JPH03230844A - Method for forming mold - Google Patents

Abstract

PURPOSE:To prevent generation of gas from inner part in a shell mold at the time of casting by preparing a cope forming cavity corresponding to a drag corresponding part in the shell mold together with the drag and beforehand, forming only the corresponding part in the drag. CONSTITUTION:As a first process, at the time of forming the drag corresponding part 10a in the shell mold 10 by burning resin sand after packing the resin sand into the cavity 12a for lower part formed with the drag 12 and a first cope 14, the drag corresponding part 10a corresponding to inner part of thick part in the shell mold 10 is surely burnt with heat of the cope 14. Successively, as a second process, at the time of forming the whole body of the shell mold 10 by burning the resin sand after packing the resin sand into the remaining part of the drag corresponding part 10a in the shell mold 10 in the cavity 18a for upper part formed with the drag 12 and a second cope 18, the cope corresponding part 10b corresponding to inner part of thick part in the shell mold 10 is burnt with heat of the already burnt drag corresponding part 10a.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for forming molds, particularly shell molds.

(Prior art) As a method for forming shell molds, Utility Model No. 63-1 (J”
As shown in '3236, after resin sand is filled into the cavity of a mold consisting of an upper mold and a lower mold using a blow molding machine, the resin sand in the cavity is heated. A method of forming a shell mold by firing is known.

(Problem to be solved by the invention) However, as shown in FIG.
When molding a shell mold having a thick wall part a, such as a water jacket core for casting a head,
If the mold e is heated for a long time so that not only the surface part C of the thick part a but also the inside part d is fired, the surface part C of the shell mold becomes carbonized and becomes brittle. Therefore, in order to avoid carbonization of the surface portion C of the shell mold, the mold e is usually heated to such an extent that the interior C of the thick wall portion a is not fired and remains unhardened.

However, when casting using a shell mold in which unhardened resin sand remains in the interior d of the thick wall part a, the interior d
Since the gas generated from the unhardened resin sand flows out of the shell mold, there is a problem that casting defects occur in the cast product.

In view of the above, an object of the present invention is to be able to sinter the inside of a thick walled part of a shell mold without carbonizing the surface thereof, thereby preventing gas generation from the shell mold during casting. shall be.

(Means for Solving the Problems) In order to achieve the above object, the present invention forms a cavity corresponding to a lower mold corresponding part of a shell mold with a lower mold in addition to a normal upper mold as an upper mold. An upper mold is prepared, and only the portion of the shell mold corresponding to the lower mold is first molded using the upper mold.

Specifically, the solution taken by the present invention is a mold forming method in which a cavity formed by an upper mold and a lower mold is filled with resin sand by blowing, and then the resin sand is fired to form a shell mold. and a first upper mold that forms a cavity corresponding to the lower mold of the shell mold with the lower mold, and a cavity that corresponds to the entire shell mold with the lower mold. A second upper mold to be formed is prepared, and as a first step, after setting the first upper mold in the lower mold, blowing resin sand into the cavity formed by the lower mold and the first upper mold. and then fill with
The resin sand is fired to form a portion corresponding to the lower mold of the shell mold, and then, as a second step, the first upper mold is removed from the lower mold, and then the second upper mold is set on the lower mold. Then, resin sand is filled in the remaining part of the shell mold corresponding to the lower mold in the cavity formed by the lower mold and the second upper mold by blowing, and then the resin sand is fired to form the entire shell mold. It is configured to mold.

(Function) With the above configuration, in the first step, resin sand is filled into the cavity formed by the lower mold and the first upper mold, and then the resin sand is fired to form the lower mold corresponding part of the shell mold. When molding is performed, the portion corresponding to the lower mold corresponding to the inside of the thick walled portion of the shell mold is reliably fired by the heat of the first upper mold.

Next, as a second step, resin sand is filled in the remaining part of the shell mold corresponding to the lower mold in the cavity formed by the lower mold and the second upper mold, and then the resin sand is fired to form the shell mold. When the entire shell mold is molded, the part corresponding to the upper mold corresponding to the inside of the thick part of the shell mold is fired by the heat of the corresponding part of the lower mold which has already been fired.

(Example) Hereinafter, an example of the present invention will be described based on the drawings. Although the application of the shell mold to which the present invention is directed is not limited, in this example, a case will be described in which a shell mold 10 made of a water jacket core for casting a cylinder head of an engine is molded. .

First, as a preparatory step for the first step, as shown in FIGS. 1 and 2, a lower mold 12, a first upper mold 14 combined with the lower mold 12, a lower mold 12 and a first upper mold 14, An insert 16 is prepared which can freely move forward and backward from the side.

The lower mold 12 includes a lower cavity 12a having a shape corresponding to the lower part of the shell mold 10, and a through hole that vertically passes through the lower part of the lower mold 12 and is open at the bottom of the lower cavity 12a. A hole 12b, an eject pin 12c that is movably disposed in the through hole 12b and that upwardly ejects the shell mold 10 after molding, and a lower mold temperature regulator 12d that adjusts the temperature of the lower mold 12. We are prepared.

Further, the first upper mold 14 is connected to the lower cavity 1 of the lower mold 12.
a blow hole 14a for supplying resin sand into 2a;
A lower cavity 1 is formed below the blow hole 14a.
Blow mouth cavity 14b constituting the blow mouth 2a
and a first upper mold temperature regulator 14c that adjusts the temperature of the first upper mold 14.

Next, as a first step, the first upper mold 14 is set on the lower mold 12, and the insert 16 is inserted between the lower mold 12 and the first upper mold 14.
are set to form the lower cavity 12a and the blow mouth cavity 14b, and then resin sand is blown with a blow molding machine (not shown) to form the lower cavity 12a and the blow hole from the blow hole 14a of the first upper mold 14. The mouth cavity 14b is filled. Thereafter, the lower mold 12 and the first upper mold 14 are heated by the lower mold temperature regulator 12d and the first upper mold temperature regulator 14c to form the lower mold cavity 1.
2a and the resin sand in the blow mouth cavity 14b are fired to form the lower mold corresponding portion 10a of the shell mold 10.

In this way, the lower corresponding portion 10 of the shell mold 10
The upper part a, that is, the inside of the thick part of the shell mold 10 is heated by the first upper mold 14 and fired reliably.

Next, as a preparation step for the second step, a second upper mold 18 as shown in FIGS. 3 and 4 is prepared. That is, the second upper mold 18 has a structure that is assembled on the lower mold 12, and includes an upper cavity 18a that forms a cavity with a shape corresponding to the entire shell mold 10 with the lower mold 12, and It is provided with a blow hole 18b for supplying resin sand to the cavity 18a, and a second upper mold temperature regulator 18c for adjusting the temperature of the second upper mold 18.

Next, as a second step, the first upper mold 14 is separated from the lower mold 12, while the lower mold corresponding portion 10a of the shell mold 10 and the insert 16 are left in the lower mold 12, as shown in FIG. The lower mold 12 is moved from below the first upper mold 14 to below the second upper mold 18, and the lower mold 12 and the second upper mold 18 are set. In this case, as shown on the right side of FIG. 1, in the first step, resin sand is filled into the blow hole cavity 4b of the first upper mold 14, but not filled into the blow hole 14a. The blowing 10C of the shell mold 10 can be used to set the height when setting the second upper mold 18, and as shown in FIG. Mouth cavity 14b
When the blow hole 14a is filled, the shell mold 10
The blow hole portion 10d can be used for positioning when setting the second upper mold 18.

Thereafter, the resin sand is blown with a blow molding machine (not shown), and the resin sand is passed through the blow hole 18b of the second mold 18 into the cavity formed by the lower mold 12 and the second upper mold 18. Lower mold corresponding part 10a of shell mold
After filling the remainder of the shell mold 10, the lower mold 12 and the second upper mold are heated by the lower mold temperature regulator 12d and the second upper mold temperature regulator 18c to form the entire shell mold 10. in this case,
The lower mold corresponding portion 10a of the shell mold 10 heated in the first and second steps and the upper mold corresponding portion 10b of the shell mold 10 heated only in the second step are fired to about the same temperature. , first upper mold temperature regulator 14c
It is also preferable that the temperature of the second upper mold temperature regulator 18c is set higher than the temperature of the lower mold temperature regulator 12d.

When the entire shell mold 10 is fired as described above,
The lower center of the upper mold corresponding part 10b of the shell mold 10, that is, the inside of the thick part of the shell mold 10, is the lower corresponding part 10.
It is fired because it is heated by the heat from the upper part of a.

Next, as a final step, after removing the insert 16 from the lower mold 12 and the second upper mold 18 and removing the second upper mold 18 from the lower mold 12, the eject pin 12c is raised to remove the shell mold 10. The mold is released from the lower mold 12.

(Effects of the Invention) As explained above, according to the mold forming method according to the present invention, as a first step, the resin sand in the cavity formed by the lower mold and the first upper mold is fired to form a shell mold. After molding the portion corresponding to the lower mold, as a second step, the resin sand remaining in the portion corresponding to the lower mold in the cavity formed by the lower mold and the second upper mold is fired to form the entire shell mold. For molding, the inside of the shell mold is fired by the heat of the first upper mold in the first step and the heat of the lower mold corresponding portion of the shell mold in the second step.

Therefore, according to the present invention, the inside of the thick wall part of the shell mold can be fired without carbonizing the surface part, so gas generation from inside the shell mold can be reliably prevented during casting. .

[Brief explanation of drawings]

1 to 5 show a molding method according to an embodiment of the present invention, FIG. 1 is a cross-sectional view showing the first step, FIG. 2 is a cross-sectional view taken along the line ■ to ■ in FIG. 1, Figure 3 is a sectional view showing the second step, Figure 4 is a sectional view taken along the line ■ to ■ in Figure 3, and Figure 5 is a sectional view showing the second step.
The figure is a schematic diagram showing the process of moving the lower mold from the first upper mold to the second upper mold, and FIG. 6 is a sectional view showing a conventional molding method. 1 10...Shell mold 10a...Lower mold corresponding part 10b...Upper mold corresponding part 12...Lower mold 12a...Lower cavity 14...First upper mold 18...Second Upper mold 18a...upper cavity 2 Fig. 2

Claims (1)

[Claims] (1) A mold forming method in which a cavity formed by an upper mold and a lower mold is filled with resin sand by blowing, and then the resin sand is fired to form a shell mold, the upper mold comprising: Prepare a first upper mold that forms a cavity corresponding to the lower mold of the shell mold with the lower mold, and a second upper mold that forms a cavity corresponding to the entire shell mold with the lower mold. As a first step, after setting the first upper mold in the lower mold, the cavity formed by the lower mold and the first upper mold is filled with resin sand, and then the resin sand is is fired to form a corresponding part of the lower mold of the shell mold. Next, as a second step, after removing the first upper mold from the lower mold, the second upper mold is set in the lower mold, and the second upper mold is set in the lower mold. Resin sand is filled in the remaining portion of the shell mold corresponding to the lower mold in the cavity formed by the lower mold and the second upper mold by blowing, and then the resin sand is fired to form the entire shell mold. A mold forming method characterized by the following.