Die for a press and method for producing a green body by means of a press

Abstract

The invention relates to a die for arrangement in a press, wherein the die extends along an axial direction between two end faces and forms an inner peripheral surface between the end faces, wherein the die extends from the inner peripheral surface along a radial direction toward an outer peripheral surface and toward at least one centering surface that is disposed in the radial direction on a first diameter, wherein the die has a pressing zone that is spaced apart from the end faces and, in the vicinity of the pressing zone, the die has a greater maximum first stiffness, at least relative to zones of the die that are arranged on the end faces, compared to a pressing force acting on the inner peripheral surface in a direction of a normal vector, and wherein the maximum first stiffness is at least 10% greater than a minimum second stiffness that is present in at least one zone that is arranged on one of the end faces.

Claims

1. A die for arrangement in a press, wherein the die extends along an axial direction between a first end face and a second end face and forms an inner peripheral surface between the end faces, wherein the die extends from the inner peripheral surface along a radial direction toward an outer peripheral surface and toward at least one centering surface that is disposed in the radial direction on a first diameter, wherein the die has a pressing zone that is spaced apart from the end faces and the die has a first stiffness in the vicinity of the pressing zone that differs along a peripheral direction and having a maximum first stiffness greater in comparison to zones of the die that are arranged on the end faces that are not in the pressing zone and wherein the maximum first stiffness is at least 10% greater than a minimum second stiffness that is present in at least one zone that is arranged on one of the end faces.

2. The die as set forth in claim 1, wherein the at least one centering surface is arranged in the pressing zone along the axial direction.

3. The die as set forth in claim 1, wherein the at least one centering surface has a first height along the axial direction, the first height corresponding to no more than 80% of a shortest distance between the end faces.

4. The die as set forth in claim 1, wherein the die, along the radial direction between the inner peripheral surface and the first diameter, has at least one cross section that is reduced at least in the axial direction or connecting regions that are arranged at a distance from one another in the peripheral direction.

5. The die as set forth in claim 4, wherein the connecting regions are additionally spaced apart from one another in the axial direction.

6. The die as set forth in claim 1, wherein a second diameter is arranged between the inner peripheral surface and the first diameter, and wherein a cross-sectional area of the die that is present on the second diameter corresponds to no more than 80% of the inner peripheral surface.

7. The die as set forth in claim 1, wherein a plurality of centering surfaces are arranged on the first diameter, with the centering surfaces being arranged so as to be spaced apart from one another along a peripheral direction.

8. The die as set forth in claim 1, wherein the at least one centering surface is embodied so as to extend circumferentially in a peripheral direction.

9. The die as set forth in claim 1, wherein the die has at least one retaining portion that is arranged so as to be spaced apart in the axial direction from the at least one centering surface.

10. A method for manufacturing at least one green compact with a press, wherein the press has at least one die as set forth in claim 1 and at least one punch that can travel along the axial direction via an end face of the die into a receptacle for the green compact that is formed by the inner peripheral surface, the method comprising at least the following steps: a) placing a powder in the receptacle; b) moving the at least one punch in the die along the axial direction and compressing the powder into a green compact in the pressing zone; c) demolding the green compact from the die via an end face of the die.

11. The method as set forth in claim 10, wherein the green compact is removed from the die in step c) via a first zone that is arranged on the first end face, the maximum first stiffness being at least 10% greater than at least the minimum second stiffness that is present in the first zone.

12. A die for arrangement in a press, wherein the die extends along an axial direction between a first end face and a second end face and forms an inner peripheral surface between the end faces, wherein the die extends from the inner peripheral surface along a radial direction toward an outer peripheral surface and toward at least one centering surface that is disposed in the radial direction on a first diameter, wherein the die has a pressing zone that is spaced apart from the end faces and the die has a first stiffness in the vicinity of the pressing zone and having a maximum first stiffness greater in comparison to zones of the die that are arranged on the end faces that are not in the pressing zone and wherein the maximum first stiffness is at least 10% greater than a minimum second stiffness that is present in at least one zone that is arranged on one of the end faces that is not in the pressing zone; wherein the die has connecting regions spaced from each other at least in a circumferential direction along the radial direction between the inner peripheral surface and the first diameter; the die being made by a manufacturing process such as turning, milling, sawing, drilling, grinding, wire cutting, die sinking, and hard milling or a shrink ring being produced by additive processes for the production of three-dimensional structures from powdered starting material by sintering.

13. The die as set forth in claim 12, wherein the connecting regions are additionally arranged at a distance from one another in the axial direction.

14. A die for arrangement in a press, wherein the die extends along an axial direction between a first end face and a second end face and forms an inner peripheral surface between the end faces, wherein the die extends from the inner peripheral surface along a radial direction toward an outer peripheral surface and toward at least one centering surface that is disposed in the radial direction on a first diameter, wherein the die has a pressing zone that is spaced apart from the end faces and the die has a first stiffness in the vicinity of the pressing zone and having a maximum first stiffness greater in comparison to zones of the die that are arranged on the end faces that are not in the pressing zone and wherein the maximum first stiffness is at least 10% greater than a minimum second stiffness that is present in at least one zone that is arranged on one of the end faces that is not in the pressing zone; wherein the die, along the radial direction between the inner peripheral surface and the first diameter at a second diameter has at least one reduced cross-section at least in the axial direction, wherein between the second diameter and the first diameter a further cross-sectional area is provided which is larger than that one cross-sectional area present at the second diameter.

15. A die for arrangement in a press, wherein the die extends along an axial direction between a first end face and a second end face and forms an inner peripheral surface between the end faces, wherein the die extends from the inner peripheral surface along a radial direction toward an outer peripheral surface and toward at least one centering surface that is disposed in the radial direction on a first diameter, wherein the die has a pressing zone that is spaced apart from the end faces and the die has a first stiffness in the vicinity of the pressing zone and having a maximum first stiffness greater in comparison to zones of the die that are arranged on the end faces that are not in the pressing zone and wherein the maximum first stiffness is at least 10% greater than a minimum second stiffness that is present in at least one zone that is arranged on one of the end faces that is not in the pressing zone; wherein the die has connecting regions spaced from each other at least in a circumferential direction along the radial direction between the inner peripheral surface and the first diameter, wherein the connecting portions are additionally spaced from each other in the axial direction.

16. The die as set forth in claim 15, wherein the first stiffness differs along a circumferential direction.

17. A method for manufacturing at least one green compact with a press, wherein the press has at least one die as set forth in claim 12 and at least one punch that can travel along the axial direction via an end face of the die into a receptacle for the green compact that is formed by the inner peripheral surface, the method comprising at least the following steps: a) placing a powder in the receptacle; b) moving the at least one punch in the die along the axial direction and compressing the powder into a green compact in the pressing zone; c) demolding the green compact from the die via an end face of the die.

18. A method for manufacturing at least one green compact with a press, wherein the press has at least one die as set forth in claim 14 and at least one punch that can travel along the axial direction via an end face of the die into a receptacle for the green compact that is formed by the inner peripheral surface, the method comprising at least the following steps: a) placing a powder in the receptacle; b) moving the at least one punch in the die along the axial direction and compressing the powder into a green compact in the pressing zone; c) demolding the green compact from the die via an end face of the die.

19. A method for manufacturing at least one green compact with a press, wherein the press has at least one die as set forth in claim 15 and at least one punch that can travel along the axial direction via an end face of the die into a receptacle for the green compact that is formed by the inner peripheral surface, the method comprising at least the following steps: a) placing a powder in the receptacle; b) moving the at least one punch in the die along the axial direction and compressing the powder into a green compact in the pressing zone; c) demolding the green compact from the die via an end face of the die.

Description

(1) The invention and the technical environment will be explained in greater detail with reference to the figures. It should be noted that the invention is not intended to be limited by the embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the features explained in the figures and to combine them with other components and insights from the present description and/or figures. In particular, it should be pointed out that the figures and, in particular, the illustrated proportions are only schematic. Same reference symbols designate same objects, so that explanations of other figures can be consulted where necessary. In the drawing:

(2) FIG. 1 shows a known die in a sectional view from the side;

(3) FIG. 2 shows the die according to FIG. 1 in a perspective view;

(4) FIG. 3 shows a die according to a first design variant in a perspective view;

(5) FIG. 4 shows a top view of the die according to FIG. 3;

(6) FIG. 5 shows a side view of the die according to FIGS. 3 and 4;

(7) FIG. 6 shows the die according to FIGS. 3 to 5 in a sectional view from the side;

(8) FIG. 7 shows a die according to a second design variant in a perspective view;

(9) FIG. 8 shows a die according to a third design variant in a perspective view;

(10) FIG. 9 shows a die according to a fourth design variant in a perspective view;

(11) FIG. 10 shows a die according to a fifth design variant in a perspective view;

(12) FIG. 11 shows the die according to FIG. 10 in a sectional view from the side;

(13) FIG. 12 shows the die according to FIGS. 10 and 11 in a sectional view from the side;

(14) FIG. 13 shows a die according to a sixth design variant in a perspective view;

(15) FIG. 14 shows a die according to a seventh design variant in a perspective view; and

(16) FIG. 15 shows a die according to an eighth design variant in a perspective view.

(17) FIG. 1 shows a known die 1 in a sectional view from the side. FIG. 2 shows the die 1 according to FIG. 1 in a perspective view. FIGS. 1 and 2 are described together below.

(18) The die 1 comprises a so-called shrink ring 23, a core 24 being arranged within the shrink ring 23 that then forms the inner peripheral surface 6 of the die 1. For one, the inner peripheral surface 6 of the die 1 forms the receptacle for the powder and the green compact 25 to be produced. An upper punch 26 of the press 2 can travel along an axial direction 3 into the die 1 via an upwardly open end face 4 of the die 1. The upper punch 26 slides along the inner peripheral surface 6 of the die 1 and increasingly compresses the powder. A lower punch 27 is additionally provided here which (during the assembly of the die 1) travels along the axial direction 3 into the die 1 via a downwardly open second end face 5 of the die 1 and moves up and down within the die 1 until the disassembly of the die 1. The powder is thus pressed between the upper punch 26 and the lower punch 27 by pressing forces 14 into a green compact 25, the inner peripheral surface 6 of the die 1 defining a side contour of the green compact 25 in particular.

(19) The die 1 has a collar 28 on an outer peripheral surface 8 via which the die 1 can be received and clamped in the press 2. The collar 28 extends in a radial direction 7 beyond the outer peripheral surface 8, so that the die 1 can be placed onto a support 29 of the press 2. The die 1 is cylindrical, the cylindrically shaped outer peripheral surface 8 being received via a radial clearance in the press 2, thus enabling a centering of punches 26, 27 and die 1—i.e., a coaxial arrangement of punches 26, 27 and die 1.

(20) The die 1 has a first zone 12 on the first end face 4 and a second zone 13 on the second end face 5, each of which is designated as a punch guide zone 30. A pressing zone 11 is present at a distance from the end faces 4, 5 and adjacent to the punch guide zones 30. The pressing zone 11 is the area in which the powder is compressed with the greatest pressing force 14. The pressing zone 11 is clearly defined in the die 1 and bounded along the axial direction 3. Furthermore, a demolding zone 31 is present on the first end face 4—i.e., an area of the die 1 through which the completely pressed green compact 25 is pushed out of the die 1 (demolded) and provided for removal from the press 2. During the pressing of the powder, an equally strong bonding pressure is applied to the inner peripheral surface 6 of the die 1. The inner peripheral surface 6 of the die 1 is elastically expanded in the direction of the normal vector 32. This expansion in the pressing zone 11 now results in strong frictional forces during demolding. These frictional forces extend into the demolding zone 31, since the die 1 is usually cylindrical and therefore has a substantially constant stiffness (i.e., a resistance to an elastic expansion in the direction of the normal vector 32 that is essentially unchanging) along the axial direction 3. This expansion only in the pressing zone 11 of the die 1 also has the effect that the green compact 25 cannot be produced with dimensional accuracy. A conicity of the green compact 25 can occur during demolding of the green compact 25. In that case, the die 1 rebounds in the pressing zone 11 as demolding progresses, so that the green compact 25 is increasingly constricted at its lower end and consequently takes on an overall conical shape.

(21) FIG. 3 shows a die 1 according to a first design variant in a perspective view. FIG. 4 shows the die 1 according to FIG. 3 in a top view. FIG. 5 shows a side view of the die according to FIGS. 3 and 4. FIG. 6 shows the die 1 according to FIGS. 3 to 5 in a sectional view from the side. FIGS. 3 to 6 are described together below.

(22) The die 1 extends along an axial direction 3 between two end faces 4, 5 and forms an inner peripheral surface 6 between the end faces 4, 5. The die 1 extends from the inner peripheral surface 6 along a radial direction 7 toward an outer peripheral surface 8 and toward three centering surfaces 10 that are disposed in the radial direction 7 on a first diameter 9. The die 1 has a pressing zone 11 that is spaced apart from the end faces 4, 5. In the vicinity of the pressing zone 11, the die 1 has a greater maximum first stiffness (i.e., the greatest first stiffness present there), at least relative to the zones 12, 13 that are arranged on the end faces 4, 5, compared to a pressing force 14 acting on the inner peripheral surface 6 in the direction of the normal vector 32.

(23) The die 1 is provided for a powder press for the purpose of manufacturing green compacts 25. Sinterable green compacts 25 are manufactured with the press 2 that can be sintered after the pressing process. Metallic or also ceramic powders can be pressed into green compacts 25 in the die 1.

(24) The die 1 comprises a so-called shrink ring 23, a core 24 being arranged within the shrink ring 23 that then forms the inner peripheral surface 6 of the die 1. For one, the inner peripheral surface 6 of the die 1 forms the receptacle for the powder and the green compact 25 to be produced. An upper punch 26 of the press 2 can travel along an axial direction 3 into the die 1 via an upwardly open end face 4 of the die 1. The upper punch 26 slides along the inner peripheral surface 6 of the die 1 and increasingly compresses the powder. A lower punch 27 is additionally provided here which moves into the die 1 via a downwardly open second end face 5 of the die 1 along the axial direction 3. The powder is thus pressed between the upper punch 26 and the lower punch 27 by pressing forces 14 into a green compact 25, the inner peripheral surface 6 of the die 1 defining a side contour of the green compact 25 in particular. The pressing force 14 is introduced into the powder by means of the punches 26, 27. The pressing force 14 is maintained over the punches 26, 27 and the die 1. At the same time, the pressing force 14 acts on the die 1 in the direction of the normal vector 32.

(25) The die 1 has punch guide zones 30 on its respective end faces 4, 5 as zones 12, 13, with a pressing zone 11 being present at a distance from the end faces 4, 5 and adjacent to the punch guide zones 30. It is in the pressing zone 11 that the powder is compressed with the greatest pressing force. The pressing zone 11 is defined by the region along the axial direction 3 in which the powder is arranged during the application of the greatest pressing force 14 (see FIG. 1).

(26) Furthermore, a demolding zone 31—i.e., a first zone 12 of the die 1 through which the green compact 25 is pushed out of the die 1 (demolded) and provided for removal from the press 2—is present at least on the first end face 4.

(27) The die 1 is aligned in the press 2 relative to the punches 26, 27 by means of the centering surfaces 10. The centering surfaces 10 lie on the largest first diameter 9 of the die 1—that is, the die 1 extends only within the first diameter 9.

(28) In the die 1 proposed here, it has been assumed that a maximally high stiffness should be present only in the vicinity of the pressing zone 11. By virtue of this high first stiffness, dimensionally accurate production of the green compact 25 by the press 2 and the pressing process can be ensured. On the other hand, a second stiffness in the vicinity of the end faces 4, 5 of the die 1 can be designed to be substantially smaller, since a substantially lesser load acts on the die 1 in these regions (which are bounded in the axial direction 3) as a result of the pressing force (component) 14 acting in the direction of the normal vector 32.

(29) A majority of the material that is usually present in cylindrically shaped dies 1 (see FIGS. 1 to 3) can be saved due to the lesser second stiffness.

(30) The centering surfaces 10 are arranged exclusively in the pressing zone 11 along the axial direction 3.

(31) The centering surfaces 10 have a first height 16 along the axial direction 3, the first height 16 being smaller than a shortest distance 17 between the end faces 4, 5.

(32) The die 1 has at least one cross section 18 along the radial direction 7 between the inner peripheral surface 6 and the first diameter 9 that is reduced at least in the axial direction 3 or connecting regions 19 that are arranged at a distance from one another in the peripheral direction 15.

(33) The cross section 18 that is reduced in the axial direction 18 describes the shape of the die 1 at the end faces 4, 5 in the region between the inner peripheral surface 6 and the first diameter 9. A constriction of the shape of the die 1 is thus present here, meaning that the die 1 has a shorter distance 17 between the end faces 4, 5 in this region than in the vicinity of the inner peripheral surface 6.

(34) The connecting regions 19 describe the shape of the die 1 along the peripheral direction 15. Free spaces (i.e., spaces without material of the die 1) are present here between the inner peripheral surface 6 and the first diameter 9. Spokes are formed by the connecting regions 19 that connect the inner peripheral surface 6 to a centering surface 10 that is arranged on the first diameter 9.

(35) Three centering surfaces 10 are arranged here on the first diameter 9, with the centering surfaces 10 being arranged so as to be spaced apart from one another along the peripheral direction 15.

(36) In addition, the die 1 has a retaining portion 22 that is arranged so as to be spaced apart from the centering surfaces 10 in the axial direction 3.

(37) The retaining portion 22 is provided for the purpose of facilitating the handling of the die 1. The retaining portion 22 serves as a handle for manual handling of the die 1. In the present case, the retaining portion 22 is fastened to the die 1 by means of screws (see FIG. 4).

(38) In particular, the retaining portion 22 is arranged in the radial direction 7 between the inner peripheral surface 6 and the first diameter 9. The retaining portion 22 extends in the manner of a ring.

(39) In FIG. 6, the green compact 25 is arranged within the pressing zone 11. The green compact 25 is formed in step b) of the method in the pressing zone by compressing a powder. The greatest bonding pressure is reached in the pressing zone 11. In step c) of the method (not shown here), the green compact 25 is removed from the mold via the first zone 12 that is provided as the demolding zone 31, which is arranged on the first end face 4.

(40) FIG. 7 shows a die 1 according to a second design variant in a perspective view. Reference is made to the remarks in relation to FIGS. 3 to 6. Unlike the first design variant, the die 1 has additional free spaces or recesses in the vicinity of the connecting regions 19. The connection of the retaining portion 22 to the die 1 and to the shrink ring 23 is also set up differently here.

(41) FIG. 8 shows a die 1 according to a third design variant in a perspective view. Reference is made to the remarks in relation to FIGS. 3 to 6. Unlike the first design variant, the connecting regions 19 are additionally spaced apart from one another in the axial direction 3. Spokes are thus formed which are arranged in at least partially identical positions in the peripheral direction 15 but in different positions in the axial direction 3. In addition, the centering surface 10 is embodied so as to extend circumferentially in the peripheral direction 15.

(42) The connecting regions 19 can be used here as handles for the manual handling of the die 1.

(43) FIG. 9 shows a die 1 according to a fourth design variant in a perspective view. Reference is made to the remarks in relation to FIGS. 3 to 6 and to FIG. 8. Unlike FIG. 8, an additional circumferential intermediate ring is provided here between the inner peripheral surface 6 and the circumferential centering surface 10.

(44) FIG. 10 shows a die 1 according to a fifth design variant in a perspective view. FIG. 11 shows the die 1 according to FIG. 10 in a sectional side view, with the section running through the center axis of the die 1. FIG. 12 shows the die 1 according to FIGS. 10 and 11 in a sectional side view, with the section line running here so as to be laterally offset from the central axis. Reference is made to the remarks in relation to FIGS. 3 to 6 and to FIG. 8. In contrast to FIG. 8, a corrugated region is formed here which extends circumferentially in the peripheral direction 15 and has a cross section 18 that is substantially reduced in the axial direction.

(45) A second diameter 20 is arranged between the inner peripheral surface 6 and the first diameter 9, with a cross-sectional area 21 of the die 1 that is present on a second diameter 20 being substantially smaller than the inner peripheral surface 6. An additional cross-sectional area is provided between the second diameter 20 and the first diameter 9 that is greater than the cross-sectional area 21 present on the second diameter 20.

(46) Here, the centering surfaces 10, or the top and bottom side of the die 1, in the immediate vicinity of the centering surfaces 10 are used as collars 28 for clamping the die 1 in a receptacle (an adapter; only a support 29 of the receptacle is shown here) of the press 2.

(47) FIG. 13 shows a die 1 according to a sixth design variant in a perspective view. FIG. 14 shows a die 1 according to a seventh design variant in a perspective view. FIG. 15 shows a die 1 according to an eighth design variant in a perspective view. FIGS. 13 to 15 are described together below. Reference is made to the remarks in relation to FIGS. 3 to 6 and to FIG. 8. In contrast to FIG. 8, the inner peripheral surface 6 is not rotationally symmetrical here. Due to the shape of the inner peripheral surface 6 or of the receptacle for the powder to be compressed, the amount of pressing force 14 applied by means of the punches 26, 27 and acting on the inner peripheral surface 6 varies as a function of the position along the peripheral direction 15. It is for this reason that the die 1 is designed to have a different first stiffness along the peripheral direction 15. Here, the die 1 is designed to be rotationally symmetrical by an angular step of 180 angular degrees about an axis parallel to the axial direction 3. Such a configuration of the die 1, with a different first stiffness along the peripheral direction 15, is particularly expedient when non-rotationally symmetrical green compacts 25 (or green compacts 25 having a symmetry only when rotated 180 angular degrees) are being produced—for example, cuboid green compacts 25 as shown. By virtue of this special design variant of the die, asymmetrical green compacts 25 can be supported in an ideal manner, so that radially asymmetrical deformations of the die 1 and hence of the green compact 25 can be avoided.

LIST OF REFERENCE SYMBOLS

(48) 1 die 2 press 3 axial direction 4 first end face 5 second end face 6 inner peripheral surface 7 radial direction 8 outer peripheral surface 9 first diameter 10 centering surface 11 pressing zone 12 first zone 13 second zone 14 pressing force 15 peripheral direction 16 first height 17 distance 18 cross section 19 connecting region 20 second diameter 21 cross-sectional area 22 retaining portion 23 shrink ring 24 core 25 green compact 26 upper punch 27 lower punch 28 collar 29 support 30 punch guide zone 31 demolding zone 32 direction of the normal vector