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(11) | EP 4 480 606 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | MACHINE FOR PRESSING METAL POWDERS |
| (57) The machine (1) for pressing metal powders comprises: - at least one forming die (2) provided with a through drilling defining at least one working surface (3) and developing along an axis of work (A); - at least one lower punch (4) associated movable with the through drilling along the axis of work (A) and provided with a contact surface (5) facing upwards and defining, with the working surface (3), a pressing cavity (7) adapted to contain a metal powder; - at least one upper punch (8) arranged on top of the forming die (2), movable along the axis of work (A) in the through drilling and provided with a pressing surface (9) adapted to close the pressing cavity (7) and to compress the metal powder to obtain a compacted component (C); where the lower punch (4) comprises dispensing means (11) adapted to dispense a lubricating agent into the pressing cavity (7) and where the machine (1) comprises a system for feeding the lubricating agent to the dispensing means (11). |
Technical Field
Background Art
[0002] In the industry of metal mechanical component manufacturing, metal powder sintering equipment is known.
[0003] Typically, such equipment comprises at least a machine for pressing metal powders, which comprises a forming cavity, within which the metal powder to be compacted is placed, and an upper punch which is movable to fit within the forming cavity and to exert a pressing force on the powder itself to obtain a compacted body.
[0004] The compacted body is then extracted from the forming cavity by means of a lower punch adapted to push the compacted body itself outwards. Depending on the conformation of the metal part to be obtained, the lower punch may be composed of one or more parts which can be assembled to each other.
[0005] At this point, the compacted body can be transferred to further heating machines that heat the metal particles and form the sintered component.
[0006] The pressing process involves lubrication of the forming cavity which prevents metal powder particles from sticking to the cavity surfaces and could result in the formation of a sintered component which does not conform to design specifications or hinder subsequent pressing operations.
[0007] Lubrication can be carried out indirectly by adding a lubricating agent to the metal powder. In this way, the insertion of the powder into the forming cavity also results, at the same time, in the lubrication of the cavity itself. The presence of the lubricating agent also promotes the flow of the powder and promotes the packing thereof.
[0008] This methodology may however interfere with the sintering process. In fact, the presence of the lubricating agent dispersed among the particles may make the compression of the powder less effective resulting in lower mechanical strength of the sintered component.
[0009] In addition, heating the powder can cause degradation of the lubricating agent with generation of toxic fumes and residual impurities in the sintered component, which in turn affect the mechanical strength of the sintered component.
[0010] Because of these drawbacks, a known type of pressing machine involves direct lubrication of the cavity, that is, by direct application of a lubricating agent to the walls of the forming cavity.
[0011] This type of machine is provided with a dispensing device, of the type e.g. of a robotic arm, adapted to distribute the lubricant into the forming cavity before the powder has been inserted.
[0012] In detail, as a result of compaction, the compacted body is extracted from the forming cavity by means of the lower punch. Once the latter returns to its initial position, thus defining the forming cavity, the dispensing device distributes the lubricating agent.
[0013] Finally, the powder is poured into the forming cavity, wherein it is compacted by means of the upper punch.
[0014] As can be easily appreciated, such operations involve the generation of downtime which can result in significantly longer production schedules and associated costs.
[0015] In order to carry out lubrication, in fact, it is necessary to wait until the lower punch has returned to its initial position and has thus completely cleared the forming cavity.
[0016] In addition to this, it is important to specify that generally the mechanical components made by sintering have complex and irregular shapes and, consequently, the forming cavity also has walls of irregular conformation, provided with grooves and undercut portions.
[0017] Therefore, the known type of pressing machines according to this second type are unable to effectively and evenly lubricate the walls of the forming cavity.
Description of the Invention
[0018] The main aim of the present invention is to devise a machine for pressing metal powders which allows effective compaction of the metal powder and at the same time allows production time to be kept short.
[0019] Another object of the present invention is to devise a machine for pressing metal powders which allows even lubrication of the forming cavity even in the case of walls of irregular conformation.
[0020] A further object of the present invention is to devise a machine for pressing metal powders which allows obtaining sintered components provided with high mechanical strength.
[0021] Another object of the present invention is to devise a machine for pressing metal powders which allows the aforementioned drawbacks of the prior art to be overcome within the framework of a simple, rational, easy and effective to use as well as affordable solution.
[0022] The aforementioned objects are achieved by this machine for pressing metal powders having the characteristics of claim 1.
[0023] The aforementioned objects are further achieved by a lower punch for machines for pressing metal powders having the characteristics of claim 14.
Brief Description of the Drawings
[0024] Other characteristics and advantages of the present invention will become more apparent from the description of a preferred, but not exclusive, embodiment of a machine for pressing metal powders, illustrated by way of an indicative, yet non-limiting example, in the attached tables of drawings wherein:
Figure 1 is an axonometric view of part of a machine for pressing metal powders according to the invention;
Figure 2 is a cross-sectional view along the plane II-II of the machine in Figure 1;
Figure 3 is an axonometric view of a lower punch according to the invention; figure 4 is a side detailed view of the lower punch in Figure 3;
Figure 5 is a cross-sectional view of the lower punch along the plane V-V in Figure 4;
Figure 6 is a cross-sectional view of the lower punch along the plane VI-VI in Figure 4;
Figure 7 is a cross-sectional view of the lower punch along the plane VII-VII in Figure 4.
Embodiments of the Invention
[0025] With particular reference to these figures, reference numeral 1 globally denotes a machine for pressing metal powders.
[0026] The machine 1 comprises at least one forming die 2 provided with a through drilling defining at least one working surface 3 and developing along an axis of work A.
[0027] The machine 1 also comprises at least one lower punch 4 associated movable with the through drilling along the axis of work A and provided with a contact surface 5 arranged in contact with the working surface 3 and with a supporting surface 6, facing upwards and defining, with the working surface 3, a pressing cavity 7 adapted to contain a metal powder.
[0028] The machine 1 also comprises at least one upper punch 8 arranged on top of the forming die 2, movable along the axis of work A in the through drilling and provided with a pressing surface 9 adapted to close the pressing cavity 7 and to compress the metal powder to obtain a compacted component C.
[0029] In detail, the forming die 2 is arranged with the axis of work A positioned substantially vertically.
[0030] The through drilling defines an upper opening 10 through which the metal powder is inserted within the pressing cavity 7 and the compacted component C flows out therefrom.
[0031] Specifically, the lower punch 4 is partly housed within the through drilling and is movable within the same along the axis of development between a forming position, wherein the supporting surface 6 is arranged inferiorly to the upper opening 10 to define the pressing cavity 7, and an extraction position, wherein the supporting surface 6 is arranged at the through drilling to extract the compacted component C.
[0032] For this purpose, the machine 1 comprises movement means, not shown in detail in the figures and adapted to move the lower punch between the forming position and the extraction position.
[0033] At the same time, the upper punch 8 is movable along the axis of development between a home position, wherein it is moved away from the forming die 2, and a pressing position, wherein it is partly inserted within the pressing cavity 7 and exerts a pressing force on the metal powder.
[0034] According to the invention, the lower punch 4 comprises dispensing means 11 adapted to dispense a lubricating agent into the pressing cavity 7 and the machine 1 comprises a system for feeding the lubricating agent to the dispensing means 11.
[0035] The dispensing means 11 are cut into the body of the lower punch 4. In actual facts, the dispensing of the lubricating agent is carried out directly from the lower punch 4.
[0036] Specifically, in the movement of the lower punch between the extraction position and the forming position, the dispensing means 11 are activated to dispense the lubricating agent.
[0037] In this way, as soon as the lower punch 4 returns to its initial position, i.e., the forming position, the pressing cavity 7 is ready to receive the metal powder, avoiding the generation of downtime and optimizing operating time.
[0038] For this purpose, the machine 1 also comprises an electronic unit configured to operate the feeding system at the same time as the movement means.
[0039] Thus, this machine 1 ensures even lubrication of the forming cavity and prevents residual metal powder from sticking to the working surface 3 between one pressing operation and the next. In this way, pressing is optimal and it is possible to obtain a compacted component C which conforms to production specifications and provided with high mechanical strength.
[0040] Advantageously, the dispensing means 11 comprise a plurality of dispensing holes 12 defined on the contact surface 5 and facing the working surface 3. Specifically, the working surface 3 has a conformation complementary to that of the side surface of the metal component to be obtained.
[0041] According to the embodiment shown in the figures, the through drilling has a cylindrical development and the working surface 3 comprises a helical toothing. In addition, such an implementation solution also provides that the forming die 2 may also comprise a forming element 13 arranged internally to the through drilling, developing along the axis of work A and adapted to result in the formation of a hole in the compacted component C. Still with reference to the embodiment shown in the figures, the forming element 13 is substantially cylindrical and the relevant surface is substantially smooth.
[0042] Thus, in this case, the working surface 3 comprises an outer working surface having a conformation corresponding to that of the outer surface of the metal component to be obtained, i.e., helical-toothed, and an inner working surface having a conformation corresponding to that of the inner surface of the metal component to be obtained, i.e., substantially smooth.
[0043] It is easy to appreciate, however, that the conformation of the working surface 3 may be of different type depending on the metal component to be obtained.
[0044] At the same time, the contact surface 5 of the lower punch 4 has a conformation complementary to that of the working surface 3. In actual facts, also the contact surface 5 comprises a helical toothing complementary to the working surface 3. In detail, the lower punch 4 is provided with an outer contact surface arranged in contact with the outer working surface, i.e., helical-toothed, and an inner contact surface arranged in contact with the inner working surface, i.e., substantially smooth.
[0045] The dispensing means 11 are, therefore, configured to dispense the lubricating agent on both the outer surface and the inner surface.
[0046] The upper punch 8 is in turn provided with an abutment surface 14 adapted to contact the working surface 3 and which has a conformation complementary to the latter.
[0047] In this particular case, the upper punch 8 is provided with an outer abutment surface adapted to contact the outer working surface and an inner abutment surface adapted to contact the inner working surface.
[0048] The movement of the punches 4, 8 is determined according to the conformation of the relevant surfaces 5, 14 and of the working surface 3. In this particular case, the conformation of the surfaces being of the helical type, the movement is a roto-translation. In the case where the surfaces are smooth, the movement is a translation along the axis of work A.
[0049] The supporting surface 6 and the pressing surface 9, on the other hand, define a bottom face and an upper face, respectively, of the metal component to be obtained.
[0050] The dispensing holes 12 are conveniently arranged in the proximity of the supporting surface 6. In this way, the dispensing means 11 are able to lubricate the pressing cavity 7 for the entire extent thereof, up to the upper opening 10. The dispensing means 11 also comprise a system of pipes 15, 16, 18 which are adapted to transfer the lubricating agent from the feeding system to the dispensing holes 12.
[0051] Conveniently, the system of pipes 15, 16, 18 is obtained within the lower punch 4. In actual facts, the system of pipes 15, 16, 18 is obtained within the body of the lower punch 4 during the relevant production.
[0052] In this regard, it should be specified that the lower punch 4 is made of a metal material obtained by liquid additive manufacturing. Specifically, by means of three-dimensional selective laser sintering printing.
[0053] The system of pipes 15, 16, 18 then flows into the dispensing holes 12. The system of pipes 15, 16, 18 will be described in more detail later in this disclosure.
[0054] Conveniently, the dispensing holes 12 are arranged according to at least one line of development extending around the contact surface 5.
[0055] The line of development can have a pattern selected from the list comprising: spiral, planar, broken, wavy. It is easy to appreciate that the line of development can have any pattern, selected depending on the conformation of the working surface 3 and of the lower punch 4.
[0056] The dispensing holes 12 are, in addition, advantageously arranged evenly along the line of development. In this way, an even distribution of the lubricating agent over the working surface 3 can be ensured. Alternatively, the dispensing holes 12 can also be arranged in a plurality of assemblies extending along the line of development.
[0057] According to a preferred embodiment, the line of development lies on a plane of development substantially perpendicular to the axis of work A. Advantageously, the dispensing holes 12 comprise a plurality of sets of dispensing holes 12, wherein the dispensing holes 12 of each set are arranged along a respective line of development.
[0058] In actual facts, the dispensing holes 12 can be arranged at different heights in order to optimize the dispensing of the lubricating agent or depending on special conformations of the contact surface 5.
[0059] In addition, the dispensing holes 12 of each set can be aligned with the dispensing holes 12 of at least one adjacent set, with respect to the axis of work
A.
[0060] Alternatively, the dispensing holes 12 of each set are misaligned with the dispensing holes 12 of at least one adjacent set, with respect to the axis of work
A.
[0061] With reference to the embodiment shown in the figures, the dispensing means 11 comprise at least two sets of dispensing holes 12, each defined on the outer contact surface. In detail, the dispensing means 11 comprise:
- at least a first set of dispensing holes 12, wherein the dispensing holes 12 of the first set are arranged on the ridges of the teeth of the contact surface 5; and
- at least a second set of dispensing holes 12, wherein the dispensing holes 12 of the second set are arranged on either side of the teeth of the contact surface 5.
[0062] In addition, the dispensing means 11 also comprise a third set of dispensing holes 12 defined on the inner contact surface. Each of the set develops along respective planar lines of development and has evenly distributed holes.
[0063] The first and second sets are misaligned with each other. In fact, as shown in Figures 3-7, the outer contact surface has a helical tooth conformation, therefore, a first set has the dispensing holes 12 arranged on the ridges of the teeth, while a second set has the dispensing holes 12 arranged on the sides of the tooth.
[0064] Such an arrangement makes it easy to lubricate the working surface 3 even in the case of complex surfaces such as, precisely, those fitted with a toothing. In fact, in such a case, effective lubrication takes on considerable importance since any adherence of the metal material can lead to alterations in the toothing of the finished metal component which, even if minor, can impair the use of the metal component itself.
[0065] Conveniently, each of the dispensing holes 12 has a respective conformation selected from the list comprising: circular, rectangular, cross-shaped, star-shaped and ring-shaped. The conformation of the dispensing hole 12 is selected depending on the amount of lubricating agent to be dispensed and on the desired mode of dispensing. It is therefore easy to appreciate that the dispensing hole 12 can comprise any conformation.
[0066] Likewise, it cannot be ruled out that the dispensing holes 12 may have different conformations to each other.
[0069] The system of pipes 15, 16, 18 comprises:
- at least one main pipe 15 connectable to the system for feeding; and
- a plurality of ending pipes 16 connected to the main pipe 15, each defining a respective dispensing hole 12.
[0070] The main pipe 15 communicates with the outside through an inlet hole 17 arranged at the base of the lower punch 4.
[0072] The system of pipes 15, 16, 18 comprises at least one secondary pipe 18 placed between the main pipe 15 and the ending pipes 16. The secondary pipe 18 receives the lubricating agent from the main pipe 15 and transfers it to the ending pipes 16.
[0073] According to the embodiment shown in the figures, each set of dispensing holes 12 has a relevant secondary pipe 18.
[0074] The main pipe 15 has a larger diameter than the ending pipes 16. Similarly, the secondary pipe 18 also has a larger diameter than the ending pipes 16.
[0075] Conveniently, the section of the ending pipe 16 corresponds to the conformation of the respective dispensing hole 12. It cannot, however, be ruled out that the section of the ending pipe 16 may be different to the conformation of the respective dispensing hole 12.
[0076] According to the embodiment shown in the figures, moreover, the ending pipe 16 has a substantially constant cross-sectional area.
[0077] Alternatively, the ending pipe 16 may have a decreasing cross-sectional area as it moves close to the dispensing hole 12.
[0078] According to a further aspect, the present invention also relates to a lower punch 4 for machines for pressing metal powders.
[0079] The lower punch 4 comprises:
- at least one contact surface 5 intended to be placed in contact with a corresponding working surface 3 of a forming die 2 of a machine 1 for pressing metal powders, wherein the forming die 2 is provided with a through drilling defining the working surface 3; and
- at least one supporting surface 6 adapted to define, with the working surface 3, a pressing cavity 7 adapted to contain a metal powder.
[0080] According to the invention, the lower punch 4 comprises the dispensing means 11 adapted to dispense the lubricating agent within the pressing cavity 7.
[0081] It has in practice been ascertained that the described invention achieves the intended objects, and in particular, the fact is emphasized that the machine according to the invention for pressing metal powders allows effective compaction of metal powder while at the same time enabling production times to be reduced.
1. Machine (1) for pressing metal powders, comprising:
- at least one forming die (2) provided with through drilling defining at least one working surface (3) and developing along an axis of work (A);
- at least one lower punch (4) associated movable with said through drilling along said axis of work (A) and provided with a contact surface (5) arranged in contact with said working surface (3) and with a supporting surface (6), facing upwards and defining, with said working surface (3), a pressing cavity (7) adapted to contain a metal powder;
- at least one upper punch (8) arranged on top of said forming die (2), movable along said axis of work (A) in said through drilling and provided with a pressing surface (9) adapted to close said pressing cavity (7) and to compress said metal powder to obtain a compacted component (C);
characterized by the fact that said lower punch (4) comprises dispensing means (11) adapted to dispense a lubricating agent into said pressing cavity (7) and by the fact that said machine (1) comprises a system for feeding said lubricating agent to said dispensing means (11).2. Machine (1) according to claim 1, characterized by the fact that said dispensing means (11) comprise a plurality of dispensing holes
(12) defined on said contact surface (5) and facing said working surface (3).
3. Machine (1) according to one or more of the preceding claims, characterized by the fact that said dispensing holes (12) are arranged according to at least one line
of development extending around said contact surface (5).
4. Machine (1) according to one or more of the preceding claims, characterized by the fact that said dispensing holes (12) are evenly arranged along said line of development.
5. Machine (1) according to one or more of the preceding claims, characterized by the fact that said line of development lies on a plane of development substantially
perpendicular to said axis of work (A)
6. Machine (1) according to one or more of the preceding claims, characterized by the fact that said dispensing holes (12) comprise a plurality of sets of dispensing
holes (12), wherein the dispensing holes (12) of each set are arranged along a respective
line of development.
7. Machine (1) according to one or more of the preceding claims, characterized by the fact that the dispensing holes (12) of each set are aligned with the dispensing
holes (12) of at least one adjacent set, with respect to said axis of work (A).
8. Machine (1) according to one or more of the preceding claims, characterized by the fact that the dispensing holes (12) of each set are misaligned with the dispensing
holes (12) of at least one adjacent set, with respect to said axis of work (A).
9. Machine (1) according to one or more of the preceding claims, characterized by the fact that said through drilling has a cylindrical development and said working
surface (3) comprises a helical toothing, said contact surface (5) comprising a helical
toothing complementary to said working surface (3) and by the fact that said dispensing
means (11) comprise:
- at least a first set of dispensing holes (12), wherein the dispensing holes (12) of said first set are arranged on the ridges of the teeth of said contact surface (5); and
- at least a second set of dispensing holes (12), wherein the dispensing holes (12) of said second set are arranged on either side of the teeth of said contact surface (5).
10. Machine (1) according to one or more of the preceding claims, characterized by the fact that each of said dispensing holes (12) has a respective conformation selected
from the list comprising: circular, rectangular, cross-shaped, star-shaped or ring-shaped.
11. Machine (1) according to one or more of the preceding claims, characterized by the fact that said dispensing means (11) comprise a system of pipes (15, 16, 18)
which are adapted to transfer said lubricating agent from said system for feeding
said dispensing holes (12), said system of pipes (15, 16, 18) being obtained within
said lower punch (4).
12. Machine (1) according to one or more of the preceding claims, characterized by the fact that said system of pipes (15, 16, 18) comprises:
- at least one main pipe (15) connectable to said system for feeding; and
- a plurality of ending pipes (16) connected to said main pipe (15), each defining a respective dispensing hole (12).
13. Machine (1) according to one or more of the preceding claims, characterized by the fact that said system of pipes (15, 16, 18) comprises at least one secondary
pipe (18) placed between said main pipe (15) and said ending pipes (16).
14. Machine (1) according to one or more of the preceding claims, characterized by the fact that the section of said ending pipe (16) corresponds to the conformation
of the respective dispensing hole (12).
15. Lower punch (4) for metal powder pressing machines, characterized by the fact that it comprises:
- at least one contact surface (5) intended to be placed in contact with a corresponding working surface (3) of a forming die (2) of a machine (1) for pressing metal powders, said forming die (2) being provided with a through drilling defining said working surface (3);
- at least one supporting surface (6) adapted to define, with said working surface (3), a pressing cavity (7) adapted to contain a metal powder;
- dispensing means (11) adapted to dispense a lubricating agent into said pressing cavity (7).