JPH07214236A - Production of casting mold - Google Patents

Abstract

PURPOSE:To provide a process for producing a casting mold capable of casting even a product which is internally formed with a cavity, is opened at least at one end and is formed with the cavity communicating with outside by a precision casting method ( lost wax method) which are cost effectively advanta geous. CONSTITUTION:Wax molded goods 10 having the same shape as the shape of the product are molded. A slurry is then adhered around these molded goods, by which a coating layer 11 is formed around the wax molded goods 10. The wax molded goods are removed from this coating layer 11 and the coating layer 11 is calcined, by which the casting mold is obtd. The coating layer is also formed on the inside surface of the cavity of the wax molded goods 10 at the time of forming the coating layer 11 and further, solid 13 which is burned away at the time of a calcination stage is packed into the cavity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manufacturing method for manufacturing a mold for a product, such as a tool holder, in which a void is formed and at least one end is opened so that the void is communicated.

[0002]

2. Description of the Related Art Conventionally, for example, as shown in FIG. 1, when a hollow bit holder 2 having a through hole inside is manufactured by a precision casting method (lost wax method), first, the same shape as the product is obtained. The wax molded product of 1. is molded by injection molding, and then these wax molded products are assembled together in a tree shape, and the refractory particles are sprayed around the assembly with the ceramic slurry applied. By repeating this, a large number of coating layers are formed around the assembly, dried, and the wax molding (assembly) is melted and removed from the coating layer to form a mold. The molten metal is injected into the space of the above, and finally, the coating layer is removed, and the product is taken out.

[0003]

In the conventional casting method of the bit holder 2 and the like using the lost wax method, in the coating layer forming step, the coating layer is formed in the entire space in the through hole of the wax molded product. Since it is filled in, it is very difficult to remove the coating layer (mold) from the through hole 1 of the metal product 2 which is replaced with the wax molded product in the subsequent mold separating step. Is difficult.

For this reason, when casting the bit holder 2 or a pipe-shaped member elongated from the bit holder 2 (having a length-to-diameter ratio of 5 or more), a ceramics core is placed in advance in the internal space. In this state, a coating layer is formed around the wax molded product, the wax molded product is removed from the coating layer to form a mold, and then molten metal is injected into the space inside the mold to make a product. The reality is that

However, in the method using the above-mentioned ceramic core, the cost increases because the ceramic core itself is expensive. In addition, when the ceramic core is removed from the product after casting the product by pouring the molten metal, it is removed by physical means such as sandblasting or chemical means such as chemicals. There was a problem such as poor productivity and reduced production efficiency.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a product in which a void is formed inside and at least one end is opened so that the void communicates with the outside. Another object of the present invention is to provide a method for producing a mold that can be cast by an economically advantageous precision casting method (lost wax method).

[0007]

To achieve the above object, the present invention provides a wax having the same shape as a product in which a void is formed inside and at least one end is opened so that the void communicates with the outside. A molded article is molded, and then a slurry is applied around the wax molded article to form a coating layer around the wax molded article. Further, the wax molded article is removed from the coating layer, and the coating layer is removed. In the method for producing a mold by firing, when forming the coating layer, a coating layer is also formed on the inner surface of the void of the wax molded product, and is further burned to the void during the firing step. It is for packing solids. Dry sand may be filled in the gap between the coating layer on the inner surface of the void of the wax molded product and the solid material. Further, the voids may be filled with solid particles that are burned out during the firing step instead of solid matter.

[0008]

In the method for producing a mold of the present invention, in the dewaxing step of removing the wax molded product from the coating layer, the solid material packed in the above-mentioned space supports the coating layer from the back side, so that the wax expansion The pressure does not damage the coating layer. Further, in the subsequent coating layer baking step, the solid matter is burned out, so that the mold (coating layer) can be easily removed by utilizing the void in the subsequent mold separating step.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. First, a wax molded product 10 having the same shape as the bit holder 2 having a void (through hole) 12 formed therein and having both ends opened as shown in FIG. 1 is molded, and then these wax molded products 10 are put together. Assemble in a tree shape,
A plurality of coating layers 11 are formed around the wax molded article 10 by spraying refractory particles in a state where the ceramic slurry is applied around this assembly and repeating this. At this time, the coating layer 11 is also formed on the inner surface of the void 12.

Next, after the solid material 13 is packed in the void 12 inside the wax molded article 10 covered with the coating layer 11, the coating layer 1 is further provided.
1 and the solid material 13 are coated with the ceramic slurry and sprayed with refractory particles to form a coating layer 14
To form and dry. At this time, there is a gap S between the coating layer 11 and the solid material 13, and this gap S
Is completely filled by the infiltration of ceramic slurry or the like when forming the coating layer 14. Further, as the solid material 13, a material which is burnt off in a subsequent firing step, for example, wood or foam styrene is used.

Next, the wax molded product 10 (assembly) is melted and removed from the inside of the coating layers 11 and 14, and then the coating layers 11 and 14 are fired at a predetermined temperature to form a mold, and then the inside of the mold is formed. The molten metal is injected into the space, and finally, the coating layers 11 and 14 are removed and the product 2 is taken out.

In the above manufacturing process, during the dewaxing process of removing the wax molded product 10 from the coating layers 11 and 14, the solid material 13 packed in the voids 12 supports the coating layer 11 from the back side, so that when the wax expands. It prevents the coating layer 11 from being damaged by the pressure.

Further, the subsequent coating layers 11 and 14
In the firing step, since the solid matter 13 is burned off and the void 12 is formed again, after the casting, the coating layer 11,
When the coating layer 14 is removed during the mold separation process in which the product 14 is removed and the product 2 is taken out, the void 12 is exposed, and the void 12 can be used to easily form the coating layer 11 on the inner surface of the void. It can be removed from product 2. Therefore, when the coating layer 11 is removed from the product 2, a defect such as a scratch on the product 2 does not occur.

In the above embodiment, the wax molded product 1 is used.
The solid space 13 such as wood and foam polystyrene is packed in the inner space 12 of 0, but not limited to this.
Dry sand may be filled in the gap S formed between the coating layer 11 on the inner surface of the wax molded product 10 and the solid material 13. By using dry sand like this,
This is advantageous when performing the subsequent drying process.

Further, as shown in FIG. 2, instead of the solid matter 13, combustible solid particles 15 made of magnesium, carbon, wood powder, or the like that are burnt out during the above-mentioned firing step may be packed in the void 12.

Further, in the above embodiment, the bit holder was described as an example of the object to be cast, but as shown in FIG. 3, the bit holder of an automobile having only one opening on one side and five openings on the other side. The present invention can be applied to even a complicated thing such as a manifold. That is, the manifold shown in this figure has a lateral member 22 in which the sprue part 21 is formed.
In addition, a plurality of molded product connecting parts 23 are arranged side by side at equal intervals, and the support parts 24 are provided on the pair of outer molded product connecting parts 23.
While the sprue portion 21, the lateral member 22, the molded product connecting portion 23, and the support portion 24 are integrally molded with wax, while the metal attachment 25 is projected from the end portion of the sprue portion 1. In addition, each molded product connecting portion 23
The round bar 26 made of metal is connected to the tip of the. Needless to say, the present invention can be applied even if the casting object is a simple pipe.

Further, in the above-mentioned embodiment, the ceramic slurries and the refractory particles are alternately stacked to form the coating layers 11 and 14, but when a thin coating layer is sufficient, the ceramics are used. You may form these coating layers 11 and 14 only with a rally.

[0018]

According to the invention of claim 1, during the dewaxing step of removing the wax molding from the coating layer,
Since the solid substance packed in the void supports the coating layer from the back side, it is possible to prevent damage to the coating layer due to the pressure when the wax expands, and the solid substance is burned off in the subsequent coating layer firing step. Therefore, the mold (coating layer) can be easily removed by utilizing the void of the product after casting. As a result, it becomes possible to cast a product in which a void is formed inside and at least one end of which is opened and the void is communicated with the outside by a precision casting method (lost wax method) that can be implemented at low cost.

According to the second aspect of the present invention, the gap between the coating layer on the inner surface of the cavity of the wax molded product and the solid is pre-filled with dry sand, so that the shape of the cavity is in the gap with the solid. Even when the slurry does not easily invade, the void portion can be densely filled with a solid substance and the like, and the pressure at the time of wax expansion can be sufficiently endured during the dewaxing process.

According to the third aspect of the present invention, the voids are filled with solid particles which are burned out during the firing step instead of the solid matter. The advantage is that solid particles can be packed tightly.

[Brief description of drawings]

FIG. 1 is a sectional view illustrating an embodiment of the present invention.

FIG. 2 is a sectional view illustrating another embodiment of the present invention.

FIG. 3 is a sectional view illustrating still another embodiment of the present invention.

[Explanation of symbols]

 2 Bit holder (product) 10 Wax molded product 11 ・ 14 Coating layer 12 Void (through hole) 13 Solid matter 15 Solid particle

Claims (3)

[Claims] 1. A wax molded product having the same shape as a product having a void formed inside and having at least one end opened so that the void communicates with the outside, and then a slurry is formed around the wax molded product. To form a coating layer around the wax molded product, further remove the wax molded product from the coating layer, and calcine the coating layer to obtain a mold, wherein the coating layer is When forming, a coating layer is formed also on the inner surface of the cavity of the above wax molded article, and the cavity is filled with a solid material that is burned off during the firing step. 2. The method of manufacturing a mold according to claim 1, wherein a dry sand is filled in a gap between the coating material on the inner surface of the cavity of the wax molded product and the solid material. . 3. The method for producing a mold according to claim 1, wherein the voids are filled with solid particles that are burned out during the firing step instead of the solid matter.