used as the pressure transmission medium.

In addition, in the present invention, air moves in the rubber mold toward the end and is vented from the end of the mold, but a hole is provided in the cap 22.2 to facilitate air venting.
3 and the caps 4A and 4B of the high pressure vessel 4. Also, when filling raw material powder into a rubber mold.

Uniform filling is possible by applying vibration to the mold.

In the above embodiment, seven small rooms are provided.

Other numbers may also be used. Furthermore, the present invention can be applied to any rubber press device other than that shown in the drawings, as long as the maximum pressurizing portion can be set at an arbitrary location.

[Effects of the Invention] As detailed above, the rubber press molding method of the present invention is characterized in that the portion to which the maximum molding pressure is applied is sequentially expanded toward the end, thereby producing green compacted powder with an extremely small amount of residual air. You can get a body.

Furthermore, according to the method of the present invention, there is no destruction of the molded product due to the expansion of residual air, so the pressure inside the rubber press can be quickly reduced, the molding time can be shortened, and production efficiency can be greatly increased. It is believed that a significant increase is possible. The present invention is extremely suitable for manufacturing elongated members having a length of 50 cm or more, especially 1 m or more.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a rubber press forming apparatus used in an embodiment of the present invention, FIGS. 2 and 3 are cross-sectional views explaining a conventional rubber press method, and FIGS. The figure is a cross-sectional view explaining an example of the rubber press molding method of the present invention, Figure 5 is a graph showing the method of applying the maximum molding pressure, and Figures 7 and 8 are green compacts obtained by the method of the present invention. It is a perspective view showing the shape of. ■...Raw material powder, 4...High pressure container. 1o08. Rubber, 2o...Rubber mold,
21... Core metal. (a) (b) Figure 2 (a) Figure 3 (c) (d) Figure 4 Small room numbers. Figure 6 Procedure? City official document (Procedural amendment pursuant to the provisions of Article 17-2, Item 1 of the Patent Law) February 1986/2. Day

Claims (1)

[Claims] (1) A forming method using a rubber press, which is characterized in that when forming a long green compact using a rubber press, the maximum pressure area is gradually expanded in the direction of the end.