JPH04371804A - Molding tool for cold hydrostatic press and manufacture of molded product for which that tool is used - Google Patents

Abstract

PURPOSE:To provide a molding tool for a cold hydrostatic press which is capable of molding a complicated formed product having a desired form and dimensions which is hard to manufacture if a core mold is not used by a simple process and a manufacture of a molded product for which that tool is used. CONSTITUTION:A molding tool for a cold hydrostatic press is constituted of a molding tool 3 comprised of water-permeability porous resin for filling a powder body and a core mold 8 having an air introducing hole 8b. Elastic films 5, 6 are formed in a thin filmy state on inner walls of the molding tools 3 and core mold 8. Then the powder body is filled into the inside of the elastic films 5, 6 through a powder body filling hole 11 and held in an airtight state. Then the inside of the elastic film is kept under negative pressure. Then the powder body is pressed, molded and shape retaining is performed. Then air is introduced through an air introducing hole 8b of the core mold 8, the core mold 8 is released form the tool and kept under static pressure. Then water is permeated into the inside of the molding tool through the porous resin from the outside of the molding tool, the elastic film with which the inner wall of the molding wall is coated is peeled off and the pressed powder body surrounded with the elastic film is press-molded evenly on the whole circumferential surface.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for cold isostatic pressing and a manufacturing method for manufacturing molded products using the same.

0002

2. Description of the Related Art Conventionally, the following method is generally known as a method for forming ceramic or metal powder by cold isostatic pressing. ■ A method of cold isostatic press molding by placing a molded body preformed by press molding, injection molding, etc. into a thin rubber mold or rubber bag; A method of forming a thin airtight film on the surface with latex etc. and cold isostatic press molding, ■
A method of placing powder in a rubber mold, sealing it, applying cold isostatic pressing, and processing the resulting molded product into the desired shape. ■Powder is placed in a rubber mold of the desired shape. A method of placing a rubber bag along the inner wall of a metal or plastic shape-retaining frame with many holes for shape-retaining, and placing the powder inside the rubber bag. There is a method in which the material is sealed, cold isostatically pressed, and then molded.

0003

However, such conventional cold isostatic presses have the following problems. That is, according to the method (1) or (2) above, a step of preforming the green compact is required, which increases the number of man-hours for manufacturing the molded product. The method (2) requires processing after cold isostatic pressing, which complicates the post-processing work and increases the amount of raw materials used, which increases costs. According to the method (2) above, if the thickness of the rubber mold having the desired shape is made thin, it is difficult to maintain the shape, and if the rubber thickness is made thick, a large amount of processing is required to obtain the desired shape. In the method (2) above, the shape-retaining frame only works by bending the rubber bag, so it cannot be formed into a complex shape, and there is a problem that it is difficult to make the molded product into the desired shape and dimensions without extensive processing. .

The present invention has been made to solve these problems, and it is possible to produce molded products with required shapes, dimensions, and complex shapes that are difficult to manufacture without using a core through a simple process. The object of the present invention is to provide a mold for cold isostatic pressing that can be manufactured at low cost and a method for manufacturing molded products using the same.

[0005]

[Means for Solving the Problems] A mold for cold isostatic pressing according to the present invention to achieve the above object includes a mold made of a water-permeable porous resin for filling powder, and a mold for filling the mold with water permeable porous resin. A core mold made of a water-permeable porous resin and having an air introduction hole on the inner wall surface through which air can be introduced, and a non-water-permeable material such as rubber or synthetic resin formed in a thin film on the inner wall of the mold. and an elastic coating formed in the form of a thin film on the inner wall of the core mold.

[0006] The method for manufacturing a molded article using a mold for cold isostatic pressing according to the present invention includes a mold made of a water-permeable porous resin and a core made of a water-permeable porous resin combined therewith. a step of forming an elastic coating on each inner wall of the mold; a step of filling the mold with the elastic coating with powder and keeping the powder airtight with the elastic coating; and a step of forming an elastic coating on the inside of the elastic coating. a step of removing the core mold, and a step of uniformly pressurizing the green compact and the mold containing the elastic coating under cold isostatic pressure. It is characterized by having the following.

[0007] In the step of converting the powder into a green compact according to the above manufacturing method, for example, a syringe needle is inserted into the powder through the elastic coating, and the air inside the elastic coating is sucked to create a negative pressure on the powder side. Can be done. Further, in the step of converting the powder into a green compact according to the manufacturing method, air can be blown through the air introduction hole of the core mold to peel off the elastic coating from the inner wall surface of the core mold.

[0008]

[Function] When the mold for cold isostatic pressing of the present invention is used, since the mold and core mold are made of porous resin, water permeates from the outside of the mold to the inside of the mold, and from the inner wall of the mold. The elastic coating is peeled off and pressure is applied uniformly to the entire outer periphery of the powder inside the elastic coating, making it possible to mold products with complex shapes in a simple process.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. First, a mold for producing a bottomed cylindrical ceramic molded body by cold isostatic pressing will be described. As shown in FIG. 1, the mold 1 consists of a core mold 8 having a cylindrical projection 8a, and a cylindrical mold 3 assembled around the projection 8a via a cavity. Both materials are made of water-permeable porous resin. This porous resin is a porous body made of a polymer compound with an average pore diameter of 30 to 50 μm. The mold 3 is made of porous resin because during cold isostatic pressing, water is infiltrated from the outside from the outside wall of the mold to the inside wall of the mold, and the film coated on the inside of the mold is removed from the mold. This is to apply hydrostatic pressure to the powder inside the mold while exfoliating it. Since this mold 1 is made of porous resin, it is not only lightweight and easy to handle, but also the pore distribution of the porous resin can be easily made uniform, allowing even pressure to be applied to the powder inside. . Core type 8 is
The protrusion 8a has an air introduction hole 8b, and a plug 9 can be fitted into the opening. By using the core mold 8, the internal shape of the molded product is maintained, so that a complex-shaped molded product with good dimensional accuracy can be obtained. Molding mold 3 and core mold 8
The material is not limited as long as it satisfies the main strength, and it is also possible to use a porous body of metal or ceramic. The average pore diameter of the porous resin constituting this mold is preferably 50 μm or less. This is because if the pore size is too large, when forming an elastic coating such as latex, which will be described later, it will be impregnated too deeply into the pores of the porous resin during coating, causing the elastic coating to peel off. This is to prevent it from becoming difficult.

[0010] Then, a latex whose viscosity has been adjusted is applied to the molding surfaces as the inner walls of the core mold 8 and the mold 3.
The elastic coatings 5 and 6 have a thickness of 1 mm or less, preferably 0.3 to
Form to 0.8 mm. The viscosity of the applied latex is adjusted so as not to impregnate the interior of the porous resin core mold 8 and mold 3 more than necessary. Through the above steps, the mold is completed.

Next, the process of cold isostatic pressing using the core mold 8 and mold 3 described above will be explained. Powder is filled through the powder filling hole 11 of the mold 3 shown in FIG. In order to increase the packing density when filling the powder, it is desirable to use a vibrator, and the cavity surrounded by the elastic coatings 5 and 6 is tightly filled with the powder. After filling the powder, as shown in FIG. 2, a felt 12 is inserted so as to close the powder filling hole 11.
An elastic body having a filtering function such as the above and a rubber stopper 13 are attached, and the powder filling hole 11 is sealed with an elastic coating 14 made of latex from above the rubber stopper 13. Next, a syringe needle (not shown) is inserted into the elastic coating 14 and the rubber stopper 13, and the syringe needle is sucked using a vacuum pump so that the powder 15 side becomes negative pressure. At this time, air is introduced into the air introduction hole 8b of the core mold 8,
The elastic coating 5 is separated from the inner wall surface of the core mold 8. Thereafter, the injection needle is removed, and the exit hole is sealed with vinyl tape (not shown). Next, the core mold 8 is released before cold isostatic press molding. Then, the result becomes as shown in FIG.

After releasing the core mold 8, the powder 15, which is airtightly held by the elastic coatings 5 and 6, and the mold 3 are placed under hydrostatic pressure in the state shown in FIG. Then, water enters the porous mold 3 from the outer wall side to the inner wall side, and the hydrostatic pressure gradually increases. Then, water enters between the elastic coating 6 and the inner wall of the mold 3, and the powder 15 contracts with the elastic coatings 5 and 6 in close contact with the outer periphery of the powder 15, and is surrounded by the elastic coatings 5 and 6. The resulting powder 15 is uniformly pressure-molded.

In this case, a compact of the powder 15 with high dimensional accuracy can be obtained. Moreover, since the thin elastic coatings 5 and 6 are used, the powder 15 is uniformly pressurized and no cracking or deformation occurs. After pressure molding, the hydrostatic pressure is removed. and,
The powder 15 wrapped in the elastic coatings 5 and 6 is taken out and the elastic coatings are removed to obtain a molded article.

[0014] In addition to the above-mentioned coating method, the elastic film can be formed by (1) spraying, (2) covering the inner wall of the mold with a thin, water-impermeable film with excellent extensibility, and leaving the inside of the mold under pressure. Pressure is applied, and the powder is filled inside the film while keeping the film in close contact with the inner wall surface (molding surface) of the mold.
Method of molding after sealing the outside of the powder with a film, ■
An elastic film mold is made in advance from thin rubber or the like in the shape of a molded object, this mold is held along the inner wall of the mold, the inside of the mold is then filled with powder, the powder is sealed with the elastic film mold, and then molded. There are methods etc. As for the material of the elastic coating, it is desirable to use latex, rubber, or water-impermeable synthetic resin having the required extensibility, strength, etc.

[0015] According to the cold isostatic press according to the above embodiment, since the mold 3 and the core mold 8 are made of water-permeable porous resin, molded products with complex shapes can be easily formed. Since the mold 3 and the core mold 8 are made of resin, they are lightweight and easy to handle, and it is also easy to adjust the pore diameter of the porous resin and manufacture a mold with uniform distribution. In addition, since the elastic coating is formed by coating or coating the mold along the inner surface of the mold, it not only has good shape retention but is also easy to make thin as mentioned above, and the simple sealing method using this elastic coating makes it airtight. can ensure sex. Furthermore, according to this embodiment, it is possible to mold a large, complex-shaped product, and a final product close to a finished product can be easily produced by cold isostatic pressing. Thereby, the amount of raw materials used and finishing processing can be significantly reduced, and manufacturing costs can be reduced.

[0016]

Effects of the Invention As explained above, according to the mold for cold isostatic pressing of the present invention, since the mold and core mold are made of water-permeable porous resin, it is possible to move from the outside of the mold to the inside of the mold. A mold for cold isostatic pressing with excellent moldability can be obtained because water is allowed to permeate through the powder and uniform pressure can be applied to the powder through the elastic coating coated inside the mold.

According to the cold isostatic press according to the present invention,
An ideal molded body can be obtained that is uniformly pressurized inside the porous mold, and a complex, dense, and homogeneous molded body can be obtained at low cost through a simple manufacturing process.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a mold for explaining the cold isostatic press of the present invention.

FIG. 2 is a schematic cross-sectional view showing a mold for explaining the cold isostatic pressing process of the present invention.

FIG. 3 is a schematic cross-sectional view showing a mold for explaining the cold isostatic pressing process of the present invention.

[Explanation of symbols]

1 Molding mold 3 Molding mold 5, 6 Elastic coating 8 Core mold 8a Air introduction hole 15 Powder

Claims (4)

[Claims] 1. A mold made of a water-permeable porous resin, a core mold made of a water-permeable porous resin combined with the mold and having an air introduction hole through which air can be introduced into an inner wall surface, and said mold. A mold for cold isostatic pressing, comprising: an elastic coating formed in the form of a film on the inner wall of the mold; and an elastic coating formed in the form of a film on the inner wall of the core mold. 2. A step of forming an elastic coating on each inner wall of a mold made of a water-permeable porous resin and a core mold made of a water-permeable porous resin combined therewith; A process of filling powder into a mold and airtightly holding the filled powder with an elastic coating, a process of putting the powder inside the elastic coating under negative pressure to form a green compact, and removing the core mold. and a step of uniformly pressurizing the powder compact into a mold containing the green compact and an elastic coating under cold isostatic pressure. A manufacturing method for molded products. 3. Claim 2, wherein in the step of converting the powder into a green compact, negative pressure is applied to the powder side inside the elastic coating.
A method for manufacturing a molded product using the cold isostatic pressing mold described in . 4. In the step of converting the powder into a green compact, air is blown through the air introduction hole of the core mold to peel off the elastic coating from the inner wall surface of the core mold. 2. A method for producing a molded product using the cold isostatic pressing mold described in 2.