U.S. patent application number 11/624037 was filed with the patent office on 2007-11-22 for multiple part compaction.
Invention is credited to Mark Haiko, Roger Lawcock, Brian Morris.
Application Number | 20070269334 11/624037 |
Document ID | / |
Family ID | 38712163 |
Filed Date | 2007-11-22 |
United States Patent
Application |
20070269334 |
Kind Code |
A1 |
Lawcock; Roger ; et
al. |
November 22, 2007 |
MULTIPLE PART COMPACTION
Abstract
A compaction tool assembly is provided that uses multiple die
cavities and a single compaction stroke for simultaneously forming
multiple discrete powdered metal components. The tooling includes a
plurality of punches and corresponding die cavities, and a single
compaction stroke operates the punches to compact powdered metal
contained by the die cavities to form the components. Preferably
the punch pairs are arranged concentrically to balance compaction
forces and die stresses.
Inventors: |
Lawcock; Roger; (Burlington,
CA) ; Haiko; Mark; (Burlington, CA) ; Morris;
Brian; (Aurora, CA) |
Correspondence
Address: |
BLAKE, CASSELS & GRAYDON LLP
BOX 25, COMMERCE COURT WEST
199 BAY STREET, SUITE 2800
TORONTO
ON
M5L 1A9
CA
|
Family ID: |
38712163 |
Appl. No.: |
11/624037 |
Filed: |
January 17, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60759046 |
Jan 17, 2006 |
|
|
|
Current U.S.
Class: |
419/68 ;
425/78 |
Current CPC
Class: |
B22F 2998/00 20130101;
B22F 3/04 20130101; B22F 2003/033 20130101; B30B 11/02 20130101;
C22C 33/0264 20130101; B22F 5/08 20130101; B22F 2998/00
20130101 |
Class at
Publication: |
419/068 ;
425/078 |
International
Class: |
B22F 3/04 20060101
B22F003/04 |
Claims
1. A tooling assembly for forming metal powder components
comprising a plurality of punches operating during a single
compaction stroke to compress metal powder contained by a plurality
of corresponding die cavities to simultaneously produce a plurality
of discrete metal powder components.
2. A tooling assembly according to claim 1 wherein said punches are
concentrically arranged about a central core, and said parts are
differently sized.
3. A tooling assembly according to claim 1 wherein said punches and
said dies are arranged side-by-side.
4. A tooling assembly according to claim 3 wherein said parts are
the same size.
5. A tooling assembly according to claim 1 wherein said punches are
hydraulically controlled.
6. A tooling assembly according to claim 1 comprising a die platen
for said corresponding die cavities, wherein said die platen
comprises a plurality of die punches being moveable within said
platen to vary the size of said die cavities.
7. A tooling assembly according to claim 6 wherein said die platen
provides a substantially flush surface surrounding said die
cavities, and said die punches are moveable to be aligned with said
flush surface to facilitate removal of said parts from said tooling
assembly.
8. A tooling assembly according to claim 7 comprising a pushing
mechanism for removing said parts.
9. A tooling assembly according to claim 7 comprising a control
system for controlling movement of said punches and said die
punches.
10. A compaction press comprising the tooling assembly of claim
1.
11. A method for simultaneously forming a plurality of discrete
metal powder components comprising: arranging a plurality of
punches and a plurality of corresponding die cavities; containing
metal powder in said die cavities; and operating said punches
during a single compaction stroke to simultaneously compact said
metal powder within said die cavities to produce said
components.
12. A method according to claim 11 wherein said punches and said
die cavities are arranged concentrically about a central core, and
said parts are differently sized.
13. A method according to claim 11 wherein said punches and said
dies are arranged side-by-side.
14. A method according to claim 13 wherein said parts are the same
size.
15. A method according to claim 11 wherein said operating is
hydraulically controlled.
16. A method according to claim 11 wherein said arranging comprises
providing a die platen for said die cavities, said die platen
comprising a plurality of die punches; and moving said die punches
within said die platen to accommodate a predetermined amount of
said metal powder.
17. A method according to claim 16 wherein said die platen provides
a substantially flush surface surrounding said die cavities, and
said method comprises moving said die punches to be aligned with
said flush surface to facilitate removal of said parts from said
tooling assembly following said operating.
18. A method according to claim 17 comprising removing said parts
using a pushing mechanism.
19. A method according to claim 17 comprising providing a control
system for controlling movement of said die punches and said
punches.
20. A method according to claim 11 wherein said arranging is
applied to a compaction press.
Description
This application claims priority from U.S. application Ser. No.
60/759,046 filed on Jan. 17, 2006.
FIELD OF THE INVENTION
[0001] The present invention relates to metal powder
compaction.
DESCRIPTION OF THE PRIOR ART
[0002] The use of metal powder compaction as a process for
facilitating the high volume manufacture of components is a well
known and established manufacturing method. Metal powder compaction
is often used to manufacture articles due to its ability to
economically produce a relatively large volume of articles.
[0003] Typically, a metal powder is placed in a die set essentially
having the finished shape of the article. The powder is then
compressed to a "green" state, sintered at an elevated temperature,
and then finished to final dimensions.
[0004] Compaction presses are built to provide maximum designed
compacting forces. For example, common compacting capacities are 50
tons, 150 tons, up to even 1500 tons. The actual allowable force
provided by a compacting press is specific to the design and
preferences of the manufacturer of the press.
[0005] The required compacting force for a particular article
relies upon the geometry of the article being produced, the
compressibility behaviour of the power being processed, and the
desired density of the article. For example, gears may be compacted
to have a density within the range of 6.6 to 7.5 g/cc, more
typically around 7.0 g/cc. The required compaction force can be
determined using knowledge of the projected area of the gear and
the compressibility characteristics of the powder used to form the
gear. The required compaction pressure can be determined from a
powder compressibility curve as shown in FIG. 1.
[0006] For the example shown in FIG. 1, to achieve a compacted
density of 7.0 g/cc, a pressure of approximately 40 tsi is
required. The compaction force may be calculated as: Compaction
Force=Part Area.times.Required Pressure.
[0007] Accordingly, to compact a gear having an area of 1 sq in,
the compaction force required would be 40 tons. Similarly, for a
larger gear having an area of 4 sq in, the compaction force
required would be 160 tons.
[0008] In a manufacturing facility it is typically not economically
or logistically feasible to purchase and install a different
compaction press that is sized for each specific article that may
need to be manufactured at the facility. In order to overcome this
obstacle, a common practice is to install a press that is capable
of pressing at or above the maximum requirements for any particular
article being manufactured, which results in sometimes only a
fraction of the available compaction force being utilized. For
example, to accommodate the above gears requiring 40 ton and 160
ton compaction forces respectively, a press with a maximum capacity
of 250 tons may be used.
[0009] There exists numerous prior art methods and apparatus for
performing metal powder compaction. For example, U.S. Pat. No.
4,183,238 to Maillet teaches a double-acting press for
deep-stamping that uses a plurality of passes; U.S. Pat. No.
5,043,123 to Gormanns et al. teaches a method of coaxially
compacting dissimilar powders to form a single composite body; and
U.S. Pat. No. 5,238,375 to Hirai uses a nest of rams acting against
a common base for producing stepped articles.
[0010] However, such prior art methods and apparatus do not
overcome the above-described disadvantages, in particular, the need
to either install different machines for different articles or to
utilize a machine at below its capabilities in order that the
machine may be capable of pressing other larger articles.
[0011] Accordingly, maximum utilization of the machine is not
achieved and throughput is limited to the cycle time of the press
being used.
[0012] It is therefore an object of the present invention to
obviate or mitigate at least one of the above-mentioned
disadvantages.
SUMMARY OF THE INVENTION
[0013] In one aspect, a tooling assembly for forming metal powder
components is provided comprising a plurality of punches operating
during a single compaction stroke to compress powdered metal
contained by a plurality of corresponding die cavities to
simultaneously produce a plurality of discrete powdered metal
components.
[0014] In another aspect, a method is provided for simultaneously
forming a plurality of discrete metal powder components. The method
comprises the steps of arranging a plurality of punches and a
plurality of corresponding die cavities, containing metal powder in
the die cavities, and operating the punches during a single
compaction stroke to simultaneously compact the metal powder within
the die cavities to produce the components.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] An embodiment of the invention will now be described by way
of example only with reference to the appended drawings
wherein:
[0016] FIG. 1 is a graph showing a powder compressibility
curve;
[0017] FIG. 2 is a sectional elevation view of a tooling
arrangement for two-part compaction;
[0018] FIG. 3 is a schematic sectional elevation view of the die
and tooling shown in FIG. 2;
[0019] FIG. 4 is a schematic sectional plan view of the lower
punches of the tooling shown in FIG. 3 along line IV-IV;
[0020] FIG. 5 shows a series of schematic views illustrating
operation of the tooling shown in FIG. 3;
[0021] FIG. 6 is a plan view of a pair of pressed gears using the
tooling of FIG. 2; and
[0022] FIG. 7 is a schematic view of another embodiment of a
tooling arrangement for two-part compaction.
DETAILED DESCRIPTION OF THE INVENTION
[0023] Referring therefore to FIG. 2, a multiple part compaction
tooling assembly is generally denoted by numeral 10. The tooling 10
shown in FIG. 2 is arranged to simultaneously press a pair of parts
A, B. However, it will be appreciated that the tooling 10 may also
be arranged to compact more than two parts as desired, and may also
be used to compact parts individually. In general, the compacting
press (not shown) utilizing the tooling 10 may be a mechanical
press or a hydraulic press, and shall not be limited to either.
[0024] In general, each part A, B, is compacted within a discrete
die set having a die to define the periphery of the particular
part, and a pair of punches to cooperate with the die and compress
powder in the die. The die sets may be nested (as shown in FIG. 2),
one within the other, where dimensions permit, to form parts A, B
such as the gears shown in FIG. 6 or may be arranged adjacent to
one another (as shown in FIG. 7). In either case, the individual
die sets define individual, discrete components, as will be
explained more fully below.
[0025] The tooling assembly 10 includes a moveable upper punch
portion 12 and a moveable lower punch portion 14. The upper portion
12 includes a removable inner top punch 16 and a removable outer
top punch I8 that move in tandem.
[0026] In this example, the inner punch 16 and outer punch 18 are
concentrically arranged about centerline C and each are formed to
transfer a particular profile to the separate and distinct parts A
and B, that are ultimately produced. It will be appreciated that
any profile may be used as desired, and that the punches 16 and 18
are interchangeable to accommodate different punches for different
applications. It will also be appreciated that either or both of
the upper punches 16, 18 and lower punches 30, 32 may be formed as
necessary, in order to define the finished shape of the desired
part. The lower punches 30, 32 may also be referred to as die
punches or bottom punches.
[0027] The lower portion 14 includes a die platen 20, the upper
surface of which defines datum D; a central tool core 22; and an
annular central punch 24 disposed therebetween. The central punch
24 connects to support 25 and defines an annular inner die cavity
26 and an annular outer die cavity 28 that are distinct and
separate from each other. The inner bottom punch 30, connected to
support 31, can slide within the inner die cavity 26 in an axial
direction, and the outer bottom punch 32, connected to support 33,
can slide within the outer die cavity 28 in an axial direction. The
bottom punches 30 and 32 are controlled in the tooling assembly 10,
and are held stationary at respective axial positions in order to
define the respective sizes of the discrete die cavities 26, 28 for
containing the respective quantities of metal powder for each
discrete part (see shaded portions of FIG. 2). The die cavities 26
and 28 are individually filled with metal powder (as shown to the
left of centerline C) prior to compaction thereof for producing a
pair of discrete compacted metal powder components (as shown to the
right of centerline C). Accordingly, punches 16 and 30 and die
chamber 26 defines one discrete die set, and punches 18 and 32 and
die chamber 28 define another discrete die set.
[0028] The tooling 10 is arranged to distribute the compaction
force of the compacting press between the inner punch 30 and outer
punch 32 such that this force equals the force applied by the upper
portion 12. The distribution of compaction force depends upon the
area of each part, and the desired density of the compacted part.
Typically, the outer punch 32 will utilize a greater portion of the
compaction force than the inner punch 30 due to the relative sizes
of the parts (assuming that they use similar materials and are
compacted to similar densities).
[0029] A schematic representation of the tooling 10 is shown in
FIGS. 3 and 4. A series of views of the portion of the tooling 10
to the right of centerline C, is shown in FIG. 5, illustrating
operation thereof. To illustrate the relative movements of the
parts, datum D is also shown in FIG. 5.
[0030] Referring now to the series of views in FIG. 5, a single
stroke of the compaction press causes the tooling 10 to compress
each quantity of powered metal in the discrete cavities 26, 28, to
produce the inner part A and the outer part B respectively. View
(a) shows a fill step, wherein the die cavities 26 and 28 are
individually filled with respective predetermined quantities of
metal powder. View (b) illustrates a compaction step. In view (b),
the inner top punch 16 slides within the die cavity 26 and the
outer top punch 18 slides within die cavity 28 under a first
compaction force F.sub.1, applied by the upper tool set 12. Once
the punches 16, 18 are within the cavities 26, 28, the lower inner
punch 30 and the lower outer punch 32 counter force F.sub.1 applied
by the upper portion 12, under second and third compaction forces
F.sub.2 and F.sub.3 respectively. Movement of the tipper portion 12
and the lower punches 30 and 32 compacts the individual quantities
of powdered metal into the discrete shapes of the separate articles
A and B. Compaction continues until the desired density of the
material for each part A, B is achieved The forces F.sub.2 and
F.sub.3 are each a portion of the maximum compaction force F.sub.c
of the press, and the relationships F.sub.1.ltoreq.F.sub.c;
F.sub.2+F.sub.3.ltoreq.F.sub.c; and F.sub.1=F.sub.2+F.sub.3 should
be satisfied. For the arrangement shown in FIGS. 2-5, typically
F.sub.2<F.sub.3, since the area of part A is smaller than the
area of part B. Once the compaction step is complete, the upper
portion 12 is raised as shown in view (c).
[0031] As shown in view (d), the lower die portions 20, 22 are
lowered and the outer bottom punch 32 raised in order to provide a
flush surface supporting the compacted parts A and B. The flush
surface enables the parts A, B to be more easily removed from the
tooling 10 using a pushing mechanism (not shown) so that the next
compaction stroke may commence. If capable, the press may cause the
tooling 10 to use a control scheme to raise both punches 30 and 32
to provide a flush surface along datum D. Therefore, it will be
appreciated that any means for removing the parts A and B from the
tooling 10 may be used, but preferably, an arrangement that
produces a flush surface should be achieved in order to facilitate
such removal.
[0032] A plan view of a pair of concentrically pressed gears A, B
is shown in FIG. 6. To form the gears shown in FIG. 6, the punches
16, 18, 30 and 32 would include profiles defining the gear teeth,
desired pitch etc.
[0033] Therefore, the tooling assembly 10 enables the production of
a pair of discrete, concentrically sized parts A, B using a single
compaction stroke and a single compaction machine, without the need
to chance dies or punches to accommodate differently sized parts.
The central punch 24 maintains separation between cavities 26, 28
in order to press the parts A, B at the same time, but into
discrete components. Moreover, each of the parts 40 and 42 may be
produced using a portion of the maximum compaction force of the
tooling 10 in order to utilize as much of the available compaction
force F.sub.c as possible.
[0034] In another embodiment shown in FIG. 7, two parts A' and B'
are simultaneously compacted in a side-by-side arrangement. The
tooling assembly 700 includes a moveable upper punch portion 702,
and a moveable lower punch portion 704. The upper portion 12
includes a first top punch 706 laterally spaced from a second top
punch 708. Similar to the tooling 10 shown in FIGS. 3-5, the
punches 706 and 708 move in tandem with upper portion 702, and
operate under a first force F.sub.1, which utilizes a portion of
but not exceeding, the available compaction force F.sub.c provided
by the press utilizing the tooling 700.
[0035] The lower portion 704 includes a die platen 710, a central
tool core 712, and first and second punch cores 714 and 715. The
cores 712, 714, 715, and platen 710, define a first annular die
cavity 716 and a second annular die cavity 718 for containing metal
powder (shaded portions). The tooling 700 operates in a similar
fashion to the tooling 10 to produce a first part A' and a second
part B' using a single stroke of the compaction press, and a
distribution of the available compaction force F.sub.c of the press
between the two lower punches 722, 720.
[0036] Therefore, multiple parts can be simultaneously compacted in
various arrangements, including concentric and side-by-side
arrangements. However, the concentric arrangement shown in FIGS.
2-5 is preferable in order to encourage a balance of compaction
forces and die stresses. The parts produced in the side-by-side
arrangement may also be of similar or the same size to balance
forces (e.g. as shown in FIG. 7). It will be appreciated that the
examples shown herein are for illustrative purposes only and that
any arrangement may be used as required by the particular
application.
[0037] It has been shown in preliminary testing that a concentric
arrangement producing an inner (smaller) gear A having an area of
9.4 sq in. and outer (larger) gear B having an area of 15.3 sq in.,
can be achieved using an 800 ton capacity press with the
above-described tooling assembly 10.
[0038] In general, the above test broadly applies to the compaction
of many grades of ferrous and non-ferrous powders. In particular, a
powder blend has been used consisting of commercially available
grades of iron powder, copper powder and carbon (graphite) powder.
The nominal elemental composition of the powder was 2% copper, and
0.8% carbon, the remainder being primarily iron with a small
concentration of unavoidable impurities. Typical lubricant
additions were also used. The compressibility characteristics of
the blend are represented by the curve of FIG. 1. In the above
example, it was desired to compress the gears to a density of 6.7
g/cc. Therefore, according to the curve of FIG. 1, the inner gear A
having 9.4 sq in. area required a compaction force of approximately
300 tons (e.g. F.sub.2), and the outer gear B having 15.3 sq in.
area required a compaction force of approximately 480 tons (e.g.
F.sub.3).
[0039] Accordingly, the combined required compaction force of
approximately 780 tons (e.g. F.sub.1) to simultaneously compact
both parts could be accommodated by an 800 ton (e.g. F.sub.c)
compacting press. The simultaneous compaction allows a doubling of
the output from the compaction press (increased throughput) while
utilizing a greater portion of the available force F.sub.c, thereby
favourably improving the economics of the compaction press.
[0040] Although the invention has been described with reference to
certain specific embodiments, various modifications thereof will be
apparent to those skilled in the art without departing from the
spirit and scope of the invention as outlined in the claims
appended hereto.
* * * * *