Method of manufacturing sand mold for casting and tool

Abstract

To provide a method of manufacturing a sand mold for casting allowed to lower the surface roughness in a cavity face.SOLUTION: A method of manufacturing a sand mold for casting 100 includes the step of performing cutting work on a work material 9 made up of foundry sand, to thereby form a sand mold 2 provided with a cavity 29. A tool 1 is continuously pressed at its surface 3 onto a cavity face 22 of the sand mold 2 configuring the cavity 29.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to methods and tools for making sand casting molds. [Background technology]

[0002] Usually, sand molds for casting are made using wooden molds. When a sand mold is made using a wooden mold, it takes time and costs money to make the wooden mold. In addition, it is costly to store the wooden mold.

[0003] As an example of a method for manufacturing a sand mold for casting that does not use a wooden pattern, JP 2005-503929 A (Patent Document 1) describes a method for manufacturing a heat-resistant mold made of molding sand, in which the mold material is cut. The method for manufacturing a heat-resistant mold described in Patent Document 1 includes a step of roughly finishing cutting the inner contour of the mold material with a milling tool, and a step of finish-cutting the mold cavity using the milling tool. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2005-503929 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the method for manufacturing a heat-resistant mold described in Patent Document 1, when the mold material is subjected to finish cutting, the cutting edge of the cutting tool ejects the sand grains from the molding sand. As a result, the surface roughness of the cavity surface of the sand mold that forms the cavity increases compared to when a sand mold is manufactured using a wooden mold.

[0006] The present disclosure has been made in view of the above, and its object is to provide a method and tool for manufacturing a sand mold for casting that can reduce the surface roughness of the cavity surface. [Means for solving the problem]

[0007] The method for manufacturing a sand mold for casting according to the present disclosure includes the following steps: A workpiece made of molding sand is machined to form a sand mold having a cavity, and a surface of a tool is continuously pressed against the cavity surface of the sand mold that forms the cavity. [Effects of the Invention]

[0008] According to the method for manufacturing a sand mold for casting according to the present disclosure, by continuously pressing the surface of a tool against the cavity surface, the sand grains of the molding sand in the convex portions of the surface irregularities can be pushed into the sand mold or scraped off, thereby reducing the surface roughness of the cavity surface. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing a configuration of a sand mold for casting according to a first embodiment. [Figure 2] 1 is an enlarged cross-sectional view showing the configuration of a sand mold for casting according to a first embodiment. [Figure 3] FIG. 1 is a flow chart schematically showing a method for manufacturing a sand mold for casting according to the first embodiment. [Figure 4] FIG. 2 is a partial cross-sectional schematic view showing a process of forming a sand mold by cutting a workpiece. [Figure 5] FIG. 2 is an enlarged schematic cross-sectional view showing a process of forming a sand mold by cutting a workpiece. [Figure 6] 1 is an enlarged cross-sectional view showing the configuration of a sand mold according to embodiment 1. FIG. [Figure 7] 1 is a schematic front view showing the configuration of a tool according to a first embodiment. [Figure 8] FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 7. [Figure 9] 4 is an enlarged schematic cross-sectional view showing a state in which the surface of the tool according to the first embodiment is continuously pressed against the side wall surface of the cavity surface. FIG. [Figure 10]4 is an enlarged schematic plan view showing a state in which the surface of the tool according to the first embodiment is continuously pressed against the side wall surface of the cavity surface. FIG. [Figure 11] 4 is an enlarged schematic cross-sectional view showing a state in which the surface of the tool according to the first embodiment is continuously pressed against the bottom surface of the cavity surface. FIG. [Figure 12] 4 is an enlarged schematic plan view showing a state in which the surface of the tool according to the first embodiment is continuously pressed against the bottom surface of the cavity surface. FIG. [Figure 13] 10 is an enlarged schematic plan view showing a state in which the surface of the tool is continuously pressed against the side wall surface of the cavity surface while the tool is being rotated. FIG. [Figure 14] FIG. 10 is a schematic front view showing the configuration of a tool according to a first modified example of the first embodiment. [Figure 15] 10 is a schematic front view showing the configuration of a tool according to a second modified example of the first embodiment. FIG. [Figure 16] FIG. 10 is a schematic front view showing the configuration of a tool according to a third modified example of the first embodiment. [Figure 17] FIG. 10 is a schematic front view showing the configuration of a tool according to a second embodiment. [Figure 18] FIG. 10 is a schematic bottom view showing the configuration of a tool according to a second embodiment. [Figure 19] 10 is an enlarged schematic cross-sectional view showing a state in which the surface of the tool according to the second embodiment is continuously pressed against the side wall surface of the cavity surface. FIG. [Figure 20] FIG. 10 is a schematic front view showing the configuration of a tool according to a first modified example of the second embodiment. [Figure 21] 10 is a schematic side view showing the configuration of a tool according to a first modified example of the second embodiment. FIG. [Figure 22] 10 is an enlarged schematic cross-sectional view showing a state in which the surface of the tool according to the first modified example of the second embodiment is continuously pressed against the bottom surface of the cavity surface. FIG. [Figure 23] FIG. 10 is a schematic front view showing the configuration of a tool according to a second modified example of the second embodiment. [Figure 24] 10 is a schematic side view showing the configuration of a tool according to a second modified example of the second embodiment. FIG. [Figure 25]10 is an enlarged schematic cross-sectional view showing a state in which the surface of a tool according to a second modification of the second embodiment is continuously pressed against a corner of the cavity surface. FIG. [Figure 26] FIG. 10 is a schematic perspective view showing the configuration of a sand mold for casting according to a third embodiment. [Figure 27] FIG. 10 is a schematic plan view showing the configuration of a sand mold for casting according to a third embodiment. [Figure 28] FIG. 10 is a cross-sectional view showing the configuration of a sand mold for casting according to a third embodiment. [Figure 29] FIG. 11 is a schematic perspective view showing the configuration of a tool according to a third embodiment. [Figure 30] FIG. 11 is a schematic plan view showing the configuration of a tool according to a third embodiment. [Figure 31] FIG. 11 is a schematic front view showing the configuration of a tool according to a third embodiment. [Figure 32] FIG. 11 is a schematic plan view showing a state in which the surface of the tool according to the third embodiment is continuously pressed against the side wall surface of the cavity surface. [Figure 33] 10 is a partial cross-sectional schematic view showing a state in which the surface of the tool according to the third embodiment is continuously pressed against the corners and bottom surface of the cavity surface. FIG. [Figure 34] 11 is a partial cross-sectional schematic view showing a state in which the surface of the tool according to the third embodiment is continuously pressed against the bottom surface of the cavity surface. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0011] Embodiment 1 First, an example of a casting sand mold 100 manufactured using the method for manufacturing a casting sand mold according to embodiment 1 will be described. The casting sand mold 100 is made of foundry sand such as furan sand. The casting sand mold is formed by bonding and hardening the sand grains of the foundry sand with a resin or the like.

[0012] As shown in FIG. 1, the outer shape of the casting sand mold 100 is, for example, a rectangular parallelepiped. The casting sand mold 100 has a plane 21 and a cavity surface 22. The direction perpendicular to the plane 21 is the Z direction. A cavity 29 is provided in the plane 21. From another perspective, the cavity 29 opens at the plane 21. The opening direction of the cavity 29 is parallel to the Z direction. The cavity surface 22 is continuous with the plane 21. The cavity surface 22 forms the cavity 29. The cavity surface 22 is, for example, concave.

[0013] FIG. 2 shows a cross section perpendicular to plane 21. As shown in FIG. 2, casting sand mold 100 is formed by a plurality of sand grains 28. Cavity surface 22 is formed by the surfaces of each of the plurality of sand grains 28 exposed in cavity 29. Cavity surface 22 has, for example, side wall surface 25 and bottom surface 26. Side wall surface 25 extends along the Z direction. Bottom surface 26 is continuous with side wall surface 25. Bottom surface 26 may be perpendicular to side wall surface 25, for example. The ridge between side wall surface 25 and bottom surface 26 forms corner 27. In the cross section perpendicular to plane 21, corner 27 may be arc-shaped.

[0014] Next, a method for manufacturing the sand casting mold 100 according to the first embodiment will be described.

[0015] As shown in Figure 3, the manufacturing method for the casting sand mold 100 according to embodiment 1 includes a step of preparing a workpiece (S10), a step of creating a machining path (S20), a step of forming a sand mold by cutting the workpiece (S30), and a step of continuously pressing the surface of a tool against the cavity surface of the sand mold (S40).

[0016] First, a step (S10) of preparing a workpiece is carried out. For example, the workpiece 9 is prepared by solidifying foundry sand such as furan sand. The workpiece 9 is a sand block. The workpiece 9 has, for example, a rectangular parallelepiped shape.

[0017] Next, a step (S20) of creating a machining path is carried out. Specifically, CAD (Computer Aided Design) data is created for the casting sand mold 100 to be manufactured. Based on the created CAD data, CAM (Computer Aided Manufacturing) software is used to create a machining path (tool path) to be used in a step (S30) of forming a sand mold by cutting a workpiece material (described below) and a step (S40) of continuously pressing the surface of a tool against the cavity surface of the sand mold.

[0018] In this specification, the machining path used in the step (S30) of forming a sand mold by cutting the workpiece is referred to as the first machining path. The machining path used in the step (S40) of continuously pressing the surface of the tool against the cavity surface of the sand mold is referred to as the second machining path. Each of the first machining path and the second machining path is converted into NC (Numerical Control) data. The NC data is input to the machine tool 7.

[0019] The order in which the step (S10) of preparing a workpiece and the step (S20) of creating a machining path are performed is not particularly limited. Specifically, the step (S20) of creating a machining path may be performed before the step (S10) of preparing a workpiece. The step (S10) of preparing a workpiece and the step (S20) of creating a machining path may be performed in parallel.

[0020] Next, a step (S30) of forming a sand mold by cutting the workpiece is performed. As shown in Fig. 4, workpiece 9 is placed on, for example, support table 6. A machine tool 7 is prepared. Machine tool 7 is, for example, a numerically controlled (NC) machine tool.

[0021] A cutting tool 8 is attached to the machine tool 7. The cutting tool 8 is not particularly limited, but is, for example, an end mill. The machine tool 7 moves the cutting tool 8 along a first machining path. This cuts the workpiece 9. A cavity 29 is formed in the workpiece 9. In this way, the sand mold 2 is formed.

[0022] The process by which the workpiece 9 is cut will now be described in detail. As shown in FIG. 5 , the cutting tool 8 has a plurality of cutting edges 82. While the cutting tool 8 is rotating in the direction of arrow A1, the plurality of cutting edges 82 come into contact with the workpiece 9. The cutting tool 8 and the workpiece 9 come into intermittent contact. From another perspective, the sand grains 28 of the foundry sand that make up the workpiece 9 repeatedly come into contact with and separate from the plurality of cutting edges 82, or come into contact with only one of the plurality of cutting edges 82 just once.

[0023] When the multiple cutting edges 82 come into contact with the sand grains 28, the sand grains 28 are broken or ejected. When the sand grains 28 are ejected, they are ejected individually or in clumps of multiple grains joined together. In particular, when the sand grains 28 are ejected in clumps, depressions are formed in the cavity surface 22 at the positions where the ejected sand grains 28 were located. In other words, irregularities are formed on the cavity surface 22. Furthermore, when the ejected sand grains 28 or clumps of sand grains 28 collide with the cavity surface 22, other sand grains 28 or clumps of sand grains 28 are ejected, forming irregularities on the cavity surface 22. This increases the surface roughness of the cavity surface 22.

[0024] 6, the sand mold 2 has a flat surface 21 and a cavity surface 22. A cavity 29 is provided in the sand mold 2. The flat surface 21, the cavity surface 22, and the cavity 29 of the sand mold 2 correspond to the flat surface 21, the cavity surface 22, and the cavity 29 of the casting sand mold 100, respectively.

[0025] In FIG. 6, a virtual plane P is indicated by a two-dot chain line. The virtual plane P is the outer edge of the space through which the cutting tool 8 passes when the cutting tool 8 moves along the first machining path. From another perspective, the virtual plane P overlaps with the cavity surface 22 that is assumed to be formed by the cutting tool 8 in the CAD data. The cavity surface 22 of the sand mold 2 formed by cutting does not overlap with the virtual plane P due to the falling off of sand grains 28, etc.

[0026] As described above, the surface roughness of cavity surface 22 of sand mold 2 is relatively large because sand grains 28 are ejected from cavity surface 22 by cutting using cutting tool 8. Specifically, after step (S30) of forming a sand mold by cutting the workpiece, the maximum height roughness (Rz) of cavity surface 22 is, for example, greater than 500 μm. Rz is a surface texture parameter defined in JIS B0601:2013.

[0027] Next, a step (S40) of continuously pressing the surface of the tool against the cavity surface of the sand mold is carried out. The configuration of tool 1 used in the step (S40) of continuously pressing the surface of the tool against the cavity surface of the sand mold will be described.

[0028] As shown in FIG. 7, the tool 1 has a pressing portion 11 and a gripped portion 12. The gripped portion 12 is a portion that is gripped by the machine tool 7 (see FIG. 4). The gripped portion 12 has, for example, a cylindrical shape. The direction in which the gripped portion 12 extends is defined as an axial direction 101. The gripped portion 12 has a second outer peripheral surface 35. The second outer peripheral surface 35 is annular.

[0029] The pressing portion 11 is supported by the grasped portion 12. Specifically, the pressing portion 11 is, for example, connected to the grasped portion 12. From another perspective, the grasped portion 12 and the pressing portion 11 are, for example, integrated. The pressing portion 11 forms a surface 3. The surface 3 is the surface that is pressed against the sand mold 2 (see FIG. 6).

[0030] The pressing portion 11 has, for example, a cylindrical shape. The diameter (first diameter D1) of the pressing portion 11 is larger than the diameter (second diameter D2) of the gripped portion 12. The central axis of the pressing portion 11 is defined as a first central axis O1. The first central axis O1 extends, for example, along the axial direction 101. The first central axis O1 may overlap with the central axis of the gripped portion 12. The first central axis O1 is surrounded, for example, by a second outer peripheral surface 35. Figure 7 shows the configuration of the tool 1 viewed perpendicular to the first central axis O1.

[0031] The pressing portion 11 has a first outer peripheral surface 15 and a front end surface 16. The first outer peripheral surface 15 surrounds a first central axis O1. When viewed in a direction perpendicular to the first central axis O1, the first outer peripheral surface 15 has, for example, a linear shape. Specifically, when viewed in a direction perpendicular to the first central axis O1, the first outer peripheral surface 15 has, for example, a linear shape extending along the axial direction 101.

[0032] The front end surface 16 is continuous with the first outer peripheral surface 15. The ridge between the first outer peripheral surface 15 and the front end surface 16 forms an angle 17. When viewed along a direction perpendicular to the first center axis O1, the angle formed at the angle 17 between the first outer peripheral surface 15 and the front end surface 16 may be, for example, a right angle.

[0033] The front end surface 16 is flat. When viewed along a direction perpendicular to the first central axis O1, the front end surface 16 is linear. Specifically, when viewed along a direction perpendicular to the first central axis O1, the front end surface 16 is linear and extends along a direction perpendicular to the axial direction 101. When viewed along the first central axis O1, the front end surface 16 is, for example, circular.

[0034] The first outer peripheral surface 15 and the front end surface 16 constitute the surface 3. The Rz of the surface 3 is, for example, 500 μm or less, which is smaller than the Rz of the cavity surface 22 of the sand mold 2 (see FIG. 6).

[0035] Fig. 8 shows a cross section perpendicular to the first central axis O1. As shown in Fig. 8, the first outer peripheral surface 15 has a circular shape in the cross section perpendicular to the first central axis O1. In other words, the pressing portion 11 has a circular shape in the cross section perpendicular to the first central axis O1. The first central axis O1 may be located at the center of the first outer peripheral surface 15 in the cross section perpendicular to the first central axis O1.

[0036] Next, the step (S40) of continuously pressing the surface of the tool against the cavity surface of the sand mold will be described. Tool 1 is attached to machine tool 7 (see FIG. 4). Machine tool 7 moves tool 1 along the second machining path. Specifically, as shown in FIGS. 9 and 10, first, first outer peripheral surface 15 of pressing unit 11 is pressed against side wall surface 25 of cavity surface 22. Machine tool 7 moves tool 1 along side wall surface 25 while pressing first outer peripheral surface 15 against side wall surface 25.

[0037] The tool 1 moves, for example, along a direction perpendicular to the first central axis O1. As shown in Fig. 10, the tool 1 moves, for example, along the arrow A2. The tool 1 moves, for example, along the arrow A2 without performing a rotational motion.

[0038] This causes the surface 3 of the tool 1 to be continuously pressed against the cavity surface 22. From another perspective, when viewed from the perspective of the sand grain 28 that constitutes the cavity surface 22, after the sand grain 28 and the tool 1 come into contact, the contact between the sand grain 28 and the tool 1 continues until the tool 1 passes near the sand grain 28. While the tool 1 moves along the cavity surface 22, the surface 3 and the cavity surface 22 continue to be in contact. Note that "continuously pressing" also includes the case where the tool 1 remains stationary for a certain period of time with the surface 3 of the tool 1 pressed against the cavity surface 22.

[0039] As a result, the sand grains 28 are pushed into or scraped away from the sand mold 2 using the pressing unit 11. The shape of the first outer peripheral surface 15 of the tool 1 is transferred to the cavity surface 22. Specifically, as shown in FIG. 9 , when viewed along a direction perpendicular to the first central axis O1, the shape of the first outer peripheral surface 15, which is linear, is transferred to the side wall surface 25 of the cavity surface 22.

[0040] Tool 1 moves so that first outer peripheral surface 15 of tool 1 passes through the interior of sand mold 2 by a first distance E1 relative to the above-mentioned imaginary plane P. From another perspective, after the step (S30) of forming the sand mold by cutting the workpiece, there remains a room for tool 1 to press sand grains 28 by first distance E1. Each of the first machining path and second machining path is created taking into account the room for tool 1 to press sand grains 28 in the step (S40) of continuously pressing the surface of the tool against the cavity surface of the sand mold. First distance E1 depends on the particle size of sand grains 28, but is preferably 0.01 mm or more and 1 mm or less, and more preferably 0.05 mm or more and 0.5 mm or less.

[0041] Next, as shown in FIGS. 11 and 12 , the front end surface 16 of the pressing unit 11 is pressed against the bottom surface 26 of the cavity surface 22. The machine tool 7 moves the tool 1 along the bottom surface 26 while pressing the front end surface 16 against the bottom surface 26. As shown in FIG. 12 , the tool 1 moves, for example, along arrows A3 and A4. Specifically, after moving, for example, along arrow A3, the tool 1 moves away from the bottom surface 26. The tool 1 is pressed against the bottom surface 26 again at the starting point of arrow A4. Thereafter, the tool 1 moves along arrow A4. By repeating similar movements, the shape of the front end surface 16 of the tool 1 is transferred to the bottom surface 26.

[0042] 11, the tool 1 moves so that the bottom surface 26 of the tool 1 passes through the interior of the sand mold 2 by a second distance E2 relative to the above-mentioned imaginary plane P. From another perspective, after the step (S30) of forming the sand mold by cutting the workpiece, there remains room for the tool 1 to push the sand grains 28 by the second distance E2. The second distance E2 may be the same as the first distance E1.

[0043] As shown in FIG. 13 , the tool 1 may move along the sidewall surface 25 while rotating around the first central axis O1. The rotation direction R of the tool 1 is determined so that the relative speed of the surface 3 with respect to the cavity surface 22 is small at the contact point between the cavity surface 22 and the surface 3 of the tool 1. When the tool 1 moves along the cavity surface 22 while rotating around the first central axis O1, it is preferable that the movement speed of the tool 1 in the movement direction and the circumferential speed at the surface 3 are the same. For example, the circumferential speed at the surface 3 is 0.8 to 1.2 times the movement speed of the tool 1 in the movement direction. This reduces the relative speed between the sand grains 28 and the surface 3. This effectively prevents the tool 1 from flicking the sand grains 28. The rotation speed of the tool 1 is smaller than the rotation speed of the cutting tool 8 (see FIG. 5 ).

[0044] The method for manufacturing the sand casting mold 100 according to the first embodiment and the effects of the tool will be described.

[0045] Typically, sand molds for casting are made using wooden patterns. When sand molds are made using wooden patterns, a wooden pattern must be made when a prototype casting is made. Therefore, time and cost are required to make the wooden pattern. Furthermore, the cost of storing the wooden pattern is also required. Other methods for making prototype castings include methods using foam molds and lost-wax casting. However, these methods also require a model to make the sand mold, and therefore have the same problems as methods using wooden patterns.

[0046] In recent years, the use of 3D printers has become popular as a method for manufacturing casting sand molds that does not require a model. Its advantage is that even complex-shaped sand molds can be manufactured directly and relatively easily, making it a suitable method for manufacturing core molds. However, when using a 3D printer, the 3D printer itself is expensive, and the materials used for the molding are also expensive. Furthermore, the amount of material used for the molding increases as the amount of sand used in the sand mold increases. Therefore, for master molds that are often relatively large and simple in shape, such as a rectangular parallelepiped with a cavity, the method using a 3D printer is not suitable as a method for manufacturing casting sand molds.

[0047] There is a method for manufacturing a sand mold for casting by using a machine tool to cut out a sand block made of casting sand into the desired shape. This method does not require a wooden model or other model as described above. Furthermore, compared to the method using a 3D printer as described above, the cost required to manufacture a sand mold for casting can be reduced.

[0048] However, when manufacturing a sand mold by cutting, the sand grains that make up the sand mold may be ejected by the cutting edge during the machining process. This increases the surface roughness of the cavity surface that forms the cavity of the sand mold. If a casting is produced using a sand mold with a high surface roughness of the cavity surface, the surface roughness of the casting surface will also increase. Therefore, it is desirable for the surface roughness of the cavity surface to be small.

[0049] The method for manufacturing the sand casting mold 100 according to the first embodiment includes a step (S40) of continuously pressing the surface of a tool against the cavity surface of the sand mold. Therefore, sand grains 28 protruding from the cavity surface 22 can be pressed into the sand mold 2 using the tool 1. This smooths the cavity surface 22. As a result, the surface roughness of the cavity surface 22 can be reduced.

[0050] According to the method for manufacturing the casting sand mold 100 of the first embodiment, the rotational speed of the tool 1 in the step (S40) of continuously pressing the surface of the tool against the cavity surface of the sand mold is lower than the rotational speed of the cutting tool 8 in the step (S30) of cutting the workpiece to form the sand mold. Therefore, the impact applied to the tool 1 when the tool 1 contacts the cavity surface 22 can be reduced compared to the impact applied to the cutting tool 8 when the cutting tool 8 contacts the cavity surface 22. This allows the life of the tool 1 to be extended compared to the life of the cutting tool 8. Furthermore, the surface roughness can be reduced simply by creating CAM and replacing the cutting tool 8 with the tool 1 after cutting. This is easier and more stable than adding a separate step, such as manually polishing the entire cavity surface 22.

[0051] The tool 1 according to the first embodiment has a gripped portion 12 and a pressing portion 11. The pressing portion 11 forms the surface 3. The pressing portion 11 has a cylindrical shape. This allows the shape of the tool 1 to be simplified. This allows the cost required to manufacture the tool 1 to be reduced.

[0052] First variant of embodiment 1. The configuration of the tool 1 according to the present disclosure is not limited to the above configuration. Specifically, as shown in Fig. 14, the corner 17 of the tool 1 may be chamfered. When viewed perpendicularly to the first central axis O1, the corner 17 may be arc-shaped. In this way, when the corner 27 (see Fig. 2) of the casting sand mold 100 is arc-shaped in a cross section perpendicular to the plane 21 of the casting sand mold 100, the surface roughness of the corner 27 can be efficiently reduced by continuously pressing the corner 17 of the tool 1 against the corner 27.

[0053] When a corner 27 (see FIG. 2) of the casting sand mold 100 is arc-shaped in a cross section perpendicular to the plane 21 of the casting sand mold 100, the radius of curvature of the corner 17 of the tool 1 (first radius of curvature R1) may be substantially the same as the radius of curvature of the corner 27 (second radius of curvature). The first radius of curvature R1 may be smaller than the second radius of curvature.

[0054] Second variant of embodiment 1. 15, the shape of the pressing portion 11 may be, for example, tapered. Specifically, the diameter of the first outer peripheral surface 15 may decrease toward the front end face 16 along the axial direction 101. The first diameter D1 is the maximum diameter of the pressing portion 11. The first diameter D1 is larger than the diameter of the front end face 16 (third diameter D3). When viewed along a direction perpendicular to the first central axis O1, the angle formed between the first outer peripheral surface 15 and the front end face 16 at angle 17 is an obtuse angle.

[0055] When viewed perpendicularly to the first central axis O1, the first outer peripheral surface 15 is inclined with respect to the first central axis O1. As a result, when a draft is provided on a side wall surface 25 (see FIG. 2 ) of the cavity surface 22, the surface roughness of the side wall surface 25 can be efficiently reduced by pressing the first outer peripheral surface 15 against the side wall surface 25. When viewed perpendicularly to the first central axis O1, the inclination angle of the outer peripheral surface with respect to the first central axis O1 is substantially the same as the draft of the cavity surface 22, for example.

[0056] Third modification of the first embodiment. Although the configuration in which the graspable portion 12 is cylindrical has been described above, the configuration of the graspable portion 12 is not limited to the above configuration. As shown in Fig. 16, the graspable portion 12 may be, for example, L-shaped. Specifically, the graspable portion 12 may have a first portion 13 and a second portion 14.

[0057] The first portion 13 is, for example, cylindrical. The first portion 13 extends along the first central axis O1. The first portion 13 constitutes the second outer peripheral surface 35. The diameter of the first portion 13 is a second diameter D2. The second portion 14 is continuous with the first portion 13. The second portion 14 extends in a direction perpendicular to the first central axis O1. The second portion 14 is a portion that is gripped by the machine tool 7 (see FIG. 2).

[0058] Embodiment 2 Next, a method for manufacturing the sand casting mold 100 and the configuration of the tool 1 according to the second embodiment will be described. The tool 1 according to the second embodiment differs from the tool 1 according to the first embodiment mainly in that the pressing portion 11 rotates relative to the gripped portion 12, but is substantially identical to the tool 1 according to the first embodiment in other respects. The following description will focus on the method for manufacturing the sand casting mold 100 according to the first embodiment and the differences from the tool 1.

[0059] The tool 1 according to the second embodiment has a roller mechanism. Specifically, the pressing portion 11 rotates relative to the gripped portion 12. The pressing portion 11 rotates around a first central axis O1. From another perspective, the first central axis O1 is the rotation axis of the pressing portion 11.

[0060] The pressing portion 11 is composed of a shaft portion 19 and a pressing portion 18. The shaft portion 19 is attached to the grasped portion 12. The shaft portion 19 has a cylindrical shape. The central axis of the shaft portion 19 may overlap with the first central axis O1.

[0061] The pressing portion 18 is connected to the shaft portion 19. In other words, the pressing portion 18 and the shaft portion 19 are integral. The pressing portion 18 is spaced apart from the grasped portion 12. The central axis of the pressing portion 18 may overlap with the first central axis O1. The pressing portion 18 constitutes the surface 3. The pressing portion 18 is, for example, cylindrical in shape. The pressing portion 18 has a first end face 31. In the pressing portion 18, the first end face 31 is opposite the front end face 16.

[0062] The gripped portion 12 has a second end surface 36. The second end surface 36 is continuous with the second outer peripheral surface 35. The second end surface 36 faces, for example, the first end surface 31. The shaft portion 19 extends from the first end surface 31 toward the second end surface 36.

[0063] 18, when viewed along the first central axis O1, the surface 3 has a circular shape. When viewed along the first central axis O1, the first central axis O1 is located at the center of the surface 3.

[0064] 19, in the step (S40) of continuously pressing the surface of the tool against the cavity surface of the sand mold, for example, pressing portion 18 is pressed against side wall surface 25 of cavity surface 22. Machine tool 7 (see FIG. 4) moves tool 1 in a direction perpendicular to first central axis O1 without rotating tool 1.

[0065] The pressing portion 11 rotates around the first central axis O1 as the tool 1 moves along the side wall surface 25 while pressing the pressing portion 18 against the side wall surface 25. From another perspective, the pressing portion 11 rotates passively due to the frictional force generated between the surface 3 and the cavity surface 22.

[0066] According to the tool 1 of the second embodiment, the pressing part 11 rotates relative to the gripped part 12. Therefore, when the surface 3 of the tool 1 is continuously pressed against the cavity surface 22 during the manufacturing process of the casting sand mold 100, the pressing part 11 can be rotated relative to the cavity surface 22 without rotating the gripped part 12. This makes it possible to easily reduce the relative velocity between the sand grains 28 of the foundry sand and the surface 3. Therefore, it is possible to easily prevent the tool 1 from flicking the sand grains 28.

[0067] According to the method for manufacturing the casting sand mold 100 of the second embodiment, in the step (S40) of continuously pressing the surface of the tool against the cavity surface of the sand mold, the tool 1 moves along the side wall surface 25 while pressing the pressing portion 18 against the side wall surface 25, thereby rotating the pressing portion 11 around the first central axis O1. This allows the machine tool 7 (see FIG. 4) to rotate the pressing portion 11 without rotating the gripped portion 12. This simply reduces the relative velocity between the sand grains 28 of the foundry sand and the surface 3. This simply prevents the tool 1 from flicking the sand grains 28 away.

[0068] First variant of embodiment 2. Although the configuration in which the central axis of the pressing portion 11 and the central axis of the gripped portion 12 are substantially parallel has been described above, the configuration of the tool 1 according to the second embodiment is not limited to the above configuration. As shown in Figures 20 and 21, the central axis of the pressing portion 11 (first central axis O1) may be inclined with respect to the central axis of the gripped portion 12 (second central axis O2). The first central axis O1 is, for example, perpendicular to the second central axis O2.

[0069] The first outer peripheral surface 15 extends in a direction perpendicular to the second central axis O2. At the second outer peripheral surface 35, the shaft portion 19 is attached to the gripped portion 12. The shaft portion 19 extends from the first end surface 31 toward the second outer peripheral surface 35.

[0070] As shown in FIG. 22 , in the step (S40) of continuously pressing the surface of the tool against the cavity surface of the sand mold, the tool 1 is moved along the bottom surface 26 of the cavity surface 22 while pressing the first outer peripheral surface 15 of the pressing portion 18 against the bottom surface 26 of the cavity surface 22. The tool 1 is moved, for example, along a direction perpendicular to each of the first central axis O1 and the second central axis O2. This causes the pressing portion 11 to rotate around the first central axis O1. The tool 1 according to the first modification of the second embodiment can efficiently reduce the surface roughness of the bottom surface 26 of the cavity surface 22. From another perspective, the surface roughness of the portion of the cavity surface 22 extending in a direction perpendicular to the central axis of the gripped portion 12 can efficiently be reduced.

[0071] Second variant of embodiment 2. 23 and 24, the pressing portion 18 may be disk-shaped. When viewed perpendicularly to the first central axis O1, the first outer peripheral surface 15 may be arc-shaped. The shaft portion 19 may pass through the pressing portion 18. Both ends of the shaft portion 19 are supported by the grasped portion 12.

[0072] When viewed perpendicularly to the first central axis O1, the radius of curvature (third radius of curvature R3) of the first outer peripheral surface 15 may be substantially the same as the radius of curvature (second radius of curvature) of the corner 27 (see FIG. 2) of the casting sand mold 100. The third radius of curvature R3 may be smaller than the second radius of curvature.

[0073] The grasped portion 12 is composed of, for example, a first portion 13, a first support portion 41, and a second support portion 42. The first support portion 41 is continuous with the first portion 13. The first support portion 41 extends in a direction parallel to the second central axis O2. The second support portion 42 is continuous with the first portion 13. The second support portion 42 extends in a direction parallel to the second central axis O2. The second support portion 42 is spaced apart from the first support portion 41.

[0074] The first support portion 41 and the second support portion 42 support the shaft portion 19. The first support portion 41 and the second support portion 42, for example, sandwich the shaft portion 19 therebetween. The pressing portion 18 is located between the first support portion 41 and the second support portion 42. The pressing portion 18 is spaced apart from each of the first support portion 41 and the second support portion 42. The pressing portion 18 intersects with the second central axis O2.

[0075] 25, in the step (S40) of continuously pressing the surface of the tool against the cavity surface of the sand mold, tool 1 is moved along corner 27 of cavity surface 22 while pressing first outer peripheral surface 15 of pressing portion 18 against corner 27. Tool 1 is moved in a direction perpendicular to each of first central axis O1 and second central axis O2 while being tilted at an angle of 45° with respect to the Z direction, for example. Tool 1 according to the first modification of embodiment 2 can efficiently reduce the surface roughness of corner 27 of cavity surface 22.

[0076] Embodiment 3 Next, a method for manufacturing the sand casting mold 100 and the tool 1 according to the third embodiment will be described. The tool 1 according to the third embodiment differs from the tool 1 according to the first embodiment mainly in that it has the same shape as part of the cavity surface 22, but is otherwise substantially identical to the tool 1 according to the first embodiment. The following description will focus on the differences from the method for manufacturing the sand casting mold 100 and the tool 1 according to the first embodiment.

[0077] First, we will explain an example of a casting sand mold 100 manufactured using the method for manufacturing a casting sand mold 100 according to embodiment 3. As shown in Fig. 26, the casting sand mold 100 according to embodiment 3 and the casting sand mold 100 according to embodiment 1 (see Figs. 1 and 2) have different shapes of cavity surfaces 22.

[0078] As shown in FIG. 27 , the side wall surface 25 has a first side wall surface portion 51, a second side wall surface portion 52, a third side wall surface portion 53, a fourth side wall surface portion 54, and a fifth side wall surface portion 55. In a first plan view perpendicular to the plane 21, the first side wall surface portion 51 is linear. The second side wall surface portion 52 connects the first side wall surface portion 51 and the third side wall surface portion 53. In the first plan view, the second side wall surface portion 52 is arc-shaped. In the first plan view, the third side wall surface portion 53 is linear. In the first plan view, the third side wall surface portion 53 may be perpendicular to the first side wall surface portion 51.

[0079] The fourth side wall surface portion 54 connects the third side wall surface portion 53 and the fifth side wall surface portion 55. In the first plan view, the fourth side wall surface portion 54 is arc-shaped. In the first plan view, the radius of curvature of the second side wall surface portion 52 (fourth radius of curvature R4) may be substantially the same as the radius of curvature of the fourth side wall surface portion 54 (fifth radius of curvature R5). In the first plan view, the fifth side wall surface portion 55 may be perpendicular to the third side wall surface portion 53. In the first plan view, the fifth side wall surface portion 55 is linear.

[0080] As shown in FIG. 28, the bottom surface 26 of the cavity surface 22 has a first bottom surface portion 61, a second bottom surface portion 62, and an inclined surface 63. The first bottom surface portion 61 extends along a plane perpendicular to the Z direction. The first bottom surface portion 61 is planar. In the Z direction, the second bottom surface portion 62 is located between the first bottom surface portion 61 and the plane 21. The second bottom surface portion 62 extends along a plane perpendicular to the Z direction. The second bottom surface portion 62 is planar. The inclined surface 63 connects the first bottom surface portion 61 and the second bottom surface portion 62. The inclined surface 63 is inclined with respect to each of the first bottom surface portion 61 and the second bottom surface portion 62.

[0081] Next, the configuration of the tool 1 according to the third embodiment will be described. As shown in Fig. 29, the pressing portion 11 has a connection surface 70. At the connection surface 70, the pressing portion 11 is continuous with the gripped portion 12. The connection surface 70 is, for example, flat.

[0082] As shown in FIG. 30, the front surface 3 has a first side surface portion 71, a second side surface portion 72, a third side surface portion 73, a fourth side surface portion 74, and a fifth side surface portion 75.

[0083] In a second plan view seen perpendicular to the connecting surface 70, the first side surface portion 71 is linear. The second side surface portion 72 connects the first side surface portion 71 and the third side surface portion 73. In the second plan view, the second side surface portion 72 is arc-shaped. The radius of curvature of the second side surface portion 72 in the second plan view (sixth radius of curvature R6) may be substantially the same as the fourth radius of curvature R4 (see FIG. 27). The sixth radius of curvature R6 is, for example, 0.5 to 1 times the fourth radius of curvature R4. The sixth radius of curvature R6 may be, for example, 0.7 times or more, or 0.9 times or more, the fourth radius of curvature R4.

[0084] In the second plan view, the third side surface portion 73 is linear. The fourth side surface portion 74 is continuous with the third side surface portion 73. In the second plan view, the fourth side surface portion 74 is linear. The fifth side surface portion 75 is continuous with each of the first side surface portion 71 and the fourth side surface portion 74. In the second plan view, the fifth side surface portion 75 has a linear connecting surface 70 that is continuous with each of the first side surface portion 71, the second side surface portion 72, the third side surface portion 73, the fourth side surface portion 74, and the fifth side surface portion 75. Each of the first side surface portion 71, the second side surface portion 72, the third side surface portion 73, the fourth side surface portion 74, and the fifth side surface portion 75 is a surface that is pressed against the sand mold 2.

[0085] FIG. 31 shows the configuration of the tool 1 viewed perpendicularly to the fourth side surface portion 74. As shown in FIG. 31, the surface 3 has a flat surface portion 76. The flat surface portion 76 extends along a plane perpendicular to the second central axis O2. The flat surface portion 76 is connected to each of the first side surface portion 71, the second side surface portion 72, the third side surface portion 73, the fourth side surface portion 74, and the fifth side surface portion 75. The flat surface portion 76 is the surface that is pressed against the sand mold 2. The connecting surface 70 extends along a plane perpendicular to the second central axis O2.

[0086] The fifth side surface portion 75 is flat. The fifth side surface portion 75 is parallel to the second central axis O2. When viewed perpendicular to the fourth side surface portion 74, the third side surface portion 73 is arc-shaped. When viewed perpendicular to the fourth side surface portion 74, the radius of curvature of the third side surface portion 73 (seventh radius of curvature R7) may be substantially the same as the radius of curvature of the corner portion 27 of the cavity surface 22 (second radius of curvature R2, see FIG. 28). The seventh radius of curvature R7 may be smaller than the second radius of curvature R2.

[0087] Next, a method for manufacturing a casting sand mold 100 according to embodiment 3 will be described. As shown in Fig. 32, in the step (S40) of continuously pressing the surface of the tool against the cavity surface of the sand mold, the tool 1 is moved so as to press the first side wall surface portion 51, the second side wall surface portion 52, the third side wall surface portion 53, the fourth side wall surface portion 54, and the fifth side wall surface portion 55 in this order. In Fig. 32, arrow A5 indicates the direction in which the tool 1 moves.

[0088] 32, in the process of moving the tool 1, the first side surface portion 71 and the second side surface portion 72 are simultaneously pressed against the first side wall surface portion 51 and the second side wall surface portion 52, respectively. Thereafter, the second side surface portion 72 and the third side surface portion 73 are pressed against the second side wall surface portion 52 and the third side wall surface portion 53, respectively.

[0089] Although not shown, in the process of moving the tool 1 along the arrow A5, the tool 1 is rotated 90° around the second central axis O2 (see FIG. 31). As a result, the first side surface portion 71 and the second side surface portion 72 are simultaneously pressed against the third side wall surface portion 53 and the fourth side wall surface portion 54, respectively. Thereafter, the second side surface portion 72 and the third side surface portion 73 are pressed against the fourth side wall surface portion 54 and the fifth side wall surface portion 55, respectively.

[0090] As shown in FIG. 33, in the process of moving the tool 1 along the arrow A5, the third side surface portion 73 and the flat surface portion 76 of the pressing portion 11 are pressed against the corner portion 27 and the second bottom surface portion 62 of the sand mold 2, respectively.

[0091] 34, with the tool 1 tilted with respect to the Z direction, the fifth side surface portion 75 is pressed against the inclined surface 63 of the sand mold 2. Specifically, the tool 1 is tilted with respect to the Z direction so that the fifth side surface portion 75 is parallel to the inclined surface 63. With the fifth side surface portion 75 pressed against the inclined surface 63, the tool 1 is moved along the inclined surface 63, whereby the fifth side surface portion 75 is continuously pressed against the inclined surface 63.

[0092] According to the tool 1 according to the third embodiment, the surface 3 of the tool 1 has a first side surface portion 71 and a second side surface portion 72. The cavity surface 22 of the sand mold 2 has a first side wall surface portion 51 and a second side wall surface portion 52. The radius of curvature of the second side surface portion 72 when viewed perpendicularly to the connection surface 70 of the tool 1 is 0.5 to 1 times the radius of curvature of the second side wall surface portion 52 when viewed in the Z direction.

[0093] Therefore, in the manufacturing process of the sand mold 100 for casting, the first side surface portion 71 and the second side surface portion 72 of the tool 1 can be simultaneously pressed against the first side wall surface portion 51 and the second side wall surface portion 52 of the sand mold 2, respectively. This increases the contact area between the tool 1 and the sand mold 2. This also shortens the travel distance of the tool 1. As a result, productivity in manufacturing the sand mold 100 for casting can be improved.

[0094] According to the method for manufacturing the sand mold for casting 100 of the third embodiment, in the step (S40) of continuously pressing the surface of the tool against the cavity surface of the sand mold, the first side surface portion 71 and the second side surface portion 72 of the tool 1 are simultaneously pressed against the first side wall surface portion 51 and the second side wall surface portion 52 of the sand mold 2, respectively. This increases the contact area between the tool 1 and the sand mold 2. This therefore shortens the travel distance of the tool 1. As a result, productivity in the manufacturing of the sand mold for casting 100 can be improved.

[0095] In the method for manufacturing the sand casting mold 100 according to the present disclosure, the tools 1 according to each of the first, second, and third embodiments and their modifications may be used in combination.

[0096] The embodiments disclosed herein are to be considered as illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the above description, and is intended to include meanings equivalent to the claims and all modifications within the scope thereof. [Explanation of symbols]

[0097] 1 Tool, 2 Sand mold, 3 Surface, 6 Support table, 7 Machine tool, 8 Cutting tool, 9 Workpiece, 11 Pressing part, 12 Holding part, 13 Part 1, 14 Part 2, 15 First outer peripheral surface, 16 Front end face, 17 Corner, 18 Pressing part, 19 Shaft part, 21 Plane, 22 Cabinet surface, 25 Side wall surface, 26 Bottom surface, 27 Corner, 28 Sand grain, 29 Cabinet, 31 First end face, 35 Second outer peripheral surface, 36 Second end face, 41 First support part, 42 Second support part, 51 First side wall surface, 52 Second side wall surface, 53 Third side wall surface, 54 Fourth side wall surface, 55 5th side face, 61 1st bottom face, 62 2nd bottom face, 63 Inclined surface, 70 Connecting surface, 71 1st side face, 72 2nd side face, 73 3rd side face, 74 4th side face, 75 5th side face, 76 Planar part, 82 Cutting edge, 100 Casting sand mold, 101 Axial direction, A1, A2, A3, A4, A5 Arrow marks, D1 1st diameter, D2 2nd diameter, D3 3rd diameter, E1 1st distance, E2 2nd distance, O1 1st central axis, O2 2nd central axis, P Imaginary surface, R Rotation direction, R1 1st radius of curvature, R2 2nd radius of curvature, R3 3rd radius of curvature, R4 4th radius of curvature, R5 5th radius of curvature, R6 6th radius of curvature, R7 7th radius of curvature.

Claims

1. a step of forming a sand mold having a cavity by cutting a workpiece made of foundry sand; and continuously pressing a surface of a tool against a cavity surface of the sand mold that defines the cavity.

2. A tool used in the method for manufacturing a sand mold for foundry according to claim 1, a gripped part that is gripped by a machine tool; a pressing portion supported by the gripped portion and constituting the surface.

3. The pressing portion has a cylindrical shape, The pressing unit is an outer peripheral surface surrounding the central axis of the pressing portion; a front end surface connected to the outer circumferential surface, The tool of claim 2 , wherein the outer circumferential surface and the front end surface define the surface.

4. A method for manufacturing a sand mold for casting using the tool according to claim 3, comprising the steps of: A method for manufacturing a sand mold for casting, wherein in the step of continuously pressing the surface of the tool against the cavity surface, the tool is moved along the cavity surface while pressing the surface against the cavity surface.

5. The pressing portion rotates relative to the gripped portion, The tool of claim 2 , wherein the surface is circular when viewed along the axis of rotation of the abutment portion.

6. A method for manufacturing a sand mold for casting using the tool according to claim 5, A method for manufacturing a sand mold for casting, wherein in the step of continuously pressing the surface of the tool against the cavity surface, the tool is moved along the cavity surface while being pressed against the cavity surface, thereby causing the pressing portion to rotate around the rotation axis.

7. The cavity surface is a first side wall surface portion that is linear when viewed in a direction parallel to the opening direction of the cavity; a second side wall surface portion that is continuous with the first side wall surface portion and has an arc shape when viewed in a direction parallel to the opening direction, The pressing portion has a connection surface that is connected to the gripped portion, The surface is a first side surface portion that is linear when viewed perpendicular to the connection surface; a second side surface portion that is continuous with the first side surface portion and has an arc shape when viewed perpendicularly to the connection surface, The tool described in claim 2, wherein the radius of curvature of the second side surface portion when viewed perpendicular to the connection surface is 0.5 to 1 times the radius of curvature of the second side wall surface portion when viewed in a direction parallel to the opening direction.

8. A method for manufacturing a sand mold for casting using the tool according to claim 7, comprising the steps of: a step of continuously pressing the surface of the tool against the cavity surface, wherein the first side surface portion and the second side surface portion are simultaneously pressed against the first side wall surface portion and the second side wall surface portion, respectively.

Images