JPH057981A - Method for molding mold for hollow product - Google Patents

Abstract

(57) [Abstract] [Purpose] To enable the use of a mold using a vanishing model in casting a product having a hollow portion. [Configuration] A virtual plane is set which passes through the hollow part of the product and crosses the product, and the first disappearance model 10 corresponding to the shape of the product on one side of the virtual plane and the same product on the other side of the virtual plane as above. A second step of forming a second vanishing model 11 corresponding to the shape of the above; and a vanishing model having a recess 19 corresponding to the hollow portion of the vanishing models 10 and 11 with an opening 20 of the recess 19 downward. A second step in which the vanishing model is installed in the metal frame 18, and the first casting sand 21 is filled in the metallic frame 18 to cover the outer surface side of the vanishing model with the first casting sand 21; The opening 20 of the concave portion 19 in the vanishing model is directed upward, and the second portion is formed through the opening 20 into the concave portion 19.
A third step of filling the foundry sand 24; a fourth step of joining the surfaces of both vanishing models 10 and 11 corresponding to the virtual surface to each other
And the process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of molding a mold for hollow products, and more particularly to a method of molding using a vanishing model.

[0002]

2. Description of the Related Art A casting method using a vanishing model made of foamed plastic, a so-called full molding method, has been widely used from the past because of facilitating casting. According to this casting method, the vanishing model is molded with, for example, foam polystyrene, and this is embedded in molding sand to mold a mold. Next, a molten metal is cast into the embedded disappearance model. Then, the disappearance model in contact with the molten metal immediately burns and gasifies due to oxygen in the air existing between the sand particles of the foundry sand, or gasifies by thermal decomposition, and in lieu of this, the molten metal fills the mold. Then, casting is performed by this.

[0003]

By the way, when a cast product has a hollow portion, it is required to also embed molding sand (core) having a shape corresponding to the hollow portion inside the vanishing model. To be done. However, since it is difficult to form a mold by combining such a disappearance model and foundry sand, conventionally, when casting a product having a hollow portion, a mold using the disappearance model as described above is not used. In reality, it is the fact that the molding is done only with foundry sand.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to make it possible to easily use a mold using a disappearing model in casting a product having a hollow portion. And

[0005]

A feature of the present invention for achieving the above object is a method of molding a mold for a product having a hollow portion, which crosses the product through the hollow portion. A virtual plane is set, and a first vanishing model corresponding to the shape of the product on one side of the virtual plane and a second vanishing model corresponding to the shape of the product on the other side of the virtual plane are formed. 1 step; a dissipative model having a recess corresponding to the hollow portion of both dissipative models is set in the metal frame so that the opening of the recess faces downward, 1. A second step of filling the molding sand with the first molding sand to cover the outer surface side of the vanishing model; integrating the vanishing model and the metal frame so that the opening of the recess in the vanishing model faces upward Second casting through the opening and into the recess. Lies in that constituted by a fourth step of bonding together the surfaces of both evaporative pattern corresponding to the virtual surface; a third step and filling the.

[0006]

[Operation] The operation of the above configuration is as follows. When molding the mold 8 of the product 1 having the hollow portion 6, first, the virtual surface 9 that crosses the product 1 through the hollow portion 6 is formed.
To set. Then, a first disappearance model 10 corresponding to the shape of the product 1 on one side of the virtual surface 9 and a second disappearance model 11 corresponding to the shape of the product 1 on the other side of the same virtual surface 9 are formed. .. Next, the outer surfaces of the first vanishing model 10 and the second vanishing model 11 are first placed inside the first metal frame (metal frame) 18 and the second metal frame 25.
It is embedded with the foundry sand 21 and the third foundry sand 26.

Next, in the first vanishing model 10 and the second vanishing model 11, the second molding sand 24 is filled in the concave portion 19 corresponding to the hollow portion 6. Then, the surfaces of the first vanishing model 10 and the second vanishing model 11 corresponding to the virtual plane 9 are joined to each other. Then, the second casting sand 24 is embedded between the first vanishing model 10 and the second vanishing model 11, and the mold 8 is obtained.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 2, reference numeral 1 is a cast product, which is, for example, a cylinder head of an engine. The product 1 is integrally formed by an upper plate 2, a lower plate 3, a side wall 4, and a protrusion 5, and a hollow portion 6 serving as a cooling water passage is formed inside the product 1. In FIG. 1, 8 is a mold, and this mold 8 is used for casting the product 1.

The method of molding the mold 8 will be described below. As a first step, first, as shown in FIG. 2, an imaginary plane 9 that crosses the product 1 substantially horizontally through the hollow portion 6 is set. The virtual surface 9 extends substantially along the lower surface of the upper plate 2.

Next, as shown in FIG. 3, a first side corresponding to the shape of the product 1 which is one side of the virtual surface 9 and which is above the virtual surface 9 is formed.
The vanishing model 10 and the second vanishing model 11 corresponding to the shape of the product 1 above, which is the other side of the virtual surface 9 above, are formed. In this case, the protrusion 12 is formed on the lower surface of the outer edge portion of the first vanishing model 10 in plan view, while the groove 13 is formed on the upper surface of the outer edge portion of the second vanishing model 11 in plan view. ing. Then, when the first strip model 10 and the second strip model 11 are joined by fitting the ridge body 12 and the concave groove 13 to each other, the first strip model 10 and the second strip model 11 are separated from each other. It is positioned accurately.

Each of the disappearance models 10 and 11 is formed by foaming pre-expanded beads (about 50 times) filled with N ₂ gas in a mold, or cutting out a block formed by the beads. It is formed by processing. Further, a coating material is applied to each of the disappeared models 10 and 11 by the dipping method or the bukkake method.

As a second step, as shown in FIG.
The first metal frame 18 is installed on the surface plate 17. The hollow portion 6 of the first vanishing model 10 and the second vanishing model 11 is
The second vanishing model 11 having the concave portion 19 corresponding to the first vanishing model 11 is placed in the first metal frame 18 so that the opening 20 of the concave portion 19 faces downward.
Install on top. Then, the first molding sand 21 is filled in the first metal frame 18, and the outer surface side of the second vanishing model 11 is covered with the first casting sand 21. 4-5 wt% of water glass (JIS No. 1, adjusted to a specific gravity of 1.35), which is a binder, is added to the first foundry sand 21 in advance and sufficiently kneaded.

Then, the first metal frame 18 is attached to the first surface plate 17
Place it in a closed chamber with it and quickly bring it to about 150 torr
Depressurize to. After this, there is a hardening gas in the closed chamber
CO ₂ Introduce gas. Then, this gas is mixed with the water
Reacts with the soot to harden the first foundry sand 21.
The desired strength is secured in 21. And the above CO₂ Moth
By introducing gas, the inside of the closed chamber is returned to atmospheric pressure, and the first gold
The frame 18 is taken out from the closed chamber together with the first surface plate 17.
In this case, CO is not present in the first foundry sand 21.₂ Filled with gas
Since it is atmospheric pressure, take it out of the closed chamber.
However, air in the atmosphere does not enter the inside.

As a third step, as shown in FIG.
The postures of the second vanishing model 11 and the first metal frame 18 are integrally determined so that the opening 20 of the recess 19 of the vanishing model 11 faces upward. More specifically, the second platen 23 shown in FIG. 5 is placed on the first metal frame 18 shown in FIG. 4, and the second vanishing model 11, the first platen 17, and the second platen 23 are placed. Upside down integrally. Then, by the above-mentioned inversion, the first surface plate 17 positioned on the first metal frame 18 is separated from the first metal frame 18 above. As a result, the second casting sand 24 is filled in the recess 19 through the opening 20 that is opened upward. The second foundry sand 24 corresponds to the core of the mold 8. In this case, the second casting sand 24, the collapse of the molding sand is a good organic binders, CO ₂
Ecorotech 2000 (Foseco
The trademark of Japan Limited) is adopted.

As a fourth step, as shown in FIG. 6, the first vanishing model 10 is placed on the second vanishing model 11, and each of the first vanishing model 10 and the second vanishing model 11 corresponding to the virtual plane 9 is placed. The surfaces are joined to each other while the projection 12 and the groove 13 are fitted to each other. Further, the second metal frame 25 is installed on the first metal frame 18, and the third molding sand 26 is filled in the second metal frame 25. In this case, a plurality of through holes 27 are formed in advance in the first disappearance model 10, and the second casting sand 24 is filled in the through holes 27 in advance. Furthermore,
A gate 29, which is a heat-resistant pottery tube, is installed in the third molding sand 26.

The third foundry sand 26 contains the first foundry sand 2
Water glass is added as in 1. Then, the first metal frame 18 and the second metal frame 25 are put together with the second surface plate 23 into the closed chamber, the pressure is reduced in the same manner as described above, and CO ₂ gas is introduced. The second molding sand 24 and the third molding sand 26 are hardened. Then, after returning to the atmosphere in the same manner as described above, the first metal frame 18 and the second metal frame 25 are taken out from the closed chamber together with the second surface plate 23. By the above, the mold 8 is molded.

Casting by the mold 8 is performed as follows. In FIG. 1, first, in the mold 8, the first
The metal frame 18 and the second metal frame 25 are disassembled and removed. in this case,
The first foundry sand 21 and the third foundry sand 26 are sufficiently hardened and retained in their shapes. On the other hand, the bottom of the third metal frame 33 is filled with sand 34, and the first foundry sand 21 and the third foundry sand 26 described above are installed on the sand 34. Next, the same as above
The space inside the metal frame 33 is further filled with sand 34. At this time, another sprue 35 of the same quality as the sprue 29 is set on the sprue 29, and the weir bowl 36 is placed on the upper surface of the sand 34 on the sprue 35.

At the time of casting, the suction pump 37 is operated to make the inside of the third metal frame 33 a negative pressure, and the suction pump 3
Continue the operation of 7. In this case, since the first metal frame 18 and the second metal frame 25 have already been removed, the pressure inside the first molding sand 21 and the third molding sand 26 is easily reduced. And
In this state, the molten metal 38 is cast into the first vanishing model 10 and the second vanishing model 11 through the dam 36, the other gate 35, and the gate 29. At this time, the first disappearance model 10 and the second disappearance model 10
Disappearance model 11 and the first foundry sands 21 and 2 around it
Since almost no air is present in the foundry sand 24, the third foundry sand 26, and the sand 34, the first vanishing model 10 and the second vanishing model 11 do not burn during the casting and are pyrolyzed (gasified) into monomers. Then, in lieu of this, the molten metal 38 fills the mold 8. After that, the molten metal 38 is cooled and solidified, and the second foundry sand 24 is discharged through the through holes 27, whereby the product 1 is obtained. In this case, since the second foundry sand 24 is made of the above-described material, it is easy to remove the sand, and thus the second foundry sand 24 can be easily discharged.

On the other hand, the gas 34 generated by the thermal decomposition is immediately discharged to the outside of the third metal frame 33 by the suction pump 37. Therefore, when the molten metal 38 is cast,
Since the generation of unburned substances is prevented and the gas 39 is smoothly discharged, the casting mold 8 makes it possible to obtain a product 1 with beautiful skin. Further, the virtual surface 9 may pass through the product 1 by passing through the upper and lower intermediate portions of the hollow portion 6. In this case, the first disappearance model 10 also has the hollow portion 6
Therefore, the first vanishing model 10 may be processed in the same manner as the second and third steps of the second vanishing model 11. In addition, the ridge 12
The virtual surface 9 may be flat without providing the concave groove 13.

[0020]

According to the present invention, there is provided a method of molding a mold for a product having a hollow portion, wherein a virtual plane is set across the product through the hollow portion, and a virtual plane is formed on one side of the virtual plane. A first step of forming a first vanishing model corresponding to the shape of the product and a second vanishing model corresponding to the shape of the same product on the other side of the same virtual surface as above; in the hollow portion of the two vanishing models A vanishing model having a corresponding recess is installed in the metal frame so that the opening of the recess faces downward, and the first casting sand is filled with the first casting sand in the same as above. A second step of covering the outer surface side of the vanishing model; the postures of the vanishing model and the metal frame are integrally determined so that the opening of the recess in the vanishing model faces upward, and then the inside of the recess is passed through the opening. Third step of filling the second foundry sand; both disappearance corresponding to the above virtual surface Since the fourth step of joining the respective surfaces of the mold to each other is performed, in short, a virtual plane that crosses the product through the hollow portion is set, and the first disappearance corresponding to the shape of the product on one side of the virtual plane is set. A model and a second vanishing model corresponding to the shape of the product on the other side of the virtual surface are formed, and casting sand is formed in the recesses corresponding to the hollow portions in the first vanishing model and the second vanishing model. By filling, a mold for a product having a hollow portion can be molded. As described above, since no complicated special work is required for this molding, it is possible to easily use the mold using the vanishing model in the casting of the product.

[Brief description of drawings]

FIG. 1 is a side sectional view at the time of casting.

FIG. 2 is a side sectional view of a product showing a first step.

FIG. 3 is a side sectional view of a first vanishing model and a second vanishing model showing a first step.

FIG. 4 is a side sectional view showing a second step.

FIG. 5 is a side sectional view showing a third step.

FIG. 6 is a side sectional view showing a fourth step.

[Explanation of symbols]

 1 Product 6 Hollow Part 8 Mold 9 Virtual Surface 10 First Disappearance Model 11 Second Disappearance Model 12 Protruding Body 13 Recessed Groove 18 First Metal Frame (Gold Frame) 19 Recess 20 Open 21 First Cast Sand 24 Second Cast Sand 25 2nd metal frame 26 3rd casting sand

Claims (1)

Claim: What is claimed is: 1. A method of molding a mold for a product having a hollow portion, wherein a virtual plane is set across the product through the hollow portion,
The first step of forming a first disappearance model corresponding to the shape of the product on one side of the virtual surface and a second disappearance model corresponding to the shape of the same product on the other side of the same virtual surface; Of the vanishing model, the vanishing model having a concave portion corresponding to the hollow portion is set in the metal frame so that the opening of the concave portion faces downward, and the same as above is filled with the first molding sand. A second step of covering the outer surface side of the vanishing model with the first casting sand of the lever; the postures of the vanishing model and the metal frame are integrally determined so that the opening of the recess in the vanishing model faces upward, and then, ,
Molding method for a hollow product mold, comprising a third step of filling the second molding sand into the recess through the opening; and a fourth step of joining the surfaces of both vanishing models corresponding to the virtual surface to each other. ..