Divided die press tool

Abstract

A split die press tool for forming a green body (8) for a double-sided double positive cutting insert for cutting metal by compressing a powder, comprising a die having at least two die sections (1, 2) forming a punch tunnel (18) extending along a vertical pressing axis (6) between them, an upper punch unit (3) and a lower punch unit (4), wherein when the lower punch unit (4) is in a distal position in the form of a reduced pressure position, a front end periphery (20) of the lower punch unit (4) is at a first expansion level (24) corresponding to a maximum downward vertical reduced pressure expansion of the green body (8) to be formed. The punch tunnel (18) includes a first side portion (22) located on at least one of the die sections (1), the first side portion (22) having a downward vertical extension from a first pressing level (23) to a first expansion level (24) and inclined downwardly away from the pressing axis (6) by an angle β that is equal to or greater than the angle α of the adjacent inclined lower surface (13) of the green body (8). The punch tunnel (18) includes a second side portion (25) located on at least one of the die sections (1), the second side portion (25) being vertically aligned with the first side portion (22) and having a downward vertical extension from the first expansion level (24) to a first restraining level (27), where the horizontal distance to the adjacent front end periphery of the lower punch unit (4) is smaller than at the first expansion level (24).

Description

Technical Field

[0001] The present invention relates to a split-die press tool for forming a green body for a double-sided positive cutting insert by compressing powder.

Background Art

[0002] Conventional cutting inserts typically comprise a body having a top surface, a bottom surface, and circumferential side surfaces. There is a central plane between the top surface and the bottom surface. A type of cutting insert commonly referred to as a conventional "double-sided cutting insert" has a top cutting edge at the intersection between the top surface and the side surfaces, and a bottom cutting edge at the intersection between the bottom surface and the side surfaces. Further, such a cutting insert is indexable to present one of the cutting edges at a time for the cutting operation.

[0003] A group of such double-sided cutting inserts are arranged to have, as chip surfaces, a portion of the top surface adjacent to the top cutting edge and a portion of the bottom surface adjacent to the bottom cutting edge. The portions of the side surfaces adjacent to the top cutting edge and the portions of the side surfaces adjacent to the bottom cutting edge form respective relief surfaces. The relief surfaces have a negative nominal relief angle when they are inclined at 90° with respect to the central plane, and have a positive nominal relief angle when they are inclined inwardly from the associated cutting edge towards the center of the cutting insert towards the central plane. The double-sided cutting insert is called double positive when both of its second relief surfaces have a positive nominal relief angle. In such double positive cutting inserts, the side surfaces typically have a waist with respect to the central plane.

[0004] Conventional methods for producing cutting inserts for metal cutting involve forming an unsintered body by compressing powder in a press tool. The process of forming an unsintered body in a press tool typically includes the steps of: filling a press tunnel in the press tool with powder; compressing the powder to form an unsintered body in a compressed state; and depressurizing the compressed unsintered body so that it expands. The expanded and relaxed unsintered body is then removed from the press tool and subsequently undergoes additional process steps, such as sintering, grinding, and / or coating, to form the final cutting insert.

[0005] When compressing powder to form an unsintered body for a double-sided, double-positive cutting insert, a split die press tool having horizontally movable and separable die sections may be used. The press tool further comprises vertically movable upper and lower punches. The side surface of the unsintered body for forming the double-sided, double-positive cutting insert has a similar shape to the side surface of the finished cutting insert, including being inclined inward toward the center of the unsintered body. When the powder is compressed to form the unsintered body in its compressed state, the lower punch is in the uppermost position inside the press tunnel within the press tool. When the unsintered body is in its compressed state, the press tunnel surface of the die section adjacent to the unsintered body has an extension equal to the side surface of the unsintered body. Thus, in the case of an unsintered body for a double-sided, double-positive cutting insert, the press tunnel surface is configured to follow the inclination of the side surface of the unsintered body. Furthermore, the inclined surface of the press tunnel extends over a certain vertical distance below the front end surface of the lower punch when the lower punch is in its uppermost position. Therefore, the unsintered body can expand downwards under reduced pressure without damaging the bottom edge at the lower end of the inclined side surface.

[0006] A problem associated with the types of split die press tools described above is that when filling the press tool with powder for the unsintered body, excess powder tends to leak between the lower punch and the side surface of the die section. Powder leakage can affect the operator's health, damage the press tool, or cause shape deviations near the edge of the unsintered body due to localized loss of material. [Overview of the project]

[0007] The object of the present invention is to provide a split die pressing tool that can mitigate the drawbacks of the prior art and reduce powder leakage. This object is achieved by the present invention using the split die pressing tool described in claim 1.

[0008] The present invention relates to a split die press tool for forming an unsintered body for a double-sided double-positive cutting insert for metal cutting by compressing powder, wherein the unsintered body has a top edge, a bottom edge, and a side surface connecting the top edge and the bottom edge, the top edge being associated with an adjacent inclined upper surface on the side surface, the bottom edge being associated with an adjacent inclined lower surface on the side surface, and each of the inclined surfaces having a positive nominal angle α, and the split die press tool is - A die comprising at least two die sections, - Each dissection is positioned to be movable along the horizontal axis to its respective proximal pressing position and several respective distal positions. - When each die section is in its respective pressing position, the die sections form punch tunnels between them that extend along the vertical pressing axis. Dai and, - Upper punch unit and lower punch unit, - Both have a front end including the circumferential front end, and both are arranged in the punch tunnel with their front ends facing each other. - Both are positioned within the punch tunnel so as to be movable along the pressing axis to their respective proximal pressing positions and several respective distal positions. Upper punch unit and lower punch unit, Equipped with, - When the die section, lower punch unit, and upper punch unit are in their respective pressing positions, the area around the front end of the lower punch unit is located at a first pressing level, and a compression space corresponding to the compressed state of the unsintered body to be formed is formed within the punch tunnel. - When the lower punch unit is in the distal position of the reduced pressure position, the area around the front end of the lower punch unit is at a first expansion level corresponding to the maximum downward vertical reduced pressure expansion of the unsintered body to be formed. - The punch tunnel comprises a first side surface portion located in at least one of the die sections, the first side surface portion having a vertical range from a first pressing level downward to a first expansion level, - The first side surface portion is inclined such that, when viewed in the vertical cross-section of the punch tunnel, it is inclined downward by an angle β of the angle α of the adjacent inclined lower surface of the unsintered body to be formed, and away from the pressing axis. - The punch tunnel comprises a second side surface portion located in at least one of the die sections, the second side surface portion being perpendicularly aligned with the first side surface portion and having a vertical range from a first expansion level downward to a first suppression level, wherein at the first suppression level, the horizontal distance to the periphery of the adjacent front end of the lower punch unit is less than the horizontal distance at the first expansion level. Regarding die-pressing tools.

[0009] Therefore, the first side surface portion in the punch tunnel is inclined downward by an angle β and away from the pressing axis. Angle β is at least the angle α of the adjacent lower inclined surface of the unsintered body to be formed in the split die tool. Furthermore, the first side surface portion has a vertical range from a first pressing level, where the periphery of the front end of the lower punch unit is located when the lower punch unit is in the pressing position, to a first expansion level, which is slightly below the first pressing level and corresponds to the maximum downward vertical expansion of the unsintered body during depressurization. Such inclination and vertical range of the first side surface portion allows the unsintered body, after being compressed in the tool, to expand during depressurization without damaging the bottom edge or its associated inclined lower surface through harmful contact with the side surface in the punch tunnel.

[0010] The second side surface portion is aligned perpendicularly to the first side surface portion and extends downward from the first expansion level to the first suppression level. Because the horizontal distance between the second side surface portion and the adjacent front end of the lower punch unit at the first suppression level is less than the horizontal distance at the first expansion level, the horizontal gap through which powder may leak during filling narrows from the first expansion level to the first suppression level. Therefore, at least some of the powder that leaks beyond the first expansion level can be contained at the first suppression level. Thus, unwanted powder leakage through the horizontal gap formed between the lower end of the first side surface portion at the first expansion level and the punch unit during tool filling can be prevented by the inventive second side surface portion.

[0011] The split die press tool according to the present invention is suitable for forming an unsintered body by compressing powder such as cermet, cemented carbide powder, or metallurgical powder. During the formation of the unsintered body in the split die press tool, the powder is compressed to form the unsintered body, which takes a compressed state after the intended maximum pressure has been applied. In the compressed state, the unsintered body has its minimum dimensions. When the pressure is removed, the unsintered body expands. Once the depressurization is complete, the unsintered body is no longer in a compressed state and has experienced maximum depressurization expansion. After the unsintered body has been formed and removed from the press tool, the unsintered body can undergo other processes such as sintering, grinding, edge treatment, and / or coating. Cutting inserts can be obtained from the unsintered body and used for machining, for example, metal cutting. Examples of such cutting inserts are milling inserts, turning inserts, and drilling inserts.

[0012] The split die press tool according to the present invention is suitable for forming an unsintered body for a double-sided double-positive cutting insert for metal cutting. The unsintered body typically comprises a top edge, a bottom edge, and a side surface connecting the top and bottom edges. In the finished cutting insert, these edges may constitute a cutting edge. The top edge is associated with an adjacent inclined upper surface on the side surface, and the bottom edge is associated with an adjacent inclined lower surface on the side surface. In the finished cutting insert, these inclined surfaces may constitute a second relief surface. Each of both inclined surfaces has a positive nominal angle α, for example, 2 to 35°. In the finished cutting insert, the positive nominal angle α corresponds to the positive nominal relief angle.

[0013] When viewed in a vertical cross-section passing through the top edge, the inclined upper surface extends downward and inward toward the center of the cutting insert. When viewed in a vertical cross-section passing through the bottom edge, the inclined lower surface extends upward and inward toward the center of the cutting insert. The cross-sections form vertical planes parallel to the central vertical plane passing through the edges. In some cases, the side surfaces have waists, and the inclined surfaces project outward from these waists, terminating at their respective edges.

[0014] Depending on the case, the unsintered body may have a circular shape or a polygonal shape, such as a square, rectangle, pentagon, or hexagon, when viewed from above. The unsintered body may have inclined upper and lower surfaces along the entire or a portion of its side surface, for example, along a small portion of the side of two sides of an unsintered body that have a square or rectangular shape. Depending on the case, only a portion of the side surface of one or more sides of the unsintered body may have both an upper inclined surface and a lower inclined surface.

[0015] The split die press tool comprises a die having at least two movable die sections and two movable punch units. The die sections are movable in directions perpendicular to the punch units.

[0016] When the split die press tool is positioned for operation, the die section is positioned to be movable in both directions along the horizontal axis, and the punch unit is positioned to be movable in both directions along the vertical axis. In this application, terms such as vertical and horizontal, or “up,” “down,” “inward,” and “outward,” are used in relation to the operational position of the split die press tool. The level of the split die press tool corresponds to the vertical position in the vertical cross-section of the split die press tool.

[0017] A split die press tool may have any appropriate number of die sections, for example, two or four. The die sections are preferably organized circumferentially around a center, in which case they are movable inward toward the center and outward toward the center. Thus, the space at the center of the punch tunnel morphology is operable to become smaller or larger. Depending on the case, each die section may be movable individually or in synchronization with some or all of the die sections, for example, in synchronization with the die section opposite the center. A die section is in the proximal pressing position when it has moved inward to a position where the punch tunnel has size for pressing. During operation, the proximal pressing position is the innermost position for each die section. Any position of a die section outward from the proximal pressing position is a distal position.

[0018] The punch unit is movable along the vertical pressing axis. Depending on the case, each punch unit may have a single punch, or each punch unit may be divided into several part punches in the vertical direction. The part punches of a punch unit may be arranged, for example, concentrically around a center or adjacent to each other as slices, forming a vertical cross-section. Depending on the case, each punch unit may be movable individually or synchronously with other punch units. In the case of a punch unit with several part punches, each part punch may be movable individually or synchronously with some or all of the part punches. The punch units are located within a punch tunnel formed in the center of the die section, with the upper punch unit entering from above and the lower punch unit entering from below. Thus, their respective front ends face each other. The punch unit is in the proximal pressing position when it has been moved inward to a position for applying the maximum intended pressure to the unsintered body to be formed. During operation, this is the innermost position for both punch units. Any upper position of the upper punch unit and any lower position of the lower punch unit are distal positions.

[0019] When all die sections and both punch units are in their respective proximal pressing positions, the space at the center of the punch tunnel forms a compression space corresponding to the dimensions of the unsintered body to be formed in the compressed state.

[0020] Each punch unit has a front end. In embodiments where the punch unit is composed of several partial punches, the front end is generally formed by the front ends of all the partial punches. Each punch unit preferably has a front end surface located at the front end. The front end surface has a topography / geometry corresponding to the desired topography / geometry of the green body to be formed. The front end has a periphery, which should be understood as the edge of the front end that is farthest from the center of the punch tunnel, in other words, the edge closest to the dissection. The periphery is also preferably the outer edge of the front end surface and also the outer edge of the entire punch unit.

[0021] Optionally, each punch unit has a circumferential side surface that extends downward from the end surface. The circumferential side surface of the punch unit is preferably perpendicular. Thus, the punch unit is guided to slide in the straight part in the vertical direction of the punch tunnel, and furthermore, the risk that the leaking powder hits the circumferential side surface and is caught is reduced.

[0022] The punch tunnel is formed around the space at the center of the dissection and is radially outwardly limited by facing inwardly the side surface of the dissection. These side surfaces comprise several side surface portions that can have different locations, ranges, and / or inclinations. Optionally, the side surface portions are located on a single dissection or extend across several dissections. The side surface portions that extend across several dissections can be discontinuous surfaces that are divided by the gaps between the dissections when the dissections are in their distal positions.

[0023] During operation, the first and second side surface portions are circumferentially and vertically aligned with the side surface of the green body and, specifically, with the adjacent inclined lower surface on the side surface of the green body. The first side surface portion faces the adjacent inclined lower side surface of the green body so as to contribute to the formation of the adjacent side surface of the green body during decompression.

[0024] The first and second side surface portions are vertically aligned, with the first side surface portion being above the second side surface in the vertical direction and connected to the second side surface portion at its lower end.

[0025] The horizontal distance from any one of the side surface portions of the punch tunnel located in at least one dissection to around the adjacent front end of the punch unit is, for example, the distance measured horizontally in a vertical cross-section. The distance is also measured horizontally when the surroundings are at different levels. The horizontal distance at the first suppression level is less than the horizontal distance at the first expansion level. According to one embodiment, the horizontal distance at the first suppression level is less than 50% of the distance at the first expansion level, preferably less than 25%. The horizontal distance at the first suppression level is preferably at most 20 μm, and preferably at most 10 μm. Thus, advantageously, it is ensured that a significant amount of powder leakage is prevented.

[0026] According to one embodiment, the horizontal distance at the first suppression level is at least 0.1 μm, preferably at least 2 μm. Thus, the punch unit can slide within the punch tunnel without excessive friction.

[0027] The vertical distance between two levels is, for example, the distance measured vertically in a vertical cross-section. According to one embodiment, the vertical distance from the first expansion level to the first suppression level is at most 1 mm, preferably at most 0 .5 mm. Thus, the space between the lower punch unit and the second side surface portion is kept small. Since powder leakage is suppressed at the first suppression level, the amount of powder that may leak beyond the first expansion level corresponds to the amount of powder that fits within this space located above the first suppression level . Thus, such a limited vertical range advantageously contributes to limiting powder leakage.

[0028] During the powder filling process in operation, the lower punch unit is lowered, and the space above the lower punch unit in the punch tunnel is filled with powder. In the subsequent compression process, when the lower punch unit is operated to move upward, the front end of the lower punch carries the powder into the compression space. Excess powder fills the space between the second side surface portion and the lower punch. According to one embodiment, the vertical distance from the first expansion level to the first suppression level is at least 0.05 mm, preferably at least 0.2 mm. Thus, it is ensured that there is sufficient space to accommodate such excess powder.

[0029] The maximum vertical downward depressurization expansion of the unsintered body to be formed may be 0.5–3% of the total vertical range (height) of the unsintered body in the compressed state. According to one embodiment, the vertical distance from the first pressing level to the first expansion level is at least 0.05 mm, preferably at least 0.1 mm. This accommodates the most common unsintered body expansion for double-sided double-positive cutting inserts.

[0030] The first side surface portion is inclined downward and away from the pressing axis by an angle β of at least the angle α of the adjacent inclined lower surface of the unsintered body to be formed, when viewed in a vertical cross-section of the punch tunnel. Thus, in a vertical cross-section, angles α and β are measured between the respective inclined surfaces and a vertical plane perpendicular to the plane of the vertical cross-section. The same result is obtained when measured in a vertical cross-section between the surface and the projection of the vertical pressing axis. According to the embodiment, angle β is 2 to 35°, preferably 5 to 20°. This corresponds to the most common desired nominal relief angle for the double-sided double-positive cutting insert to be fabricated.

[0031] In some cases, angle β may be greater than angle α, and the first lateral surface portion may extend linearly or concavely when viewed in a vertical cross-section. In embodiments including a curved first lateral surface portion, angle β should be measured as tangent to the first lateral surface portion. Thus, a safety margin is created to further protect the bottom edge of the unsintered body to be formed from damage caused by contact with the first lateral surface portion during expansion.

[0032] According to one embodiment, angle β is equal to angle α. Therefore, advantageously, the unsintered body to be formed is supported during depressurized expansion.

[0033] According to one embodiment, the second lateral surface portion comprises an upper portion extending downward from a first expansion level to a first relaxation level. Optionally, the upper portion extends in the same direction as the first lateral surface portion and has a larger inclination angle ε or a slightly concave shape. Thus, the bottom edge of the unsintered body to be formed is further protected from damage by contact with the upper portion of the second lateral surface portion during expansion.

[0034] In some cases, the vertical distance from the first expansion level to the first relaxation level is 0 to 0.5 mm, preferably 0.05 mm to 0.2 mm.

[0035] According to one embodiment, the second side surface portion comprises a lower portion which extends downward from a first relaxation level to a first suppression level and is inclined downward and toward the pressing axis at an angle γ of at least 5° and at most 45° when viewed in the vertical cross-section of the punch tunnel. Thus, it is ensured that excess powder initially trapped does not clog between the lower second side surface portion and the adjacent side of the lower punch unit. After a depressurization step during operation, the lower punch is retracted, the section is moved to a distal position, and the excess powder is released and can slide down over the lower surface portion.

[0036] The lower portion of the second side surface portion is preferably shaped in such a way that excess powder can fall off more easily when viewed in a vertical cross-section. For example, a linear or curved shape, where a convex shape may be beneficial.

[0037] According to one preferred embodiment, all positions of the first and second lateral surface portions below the expansion level have a horizontal distance to the perimeter of the adjacent front end of the lower punch unit that is greater than the horizontal distance at the suppression level.

[0038] According to one embodiment, when the lower punch unit is in the distal retracted position of the filling position, the area around the front end of the lower punch unit is at the filling level, and the filling level is below a first suppression level. Designing a split die press tool with such a low filling position is advantageous because it allows sufficient room to initially fill the powder at a low density and still achieves strong consolidation when moving the lower and upper punch units to their respective proximal pressing positions. It is also advantageous that all available space for leaked powder, which is space above the first suppression level, is located above the level of the filling position.

[0039] According to one embodiment, the punch tunnel comprises a bottom side surface portion located in at least one of the die sections, which is perpendicularly aligned with a second side surface portion and has a vertical range from a first suppression level downward to a filling level. At each level between the first suppression level and the filling level, the horizontal distance from the bottom side surface portion to the perimeter of the adjacent front end of the lower punch unit is the same. Thus, the lower punch unit is properly guided within the punch tunnel, and all available space for leaked excess powder is located above the first suppression level.

[0040] It is preferable that both the bottom side surface portion and the adjacent portion of the circumferential side surface of the punch unit be linear and perpendicular when viewed in a vertical cross-section.

[0041] According to one embodiment, the side surface portions corresponding to the first and second side surface portions are positioned adjacent to the upper punch unit. This is advantageous in preventing the powder from leaking upward during the compaction of the powder in the pressing process. According to one exemplary embodiment, - When the upper punch unit is in the pressing position, the area around the front end of the upper punch unit is at a second pressing level. - When the upper punch unit is in the distal position of the reduced pressure configuration, the area around the front end of the lower punch unit is at a second expansion level corresponding to the maximum upward vertical reduced pressure expansion of the unsintered body. - The punch tunnel comprises a third side surface portion located in at least one of the die sections, the third side surface portion being perpendicularly aligned with the first and second side surface portions and having a vertical range from a second pressing level upward to a second expansion level. - The third side surface portion, when viewed in the vertical cross-section of the punch tunnel, is inclined upward by an angle β of at least the angle α of the adjacent upper inclined surface of the unsintered body to be formed, and away from the pressing axis. - The punch tunnel comprises a fourth side surface portion located in at least one of the die sections, the fourth side surface portion being perpendicularly aligned with the third side portion and having a vertical range from a second expansion level upward to a second suppression level, wherein at the second suppression level, the horizontal distance to the perimeter of the adjacent front end of the upper punch unit is less than the horizontal distance at the second expansion level.

[0042] Other embodiments include having a first side surface portion and a second side surface portion, as well as differently formed surfaces, on at least one die section in the upper punch unit.

[0043] Preferably, the third side surface portion is symmetrical with respect to the first side surface portion, and the fourth side surface portion is symmetrical with respect to the second side surface portion, across the horizontal axis between the first and second pressing levels. The symmetry may be specular symmetry or rational symmetry. Double-sided cutting inserts to be made from unsintered bodies to be formed in a press tool typically have rotational symmetry. Therefore, this embodiment is advantageously suited for forming unsintered bodies for such general cutting inserts.

[0044] According to another aspect of the present invention, the split die pressing tool comprises a powder which can be pressed onto an unsintered body in a compressed state, and the unsintered body which can be depressurized to form an unsintered body. Thus, the split die pressing tool also comprises a powder and an unsintered body to be formed from the powder. The formed unsintered body has a top edge, a bottom edge, and a side surface connecting the top edge and the bottom edge, the top edge being associated with an adjacent inclined upper surface on the side surface, and the bottom edge being associated with an adjacent inclined lower surface on the side surface, and each of the respective inclined surfaces having a positive nominal angle α.

[0045] The exemplary embodiments will be described in more detail below with reference to the attached drawings. [Brief explanation of the drawing]

[0046] [Figure 1] This is a schematic diagram of a first embodiment of a split die press tool, in which two die sections, an upper punch, and a lower punch are in the pressing position. [Figure 2] This is a schematic exploded assembly diagram of the first embodiment of a split die press tool. [Figure 3] This is a perspective view of an unsintered body formed in a split die press tool according to the first embodiment. [Figure 4] This is a diagram of a vertical cross-section passing through the unsintered body in Figure 3, where the plane of the vertical cross-section is the central vertical plane. [Figure 5] This is an enlarged cross-sectional view of a split die press tool according to the first embodiment, when the split die press tool is set up to compress powder and form an unsintered body in a compressed state. [Figure 6] This is an enlarged cross-sectional view corresponding to Figure 5 of a split die press tool according to the first embodiment, when the split die press tool is set up to allow the unsintered body to expand downward to its maximum extent under reduced pressure. [Figure 7] This figure corresponds to Figure 6 of the second embodiment of the split die press tool. [Figure 8a] This is a cross-sectional view of a split die press tool, showing the positions of the die section and punch unit during the press cycle. [Figure 8b] This is a cross-sectional view of a split die press tool, showing the positions of the die section and punch unit during the press cycle. [Figure 8c] This is a cross-sectional view of a split die press tool, showing the positions of the die section and punch unit during the press cycle. [Figure 8d] This is a cross-sectional view of a split die press tool, showing the positions of the die section and punch unit during the press cycle. [Modes for carrying out the invention]

[0047] All diagrams are schematic and not necessarily to scale, and generally show only the parts necessary to illustrate each embodiment, while other parts may be omitted or merely suggested. Unless otherwise indicated, the same reference number refers to the same or corresponding part in various diagrams.

[0048] Figures 1 and 2 show the overall design of one embodiment of a split die press tool according to the present invention. The split die press tool comprises two die sections 1 and 2, an upper punch unit in the form of a single upper punch 3, and a lower punch unit in the form of a single lower punch 4.

[0049] Both dissections 1 and 2 are positioned to be movable along the horizontal axis 5, and each is movable to its respective proximal pressing position and to several respective distal positions. Specifically, dissections 1 and 2 are movable inward toward the center 7 and outward toward the center 7.

[0050] Both punches 3 and 4 are positioned to be movable along the vertical pressing axis 6, and each is movable to its respective proximal pressing position and to several respective distal positions. Specifically, punches 3 and 4 are movable toward each other and toward the center 7, and are movable toward each other and toward the center 7.

[0051] In exemplary embodiments, each die section 1, 2 and each punch 3, 4 can move independently of the other die section and punch.

[0052] The split die press tool is operable to form an unsintered body by compressing powder, which in this exemplary embodiment is cemented carbide powder. During operation, the powder is compressed to form an unsintered body in a compressed state, which is then depressurized and expanded to its final shape. Figure 2 shows the unsintered body 8 formed in the tool, which has its final shape. The unsintered body 8 is to be used later in a process to produce a cutting insert for metal cutting.

[0053] Referring to Figures 3 and 4, the unsintered body 8 comprises a top surface 14, a bottom surface 15, and a circumferential side surface 11 connecting the top surface 14 and the bottom surface 15. A top edge 9 is formed at the intersection between the side surface 11 and the top surface 14. A bottom edge 10 is formed at the intersection between the side surface 11 and the bottom surface 15. The top edge 9 is associated with an adjacent inclined upper surface 12 on the side surface 11, and the bottom edge 10 is associated with an adjacent inclined lower surface 13 on the side surface. Figure 4 shows a vertical cross-section passing through the top edge 9 and the bottom edge 10, which is the central vertical plane 21. The upper surface 12 extends downward and inward by an angle α, and the lower surface 13 extends upward and inward by an angle α. Both angles α constitute positive nominal angles that will form a positive nominal relief angle in the finished cutting insert. The finished cutting insert fabricated from the unsintered body 8 will be double-sided double-positive. In the unsintered body 8, the nominal angle α is the angle between the vertical planes 16 perpendicular to the plane of the vertical cross-section as shown in Figure 4. In the first embodiment, the angle α is 15°. Due to the inclined upper and lower surfaces 12, 13, the unsintered body has a waist to the central horizontal plane 17.

[0054] When die sections 1 and 2 are in their respective pressing positions, they form a punch tunnel 18 between them, with the center 7 located in the center of the punch tunnel 18. In Figure 1, both die sections 1 and 2 and both punches 3 and 4 are in their respective proximal pressing positions, and a compression space corresponding to the shape of the unsintered body 8 in the compressed state is formed between them. By operating die sections 1 and 2 and / or punches 3 and 4 to move to their respective distal positions, the space between components 1, 2, 3 and 4 is enlarged to expand the unsintered body 8 and to allow the unsintered body 8 to be removed from the split die press tool.

[0055] The upper punch 3 and lower punch 4 each have a top surface 14 and bottom surface 15 of the unsintered body, and a front end surface 19 corresponding to the desired topography. Each front end surface 19 has a circumferential circumference 20. Depending on the positions of the lower and upper punches 3 and 4 in the punch tunnel, their respective circumferences are located at corresponding different heights, in other words, levels, within the punch tunnel 18.

[0056] As shown in Figure 5, when the lower punch 4 is in the proximal pressing position, the circumference 20 around its front end is located at the first pressing level 23. The unsintered body is in a compressed state. As shown in Figure 6, when the lower punch 4 is in the distal decompression position, the circumference 20 around its front end is located at the first expansion level 24. The vertical distance 38 between the first pressing level 23 and the first expansion level 24 corresponds to the maximum downward vertical decompression expansion of the unsintered body 8 after it is released from the compressed state. According to the first embodiment, the vertical distance 38 is 0.1 mm. Therefore, the first expansion level 24 is located below the first pressing level 23.

[0057] As powder is filled into the split die press tool during operation, the upper punch 3 is moved aside to expose the punch tunnel 18, and the lower punch 4 is in the distal filling position (see Figure 8a). When the lower punch 4 is in the filling position, the front end circumference 20 is at the filling level 35.

[0058] The upper and lower punches 3 and 4 each have a circumferential side surface 36 that extends rearward from the periphery 20 of their respective front end surface 19. According to the first embodiment, the circumferential side surfaces 36 are each perpendicular and parallel to the pressing axis 6 when viewed in the cross-sections of Figures 5 and 6.

[0059] The punch tunnel 18 comprises a first side surface portion 22 located in the first die section 1; see Figures 5 and 6. As can be derived from Figures 1 and 2, in the first embodiment described, the second die section 2 also comprises a corresponding first side surface portion 22. The first side surface portion 22 is positioned circumferentially aligned with the adjacent inclined lower surface 13 of the unsintered body 8 and has a vertical range from the first pressing level 23 downward to the first expansion level 24. The first side surface portion 22 is inclined downward and outward from the first pressing level 23 by an angle β away from the pressing axis 6; see Figure 6. The angle β can also be measured as the angle between the first side surface portion 22 and a vertical plane 16 perpendicular to the plane of the vertical cross section shown in Figure 6. In the first embodiment shown, the angle β is 15° and is therefore equal to the angle α. In other embodiments, the angle β is greater than the angle α.

[0060] The punch tunnel 18 further comprises a second side surface portion 25, which is also located in the first die section 1. In the first embodiment, the second die section 2 also comprises a second side surface portion 25. The second side surface portion 25 is perpendicularly aligned with the first side surface portion 22 and is connected to the lower end of the first side surface portion 22 at the first expansion level 24. The second side surface portion 25 has a vertical range from the first expansion level 24 downward to the first suppression level 27. The first suppression level 27 is a level in the punch tunnel 18 that is below the first expansion level 24, and the vertical distance 39 from the first expansion level 24 to the first suppression level 27 is 0.19 mm. In the first embodiment, the total distance from the first pressing level 23 to the first suppression level 27 is the sum of distance 38 and distance 39, which is 0.29 mm in the first embodiment.

[0061] Each point on the first and second side surface portions 22, 25 has a horizontal distance to the perimeter 20 of the adjacent front end of the lower punch 4. This horizontal distance is measured horizontally when viewed in the cross-section of Figure 6, and is also measured horizontally when the perimeter 20 is located at different levels.

[0062] Referring to Figure 5, the horizontal distance 28 between the second lateral surface portion 25 and the circumference 20 of the front end of the lower punch 4 at the first suppression level 27 is less than the water wall distance 29 between the second lateral surface portion 25 (or the first lateral surface portion 22) and the circumference 20 of the front end of the lower punch 4 at the first expansion level 24. As shown in Figure 5, when the first dicect 1 is in the proximal pressing position, the horizontal distance 28 between the second lateral surface portion 25 and the circumference 20 of the front end of the lower punch 4 at the first suppression level 27 is 5 μm, and the horizontal distance 29 between the second lateral surface portion 25 (or the first lateral surface portion 22) and the circumference 20 of the front end of the lower punch 4 at the first expansion level 24 is determined by the maximum downward vertical decompression expansion and angle β.

[0063] The second lateral surface portion 25 comprises an upper portion 30 extending downward from the first expansion level 24 to the first relief level 31. In the first embodiment described, the upper portion 30 extends in the same direction as the first lateral surface portion 22. The upper portion 30 is inclined downward and outward away from the pressing axis 6 by an angle ε. The angle ε can be measured as the angle between the upper portion 30 and a vertical plane 16 perpendicular to the plane of the vertical cross-section as shown in Figure 5. In the first embodiment shown, the angle ε is 15° and is therefore equal to angles α and β.

[0064] The second lateral surface portion 25 further comprises a lower portion 32 extending downward from the first relaxation level 31 to the first suppression level 27. The lower portion 32 extends downward toward the pressing axis 6 at an angle γ of 30°. The angle γ can be measured as the angle between the lower portion 32 and a vertical plane 16 perpendicular to the plane of the vertical cross-section as shown in Figure 5.

[0065] According to the first embodiment, both the upper portion 30 and the lower portion 32 have a linear range when viewed in the cross-section of Figure 6. In the first embodiment, the vertical distance 33 between the first expansion level 24 and the first relaxation level 31 is 0.1 mm, and the vertical distance from the first relaxation level 31 to the first suppression level 27 is 0.09 mm. In the first embodiment, the total vertical distance 39 of the second lateral surface portion 25 from the first expansion level 24 to the first suppression level 27 is the sum of distance 33 and distance 40. When the first dicect 1 is in the proximal pressing position as shown in Figure 5, the horizontal distance 34 from the second lateral surface portion 25 at the first relaxation level 31 to the circumference 20 of the front end of the lower punch 4 is influenced by angle ε and distance 33. This is the maximum horizontal distance from the lateral surface of the punch tunnel 18 to the circumference 20 of the front end of the lower punch 4.

[0066] Finally, the punch tunnel 18 also includes a bottom side surface portion 37 located in the first die section 1. In the first embodiment, the second die section 2 also includes a bottom side surface portion 37. The bottom side surface portion 37 is vertically aligned with the first and second side surface portions 22, 25 and connects to the lower end of the lower portion 32 of the second side surface portion 25 at the first pressing level 27. The bottom side surface portion 37 has a vertical range from the first pressing level 27 downwards to the filling level 35, and the bottom side surface portion 37 is vertical. The filling level 35 is below the first pressing level 27, and the vertical distance 41 from the first pressing level 23 to the filling level 35 is 50% of the total vertical range (height) of the unsintered body in the compressed state. At each level between the first suppression level 27 and the filling level 35, the horizontal distance from the bottom side surface portion to the perimeter 20 of the adjacent front end of the lower punch 4 is the same. Therefore, the gap between the circumferential side surface 36 and the bottom side surface portion 37 of the lower punch 4 is constant and equal to the horizontal distance 28 at the first suppression level 27. When the first dicect 1 is in the proximal pressing position as shown in Figure 5, the horizontal distance 28 and the gap are 5 μm.

[0067] The first die section of the first embodiment comprises a third side surface portion 42 and a fourth side surface portion 43. These side surface portions 42, 43 have location and extent relative to the top edge 9, the upper surface 12, and the upper punch 3 of the unsintered body 8, which correspond to the location and extent of the first side surface portion 22 and the second side surface portion 25 relative to the bottom edge 10, the lower surface 13, and the lower punch 4 of the unsintered body 8. Therefore, the third side surface 42 and the fourth side surface 43 will not be described in detail. In the first embodiment, across the central neutral horizontal plane at the waist of the unsintered body in the compressed state, the third side surface portion 42 is mirror symmetric with respect to the first side surface portion 22, and the fourth side surface portion 43 is mirror symmetric with respect to the second side surface portion 25. However, in other embodiments, the third side surface portion 42 and the fourth side surface portion 43 have other symmetries across the horizontal axis in the neutral plane. Yet another embodiment has only the first side surface portion 22 and the second side surface portion 25, and has various side surfaces in the upper punch.

[0068] Referring to Figures 8a to 8f, the positions and steps during the pressing cycle when the split die pressing tool according to the first embodiment is in operation will be described.

[0069] In Figure 8a, the first die section 1 and the second die section 2 are in their respective proximal pressing positions, forming a punch tunnel 18 between them. The upper punch 3 is removed from the punch tunnel 18 so that the punch tunnel is accessible from above. The lower punch 4 is in the distal position of the filling position, with its front end circumference 20 located at the filling level 35. A predetermined amount of cemented carbide powder is filled into the punch tunnel 18. The powder flows downward in the punch tunnel 18, filling the space within the punch tunnel 18 upward from the front end 19 of the lower punch 4. As shown in the figure, the lower portion 32 of the second lateral surface portion 25 extends downward toward the pressing axis 6. Thanks to this advantageous design, there is only a small gap between the circumference 20 of the lower punch 4 and the first die section 1. When the first die section 1 and the second die section 2 are in their respective proximal pressing positions, the horizontal distance 28 of the gap is 5 μm. Thanks to this narrow gap, only a small amount of powder can leak beyond the perimeter 20 around the front end of the lower punch 4.

[0070] In Figure 8b, the split die pressing tool is operated to move the lower punch 4 to its proximal pressing position, so that the periphery 20 of the lower punch 4 is at the first pressing level 23. Furthermore, the split die pressing tool is operated to move the upper punch 3 to its proximal pressing position, so that the periphery 20 of the upper punch 3 is at the second pressing level 44. Thus, the powder is compressed, forming an unsintered body 8 in a compressed state. The excess powder fills the space between the first and second side surface portions 22, 25 on one side and the lower punch 4 on the other. Similarly, the excess powder fills the space between the third and fourth side surface portions 42, 43 on one side and the upper punch 3 on the other. Due to the upper portion 48 of the fourth side surface 43 (corresponding to the lower portion 32 of the second side surface portion 25) which extends upward toward the pressing axis 6, only a small gap exists between the periphery 20 of the upper punch 3 and the side surface of the first die section 1. When the first dissection 1 and the second dissection 2 are in their respective proximal pressing positions, the horizontal distance 28 of the gap is 5 μm. Thanks to this narrow gap, when the powder is compacted, only a small amount of powder can be ejected beyond the perimeter 20 around the front end of the upper punch 3.

[0071] The split die press tool according to the first embodiment further comprises a second relaxation level 45 corresponding to a first relaxation level 31, and a second suppression level 46 corresponding to a first suppression level 27.

[0072] After pressing, the lower punch 4 is moved to a distal position in the form of its depressurized position, where the perimeter 20 is at a first expansion level 24 (see Figure 8c). Simultaneously, the upper punch 3 is moved to a distal position in the form of its depressurized position, where the perimeter 20 is at a second expansion level 47. The first die section 1 and the second die section 2 are still in their respective pressing positions. Thus, the unsintered body 8 undergoes vertical depressurized expansion, where the unsintered body 8 expands vertically. As shown in Figure 6, the inclination angles β of the first side surface portion 22 and the third side surface portion 42 are equal to the inclination angles α of the adjacent lower surface 13 and the adjacent upper surface 12 of the unsintered body 8, respectively. Thus, advantageously, the bottom edge 10 and top edge 9 are not damaged by the side surfaces during depressurized expansion. The first expansion level 24 and the second expansion level 47 correspond to the total maximum vertical depressurization expansion of the unsintered body 8. The vertical distance between the second expansion level 47 and the first expansion level 24 corresponds to the vertical distance from the top edge 9 to the bottom surface 10 of the unsintered body 8 in the final shape.

[0073] After depressurization, the first die section 1 and the second die section 2 are moved further apart to their respective distal positions to release the completed unsintered body 8. Thus, the unsintered body 8 undergoes horizontal depressurization expansion, where it expands horizontally. Referring to Figure 8d, any excess powder trapped within the punch tunnel 18 can leak downward and be removed from the split die press tool. This is facilitated by the inclination angle γ of the lower portion 32 of the second side surface portion 25, which is 30°; see Figure 6. Finally, the upper punch 3 is removed from the punch tunnel 18, and the lower punch 4 is extruded together with the completed unsintered body 8 resting on the front end surface 19.

[0074] A second embodiment of the split die press tool is shown in Figure 7. The second embodiment differs from the first embodiment in the design of the first side surface portion 22 and the second side surface portion 25. The upper portion 30 of the first side surface portion 22 and the lower portion 32 of the second side surface portion 25 are mostly concave. The very bottom of the lower portion 32 of the second side surface portion 25 is convex in order to make smooth contact with the vertical bottom side surface portion 37. This embodiment is advantageous in that the risk of powder getting stuck in sharp corners or pockets is further reduced. The second embodiment is an example of an embodiment in which angle β is greater than angle α.

[0075] The first die section of the second embodiment comprises a third side surface portion 42 and a fourth side surface portion 43. These side surface portions 42, 43 have location and extent relative to the top edge 9 of the unsintered body 8, the upper surface 12 of the unsintered body 8, and the upper punch 3, and this location and extent corresponds to the location and extent of the first side surface portion 22 and the second side surface portion 25 relative to the bottom edge of the unsintered body 8, the lower surface 13 of the unsintered body 8, and the lower punch 4. Therefore, they are not further described or illustrated in the figures.

Claims

1. A split die press tool for forming an unsintered body (8) for a double-sided double-positive cutting insert for cutting metal by compressing powder, wherein the unsintered body (8) has a top edge (9), a bottom edge (10), and a side surface (11) connecting the top edge (9) and the bottom edge (10), the top edge (9) being associated with an adjacent inclined upper surface (12) on the side surface (11), and the bottom edge (10) being associated with an adjacent inclined lower surface (13) on the side surface (11), and both respective inclined surfaces (12, 13) having a positive nominal angle α, and the split die press tool is, - A die comprising at least two die sections (1, 2), - Each dissection (1, 2) is positioned to be movable along the horizontal axis to its respective proximal pressing position and several respective distal positions. - When each die section (1, 2) is in its respective pressing position, the die sections (1, 2) form a punch tunnel (18) between them that extends along the vertical pressing axis (6). Dai and, - Upper punch unit (3) and lower punch unit (4), - Both have a front end (19) that includes the circumferential front end circumference (20), and both are arranged in the punch tunnel (18) with their front ends (19) facing each other. - Both are positioned within the punch tunnel (18) so as to be movable along the pressing axis (6) to their respective proximal pressing positions and several respective distal positions. An upper punch unit (3) and a lower punch unit (4), Includes, - When the die sections (1, 2), the lower punch unit (4), and the upper punch unit (3) are in their respective pressing positions, the area around the front end (20) of the lower punch unit (3) is located at a first pressing level (23), and a compression space corresponding to the compressed state of the unsintered body (8) to be formed is formed within the punch tunnel (18). - When the lower punch unit (4) is in the distal position of the reduced pressure configuration, the area around the front end (20) of the lower punch unit (4) is located at a first expansion level (24) corresponding to the maximum downward vertical reduced pressure expansion of the unsintered body (8) to be formed. - The punch tunnel (18) includes a first side surface portion (22) located in at least one (1) of the die sections, the first side surface portion (22) having a vertical range from a first pressing level (23) downward to a first expansion level (24), - The first side surface portion (22) is inclined such that, when viewed in a vertical cross-section of the punch tunnel (18), it is inclined downward by an angle β greater than or equal to the angle α of the adjacent inclined lower surface (13) of the unsintered body (8) to be formed, and away from the pressing axis (6). - A split die press tool characterized in that the punch tunnel (18) comprises a second side surface portion (25) located in at least one (1) of the die sections, the second side surface portion (25) is perpendicularly aligned with the first side surface portion (22), and has a vertical range from a first expansion level (24) downward to a first suppression level (27), and at the first suppression level (27), the horizontal distance to the periphery of the adjacent front end of the lower punch unit (4) is less than the horizontal distance at the first expansion level (24).

2. The dividing die pressing tool according to claim 1, wherein when at least one die section (1) is in the pressing position, the horizontal distance to the perimeter (20) of the adjacent front end of the lower punch unit (4) at the first suppression level (27) is less than 20 μm.

3. The split die press tool according to claim 1, wherein the vertical distance (39) from the first expansion level (24) to the first suppression level (27) is a maximum of 1 mm.

4. The split die press tool according to claim 1, wherein the vertical distance (39) from the first expansion level (24) to the first suppression level (27) is at least 0.05 mm.

5. The split die pressing tool according to claim 1, wherein the vertical distance (38) from the first pressing level (23) to the first expansion level (24) is at least 0.1 mm.

6. The split die press tool according to claim 1, wherein the angle β is 2 to 35°.

7. The dividing die press tool according to claim 1, wherein the angle β of the first side surface portion (22) is equal to the angle α.

8. The split die press tool according to claim 1, wherein the second lateral surface portion (25) includes an upper portion (30), the upper portion (30) extending downward from a first expansion level (24) to a first relaxation level (31) in the same direction as the first lateral surface portion (22).

9. The split die press tool according to claim 8, wherein the second lateral surface portion (25) includes a lower portion (32), the lower portion (32) extending downward from a first relaxation level (31) to a first suppression level (27), and is inclined downward and toward the pressing axis (6) at an angle γ of at least 5° and up to 45° when viewed in a vertical cross-section of the punch tunnel (18).

10. The split die press tool according to claim 1, wherein when the lower punch unit (4) is in the distal position of the filled position, the area around the front end (20) of the lower punch unit (4) is located at a filled level (35) below the first suppression level (27).

11. The punch tunnel (18) includes a bottom side surface portion (37) located in at least one (1) of the die sections, the bottom side surface portion (37) is perpendicularly aligned with the second side surface portion (25), and has a vertical range from a first suppression level (27) downward to a filling level (35), - The split die press tool according to claim 10, wherein at each level between the first suppression level (27) and the filling level (35), the horizontal distance from the bottom side surface portion (37) to the perimeter (20) of the adjacent front end of the lower punch unit (4) is the same.

12. - When the upper punch unit (3) is in the pressing position, the area around the front end (20) of the upper punch unit (3) is located at the second pressing level (44). - When the upper punch unit (3) is in the distal position of the reduced pressure configuration, the area around the front end (20) of the upper punch unit (3) is located at a second expansion level (47) corresponding to the maximum upward vertical reduced pressure expansion of the unsintered body (8). - The punch tunnel (18) includes a third side surface portion (42) located in at least one (1) of the die section, the third side surface portion (42) being perpendicularly aligned with the first and second side surface portions (22, 25), and having a vertical range from a second pressing level (44) upward to a second expansion level (47), - The third side surface portion (42), when viewed in a vertical cross-section of the punch tunnel (18), is inclined upward by an angle β greater than or equal to the angle α of the adjacent upper inclined surface (12) of the unsintered body (8) to be formed, and away from the pressing axis (6). - The split die press tool according to claim 1, wherein the punch tunnel (18) includes a fourth side surface portion (43) located in at least one (1) of the die sections, the fourth side surface portion (43) is perpendicularly aligned with the third side portion (42) and has a vertical range from a second expansion level (47) upward to a second suppression level (46), and at the second suppression level (46), the horizontal distance to the perimeter (20) of the adjacent front end of the upper punch unit (3) is less than the horizontal distance at the second expansion level (47).

13. The split die pressing tool according to claim 12, wherein the third side surface portion (42) is symmetrical with respect to the first side surface portion (22) and the fourth side surface portion (43) is symmetrical with respect to the second side surface portion (25) across the horizontal axis between the first pressing level (23) and the second pressing level (44).

14. The powder further contains the powder which can be pressed onto the unsintered body (8) in a compressed state, and the unsintered body (8) in a compressed state can be reduced in pressure to form the unsintered body (8), - The unsintered body (8) has a top edge (9), a bottom edge (10), and a side surface (11) connecting the top edge (9) and the bottom edge (10), - The top edge (9) is associated with an adjacent inclined upper surface (12) on the side surface (11), and the bottom edge (10) is associated with an adjacent inclined lower surface (13) on the side surface (11), and both inclined surfaces (12, 13) have a positive nominal angle α. The split die pressing tool according to claim 1.

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