Mold and method for manufacturing powder molded body

Abstract

A mold comprising: a die that has a hollow section penetrating therethrough in a first direction; a first core that splits the hollow section into a plurality of spaces which are arranged in a direction orthogonally intersecting the first direction; and an upper punch and a lower punch that are fitted into each of the plurality of spaces, wherein the first core comprises a partial region that is provided midway in the first direction in a side surface facing the plurality of spaces, and the partial region includes a protrusion protruding from the side surface.

Description

Technical Field

[0001] The present disclosure relates to a mold and a method for manufacturing a powder compact. This application claims priority based on Japanese Patent Application No. 2022-128789 filed on August 12, 2022, and incorporates all the descriptions set forth in the Japanese application.

Background Art

[0002] Patent Document 1 discloses a mold for manufacturing a molded body having an undercut shape. This mold includes a first die, a second die, a first punch, and a second punch. The second die is provided with an undercut molding portion for imparting an undercut shape to the molded body. The second die is inserted into the through-hole of the first die such that the outer surface contacts the inner surface of the through-hole. The molded body is molded by compressing powder in a cavity surrounded by the inner surface of the through-hole, the second die, the first punch, and the second punch.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The mold of the present disclosure includes a die having a hollow portion penetrating in a first direction, a first core that divides the hollow portion into a plurality of space portions arranged in parallel in a direction orthogonal to the first direction, and an upper punch and a lower punch fitted into each of the plurality of space portions. The first core includes a partial region provided in the middle of the first direction on a side surface facing the plurality of space portions, and the partial region includes a protrusion protruding from the side surface.

Brief Description of the Drawings

[0005] [Figure 1] FIG. 1 is a cross-sectional view of the mold according to the embodiment. [Figure 2] Figure 2 is a longitudinal cross-sectional view of the mold according to the embodiment, showing the state in which the upper punch, lower punch, first core, and second core are not inserted into the die. [Figure 3] Figure 3 is a longitudinal cross-sectional view of the mold according to the embodiment, showing the lower punch, first core, and second core inserted into the die, but the upper punch not inserted into the die. [Figure 4] Figure 4 is a perspective view of a powder molded body formed using a mold according to the embodiment. [Figure 5] Figure 5 is an explanatory diagram of the powder filling step in the method for manufacturing a powder molded body using a mold according to the embodiment. [Figure 6] Figure 6 is an explanatory diagram of the process for molding a powder molded body in a method for manufacturing a powder molded body using a mold according to the embodiment. [Figure 7] Figure 7 is an explanatory diagram of the process for removing a powder molded body in a method for manufacturing a powder molded body using a mold according to the embodiment. [Modes for carrying out the invention]

[0006] [Issues this disclosure aims to address] The mold disclosed in Patent Document 1 comprises a cavity into which powder is filled. When the powder in the cavity is compressed, lateral pressure from the powder acts on the contact surface between the first die and the second die. When the first die and the second die move relative to each other, the lateral pressure may cause seizure between the first die and the second die.

[0007] One of the objectives of this disclosure is to provide a mold that can suppress seizing of the mold's components during powder compression.

[0008] [Effects of this disclosure] The mold of this disclosure can suppress seizing of the mold's components when the powder is compressed.

[0009] [Description of Embodiments in this Disclosure] First, the embodiments of this disclosure will be listed and described.

[0010] (1) A die according to the embodiment of the present disclosure comprises a die having a hollow portion penetrating in a first direction, a first core dividing the hollow portion into a plurality of spaces arranged in parallel in a direction perpendicular to the first direction, and an upper punch and a lower punch fitted into each of the plurality of spaces, wherein the first core has a partial region provided in the middle of the first direction on a side surface facing the plurality of spaces, and the partial region includes a projection protruding from the side surface.

[0011] The first core, referred to as the core in this disclosure, may be composed of a component generally called a punch, depending on the mold configuration. The first core is not limited in name as long as it is a component that divides the hollow portion into multiple spaces.

[0012] In the mold of this disclosure, multiple spaces are formed, allowing for the production of multiple powder molded bodies in a single compression. Each space is faced by a partial region. Therefore, the mold of this disclosure can efficiently produce powder molded bodies having an undercut shape.

[0013] In the mold of this disclosure, since multiple spaces are formed on either side of the first core, when the powder filled in each space is compressed, the lateral pressure acting on the inner circumferential surface of the die is more likely to act on the contact surface with the powder and less likely to act on the contact surface with the first core. Therefore, even if the first core and the die move relative to each other, seizure is less likely to occur between the first core and the die.

[0014] (2) In the mold described in (1) above, there may be two of the plurality of spaces.

[0015] When two spaces are formed with a first core in between, the direction of lateral pressure from the powder tends to be symmetrical with respect to the first core, and localized excessive lateral pressure is less likely to act. If the direction of the lateral pressure is symmetrical, it is possible to manufacture two powder molded bodies with small local variations in density. A first core that divides the hollow part into two spaces has a simpler structure compared to a first core that divides the hollow part into three or more spaces.

[0016] (3) In the mold of the above (1) or the above (2), all of the plurality of space portions may have the same shape.

[0017] If all of the plurality of space portions have the same shape, a plurality of powder compacts having the same shape can be molded simultaneously. When space portions having the same shape are formed with the first core interposed therebetween, the direction of the lateral pressure from the powder tends to be symmetric with respect to the first core. When space portions having the same shape are formed with the first core interposed therebetween, the powder in the plurality of space portions is compressed evenly, so that stable production can be realized.

[0018] (4) In the mold of any one of the above (1) to the above (3), the first core may be inserted into the hollow portion from the same direction as the lower punch. ]>

[0019] The procedure for manufacturing a powder compact is as follows: First, while the lower punch and the first core are inserted into the hollow portion, powder is filled into each of the plurality of space portions, and then an upper punch is inserted into each of the plurality of space portions, and the powder is compressed by the upper punch and the lower punch. When the lower punch and the first core are inserted into the hollow portion from the same direction, it is easy to form the space filled with powder.

[0020] (5) The mold of any one of the above (1) to the above (4) may further include a second core inserted into each of the plurality of space portions.

[0021] When the second core is provided, the degree of freedom in the shape of the powder compact to be manufactured is increased.

[0022] (6) In the mold of any one of the above (1) to the above (5), the partial region may be the protrusion.

[0023] When the partial region is a protrusion, a powder compact having a concave undercut shape can be manufactured.

[0024] (7) A method for manufacturing a powder molded article according to an embodiment of the present disclosure comprises the steps of: preparing a mold according to any of (1) to (6) above; filling each of the plurality of spaces with powder while the lower punch and the first core are inserted into the hollow part; inserting the upper punch into each of the plurality of spaces and compressing the powder with the upper punch and the lower punch to form a powder molded article; and moving the die and the upper punch relative to the lower punch to remove the powder molded article.

[0025] In the method for manufacturing powder molded articles of this disclosure, since the mold of this disclosure is used, multiple powder molded articles having an undercut shape can be efficiently manufactured in a single compression. In the method for manufacturing powder molded articles of this disclosure, since the mold of this disclosure is used, even if the first core and the die move relative to each other, seizure between the first core and the die is less likely to occur.

[0026] [Details of the embodiments of this disclosure] Specific examples of the molds of this disclosure and the methods for manufacturing powder molded articles using the molds of this disclosure will be described with reference to the drawings. Identical reference numerals in the drawings indicate the same or corresponding parts. In each drawing, some parts of the structure may be exaggerated or simplified for ease of explanation. The dimensional ratios of parts in the drawings may also differ from those of the actual parts. However, the present invention is not limited to these examples and is indicated by the claims, and all modifications within the meaning and range equivalent to the claims are intended to be included.

[0027] <Mold> The mold 1 of the embodiment will be described with reference to Figures 1 to 3. The mold 1 comprises a die 2, an upper punch 3, and a lower punch 4. The die 2 and the lower punch 4 constitute a cavity 9. The cavity 9 is filled with powder 9P as shown in Figure 5. The powder molded body 10 shown in Figures 4 and 7 is formed by compressing the powder 9P filled in the cavity 9 with the upper punch 3 and the lower punch 4. Figure 1 shows the mold 1 with its components assembled, cut in a plane perpendicular to the first direction D1 so as to include the upper punch 3. Figure 2 shows the mold 1 before the cavity 9 is formed, cut in a plane along the first direction D1. Figure 3 shows the mold 1 with the cavity 9 formed, cut in a plane along the first direction D1. In Figure 3, the upper punch 3 is located above the cavity 9.

[0028] The first direction D1 is the vertical direction. As shown in Figure 2, the first direction D1 is also the direction in which the hollow section 20 in the die 2 penetrates. The upper punch 3 and the lower punch 4 are fitted into the hollow section 20. In each figure, the first direction D1 is indicated by a single arrow, but the opposite direction of the first direction D1 is also sometimes referred to as the first direction D1. The first direction D1 is the direction of movement of the upper punch 3 and the lower punch 4 relative to the die 2, and is the compression direction of the powder 9P.

[0029] One of the features of the mold 1 of this embodiment is that it is equipped with a first core 5 that divides the hollow portion 20 in the die 2 into a plurality of space portions 8. The plurality of space portions 8 are arranged in parallel in a direction perpendicular to the first direction D1. In this example, two space portions 8 are arranged side by side in the second direction D2. Multiple cavities 9 are formed corresponding to the plurality of space portions 8. Hereinafter, the direction perpendicular to both the first direction D1 and the second direction D2 may be referred to as the third direction D3. The mold 1 of this example further includes a second core 7.

[0030] Thailand As shown in Figure 2, die 2 is a cylindrical member having a hollow portion 20 that penetrates in a first direction D1. The hollow portion 20 has an end that opens upward and an end that opens downward. The hollow portion 20 is a space with both ends open. The shape of the hollow portion 20 corresponds to the outer shape of the powder molded body 10 that is compression molded. The inner surface 21 of die 2 that constitutes the hollow portion 20 is, for example, a smooth surface without irregularities. The opening edge of the hollow portion 20 as seen from the first direction D1 may be composed of a straight line or a curve. In this example, the opening edge is composed of, for example, a combination of multiple straight lines and curves. As shown in Figure 1, the shape of the opening edge in this example is generally rectangular and includes four straight lines and four curves. The four curves constitute corners connecting adjacent straight lines. The three-dimensional shape of the hollow portion 20 in this example is generally rectangular and includes four planes. The corners connecting the four planes are rounded.

[0031] Die 2 moves along the first direction D1 by a drive mechanism (not shown).

[0032] ≪Upper punch≫ The upper punch 3 is inserted into the upper part of the hollow section 20. Multiple upper punches 3 are provided, corresponding to the number of multiple space sections 8, which will be described later. In this example, as shown in Figure 3, the upper punches 3 consist of a first upper punch 31 and a second upper punch 32, corresponding to two space sections 8. Each of the first upper punch 31 and the second upper punch 32 is a columnar member. The outer shape of the end faces of the first upper punch 31 and the second upper punch 32 corresponds to the outer shape of the first end face 11 of the powder molded body 10 that is compression molded. The outer shape of the end faces of the first upper punch 31 and the second upper punch 32 in this example is substantially rectangular. The substantially rectangular shape includes shapes with chamfered corners or shapes with rounded corners, and is considered to be substantially rectangular.

[0033] When the powder 9P is compressed, a portion of the first core 5, which will be described later, is inserted between the first upper punch 31 and the second upper punch 32. The first upper punch 31 and the second upper punch 32 are positioned with a gap that allows a portion of the first core 5 to slide freely.

[0034] In this example, the first upper punch 31 and the second upper punch 32 are each provided with a through hole 34. A portion of the second core 7, which will be described later, is slidably inserted into the through hole 34.

[0035] Each of the first upper punch 31 and the second upper punch 32 slides along the first direction D1 relative to the die 2, the first core 5, and the second core 7.

[0036] The first upper punch 31 and the second upper punch 32 move along the first direction D1 by a drive mechanism (not shown). The first upper punch 31 and the second upper punch 32 may operate in conjunction with each other. For example, the first upper punch 31 and the second upper punch 32 may be connected at a point where they are not inserted into the die 2, and the first upper punch 31 and the second upper punch 32 may move simultaneously along the first direction D1 by the drive mechanism. The first upper punch 31 and the second upper punch 32 may operate independently of each other. For example, the drive mechanism may include a first drive mechanism that operates only the first upper punch 31 and a second drive mechanism that operates only the second upper punch 32. Even if the first upper punch 31 and the second upper punch 32 operate independently of each other, it is preferable that the compression by the first upper punch 31 and the compression by the second upper punch 32 be performed simultaneously. Simultaneous compression ensures that the powder in each cavity 9 is compressed evenly.

[0037] ≪Lower punch≫ The lower punch 4 is inserted into the lower part of the hollow section 20. Multiple lower punches 4 are provided, corresponding to the number of multiple space sections 8, which will be described later. In this example, as shown in Figure 3, the lower punches 4 consist of a first lower punch 41 and a second lower punch 42, corresponding to two space sections 8. The first upper punch 31 and the first lower punch 41 are paired. The second upper punch 32 and the second lower punch 42 are paired. Each of the first lower punch 41 and the second lower punch 42 is a columnar member. The outer shape of the end faces of the first lower punch 41 and the second lower punch 42 corresponds to the outer shape of the second end face of the powder molded body 10 that is compression molded. The second end face is the face facing the first end face 11 of the powder molded body 10 shown in Figure 4. The outer shape of the end faces of the first lower punch 41 and the second lower punch 42 in this example is substantially rectangular.

[0038] When the powder 9P is compressed, a portion of the first core 5, described later, is inserted between the first lower punch 41 and the second lower punch 42. The first lower punch 41 and the second lower punch 42 are positioned with a gap that allows a portion of the first core 5 to slide freely. In this example, the first core 5 is inserted into the hollow portion 20 from the same direction as the lower punch 4. Therefore, in this example, the first core 5 is always positioned between the first lower punch 41 and the second lower punch 42. In other words, the first lower punch 41 and the second lower punch 42 in this example sandwich the first core 5.

[0039] In this example, the first lower punch 41 and the second lower punch 42 are each provided with a through hole 44. A portion of the second core 7, which will be described later, is slidably inserted into the through hole 44. In this example, the second core 7 is inserted into the hollow portion 20 from the same direction as the lower punch 4. Therefore, in this example, the second core 7 is always located inside the through holes 44 of the first lower punch 41 and the second lower punch 42.

[0040] Each of the first lower punch 41 and the second lower punch 42 slides along the first direction D1 relative to the die 2, the first core 5, and the second core 7.

[0041] The lower punch 4 is normally fixed. The die 2, upper punch 3, and first core 5 move along the first direction D1 relative to the lower punch 4.

[0042] ≪First Core≫ The first core 5 is a columnar member that divides the hollow portion 20 into a plurality of space portions 8 arranged in parallel in a direction perpendicular to the first direction D1. The first core 5 is positioned to divide the hollow portion 20 into a plurality of space portions 8. In this example, the first core 5 is positioned to divide the hollow portion 20 into two space portions 8: a first space portion 81 and a second space portion 82. In this example, two cavities 9, a first cavity 91 and a second cavity 92, are formed corresponding to the number of space portions 8. The shape of the first core 5 is determined in accordance with the shape and number of powder molded bodies 10 that are compression molded. In this example, the shape of the first core 5 is substantially rectangular parallelepiped. The substantially rectangular parallelepiped shape includes a range that can be considered substantially rectangular parallelepiped, including shapes with chamfered corners or shapes with rounded corners. The first core 5 in this example comprises a side surface 51 facing the first space 81, a side surface 52 facing the second space 82, sliding surfaces 53, 53 facing the die 2, and an end surface 54. The first core 5 in this example has a substantially rectangular cross-sectional shape in which the length in the third direction D3 is longer than the length in the second direction D2.

[0043] The first core 5 includes a partial region 6 provided on the sides 51 and 52, as shown in Figures 2 and 3. The partial region 6 is located midway along the first direction D1 on the sides 51 and 52. The partial region 6 includes a projection that protrudes from the sides 51 and 52. The projection protrudes in the second direction D2. The shape of the projection is not limited. The projection has a curved, bulging cross-sectional shape, as shown in Figures 2 and 3, for example. More specifically, the projection in this example has an arc-shaped cross-sectional shape enclosed by a circular arc and a chord. The projection is provided in at least a part of the partial region 6. The projection may be provided in a part of the partial region 6, or it may be provided in the entire area of ​​the partial region 6. The partial region 6 may include a partial recess. In this example, the partial region 6 is a projection.

[0044] The partial region 6 provides the powder molded body 10, which is compression-molded, with an undercut portion 15 as shown in Figure 4. The undercut portion 15 has an undercut shape. The undercut shape includes a concave shape that is recessed in a second direction D2 perpendicular to the first direction D1. If the partial region 6 is a protrusion, the shape of the undercut portion 15 provided on the powder molded body 10 is concave. In Figure 1, for ease of explanation, the partial region 6 is shown with a dashed line.

[0045] The partial region 6 comprises a first partial region 61 provided on the side surface 51 and a second partial region 62 provided on the side surface 52. Both the first partial region 61 and the second partial region 62 are protrusions. In this example, the protrusions are provided to project in the second direction D2 and extend in the third direction D3. In this example, the protrusions have an arc-shaped cross-section and are columnar bodies extending along the third direction D3. The protrusions may also be provided to extend inclined in a direction intersecting the third direction D3. In this example, the shape of the first partial region 61 and the shape of the second partial region 62 are the same. In this example, the size of the first partial region 61 and the size of the second partial region 62 are the same. In this example, the first partial region 61 and the second partial region 62 are provided symmetrically. If the first partial region 61 and the second partial region 62 are the same in shape, size, and arrangement, multiple powder molded bodies 10 having the same undercut portion 15 can be manufactured simultaneously.

[0046] At least one partial region 6 is provided on each side 51, 52. As in this example, one partial region 6 may be provided on each side 51, 52. Multiple partial regions 6 may be provided on each side 51, 52, for example, by dividing them in a third direction D3.

[0047] The first partial region 61 provided on side surface 51 and the second partial region 62 provided on side surface 52 do not have to be exactly the same shape and size. If the first partial region 61 and the second partial region 62 are the same in shape, size and arrangement as the other, the powder 9P in each cavity 9 will be compressed evenly, enabling stable manufacturing.

[0048] As shown in Figure 4, the powder molded body 10 that is compression molded is given an undercut portion 15 in which the partial region 6 shown in Figures 2 and 3 is inverted.

[0049] The end face 54 is exposed to the outside and does not come into contact with other components of the die 1. The first core 5 in this example is inserted into the hollow portion 20 from the same direction as the lower punch 4. That is, the first core 5 in this example is inserted into the hollow portion 20 from below the die 2. The first core 5 in this example has a structure that allows it to be fitted into the hollow portion 20 together with the lower punch 4 from the same direction as the lower punch 4. The first core 5 moves along the first direction D1 by a drive mechanism (not shown). The first core 5 is positioned by, for example, a block (not shown).

[0050] ≪Second Core≫ The second core 7 is a columnar member inserted into each of the multiple spaces 8. The second core 7 is inserted into each space 8 from the same direction as the lower punch 4. In other words, the second core 7 is inserted into each space 8 from below the die 2. The second core 7 has a structure that allows it to be fitted into the hollow section 20 together with the lower punch 4 and the first core 5 from the same direction as the lower punch 4. The second core 7 is inserted into the through holes 44 of the first lower punch 41 and the second lower punch 42, respectively. The second core 7 forms through holes 16 in the powder molded body 10 that is compression molded. The shape of the second core 7 corresponds to the shape of the through holes 16 shown in Figure 4. In this example, the shape of the second core 7 is cylindrical.

[0051] ≪Multiple spatial areas≫ When the first core 5 is placed in the hollow portion 20 of the die 2, the hollow portion 20 is divided into multiple spaces 8 by the first core 5. In this example, the first core 5 forms two spaces 8: a first space 81 and a second space 82. In this example, the shape of the first space 81 and the shape of the second space 82 are the same. In this example, the size of the first space 81 and the size of the second space 82 are the same. The orientation of the first space 81 and the orientation of the second space 82 may be different. In this example, the orientation of the first space 81 and the orientation of the second space 82 are symmetrical with respect to the first core 5.

[0052] When the first lower punch 41 is placed in the first space 81, a first cavity 91 is formed in the first space 81. When the second lower punch 42 is placed in the second space 82, a second cavity 92 is formed in the second space 82. In this example, a second core 7 is further placed in each of the first space 81 and the second space 82. In this example, the first cavity 91 and the second cavity 92 have the same shape. In this example, the shapes of the first cavity 91 and the second cavity 92 are cylindrical. In the mold 1 of this example, two powder molded bodies 10 of the same shape and size can be molded simultaneously.

[0053] When two spaces 8, a first space 81 and a second space 82, are formed on either side of the first core 5, the direction of the lateral pressure from the powder 9P in each cavity 91, 92 becomes symmetrical with respect to the first core 5, and the lateral pressure cancels out. When the lateral pressure cancels out, even if the first core 5 and the die 2 move relative to each other, seizure is less likely to occur between the first core 5 and the die 2. Furthermore, if the direction of the lateral pressure is symmetrical, it is possible to manufacture two powder molded bodies 10 with small local variations in density. In particular, when spaces 8 of the same shape are formed on either side of the first core 5, two powder molded bodies 10 of the same shape can be molded simultaneously.

[0054] The number of spatial sections 8 may be three or more. Three or more spatial sections 8 may be arranged in parallel, for example, in the second direction D2. If the opening edge of the hollow section 20 as viewed from the first direction D1 is circular, the three or more spatial sections 8 may be arranged in parallel around the axis of the hollow section 20.

[0055] Multiple spatial sections 8 may include spatial sections 8 of different shapes. For example, the shape of the first spatial section 81 may be different from the shape of the second spatial section 82. Multiple spatial sections 8 may include spatial sections 8 of different sizes. For example, the size of the first spatial section 81 may be different from the size of the second spatial section 82.

[0056] <Powder molded body> The powder molded body 10 produced by the mold 1 described above includes an undercut portion 15, as shown in Figure 4. The undercut portion 15 is a recessed area indented from the side surface 13. The powder molded body 10 in this example further includes a through hole 16.

[0057] <Method for manufacturing powder-molded bodies> The method for manufacturing a powder molded body according to an embodiment will be described with reference to Figures 5 to 7. The method for manufacturing a powder molded body comprises a preparation step, a filling step, a molding step, and a removal step, which are performed in order.

[0058] ≪Preparation Steps≫ In the preparation step, the mold 1 described above is prepared. The shapes of the die 2, upper punch 3, lower punch 4, first core 5, and second core 7 in mold 1 can be appropriately selected so that multiple cavities 9 corresponding to the shape of the powder molded body 10 to be manufactured are formed.

[0059] ≪Filling process≫ In the filling process, as shown in Figure 5, with the lower punch 4 and the first core 5 inserted into the hollow section 20 shown in Figures 2 and 3, powder 9P is filled into each of the multiple spaces 8. The spaces 8 with the lower punch 4 and the first core 5 inserted into the hollow section 20 are cavities 9. In this example, a second core 7 is also inserted into the hollow section 20. The end face of the second core 7 is positioned above the end face of the lower punch 4. The end faces 54 of the first core 5 and the end faces of the second core 7 are, for example, coplanar with the end face of the die 2.

[0060] ≪Molding process≫ In the molding process, as shown in Figure 6, an upper punch 3 is inserted into each of the multiple spaces 8 shown in Figure 3, and the powder 9P is compressed by the upper punch 3 and the lower punch 4. In this example, the powder 9P in the first cavity 91 is compressed by the first upper punch 31 and the first lower punch 41, and the powder 9P in the second cavity 92 is compressed by the second upper punch 32 and the second lower punch 42. In this example, the first upper punch 31 and the second upper punch 32 are moved simultaneously downward along the first direction D1 by a drive mechanism (not shown). At this time, the end face 54 of the first core 5 is not in contact with the other components of the mold 1.

[0061] When powder 9P is compressed, the lateral pressure from powder 9P is applied to the inner surface 21 of die 2, the side surfaces 51 and 52 of the first core 5, and the outer circumferential surfaces of each second core 7. The above lateral pressure is not easily applied to the sliding surface 53 of the first core 5.

[0062] The powder 9P filled inside the first cavity 91 and the second cavity 92 is compressed, and two powder molded bodies 10 are formed simultaneously. If three or more spaces 8 are formed, a number of powder molded bodies 10 corresponding to the three or more spaces 8 are formed simultaneously.

[0063] ≪Removal Process≫ In the removal process, as shown in Figure 7, the die 2, upper punch 3, and second core 7 are moved relative to the lower punch 4. In other words, with the lower punch 4 and first core 5 fixed, the die 2, upper punch 3, and second core 7 are moved along the first direction D1.

[0064] As described above, the lateral pressure from the powder 9P in each cavity 9 is not easily applied to the sliding surface 53 of the first core 5. Therefore, even if the first core 5 and the die 2 move relative to each other, seizure is unlikely to occur between the first core 5 and the die 2. In this example, two powder molded bodies 10 are molded with the first core 5 in between. Therefore, the direction of the lateral pressure from the powder 9P is symmetrical with respect to the first core 5, and the lateral pressure cancels out. In this example, it is possible to manufacture two powder molded bodies 10 with small local variations in density.

[0065] The removal process positions each powder molded body 10 outside the hollow portion 20 of the die 2. Once outside the hollow portion 20, each powder molded body 10 has surfaces other than the contact surface with the first core 5 exposed. Each powder molded body 10, located outside the hollow portion 20, is movable away from the first core 5. Each powder molded body 10 can be removed by detaching it from the first core 5. In this example, two powder molded bodies 10 are moved away from each other along the second direction D2. This removal process allows for easy removal of the powder molded body 10 having the undercut portion 15 shown in Figure 4 from the mold 1. [Explanation of Symbols]

[0066] 1. Mold 2 die, 20 hollow section, 21 inner surface 3. Upper punch, 31. First upper punch, 32. Second upper punch 34 Through holes 4. Lower punch, 41. First lower punch, 42. Second lower punch 44 Through holes 5 First core, 51, 52 Side surfaces, 53 Sliding surface, 54 End surface 6 partial area, 61 first partial area, 62 second partial area 7 Second Core 8 space part, 81 first space part, 82 second space part 9 Cavity, 91 First Cavity, 92 Second Cavity 9P powder 10 Powder molded body 11 First end face, 13 Side surface, 15 Undercut portion, 16 Through hole D1 first direction, D2 second direction, D3 third direction

Claims

1. A mold for forming a powder molded body having an undercut shape, A die having a hollow portion penetrating in the first direction, A first core divides the hollow portion into a plurality of spatial portions arranged in parallel in a direction perpendicular to the first direction, It comprises an upper punch and a lower punch that are fitted into each of the aforementioned plurality of spaces, The first core comprises a partial region provided midway in the first direction on the side surface facing the plurality of spatial portions, The aforementioned partial region includes a projection that protrudes from the side in a direction intersecting the first direction, The aforementioned projection is It protrudes from both the upper and lower parts of the aforementioned projection, In a longitudinal section obtained by cutting the first core so as to include the protrusion along both the first direction and the direction in which the adjacent spaces are aligned, the cross-sectional shape is curved and bulging. Mold.

2. The mold according to claim 1, wherein the plurality of spaces are two.

3. The hollow portion comprises a first space and a second space, which are divided by the first core. The first core comprises a first surface facing the first space and a second surface facing the second space, The mold according to claim 2, wherein the first partial region provided on the first side surface and the second partial region provided on the second side surface have the same shape of projection.

4. The mold according to claim 1 or claim 2, wherein all of the aforementioned multiple spaces have the same shape.

5. The mold according to claim 1 or claim 2, wherein the first core is inserted into the hollow portion from the same direction as the lower punch.

6. The mold according to claim 1 or claim 2, further comprising a second core inserted into each of the plurality of spaces.

7. The mold according to claim 1 or claim 2, wherein the aforementioned partial region is the protrusion.

8. A step of preparing the mold according to claim 1 or claim 2, With the lower punch and the first core inserted into the hollow portion, the process involves filling each of the plurality of spaces with powder. A step of inserting the upper punch into each of the plurality of spaces, and compressing the powder with the upper punch and the lower punch to form a powder molded body, The process includes moving the die and the upper punch relative to the lower punch to remove the powder molded body. A method for manufacturing a powder-molded body.

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