Patent Application
20170043397
The present invention relates to a method of compacting a powder into a cutting insert green body, such that said cutting insert green body obtains a barrel-shape having a parting line on the outer peripheral surface thereof which is at least partially non-perpendicular to a pressing axis along which said compacting is performed, said method comprising the steps of: providing a compaction tool comprising a die that comprises an upper die part and a lower die part, and an upper punch and a lower punch, wherein the upper and lower die parts, when joined together, contribute to defining a die cavity that is delimited by an inner peripheral surface that defines the shape of the outer peripheral surface of the barrel-shaped green body to be formed by said compaction, said method further comprising the steps of providing either of the lower die part or the upper die part with a pressing bore extending from said cavity, for the lower punch or the upper punch to be received in in connection to said compacting.
The invention also relates to a device for manufacturing a cutting insert green body by compacting a powder, said device comprising; a die that comprises an upper die part and a lower die part that are separable from each other, and an upper punch and a lower punch, at least one of which is moveable along a pressing axis in relation to the die, wherein the upper and lower die parts, when joined, contribute to defining a die cavity that is delimited by an inner peripheral surface that defines the shape of the outer peripheral surface of the green body to be formed by said compaction, and wherein said inner peripheral surface of the die cavity is designed such that the green body obtains a barrel-shape having a parting line on the outer peripheral surface thereof which at least partially is non-perpendicular to said pressing axis, and wherein at least one of the lower die part and the upper die part has a pressing bore extending from said cavity, for the lower punch or the upper punch to be received in.
The invention relates to the technical field in which cutting inserts, preferably to be used for the machining of metal by milling, drilling or turning or by similar chip forming methods, are produced from a powder which is compacted into a green body and then subjected to a sintering process in which the compacted green body is further densified. Typically, the sintered body is then provided with a suitable wear resistant coating, such as a carbide, nitride, carbonitride, oxide, or boride with any suitable contemporary technique, such as physical vapour deposition or chemical vapour deposition.
It should be understood that a parting line as referred to herein is a line along which the barrel-shaped green body presents its maximum extension in a radial direction as seen from the a centre line of the green body. Preferably, said centre line is parallel with and coincident with the pressing axis.
It should also be understood that the die must not be restricted to being comprised only by the mentioned die parts, but that further die parts may be provided, and that the mentioned die parts may be further subdivided into further subparts thereof.
The compacted cutting insert green body is, typically, subjected to a sintering process in order to complete the production of a cutting insert on basis thereof.
According to prior art, barrel-shaped cutting inserts may be formed by means of a process which includes that barrel-shaped green bodies are formed in a compaction device that comprises a die that is divided in an upper die part and a lower die part. The die parts are surrounded by an outer die part or a press table having a generally flat upper surface. When joined together, the upper die part and the lower die part define a chamber which defines the outer peripheral surface of the green body to be formed. Normally, the lower die part comprises a pressing bore extending from the lower surface thereof to said chamber, and the upper die part comprises a pressing bore that extends from an upper surface thereof to said chamber. There is also provided an upper punch arranged to slide through the upper pressing bore, and a lower punch arranged to slide through the lower pressing bore. During compaction, the respective punches are forwarded through the respective pressing bores such that the ends thereof reach said chamber and contribute to the definition of the outer peripheral surface of the green body by defining the opposite upper and lower surfaces thereof.
Prior to the compaction step, the upper die part is retracted or held in a retracted position in relation to the lower die part. The lower punch is retracted or held in a retracted position in the pressing bore provided in the lower die part. An upper surface of the lower die part is exposed as a consequence of the retraction of the upper die part. The exposed upper surface of the lower die part is in alignment with the upper surface of the surrounding press table, thereby enabling a powder filling device to be forwarded on said upper surfaces of the press table and the lower die part to a position in which it is enabled to introduce a powder into the part of the chamber defined by the lower die part, which defines an opening in said upper surface. Since the lower punch is retracted, powder is also introduced in the part of the pressing bore of the lower die part that is not occupied by the lower punch. After completion of the powder filling step, the powder filling device is retracted and the upper die part is forwarded to and joined with the lower die part. The compaction step is then performed by forwarding the lower and upper punch respectively to a position in which they, together with the inner walls of the respective die parts, define the shape of the green body to be formed. Finally, the upper die part is once again retracted, together with the upper punch, and the lower punch is further forwarded upwards in the direction of the pressing axis until the green body is fully exposed. Preferably the lower punch is forwarded until the upper surface thereof is in alignment with the upper surface of the lower die part. Thereby, a green body removal device, e.g. a robot arm, is enabled to remove the green body, and the main steps of the compaction sequence are finished.
The upper surface of the lower die part is flat, thereby enabling alignment with the upper surface of the press table and enabling the powder filling device to slide thereon and to fit tightly on top of and around the opening in said upper surface of the lower die part. Thereby, the risk of having powder escaping to the upper surface of the lower die part is efficiently suppressed. Powder remaining on the upper surface of the lower die will have a negative impact on the sealing between the upper and lower die parts and should therefore be avoided.
However, the above design is primarily suitable for the compaction of a barrel-shaped green body that has a parting line that is perpendicular to the pressing axis of the punches, and/or extends in one plane only. An upper inner edge of the lower die part extends along a line defining the parting line of the green body, and so does a lower inner edge of the upper die part. Should the parting line have a different than planar extension, the upper surface of the lower die part will have a contour corresponding to the contour of the parting line and will not be flat. This fact will make sliding of the powder filling device difficult due the fact that part of the lower die part will project from the plane defined by the upper surface of the outer die part or press table. If the contour is such that parts of the upper surface around said opening is below the level of the rest of said upper surface, it will be difficult to prevent powder from being gathered at those parts of the upper surface during powder filling. Such powder will have a negative impact on the sealing between the lower and the upper die parts.
It is an object of the present invention to present a new and alternative method and a device for producing a cutting insert green body, wherein the green body to be produced has a barrel-shape with a parting line which is not planar and/or not perpendicular to the pressing axis and wherein a die used therefore comprises two die parts the inner peripheral surface of which, when joined together, define an outer peripheral surface of the green body. The invention shall enable efficient and reliable filling of powder into the die regardless of the fact that the parting line is non-planar and/or not perpendicular to the pressing axis.
The object of the invention is obtained by means of the initially defined method, characterized in that it comprises the steps of
It is not crucial in which order the upper punch and the upper die part are retracted from the lower die part in order to expose the green body and make the latter accessible for a device for the removal of the green body. In order to fully expose the compacted green body, the lower punch is forwarded upwards further through the lower die part. This motion may take place simultaneously with the retraction of the upper punch, such that the compacted green body is held between the two punches during displacement thereof out of the lower die part. Preferably, the upper die part is separable from the lower die part in the direction of the pressing axis and, preferably, separation is achieved by retraction of the upper die part upwards from the lower die part. The term “contiguously” as well as the term “coincide” as used here and hereinafter does not necessarily mean that there is a physical contact between edges or surfaces that are contiguously arranged or coincide. However, preferably, a sealing effect, preventing powder from leaking into any space between such edges and surfaces is achieved as an effect of such coincidence.
Preferably, said method comprises the step of providing a powder-filling device and positioning it on top of said upper opening in the upper die part or removing it from said position by enabling it to slide on said upper surface of the upper die in said direction in which said surface extends rectilinearly. Thereby the use of a sliding powder-filling device is enabled. Preferably, in the direction in which the upper surface of the upper die extends rectilinearly, said surface extends in a direction perpendicular to the pressing axis. Preferably, the surface that extends rectilinearly extends rectilinearly from a position laterally offset from said upper opening to said upper opening, corresponding to a conceived sliding path of a powder-filling device.
According to another embodiment the upper die part is retracted from the lower die part through a rectilinear motion of at least one of said upper die part and lower die part in the direction of the pressing axis.
The object of the invention is also achieved by the initially mentioned device, characterized in that
The provision of an upper surface of the upper die that, at least in one direction, extends rectilinearly, and the upper opening therein, enables a powder filling device to be positioned on top of said opening by a lateral rectilinear sliding motion, for the purpose of filling powder into the die. The upper surface of the upper die extends rectilinearly in a direction from a lateral position on the surface to the opening therein, thereby enabling a powder filling device to be slid along said rectilinearly extending surface from a lateral position to a position on top of said opening. The rectilinearly extending surface includes the area around said opening.
According to one embodiment, the lower die part has an upper surface which is delimited by said upper inner edge and which, from a centre axis of said cavity parallel with the pressing axis, extends in a lateral direction from said upper inner edge, and that the upper die part has a lower surface which is delimited by said lower inner edge thereof and which, from said centre axis, extends in a lateral direction, wherein at least parts of the upper surface of the lower die part and the lower surface of the upper die part are in bearing contact with each other when the upper and lower die parts are joined and the lower inner edge of the upper die part and the upper inner edge of the lower die part are contiguously arranged in relation to each other and the inner cavity is defined. Thereby, bearing surfaces are not only defined by said upper and lower edges respectively, but also by said parts of the upper and lower surfaces of the lower and upper die parts respectively that bear against each other, thereby contributing to a more stable design. The upper and lower edges may not even be in direct contact with each other and, in the case that there is a compressive load pressing the die parts against each other, such load may be adopted by said parts of the surfaces and not by the edges. Such an embodiment might even be preferred, since it prevents damage of the edges caused by compressive load on the latter.
According to one embodiment, said upper and lower surfaces have corresponding extension and are in bearing contact with each other along the whole area thereof when the upper and lower dies are joined and the lower inner edge of the upper die part and the upper inner edge of the lower die part are contiguously arranged and the inner cavity is defined. Thereby, a stable and steady engagement between the upper and lower die parts is promoted.
According to one embodiment, the upper surface of the upper die part is flat. Thereby, a powder-filling device is enabled to be positioned on top of said opening in the upper surface of the upper die part by a sliding motion in any direction on said upper surface.
According to yet another embodiment, the upper surface of the upper die part extends in a plane perpendicular to the pressing axis.
According to yet another embodiment, the die comprises an outer die part that at least partially laterally encloses the upper and lower die parts when those are joined. The outer die part may be connected to the lower die part and form a part thereof.
Preferably, the outer die part has an upper surface that is arranged to be contiguously arranged in relation to the upper surface of the upper die part when the latter is joined with the lower die part and the device is set for filling of powder into said cavity. In other words, the upper surfaces of the upper die part and the outer die part are in alignment and in close proximity to each other, at least partly, and preferably such that, in the aforementioned direction in which the upper surface of the upper die part extends rectilinearly, the upper surface of the outer die part is in alignment with the upper surface of the upper die part. Thereby, a powder-filling device is enabled to slide on the upper surface of the outer die part and on the upper surface of the upper die part from one of said surfaces to the other without being hindered by any level difference between said upper surfaces.
According to one embodiment, the upper die part is displaceable in the direction of the pressing axis in relation to the outer die part.
According to one embodiment, the device according to the invention comprises a powder-filling device, arranged to slide on said upper surface of the upper die part in said at least one direction in which the upper surface extends rectilinearly, to and from a powder-filling position on top of said upper opening of the upper die.
According to one embodiment, the upper die part presents an extension which is connected to an actuator by means of which a displacement of the upper die part in the direction of the pressing axis is enabled. The extension is positioned such that it does not prevent a powder filling device from sliding to and from said opening in the upper surface of the upper die part in a direction in which the upper surface extends linearly. Furthermore, the extension is positioned and designed such that it does not prevent a robot or the like from removing the compacted green body when the latter is in its exposed position. The extension may either extend upwards to an actuator located above the upper die part or downwards to an actuator located below the lower die part.
According to one embodiment, the cutting insert green body, the outer peripheral surface of which is defined by the inner peripheral surface of the die cavity, presents an upper end, a lower end and a waist between said upper end and lower end, and, in at least one radial direction as seen from a centre axis of the cutting insert green body, the waist has a lateral extension that is larger than the corresponding lateral extension of the cutting insert green body anywhere from the waist to the upper end of the cutting insert green body and anywhere from the waist to the lower end of the cutting insert green body. Typically, the waist defines the maximum width of the cutting insert green body, and the width of the cutting insert tapers from the waist towards the respective upper and lower ends of the cutting insert. The waist need not extend further laterally than the rest of the cutting insert body in all radial directions, but at least in some radial directions, such that a sector is defined, for which the waist has a larger lateral extension than the rest of the cutting insert green body. Typically, the waist has a larger lateral extension than the rest of the cutting insert green body in all lateral directions, i.e. for a sector of 360°. A lateral extension is referred to as an extension cross wise to the centre axis of the cutting insert green body extending from the upper end to the lower end of the cutting insert green body. The waist may defined by a line or a zone running circumferentially around the body.
The invention also relates to a cutting insert, characterized in that it is formed from a green body produced in a device according to the invention.
Further features and advantages of the invention will be disclosed in the following detailed description of exemplifying embodiments of the invention.
Hereinafter, embodiments of the present invention will be described in detail with reference to the annexed drawing, on which:
The waist of the cutting insert green body to be formed is regular in the sense that it extends in a plane perpendicular to a centre axis of the cutting insert green body to be formed. The centre axis of the green body, when confined by the die 1, coincides with or is parallel with the aforementioned pressing axis x1 of the punches 5, 6. Thus, the parting plane between the upper die part and the lower die part is perpendicular to the pressing axis x1.
Accordingly, filling of the die with powder gets more complicated. The present invention, as described hereinafter with reference to
Further, the compaction device comprises an upper punch 22 and a lower punch 23. The upper punch 22 extends longitudinally in and is movable in the direction of a pressing axis x. The lower punch 23 extends longitudinally in and is movable in the direction of a pressing axis that does, but need not, coincide with the pressing axis x of the upper punch 22. The respective punches 22, 23 are connected to a respective actuator, not shown, by means of which their movement in the direction of the pressing axis x is accomplished. Through the lower punch 23, in the direction of the pressing axis x, a core pin 24 extends. The core pin 24 is connected to a further actuator, not shown, by means of which it is moved in the direction of the pressing axis x. It should be understood that other provisions of one or more core pins, or no use thereof at all, is also within the scope of the present invention. It should also be understood that there may be further punches provided and/or that the upper and lower punches may be subdivided into further punches.
The lower die part 20 defines part of a die cavity 25 that defines the final shape of the cutting insert green body 13 to be compacted. The lower die part 20 also presents a bore that extends from said die cavity 25 to a lower surface of the lower die part 20 and through which the lower punch 23 is introduced into the lower die part 20. The bore has an inner peripheral surface corresponding to the outer peripheral surface of the lower punch 23 and defines a guiding bore through which the lower punch 23 can be advanced towards said cavity 25 or retracted therefrom. An upper end surface 26 of the lower punch 23 contributes to the definition of said die cavity 25 when the lower punch is advanced to a final compaction position, as shown in
The upper die part 19 defines a further part of the die cavity 25 that defines the final shape of the cutting insert green body 13 to be compacted. The die cavity 25 is completely defined once the upper die part 19 is joined to the lower die part 20 and the upper punch 22 is advanced to its final compaction position and the lower punch 23 is advanced to its final compaction position. The final compaction position is shown in
The cutting insert green body to be compacted has the geometry as described with reference to
The upper die part 19 presents an upper surface 30 which is generally flat and extends in a plane that is perpendicular to the pressing axis x. In the upper surface 30 of the upper die part 19 there is provided an opening 31. The opening 31 is provided for receiving the upper punch 22 when the latter is advanced to its final compaction position and defines the beginning of a punch tunnel through which the punch is advanced. The outer die part 21 comprises an upper surface 32, which is generally flat. Around the outer die part 21 there is also provided a table 33 that has an upper surface 34. It should be stated that the provision of both an outer die part 21 and a table 33 is not a necessity. Depending on the function and design of the outer die part 21, the latter may be regarded as a table rather that a die part. In such a case, it might also happen that any further table, like table 33, is not included in the compacting device.
For the purpose of filling powder into the die cavity 25 during a powder-filling step, the compaction device also comprises a powder-filling device 35. The powder-filling device 35 is arranged so as to slide on the upper surfaces 30, 32 of the upper die part 19 and the outer die part 21 respectively and, possibly, also on the upper surface 34 of the table 33 to and from a position on top of the opening 31 in the upper surface 30 of the upper die part 19. In order to enable such sliding, the upper surfaces 30, 32 of the upper die part 19 and the outer die part 21 respectively, and preferably also the upper surface 34 of the table 33, are in alignment with each other when the upper die part 19 is in a position ready for powder-filling. This position is shown in
In order to make the upper die part 19 be conveniently connected to an actuator for moving the upper die part 19 in the direction of the pressing axis x, the upper die part 19 presents an upper extension 36 which extends above said upper surface 30, and there is space 37 between said upper surface 30 of the upper die part 19 and an opposite lower surface 38 of the upper extension 36 thereof, and there is a lateral opening into said space enabling the powder-filling device 35 to be slid to or from the upper opening 31 of the upper die part 19 through said lateral opening. The upper extension 36 is connected to an actuator, not shown, for moving the upper die part in the direction of the pressing axis x. In the present embodiment, the upper extension 36 also defines a punch channel for guiding the upper punch 22. However, it should be stated that such a punch channel is only an optional feature of the compaction device according to the invention.
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In order to allow a removal device 39 to remove the compacted cutting insert green body 13 after compaction thereof, the lower extension 42 of the upper die part 41 comprises a lateral opening 43 which is exposed when the upper die part 41 is retracted from the position in which it is joined with the lower die part 20, such that a compacted green body 13, which is exposed as a result of said retraction of the upper die part 41, is laterally exposed through said opening 43.
| Number | Date | Country | Kind |
|---|---|---|---|
| 14164869.1 | Apr 2014 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2015/055877 | 3/20/2015 | WO | 00 |
