JPH11239843A - Core for casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cast even a casting whose dimension is large and whose shape is complicated with excellent dimensional accuracy by a simple work by assembly a plurality of split cores having a split surface at the positions between a plurality of cavities to constitute a core. SOLUTION: A core 10 is constituted by assembling split cores which are split into the number of blades of an impeller, i.e., three in a disk shape. The central angle of each split core is of approximately fan-shape of 120 deg., and a cavity 14 along the shape of a blade is provided inside having openings in upper and lower surfaces. A hollow body of uniform thickness comprises an upper plate 16, a lower plate 18, an inner end plate 20 and the cavity 14. The split cores are assembled to a disk shape by setting end faces 12a, 12a to an upper surface of a lower die of the preliminarily specified shape to form the core 10, and a mold having the cavity along the shape of the impeller is formed by covering an upper die thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting core suitable for casting a casting having a complicated shape such as an impeller of a centrifugal rotary machine.

[0002]

2. Description of the Related Art In the case of casting an impeller 104 of a large centrifugal rotary machine having a plurality of (three in the figure) blades 102 inside a shroud 100 as shown in FIG. As shown, the upper mold 118, the lower mold 114, and the core 1
10 is prepared, and the core 1 is placed between the upper mold 118 and the lower mold 114.
10 is arranged to form a mold 122 having a cavity 116 inside the product shape (shape of the impeller 104).

[0003] That is, the core 110 is divided into the same number of divided cores 112 as the number of the wings 102, and concave portions having a predetermined shape are formed on end faces 112 a and 112 a of these divided cores 112. deep. Then, the divided cores 112 are combined in a disk shape to form the wing 10 between the adjacent end faces 112a, 112a.
The core 110 is configured to form the cavity 116 according to the shape of No. 2.

[0004]

However, if the cavity is formed between the end faces of the split core as described above, the misalignment at the time of assembling the split core directly affects the thickness and shape of the blade. . Therefore, it is difficult to cast an impeller having a particularly large size with high dimensional accuracy. In addition, a high accuracy is required for the alignment of the divided cores, and a large amount of labor is required for an assembling operation. There was a problem.

The present invention has been made in view of the above problems, and provides a casting core capable of casting with high dimensional accuracy by a simple operation even in a casting having a large size and a complicated shape. With the goal.

[0006]

According to a first aspect of the present invention, in a casting core including a plurality of cavities for casting a product portion therein, a dividing surface is formed at a position between the plurality of cavities. A casting core characterized by being constructed by assembling a plurality of divided cores.

[0007] Thus, since the cavity itself for casting the product portion is not divided, its shape and dimensions are not affected by assembly, and a highly accurate product can be cast. In addition, the precision required for the assembling work of the mold is reduced, so that the work is facilitated. The split cores are usually of the same shape and are each formed to include a cavity. The division surface can be formed in a simple shape such as a flat surface, but a projection for positioning or the like may be provided.

The casting object is, for example, an impeller of a centrifugal rotary machine, and the core is used to form a portion including wings between the side plates or the main plate. In this case, the split core is configured to include one or more cavities forming the wing.

According to a second aspect of the present invention, the split core is formed by a rapid forming method.
The core for casting according to the above. This makes it possible to easily and accurately produce a core having a cavity having a complicated shape inside. Examples of the rapid forming method include a selective laser sintering method, a droplet jetting method, a melt deposition method, an optical molding method, a thin plate laminating method, and a solid base curing method. Since the individual split cores are smaller than the cores formed integrally, the apparatus for performing the rapid forming process need not be large.

According to a third aspect of the present invention, there is provided the casting core according to the second aspect, wherein the split core is formed hollow. Thus, the weight of the split core can be reduced, and the casting can be cooled uniformly, thereby preventing the occurrence of defects in the casting due to hot spots.

According to a fourth aspect of the present invention, the outer mold for accommodating the core is formed by directly processing a sand mold block by an automatic control processing machine. It is a core. Thus, the outer mold can be manufactured with a high degree of shape reproducibility without going through the transfer step using the original mold.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. Here, an impeller 1 having three blades 102 as shown in FIG.
The core used for casting the core 04 will be described.

The core 10 of this embodiment includes an impeller 10
Four blades 102, that is, three divided cores 12 divided into three, and these divided cores 12 are combined in a disk shape. Each of these split cores 12 is formed in a substantially fan shape with a central angle of 120 °, and a wing 102
Are provided in the upper and lower surfaces with openings.

The split core 12 includes an upper plate 16 and a lower plate 1.
8, the inner end plate 20 and the wall plate 22 which defines the cavity 14 form a hollow body having a uniform thickness. As a result, the weight of the mold is reduced, and the casting is cooled evenly, thereby preventing the occurrence of defects in the casting due to hot spots. Although the end faces 12a, 12a of the split core 12 are flat surfaces perpendicular to the XY plane in this embodiment, they may have an appropriate inclination or irregularities according to the shape of the cavity and the like. Also, irregularities may be formed for alignment between the end faces.

The split core 12 is placed on the upper surface of a lower die 30 having a predetermined shape in advance, and the end surfaces 12a, 12a
Are combined into a disk shape to form the core 10, and the upper die 32 is put on the core 10, thereby forming the mold 36 having the cavity 34 conforming to the shape of the impeller 104.
At this time, the end face 12a is constituted by a flat face extending in the vertical direction by the end plate 20, so that the split core 12
Can be easily positioned. Then, a molten metal is poured into the cavity 34, solidified to cast a casting, and the mold is broken to take out the cast impeller. Since the core is hollow, destruction is easy.

In this embodiment, the split core 10 is manufactured by an optical shaping method using a selective laser sintering apparatus, which is one of the rapid forming methods. That is, as shown in FIG. 3, in the chamber 42 of the selective laser sintering apparatus 40, for example, with a thickness h of 0.1 mm, for example, an average particle diameter of 30 to
One layer of the raw material particles 44 of about 40 μm is filled. As the raw material particles 44, those obtained by using a molding sand such as zircon sand as a core and coating the surface of the core with a thermoplastic resin are used.

Then, laser light from a laser light source 46 such as a carbon dioxide laser generator is applied to the raw material particles 44 via a mirror 48, and the thermoplastic resin of the raw material particles 44 located at the portion irradiated with the laser light is removed. By selectively melting and hardening (sintering), one thin piece 50 is formed, and the thin pieces 50 are sequentially laminated. The irradiation pattern of the laser beam is controlled by a control device in which a shape to be manufactured is stored in advance.

On the other hand, the lower mold 24 and the upper mold 26 which are outer molds
According to a method previously filed by the applicant of the present invention and disclosed in Japanese Patent Application Laid-Open No. 9-25780, for example, a block obtained by solidifying a granular material is stored in a program (CA
It is manufactured by being directly processed by an automatic control processing machine (NC processing machine) that operates a tool according to M). Thus, the lower mold 24 and the upper mold 26 can be manufactured with a high degree of shape reproducibility without going through a transfer step using a wooden mold.

Therefore, in this embodiment, since all of the upper and lower molds and the core are directly processed, a large number of wooden molds are prepared, and the temperature and the temperature are adjusted to maintain the accuracy of the wooden molds. This eliminates the need for labor such as storage while controlling the humidity, thereby reducing the cost of manufacturing the mold.

[0020]

As described above, according to the present invention,
Since the split core that does not split the cavity itself for casting the product part is used, the shape and dimensions of the cavity are not affected by assembly, and therefore, even in cast products with large dimensions and complicated shapes. It can be cast with high dimensional accuracy by a simple operation.

[Brief description of the drawings]

FIG. 1 is a plan view showing a state in which a core is formed by combining divided cores according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a state in which the core shown in FIG. 1 is set between a lower mold and an upper mold to form a mold.

FIG. 3 is a schematic diagram for explaining an example of manufacturing a split core.

FIG. 4 is a perspective view showing an impeller of a centrifugal rotary machine cast according to an embodiment of the present invention.

FIG. 5 is a plan view showing a state in which a core is formed by combining conventional split cores.

6 is a cross-sectional view showing a state in which the core shown in FIG. 4 is set between a lower mold and an upper mold to form a mold.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Core 12 Split core 12a Same, end surface 14 Cavity 30 Lower mold 32 Upper mold 40 Selection laser sintering apparatus

Continuation of front page (72) Inventor Satoshi Kudo 11-1 Haneda Asahimachi, Ota-ku, Tokyo Inside Ebara Corporation

Claims (4)

[Claims] 1. A casting core including a plurality of cavities for casting a product portion therein, wherein a plurality of divided cores having a dividing surface are assembled at positions between the plurality of cavities. Characteristic core for casting. 2. The casting core according to claim 1, wherein said split core is formed by a rapid forming method. 3. The casting core according to claim 2, wherein the split core is formed hollow. 4. The casting core according to claim 1, wherein the outer mold for accommodating the core is formed by directly processing a sand mold block by an automatic control processing machine.