Molding die and molding method

The molding die of the invention includes: a first die having a through-hole; a second die inserted into the through-hole and capable of moving relative to the first die; and a first punch and a second punch each insertable into the through-hole. A cavity surrounded by the second die, the first punch, and the second punch to compression-mold a molding object is formed in the through-hole. An undercut molding part is formed in the surface of the second die facing the cavity. The second die is formed so as to be splittable into two or more split bodies.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a U.S. National Phase application under 35 U.S.C. § 371 of International Patent Application No. PCT/JP2017/029386, filed Aug. 15, 2017, and claims the benefit of Japanese Patent Application No. 2016-160554, filed on Aug. 18, 2016, all of which are incorporated herein by reference in their entirety. The International Application was published in Japanese on Feb. 22, 2018 as International Publication No. WO/2018/034288 under PCT Article 21(2).

FIELD OF THE INVENTION

The present invention relates to a molding die, and a molding method using the same.

BACKGROUND OF THE INVENTION

For example, a method of manufacturing high-accuracy components or the like is known (for example, refer to: Japanese Unexamined Publication No. 2009-68558), and the method includes: performing die molding by using a powder material such as metal powder, ceramic powder, and the like as a molding object; and sintering the obtained green compact (molded body) at a high temperature. Generally, the powder molding die consists of a die in which a through-hole is formed between two facing openings, and an upper punch and a lower punch that are respectively inserted into the cavity from one opening and the other opening of the die.

In the power molding die having such a configuration, for example, raw material powder is filled into the cavity in a state where the lower punch is fitted into the cavity from the opening on the other side (lower side) of the die. Next, inserting the upper punch is inserted into the cavity from the opening on one side (upper side) of the die and the raw material powder is pressed into the cavity between the upper punch and the lower punch; and thereby, a green compact that imitates the shape of the cavity is formed. Next, one punch is separated from any opening of the die, and then the other punch pushes out the green compact molded within the cavity. Accordingly, the green compact can be extracted (released) from the inside of the cavity.

Meanwhile, in the case where a molded body including an undercut shape, such as a projection or a groove, which extends in a direction intersecting an insertion/removal direction of the upper punch and the lower punch, is molded as a green compact (molded body), a molding method of inserting a splittable second die into the through-hole of the die to perform molding is known.

For example, in the powder molding method disclosed in Japanese Unexamined Publication No. H01-100206, a swelling part (undercut shape) is formed within the through-hole of the outer mold (die), and the coupling die (second die) splittable into two split bodies is inserted into the through-hole.

Next, the powder filled into the cavity of the coupling die is compressed with the upper punch and the lower punch to form a green compact, and then the coupling die is extracted from the die, and the coupling die is split; and thereby, a green compact including the undercut shape is obtained.

Problems to be Solved by the Invention

However, in the powder molding method described in Japanese Unexamined Publication No. H01-100206, a structure is adopted in which the coupling die is inserted into the through-hole of the outer die (die), and then, the upper punch is inserted into the coupling die to compress the molding object. Therefore, the molding position of the undercut shape part in the obtained molded body is likely to deviate, that is, the coupling die is inserted into the through-hole of the outer die (die), and the molding object is introduced into the cavity of the coupling die, and then, the upper punch is inserted into the cavity and compressed. Therefore, in the case of the molding object with a high compression rate, there is a problem that the upper punch enters the cavity more deeply and the molding position of the undercut shape part in a height direction of the molded body is likely to deviate.

The invention has been made in view of the above-described circumstances, and an object thereof is to provide a molding die capable of molding an undercut shape part without any positional deviation and with high accuracy, and a molding method using this molding die.

SUMMARY OF THE INVENTION

Solutions for Solving the Problems

A molding die that is an aspect of the invention has the following configuration.

A molding die includes: a first die having a through-hole; a second die inserted into the through-hole and capable of moving relative to the first die; and a first punch and a second punch each insertable into the through-hole. A cavity surrounded by the second die, the first punch, and the second punch to compression-mold a molding object is formed in the through-hole. An undercut molding part is formed in the surface of the second die facing the cavity. The second die is formed so as to be splittable into two or more split bodies.

According to the molding die that is the aspect of the invention, the molding die has a structure in which the molding object is introduced into the through-hole of the first die in advance and then, the second die is insertable into the through-hole of the first die in a state where the second die is attached to the first punch. Thus, it is possible to realize the molding die capable of molding the undercut shape part in the molded body without any positional deviation and with high accuracy irrespective of the compression rate of the molding object.

The molding die that is the aspect of the invention further includes a third punch outside the second punch, and the third punch is movable relative to the second punch and is insertable into and removable from the through-hole so as to be in contact with the second die at a tip thereof and in contact with an inner surface of the through-hole, outside the second punch.

The molding die that is the aspect of the invention further includes a core rod insertable into the cavity.

In the molding die of the invention, the molding object is powder.

A molding method that is another aspect of the invention has the following configuration.

A molding method using the molding die as described above is provided. The molding method includes at least an introduction step of introducing the molding object into the through-hole in a state where the second punch is inserted in an insertion/removal direction from one side of the through-hole; an insertion step of simultaneously inserting the first punch and the second die from the other side of the through-hole; a compression step of bringing the first punch and the second punch close to each other to compression-mold the molding object within the cavity to mold a molded body; and an extraction step of extracting the molded body from the molding die.

According to the molding method that is the aspect of the invention, the molding object is introduced into the through-hole of the first die in advance and then, the second die is inserted into the through-hole of the first die to compress the molding object in a state where the second die is attached to the first punch. Thereby, it is possible to realize the molding method capable of molding the undercut shape part in the molded body without any positional deviation and with high accuracy irrespective of the compression rate of the molding object.

In the molding method that is the aspect of the invention, the extraction step is a step of pulling out the first punch, the second die, and the molded body from the through-hole, and then splitting the second die in a direction intersecting the insertion/removal direction to remove the molded body from the second die.

Effects of the Invention

According to the invention, it is possible to provide a molding die capable of molding the undercut shape part in the molded body without any positional deviation and with high accuracy, and a molding method using this molding die.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a molding die and a molding method, which are embodiments to which the invention is applied, will be described with reference to the drawings. In addition, an embodiment shown below will be specifically described in order to make the purpose of the invention better understood, and does not limit the invention unless otherwise specified. Additionally, in the drawings to be used in the following description, major portions may be shown in an enlarged manner for convenience in order to make the features of the invention easily understood, and the dimension scales or the like of respective constituent elements are not necessarily the same as actual dimension scales.

FIG. 1is a side sectional view in an insertion/removal direction (compression direction) of the molding die related to the embodiment of the invention. Additionally,FIG. 2is a sectional view as seen from line A-A′ ofFIG. 3. In addition, in the following description, the insertion/removal direction Y indicates a compression direction with respect to a cavity P obtained by a second die12, a first punch13, and a second punch14to be described below.

A molding die10of the present embodiment is, for example, a die for forming a green compact which is an example of a molded body through compression molding using powder as an example of a molding object.

The molding die10includes a first die11, the second die12that is insertable and removable from the first die11, the first punch13, the second punch14, a third punch15, and a core rod16.

The first die11has, for example, an outer shape of a substantially cylindrical shape, and has a through-hole22penetrating between one opening11aand the other opening11bformed therein. In the present embodiment, the through-hole22forms a rectangular parallelepiped space surrounded by four inner surfaces22ato22d.

The second die12is a hollow angular tubular member that is formed so as to be insertable into and removable from the through-hole22of the first die11and has an outer shape of substantially rectangular parallelepiped shape. An outer surface12aof the second die12is brought into close contact with the inner surfaces22ato22dwhich form the through-hole22of the first die11during molding. The second die12includes second-die split bodies12A and12B that are two split bodies capable of being split from each other. Contact portions of the second-die split bodies12A and12B are brought into close contact with each other without a gap by combining the second-die split bodies12A and12B with each other and inserting the second-die split bodies12A and12B into the through-hole22of the first die11. In the present embodiment, the second die12includes the second-die split bodies12A and12B that faces each other and have a U-shaped cross-section.

An undercut molding part32including an alternate projection and depression31extending in a direction intersecting the insertion/removal direction Y is formed in an inner wall surface12bof the second die12that constitutes the cavity P. In the present embodiment, a projection, which protrudes toward a central direction of the cavity P and a trapezoidal cross-section, is formed as the alternate projection and depression31so as to surround four inner wall surfaces12bof the second die12. This undercut molding part32gives an undercut shape to the green compact in the molding method to be described below.

In addition, the alternate projection and depression31extending in the direction intersecting the insertion/removal direction Y means a shape portion that protrudes or is indented in a direction having an angle with respect to the insertion/removal direction Y, and the number of these alternate projections and depressions, the shapes, combinations, and arrangements of the respective alternate projections and depressions are not limited.

The first punch13is a quadrangular prismatic member that is formed so as to be insertable into and removable from the second die12and has a rectangular cross-section. A pressing surface13aof the first punch13compresses the molding object in the insertion/removal direction Y from one opening11aside of the first die11during molding. A through-hole13bhaving a round cross-section is formed at a cross-sectional center portion in this first punch13. The core rod16to be described below is made to be insertable into and removable from the through-hole13b. During molding, the first punch13is inserted in the through-hole22of the first die11in a state where the first punch13is immovable with respect to the inner wall surface12bof the second die12. Thereby, the first punch and the second die can be inserted into the through-hole22of the first die11while keeping the distance from the pressing surface13aof the first punch13to the undercut molding part32constant, and the undercut shape part32can be molded in the molded body without any positional deviation and with high accuracy.

The second punch14is a quadrangular prismatic member that is formed so as to be insertable into and removable from a hollow portion of the third punch15to be described below and has a rectangular cross-section. A pressing surface14aof the second punch14compresses the molding object in the insertion/removal direction Y from the other opening11bside of the first die11during molding.

A through-hole14bhaving a round cross-section is formed at a cross-sectional center portion in this second punch14. The through-hole14bis coaxially formed with the same diameter as that of the through-hole13bof the first punch13, and a portion of the core rod16to be described below is made to be insertable into and removable from the through-hole14b.

The third punch15is a hollow angular tubular member that is formed so as to be insertable into and removable from the through-hole22of the first die11and has an outer shape of a substantially rectangular parallelepiped shape. An outer surface15aof the third punch15is in contact with the inner surfaces22ato22dwhich forms the through-hole22of the first die11during molding. A tip15bof the third punch15is in contact with a lower end of the second die12in a state where the third punch15is inserted into the through-hole22of the first die11. Thereby, the second die12can be, for example, raised by moving the third punch15with respect to the first die11. Additionally, the second punch14mentioned above is made to be insertable into and removable from a hollow portion of the third punch15.

The core rod16is, for example, a cylindrical rod-like member, and is insertably and removably disposed so as to pass through the cavity P from the through-hole14bof the second punch14toward the through-hole13bof the first punch13. This core rod16forms a through-hole having a round cross-section in the green compact molded within the cavity P.

FIG. 3is a side sectional view of the molding die shown inFIG. 1during molding. Additionally,FIG. 4is an enlarged sectional view of main parts showing the cavity P ofFIG. 3and its peripheral portion.

During molding of the molding object, the cavity P surrounded by the second die12, the first punch13, and the second punch14is formed within the through-hole22of the first die11. More specifically, the cavity P is a molding space that is surrounded by the inner wall surface12bof the second die12, the pressing surface13aof the first punch13, and the pressing surface14aof the second punch14and has a substantially rectangular parallelepiped shape.

The second die12covers the inner surfaces22ato22dthat form the through-hole22of the first die11. Accordingly, the inner surfaces22ato22dthat form the through-hole22are not exposed to the cavity P. The undercut molding part32is formed in the inner wall surface12bof the second die12that faces the cavity P. Additionally, the core rod16passes through a central portion of the cavity P in the insertion/removal direction Y.

In such a molding die10, during molding, the cavity P is filled with powder W that is the molding object, the first punch13is moved toward the second punch14by a pressing mechanism40including a hydraulic device and the like, the height in the insertion/removal direction Y of the cavity P is reduced, the powder W that is the molding object is compressed, and the green compact that imitates the shape of the cavity P is molded.

FIG. 5is an external perspective view showing an example of the green compact (molded body) formed using the molding die10having such a configuration. The green compact50has a substantially rectangular parallelepiped shape, and the center thereof is provided with a through-hole51that is molded by the core rod16(refer toFIGS. 1 and 2) and has a round cross-section. Additionally, a groove (undercut shape part)52, which is molded by the alternate projection and depression31(refer toFIGS. 1 and 2) forming the undercut molding part32and has a substantially trapezoidal cross-section, is formed over the entire circumference of four side surfaces53of the green compact50on one surface of the green compact50. This groove52is an undercut shape part extending in the direction intersecting the insertion/removal direction Y during molding of the green compact50.

The molding method of the invention using the molding die having the above configurations will be described.FIG. 6A,FIG. 6B,FIG. 6C,FIG. 7A, andFIG. 7Bare side sectional views showing the molding method of the invention step by step. In addition, top sectional views of the molding die as seen from above are also shown at upper parts ofFIG. 7AandFIG. 7B.

For example, in the case where the green compact50having the groove52that is the undercut shape part is molded at the entire circumference of a side surface as shown inFIG. 5by the molding method of the invention, first, as shown inFIG. 6A, the third punch15is inserted into the through-hole22from the other opening11bof the first die11, and the second punch14is further inserted into the hollow portion of the third punch15. At this time, the pressing surface14aof the second punch14is at a position lower than the tip15bof the third punch15in the insertion/removal direction Y. Additionally, the core rod16is inserted into the through-hole14bof the second punch14.

Next, the powder W that is an example of the molding object is introduced into the through-hole22of the first die11(into the third punch15inserted into the through-hole22). The powder W is introduced into the hollow portion of the third punch15before molding. Examples of the powder W to be introduced includes iron powder and copper power including metals as main components, mixed powder thereof, and the like.

Next, as shown inFIG. 6B, the pressing mechanism40(refer toFIG. 3) is actuated to lower the first punch13where the first punch13is fitted into the second die12, and the first punch13and the second die12are simultaneously inserted into the through-hole22from the opening11aof the first die11. Accordingly, the powder W is filled into the cavity P surrounded by the inner wall surface12bof the second die12, the pressing surface13aof the first punch13, and the pressing surface14aof the second punch14(molding object filling step). Additionally, the second-die split body12A and the second-die split body12B that constitute the second die12are combined with each other and the combined second-die split bodies are inserted into the through-hole22of the first die11; and thereby, split portions of the second-die split body12A and the second-die split body12B are brought into close contact with each other without a gap.

The first punch13is further lowered toward the second punch14by the pressing mechanism40(refer toFIG. 3), and a gap between the pressing surface13aof the first punch13and the pressing surfaces14aof the second punch14is narrowed to compress the powder W (compression step). Through the compression step, the powder W is compressed within the cavity P, and the green compact (molded body)50including the groove52(refer toFIG. 5) that forms the undercut shape part imitating the internal shape of the cavity P, and the through-hole51(refer toFIG. 5) that imitates the core rod16is compression-molded.

When the powder W is compressed, the compressed powder is pressed against the undercut molding part32(refer toFIG. 4) of the second die12, and the alternate projection and depression31(refer toFIG. 4) extending in the direction intersecting the insertion/removal direction Y and having a trapezoidal cross-section are transferred. Accordingly, the groove52, which is the undercut shape part having a trapezoidal cross-section, is formed in the green compact (molded body)50so that the groove52surrounds the entire circumference of the side surface of the green compact50.

Next, after the molding of the green compact (molded body)50is completed, as shown inFIG. 6C, the second punch14, the third punch15, and the second die12and the first punch13that hold the green compact50are extracted from the through-hole22of the first die11(extraction step). In such an extraction step, the green compact50is held by the inner wall surface12bof the second die12.

As shown inFIG. 7A, the second die12and the first punch13that hold the green compact50are completely extracted from the through-hole22of the first die11. In this state, the green compact50is in a state where the groove52is engaged with the undercut molding part32.

Next, as shown inFIG. 7B, the second-die split body12A and the second-die split body12B that constitute the second die12are separated from each other. Specifically, the second-die split body12B is moved in the direction intersecting the insertion/removal direction Y, for example, the horizontal direction by, for example, a die moving device55or the like in a state where the second-die split body12A is fixed. In this way, by moving the second-die split body12A and the second-die split body12B constituting the second die12relative to each other in the horizontal direction L, the green compact50(refer toFIG. 5) can be released from the second die12without damaging the groove52(refer toFIG. 5) that is the undercut shape part extending (recessed) in the direction intersecting the insertion/removal direction Y.

The green compact50including the groove52that is the undercut shape part can be molded by the above-described steps.

As described above, according to the molding die and the molding method of the invention, simply by inserting the second die12having the undercut molding part32into the through-hole22of the first die11to perform molding, a high-accuracy undercut shape part (the groove52in the present embodiment) can be easily molded to the entire circumference of the side surface of the green compact (molded body)50.

The second die12consists of the second-die split bodies12A and12B capable of being split from each other, and the second-die split body12A and the second-die split body12B are split in a direction different from the insertion/removal direction Y, for example, the horizontal direction L after the molding of the green compact50. Thereby, the green compact50can be easily released from the second die12without damaging the groove52that is the undercut shape part, and the green compact50with a high-accuracy undercut shape can be formed.

Additionally, the powder W (molding object) is introduced into the through-hole22of the first die11in advance and then, the second die12is inserted into the through-hole22of the first die11to compress the molding object in a state where the second die12is attached to the first punch13. Thereby, it is possible to mold the undercut shape part in the molded body without any positional deviation and with high accuracy irrespective of the compression rate of the molding object. Therefore, it is possible to easily obtain the molded body in which the undercut shape part is formed with high accuracy.

Additionally, in the molding die10of the invention, the second die12having the undercut molding part32is inserted into the first die11so that the first die11is brought into close contact with the outer surface12aof this second die12, and then the powder W is compressed. Thereby, the close contact between splitting surfaces of the second-die split body12A and the second-die split body12B that constitute the second die12can be enhanced. Accordingly, there is no case where powder enters the splitting surfaces of the second-die split body12A and the second-die split body12B and burrs are generated in the green compact (molded body)50, and as a result, an accurate green compact (molded body)50can be obtained.

Additionally, as in the molding die10of the invention, the second die12having the undercut molding part32is inserted into the first die11so that the first die11is brought into close contact with the outer surface12aof the second die12. Thereby, damage of the second die12to which strong pressure is applied at the time of compression can be prevented.

In the molding die and the molding method of the above-described embodiment, the second die12is formed so as to be splittable into two bodies in the horizontal direction L. However, in the case where the second die12consists of three or more splittable bodies and splitting directions of the respective split bodies are changed after molding, a green compact including an undercut shape including a plurality of types of alternate projections and depressions of which directions intersecting the insertion/removal direction Y are different can be molded. For example, the second die12may be split into two in the horizontal direction L and then split into two in the insertion/removal direction Y.

Additionally, in the molding die and the molding method of the above-described embodiment, an example has been shown in which the green compact that is an example of the molded body is obtained using a powder material as the molding object. However, the molding object is not limited to the powder. For example, the invention is completely similarly applicable to so-called sizing in which a coarsely molded solid object is used as the molding object and this solid object is introduced into the cavity P of the molding die of the invention and molded in a predetermined shape.

Additionally, besides the powder or the coarsely molded solid object, those of various forms, such as aggregates and granules, can be used as the molding object.

In the above-described embodiment, the substantially rectangular parallelepiped-shaped green compact is an exemplary example of the green compact (molded body)50. However, the molded body obtained by the molding die and molding method of the invention is not limited to one having such a shape. Hereinafter, an exemplary example of some of molded bodies obtained by the molding die and the molding method of the invention will be described with reference to the drawings.

In a molded body60shown inFIG. 8, the outer shape thereof is a substantially cylindrical shape, and a groove61serving as the undercut shape part and having a trapezoidal cross-section is formed over the entire circumference of a circumferential side surface62. Additionally, a through-hole63is formed at a center portion.

In a molded body70shown inFIG. 9A, the outer shape thereof is a substantially cylindrical shape, and one groove71serving as the undercut shape part and having a semicircular cross-section is formed over the entire circumference of a circumferential side surface72. Additionally, a through-hole73is formed at a center portion.

In a molded body75shown inFIG. 9B, the outer shape thereof is a substantially cylindrical shape, and two grooves76aand76bserving as the undercut shape part and having a semicircular cross-section are formed parallel to each other over the entire circumference of a circumferential side surface77. Additionally, a through-hole78is formed at a center portion.

In a molded body80shown inFIG. 9C, the outer shape thereof is a substantially cylindrical shape, and flat surfaces81aand81bfacing each other are formed. A groove82serving as the undercut shape part and having a semicircular cross-section is formed in the portion of the circumferential side surface83excluding the flat surfaces81aand81b. Additionally, a through-hole84is formed at a center portion.

In a molded body85shown inFIG. 10A, the outer shape thereof is a substantially cylindrical shape, and a plurality of rectangular grooves86serving as the undercut shape part are formed at predetermined intervals over the entire circumference of a circumferential side surface87. Additionally, a through-hole88is formed at a center portion.

In a molded body90shown inFIG. 10B, the outer shape thereof is a substantially cylindrical shape, and a groove91serving as the undercut shape part and having a shape in which a plurality of cross-shaped grooves are connected together is formed over the entire circumference of a circumferential side surface92. Additionally, a through-hole93is formed at a center portion.

In a molded body100shown inFIG. 11A, the outer shape thereof is a square, substantially plate shape, and a groove101serving as the undercut shape part and having a semicircular cross-section is formed over the entire circumference so as to straddle four circumferential side surfaces102. Additionally, a through-hole103is formed at a center portion.

In a molded body105shown inFIG. 11B, the outer shape thereof is a square, substantially plate shape, and grooves106serving as the undercut shape part and having a semicircular cross-section are respectively formed at four corner parts where four circumferential side surfaces107intersect each other. Additionally, a through-hole108is formed at a center portion.

The respective shapes of the molded bodies listed above are merely examples, and do not limit the shapes of the molded bodies obtained by the molding die and the molding method of the invention.

Although the several embodiments of the invention have been described above, these embodiments have been presented as examples only and are not intended to limit the scope of the invention. These embodiments can be implemented in other various forms, and various omissions, substitutions, and alternations can be made without departing from the features of the invention. These embodiments and modifications thereof are included in the scope and the features of the invention as well as being included in the invention set forth the claims and the equivalent range thereof.

INDUSTRIAL APPLICABILITY

According to the molding die of the invention and the molding method using this, the undercut shape part can be molded without any positional deviation and with high accuracy.

EXPLANATION OF REFERENCE SIGNS