JPS61235101A - Slurry casting molding method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of casting a slurry of ceramic, metal, cermet, etc. into a water-absorbing mold and solidifying it.

[Conventional technology]

The cast molding method is a method of obtaining a molded article by pouring slurry into a water-absorbing mold to form an ink layer.

This molding method has the characteristics of being able to mold products with complex shapes, and is suitable for small-scale production because the equipment costs for molding are low, making it suitable for molding clay-based materials such as ceramics and sanitary ware. It is widely used. Recently, it has also been used for non-clay ceramic materials such as alumina, magnesia, zirconia, ferrite, silicon carbide, and silicon nitride. Application to metal cermets has also been attempted.

Gypsum is generally used as a water-absorbing mold for cast molding. Plaster molds can accurately copy even the finest patterns on a model and have excellent water absorption properties, but they do have some problems. That is, (1) the time required from casting the slurry to taking it out as a molded body is long. It is also possible to increase the speed of dewatering by pressurized casting, but the plaster mold is weak, so applying pressure is almost impossible.

(2) For non-clay ceramics, metals, and cermets,
There is no or little shrinkage due to dehydration, and fine particles enter the pores of the plaster mold, making it difficult to release the molded product from the mold and easily causing mold release defects.

(3) It takes a long time to dry the plaster mold after releasing it from the mold.

(4) Gypsum has poor wear resistance and dissolves in extremely acidic or alkaline slurry, resulting in a short mold life.

There are drawbacks such as. On the other hand, in order to improve the lifespan, it is known to use molds made of resin, calcium silicate, or fiber-reinforced composite materials, but these are expensive, and are inferior to plaster molds in terms of water absorption and mold releasability.

A method is also known in which dry powder, for example alumina powder, is compacted to form a mold, the cast-molded hindlimb powder is crushed, the molded body is taken out, and the powder is dried and reused. . According to this method, mold release is relatively easy, and drying of the mold is replaced with drying of the powder, so the drying time can be significantly shortened. However, on the other hand, there are severe restrictions on the properties of the powder. In other words, in order to create a solid mold that does not cause mold formation, it is necessary to increase the particle size of the powder, but if the particle size is increased, not only will the slurry penetrate between the particles, causing poor mold release, but also the rate of water absorption will decrease. . For this reason, a compromise has been made by using powder with a particle size close to that of the powder constituting the slurry.

Another problem lies in the mold manufacturing method. In other words, when manufacturing molds by tamping, there is a limit to the shapes that can be manufactured.
It cannot be applied to complex shapes.

[Problem that the invention seeks to solve]

The purpose of the present invention is to provide a slurry casting method that can solve the problems of the conventional casting method as described above, and enables a significant reduction in molding time and the repetition of a mold material with good mold releasability. It is something to do.

[Means for solving problems]

The present invention is a slurry casting method in which a mold is constructed of a swellable powder, slurry is poured into the mold, and the powder absorbs water in the slurry, thereby dehydrating and hardening the slurry to form a molded body. This is a method of molding the swellable powder into a desired mold shape.

Further, a swellable powder is sealed in a closed space in a desired mold shape, the main part of which is a film and a filter, with at least the wall constituting the cavity being a water-soluble film, and the swelling powder is encapsulated by suction from the filter part. This is a slurry casting method that involves applying negative pressure to a closed space to maintain the shape and form a mold.

[Effect]

The swellable powder in the present invention is selected from acrylic acid/vinyl alcohol copolymer, sodium acrylate polymer, sodium acrylate/acrylamide copolymer, starch-based graft polymerization of acrylic acid, etc. Since it is a mixed powder of a water-absorbing swelling powder or a non-water-absorbing swelling powder and the above-mentioned water-absorbing swelling powder, it becomes a filler with voids in a dry state, has water absorption, and the particles swell due to water absorption. Swellable powders are powders that are easily plastically deformed, but do not form chemical bonds between particles.

In addition, this powder has a water absorption capacity of 20 to 50 liters (moisture)/
For example, the water absorption capacity of the resin powder is 5 for f (gypsum).
0 to 1000 F (moisture)/f (resin powder), which is extremely large, is considered a small percentage.

Although the particle size of the powder is not uniformly determined, it is desirable to select it as appropriate from the range of about 20 to 1000 μm in dry state.

Films must have thermoplasticity, tear resistance, appropriate elongation, high tensile strength, and appropriate thickness.Polyethylene film, polypropylene film, soft vinyl film, vinylon film, water-soluble film, It is a film such as a hydrochloric acid rubber film or a polybutylene film, and its thickness cannot be uniformly determined because it varies depending on the shape of the target mold and the place where the film is applied, but it can be selected from among 20 to 200 μm. It is desirable to select and use them.

The water-soluble film applied to the walls that make up the cavity is
In addition to the above film properties, the working temperature is approximately 10-3
The film must be soluble in water within a short time at 5°C. Preferably, polyvinyl alcohol-based and methyl cellulose-based water-soluble films are suitable. The thickness of the film may be appropriately selected from 20 to 200 μm.

The filter prevents powder constituting the mold from scattering into the suction system, and it is desirable that it is resistant to clogging and has low pressure loss.
Use wire mesh with a size of 0 to 250 mm.

Examples of the present invention will be described below.

〔Example〕

FIGS. 1 to 9 are explanatory diagrams specifically showing the operation of an example of an embodiment of the method of the present invention.

First, as shown in FIG. 1, a surface plate 2 having a vent hole is installed on top of a suction box 1, and a model 3 is placed at a predetermined position above it. Next, as shown in FIG. 1, a vacuum suction system consisting of a three-way switching valve 4, a dust filter 5, and a vacuum pump 6 is connected to the suction box 1, and a clamp is placed above the model 3 to sandwich the water-soluble film 7. A frame 8 and an electric heater 9 are installed. In this case, the heater is not limited to an electric heater, but may also be a gas heater or a hot air heater.While heating the water-soluble film 7,
Activate the vacuum pump 6. In order to promote the elongation of the water-soluble film 7, water vapor may be added in combination. When the water-soluble film 7 reaches the appropriate molding temperature, move the clamp frame 8 to the surface plate 2 as shown in FIG. Remove 8.

Next, as shown in FIG. 4, a metal frame 11 having a filter 10 is placed on a surface plate 2, which is entirely fixed to a vibration table 17, so as to surround the model 3.
, a vacuum suction system consisting of a dust filter 16 and a vacuum pump 14 is connected, and after placing the sleeve 15 covered with the film 7 on the model 3, the swelling powder 16 is introduced and the vibrating table 17 is operated. The swellable powder 16 is tightly packed inside the metal frame 11, and the excess powder is removed by cutting.

Thereafter, as shown in FIG. 5, one film 18 is placed between the clamp frames 8 and an electric heater 9 placed above the one metal frame 11. While the film 18 is heated, the vacuum pump 14 is operated. When the film 18 reaches the appropriate molding temperature, the clamp frame 8 is moved to the metal frame 11, and when the film 18 is brought into close contact with the swellable powder 1 (SK) by vacuum suction, and the clamp frame 8 is removed, the water-soluble film 7 is formed.
The metal frame 11 is covered with the film 18 and the film 18 as shown in Fig. 6. Next, as shown in Figure 7, the gold bar 1
Move 1ft upwards and cut out the mold. The upper mold is molded in the metal frame 19 using the same procedure as the lower mold described above, and the heated metal rod is inserted into the sleeve 15 by stacking the upper mold 19 and the lower mold 11 as shown in FIG. Then tear the film and make a hole to complete the cavity.

On the other hand, the slurry 21 is charged into the closed stirrer 20, and while stirring and mixing, the vacuum pump 22 is operated to defoam.

When the defoaming is completed, the vacuum pump 22 is stopped. After connecting the slurry discharge pipe 23 to the sleeve 15, the air compressor 24 is operated to discharge the slurry under pressure and cast it into the cavity 25. After mixing, the air compressor 24 is stopped, the three-way switching valve 26 is switched, atmospheric air is introduced, the pressure is maintained at atmospheric pressure, and the slurry is continued to be pressurized by the differential pressure with the negative pressure inside the mold. The pressure is important for preventing casting defects such as shrinkage and for promoting inkling, but it must not exceed atmospheric pressure to prevent damage to the mold. When the water in the slurry penetrates into the water-soluble films 7 and 18 inside the cavity 25 and dissolves them to form a hole, the air remaining in the cavity 25 escapes to the swellable powder layer, and the slurry completely fills the cavity. The swellable particles that come into contact with water swell and plastically deform, filling and closing the voids, so that the cast body is surrounded by a void-free swellable powder layer via the dissolved water-soluble films 7 and 18. In this way, the particles in the slurry are completely prevented from migrating into the mold, and the water is absorbed into the swellable powder without relying on capillary forces, while being evaporated and removed by the suction of the vacuum pump 6.14. In this way, the cast body dehydrates and hardens to become a molded body, but during this time, even if it shrinks during dehydration, the swollen powder follows and expands, so separation from the mold does not occur, and the cavity wall is always in contact with the infill layer, increasing water absorption. last.

Next, the slurry discharge valve 27 is closed, the slurry discharge pipe is removed, and the metal frames 11 and 19 are placed on the screen 28 shown in FIG. Return to atmospheric pressure. Subsequently, the vacuum pump 6 is stopped and the three-way switching valve 4 is switched to return the lower mold to atmospheric pressure.

Through this operation, the swellable powder in the metal frame 11.19 collapses under its own weight, breaks the water-soluble film 7 and film 18, passes through the screen 2, and falls, resulting in a molded product with the water-soluble film 7 attached to the surface. 29 remains on the screen. The water-soluble film 7 can be easily wiped off. Note that the number of cavities in the mold is not limited to one, but it is also possible to create multiple cavities and increase productivity by molding multiple cavities at the same time.

Next, in the above invention method, α-alumina (particle size 0
．． (1 μm to 2 μm) 6aO weight%, moisture 31.71m%, and carboxymethyl cellulose 0.3% by weight.
Both the film and the water-soluble film used polyvinyl alcohol (thickness: 50 μm). The cavity has a diameter of 20m.

It consists of a shaft with a length of 60 m and a disk with a diameter of 80 gm and a thickness of 15 m mounted 20 m from one end of the shaft. When the negative pressure for holding the mold was set at -400 mHg and the mold was released after 3 hours of dehydration after casting, there was no problem with mold release and a sound molded product could be obtained.

The water-absorbing swelling powder that absorbed water could be regenerated into a dry powder by vacuum drying at 80° C. and 2 TOrr for 3 hours. After repeating water absorption and drying 10 times, the water absorption performance did not change at all.By the way, the water absorption performance of plaster decreases after it is used several times after being molded.

〔Effect of the invention〕

The slurry casting method of the present invention significantly shortens the molding time,
Excellent mold releasability, replacing mold drying with powder drying enables a significant reduction in the required time, and solves the problem of mold life through easy production of molds and repeated use of water-absorbing and swelling powder as mold material. This method can overcome the drawbacks of the plaster method.

[Brief explanation of drawings]

FIGS. 1 to 9 are explanatory diagrams of the operating method in an embodiment of the method of the present invention. In the figure, 1: suction box, 2: surface plate, 6: model,
4, 12.26: Three-way switching valve, 5.13: Dust filter, 6, 14.22: Vacuum bong 7', 7: Water-soluble film, 8: Clamp frame, 9: Heater, 10: Filter, 11, 19 : Metal frame, 15 Ni sleeve, 16: Swellable powder, 17: Vibration table, 18: Film, 20
: Closed type stirrer, 21: Slurry, 23: Slurry discharge pipe, 24
: Air compressor, 25: Cavity, 28 Niscreen,
29: Molded object. In each figure, the same reference numerals indicate the same or corresponding parts. Figure 1 Figure 2 Figure 3 Figure 5 Figure 6 Figure 7

Claims (8)

[Claims] (1) A slurry casting molding method characterized by casting slurry into a mold made of swellable powder, allowing the powder to absorb water in the slurry, and dehydrating and hardening the slurry to form a molded body. (2) A swellable powder is sealed in a closed space in a desired mold shape consisting of a film and a filter, with at least the wall constituting the cavity made of a water-soluble film, and the swelling powder is sucked from the filter part. The slurry casting method according to claim 1, characterized in that the closed space is subjected to negative pressure to maintain the shape and form the mold. (3) The swelling powder is selected from acrylic acid/vinyl alcohol copolymer, sodium acrylate polymer, sodium acrylate/acrylamide copolymer, starch-based graft polymerization of acrylic acid, etc. The method of slurry casting according to claim 1, wherein the slurry is a mixture of one type of water-absorbing swelling powder, a non-water-absorbing swelling powder, and the water-absorbing swelling powder. (4) The slurry casting method according to claim (3), wherein the particle size of the swollen powder is 20 to 1000 μm. (5) A patent claim characterized in that the film is one type of thermoplastic film selected from polyethylene, polypropylene film, soft vinyl chloride film, vinylon film, water-soluble film, hydrochloric acid rubber film, polyethylene film, etc. A method of slurry casting according to item (2). (6) The slurry casting method according to claim (5), wherein the thickness of the film is 20 to 200 μm. (7) Claim (2) characterized in that the water-soluble film applied to the wall constituting the cavity is soluble in water at a working temperature of about 10 to 35°C.
The method of slurry casting described in . (8) The slurry casting method according to claim (7), wherein the water-soluble film is a polyvinyl alcohol-based or methylcellulose-based water-soluble film.