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The present invention relates to a method of producing a metal powder compact having a top punch-driven drivable powder press drivable lower punch assembly and a die assembly which forms the mold cavity in which the metal powder is filled into said mold cavity and thereafter the upper die is molded to form the compact Stamp assembly and the lower punch assembly are pressed against each other, and to an apparatus for performing the method.
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With such methods, compacts of various shapes can be produced on the corresponding powder presses, which are hydraulically or mechanically drivable. Here, the corresponding powder in the mold, which is formed by a die assembly and by an upper and a lower punch assembly, filled, then the pressing operation is carried out, with the possibility of separate method of the individual stamp members of the lower punch assembly and / or the upper Stamp arrangement in the compact different gradations can be achieved. In this case, filling volume for the individual areas of the compact and the desired thickness of these areas of the finished pressed compact must be optimally matched to each other, so that a finished pressed compact over the entire body has a uniform material density.
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Now, if a compact having a complicated shape has to be produced, in which in particular transverse passages should also be provided, filling a mold in which transverse punches are arranged to reach these transverse passages is very difficult, and then in the finished pressed compact to achieve the required uniform material density.
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For producing such compacts having a relatively complicated shape, it is known that a plurality of bodies with simpler geometries are pressed individually, whereby the required quality of the individual Body is reached, after which these individual bodies are placed on each other before the sintering process and interconnected during sintering, which is achieved in that a connecting means, such as a solder, is introduced into the connection points. During the sintering process, these individual bodies connect to the desired shaped body.
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With this method, relatively complex bodies can be achieved with penetrations with the powder pressing process, the individual components of which this body is composed do not have very complex shapes. But in order to produce the individual components of the body to be produced, several powder molding machines are required, each one of these powder molding machines produces one of the components for the body. The investment, operating and maintenance costs for the powder press machines are correspondingly high. Since the individual components, from which then the desired body is assembled, can have very different dimensions, it is not possible to run all machines for the production of the individual components with the same stroke rates. As a result, certain components must be stored, which is undesirable because unsintered components are relatively easily damaged. In addition, this intermediate storage storage costs and a corresponding logistics costs result. For each of these components to be produced an individual pressing tool is necessary, which are expensive and must be maintained with the appropriate effort.
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In addition, it is necessary that these individual components must be provided and assembled before the sintering process with the connecting means, which requires additional effort, be it personal or by providing a corresponding automatic operating system. The joining of the individual components and in particular the application of the bonding agent on the different joints carries a quality risk in itself, a reduction in quality has an undesirable reduction in the strength of the finished body result.
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The object of the present invention is therefore to provide a method by which compacts with more complex shapes can be carried out in a pressing operation, in particular when these compacts must be provided with transverse openings, and with which compacts can be obtained, the desired quality which can save investment, operating and maintenance costs.
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According to the invention, the solution of this object is achieved in that a lower part of the die assembly, which is in the filling position is filled with a first filling shoe with metal powder, that after the filling of the lower part of the die assembly, an upper part of the die assembly with retracted into the mold cavity Cross stamping is lowered onto the lower part of the die assembly, that the lowered on the lower part of the die assembly upper part of the die assembly is filled with a second filling shoe with powder that executed after the completion of the filling process, the pressing operation and the compact is pressed, then that Querstempel be moved back from the mold cavity filled by the compact and from the compact and that subsequently the upper part of the die assembly and the lower part of the die assembly from the compact, which is held by the punch assemblies are withdrawn.
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With this method, metal powder compacts of relatively complex shape, particularly with transverse breakthroughs, can be made in a single press operation, requiring multiple machines for the manufacture of individual components for that compact, resulting in significant cost savings. These savings also have a direct impact on the selling price of the corresponding manufactured products. Only one tool is required to produce these pellets, which can reduce setup time, which increases the efficiency of the corresponding powder press. In addition, this method ensures that the quality of the compacts produced meets the desired requirements, in particular it ensures that the material density in the entire compact is identical and therefore optimal.
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Advantageously, after lowering the upper part of the die assembly with retracted into the mold cavity transverse punches on the lower part of the die assembly at least a portion of the lower punch assembly is raised in each case by a predetermined amount, whereby the areas that lie under the transverse punches in the mold cavity be filled with powder. As a result, the optimum quality of the compacts is achieved.
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Advantageously, after the completion of the pressing operation and before retracting the transverse punch from the mold cavity filled by the compact and from the compact of the compact by a corresponding return stroke of the punch assemblies relaxed, the withdrawal of the transverse punch of the compact is facilitated, this also has on the quality of the compact an influence.
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Advantageously, to perform the peel-off operation, first the upper part of the die assembly is withdrawn by the process from the lower part of the die assembly away from the compact while the compact is held by the upper die assembly, and thereafter the lower part of the die assembly is machined by moving the lower part of the die assembly Die assembly removed from the upper part of the die assembly away from the compact, while the compact is held by the lower punch assembly. This achieves optimum shaping of the compact.
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A further object of the invention is to design a device for carrying out said method in such a way that this method can be carried out in an optimum manner, which according to the invention takes place in that the first filling shoe is displaceably arranged along a first filling level for the lower part of the die arrangement, and that the second filling shoe is slidably disposed along a second filling level for the upper part of the die assembly. With this arrangement, the mold cavity can be optimally filled in two stages.
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Advantageously, the transverse punches projecting into the upper part of the die arrangement are, via drives, moved from the position extended from the mold cavity into a position retracted into the mold cavity Position and vice versa brought, whereby, since these drives are controlled by the machine control, an optimal pressing operation is guaranteed.
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Advantageously, the drives for the transverse punch are hydraulically actuated, whereby a simple control of these drives can be done.
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A further advantageous embodiment of the device is that the upper punch assembly and / or the lower punch assembly is constructed of one or more punch elements, depending on what is to be produced for a compact.
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In order to achieve optimum shaping and pressing of the compact with the desired quality, the stamp elements of the upper punch assembly and the punch members of the lower punch assembly are each separately driven.
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An inventive method and an embodiment of the apparatus for performing the method for producing a compact of metal powder will be explained in more detail by way of example with reference to the accompanying drawings.
It shows,
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Fig. 1A to Fig. 1C Spatial representations and a sectional view of an example of a compact, as it can be produced by the inventive method;
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Fig. 2 in a spatial representation and partly in section, the upper punch assembly and the lower punch assembly with the die assembly and the filling shoes, which for the production of the compact according to the FIGS. 1A to 1C serve;
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FIGS. 3 to 15 in a schematic representation of the upper punch assembly, the lower punch assembly, the die assembly and the Filling shoes each shown in a position during the performance of a pressing operation; and
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Fig. 16A and Fig. 16B a schematic representation of a hydraulic drive for the displacement of a cross bar, arranged on a die plate.
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In the FIGS. 1A to 1C shows an example of a compact, as it can be produced by the method according to the invention and a device designed to carry out this method. This compact 1 has a lower cylindrical part 2 and an attached upper cylindrical part 3, which has a smaller diameter than the cylindrical part 2. In the lower cylindrical part 2 is inserted a coaxial hollow cylindrical recess 4, the compact 1 is by a coaxial penetrated cylindrical bore 5. In the upper cylindrical part 3, four radially extending transverse openings 6 are provided, which open into the cylindrical bore 5 and which have a rectangular cross-sectional shape. Furthermore, this compact 1 has four further holes 7, which are aligned parallel to the cylindrical bore, from which holes 7 each have a corresponding transverse opening 6 is penetrated.
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According to the prior art, now this compact would be 1, as in the FIGS. 1A to 1C has been pressed in two parts, namely the lower cylindrical part 2 on its own and the upper cylindrical part 3 on its own, the separation of these two parts being placed in a plane formed by the lower planes of the transverse openings 6, as indicated by the dot-dash line 8 in FIG Fig. 1C is shown. The two pressed parts would then, as previously described, be soldered at the joints and would have been joined together during the sintering process.
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In again FIGS. 1A to 1C shown compact 1 can be produced in a single pressing operation, will now be described below. Out Fig. 2 an upper punch assembly 9, a lower punch assembly 10, and a die assembly 11 are shown. These arrangements 9 to 11 are used in a known, not shown manner in a known powder press, of course, and preferably these arrangements 9 to 11 used in a known adapter, which can then be used according to the powder press. The upper punch assembly 9 comprises an inner punch 12 and a punch ring 13. The inner punch 12 and the punch ring 13 are separately driven by the powder press. The inner punch 12 is equipped on the die side with a centrally arranged blind bore 14. The inner punch 12 additionally has four through holes 15, which run parallel to the punch axis, represented by the dot-dash line 19.
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The lower punch assembly 10 is composed of the following punch elements: an outer lower punch 16, an inner lower punch 17 and a central mandrel 18. The outer lower punch 16, the inner punch 17 and the central mandrel 18 are hollow cylindrical or cylindrical, and coaxial with the press axis 19 arranged. As further punch elements four pins 20 are provided which are slidably inserted into the inner lower punch 17 such that they are aligned with the holes 15 of the upper punch assembly 9. The pins 20 inserted into the inner lower punch 17 are, like the outer lower punch 16, the inner lower punch 17 and the central mandrel 18 drivable separately in a known manner by the powder press.
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The die assembly 11 comprises an upper part 21 and a lower part 22. The lower part 22 is arranged coaxially around the lower punch assembly 10, also along the pressing axis 19 in a known, not shown manner driven by the powder press. The upper part 21 of the die assembly is formed as a hollow cylindrical ring, in each of which four transverse punches 23 are mounted radially displaceable in corresponding recesses. Each of these transverse punches 23 is slidably drivable by a hydraulic drive 24, which hydraulic drive 24 is shown only schematically, a detailed description follows later.
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A plate 25, the upper surface of which is flush with the annular surface of the lower part 22 of the die assembly, forms a plane, on which an only schematically illustrated first filling shoe 26 is arranged movable. Another plate 27 is disposed at the level of the annular surface of the upper part 21 of the die assembly 11 so that its surface also forms a plane with this annular surface. On this further plate 27, a second filling shoe 28 is also slidably disposed, which is also shown only schematically.
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Also off Fig. 2 It can be seen a finished pressed compact 1, as in the Fig. 1A to 1C is shown, which rests on the lower punch assembly 10 and is located in the ejection position. Such compacts 1 can by the arrangement, as shown in Fig. 2 is shown pressed.
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To perform a pressing operation, the upper punch assembly 9 and the lower punch assembly 10 are in the open filling position, as is apparent Fig. 3 is apparent. The upper part 21 of the die with the further plate 27 and the second filling shoe 28 are in the raised positions. The outer lower punch 16 and the inner lower punch 17 are moved downwards so far that within the lower part 22 of the die, a lower part of the mold cavity 29 is formed, which can accommodate the exact predetermined volume of powder. The pins 20 and the central mandrel 18 of the lower punch assembly 10 are so far advanced that its surface is flat with the filling plane formed by the plate 25, in which there is also the circular cylindrical surface of the lower part 22 of the die.
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The first filling shoe 26 is moved along this plane formed by the plate 25 and passes over the mold cavity 29 located within the lower part 22 of the die and fills it completely with powder.
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The first filling shoe 26 is then moved back along the plate 25 as shown in FIG Fig. 4 is shown. The lower part 22 of the die assembly with the plate 25 is slightly raised, at the same time the pins 20 by a predetermined amount and the central mandrel 18 by a predetermined Mass raised, driven by the individual drives of the powder press.
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After that, as in Fig. 5 is shown, the upper part 21 of the die assembly with the further plate 27 and the second filling shoe 28 moved down, arranged in the upper part 21 of the die assembly transverse punches 23 are retracted in the upper part of the mold cavity 29 state, carried out by the hydraulic drives 24th ,
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The upper part 21 of the die assembly is lowered together with the further plate 27 and the second filling shoe 28 until it rests on the lower part 22 of the die assembly, as is apparent from Fig. 6 is apparent. In this case, the pins 20 penetrate the corresponding holes provided in the transverse punches 23.
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The outer lower punch 16 and the inner lower punch 17 are then raised by a predetermined amount until the surface of the already filled powder in the lower part of the mold cavity 29 at least to the underside of the transverse punch 23 abuts, so that the areas below the transverse punch 23 in the lower part of the mold cavity 29 are completely filled with powder, the powder which is located above the outer lower punch 16 is already slightly pressed by abutment against the upper part 21 of the die assembly. At the same time, the pins 20 are moved so that their front surface is flat with the plane formed by the further plate 27, accordingly, the central mandrel 18 is moved to the same level as that Fig. 7 is apparent.
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Now, the upper portion of the mold cavity 29 can be filled with powder, for which purpose the second filling shoe 28 is moved along the plate 27 via the upper part 21 of the die assembly, as can be seen from Fig. 8 is apparent. The upper region of the mold cavity 29 is completely filled with the powder.
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How out Fig. 9 can be seen, then the second filling shoe 28 from the filling of the region of the upper part 21 of the die assembly scaled back. The upper punch assembly 9 is moved down until the punch ring 13 comes to rest on the surface of the upper part 21 of the die assembly and the surface of the inner punch 12 closes the mold cavity 29 and rests on the filled powder.
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Then the actual pressing process can be carried out. How out Fig. 10 As can be seen, the inner punch 12 of the upper die assembly 9, the outer die 16 and the inner die 17 are moved against each other, each die travels in a known manner a precisely predetermined feed path during a certain time interval. The pins 20 are in this case moved so that they penetrate into the holes 15 of the inner punch 12. The central mandrel 18 is also moved so that it projects into the blind bore 14 of the inner punch 12. Of course, the pressing forces of the individual punches are measured here in a known manner.
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After the pressing operation has been completed and the compact 1 is formed, the pins 20 are completely withdrawn from the compact 1 and the transverse punches 23. Before now the transverse punches 23 are withdrawn via the hydraulic drives 24 from the compact, the compact 1 is slightly relieved by a predetermined amount, which is achieved by corresponding withdrawal movements of the upper punch 9, the outer lower punch 16 and the inner lower punch 17.
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Thereafter, the transverse punches 23 are pulled out of the compact 1 via the hydraulic drives 24, as shown in FIG Fig. 12 is shown, also raised the punch ring thirteenth
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After that, how will off Fig. 13 it can be seen, raised the upper part 21 of the die assembly with the further plate 27 and the second filling shoe 28 and the hydraulic drives 24 for the transverse punches 23 and deducted from the compact 1, while the stamp the compact 1 on the top and bottom still hold.
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Subsequently, the lower part 22 of the die assembly with the plate 25 and the first filling shoe 26 is moved downwards with respect to the punch assemblies, the lower part 22 of the die assembly is thus removed from the compact 1, which is further held by the punches, as shown in FIG Fig. 14 is shown.
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In a last step, the upper punch assembly 9 moves back to the raised position, the outer lower punch 16 is advanced so far that it comes to lie with the surface of the inner lower punch in a plane, the compact 1 is ejected, as in Fig. 15 is shown. The finished pressed compact 1 is then free on the outer die 16 and can be carried away in a known manner, which can for example be done automatically via a robot, the pressing process is then completed, the lower punch assembly 10 is moved back to the filling position, as in Fig. 3 is shown, the press is ready to carry out another pressing operation.
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Of course, with correspondingly designed powder presses and moldings can be made with a different shape, the configuration of the upper punch assembly 9 and the lower punch assembly 10 can be configured differently by appropriate selection of number and shape of stamp elements, in particular, the upper punch assembly 9 may also have a plurality of punch elements , depending on the shape of the compact to be produced. It would even be conceivable that even a central part of a die is used, so that the die would be in three parts and three Füllvorgangszyklen could be performed with the appropriate design of the device, which even in this middle die even cross slide could be attached.
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By this method, a great flexibility of the design of the moldings to be produced is achieved.
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The Figures 16A and 16B show the die plate 30 for receiving the corresponding upper part 21 of the die assembly. At this die plate 30 of the hydraulic drive 24 for the transverse punch, not shown 23 attached. This hydraulic drive 24 has a piston rod 31 in a known manner, with attached thereto piston 32, which are acted upon in the cylinder 33 on both sides with pressure medium and thus can be moved back and forth. In addition, guide and coupling elements 34 are attached to the hydraulic drive 24, to which the respective transverse punch 23 can be coupled, and is correspondingly displaceable. This hydraulic drive 24 is connected to the hydraulic unit of the powder press, and is controlled in a known manner via the machine control. In the Figures 16A and 16B If only one hydraulic drive 24 is shown, four hydraulic drives 24 are of course arranged on the corresponding die plate 30 for producing the compact 1 according to the previously described method.
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Of course, it is also conceivable to use other drives instead of the hydraulic drives for moving the transverse punches, for example mechanical, depending on the powder press type.
