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

Mold and method for manufacturing powder compact

[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 by reference all of the contents of the above-mentioned Japanese application.

[0002] Patent Document 1 discloses a mold for producing a molded body having an undercut shape. The 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 that imparts the undercut shape to the molded body. The second die is inserted into the through hole of the first die so that its outer surface contacts the inner surface of the through hole. The molded body is molded by compressing powder within a cavity surrounded by the inner surface of the through hole, the second die, the first punch, and the second punch.

[0003] JP 2017-159360 A

[0004] The mold 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 space portions 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 space portions, wherein the first core has a partial region provided midway in 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.

[0005] FIG. 1 is a cross-sectional view of a mold according to an embodiment. FIG. 2 is a longitudinal cross-sectional view of the mold according to an embodiment, in which an upper punch, a lower punch, a first core, and a second core are not inserted into the die. FIG. 3 is a longitudinal cross-sectional view of the mold according to an embodiment, in which a lower punch, a first core, and a second core are inserted into the die, and the upper punch is not inserted into the die. FIG. 4 is a perspective view of a powder compact molded using the mold according to an embodiment. FIG. 5 is an explanatory diagram of a powder filling step in a method for manufacturing a powder compact using the mold according to an embodiment. FIG. 6 is an explanatory diagram of a powder compact molding step in a method for manufacturing a powder compact using the mold according to an embodiment. FIG. 7 is an explanatory diagram of a powder compact removal step in a method for manufacturing a powder compact using the mold according to an embodiment.

[0006] [Problem to be Solved by the Present Disclosure] The mold disclosed in Patent Document 1 has one 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 are moved relative to each other, the lateral pressure may cause seizure between the first die and the second die.

[0007] An object of the present disclosure is to provide a mold that can suppress seizure between components of the mold when compressing powder.

[0008] [Effects of the Present Disclosure] The mold of the present disclosure can suppress seizure between the components of the mold when compressing powder.

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

[0010] (1) A mold according to an 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 space portions 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 space portions, wherein the first core comprises a partial region provided midway in 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.

[0011] Although the first core is referred to as a core in the disclosure of this specification, it may be constituted by a member generally called a punch depending on the configuration of the mold. The first core may be called by any name as long as it is a member that serves to divide the hollow portion into a plurality of space portions.

[0012] The die of the present disclosure has multiple spaces, allowing multiple powder compacts to be produced in a single compression run. Each space faces a partial region. Therefore, the die of the present disclosure can efficiently produce powder compacts having an undercut shape.

[0013] In the mold of the present disclosure, multiple spaces are formed on either side of the first core, and when the powder filled in each space is compressed, the lateral pressure acting on the inner peripheral surface of the die is more likely to act on the surface in contact with the powder than on the surface in contact with the first core, so that 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.

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

[0015] When two spaces are formed on either side of the first core, the direction of lateral pressure from the powder tends to be symmetrical with respect to the first core, and excessive lateral pressure is less likely to act locally. Symmetrical lateral pressure directions make it possible to produce two powder compacts with small local variations in density. A first core that divides the hollow space into two spaces has a simpler configuration than a first core that divides the hollow space into three or more spaces.

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

[0017] If all of the multiple spaces have the same shape, multiple powder compacts of the same shape can be molded simultaneously. When spaces of the same shape are formed on either side of the first core, the direction of lateral pressure from the powder tends to be symmetrical with respect to the first core. When spaces of the same shape are formed on either side of the first core, powder compression in the multiple spaces is uniform, allowing for stable production.

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

[0019] The procedure for manufacturing the powder compact is as follows: first, a lower punch and a first core are inserted into the hollow portions, and powder is filled into each of the multiple spaces. Then, an upper punch is inserted into each of the multiple spaces, 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 portions from the same direction, it is easy to form spaces into which the powder can be filled.

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

[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 any of the molds described in (1) to (5) above, the partial region may be the protrusion.

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

[0024] (7) A method for manufacturing a powder compact according to an embodiment of the present disclosure includes the steps of preparing a mold according to any one of (1) to (6) above, filling each of the plurality of spaces with powder while inserting the lower punch and the first core into the hollow portion, 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 compact, and moving the die and the upper punch relative to the lower punch and removing the powder compact.

[0025] In the method for producing a powder compact according to the present disclosure, since the die according to the present disclosure is used, it is possible to efficiently produce multiple powder compacts having an undercut shape by a single compression. In the method for producing a powder compact according to the present disclosure, since the die according to the present disclosure is used, even if the first core and the die move relative to each other, seizure is unlikely to occur between the first core and the die.

[0026] [Details of the embodiments of the present disclosure] Specific examples of the mold of the present disclosure and the method for manufacturing a powder compact using the mold of the present disclosure will be described with reference to the drawings. The same reference numerals in the figures indicate the same or equivalent parts. In each drawing, for the convenience of explanation, some of the configuration may be exaggerated or simplified. The dimensional ratios of each part in the drawings may also differ from the actual ratios. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0027] <Mold> A mold 1 according to an embodiment will be described with reference to FIGS. 1 to 3. The mold 1 includes a die 2, an upper punch 3, and a lower punch 4. The die 2 and the lower punch 4 define a cavity 9. The cavity 9 is filled with a powder 9P, as shown in FIG. 5. The powder compact 10 shown in FIGS. 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. FIG. 1 shows the mold 1, with the components of the mold 1 assembled, cut along a plane perpendicular to the first direction D1 so as to include the upper punch 3. FIG. 2 shows the mold 1 cut along a plane along the first direction D1 before the cavity 9 is formed. FIG. 3 shows the mold 1 cut along a plane along the first direction D1 after the cavity 9 is formed. In FIG. 3, the upper punch 3 is positioned above the cavity 9.

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

[0029] One of the features of the mold 1 of this embodiment is that it includes a first core 5 that divides the hollow portion 20 in the die 2 into multiple spaces 8. The multiple spaces 8 are arranged in parallel in a direction perpendicular to the first direction D1. In this example, two spaces 8 are arranged side by side in the second direction D2. Multiple cavities 9 are formed corresponding to the multiple spaces 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] <Die> As shown in FIG. 2 , the die 2 is a cylindrical member having a hollow portion 20 penetrating 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 compact 10 to be compression-molded. The inner surface 21 of the die 2 that forms the hollow portion 20 is, for example, a smooth surface without irregularities. The opening edge of the hollow portion 20 as viewed from the first direction D1 may be formed by straight lines or curved lines. In this example, the opening edge is formed by, for example, a combination of multiple straight lines and curved lines. In this example, the shape of the opening edge is generally rectangular as shown in FIG. 1 and includes four straight lines and four curved lines. The four curved lines form corners connecting adjacent straight lines. In this example, the three-dimensional shape of the hollow portion 20 is generally rectangular and includes four flat surfaces. The corners connecting the four flat surfaces are rounded.

[0031] The die 2 is moved along a first direction D1 by a driving mechanism (not shown).

[0032] <<Upper Punch>> The upper punch 3 is inserted into the upper part of the hollow portion 20. A plurality of upper punches 3 are provided corresponding to the number of the plurality of spaces 8 described below. As shown in FIG. 3 , the upper punch 3 in this example includes a first upper punch 31 and a second upper punch 32 corresponding to the two spaces 8. Each of the first upper punch 31 and the second upper punch 32 is a columnar member. The outer shape of each end face 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 compact 10 to be compression-molded. The outer shape of each end face of the first upper punch 31 and the second upper punch 32 in this example is substantially rectangular. The term "substantially rectangular" includes a shape with chamfered corners or a shape with rounded corners, and encompasses a range that is considered to be substantially rectangular.

[0033] When compressing the powder 9P, a part of a 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 arranged with a gap therebetween that allows a part of the first core 5 to slide freely.

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

[0035] The first upper punch 31 and the second upper punch 32 each slide relative to the die 2, the first core 5, and the second core 7 along a first direction D1.

[0036] The first upper punch 31 and the second upper punch 32 are moved along the first direction D1 by a drive mechanism (not shown). The first upper punch 31 and the second upper punch 32 may be operated in conjunction with each other. For example, the first upper punch 31 and the second upper punch 32 may be connected at a location that is not inserted into the die 2, and the first upper punch 31 and the second upper punch 32 may be simultaneously moved along the first direction D1 by the drive mechanism. The first upper punch 31 and the second upper punch 32 may also be operated 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 are operated independently of each other, compression by the first upper punch 31 and compression by the second upper punch 32 may be performed simultaneously. Simultaneous compression ensures uniform compression of the powder in each cavity 9.

[0037] <Lower Punch> The lower punch 4 is inserted into the lower part of the hollow portion 20. A plurality of lower punches 4 are provided corresponding to the number of spaces 8 described below. As shown in FIG. 3 , the lower punch 4 in this example includes a first lower punch 41 and a second lower punch 42, each corresponding to two spaces 8. The first upper punch 31 and the first lower punch 41 form a pair. The second upper punch 32 and the second lower punch 42 form a pair. Each of the first lower punch 41 and the second lower punch 42 is a columnar member. The outer shape of each end face 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 compact 10 to be compression-molded. The second end face is the surface facing the first end face 11 of the powder compact 10 shown in FIG. 4 . The outer shape of each end face of the first lower punch 41 and the second lower punch 42 in this example is substantially rectangular.

[0038] When compressing the powder 9P, a portion of a first core 5, which will be 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 arranged with a gap therebetween that allows a portion of the first core 5 to slide freely. The first core 5 in this example is inserted into the hollow portion 20 from the same direction as the lower punch 4. Therefore, the first core 5 in this example is always arranged between the first lower punch 41 and the second lower punch 42. In other words, the first core 5 is sandwiched between the first lower punch 41 and the second lower punch 42 in this example.

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

[0040] The first lower punch 41 and the second lower punch 42 each slide relative to the die 2, the first core 5, and the second core 7 along a first direction D1.

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

[0042] <First Core> The first core 5 is a columnar member that divides the hollow portion 20 into a plurality of spaces 8 arranged in a direction perpendicular to the first direction D1. The first core 5 is disposed at a position that divides the hollow portion 20 into a plurality of spaces 8. In this example, the first core 5 is disposed at a position that divides the hollow portion 20 into two spaces 8, a first space 81 and a second space 82. In this example, two cavities 9, a first cavity 91 and a second cavity 92, are formed corresponding to the number of spaces 8. The shape of the first core 5 is determined according to the shape and number of the powder compacts 10 to be compression-molded. The shape of the first core 5 in this example is a substantially rectangular parallelepiped. The substantially rectangular parallelepiped shape includes a shape with chamfered corners or a shape with rounded corners, and includes a range that can be considered substantially a rectangular parallelepiped. The first core 5 of this example has 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 of this example has a substantially rectangular cross-sectional shape whose length in the third direction D3 is longer than its length in the second direction D2.

[0043] As shown in FIGS. 2 and 3 , the first core 5 includes partial regions 6 provided on the side surfaces 51 and 52. The partial regions 6 are provided midway along the side surfaces 51 and 52 in the first direction D1. The partial regions 6 include protrusions protruding from the side surfaces 51 and 52. The protrusions protrude in the second direction D2. The shape of the protrusions is not important. For example, as shown in FIGS. 2 and 3 , the protrusions have a curved, bulging cross-sectional shape. More specifically, the protrusions in this example have an arched cross-sectional shape surrounded by a circular arc and a chord. The protrusions are provided on at least a portion of the partial regions 6. The protrusions may be provided on a portion of the partial regions 6 or may be provided over the entire area of ​​the partial regions 6. The partial regions 6 may include partial recesses. The partial regions 6 in this example are protrusions.

[0044] The partial region 6 provides the powder compact 10 with an undercut portion 15 shown in FIG. 4 after compression molding. The undercut portion 15 has an undercut shape. The undercut shape includes a concave shape recessed in a second direction D2 perpendicular to the first direction D1. When the partial region 6 is a protrusion, the shape of the undercut portion 15 provided in the powder compact 10 is a concave shape. For ease of explanation, the partial region 6 is shown by a dashed line in FIG. 1 .

[0045] The partial region 6 includes 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 so as to protrude in the second direction D2 and extend in the third direction D3. In this example, the protrusions are columnar bodies having an arched cross-sectional shape and extending along the third direction D3. The protrusions may be provided so as to extend at an angle 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. When the first partial region 61 and the second partial region 62 have the same shape, size, and arrangement, multiple powder molded bodies 10 having the same undercut portion 15 can be simultaneously manufactured.

[0046] At least one partial region 6 is provided on each of the side surfaces 51 and 52. As in this example, one partial region 6 may be provided on each of the side surfaces 51 and 52. A plurality of partial regions 6 may be provided on each of the side surfaces 51 and 52, for example, divided in the third direction D3.

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

[0048] As shown in FIG. 4, the powder compact 10 that is compression-molded is provided with an undercut portion 15 that is an inverted version of the partial region 6 shown in FIGS.

[0049] The end surface 54 is exposed to the outside and does not contact other components of the mold 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, for example, by a block (not shown).

[0050] <<Second Core>> The second core 7 is a columnar member inserted into each of the plurality of spaces 8. The second core 7 is inserted into each space 8 from the same direction as the lower punch 4. That is, the second core 7 is inserted into each space 8 from below the die 2. The second core 7 has a structure in which it is fitted into the hollow portion 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 each through hole 44 of the first lower punch 41 and the second lower punch 42. The second core 7 forms a through hole 16 in the powder compact 10 to be compression-molded. The shape of the second core 7 corresponds to the shape of the through hole 16 shown in FIG. 4 . The shape of the second core 7 in this example is cylindrical.

[0051] <<Multiple Spaces>> 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 first cavity 91 and the second cavity 92 each have a cylindrical shape. With 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, the first space 81 and the second space 82, are formed on either side of the first core 5, the direction of lateral pressure from the powder 9P in each cavity 91, 92 becomes symmetrical with respect to the first core 5, and the lateral pressure is canceled out. When the lateral pressure is canceled out, seizure is less likely to occur between the first core 5 and the die 2 even if the first core 5 and the die 2 move relative to each other. Furthermore, if the direction of the lateral pressure is symmetrical, two powder compacts 10 with small local variations in density can be manufactured. In particular, when spaces 8 of the same shape are formed on either side of the first core 5, two powder compacts 10 of the same shape can be molded simultaneously.

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

[0055] The plurality of spaces 8 may include spaces 8 of different shapes. For example, the shape of the first space 81 may be different from the shape of the second space 82. The plurality of spaces 8 may include spaces 8 of different sizes. For example, the size of the first space 81 may be different from the size of the second space 82.

[0056] <Powder Molded Body> As shown in Fig. 4, the powder molded body 10 manufactured by the above-described die 1 has an undercut portion 15. The undercut portion 15 is a recess recessed from the side surface 13. The powder molded body 10 of this example further has a through hole 16.

[0057] <Method for Manufacturing Powder Compact> A method for manufacturing a powder compact according to an embodiment will be described with reference to Figures 5 to 7. The method for manufacturing a powder compact includes a preparation step, a filling step, a molding step, and a removal step, which are performed in this order.

[0058] <Preparation Step> In the preparation step, the above-described mold 1 is prepared. The shapes of the die 2, upper punch 3, lower punch 4, first core 5, and second core 7 in the mold 1 can be appropriately selected so as to form a plurality of cavities 9 corresponding to the shape of the powder molded body 10 to be manufactured.

[0059] <Filling Process> In the filling process, as shown in Fig. 5, with the lower punch 4 and first core 5 inserted into the hollow portion 20 shown in Figs. 2 and 3, each of the plurality of spaces 8 is filled with powder 9P. The spaces 8 with the lower punch 4 and first core 5 inserted into the hollow portion 20 form cavities 9. In this example, a second core 7 is also inserted into the hollow portion 20. An end face of the second core 7 is positioned higher than an end face of the lower punch 4. An end face 54 of the first core 5 and each end face of the second core 7 are flush with, for example, an end face of the die 2.

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

[0061] When the powder 9P is compressed, lateral pressure from the powder 9P is applied to the inner surface 21 of the die 2, the side surfaces 51 and 52 of the first core 5, and the outer peripheral surfaces of each second core 7. The lateral pressure is less likely to be applied to the sliding surface 53 of the first core 5.

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

[0063] 7 , in the removal process, the die 2, the upper punch 3, and the second core 7 are moved relative to the lower punch 4. That is, with the lower punch 4 and the first core 5 fixed, the die 2, the upper punch 3, and the 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 unlikely to be 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 compacts 10 are molded with the first core 5 sandwiched between them. Therefore, the direction of the lateral pressure from the powder 9P is symmetrical with respect to the first core 5, and the lateral pressures are canceled out. In this example, two powder compacts 10 with small local variations in density can be manufactured.

[0065] The removal step positions each powder compact 10 outside the hollow portion 20 of the die 2. The surfaces of each powder compact 10 outside the hollow portion 20 are exposed except for the surface in contact with the first core 5. Each powder compact 10 outside the hollow portion 20 can be moved away from the first core 5. Each powder compact 10 can be removed by peeling it off the first core 5. In this example, two powder compacts 10 are moved away from each other along the second direction D2. This removal step allows the powder compact 10 having the undercut portion 15 shown in FIG. 4 to be easily removed from the die 1.

[0066] DESCRIPTION OF SYMBOLS 1 Mold 2 Die 20 Hollow portion 21 Inner surface 3 Upper punch 31 First upper punch 32 Second upper punch 34 Through hole 4 Lower punch 41 First lower punch 42 Second lower punch 44 Through hole 5 First core 51, 52 Side surface 53 Sliding surface 54 End surface 6 Partial region 61 First partial region 62 Second partial region 7 Second core 8 Space portion 81 First space portion 82 Second space portion 9 Cavity 91 First cavity 92 Second cavity 9P Powder 10 Powder compact 11 First end surface 13 Side surface 15 Undercut portion 16 Through hole D1 First direction D2 Second direction D3 Third direction

Claims

1. A die having a hollow portion extending therethrough in a first direction; a first core that divides the hollow portion into a plurality of space portions that are arranged in parallel in a direction perpendicular to the first direction; an upper punch and a lower punch fitted into each of the plurality of spaces, the first core includes a partial region provided midway in the first direction on a side surface facing the plurality of spaces, The partial region includes a protrusion protruding from the side surface. Mold.

2. The mold according to claim 1 , wherein the number of said spaces is two.

3. A mold as described in claim 1, wherein the protrusion has a curved, bulging cross-sectional shape in a longitudinal section obtained by cutting the first core along both the first direction and the direction in which adjacent spatial portions are aligned to include the protrusion.

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

5. The mold according to claim 1 or 2, wherein all of the plurality of spaces have the same shape.

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

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

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

9. A step of preparing a mold according to claim 1 or claim 2; filling each of the plurality of spaces with powder while the lower punch and the first core are inserted into the hollow portions; 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 compact; and moving the die and the upper punch relative to the lower punch to remove the powder compact. A method for producing a powder compact.