Method and device for manufacturing a cutting insert green body

Abstract

A method and device for manufacturing a cutting insert green body, the method includes the step of providing a compression tool having an upper and lower die, and an upper and lower punch. The upper die defines a punch tunnel in which the upper punch slides, and the lower die defines a punch tunnel in which the lower punch slides. The dies define a die cavity to accommodate a powder to be compressed by action of the respective punches to form the green body. Powder in the die cavity is compressed by forwarding the upper punch through the punch tunnel of the upper die and a predetermined distance L through the opening of the lower die. The upper die is displaced relative to the opening of the lower die and the upper punch is removed from the lower die to move the green body out of the lower die through the opening thereof.

Claims

1. A method for manufacturing a cutting insert green body by compressing a powder, comprising the steps of providing a compression tool having an upper die and a lower die, an upper punch and a lower punch, wherein the upper die defines a punch tunnel in which the upper punch is arranged to slide, and the lower die defines a punch tunnel in which the lower punch is arranged to slide, and wherein the dies, when joined together define a die cavity provided to accommodate a powder to be compressed by action of the respective punches for the forming of said green body; providing the lower punch in a predetermined position in the punch tunnel of the lower die; filling powder into an open cavity defined in the lower die; joining the upper and lower dies such that an opening of the upper die meets and communicates with a corresponding opening of the lower die and such that said cavity filled with powder in the lower die forms part of said die cavity; compressing the powder in said die cavity by action of said punches, wherein said upper punch is forwarded through the punch tunnel of the upper die and is forwarded a predetermined distance L through said opening of the lower die and into the lower die, whereby said green body is formed; displacing the upper die relative the opening of the lower die, thereby providing for more space for the green body to exit through; and removing the upper punch from the lower die, and moving the green body out of the lower die through said opening of the lower die, wherein the die cavity defined by the dies has a vertical centre axis and that, in the region of said opening of the lower die, an inner peripheral surface of the lower die has an inclination angle ? relative to said centre axis such that an inner circumference of the inner peripheral surface of the lower die increases towards said opening thereof, wherein the upper punch presents an abutment surface for abutment against the powder, an outer peripheral surface, and a punch edge at an intersection between the abutment surface and the outer peripheral surface, wherein the upper punch is forwarded the distance L into the lower die such that there is a remaining gap g between said inner peripheral surface of the lower die and said punch edge, wherein 0 ?m<g?30 ?m, wherein the level of the punch edge will define an upper edge of the green body, and wherein the upper edge is formed where said inner peripheral surface intersects a plane of the abutment surface of the upper punch.

2. A method according to claim 1, wherein the opening of the upper die is smaller than the opening of the lower die, such that the upper die overlaps the opening of the lower die with a distance l when the dies are joined.

3. A method according to claim 2, wherein l?55 ?m.

4. A method according to claim 1, wherein L?50 ?m.

5. A method according to claim 1, wherein 2????30?.

6. A method according to claim 1, wherein in the region of the opening of the upper die, there is formed a gap k between an outer peripheral surface of the upper punch and an inner peripheral surface of the upper die, wherein k<50 ?m.

7. A method according to claim 1, wherein the green body is moved out of the lower die either by withdrawal of the lower die while the lower punch is maintained in its position, or by ejection of the lower punch through the lower die while the latter is maintained in its position, or a combination thereof.

8. A device for manufacturing a cutting insert green body by compressing a powder, said device comprising: a compression tool including an upper die and a lower die, an upper punch and a lower punch, wherein the upper die defines a punch tunnel in which the upper punch is arranged to slide, and the lower die defines a punch tunnel in which the lower punch is arranged to slide, and wherein the dies, when joined, together define a die cavity provided to accommodate a powder to be compressed by action of the respective punches for the forming of said green body, the upper and lower dies each having a respective opening such that an opening of the upper die meets and communicates with a corresponding opening of the lower die when the upper and lower dies are joined, whereby the upper punch is arranged so as to be forwarded a predetermined distance L through said opening of the lower die and into the lower die upon compaction of the powder, and whereby the upper die is displaceable relative to the opening of the lower die, and being arranged so as to be displaced relative said opening of the lower die before removal of said green body through said opening of the lower die, thereby providing for more space for the green body to exit through, wherein the die cavity defined by the dies has a vertical centre axis and that, in the region of said opening of the lower die, an inner peripheral surface of the lower die has an inclination angle ? relative to the centre axis such that an inner circumference of the inner peripheral surface of the lower die increases towards said opening thereof, wherein the upper punch presents an abutment surface for abutment against the powder, an outer peripheral surface, and a punch edge at an intersection between the abutment surface and the outer peripheral surface, and wherein the upper punch is arranged to be forwarded the distance L into the lower die such that there is a remaining gap g between said inner peripheral surface of the lower die and said punch edge, wherein 2????30?, wherein the level of the punch edge will define an upper edge of the green body, and wherein the upper edge is formed where said inner peripheral surface intersects a plane of the abutment surface of the upper punch.

9. A device according to claim 8, wherein the opening of the upper die is smaller than the opening of the lower die, such that the upper die overlaps the opening of the lower die with a distance/when the dies are joined.

10. A device according to claim 9, wherein l?55 ?m.

11. A device according to claim 8, wherein L?50 ?m.

12. A device according to claim 8, wherein in the region of the opening of the upper die, there is formed a gap k between an outer peripheral surface of the upper punch and an inner peripheral surface of the upper die, wherein k<50 ?m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Hereinafter, an embodiment of the present invention will be presented with reference to the annexed drawing, on which:

(2) FIG. 1 is a cross section of a device according to the invention before a filling step in which a powder is introduced into a die cavity thereof,

(3) FIG. 2 is a corresponding cross section of the device shown in FIG. 1 as arranged during the filling step,

(4) FIG. 3 is a corresponding cross section of the device shown in FIGS. 1 and 2 showing a step in which an upper die is joined with a lower die,

(5) FIG. 4 is a corresponding cross section of the device shown in FIGS. 1-3 during an initial stage of a pressing step during which the powder introduced into the die cavity is to be compressed,

(6) FIG. 5 is a corresponding cross section of the device shown in FIGS. 1-4 during a subsequent stage of said pressing step,

(7) FIG. 6 is a corresponding cross section of the device shown in FIGS. 1-5 in connection to ejection of a green body formed during the foregoing pressing step,

(8) FIG. 7 is a cross section showing a detail of the device as arranged during the pressing step shown in FIG. 5, and

(9) FIG. 8 is a corresponding cross section of prior art.

DETAILED DESCRIPTION OF THE INVENTION

(10) FIGS. 1-6 show different steps during forming of a cutting insert green body by means of a device according to the present invention. The cutting insert green body is formed from a powder which is compacted by means of the device and method of the invention. The powder may be any powder suitable for such production, for example a powder used for making cemented carbide, ceramic or cermet bodies. The cutting insert to be produced is aimed for the machining of metal by milling, drilling or turning or by similar chip forming methods. After forming of the green body, the latter is preferably sintered to its final shape in accordance with suitable contemporary technique and, normally, provided with a suitable wear resistant coating comprising single or multiple layers of, for example, at least one carbide, nitride, carbonitride, oxide or boride with any suitable contemporary technique, such as physical vapour deposition or chemical vapour deposition.

(11) FIG. 1 shows the principal components of the device according to the invention, in a position before a filling step in which a powder is introduced into a die cavity thereof. The device comprises an upper die 1, a lower die 2, an upper punch 3 and a lower punch 4. There is also provided an upper core pin 5 and a lower core pin 6.

(12) The upper die 1 defines a punch tunnel 7 in which the upper punch 3 is able to slide in a vertical direction (given that the device is positioned as suggested in the room). The lower die 2 defines a punch tunnel 8 in which the lower punch 4 is able to slide in a vertical direction. Though not shown in the figures, it should be understood that to the respective punches 3, 4 there is connected a respective driving device for the driving of each punch 3, 4 in its respective punch tunnel such that the respective punch 3, 4 slides therein in the vertical direction. In the embodiment shown, the upper punch 3 is fixed to the upper core pin 5, such that these components will move together as one unit. The lower core pin 6, on the other hand, which is arranged in a tunnel in the lower punch 4, is movable in a vertical direction in relation to the lower punch 4 and is separately driven with regard to the latter. The core pins 5, 6 are provided for the purpose of generating a centre hole in the cutting insert green body to be produced by means of the device. It should be understood that embodiments that do not include core pins or in which core pins are differently arranged and driven with regard to the remaining components of the device are also conceived and fully possible within the scope of the present invention.

(13) When joined, the upper and lower dies 1, 2, or more precisely the punch tunnels 7, 8 thereof, define a die cavity 9 arranged to accommodate a powder, indicated with 10 in FIGS. 2-4, which is compacted to a cutting insert green body, indicated with 11 in FIG. 5, by the action of the upper and lower punches 3, 4 during a pressing step in which at least one of the punches 3, 4 is moved towards the opposite punch 4, 3 in its respective punch tunnel 7, 8.

(14) The upper die 1 comprises a lower peripheral surface 12 arranged to abut and be supported by a corresponding upper peripheral surface 13 of the lower die 2 when the two dies are joined. The punch tunnel 7 of the upper die 1 presents an opening 14 in the lower peripheral surface 12 of the upper die 1. The punch tunnel 8 of the lower die 2 presents an opening 15 in the upper peripheral surface 13 of the lower die 2. The opening 14 of the upper die 1 is slightly smaller than the opening 15 of the lower die 2. When the dies 1, 2 are joined, and arranged for the pressing step in which the powder in the die cavity 9 is to be compressed, the opening 14 of the upper die 1 is in alignment with and opposite to the opening 15 of the lower die 2. Due to the difference in size between the openings 14, 15, the upper die 1 will overlap the opening 15 of the lower die 2. Preferably, the overlap, indicated with l in FIG. 7, is generally constant along the circumference of the opening 15 of the lower die 2. It is assumed, and preferred, that the opening 14 of the upper die 1 has a shape corresponding to the shape of the opening 15 of the lower die 2. However, there may be alternative embodiments in which a punch edge (to be described later) of the upper punch 3 has a non-linear shape, such as a wave-like shape, whereby the l will be permitted to vary and there will be a slight difference in shape between the opening 14 of the upper die 1 and the opening 15 of the lower die 2.

(15) In the following the essential steps of the process in which a cutting insert green body 11 is produced by means of the device according to the invention will be described.

(16) FIG. 2 shows a filling step in which the upper die 1, upper punch 3 and the upper core pin 5 are distanced from the lower die 2, the lower punch 4 and the lower core pin 6. The lower core pin 6 is forwarded in a vertical direction to a position in which an upper abutment surface 17 thereof is in alignment with the upper peripheral surface 13 of the lower die 2. The lower punch 4 is provided in a vertically retracted position in the punch tunnel 8 of the lower die 2. Thereby an open cavity that will form part of the die cavity 9 mentioned earlier is defined by an upper abutment surface 18 of the lower punch 4, an inner peripheral surface 19 of the lower die 2 that also defines at least part of the punch tunnel 8 of the lower die 2, and an outer peripheral surface 20 of the lower core pin 6. A powder 10 is introduced into the above-mentioned open cavity in the lower die 2.

(17) In a subsequent step shown in FIG. 3 the upper die 1 is joined with the lower die 2, in this embodiment by means of a vertical motion of the upper die 1 such that it lands on the lower die 2. The opening 14 of the upper die 1 is in the above-mentioned position relative the opening 15, in which a rim of the upper die 1 will overlap the opening 15 of the lower die 2 along the circumference of the latter. The upper punch 3, together with the upper core pin 5, is forwarded to a position in which a lower abutment surface 21 of the upper core pin 5 abuts the upper abutment surface 17 of the lower core pin 6. A closed die cavity 9 is now defined by a lower abutment surface 22 of the upper punch 3, an inner peripheral surface 23 of the upper die 1 that also defines at least part of the punch tunnel 7 of the upper die, an outer peripheral surface 24 of the upper core pin 5 and the surfaces that, with reference to FIG. 2, defined the above-mentioned open cavity.

(18) In a further subsequent step, shown in FIG. 4, the lower punch 4 is forwarded towards the upper punch 3 such that the powder 10 is lifted in the cavity 9 towards the upper punch 3. Thereby, a desired distribution of the powder is achieved.

(19) Subsequently, as shown in FIG. 5, the upper punch 3 is forwarded towards the lower punch 4. Since, in this embodiment, the upper core pin 5 is fixed to the upper punch 3, the upper core pin 5 and the lower core pin 6 are also moved together with the motion of the upper punch 3, in the same direction and to the same extent as the latter. The upper punch 3 is forwarded to a predetermined level in the cavity 9 such that the powder 10 is compacted into a green body 11. The upper punch 3 presents a punch edge 25 (see FIGS. 1 and 7) at an intersection between the abutment surface 22 and an outer peripheral surface 26 of the upper punch 3, and, as will be further discussed in the following presentation of the invention, the upper punch 3 is forwarded such a distance L (see FIG. 7) into the lower die 2 that there is a remaining gap g (see FIG. 7) between said inner peripheral surface 19 of the lower die and said punch edge 25. As can be seen in FIGS. 5 and 7, the position of the upper die 1 relative the lower die 2, and the position of the forwarded upper punch 3, is such that the whole green body 11 will be received by the lower die 2 as the powder 10 is compacted.

(20) After compaction of the powder 10 into the green body 11 shown in FIG. 5 the method of the invention includes the steps of displacing the upper die 1 relative the opening 15 of the lower die 2, thereby providing for more space for the green body 11 to exit through, and removing the upper punch 3 from the lower die 2, and moving the green body 11 out of the lower die 2 through said opening 15 of the lower die 2. These steps are indicated in FIG. 6. In embodiments that, like the one presented here, comprises an upper core pin 5 connected to the upper punch 3, the upper core pin 5 is also removed from the lower die 2 together with the upper punch 3. Since the upper punch 3, the lower die 2 and the upper die 1 can be designed such that the latter will be at a very short distance from the level to which the punch edge 25 of the upper punch 3 is forwarded during compaction, and the upper die 1 is displaced from the lower die 2 before the green body 11 is ejected from the latter, a very small release portion on the inner peripheral surface 19 of the lower die 2 will be needed above said level. As has already been explained, the formation of a residual edge on the green body 11 by powder that has escaped into such a release portion during the pressing step is thereby suppressed.

(21) FIG. 7 is a detailed representation of the region in which the abutment surface 22 of the upper punch 3 abuts the powder 10 during pressing thereof, at the level to which the upper punch 3 is maximally forwarded into the lower die 2. The upper punch 3, and more precisely the punch edge 25 thereof, is forwarded a predetermined distance L through the opening 15 of the lower die 2 and into the lower die 2, to the level at which it is maximally forwarded.

(22) The die cavity 9 has a centre axis x (see FIGS. 1-6). The upper punch 3, the lower punch 4, and the upper and lower core pins 5, 6 also has x as their respective centre axis. Above the level to which the punch edge 25 of the upper punch 3 is maximally forwarded, the inner peripheral surface 19 of the lower die 2 has an inclination angle ? relative said centre axis x such that an inner circumference of the inner peripheral surface 19 of the lower die 2 increases towards the opening 15 thereof. In this embodiment, the inner peripheral surface 19 of the lower die 2 has the same inclination angle ? also in the region below said level, down to the level at which the abutment surface of the lower punch 4 is forwarded or positioned during the pressing step. It should be understood that the inclination angle may differ along the inner peripheral surface 19, but that, at least in the release portion, i.e. the part of said surface 19 above the level to which the punch edge 25 is forwarded, there should be such an angle in order to permit radial expansion of the green body as the latter is ejected through the opening 15 of the lower die 2. The inclination angle ? is in the range of 2????30?, depending on shape and size of the green body to be formed.

(23) As can be seen in FIG. 7, the upper punch 3 is only forwarded to such a level that there will be a remaining gap g between the punch edge 25 and the inner peripheral surface 19 of the lower die 2. Contact between the punch edge 25 and the inner peripheral surface 19 should be avoided. The gap g may differ around the circumference of the upper punch 3 but should not be larger than 30 ?m in order to prevent the upcoming of an excessively large residual edge at the upper edge of the conceived green body 11 to be formed.

(24) The opening 14 of the upper die 1 is smaller than the opening 15 of the lower die 2, but has a corresponding shape as the latter, which in its turn is dependent on the shape of the green body 11 to be formed and adapted to permit ejection of the whole green body 11 out of the lower die 2 through said opening 15 thereof. As a result thereof, a part of the lower peripheral surface 12 of the upper die 1 will overlap the opening 15 of the lower die 2. This overlap is indicated with l in FIG. 7, and forms a rim along the circumference of the opening 15 of the lower die 2. It should be understood that the size of the overlap l may differ along the circumference of the opening 15 of the lower die 2. The overlap l is dependent on the distance L that the upper punch 3 is forwarded into the lower die 2, and the inclination angle ? of the inner peripheral surface 19 of the lower die 2. It is also dependent on the requisite that there should only be a very restricted gap k between the inner peripheral surface 23 of the upper die 1 and the outer peripheral surface 26 of the upper punch 3 in order to provide for accurate guiding of the upper punch 3 in the punch tunnel 7 defined by the inner peripheral surface 23 of the upper die 1 and to provide for prevention of leakage of powder into and through said gap k in connection to the pressing step during which the powder 10 in the die cavity 9 is compacted. Preferably, k<10 ?m, and L should preferably be chosen such that l+k?20 ?m. Thereby, the space 27 defined by the outer peripheral surface 26 of the upper punch 3, the overlapping part of the lower peripheral surface 12 of the upper die 1 and the inner peripheral surface 19 of the lower die 2 can be very restricted, and will provide for formation of only a very small residual edge on the green body due to leakage of powder into said space 27 during the pressing step. This should be compared to the prior art, shown in FIG. 8, in which there is no subdivision of the die in an upper die and a lower die, and in which the only die has to provide for a sufficient release portion for an expanding green body when the latter is ejected in the direction of the upper punch. Prior art will therefore adopt a much larger gap k between the inner peripheral surface of the die and outer peripheral surface of the punch, and there will be much larger space for the powder to leak into during the pressing step. Thus, prior art will result in a larger residual edge on the green body than the device and method of the present invention will result in.

(25) In the foregoing description of the present invention, the definitions upper and lower have been used for a number of components and surfaces thereof, and as a consequence thereof also the definition vertical direction. However, it should be understood that these definitions have been made merely in order to facilitate the disclosure of the invention, when the device according to the invention is positioned in such a position in the room that these definitions are valid, as can be seen on the drawing. Other positioning of a correspondingly designed device is, of course, also within the claimed scope of protection. However, according to a preferred embodiment, this specific positioning of the device is preferred, since it will facilitate the whole set up of the device as well as certain method steps, in particular the filling of the powder into the die cavity.