TECHNICAL FIELD
[0001] The present invention relates to a device for manufacturing a cutting insert green
body by compacting a powder, said device comprising: a die for receiving said powder;
at least one punch for compacting said powder received by said die, and; a powder-filling
device for filling powder into the die, wherein, in an upper surface of at least one
part of the die, the die comprises an upper opening through which said powder is introduced
into the die and through which or towards which said punch may be forwarded into the
die for the purpose of compacting powder introduced into the die, and wherein said
upper opening is defined by an edge that presents a curvature other than planar.
[0002] The invention also relates to a method of compacting powder into a cutting insert
green body, by means of a device according to the invention.
BACKGROUND OF THE INVENTION
[0003] In connection to the compacting of powder into cutting insert green bodies to be
sintered into cutting inserts for the cutting of metals, it may be of interest to
purposively affect the distribution of the non-compacted powder filled into a die
in order to suppress predetermined density variations within the compacted green body
to be formed.
[0004] Accordingly, it is of interest to be able to press a powder into a green body with
a uniform density distribution in order to, for example, minimize the upcoming of
cracks during the pressing operation or to avoid unintentional shape distortions during
the subsequent sintering operation. In connection to the pressing of green bodies
with a multi-level appearance (varying height) using only one upper punch, one lower
punch and a standard filling shoe, the green body will per definition obtain a non-uniform
density distribution.
[0005] One way of solving the above-mentioned problem of non-uniform density, or at least
suppressing/reducing such non-uniformity, would be to adapt the top surface of the
column of powder filled into a die to the shape of the green body to be compacted.
This can be achieved by providing the die with an upper opening through which powder
is filled into the die, wherein said opening is defined by an edge that presents a
curvature other than planar. Powder is filled into the die to such a level that it
is in alignment with the edge that defines said opening.
[0006] EP 2 164 657 discloses a device and a method for manufacturing an end mill, in which there is
formed a down-stepped portion on an upper surface of the die for the purpose of affecting
the density distribution of the compacted green body to be formed in said die. As
a result of the provision of said down-stepped portion, a part of the die that will
define a part of the compacted green body that will have a smaller thickness is filled
with a smaller amount of powder.
EP 2 164 657 does not mention how a powder filling device would be adapted to the non-planar configuration
of the upper surface of the die, but is very clear on the point that there is needed
a specific means for eliminating remaining powder from the top surface of the die,
thereby indicating that there is a remaining problem related to the filling of powder,
namely how to prevent excessive power from being left on the top surface of the die
in the area of the down-stepped portion.
THE OBJECT OF THE INVENTION
[0007] It is an object of the present invention to present a device and a method for the
compaction of a powder into a cutting insert green body which either enables a less
complicated press tool design or enables a control of the density distribution in
the compacted green body by adaption of the curvature of an opening into which powder
is filled into the die by letting the edge, that defines said opening, present a non-planar
curvature, wherein the device and method presents a solution to the problem of how
to prevent powder from being left on the upper surface of the die, in the area affected
by the non-planar curvature, in connection to the filling of the die with powder.
SUMMARY OF THE INVENTION
[0008] The object of the invention is achieved by means of the invention according to claim
1, characterised in that the upper surface of the die presents a path that, in one
direction, extends rectilinearly from a laterally offset point on said upper surface
to said upper opening and covers said upper opening and intersects said edge that
defines said upper opening, wherein said path has a predetermined non-planar profile
in a cross section perpendicularly to said direction, and that the powder-filling
device has a bottom surface that at least partially presents a profile corresponding
to said non-planar profile of said path. In said bottom surface, the powder-filling
device has an opening through which powder is discharged into the die. As a result
of the inventive design, the upper surface of the column of powder that is provided
in the die will present a profile corresponding to said non-planar profile. The non-planar
profile of the upper surface of the powder column is adapted to the geometry of the
green body to be formed. Said profile may, but must not necessarily, resemble the
shape of the upper surface of the green body to be shaped. The non-planar profile
may be designed so as to accomplish a more uniform density distribution in the green
body to be compacted, or so as to accomplish a predetermined symmetry of the density
distribution of the green body to be compacted. However, in specific press designs,
the provision of the non-planar profile on an upper surface of a die part may primarily
be to achieve other advantages, such as simplification of the die design rather than
affecting the uniformity or symmetry of the density distribution of the green body.
[0009] According to the present disclosure, the powder-filling device is enabled to be rectilinearly
moved on and along said path in continuous contact with the upper surface of the die
to and from said opening in said direction, and to overlap said opening. When the
powder-filling device has been removed from the upper opening of the die, an upper
surface of the powder that has been introduced into the die will, preferably, be in
alignment with said path and edge, of the upper surface of the die.
[0010] According to one embodiment, the powder-filling device has a bottom surface with
a path that extends rectilinearly in one direction x and which has a profile in a
cross-section perpendicular to said direction x that corresponds to the predetermined
non-planar profile of said path of the upper surface of the die. The path of the bottom
surface of the powder-filling device is wide enough and long enough to be able to
fully overlap the upper opening in the upper surface of the die. Thereby, the powder-filling
device will be able of sliding along said path on the upper surface of the die and
to fully overlap (cover) the upper opening in the latter, while being in alignment
with the part of the path of the die that encloses said opening. Any excessive powder
in the region of said upper opening on the upper surface of the die part after powder-filling
will be effectively removed by the returning powder-filling device.
[0011] According to one embodiment, at the bottom surface thereof, the powder-filling device
has a bottom opening for discharge of powder into the die, wherein said path of the
bottom surface covers said bottom opening. The opening in the bottom of the powder-filling
device will overlap the upper opening of the die when the powder-filling device is
in a position in which filling of powder is executed.
[0012] According to one embodiment, in at least a direction perpendicular to said direction
x, the bottom opening of the powder-filling device has a size that is larger than
the size of the upper opening in the die.
[0013] According to an alternative embodiment, in at least a direction perpendicular to
said direction x, the bottom opening of the powder-filling device has a size that
is equal to or smaller than the size of the upper opening in the die.
[0014] According to yet another embodiment, a region around said bottom opening in the bottom
surface of the powder-filling device has a curvature corresponding to the curvature
of the edge that defines the upper opening in the upper surface of the die, such that
the bottom surface of the powder-filling device will be in sealing relation with said
edge of the opening in the upper surface of the die when the powder-filling device
is in an operative position on the die in which powder is filled into the die.
[0015] According to one embodiment, the powder-filling device is arranged so as to slide
above and along said path of the upper surface of the die in said direction x in which
said path of the upper surface of the die extends rectilinearly from said laterally
offset point to said upper opening and to overlap said opening, wherein said path
of the powder-filling device is arranged opposite to the path of the upper surface
of the die and extends rectilinearly in the direction x in which the path of the upper
surface of the die extends rectilinearly.
[0016] According to one embodiment, the path of the powder-filling device is arranged so
as to be in supporting contact with said path of the die in connection to said sliding
of the powder-filling device on the upper surface of the die. As an alternative, if
there is no such supporting contact, the distance between the path of the powder filling
device and the path of the die should be kept so small that it prevents powder from
leaking into the space between said paths.
[0017] The non-planar profile of said path, which is also adopted by the upper surface of
the powder column residing in the die after powder-filling and removal of the powder-filling
device, may be adapted to the of the green body to be compacted in order to achieve,
or at least promote, uniform density distribution or symmetric density distribution
of the green body to be compacted and may correspond to or resemble the shape of the
upper surface of the green body to compacted.
[0018] According to one embodiment, the curvature of said edge that defines the upper opening
in the upper surface of the die and intersects with said path corresponds to a curvature
of an upper edge of a green body to be compacted in said die. An upper edge of the
green body is referred to as an upper lateral edge formed in the region in which the
upper punch is as closest to an inner peripheral surface of the die. Typically, said
edge corresponds to a cutting edge of the cutting insert to be formed by sintering
of the green body. The curvature of said edge that defines said opening is not necessarily
exactly identical to the curvature of said edge on the green body. It could, for example,
have larger amplitude than the latter, in order to compensate for the fact that the
green body at high elevation sections of the curvature, obviously representing sections
of the green body with larger height, requires proportionally more powder when compared
to low elevation sections in order to achieve/promote a uniform density distribution
of the green body after compaction.
[0019] According to another embodiment, said punch comprises an abutment surface for abutment
with the powder to be compacted, and an outer peripheral surface, and a punch edge
at the intersection between the abutment surface and the outer peripheral surface,
wherein the punch edge extends with a predetermined curvature around the circumference
of the punch, which curvature corresponds the curvature of the edge that defines the
opening in the upper surface of the die and intersects with said path. This may be
regarded as another way of expressing the same characteristic as defined in the previous
paragraphs, but by connecting the shape of said edge to the shape of the punch rather
than to the shape of a green body to be formed. The edge that defines said opening
is not necessarily exactly identical to the curvature of said punch edge in order
to enable the formation of said path and/or it could have a larger amplitude than
the punch edge.
[0020] Alternatively the curvature of the edge that defines the opening in the upper surface
of the die and, thereby, the profile of the path may be adapted to and resemble the
shape of the abutment surface of the punch rather than just the curvature of the punch
edge, for the purpose of accomplishing a more uniform or symmetric density distribution
in the green body.
[0021] The profile of said path may deviate substantially from the shape of the upper surface
of the green body to be compacted due to several reasons. For example, in cases in
which a press tool member by means of its mere presence and/or geometry obstructs
powder from flowing freely to all regions in the die cavity to be filled, and in those
cases when the obstructed regions might be poorly filled, the profile of said path,
and the curvature of said edge that defines the upper opening of the upper surface
of the die may differ substantially from the shape of the upper surface of the green
body to be compacted and from the curvature of the upper edge of the green body to
be compacted, since the profile of said path and of the edge that defines said opening
are designed in order to compensate for the poor filling caused by the obstructing
press tool member.
[0022] According to one embodiment, said die is subdivided into a first lower die part and
a second upper die part, and said upper surface of the die that comprises said path
is an upper surface of the second upper die part.
[0023] According to one embodiment, the lower die part may be the die part that, together
with an abutment surface of the upper punch and, preferably, an abutment surface of
a lower punch, introduced into the lower die from a position below the lower die,
defines the cavity that determines the geometry of the green body. Said upper die
part is provided with said path in an upper surface thereof. During powder-filling,
the die parts are contiguously arranged and the powder is introduced into the die
through an upper opening covered by said path in the upper die part and up to the
level defined by the edge that defines the upper opening of the upper die part. After
compaction, the upper die part may be removed from the lower die part for the purpose
of facilitating removal of the compacted green body out of the first die part. According
to an alternative embodiment, the lower die part, the upper die part, provided with
said path, an upper punch and a lower punch define the cavity that determines the
geometry of the green body to be compacted. Typically, the green body will have a
waist, of larger dimension than the rest of the green body and that is defined by
the intersection between the lower die part and the upper die part. During powder-filling,
the die parts are contiguously arranged and the powder is introduced into the die
through the upper opening covered by said path in the upper die part and up to the
level defined by an edge that defines said upper opening.
[0024] According to an alternative embodiment, the die is subdivided into a first lower
die part and a second upper die part that are removable from each other, wherein said
upper surface of the die that comprises said path is an upper surface of the first
lower die part. The lower die part may be the die part that, together with an abutment
surface of the upper punch and an abutment surface of a lower punch, introduced into
the lower die from a position below the lower die, defines the cavity that determines
the geometry of the compacted green body. During powder-filling, the die parts are
separated and the powder is introduced by means of a powder-filling device as previously
disclosed into the die through an upper opening covered by said path of the lower
die part and up to the level defined by the edge that defines the upper opening of
the lower die part. The upper die part may have a corresponding path on its lower
surface, such that it may be in alignment with the lower die part and contiguously
arranged in relation thereto during the subsequent compaction procedure. The die parts
are joined such that they are contiguously arranged and the compaction is effected
by displacement of the upper punch downwards through the upper die part and into the
lower die part. A lower opening of the upper die part may be smaller than the upper
opening of the lower die part, such that, during compaction, a thin rim formed by
a lower surface of the upper die part overlaps said upper opening of the lower die
part around said upper opening. The edge that defines said upper opening of the lower
die part may have a curvature corresponding to the curvature of an upper edge of the
green body. Typically, the inner peripheral surface of the lower die part widens towards
said upper opening thereof. During compaction the upper punch is forwarded only a
very short distance into the lower die part until a punch edge of the punch is very
close to the inner peripheral surface of the lower die part. After compaction, the
upper die part may be removed from the lower die part for the purpose of facilitating
removal of the compacted green body out of the first die part. In this case, an important
advantage of the invention is the enablement of a less complicated press tool design,
possibly combined with the advantage of promoting improved density distribution and/or
density distribution symmetry in the green body.
[0025] According to yet another alternative, in which the die is subdivided into a first
lower die part and a second upper die part that are removable from each other, wherein
said upper surface of the die that comprises said path is an upper surface of the
first lower die part, the green body will have a waist of larger dimension than the
rest of the green body, said waist being defined by the intersection between the lower
die part and the upper die part when these are contiguously arranged.
[0026] During powder-filling, the die parts are separated and the powder is introduced into
the die through said upper opening covered by said path of the lower die part and
up to the level defined by the edge that defines the upper opening of the lower die
part covered by said path. A lower opening of the upper die part comprises an edge
with a curvature corresponding to the curvature of the edge that defines the upper
opening in the upper surface of the lower die part. The upper die part may have a
corresponding path on its lower surface, such that it may be in alignment with the
lower die part and contiguously arranged in relation thereto during the subsequent
compaction procedure.
[0027] If profile filling in accordance with the teaching of the invention is not being
applied as suggested here, filling the upper opening covered by said path of the lower
die part will result in leakage of powder and obstruct the die parts from being contiguously
arranged. The powder filling could also be performed through an upper opening of the
upper die part, something that may necessitate a more complicated press tool design.
[0028] The object of the invention is also achieved by a method of compacting powder into
a cutting insert green body, comprising the steps of,
- providing a device according to the invention, as defined hereinbefore or hereinafter,
- positioning the powder-filling device at said laterally offset position on the upper
surface of the die such that said profile of the path of the bottom surface of the
powder-filling device is in alignment with said predetermined non-planar profile of
the path of the die,
- forwarding the powder-filling device to the upper opening of the die by way of sliding
along said path of the upper surface of the die, filling powder into the die,
- removing the powder-filling device from said upper opening by way of sliding along
said path of the die, and
- compacting the powder in the die by means of said punch.
[0029] According to one embodiment, the die is subdivided in a first lower die part and
a second upper die part that are removable from each other, and said upper surface
of the die that comprises said path is an upper surface of the first lower die part,
wherein the method comprises the further steps of removing the second upper die part
from the first lower die part before filling powder into the first lower die part,
and placing the second upper die part on the first lower die part before compacting
the powder by means of said punch.
[0030] Further features and advantages of the present invention will be presented in the
following detailed description and the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
[0031] Embodiments of the present invention will now be described more in detail with reference
to the annexe drawing, on which:
Fig. 1a is a cross section of parts of a device for compaction of powder into cutting
insert green bodies, according to prior art,
Fig. 1b a view from above of a cutting insert green body produced by means of the
device shown in fig. 1a,
Fig. 2 is a cross section corresponding to that of fig. 1, showing parts of a compaction
device according to an embodiment of the invention,
Fig. 3a is a perspective view of parts of a compaction device according to one embodiment
of the invention,
Fig. 3b is a cross-section of parts of the device shown in fig. 3a, separated from
each other,
Fig. 3c is a cross-section corresponding to IIIc-IIIc in fig. 3a
Fig. 4a, is a perspective view of parts of a compaction device according to one embodiment
of the invention,
Fig. 4b is a cross-section of parts of the device shown in fig. 4a, separated from
each other,
Fig. 4c is a cross-section corresponding to IVc-IVc in fig. 4a,
Fig. 5 is cross section corresponding to that of fig. 2, but showing a modified version
of the embodiment shown in fig. 2,
Fig. 6 is a cross section corresponding to that of figs. 1a, 2 and 5, but showing
a further embodiment of the invention,
Figs. 7 and 8 and 9 are an alternative embodiment of a compaction device according
to the invention shown in perspective and/or cross section views,
Fig. 10a shows a cross section of a further alternative embodiment of a compaction
device according to the invention,
Fig. 10b is a representation of a green body compacted by means of the compaction
device shown in fig. 10a,
Fig. 11 shows a cross section of another embodiment of a compaction device according
to the invention,
Fig.12a shows the compaction device shown in fig. 11 in a position ready for filling
of powder into the die thereof,
Fig. 12b is a representation of a green body compacted by means of the compaction
device shown in fig. 11, and
Fig. 13 shows the principle of how to adapt the orientation of the die cavity geometry
in order to enable profile filling in accordance with the teaching of the present
disclosure for a specific green body geometry
DETAILED DESCRIPTION OF THE INVENTION
[0032] Fig. 1a shows essential parts of a compaction device according to prior art, suitable
for the pressing of powder into cutting insert green bodies. The compaction device
comprises a die 1, an upper punch 2 and a lower punch 3. The die 1 defines a hollow
space into which the upper punch 2 is introduced from above and the lower punch 3
is introduced from below. When powder, here indicated with 5, is introduced into the
die 1, this is usually done by means of a powder-filling device (not shown) which
slides on an upper surface of the die 1 to a position above an upper opening therein
and fills a die cavity defined by the die 1 and the lower punch 3 up to the level
of the upper surface of the die 1, as shown in fig. 1a. In fig. 1a there is also indicated
the geometry of a green body, here indicated with 6, and the position that the latter
will take in the die 1 when the powder 5 is compacted through a downward motion of
the upper punch 2 and upward motion of the lower punch 3 from the respective positions
thereof shown in fig. 1a. Before introduction of the upper punch into the die 1, the
lower punch 3 is normally retracted slightly downwards, such that the upper surface
of the column of powder is lowered in relation to an upper surface of the die 1. The
geometry of the green body shown in fig. 1a, is further shown in fig. 1b.
[0033] In this specific example shown in fig. 1a the ratio between the total height of the
powder columns at section A and B (H) and the final height of the compacted green
body at A and B (hA, hB) varies approximately from 2.5 at A (H/hA=2.5) to 1.7 at B
(H/hB=1.7). Section A will thus obtain a relative high density and section B a relative
low density, all because the powder-filling device leaves a powder column with a flat
top surface behind after filling the die cavity.
[0034] The present invention suggests a way of reducing/suppressing the density variations
of prior art upon compaction of powder into a cutting insert green body by using a
filling method and device hereinafter named a
profile filling method and device. By using the profile filling method by means of a custom
designed powder-filling device, die table (optional) and die, the powder can be shaped
into a specific profile using standard filling movements of a press. The profile can
be chosen in such a way that the powder columns at section A, B and anywhere else
along the insert obtain the same or similar compaction ratio, thereby significantly
uniforming the density distribution in the green body.
[0035] Fig. 2 shows a cross section of essential parts of a compaction device according
to an embodiment of the present invention, aimed for the pressing of powder into cutting
insert green bodies. The shown parts may be identical to those shown in fig 1a in
the sense that they are able of forming a green body of corresponding shape. The characterising
difference is the design of the upper surface of the die, which however only reveals
itself in fig. 2 by the fact that the column of powder shown therein has a different
shape than in fig. 1a. However, in order to clarify that the parts shown in fig. 2
belong to a device according to the present disclosure, they are given other numbers.
Thus, there is a die 7, an upper punch 8 and a lower punch 9. As can be seen, the
powder 10 is shaped into a predetermined profile. The profile is chosen such that
each of the sections A, B and anywhere else along the insert obtain the same or similar
compaction ratios (HA/hA=HB/hB=2.5). Crucial for the generation of the predetermined
shape of the powder column is the shape of the upper surface of the die, as will be
seen in fig. 3a. The green body 11 may have the same geometry as the green body 6
shown in fig. 1a, since the inner peripheral surface of the die 7 that, together with
the upper punch 8 and the lower punch 9, defines the cavity which defines the shape
of the green body 11 is the same as the one shown in fig. 1a.
[0036] Fig. 3a is another figure showing essential parts of the compaction device according
to an embodiment of the invention shown in fig. 2. The device presents features that
make it suitable for forming the profile of the powder shown in fig. 2. Accordingly,
the compaction device shown in figs. 2 and 3a-c comprises a die 7 for receiving powder
10, at least one punch (here at least the upper punch 8) for compacting said powder
10 received by said die 7 (the punches are though not shown in fig. 3a-c), and a powder-filling
device 12 for filling powder into the die 7. In an upper surface 13 thereof, the die
7 comprises an upper opening 14 through which said powder 10 is introduced into the
die 7 and through which said punch 8 shown in fig. 2 may be forwarded into the die
7 for the purpose of compacting powder 10 introduced into the die 7. The opening 14
is defined by an edge 15 that presents a curvature other than planar. The upper surface
13 of the die 7 presents a path that, at least in one direction x, extends rectilinearly
from a laterally offset point on said upper surface 13 to said upper opening 14 and
covers said upper opening 14 and intersects said edge 15 that defines said upper opening
14, wherein said path has a predetermined non-planar profile in a cross section perpendicularly
to said direction x, and wherein the powder-filling device 12 has a bottom surface
that at least partially presents a profile corresponding to said non-planar profile.
At least a part of said path may be defined by a rim or the like, as shown in fig.
3a, that extends in said direction x and may be removable from the upper surface of
the die 7, for possible exchange thereof. In fig. 3a, there is also shown a die table
16 that surrounds the die 7 and works as a further support surface for the powder-filling
device 12. Preferably, the upper surface of the table 16 is in alignment with the
upper surface 13 of the die 7. The table 16 presents an extension of said path on
the upper surface 13 of the die 7, thereby enabling further sliding of the powder-filling
device 12 away from the die 7. Depending on the design of the die 7, the presence
of the table 16 is optional.
[0037] The powder-filling device 12 has a bottom surface 17 (see fig. 3b) with a path that
extends rectilinearly in one direction and which has a profile in a cross-section
perpendicular to said direction that corresponds to the predetermined non-planar profile
of said path of the upper surface 13 of the die 7. The powder-filling device 12 has
a bottom opening 18 for discharge of powder into the die 7, and said path of the bottom
surface 17 covers said bottom opening 18.
[0038] When powder is to be filled into the die 7 through the upper opening 14 thereof,
the powder-filling device 12 is positioned on the path of the die 7 such that the
path of the bottom surface 17 of the powder-filling device 12 overlaps and is in alignment
with the path of the die 7 in said direction x (see fig. 3c). The powder-filling device
12 is slid along the path of the die 7 in said direction x to a position in which
the opening 18 in the bottom surface 17 thereof overlaps the upper opening 14 of the
die 7, and powder is filled into said upper opening at least to the level of the edge
15 that defines said upper opening. Then the powder filling device 12 is removed from
the upper opening 14 of the die by means of sliding along said path on the upper surface
of the die 7, either backwards towards the offset position from which it started or
forwards, if the path on the upper surface 13 of the die 7 continues beyond the upper
opening 14. The powder-filling device 12 leaves behind it an upper surface 13 of the
die 7 that is practically free from powder, except for the opening 14, which is has
powder up to a level that is in alignment with said path on the upper surface 13 of
the die 7. Thus the powder column will have an upper surface with a profile corresponding
to the profile of said path, which may be the profile shown fig. 2. The upper opening
14 of the die is now exposed for introduction of the upper punch 8 from above for
the purpose of compacting powder. Before the upper punch 8 is introduced into the
upper opening 14, a lower punch introduced from below into the die may be retracted
downwards such that the powder in the die is displaced downwards, and the upper surface
of powder is lowered to a position not in alignment but below the level of said path
of the upper surface of the die. Thereby, the upper punch is enabled to enter the
die without immediately pressing powder out of the die. However, the above-mentioned
profile of the upper surface of the powder is maintained after said lowering thereof.
[0039] Traditionally, the bottom opening of the powder-filling device 12 would have a size
that is larger than the size of the upper opening in the die, at least in a direction
perpendicular to said direction x. However, in order to further suppress the risk
of having remaining powder on the upper surface 13 of the die 7 after removal of the
powder-filling device 12 from the filling position thereof to a laterally offset position,
it is also suggested, as an alternative, that, at least in a direction perpendicular
to the direction x, the bottom opening 18 of the powder-filling device 12 has a size
that is equal to or smaller than the size of the upper opening 13 in the die 7 (see
fig. 3b and 3c). It is preferred that a region around said bottom opening 18 in the
bottom surface 17 of the powder-filling device 12 has a curvature corresponding to
the curvature of the edge 15 that defines the upper opening 14 in the upper surface
13 of the die 7, such that the bottom surface 17 of the powder-filling device 12 will
be in sealing relation with said edge 15 of the opening 14 in the upper surface 13
of the die 7 when the powder-filling device 12 is in an operative position on the
die 7 in which powder is filled into the die 7.
[0040] Figs. 4a-4c shows an alternative embodiment for the compaction of an alternative
green body (not shown) of the compaction device shown in figs. 3a-c, in which said
edge that defines the opening in the upper surface of the die, the path of the upper
surface of the die and the path of the lower surface of the powder-filling device
have a different profile than in the embodiment shown in figs. 3a-c, such that the
profile of upper surface of the column of powder after powder-filling will be different
from the one shown in fig. 2. However, since the components, apart from that difference,
are identical to those shown in figs. 3a-c, they are given the same reference numbers
as those in figs. 3a-c added with the symbol '. The operation and functionality of
the device shown in figs. 4a-c is the same as for the device shown in figs. 3a-c.
[0041] In practice, it is probably not possible to give the whole profile of the upper surface
of the power column the theoretically correct shape due to complex green body design
features, collapse of steep profile slopes, collapse of sharp profile corners, etc.
However, a modified profile, compensated for the possible issues mentioned above,
should still give a significant improvement regarding density distribution. Fig. 5
is a representation of an alternative to the profile shown in fig. 2. The punches
are identical to those shown in fig. 2, and are thus given the same reference numbers
as those in fig. 2. The die is however different from the die 7 shown in fig. 2 in
that it has an edge that defines an upper opening thereof that is different from that
of fig. 1 in the respect that it has a curvature that will result in the profile shown
in fig. 5. The die is therefore given the reference number 19. The path in the upper
surface of the die has profile perpendicularly to said direction x that corresponds
to the profile of the upper surface of the powder column shown in fig. 5, and the
powder-filling device has a path on its bottom surface with a corresponding profile,
all in accordance with the essential teaching of the invention.
[0042] Fig. 6 shows a further embodiment in which the die is subdivided into a first lower
die part 7a and a second upper die part 7b, and said upper surface 13 of the die that
comprises said path is an upper surface 13 of the second upper die part 7b. The reasons
for using a die subdivided into a lower die part and an upper die part may be diverse
and the upper die part may be arranged so as to be displaced relative to the lower
die part during the pressing operation or not. One reason may be as follows: The length
of the upper negative section of a compaction tool for positive inserts is here indicated
with HvN. It is of interest to be able to change this length, because a fixed length
could limit the possibility to optimize the press cycle for powders with different
filling properties that result in relatively large fill heights. In the case of profile
filling, the relatively cheap wear plate that forms an upper die part 7b of the die
potentially could be manufactured in a variety of heights (HvP), giving the possibility
to optimize the HvN dimension.
[0043] There may be further and other reasons for using a die which is subdivided into a
lower die part and an upper die part. Figs. 7 and 8 and 9 show an embodiment of such
a device which comprises a die comprised by a lower die part 20 and an upper die part
21. There is also provided a lower punch 22 and an upper punch 23. The upper die part
21 comprises an upper surface 24 which comprises an opening 25 defined by an edge
26 which is non-planar. On the upper surface 24 there is provided a path which extends
rectilinearly in direction x and has a predetermined non-flat profile perpendicular
to said direction. The path overlaps the upper opening 25 and intersects the edge
26. In accordance with the teaching of the invention, the device should be provided
with a powder-filling device (not shown) that has a lower surface with a path with
a profile corresponding to the profile of the upper surface 24 of the upper die part
21, such that it can fit into the path of the upper surface 24 of the upper die part
21. Powder is introduced into the die by means of the powder-filling device in accordance
with the teaching already described. In connection to compaction of powder introduced
into a cavity defined by the lower punch 22, the lower die part 20 and the upper die
part 21, the upper punch 23 is introduced into the upper die part 21 through the opening
25 and forwarded such a distance into the lower die part 20 that a lower edge of the
upper punch 23 is so close to the sloping inner peripheral surface of the lower die
part 20 that the green body is defined by an upper surface of the lower punch 22,
the inner peripheral surface of the lower die part 20 and a lower surface of the upper
punch 23. Above the level to which the lower lateral edge 27 of the upper punch 23
is forwarded there will be a space which is not occupied by the green body but will
have the function of a release portion that permits lateral expansion of the green
body as the latter is taken out of the lower die part. Before taking out the green
body from the lower die part 20, the upper die part 21 is removed from the lower die
part 20, such that the green body only has to pass a release portion defined by the
inner peripheral surface of the lower die part 20 above said level, and not pass through
a punch channel provided in the upper die part 23.
[0044] Figs. 9 is a further view of the device for compaction of powder to a green body
shown in figs. 7 and 8.
[0045] Fig. 10a shows an embodiment according to which, as an alternative to powder-filling
through an upper opening in the upper flat surface of an upper die part which can
be flat enabling filling with a standard filling device with a lower flat surface,
powder-filling may be done through an upper opening 28 in the upper surface 29 of
the lower die part 30. A path in accordance with the general teaching of the present
invention is then arranged in the upper surface 29 of the lower die part 30, and the
device comprises a powder-filling device 31 with a lower surface that presents a corresponding
path or cross-section in accordance with the general teaching of the present invention
and is arranged to be slid from a laterally offset position to a powder filling position
along said path of the lower die part 30. An upper die part 32 may, preferably, have
a corresponding path on its lower surface, such that it may be in alignment with the
lower die part 30 and contiguously arranged in relation thereto during the subsequent
compaction procedure in which an upper punch 33 is forwarded through the upper die
part 32 into the lower die part 30. The upper die part 32 is removable from the lower
die part 30, and removed from the latter during said powder-filling, and contiguously
arranged in relation thereto during compaction. During powder-filling, a lower punch
is retracted downwards in order to enable receipt of the amount of powder needed for
the subsequent compaction. Prior to the compaction, the lower punch is forwarded upwards
to transfer some of the powder into the upper die part 32 before the powder is compacted
by both the upper punch 33 and the lower punch.
[0046] After compaction, the upper die part 32 is once again removed from the lower die
part 30 in order to enable ejection of the compacted green body, indicated with 34
in fig. 10b, from the lower die part 32 through the upper opening 28 in the upper
surface 29 thereof. The compacted green body 34 has an upper lateral edge 35 that
has a curvature corresponding to the curvature of an edge that defines the upper opening
28 in the upper surface 29 of the lower die part 30.
[0047] In accordance with the teaching of figs. 11, 12a and 12b the present invention may
also be applied to cases in which the die is subdivided into a lower die part 36 and
an upper die part 37 and in which the cavity 38 that defines the shape of the compacted
green body is defined by an upper surface of a lower punch 39, the lower surface of
an upper punch 40 and the inner peripheral surfaces of both the lower and the upper
die parts 36, 37. Typically, the intersection line 41 between an upper opening in
the lower die part and a lower opening in the upper die part defines a waist of maximum
width of the green body 42 to be compacted. The compacted green body 42 is shown in
fig. 12b. An upper surface 43 of the lower die part 36 is provided with an opening
44 through which powder is introduced into the die by means of a powder-filling device
45. A path in accordance with the general teaching of the invention defined hereinbefore
is provided in said upper surface 43, as well as an upper opening 44. A powder-filling
device 45 according to the teaching of the present invention is arranged for the filling
of powder into said opening. During powder-filling, the upper die part 37 is separated
from the lower die part 36 to enable the powder-filling device 45 to slide on and
along said path to its powder-filling position above the opening 44 in upper surface
43. The lower punch 39 is temporarily retracted downwards to enable receipt of the
amount of powder necessary for the subsequent compaction. Prior to the compaction
the lower punch 39 is forwarded upwards to transfer some of the powder into the upper
die part 37 before the powder is compacted by both the upper punch 40 and the lower
punch 39.
[0048] After completed powder-filling, the powder-filling device 45 is removed from said
opening 44 by sliding along said path, and the upper die part 37 is positioned contiguously
on top of the lower die part 36. During compaction, the upper punch 33 is moved towards
the upper opening 44 in the lower die part 36 and towards the space that will define
said cavity 38.
[0049] As a further alternative, said path could instead be arranged in the upper surface
of the upper die part, and the powder-filling device could be arranged to fill powder
into the die from an opening in the upper surface of the upper die part, provided
that the upper punch is able to be removed sufficiently upwards to enable such powder-filling.
[0050] Fig. 13 shows a cutting insert produced from a green body, such as the green body
by way of sintering, wherein it is obviated that the invention, in order to be realised,
may require a specific positioning of said path on the upper surface of the die in
relation to a specific geometry of a green body which is defined by an inner peripheral
surface of the die. Initially it may not be obvious that the insert shown in fig.
13 is a candidate for the filling method according to the present invention. However,
by changing the orientation of the insert (i.e. the cavity that defines the geometry
of the green body to be produced in the die) with approximately 60 degrees it is apparent
that this geometry could benefit from profile filling (see figure 13).
1. A device for manufacturing a cutting insert green body (6, 11) by compacting a powder
(10), said device comprising:
- a die (7; 7'; 7a, 7b; 19; 20, 21) for receiving said powder (10)
- at least one punch (8; 23) for compacting said powder (10) received by said die
(7; 7'; 7a, 7b; 19; 20, 21), and
- a powder-filling device (12; 12') for filling powder (10) into the die (7; 7'; 7a,
7b; 19; 20, 21),
- wherein, in an upper surface (13; 13'; 24) of at least one part of the die (7; 7';
7a, 7b; 19; 20, 21), the die comprises an upper opening (14; 14'; 25) through which
said powder (10) is introduced into the die (7; 7'; 7a, 7b; 19; 20, 21) and through
which or towards which said punch (8; 23) may be forwarded into the die (7; 7'; 7a,
7b; 19; 20, 21) for the purpose of compacting powder (10) introduced into the die
(7; 7'; 7a, 7b; 19; 20, 21),
- wherein said upper opening (14; 14'; 25) is defined by an edge (15; 15'; 26) that
presents a curvature other than planar, characterised in that the upper surface (13; 13'; 24) of the die (7; 7'; 7a, 7b; 19; 20, 21) presents a
path that, in one direction (x), extends rectilinearly from a laterally offset point
on said upper surface (13; 13'; 24) to said upper opening (14; 14'; 25) and covers
said upper opening (14; 14'; 25) and intersects said edge (15; 15'; 26) that defines
said upper opening (14; 14'; 25), wherein said path has a non-planar profile in a
cross section perpendicularly to said direction (x), and that the powder-filling device
(12; 12') has a bottom surface (17, 17') that at least partially presents a profile
corresponding to said non-planar profile of said path.
2. A device according to claim 1, characterised in that the powder-filling device (12; 12') has a bottom surface (17, 17') with a path that
extends rectilinearly in said direction (x) and which has a profile in a cross-section
perpendicular to said direction (x) that corresponds to the predetermined non-planar
profile of said path of the upper surface (13; 13'; 24) of the die (7; 7'; 7a, 7b;
19; 20, 21).
3. A device according to claim 2, characterised in that, in the bottom surface (17, 17') thereof, the powder-filling device (12; 12') has
a bottom opening for discharge of powder (10) into the die (7; 7'; 7a, 7b; 19; 20,
21), and that said path of the bottom surface (17, 17') covers said bottom opening.
4. A device according to claim 3, characterised in that, at least in a direction perpendicular to said direction x, the bottom opening of
the powder-filling device (12; 12') has a size that is larger than the size of the
upper opening (14; 14'; 25) in the die (7; 7'; 7a, 7b; 19; 20, 21).
5. A device according to claim 3, characterised in that, at least in a direction perpendicular to said direction x, the bottom opening of
the powder-filling device (12; 12') has a size that is equal to or smaller than the
size of the upper opening (14; 14'; 25) in the die (7; 7'; 7a, 7b; 19; 20, 21).
6. A device according to claim 5, characterised in that a region around said bottom opening in the bottom surface (17, 17') of the powder-filling
device (12; 12') has a curvature corresponding to the curvature of the edge (15; 15';
26) that defines the upper opening (14; 14'; 25) in the upper surface (13; 13'; 24)
of the die (7; 7'; 7a, 7b; 19; 20, 21), such that the bottom surface (17, 17') of
the powder-filling device (12; 12') will be in sealing relation with said edge (15;
15'; 26) of the opening in the upper surface (13; 13'; 24) of the die (7; 7'; 7a,
7b; 19; 20, 21) when the powder-filling device (12; 12') is in an operative position
on the die (7; 7'; 7a, 7b; 19; 20, 21) in which powder (10) is filled into the die
(7; 7'; 7a, 7b; 19; 20, 21).
7. A device according to any one of claims 2-6, characterised in that the powder-filling device (12; 12') is arranged so as to slide above and along said
path of the upper surface (13; 13'; 24) of the die (7; 7'; 7a, 7b; 19; 20, 21) in
said direction (x) in which said path of the upper surface (13; 13'; 24) of the die
(7; 7'; 7a, 7b; 19; 20, 21) extends rectilinearly from said laterally offset point
to said upper opening (14; 14'; 25) and to fully overlap said opening, wherein said
path of the powder-filling device (12; 12') is arranged opposite to the path of the
upper surface (13; 13'; 24) of the die (7; 7'; 7a, 7b; 19; 20, 21) and extends rectilinearly
in the direction (x) in which the path of the upper surface (13; 13'; 24) of the die
(7; 7'; 7a, 7b; 19; 20, 21) extends rectilinearly.
8. A device according to claim 7, characterised in that the path of the powder-filling device (12; 12') is arranged so as to be in supporting
contact with said path of the die (7; 7'; 7a, 7b; 19; 20, 21) in connection to said
sliding of the powder-filling device (12; 12') on the upper surface (13; 13'; 24)
of the die (7; 7'; 7a, 7b; 19; 20, 21).
9. A device according to any one of claims 1-8, characterised in that the curvature of said edge (15; 15'; 26) that defines the upper opening (14; 14';
25) in the upper surface of the die (7; 7'; 7a, 7b; 19; 20, 21) corresponds to a curvature
of an upper edge of a green body (6) to be compacted in said die (7; 7'; 7a, 7b; 19;
20, 21).
10. A device according to any one of claims 1-9, characterised in that said punch (8; 23) comprises an abutment surface for abutment with the powder (10)
to be compacted, and an outer peripheral surface, and a punch edge at the intersection
between the abutment surface and the outer peripheral surface, wherein the punch edge
extends with a predetermined curvature around the circumference of the punch (8; 23),
which curvature corresponds to the curvature of the edge (15; 15'; 26) that defines
the upper opening (14; 14'; 25) in the upper surface (13; 13'; 24) of the die (7;
7'; 7a, 7b; 19; 20, 21).
11. A device according to any one of claims 1-10, characterised in that said die (7; 20, 21) is subdivided into a first lower die part (7a; 20) and a second
upper die part (7b, 21), and said upper surface of the die that comprises said upper
opening and said path is an upper surface of the second upper die part (7b; 21).
12. A device according to claim 11, characterised in that said die is subdivided into a first lower die part (30; 36) and a second upper die
part (32; 37) that are removable from each other, and said upper surface of the die
part that comprises said path is an upper surface (29; 43) of the first lower die
part (30; 36).
13. A method of compacting a powder (10) into a cutting insert green body (6), comprising
the steps of,
- providing a device according to any one of claims 1-14,
- positioning the powder-filling device (12; 12') at said laterally offset position
on the upper surface (13; 13'; 24) of the die (7; 7'; 7a, 7b; 19; 20, 21) such that
said profile of the path of the bottom surface (17, 17') of the powder-filling device
(12; 12') is in alignment with said predetermined non-planar profile of the path of
the die (7; 7'; 7a, 7b; 19; 20, 21),
- forwarding the powder-filling device (12; 12') to the upper opening (14; 14'; 25)
of the die (7; 7'; 7a, 7b; 19; 20, 21) by way of sliding along said path of the upper
surface (13; 13'; 24) of the die (7; 7'; 7a, 7b; 19; 20, 21),
- filling powder (10) into the die (7; 7'; 7a, 7b; 19; 20, 21),
- removing the powder-filling device (12; 12') from said upper opening (14; 14'; 25)
by way of sliding along said path of the die (7; 7'; 7a, 7b; 19; 20, 21), and
- compacting the powder (10) in the die (7; 7'; 7a, 7b; 19; 20, 21) by means of said
punch (8; 23).
14. A method according to claim 13, characterised in that the die is subdivided in a first lower die part (30; 36) and a second upper die part
(32; 37) that are removable from each other, and that said upper surface (29; 43)
of the die part that comprises said path is an upper surface (29; 43) of the first
lower die part (30; 36), wherein the method comprises the further steps of removing
the second upper die part (32; 37) from the first lower die part (32; 36) before filling
powder into the first lower die part (30; 36), and placing the second upper die part
(32; 37) on the first lower die part (30; 36) before compacting the powder by means
of said punch (33; 40).