Mold forming method and plug used in mold forming method

Abstract

To install a plug in a curved portion of a mold to exhaust gas from the cavity to the outside.SOLUTION: In the present invention, a mold is provided with a flow path pt through which a fluid to be discharged from the cavity to the outside can flow, and a vent plug 50 is installed in the flow path, the vent plug having a slit 52 through which the fluid can flow. The slit in the vent plug is formed on a curved surface 51 and is formed by a wire cutting method.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a mold-making method and a plug used in the mold-making method. [Background technology]

[0002] Numerous casting techniques have been known for some time. When creating a mold, sand or other materials are poured into the cavity that will become the mold, but gas inside the cavity must be expelled during this process. One technique for expelling gas inside the cavity involves creating a minute gap between the mating surfaces of a first mold and a second mold when casting is performed using them. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-131269 Summary of the Invention [Problem to be solved by the invention]

[0004] When pouring a material such as sand into a mold cavity, a flow path is provided in part of the mold to discharge gas from the cavity to the outside, and a plug is installed in part of this flow path. The inventors of the present invention have been actively studying the possibility of installing the plug in a curved portion of the mold, in contrast to the conventional location where the plug is installed on a flat portion of the mold.

[0005] The object of the present invention is to provide a plug in the curved surface of the mold to vent gas from the cavity to the outside. [Means for solving the problem]

[0006] One aspect of the present invention is a mold-making method in which sand to be a product is poured into a cavity formed by a mold. The mold is provided with a flow path through which a fluid can flow to be discharged from the cavity to the outside. A plug having a slit through which the fluid can flow is installed in the flow path. At least a portion of the location where the slit is installed in the plug is formed into a curved surface. The slit in the plug is formed by a wire cutting method. Another aspect of the present invention is a plug used in the mold-making method and having the slit. [Effects of the Invention]

[0007] According to the above mold making method and plug, the plug can be placed on the curved surface of the mold to discharge gas from the cavity to the outside. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing how a core is formed using a mold forming apparatus according to an embodiment. [Figure 2] FIG. 1 is a diagram showing how a core is formed using a mold forming apparatus according to an embodiment. [Figure 3] FIG. 1 is a diagram showing how a core is formed using a mold forming apparatus according to an embodiment. [Figure 4] FIG. 1 is a diagram showing how a core is formed using a mold forming apparatus according to an embodiment. [Figure 5] FIG. 10 is a perspective view showing a vent plug that constitutes the mold forming apparatus. [Figure 6] FIG. 6 is a plan view showing the vent plug shown in FIG. 5. [Figure 7] FIG. 6 is a cross-sectional view taken along an axial direction passing through the center of the vent plug shown in FIG. 5. [Figure 8] FIG. 10 is a cross-sectional view showing a vent plug according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same components are designated by the same reference numerals, and redundant explanations will be omitted. In the drawings, the size and proportions of each component are exaggerated to facilitate understanding of the embodiments, and may differ from the actual size and proportions.

[0010] In each figure, arrows representing X, Y, and Z are used to indicate the orientation of the members constituting the mold structure according to the embodiment. X indicates the width direction of the mold, and is referred to as the width direction X. Y indicates the depth direction of the mold, and is referred to as the depth direction Y. Z indicates the height direction of the mold, and is referred to as the height direction Z.

[0011] The vent plug according to this embodiment can be used as part of a mold when forming a casting mold by pouring sand, which will become the product, into a cavity formed by a metal mold and allowing it to harden. The casting mold according to this embodiment is generally configured with a fixed mold 10, a movable mold 20, a blow nozzle 30, an ejector pin 40, and a vent plug 50. The vent plug 50 will be described below after explaining the mold configuration.

[0012] (Fixed type) The fixed mold 10 forms part of the outer wall of the space (cavity) that will become the product during molding of the casting mold, and is configured as a mold that does not move relative to the movable mold 20 as shown in Figures 1 to 4. In this embodiment, the fixed mold 10 is installed below the movable mold 20 in the height direction Z as shown in Figure 1, but the positions of the movable mold and the fixed mold may be reversed as long as the desired shape can be formed.

[0013] 1 to 4, the movable mold 20 is configured to be movable in a predetermined direction relative to the fixed mold 10. In this embodiment, the movable mold 20 is configured to be movable in the height direction Z, but the direction of mold movement is not limited to the vertical direction and may be horizontal or oblique as long as the desired shape can be formed. Either the fixed mold 10 or the movable mold 20 may be provided with a flow path pt that can exhaust gas generated from the cavity.

[0014] The blow nozzle 30 is configured to fill sand into a cavity that will become the product shape. In this embodiment, the blow nozzle 30 is configured to form a closed cavity space together with the fixed mold 10 and the movable mold 20. Gas that hardens the filled sand can be introduced into the cavity from the blow nozzle 30. Although two blow nozzles 30 are shown in Figures 1 to 4, the number and installation positions of the blow nozzles 30 are not limited to those shown in the figures as long as the desired shape can be formed with good yield.

[0015] The ejector pins 40 are configured to be movable relative to the fixed mold 10, and are provided so that when the sand hardens in the cavity, they are pushed out toward the cavity, thereby separating the product from the mold. Although four ejector pins 40 are provided on the side of the fixed mold 10 in Figures 1 to 4, the number and installation positions of the ejector pins are not limited to those shown in the figures as long as the desired shape can be formed.

[0016] The vent plug 50 is provided so as to form a closed space using the fixed mold 10, the movable mold 20, etc., and to discharge gas that may be generated from the cavity to the outside. The vent plug 50 is provided on a flow path pt through which gas such as air can flow to be discharged from the cavity to the outside. The vent plug 50 can be installed in a location facing the cavity other than the installation position of the blow nozzle 30 on the movable mold 20 (see FIG. 5). The vent plug 50 can be made of stainless steel, etc.

[0017] The vent plug 50 has a flat surface 53 on the back side (upper side in FIG. 5, lower side in FIG. 8) that will become the product, and is formed so that the shape of the cavity side (lower side in FIG. 5, upper side in FIG. 8) includes a curved surface 51. The vent plug 50 has a side surface 54 shaped like the side surface of a cylinder, and is configured to provide an internal space sp1 for discharging (circulating) gas inside. The inner surface that forms the space is approximately concentric with the cylindrical side surface and can be configured to have a smaller diameter than the outer surface. Furthermore, the surface 55 in the internal space sp1 that corresponds to the curved surface 51 is formed to have a step, but a shape other than a step may be used as long as the wall thickness can be ensured and molding is easy.

[0018] The vent plug 50 is configured so that a plurality of slits 52 extending in one direction are provided on the surface at a portion where curved surface 51, which is on the cavity side, is formed. The slits 52 are configured so that they communicate with the cylindrical internal space sp1. The slits 52 are provided on the curved surface 51. Two slits 52 are formed so as to extend in the depth direction of the page, but the number of slits and the extending direction may be other than those shown in the drawing.

[0019] The slits 52 can be formed by wire cutting. Wire cutting is a machining method that utilizes the discharge phenomenon between the workpiece and an extremely thin wire electrode. Conventionally, vent plugs were installed on flat parts of the mold, which prevented air from being discharged from complex curved surfaces, hindering sand filling. Furthermore, even when slits were installed on curved surfaces with existing vent plugs, they were formed by cutting, which deformed the slits during the cutting process, resulting in a problem of reduced exhaust capacity.

[0020] In contrast, in this embodiment, an electric current is passed through a wire electrode, and the heat melts the metal while cutting, enabling precision machining, even with hard materials as long as they are conductive. By forming the slits in this way, air can be reliably evacuated even if the material includes a curved surface, as described above. Furthermore, the slit portion is less likely to deform during formation.

[0021] Alternatively, the vent plug slit could be formed as a groove of the same width from the cavity side to the back side. However, in that case, if sand gets into the slit, it cannot be removed and can become clogged, which could reduce the exhaust capacity.

[0022] In response to this problem, in this embodiment, the slit 52 of the vent plug 50 is tapered. That is, the taper of the slit 52 is formed like a groove in which the width of the slit 52 gradually increases from the cavity side to the back side. This configuration prevents or suppresses the inclusion and accumulation of sand, and allows the core sand to be removed. Furthermore, even if sand or the like accumulates, it can be easily removed by cleaning from the cavity side, and the exhaust capacity can be easily restored.

[0023] Furthermore, the dimension of the taper on the cavity side of the slit 52 is set so that the dimension on the smaller side of the taper is slightly larger (similar) to the grain size of the sand, while the dimension on the rear side (the larger side of the taper) is set to a width at least twice the average grain size. As a specific example, the dimension d1 on the cavity side can be set to 0.2 or 0.3 mm, and the dimension d2 on the rear side can be set to 0.5 or 0.6 mm (see Figure 7).

[0024] If the width is too narrow, sufficient exhaust cannot be achieved, while if it is too wide, too much core sand will be exhausted along with the air, which may actually worsen the filling performance. Furthermore, if the width is too wide, the pitch between adjacent slits must be wide, which reduces the number of slits and prevents sufficient exhaust. If the width is too narrow, core sand may accumulate. By configuring the slit as described above, it is possible to ensure exhaust capacity while preventing or suppressing core sand from becoming trapped.

[0025] The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the claims. Figure 8 is a cross-sectional view showing a vent plug 50a according to a modified example. As described above, the slit 52 of the vent plug 50 has a tapered shape that widens from the cavity side to the back surface side. However, as long as air can be efficiently exhausted and the slit portion is less likely to deform, the slit portion may be shaped so that its width is constant from the cavity side to the back surface side, as shown in the slit 52a of the vent plug 50a in Figure 8. [Explanation of symbols]

[0026] 50 vent plug, 51 curved surface, 52 slits, d1, d2 dimensions, pt flow path, X width direction, Y depth direction, Z height direction.

Claims

1. A method for forming a mold by pouring sand into a cavity formed by a metal mold and allowing it to harden, The mold is provided with a flow path through which a fluid to be discharged from the cavity to the outside can flow, a plug having a slit through which the fluid can flow is provided in the flow path, The location of the slit in the plug is at least partially formed into a curved surface, The method for making a mold, wherein the slit in the plug is formed by a wire cutting method.

2. 2. The mold making method according to claim 1, wherein the slit is formed in a tapered shape from the cavity side toward the back surface of the mold.

3. 3. The mold making method according to claim 2, wherein the slit is formed so that the dimension on the smaller side of the tapered shape is approximately the same as the grain size, and the dimension on the larger side is formed to be at least twice the grain size.

4. A plug used in the mold making method according to any one of claims 1 to 3, the plug having the slit.

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