U.S. patent application number 11/193571 was filed with the patent office on 2006-07-27 for methods for shaping green bodies and articles made by such methods.
Invention is credited to Norbert Abels, Claus-H. Backes.
Application Number | 20060163774 11/193571 |
Document ID | / |
Family ID | 36695957 |
Filed Date | 2006-07-27 |
United States Patent
Application |
20060163774 |
Kind Code |
A1 |
Abels; Norbert ; et
al. |
July 27, 2006 |
Methods for shaping green bodies and articles made by such
methods
Abstract
A method of shaping a green body provides a shaped green body
comprised of a plurality of sinterable particles and an organic
binder. Such a method includes: (1) molding a mixture of sinterable
particles and organic binder into the shape of an initial green
body or intermediate, wherein the sinterable particles include at
least one of metal particles or ceramic particles; and (2) shaping
the green body intermediate with at least one of a stream of energy
or a stream of matter, wherein the shaping yields a green body
having a desired shape. The shaped green body can be sintered in
order to provide a hardened body having substantially the shape of
the shaped green body.
Inventors: |
Abels; Norbert; (Homburg,
DE) ; Backes; Claus-H.; (Saarbrucken, DE) |
Correspondence
Address: |
WORKMAN NYDEGGER;(F/K/A WORKMAN NYDEGGER & SEELEY)
60 EAST SOUTH TEMPLE
1000 EAGLE GATE TOWER
SALT LAKE CITY
UT
84111
US
|
Family ID: |
36695957 |
Appl. No.: |
11/193571 |
Filed: |
July 29, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11042025 |
Jan 25, 2005 |
|
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11193571 |
Jul 29, 2005 |
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Current U.S.
Class: |
264/293 ;
264/401; 264/414; 264/446; 428/688 |
Current CPC
Class: |
Y10T 428/24893 20150115;
A61C 13/0022 20130101; B28B 11/12 20130101; B28B 17/0036 20130101;
C04B 2235/612 20130101; C04B 35/634 20130101; A61C 7/14 20130101;
C04B 2235/658 20130101; C04B 2235/6022 20130101; B29C 2035/0838
20130101; C04B 2235/602 20130101; B29C 35/0805 20130101; C04B
35/638 20130101; A61C 7/12 20130101 |
Class at
Publication: |
264/293 ;
264/401; 264/414; 264/446; 428/688 |
International
Class: |
B28B 11/08 20060101
B28B011/08; B32B 19/00 20060101 B32B019/00; B29C 39/00 20060101
B29C039/00; B29C 35/04 20060101 B29C035/04 |
Claims
1. A method of manufacturing a shaped green body, comprising:
forming an initial green body by molding a mixture of sinterable
particles and organic binder into a desired shape of the initial
green body, wherein the sinterable particles include at least one
of metal particles or ceramic particles; and shaping the initial
green body by removing a portion of the sinterable particles from
the initial green body using at least one of a stream of energy or
a stream of matter to yield the shaped green body.
2. A method as in claim 1, wherein forming the initial green body
further comprises: introducing the sinterable particles into a
mold; and introducing the organic binder into the mold in an,
amount and distribution sufficient to hold the particles together
after being released from the mold as the initial green body,
wherein the initial green body is sufficiently a form-stable so as
to resist cracking or breaking during shaping.
3. A method as in claim 2, wherein the sinterable particles and
organic binder are injected into the mold substantially
simultaneously.
4. A method as in claim 3, further comprising: introducing the
sinterable particles into a mixer; introducing the organic binder
into the mixer; and mixing the particles and binder so as form a
mixture.
5. A method as in claim 3, wherein at least a portion of the
sinterable particles are at least partially coated with the organic
binder before being introduced into the mold.
6. A method as in claim 1, wherein the shaping is performed using a
laser beam.
7. A method as in claim 1, wherein the shaping is performed using a
stream of energy that comprises at least one of an electron beam,
an electrical discharge, or an ion beam.
8. A method as in claim 1, wherein the shaping is performed using a
stream of matter that comprises at least one of a water-jet, a
stream for sandblasting, a chemical-jet, or a fluid jet.
9. A method as in claim 8, wherein the water-jet further comprises
abrasive particles.
10. A method as in claim 1, further comprising: melting, on the
stream-cut surface, at least one of a portion of the metal
particles or a portion of the organic binder with a thermal
beam.
11. A shaped green body formed according to claim 1, the shaped
green body comprising: a plurality of sinterable particles; the
organic binder sufficiently holding the plurality of sinterable
particles together in order to be form-stable during the shaping;
and at least one stream-cut surface on the shaped green body.
12. A shaped green body as in claim 11, wherein the shaped green
body consists essentially of metal particles and has a laser-cut
surface thereon, the laser-cut surface being characterized as
including at least one of melted metal particles or melted organic
binder.
13. A shaped green body as in claim 11, wherein the shaped green
body has a volume about 10% to about 30% larger than a sintered
body obtained by sintering the shaped green body.
14. A method of manufacturing a shaped sintered article,
comprising: manufacturing a shaped green according to claim 1; and
sintering the shaped green body to yield the shaped sintered
article.
15. A method as in claim 14, wherein the sintering causes the
shaped sintered article to have a volume that is about 10% to about
30% less than the volume of the shaped green body.
16. A method as in claim 14, wherein the shaping is performed using
a laser before the sintering to provide a laser-cut surface on the
article that is substantially devoid of charring after
sintering.
17. A method as in claim 14, further comprising smoothing the
stream-cut surface during sintering.
18. A shaped sintered article formed according to claim 14,
comprising: a hardened sintered body, the sintered body including
at least one of a metal material or a ceramic material; and a
stream-cut surface on the sintered body, the stream-cut surface
being characterized by having a smoother topology after sintering
compared to before sintering.
19. A shaped hardened body as in claim 18, wherein the sintered
body consists essentially of sintered metal.
20. A shaped hardened body as in claim 18, wherein the sintered
body consists essentially of ceramic.
21. A shaped green body comprising: a plurality of sinterable
particles; an organic binder in an amount and distribution so as to
hold the plurality of sinterable particles together so that the
shaped green body is form-stable when shaped with at least one of a
stream of energy or a stream of matter; and at least one stream-cut
surface on the shaped green body formed by at least one of a stream
of energy or a stream of matter.
22. A shaped green body as in claim 21, wherein the plurality of
sinterable particles consists essentially of ceramic particles.
23. A shaped green body as in claim 21, wherein the plurality of
sinterable particles consists essentially of sinterable metal
particles.
24. A shaped green body as in claim 21, wherein the organic binder
includes at least one member selected from the group consisting of
polypropylene, polyethylene, acrylic polymers, polystyrene,
polyethylene-vinyl acetate, polyethylene vinyl alcohol,
polyethylene acetate, chlorinated polyethylene, polyisoprene,
polybutadiene, styrenebutadiene di-and tri-block polymers,
polychloroprenes, polyethylene-propylene copolymers,
chlorosulfonated polyethylenes, polyurethanes, styrene-isoprene
copolymers, styrene ethylbutylene copolymers, styrene-butadiene
rubber latex, polychloroprene latex, polymethylmethacrylate,
polyethylmethacrylate, and polydimethylsiloxanes.
25. A green body for use in preparing a stream-shaped green body,
the green body comprising: a plurality of sinterable particles
including at least one of a metal material or a ceramic material;
and an organic binder matrix comprised of an organic binder that
binds the sinterable particles together, wherein the organic binder
at least partially coats a portion of each sinterable particle
within the plurality of sinterable particles, the organic binder
being characterized as: being sufficiently adhesive to hold the
plurality of sinterable particles together; and forming a
form-stable green body that is capable of being shaped with at
least one of a stream of energy or a stream of matter without
cracking or breaking the green body.
26. A green body as in claim 25, wherein the sinterable particles
consist essentially of ceramic particles.
27. A green body as in claim 25, wherein the sinterable particles
consist essentially of sinterable metal particles
28. A shaped green body as in claim 25, wherein the organic binder
includes at least one member selected from the group consisting of
polypropylene, polyethylene, acrylic polymers, polystyrene,
polyethylene-vinyl acetate, polyethylene vinyl alcohol,
polyethylene acetate, chlorinated polyethylene, polyisoprene,
polybutadiene, styrenebutadiene di-and tri-block polymers,
polychloroprenes, polyethylene-propylene copolymers,
chlorosulfonated polyethylenes, polyurethanes, styrene-isoprene
copolymers, styrene ethylbutylene copolymers, styrene-butadiene
rubber latex, polychloroprene latex, polymethylmethacrylate,
polyethylmethacrylate, and polydimethylsiloxanes.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of copending U.S.
application Ser. No. 11/042,025, filed on Feb. 25, 2005, and
entitled "LASER SHAPING OF GREEN METAL BODY TO YIELD AN ORTHODONTIC
BRACKET", with Norbert Abels and Claus H. Backes as inventors. The
disclosure of the foregoing application is incorporated herein in
its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. The Field of the Invention
[0003] The present invention relates to processes for manufacturing
green bodies and sintered articles. More particularly, the present
invention relates to cutting and shaping a green body intermediate
with a stream of energy and/or matter prior to sintering so as to
fabricate a green body having substantially the shape of the
sintered article.:
[0004] 2. The Related Technology
[0005] Traditionally, when tools, machinery parts, or other metal
or ceramic components were designed and prepared for manufacturing,
an extensive process of designing, fabricating, and retooling
resulted in an extremely complicated and time consuming endeavor.
The sequential iterations required to produce a metal or ceramic
article with the proper dimensions and characteristics has become a
significant and costly issue, especially considering the complexity
of some of the more recently developed articles of manufacture. In
part, the long lead times and high costs associated with research
and development, when combined with the number of iterative
production steps needed for perfecting a metal or ceramic article,
has increased the time-to-market and associated costs. This has
resulted in delayed profits for many manufacturers, and
consequently, foregoing development of products that require costly
prototypes.
[0006] In response, research and development has been driven to
produce rapid prototyping and manufacturing technologies. As such,
the development of rapid prototyping techniques has provided the
ability to design and retool prototypes in a much shorter time
frame. In part, computer aided design and the ability to generate
accurate three-dimensional computer images of the prototypes,
sometimes by scanning a physical mockup, has enabled the iterative
process to manipulate virtual images rather than the physical
mockups.
[0007] Also, rapid prototyping has resulted in rapid tooling, which
is an indirect method for producing working models from molds
generated by the rapid prototyping process. As such, virtual
objects can be precisely designed by manipulating computer images,
which then are used for fabricating a physical mold before actually
preparing the physical object. The physical objects prepared by
these processes can then be tested to determine whether or not any
one object will function for the desired use.
[0008] Additionally, these prototyping techniques have resulted in
rapid manufacturing systems. These rapid manufacturing systems have
integrated the computer aided prototyping capabilities with
computer aided fabrication techniques such as stereolithography.
Other rapid manufacturing techniques include jet solidification,
three-dimensional welding, shape-deposition manufacturing, and
laser-based manufacturing systems. The prevalent laser-based
fabrication technologies include selective laser sintering, direct
metal laser sintering, and laser engineered net shaping.
[0009] Briefly, these laser-based fabrication technologies build a
prototype layer-by-layer by using lasers to sinter or cure metal or
ceramic powders one layer at a time until the article is finished.
Moreover, additional sintering and metal infiltration steps may be
required to produce a working piece. On the other hand, these
laser-based fabrication technologies can be inadequate for
preparing complex articles with protruding, overhanging, or other
features that would be difficult to prepare one layer at a time.
Additionally, these techniques are generally inadequate for
manufacturing a high volume of end use articles. Thus, there still
remains a need for improvements in rapid manufacturing processes to
produce highly accurate prototypes as well as end use articles.
[0010] Therefore, it would be advantageous to have a fabrication
technique for producing and shaping a metal or ceramic article
without cutting or milling a hardened metal or ceramic material.
Also, it would be beneficial to forego fabrication processes that
require a prototype or working article to be manufactured one layer
at a time.
BRIEF SUMMARY OF EMBODIMENTS OF THE INVENTION
[0011] Generally, an embodiment of a method for shaping a green
body can provide a green body having a desired shape that is
substantially the shape of a sintered article prepared therefrom.
Such a method includes molding a mixture of sinterable particles
and organic binder into the shape of an initial green body.
Additionally, the method includes further shaping the initial green
body with a stream of energy and/or matter in order to obtain a
shaped green body having a desired shape. To facilitate further
shaping, the initial green body intermediate is comprised of a
plurality of sinterable particles and an organic binder in an
amount and distribution sufficiently holding the plurality of
sinterable particles together so as to be form-stable while
removing sinterable particles during shaping. The shaped green body
is characterized as having at least one "stream-cut surface"
thereon.
[0012] In another embodiment, a method of manufacturing can provide
an article of manufacture comprised of a sintered body. Such a
method includes molding a mixture of sinterable particles and
organic binder into the shape of an initial green body
intermediate. Also, shaping the initial green body intermediate
with a stream of energy and/or matter results in a green body
having a desired shape, wherein the desired shape is substantially
the shape of the final sintered article. Additionally, sintering
the shaped green body can be performed to yield an article having
the desired shape.
[0013] Another embodiment includes an initial green body for use in
preparing a stream-shaped green body. The initial green body is
comprised of a plurality of sinterable particles, wherein the
sinterable particles including at least one of a metal material or
a ceramic material. Additionally, the green body is comprised of an
organic binder matrix, wherein the organic binder at least
partially coats each sinterable particle within the plurality of
sinterable particles. The organic binder is characterized as having
a thickness around a portion of the plurality of sinterable
particles that separates one sinterable particle from another
sinterable particle; being sufficiently adhesive to hold the
plurality of sinterable particles together; and forming a
form-stable body in which the plurality of sinterable particles are
initially bound together by the binder, wherein the form-stable
body is capable of being shaped with at least one of a stream of
energy or a stream of matter while remaining form-stable in areas
not subjected to the stream removal process.
[0014] These and other advantages and features of the present
invention will become more fully apparent from the following
description and appended claims, or may be learned by the practice
of the invention as set forth hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] To further clarify the above and other advantages and
features of the present invention, a more particular description of
the invention will be rendered by reference to specific embodiments
thereof which are illustrated in the appended drawings. It is
appreciated that these drawings depict only typical embodiments of
the invention and are therefore not to be considered limiting of
its scope. The invention will be described and explained with
additional specificity and detail through the use of the
accompanying drawings in which:
[0016] FIG. 1 is a side view illustrating an embodiment of a shaped
green body in the form of an orthodontic bracket;
[0017] FIG. 2 is a schematic diagram that illustrates different
embodiments of shaped green bodies that can be shaped from a single
initial green body by stream-removal of sinterable particles
therefrom;
[0018] FIGS. 3A and 3B are cross-sectional views of embodiments of
exemplary morphologies of a stream-cut surface;
[0019] FIG. 4 is a schematic diagram that illustrates an embodiment
of a system for preparing a shaped green body;
[0020] FIG. 5 is a schematic diagram that illustrates an embodiment
of a system for preparing a sintered body from a shaped green
body;
[0021] FIG. 6 is a schematic diagram that illustrates an embodiment
of a system for processing a particle and binder composition used
to form initial green bodies;
[0022] FIG. 7 is a schematic diagram that illustrates an embodiment
of a scanning and/or shaping system;
[0023] FIG. 8 is a schematic diagram that illustrates an embodiment
of a stream-cutting apparatus;
[0024] FIG. 9A is a schematic diagram that illustrates an
embodiment of a stream-cutting nozzle;
[0025] FIG. 9B is a schematic diagram that illustrates an
embodiment of a coaxial stream-cutting nozzle;
[0026] FIG. 9C is a schematic diagram that illustrates an
embodiment of a coaxial stream-cutting nozzle; and
[0027] FIG. 10 is a schematic diagram that illustrates an
embodiment of a three-dimensional stream-cutting system.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0028] Embodiments of the present invention include initial green
bodies comprised of metal or ceramic particles, shaped green bodies
prepared from the initial green bodies, sintered bodies prepared
from the shaped green bodies, and associated methods of making and
using the same. More particularly, embodiments of the present
invention include initial green bodies that are shaped with at
least one of a stream of energy and/or matter in order to have a
desired shape before being sintered into a final hardened article.
It should be understood that terminology employed herein is used
for the purpose of describing particular embodiments only and is
not intended to be limiting.
I. General Definitions
[0029] As used herein, the term "green" is meant to refer to the
state of an article of manufacture, wherein the article is
comprised of a plurality of sinterable particles such as metal or
ceramic particles that are held together with an organic binder. As
such, an initial green body can be shaped with a stream of energy
and/or matter in order to form a shaped green body.
[0030] As used herein, the terms "shape," "form," and the like are
meant to identify the three-dimensional structure or appearance of
an article of manufacture. As such, a green body in the shape of a
gear can be construed to indicate that the green body looks like a
gear, even though it may have compositions, dimensions, and
proportionalities that are different from an actual gear prepared
by sintering the gear-shaped green body. For example, a green body
shaped like a gear will have the appearance of a gear, but will be
about 10% to about 30% larger than the sintered gear. It may also
lack sufficient strength to function as intended. Such strength
typically develops as a result of sintering.
[0031] As used herein, the term "stream-cut" is meant to refer to
the process of preparing an object or article to have a desired
shape by cutting the object with a stream of energy, such as a
laser or electron beam, or a stream matter such as a water-jet to
stream of particles. By being stream-cut, the object or article has
been cut so as to alter the shape. A "stream-cut surface" refers to
a surface formed by removing sinterable particles by means of at
least one of a stream of energy or a stream of matter.
[0032] As used herein, the term "laser-cut" is meant to refer to
the process of shaping an object or article to have a desired shape
by cutting the object with a laser. By being laser-cut, the object
or article has been cut with a laser so as to alter the shape.
[0033] As used herein, the term "stream of energy" is meant to
refer to a beam or flow of energy that is propagated in a
substantially linear trajectory. As such, a stream of energy can
include a laser beam or other beam of electromagnetic radiation.
Additionally, a beam of atomic or subatomic level materials such as
plasma, ions, or electrons are also considered to be a stream of
energy. Examples of atomic or subatomic streams of energy include
an electron beam, electrical discharge, plasma beam, ion beam, and
the like.
[0034] As used herein, the term "stream of matter" is intended to
refer to a flow of matter in a substantially linear trajectory,
wherein the matter is larger than the atomic level and includes
microscopic- and macroscopic-sized particles. Examples of
macroscopic streams of matter include water-jet, fluid-jet,
chemical-jet, sandblasting, and the like.
[0035] Concentrations, amounts, particle sizes and other numerical
data may be presented in a range format. It is to be understood
that such a range format is used merely for convenience and brevity
and should be interpreted flexibly to include not only the
numerical values explicitly recited as the limits of the ranges,
but also to include all the individual numerical values or
sub-ranges encompassed within that range as if each numerical value
and sub-range is explicitly recited. For example, sinterable
particles can be present in various green body compositions within
a range of about 50% to about 98% by total weight. This recited
range should be interpreted to include not only the explicitly
recited limits of about 50% and about 98%, but also to include such
individual compositional percentages, such as 55, 62, 70, and 88,
as well as sub-ranges between these individual percentages. This
interpretation should apply regardless of the breadth of the range
or the characteristic being described, and should apply to ranges
having both upper and lower numerical values as well as open-ended
ranges reciting only one numerical value.
II. Green Body Compositions
[0036] In one embodiment, a metal-based composition useful for
preparing a green body can include a plurality of sinterable metal
particles. The metal particles can include, for example, aluminum,
nickel, titanium, copper, cobalt, stainless steel, and the like as
well as various alloys thereof. In a more specific example, the
metal particles can be comprised of a nickel-titanium alloy powder.
More particularly, it is preferable that the metal particles be
comprised of a metal that can be pulverized and/or powdered and
later sintered. For example, if corrosion-resistant stainless steel
gears are desired, a pre-alloyed fine-grained stainless steel
powder can be used.
[0037] In one embodiment, a ceramic-based composition useful for
preparing a green body or intermediate thereof can include a
plurality of sinterable ceramic particles. Examples of sinterable
ceramic particles, or materials within particles, include
hydroxylapatite, mullite, crystalline oxides, non-crystalline
oxides, carbides, nitrides, suicides, borides, phosphides,
sulfides, tellurides, selenides, aluminum oxide, silicon oxide,
titanium oxide, zirconium oxide, alumina-zirconia, silicon carbide,
titanium carbide, titanium boride, aluminum nitride, silicon
nitride, ferrites, iron sulfide, and the like. As such, any
sinterable ceramic particle can be used in preparing a sinterable
green body in accordance with the present invention.
[0038] Accordingly, various types of sinterable metal and/or
ceramic powders can be used in preparing an initial green body. In
some instances, the use of the articles prepared from sintering the
green body will require certain sinterable materials in order to
provide the desired or needed physical characteristics. As such,
there may be preferences or restrictions on the type of material to
be used for a specific type of finished article. In part, this is
because different articles may need to withstand forces that are
applied during use that impart varying levels of stress or strain.
It can be preferable in some cases for the sintered body to have a
high level of strength and toughness so as not to be easily damaged
during normal use. Alternatively, there may be circumstances that
would prefer bendable or high-deflection sintered articles. Some
articles may need to withstand very high or very low temperatures.
Thus, there are instances where metal particles may be preferred
over ceramic particles and vice versa.
[0039] Accordingly, the characteristics of the particles used in
accordance with the present invention can depend on the structure
of the shaped green body as well as the sintered article. In part,
the size and surface qualities of the sintered article can
determine the size of the particles, e.g., smaller articles or
articles having smooth surfaces may require smaller particles. For
example, the average diameter of the sinterable particles can
generally range from about 0.01 .mu.m to about 5 mm. A preferred
smaller particle range is about 0.1 .mu.m to about 50 .mu.m; a more
preferred range is about 0.5 .mu.m to about 25 .mu.m; and a most
preferred range is about 1 .mu.m to about 10 .mu.m. On the other
hand, a preferred larger particle range is about 50 .mu.m to about
5 mm; a more preferred range is about 100 .mu.m to about 1 mm; and
a most preferred range is about 0.25 mm to about 0.75 mm. Moreover,
it can be beneficial to use a combination of smaller particles
within the preferred smaller particle range(s) and within the
larger particle range(s).
[0040] Additionally, the concentration of sinterable particles
within the green body compositions can vary greatly depending on a
number of factors, such as particle size, type of metal or ceramic,
amount and type of organic binder, and the physical characteristics
of the shaped green body and sintered articles prepared therefrom.
For example, the sinterable particles may be present in a range of
about 25% to about 98% by weight of the green body composition,
preferably in a range of about 35% to about 95% by weight, more
preferably in a range of about 50% to about 90% by weight, and most
preferably in a range of about 60% to about 85% by weight of the
green body composition. On the other hand, when metal, ceramics,
carbides, or other strengthening fillers are included, the
sinterable particles can be present at lower concentrations.
[0041] In order to bind the sinterable particles together, the
metal or ceramic-based compositions include an organic binder.
Examples of organic binders that can be used to bind sinterable
particles together in accordance with the present invention include
various polymers, polyolefins, silicones, acrylics, latexes, waxes,
oils, greases, plasticizers, lignosulfonates, polysaccharides,
celluloses and derivatives thereof, starches and derivatives
thereof, other natural polymers (e.g., proteins), natural and
synthetic rubbers, and the like. More specific examples of
polymeric binders can include polypropylenes, polyethylenes,
acrylic polymers, polystyrenes, polyethylenevinyl acetate,
polyethylene vinyl alcohol, polyethylene acetate, chlorinated
polyethylenes, polyisoprenes, polybutadienes, styrene-butadiene
di-and tri-block polymers, polychloroprenes,
polyethylene-propylenes, chlorosulfonated polyethylenes,
polyurethanes, styrene isoprene polymers, styrene ethylbutylene
polymers, styrene butadiene rubber latex, polychloroprene latex,
polymethylmethacrylate, polyethylmethacrylate,
polydimethylsiloxanes, and the like. It should be recognized that
other organic binders known in the art can be used in order to bind
the sinterable particles into green body compositions for
processing in accordance with the present invention.
[0042] Accordingly, the compositions useful in preparing a green
body include a binder in an amount and disposition within the
plurality of sinterable particles sufficient to hold the sinterable
particles together. Additionally, an initial molded green body or
intermediate comprised of metal and/or ceramic particles and a
binder can be sufficiently pressed or compacted so as to be
form-stable and capable of standing freely and being
self-supporting. More particularly, the amount and disposition of
binder is sufficient for the green body intermediate to be shaped
with a stream of matter and/or a stream of energy, such as with a
laser, water-jet, or electron beam. Thus, the organic binder can
hold the sinterable particles together in the desired shape, and
continue to hold the particles together during the shaping
process.
[0043] Additionally, the concentration of organic binder mixed with
the sinterable particles within the green body compositions can
vary greatly depending on the aforementioned factors. For example,
the organic binder may be present at a concentration range of about
2% to about 75% by weight of the green body composition, preferably
in a range of about 5% to about 65% by weight, more preferably in a
range of about 10% to about 50% by weight, and most preferably in a
range of about 15% to about 40% by weight of the green body
composition. As previously described, it should be recognized that
any sinterable particle to binder ratio can be used as long as a
green body or intermediate is sufficiently held together to be
handled and shaped with a stream of energy or stream of matter.
[0044] In one embodiment, the organic binder can be intermingled or
combined with the sinterable particles in an amount and disposition
sufficient to form a flowable particle-binder composition that is
capable of being injected into a mold. This flowable
particle-binder composition can be premixed so as to disperse the
binder around and/or between the sinterable particles. This can
include adhering the binder onto the particles as well as providing
a medium for suspending the particles.
[0045] Examples of green bodies and the various processes for
manufacturing green bodies in accordance with the present invention
as well as the types of articles that can be prepared from shaped
green bodies will be discussed in more detail below.
III. Green Bodies
[0046] FIG. 1 illustrates an embodiment of a green body 12 in the
shape of an orthodontic bracket 10. The green body 12 is comprised
of sinterable metal and/or ceramic particles held together with an
organic binder, wherein the shape of the orthodontic bracket 10 is
defined by an external surface 16. Accordingly, the green body 12
includes at least one tie wing 18 that is characterized as having a
lobe 28 that is adjacent to a lobe recess 30. Also, the green body
12 has an archwire slot 20 that is open to the upper (or labial)
side. As depicted, the green body 12 includes a bonding surface 22
having a topology that includes a plurality of protrusions and
undercuts.
[0047] In this embodiment, the exterior surface 16 includes at
least one stream-cut (e.g., laser-cut) surface 32a having a
topology characterized by a plurality of undercuts 24 formed by
removing sinterable particles and binder from the green body 12. In
general, features formed from such a feature-forming cut can be
either macroscopically visible or microscopically visible. As used
herein, the term "macroscopic" can include features that are visual
with the naked eye without any magnification. Alternatively, the
term "microscopic" as used herein refers to the need for
magnification to be used in order to visualize the features.
[0048] In one embodiment, the green body 12 can have another
stream-cut surface 32b on the external surface 16. This stream-cut
surface 32b is cut into the green body 12 so that a significant
amount of green material is removed in order to form the shape of
the orthodontic bracket 10. Accordingly, the green body 12 can
initially have a rectangular cross-sectional area as shown with the
dashed-lines 34 (e.g., initial green body). More particularly, a
first portion 36 of the green body 12 can be cut away from a second
portion 38 of the green body, which thereby forms the laser-cut
surface 32b at the cut.
[0049] Additionally, a minor stream-cut surface 32c can be made to
remove only a minimal amount of green body material or to refine a
previous cut. Thus, a feature-forming stream-cut surface 32a,
significant stream-cut surface 32b, and/or a minor stream-cut
surface 32c can be part of the external surface 16 of a green body
shaped by being stream-cut according to the invention.
[0050] FIG. 2 illustrates additional embodiments of articles that
can be formed from a green body 50. A single initial green body 50
can be stream-cut into a shaped green body having the shape of a
gear 52, roller 54, spindle 56, or any other desired article. This
can be done by a stream-cutting process that essentially forms the
desired shape from the initial green body 50 by cutting away the
excess material. Thus, a substantially cylindrical-shaped initial
green body 50 can be cut into a myriad of green body shapes.
[0051] Accordingly, the initial green body 50 can be shaped by a
stream-cutting process so as to form a stream-cut surface 58. As
such, the stream-cut surface 58 can include the entire external
surface so that the shape of the gear 52, which includes gear teeth
60 and an aperture 62, can be formed by cutting the green material
with a stream of energy or stream of matter. Thus, the teeth 60 and
aperture 62 can each be defined by a stream-cut surface 58.
[0052] Similarly, the stream-cut surface 58 can be cut into the
initial green body 50 so as to form the shape of a roller 54. As
shown, the roller 54 includes an annular outer stream-cut surface
58 that is substantially smooth. Also, an aperture 64 defined by a
smooth stream-cut surface 58 can be bored through the initial green
body 50.
[0053] Alternatively, a spindle 56 having a stream-cut surface 58
can be stream-cut from the initial green body 50.
[0054] While various embodiments of shaped green bodies have been
depicted and described, the present invention is not limited to
such shapes. Accordingly, a shaped green body can be any shape that
can be cut and sintered as described herein. That is, any shape or
article prepared from sintering can be prepared as a shaped green
body in accordance with the present invention.
[0055] FIGS. 3A and 3B illustrate embodiments of a stream-cut
surface 70. The stream-cut surface 70 of FIG. 3A includes a
topology 72 that defines features on the exterior surface of a
green body 74. In this embodiment, the topology 72 includes a
plurality of macroscopic irregular elevations, which can be in the
form of protrusions 76, recesses 78, and/or undercuts 80, and
result in a substantially uneven or rough surface 81. The larger
irregular elevations can also include microscopic or smaller
irregular elevations, which can be micro-protrusions 82,
micro-recesses 84, and micro-undercuts 86.
[0056] Alternatively, as shown in FIG. 3B, the stream-cut surface
70 can be cut with a stream of energy or stream of matter in a
manner than results in a topology 72 that defines a substantially
smooth surface 88. Thus, the green body 74 can be configured to
have a topology or surface ranging from substantially uneven (FIG.
3A) through substantially smooth (FIG. 3B).
[0057] The topology 72 characterized by the uneven or rough surface
81 or smooth surface 88 can be comprised of a binder holding a
plurality of sinterable particles together to form the green body
74. In one embodiment, a portion of metal particles on the topology
72 are melted together to form a melted surface layer. In another
embodiment, the sinterable particles on the topology 72 are adhered
together with melted binder.
[0058] In yet another embodiment, a portion of the topology 72
includes a charred or blackened layer, especially when formed by a
stream of energy such as a laser. The charred or blackened layer
can be characterized by surface features that result from the
vaporizing, melting, and/or burning of the binder that accompany
the process of cutting the green body 74 with the stream of energy
that heats the surface to a hot temperature.
IV. Manufacturing Green Bodies and Sintered Articles
[0059] FIGS. 4-10 illustrate various schematic diagrams of
embodiments of processing systems and equipment that can be used
during the formation of green bodies and sintered articles prepared
therefrom. It should be recognized that these are only examples of
schematic representations of processing systems and equipment, and
various modifications can be made thereto in order to prepare the
inventive green bodies and sintered articles. Accordingly, the
various systems and equipment currently known or later developed
for preparing most types of sinterable green bodies and sintered
articles are considered to be included within the scope of this
disclosure. Also, the schematic representations should not be
construed in any limiting manner to the arrangement, shape, size,
orientation, or presence of any of the features described in
connection therewith. With that said, a more detailed description
of examples of some of the systems and equipment that can prepare
the green bodies and sintered articles in accordance with the
present invention is now provided.
[0060] FIG. 4 is a schematic diagram illustrating a general
embodiment of a shaping system 100 for preparing a shaped green
body from an initial green body. Initially, the sinterable
particles are obtained from a particle supply 102, and the organic
binder is obtained from an organic binder supply 104. The
sinterable particles and organic binder are then introduced into a
mixing apparatus 106 to prepare a mixture. The mixture is then
introduced into a molding apparatus 108, which forms an initial
green body or intermediate 110 of a desired initial shape. The
initial green body 110 can be characterized as having an exterior
surface that is substantially in the shape of the mold cavity
defined by the molding apparatus 108.
[0061] The initial green body or intermediate 110 having the shape
of the mold cavity is then supplied into a stream-cutting apparatus
112. The stream-cutting apparatus 112 may at some point be in
communication with a three-dimensional ("3-D") virtual image
generator 114, which can create a 3-D virtual image of the desired
shape of the shaped green body 116. Alternatively, the 3-D virtual
image can be created within the 3-D virtual image generator 114 and
then stored on a data storage device, which is then provided to the
stream-cutting apparatus 112.
[0062] In any event, the stream-cutting apparatus 112 is able to
stream-cut the initial green body 110 into a shaped green body 116.
Preferably, the stream-cutting apparatus 112 uses computer-guided
technology to direct a stream of energy and/or a stream of matter
so that a precise shape is formed into the green body material. As
depicted, the shaped green body 116 can be prepared into the shape
of a gear, or any other desired stream-cut shape.
[0063] FIG. 5 is a schematic diagram that illustrates a general
embodiment of a sintering system 120 for sintering a shaped green
body into a sintered body. A shaped green body 124 may be obtained
by employing a shaping system 100, as depicted in FIG. 4.
Alternatively, various other embodiments of shaping systems in
accordance with the present invention can provide the shaped green
body 124. In any event, the shaped green body 124 is introduced
into a sintering apparatus 126. The sintering apparatus 126 then
sinters the sinterable particles together and removes the binder
from the interstitial spaces. In some instances it can be
preferable for the binder to be removed by being melted away or
vaporized such as through a de-binding process.
[0064] After sintering the green body material, a sintered body 128
is removed from the sintering apparatus 126. A comparison of the
sintered body 128 with the shaped green body 124 shows that
sintering has reduced the volume of the article by about 10% to
about 30% according to a preferred embodiment. Optionally, the
sintered body 128 may then be processed through a finishing
apparatus 130 that can further refine the sintered body into a
finished article 132. Many processes can be used to finish a
sintered article, which depend on the nature of the finish.
Examples of such finishing processes include grinding, sanding,
shot peening, powder coating, painting, and the like.
V. Manufacturing Particle-Binder Compositions
[0065] FIG. 6 is a schematic diagram illustrating embodiments of a
particle-binder processing system 200 in accordance with the
present invention. The various embodiments of particle-binder
processing systems 200 described below can be represented by the
general mixing apparatus 106 described in FIG. 4. More
particularly, the particle-binder processing system 200 can be used
to mix the particles and binder together in order to form a mixture
that is capable of being introduced into a mold for preparing a
green body in accordance with the present invention.
[0066] In one embodiment, sinterable particles can be kept in a
particle storage container 202 such as a container, storage bin,
hopper, mixer, and the like. A suspension solution for suspending
the sinterable particles can be kept in a suspension container 208.
Additionally, binder A can be similarly kept within a binder
storage container 204, and a binder solvent for dissolving or
suspending the binder can be kept in a solvent container 210.
[0067] Accordingly, particles from container 202 can be combined
with the suspension solution from container 208. The suspension
solution is compatible with the particles so as to form a particle
suspension or other fluid composition that is capable of being
processed for preparing the particle-binder composition. The
suspension solution can be comprised of an organic solvent or
water, and can include cellulose ethers to impart non-Newtonian
shear characteristics or thickening to hold the particles in
suspension. As such, the particles and suspension solution can be
combined in the particle container 202, suspension container 208,
or a mixer 206.
[0068] Similarly, binder A from container 204 can be combined with
the solvent from container 210, wherein the combining can be
performed within the binder A container 204, solvent container 210,
or the mixer 206. As such, the solvent can be mixed with binder A
to either dissolve the binder A or form a flowable suspension
therewith. The binder A and solvent mixture can be useful in
preparing the particle-binder composition with the particles and
with or without the suspension solution.
[0069] In one embodiment, the suspended particles are supplied into
mixer 206. Additionally, binder A suspended or dissolved in the
solvent can also be supplied into mixer 206. Mixer 206 can be a
high sheer mixer or a low speed mixer that is configured to form a
composition comprised of particles and binder A. Additionally, the
suspension solution and/or solvent can enhance mixing by being
either miscible or immiscible. In either case, a particle-binder
composition can be prepared in the mixer 206. Alternatively, the
particles without the suspension solution are mixed in the mixer
206 with binder A with or without the solvent.
[0070] In one embodiment, the suspended particles can be combined
with the binder A in mixer 206 without the binder solvent. As such,
binder A can be heated by heating unit 220 in a manner that
liquefies binder A. By liquefying binder A with the heating unit
220, the binder can be easily manipulated and injected into mixer
206. As such, the heating unit 202 can be configured to supply heat
to the binder A container 204, or alternatively, binder A can be
supplied into the heating unit 220. In any event, binder A is
heated so as to be flowable, wherein a fluid binder can be easily
injected into mixer 206. In the instance binder A is liquefied by
heat without the aid of solvent, the particle suspension can enable
increased mixing between the particles and binder A. Alternatively,
the particles without the suspension solution are mixed with the
heated binder in the mixer 206.
[0071] In one embodiment, dry particles from container 202 and
binder A from container 204 can be supplied directly into mixer 206
without any suspension solution, solvent, or heat. In this case,
mixer 206 can be a dry granulizing mixer, which can granulize and
combine the particles and binder A into a homogenous granulized
composition. Accordingly, such a granulized composition can be
further processed in accordance with the present invention.
[0072] In one embodiment, particles from container 202 with or
without the suspension solution from container 208 can be supplied
into a conditioning vessel 212. The conditioning vessel 212 can
contain a conditioner (e.g., conditioning composition) for
conditioning the particles in a manner to enhance the mixing with
the binder. Such a conditioner can be any of various waxes,
polyolefins, dispersants, rheology-modifying agents, surfactants,
and like materials so as to enhance the ability of the particles to
be combined, coated, and/or interspersed within binder A. In one
embodiment, the conditioner can be an organic binder. After mixing,
the conditioner can at least partially coat the particles in a
manner that increases the interaction between the particles and
binder A. Thus, particles that have been conditioned in the
conditioner 212 can then be supplied into mixer 206 along with
binder A.
[0073] On the other hand, after the particles are supplied into the
conditioning vessel 212, it may be beneficial to introduce the
conditioned particles into a dryer/cooler unit 214. As such, the
conditioner may comprise a volatile solvent so that when the dryer
212 is heated, the solvent is vaporized leaving dry conditioned
particles. On the other hand, the conditioning vessel 212 may be
heated so that the cooler 214 cools the conditioned particles
before being further processed. Either the dried or cooled
conditioned particles can be further processed by being mixed in
mixer 206.
[0074] In any event, independent of how the particles or binder A
have been processed, mixer 206 can be configured to provide a
substantially homogeneous composition comprised of the particles
and binder A.
[0075] In one embodiment, mixer 206 can be configured to be an
extruder. Accordingly, such an extruder can be a single screw
extruder, twin screw extruder, or a piston-type extruder. This can
be beneficial in order to produce an extrudate comprised of
particles and binder A. The extruder can include heating elements
to increase the temperature of the particle-binder composition when
thermoplastic binders are used. The heating elements can vaporize
any solvents, and also increase the composition to a temperature
sufficient for being extruded
[0076] In one embodiment, independent of how the particle-binder
composition is prepared, such a composition can be supplied into
the dryer/cooler 214. The dryer 214 is configured to remove any
solvent or other volatile substances from the mixture. Accordingly,
the dried composition can have a moisture content less than about
20% by wet weight, more preferably less than about 10% by wet
weight, and most preferably less than about 5% by wet weight.
Alternatively, the cooler 214 can decrease the temperature of a
heated mixture (e.g., extrudate) such that it can be further
processed. The cooler 214 can decrease the temperature to about
35.degree. C., or more preferably about 30.degree. C., and most
preferably less than about 25.degree. C.
[0077] In one embodiment, the composition obtained in mixer 206 may
forego any drying/cooling, and can be directly supplied into
pelletizer 216; especially when in the form of an extrudate.
Alternatively, the dried or cooled composition obtained from the
dryer/cooler 214 can be supplied into pelletizer 216. In any event,
the particle-binder composition can be pelletized so as to form
small pellets having various sizes or shapes. Such shapes can be
relatively spherical, uneven, and/or jagged.
[0078] Pelletizer 216 can be configured for cutting the dried or
cooled particle-binder composition into pellets or beads having a
variety of sizes. For example, pelletizer 216 can form pellets
having an average diameter from about 0.2 mm to about 2 cm, more
preferably in range from about 0.3 mm to about 1 cm, and most
preferably in a range from about 0.5 mm to about 0.8 cm. However,
any pellet size can be obtained because the size of the shaped
green body and its surface characteristics can be determinate of
the pellet size.
[0079] In another embodiment, it could be preferable for the
particle-binder composition to be removed from the mixer 206 in a
form or a consistency useful for further Processing 218 into a
green body intermediate in accordance with the present
invention.
[0080] In one embodiment, additional binder B can be kept in a
binder B storage container 222, and can be utilized in order to
form a particle-binder system having at least two-types of binders.
As such, it can be beneficial to form a particle-binder A
composition as described herein, and then further processes such a
composition with additional binder B. Binder B obtained from
container 222 can be processed similar to binder A from container
204 by being dissolved or suspended in a solvent from container
210, or by being liquefied by heating unit 220. Accordingly, binder
B can be supplied into mixer 206 with the particle-binder A
composition, which can form a dual-binder composition.
[0081] Alternatively, after particle-binder A pellets have been
prepared in pelletizer 216, such pellets can be supplied into mixer
206 along with binder B. The pellets obtained from pelletizer 216
can be substantially coated with binder B, or become suspended
within binder B. Also, the particles combined with binder A and
binder B can then undergo further processing as described herein
after being mixed in mixer 206.
[0082] In another embodiment, processing the particles and binders
so as to form a particle-binder composition can be performed in a
sprayer/liquid-jet apparatus 224. As such, the particles from
container 202 can be supplied into the sprayer/liquid-jet apparatus
224. Optionally, such particles can be supplied by a conveyer or
other means of holding the particles so that they can be sprayed
with a liquefied binder. This can include a vibrating conveyor or
other type of holder such that the particles can be sprayed easily
on all sides or surfaces.
[0083] In one embodiment, the sprayer/liquid-jet apparatus 224 can
have a column-like spray tower configured with nozzles to spray the
binder. In this embodiment, the particles can be supplied into the
sprayer/liquid jet apparatus 224 by being dropped from the top of
the spray tower so as freefall past the nozzles spraying the binder
so as to at least partially coat the particles. Additionally, any
of the spray processes can be preformed with particles that have
been suspended or conditioned, or previously coated with a
binder.
[0084] Independent of the particle-binder composition formed within
the sprayer/liquid-jet apparatus 224, such a composition can be
supplied into a dryer/cooler apparatus 226 so as to dry and remove
any access volatile solvent, or to cool the particle-binder
composition. As such, the particle-binder composition can be dried
or cooled with apparatus 226 so as to be prepared for further
processing 228 in accordance with the present invention.
[0085] While embodiments of equipment, systems, and methods for
preparing a particle-binder composition have been described in
connection with FIG. 6, various other equipment, systems, and
methods can be used so as to form a particle-binder composition in
order to prepare an initial green body or intermediate. As such,
the processes of preparing an initial green body will be discussed
in further detail below.
VI. Molding Green Bodies
[0086] Referring now back to FIG. 4 and more particularly to the
molding apparatus 108, embodiments of systems and processes for
molding green bodies are described in greater detail. As such, the
molding apparatus 108 can receive any of the particle-binder
compositions prepared in accordance with the present invention
and/or described in connection with FIG. 6.
[0087] In any event, the particle-binder composition can be
supplied into the molding apparatus 108, which can be operated by
any of the well-known schemes for providing a molded article. As
such, the molding apparatus 108 can be operated at high
temperatures and/or at high pressures so as to form a molded body.
It can be beneficial to operate the molding apparatus in a manner
that generates a high pressure so that the particles can be tightly
pressed together. In this manner, any voids, air pockets, or other
anomalies within the binder the particle composition can be pressed
out and removed so that a dense form-stable molded article can be
prepared.
[0088] In one embodiment, the molding apparatus 108 can be
configured to have movable mold bodies that can compress the
particle-binder composition during molding. In this manner, a first
volume of the particle-binder composition can be supplied into the
molding apparatus 108 until it is substantially full, and then by a
compression molding technique, the molding apparatus can decrease
the volume of the particle-binder composition. By compressing the
composition, a more dense molded green body intermediate can be
obtained. Such compression can also be achieved by increasing the
pressure within the mold by either using some type of extruder
apparatus such as a piston extruder or by decreasing the volume of
the mold cavity within the molding apparatus 108.
[0089] In one embodiment, a method of molding a green body
intermediate can include injecting a particle-binder composition
into a mold under high pressure and/or temperature such as in
injection molding. Alternatively, the binder and sinterable
particles can be injected into a mold as separate feed streams that
are delivered at different times or simultaneously. When the
particles and binder are injected as separate feeds, it may be
advantageous for the binder to easily coat the particles by having
a high work of adhesion with respect to the particles, or to be
heated and mixed with the particles in the mold.
[0090] Additionally, the molding apparatus 108 can be configured to
operate by injection molding, casting molding, compression molding,
thermal molding, or any other molding technique.
[0091] In one embodiment, the green body intermediate can be formed
by increasing the temperature and/or pressure so that the
sinterable particles and binder are pressed together into the shape
of the mold cavity. Accordingly, the mold can increase the
temperature of the particles and binder from about 80.degree. C. to
about 400.degree. C., and more preferably from about 100.degree. C.
to about 380.degree. C., and most preferably about 120.degree. C.
to about 340.degree. C. Also, the particles and binder can be
pressed together at a pressure range of about 2 MPa to about 200
MPa, more preferably about 10 MPa to about 200 MPa, and most
preferably about 100 MPa to about 200 MPa.
[0092] The shape of the mold cavity within the molding apparatus
108 can be a general shape such as a cube, cylinder, sphere and the
like. Alternatively, the mold cavity can have a complex shape that
is similar to the shape of the final article prepared from the
molded green body intermediate.
[0093] Moreover, many variations can be made in the molding process
performed within the molding apparatus 108 so as to obtain a molded
article that is a green body intermediate.
VII. Generating Virtual Images
[0094] FIG. 7 is a schematic diagram that illustrates a scanning
system 230 (e.g., scanning and shaping system 230) in accordance
with the present invention. Such a scanning system 230 can be used
as at least part of the three-dimensional ("3-D") virtual image
generator 114 of FIG. 4. Accordingly, the scanning system 230
includes a computer system 232 in order to control the movement of
the various scanning components by providing control data to the
scanning controller 236. Also, the computer system 232 can control
any data acquisition, and direct any image data generated during
scanning to be saved on a data storage device 243. Data storage
devices 234 is well known in the art, and can include, but is not
limited to, floppy drives, hard disk drives, magnetic disk drives,
optical disc drives, read access memory ("RAM"), read-only memory
("ROM"), and the like. The scanning system can operate similarly to
any of the various well-known and later developed scanning
protocols.
[0095] In any event, the scanning controller 236 is in
communication with the computer system 232. This allows the
computer system 232 to be programmed by a user in order to
manipulate and control the performance of the scanning controller
236. After a scanning protocol is input into the scanning
controller 236, the scanning controller 236 controls an emitter
238, which is configured to emit a scanning beam 240a towards the
surface 242 of the body being scanned 244. A scanning beam 240a
directed towards the surface 242 of the body 244a can enable the
acquisition of 3-D image data. Such data acquired by the scanning
controller 236 can be stored on the memory storage device 234 as
raw data or data that has been manipulated to generate a virtual
3-D image of the body 244a.
[0096] Additionally, in order to facilitate the scanning of the
body 244a the scanning system 230 can include a turret 246 that can
rotate the body 244a as well as a mechanical feature 248 that can
enable lateral movement in the x, y, and z axes as well as rotate
around the x, y, and z axes. As such, a 3-D virtual image can be
obtained and stored within the memory storage device 234 so as to
be usable in various computer-assisted drawing programs ("CAD"). By
acquiring a 3-D virtual image of the body 244a, a user can
manipulate such a virtual image in order to obtain an exact or
precise 3-D virtual image of the desired shape of the green body
and sintered article.
[0097] In any event, a mockup of the desired finished article can
be placed within the scanning system 230 so that destructive or
non-destructive scanning can be used to create a virtual image.
Such destructive and non-destructive scanning technologies as well
as the associated equipment and software that are used to generate
three-dimensional virtual images are well known. Additionally, it
can also be possible to create a 3-D image using a CAD program so
that the shape of the green body is created entirely from a virtual
image without a mockup. Also, CAD programs can be used to take any
virtual image and alter the shape and size in order to provide the
desired shape of the green body.
VIII. Stream-Cutting Green Bodies
[0098] Referring again to FIG. 4, more particular details for the
embodiments of the stream-cutting apparatus 112 are described in
accordance with the present invention. The stream-cutting apparatus
112 can be configured to have or use a variety of stream-cutting
techniques. Such stream-cutting techniques can utilize streams of
energy and/or streams of matter. The streams of energy include
photons, electromagnetic radiation, atomic, and sub-atomic
materials, as described above. On the other hand, the streams of
matter are considered to include materials larger than atomic scale
particles, and can be microscopic or macroscopic in size. In any
event, the stream-cutting apparatus 112 is designed to direct a
stream of energy or a stream of matter at the initial green body
110 prepared in the molding apparatus 108, as described above in
connection with FIG. 4.
[0099] Referring again to FIG. 7, the schematic diagram also
depicts an embodiment of a shaping system 230 (e.g., scanning and
shaping system). The shaping system 230 can be employed within the
stream-cutting apparatus 112 of FIG. 4. The shaping system 230 can
optionally be combined with the scanning system 230 so as to be a
scanning and shaping system 230, as described in more detail below.
In any event, the shaping system 230 can acquire the 3-D virtual
image previously generated from the computer system 232 or the data
storage device 234.
[0100] The shaping system 230 can include a matter controller 250
and/or an energy controller 252 in communication with the computer
system 232. The matter controller 250 can enable the emitter 238b
to emit a stream of matter 240b to be directed at a surface 242b of
a green body 244b that is being shaped. The matter controller 250
can control the emitter 238 so that a stream of matter 240b, such
as chemicals, water, sand or other particulates, can be directed at
the green body 244b. The stream of matter 240b can shape the green
body 244b in accordance with the virtual image stored in the data
storage device 234 of the computer system 232.
[0101] In another embodiment, the energy controller 252 can control
the emitter 238c to emit a stream of energy 240c, such as a laser,
electron beam, ion beam, or the like, towards the green body 244b
to obtain a shape in accordance with the virtual image.
[0102] In view of the foregoing general description of a shaping
system in accordance with the present invention, the various types
of streams of energy and streams of matter that can be used therein
will now be described in more detail. As such, the following
embodiments of stream-cutting apparatuses can be employed within
the stream-cutting apparatus 112 of FIG. 4 as well as in the
shaping system 230 of FIG. 7.
[0103] In one embodiment, the stream of energy can cut and shape
the green body intermediate by generating heat at the site where
the stream intersects the green body material. As such, energy can
be used to generate heat in order to have a thermal interaction
with the binder and the sinterable particles. The thermal
interaction can elevate the local temperature to a point which can
cut, de-bind, melt, and/or vaporize portions of the binder-particle
composition from the rest of the bulk green body material.
[0104] Accordingly, one embodiment of the stream-cutting apparatus
can operate and shape the green body intermediate by thermal
interactions. As such, any of the thermal processes described
herein can be used for thermal-cutting. For example, such thermal
interactions can arise from laser beam treatment, laser beam
machining, electron beam machining, electrical discharge machining,
ion beam machining, and plasma beam machining. Thus, a stream-cut
surface can be a laser-cut surface, electron beam-cut surface,
electron discharge-cut surface, ion beam-cut surface, or a plasma
beam-cut surface.
[0105] In one embodiment, since the green body compositional
concentrations are known to be comprised of a substantial amount of
binding material, the thermal cutting process can require less
energy in comparison to similar techniques used for sintered or
otherwise hardened metal or ceramic articles. As such, by knowing
the thermal properties of the binder, precise energy requirements
can be calculated so that the thermal beam provides the appropriate
or minimum energy for melting and/or vaporizing the binder without
significantly melting or point-sintering the sinterable particles.
Alternatively, the energy can be increased so as to melt and/or
point sinter the sinterable particles.
[0106] For example, laser beams are a common form of a stream of
energy that can be used in the stream-cutting apparatus 112.
Typical laser-cutting machines can accurately produce complex
exterior contours in the green body because a laser beam is usually
between about 0.02 mm to about 0.2 mm in diameter at the cutting
surface and can have a power that ranges up to about 2,000 watts;
however, benefits of the current invention include the use of lower
powered lasers. Additionally, there are instances where a laser is
preferred over all other stream-cutting techniques because of the
nature of the resulting article as well as the characteristics of
the green body.
[0107] Accordingly, a laser can cut the green bodies, wherein the
power of the laser or the heat generated can depend upon the
composition of the material to be cut. The ability to vary the
laser power arises due to the use of different binders and/or
sinterable particles. The laser power is defined as the rate of
which energy is delivered by the beam and is usually measured in
units as joules/second or watts.
[0108] For example, lasers typically used in laser surgery have a
power on the order of about 10 watts, and such a low wattage can be
used to melt some binders to shape the green body. On the other
hand, lasers typically used in cutting hardened steel, such as YAG
or eximer lasers, can have a power of about 2,000 watts.
Accordingly, green bodies with softer binders can be shaped with
lasers operating below about 500 watts, more preferably below about
400 watts, and most preferably below about 200 watts.
Alternatively, harder binders or additionally melting and/or
vaporizing the metal or ceramic particles can use lasers operating
above about 500 watts, more preferably above about 750 watts, and
most preferably above about 1,000 watts.
[0109] In one embodiment, electrical discharge machining is used to
shape a green metal body. As such, electrical discharge machining
can is capable of cutting all types of conductive materials such as
exotic metal including such as titanium, hastaloy, kovar, inconel,
hard tool steels, carbides, and the like. In electrical discharge,
the main interaction between the stream of energy and the green
body is thermal, where heat is generated by producing electrical
discharges. This can lead to the green body material being removed
by melting and evaporation. Some examples of electrical discharge
machining include wire electron discharge machining, CNC-controlled
electrical discharge machining, sinker electrical discharge
machining, small hole discharge machining, and the like.
[0110] In another embodiment, the stream-cutting apparatus 112 can
use a charged particle beam, wherein charged particle beams are
exemplified by electron beams and ion beams. A charged particle
beam is a group of electrically-charged particles that have
approximately the same kinetic energy and move in approximately the
same direction. Usually, the kinetic energies are much higher than
the thermal energies of similar particles at ordinary temperatures.
The high kinetic energy and the directionality of these charged
beams can be useful for cutting and shaping of the green bodies, as
described herein. Additionally, there are some instances where
electron beams or ion beams are preferred over other cutting
techniques.
[0111] In one embodiment, the stream-cutting apparatus 112 can use
a stream of chemical matter in order to shape the green body.
Chemical-jet milling, for example, provides selective and
controlled material removal by jet and chemical action. As such,
the process is similar to waterjet cutting, which is described in
more detail below. In any event, chemical-jet milling can be useful
for removing various types of binders from the bulk green body
material, which provides intricate shaping capabilities. More
particularly, binders that can be chemically dissolved by certain
solutions or solvents can be chemically milled by directing a
stream of the reactive chemicals.
[0112] In another embodiment, electrochemical shaping can be based
on a controlled electrochemical dissolution process similar to
chemical-jet milling a green body comprised of a metal sinterable
particle. As such, the green metal body is attached to an
electrical source in order to allow an electrical current to assist
in the shaping.
[0113] In one embodiment, it can be beneficial for the
stream-cutting apparatus 112 to be configured as a hydro-cutting
apparatus or water-jet cutter. Hydro-cutting is essentially a
water-jet technology that uses the high force and high pressure of
a stream of water directed at the green body in order to cut and
shape the green body as desired. Hydro-cutting can be preferred
over some of the other stream-cutting technologies because it can
be free of heat, flame, and chemical reactions, and can provide a
precise cold shaping technique. However, heated water with or
without being doped with reactive chemicals can also be used.
[0114] A typical hydro-cutting apparatus for hardened materials can
use about 2.5 gallons of water per minute directed at the green
body at about 40,000 psi as a single stream. For example, a
hydro-cutting apparatus in accordance with the present invention
can use from about 0.25 gallon/minute to about 15 gallon/minute,
more preferably from about 0.5 gallon/minute to about 10
gallons/minute, even more preferably from about 1 gallon/minute to
about 5 gallons/minute, and most preferably about 2 gallons/minute
to about 4 gallons/minute. However, it should be recognized that
higher or lower flow rates can be used, and depend on the diameter
and pressure of the flow.
[0115] Additionally, the hydro-cutting apparatus can jet the water
at a force that ranges from about 50 psi to about 60,000 psi. This
is because there are instances where lower pressures, such as from
about 50 psi to 500 psi, can be used to ablate softer binders, and
some instances where more durable and harder binders may use from
about 15,000 psi to about 60,000 psi, especially when shaping
larger parts such as automobile or airplane parts or construction
materials. Additionally, water-jets similar to those used for
washing purposes can jet the water at about 1,000 psi to about
5,000 psi in order to shape a green body bound with a binder of
medium hardness. Thus, a wide range of water pressures can be
employed.
[0116] Moreover, the stream of water can be used at greatly varying
diameters. This is because the diameter of the flow drastically
affects the intricacy of the cutting or etching, where etching
green bodies for microelectronic circuit boards can require an
extremely fine diameter flow as small as about 0.5 mm, and carving
a rough shape and/or a larger article such as a tractor wheel rim
can use a flow diameter of about 2.54 cm. However, there are
instances where the use of a larger diameter, such as about 6 mm,
is first employed for rough shaping before fine and intricate
shapes are made with a jet of about 1 mm. Also, it is contemplated
that larger or smaller diameter water-jets can be used.
[0117] Additionally, hydro-cutting can be enhanced by the
introduction of particulate materials into the water feed line. As
such, some hydro-cutting techniques utilize garnet or other rigid
and strong materials in order to apply an abrasive cutting force
along with the force applied by the water itself. Also, the
hydro-cutting process in the present invention can be used with or
without inclusion of such abrasives.
[0118] Additionally, one of the benefits of hydro-cutting is the
ability to reutilize and recycle the spent water-jet material. As
such, the green body materials can be easily separated from the
spent water, thereby enabling the recycling and reuse of the water
during the hydro-cutting process.
[0119] In one embodiment, sandblasting, which fits into the regime
of stream of matter cutting, can be used to shape green bodies by
projecting a high energy stream of sand particles at the green body
material. Sandblasting cuts materials similar to hydro-cutting,
especially when the water-jet is doped with abrasive particulates.
Additionally, various other particulate streams other than sand can
be used in the stream-cutting techniques and machinery.
[0120] FIG. 8 illustrates an embodiment of a stream-cutting
assembly 350. The stream-cutting assembly 350 can be at least part
of the stream-cutting apparatus 112 as illustrated in FIG. 4,
and/or or the shaping system 230 of FIG. 7. Accordingly, the
stream-cutting assembly 350 can include a stream supply 352,
wherein at least a portion of the stream supply 352 is enclosed
within a housing 354. The stream supply 352 can be configured to
generate and/or supply a stream or energy. Alternatively, the
stream supply 352 can be configured to store and/or supply a stream
of matter.
[0121] Additionally, the housing can optionally include an aiming
apparatus 356. As such, the stream supply 352 can be configured to
supply a stream of energy and/or a stream of matter to be directed
through the aiming apparatus 356, which acts to aim or further
direct the stream of energy or stream of matter towards a green
body 364. As such, the aiming apparatus 356 can create an aimed
stream 358 with a trajectory aimed at a cutting site 360 on the
green body 364 so that a stream-cut surface 362 is formed
thereon.
[0122] In one embodiment, in order to enable precise
three-dimensional cutting and shaping, the green body 364 can be
retained on a turret 366 to rotate the green body 364.
Additionally, the stream-cutting assembly 350 can include a
mechanical feature 368 that is configured to move the green body
364 in various three-dimensional movements and/or rotations so that
the focused stream 358 can strike the green body 364 at various
cutting sites 360. The mechanical feature 368 along with the turret
366 can move the green body 364 in the x, y, and z axes and rotate
with a rotation "u" around the z-axis, a rotation "w" around the
y-axis, and rotation "v" around the x-axis. This enables a precise
and intricate structure to be cut into the green body 364 within
the stream-cutting assembly 350. Alternatively, the stream-cutting
assembly can move the stream relative to a stationary green body
364, as described in more detail below.
[0123] Accordingly, the mechanical feature 386 can move and/or
rotate the green body 364 by being outfitted with rubberized or
other malleable endpoints that contact the green body 364 so as to
not deform the green body 364. As such, these malleable endpoints
can provide favorable interactions with the green body 364 so as to
not deform, dent, crack, or otherwise stress or fatigue the green
body 364 during the stream-cutting process.
[0124] In another embodiment, the housing 354 of the stream-cutting
assembly 350 can include a coaxial gas assist device 370. Such a
coaxial gas assist device 370 can be configured to emit an assist
gas 372 during the stream-cutting procedure. An assist gas is a
flow of air, other type of gas, concurrent with, and often
peripheral to, the stream of energy or stream of matter.
Alternatively, a flow of a liquid (e.g., assist fluid), such as
water, can be used in place of an assist gas. A significant feature
of gas-assisted stream-cutting is that the material being cut from
the body is ejected or removed by the force of the gas jet coaxial
to the stream of energy or stream of matter to produce relatively
smooth stream-cut surfaces. Some examples of the different types of
gases that can be used in gas-assisted cutting include oxygen,
nitrogen, argon, and the like. Preferably, the gas is delivered at
a pressure up to about 15 bars. Additional information about
coaxial assist gas 372 will be described below.
[0125] In another embodiment, the stream-cutting assembly 350 can
include a scanner 374. Similar to the three-dimensional virtual
image generator 114 of FIG. 4, and/or the scanning system 230 of
FIG. 7, a scanner 374 can be implemented into the stream-cutting
assembly 350. The scanner 374 can be use to continuously or
intermittently scan the surface of the green body 364. Accordingly,
the scanner 374 emits a scanning beam 376 toward the green body
364, and more specifically toward any stream-cut surface 362. This
can monitor the cutting sites 360 as well as the stream-cut
surfaces 362. By including a scanner 374 in the stream-cutting
assembly 350, the cutting and shaping can be monitored so as to
ensure that the features formed thereon are in accordance, or
substantially similar, with the three-dimensional virtual image.
The scanning beam 376 and scanner 374 can be a part of a means of
scanning three-dimensional images, as is well known in the art.
[0126] In another embodiment, the stream-cutting assembly 350
includes a power blower 378. While the stream-cutting assembly 350
can include a coaxial gas device 370 in order to emit a coaxial
assist gas 372, such coaxial gas 372 maybe insufficient for
removing large pieces of green material cut from the bulk green
body 364. Accordingly, a power blower 378 can be used in order to
forcefully blow air, gas, or other fluid across the green body 364
so as to remove any particulates or large pieces of material.
Alternatively, the power blower 378 can be configured as a vacuum.
Similar to the power blower 387, a vacuum can also be used in order
to remove the particulates or large pieces of material cut away
from the green body 364. Thus, the power blower 378 can be used
intermittently during the stream-cutting protocol.
[0127] In another embodiment, along with the coaxial gas device
372, the power blower 378 can blow a cooling air or fluid so as to
cool the green body 364. This can be used to remove unwanted heat
from the green body 364 or to prevent undesired melting of the
binder or sinterable particles.
[0128] With reference now to FIGS. 9A, 9B, and 9C various features
and elements of an aiming apparatus 400 are now illustrated and
described. Such an aiming apparatus 400 can be used with the
shaping system 230 of FIG. 7 as well as the stream-cutting assembly
of FIG. 8.
[0129] In any event, the aiming apparatus 400 includes a nozzle 402
that is configured to emit a stream of energy 404, as represented
by the arrow being directed therethrough. Additionally, the nozzle
402 can be configured to emit a stream of matter 406, as
represented by the plurality of dots flowing through the nozzle
402. Accordingly, the nozzle 402 can be configured to aim the
stream of energy 404 and/or the stream of matter 406 toward a
cutting surface 410 on the green body 408. Thus, by aiming the
nozzle 402, precise and intricate shapes can be formed.
[0130] With particular reference to FIG. 9B, the aiming apparatus
400 includes an inner nozzle 402a that is encased within the lumen
of an outer nozzle 402b, which together forms a coaxial nozzle 412.
Such a coaxial nozzle 412 includes an inner chamber 413 to aim the
stream of energy 404 and/or the stream of matter 406. Additionally,
the coaxial nozzle 412 includes an outer or coaxial chamber 415,
wherein the outer or coaxial chamber 415 directs a flow of assist
gas 414.
[0131] As depicted in FIG. 9B, the coaxial nozzle 412 includes a
coaxial nozzle opening 416. The coaxial nozzle opening 416 includes
a first opening 419 for the stream of energy 404 and/or the stream
of matter 406 that is separate and independent from the second
opening 421 that provides the assist gas 414. In this
configuration, the coaxial nozzle opening 416 produces coaxial
eddies 418 of the assist gas 414 in a manner that removes and blows
away the cut particulates or materials.
[0132] With specific reference now to FIG. 9C, another embodiment
of a coaxial nozzle 402 is illustrated. As such, the coaxial nozzle
402 can include a combining aperture 420. Such a combining aperture
420 includes a single opening for the stream of energy 404 and/or
matter 406 as well as the assist gas 414. The combining aperture
420 can also produce eddies 422 to remove particles or matter from
the green body 408.
[0133] In any event, various configurations of stream nozzles 402
can be provided to produce a precisely cut green body 408 in
accordance with a virtual image or other desired shape. As such,
this can include providing streams of energy 404 and/or matter 406
along with the assist gas 414 in a manner that enhances the
stream-cutting protocol.
[0134] With reference now to FIG. 10, an embodiment of a
three-dimensional cutting system 450 is illustrated and described.
Such a three-dimensional cutting system 450 can be implemented in
the stream-cutting apparatus of 112 of FIG. 4 as well as in any
other stream-cutting system or process described herein.
Accordingly, the three-dimensional cutting system 450 includes a
three-dimensional cutting device 452 that is configured to move in
three-axes of movement. As such, the cutting device 452 can move
longitudinally in the z-axis, x-axis, and y-axis as well as rotate
in around each axis. This enables the cutting device 452 to move
about and around a green body 456 being cut.
[0135] In the illustrated embodiment, the cutting device 452
includes first body 454 attached to a swivel coupling 457 that is
configured such that it can rotate the first body 454 with a
rotation "u" around the z-axis. The swivel coupling 457 couples the
first body 454 with additional robotics (not shown) that enable
movement in various degrees of freedom. More particularly, another
swivel coupling (not shown) is included within the robotics that
can enable a rotation "w" around the y-axis. These rotations enable
the first body 452 to be move around the green body 456.
[0136] The cutting device 452 can also include a cutting nozzle 458
which is coupled with the first body 454 by a swivel coupling 460.
As such, the cutting nozzle 458 can also move in the x, y, and
z-axes along with the first body 454. Additionally, the swivel
coupling 460 allows for the cutting nozzle 458 to be capable of
rotating with a rotation "v" about the x-axis. By being capable of
additionally rotating with the "v" rotation, the three-dimensional
cutting device 452 is able to cut the green body 456 with precise
and intricate details in order to provide various shapes.
[0137] In another embodiment, the three-dimensional cutting system
450 includes a mechanical feature 462, which can be substantially
similar to the mechanical feature 386 of FIG. 8. Briefly, the
mechanical feature 462 is configured to move the green body 456
relative to the cutting device 452. As such, the mechanical feature
458 can move in the x, y, and z-axes, and also rotate with
rotations "u," "v" and "w." Thus, the mechanical feature 462 can
move independently of and/or in cooperation with the cutting nozzle
458, which can enable enhanced cutting techniques.
[0138] In one embodiment, any of the stream-cutting equipment,
systems, and/or processes can be configured to be operated and
controlled by a computer and associated software. As such, the
computer uses controlling software that receives input data from a
three-dimensional image of the shape to be cut into the green body.
The controlling software can obtain the input data from images that
have been generated or modified with CAD software. Accordingly, any
image that is stored within a computer memory, such as the data
storage device 234 illustrated in FIG. 7, can be used and
controlled by the stream-cutting apparatus in order to create a
three-dimensional structure from the green body material.
[0139] In one embodiment, the process or method of shaping a green
body can include cutting a first portion of the green body
intermediate away from a second portion with a stream of energy or
a stream of matter such as with a laser, electron beam, or
water-jet, so as to form a stream-cut surface such as a laser-cut
surface, electron beam-cut surface, or a water-jet-cut surface on
the resulting shaped green body. This can either form a
substantially smooth surface or an uneven surface.
[0140] In one embodiment, a process or method of stream-cutting a
green body can be conducted in a vacuum or under low pressure.
Also, the surface being stream-cut can be facing in a downward
direction (inverted) so that any material ejected from the surface
can fall away from the surface. When stream-cutting is performed on
an inverted surface, the green body can be rotated so that each
site being cut can have the removed green body materials fall free
and clear of the stream-cut surface. This can allow for the ejected
particles and/or binder to escape the surface without being
re-deposited adjacent to the feature being formed by the ejected
material. This can be especially favorable when the stream-cutting
procedure generates heat and melts the z m binder at the site being
cut because the melted binder can re-solidify after re-depositing,
which can produce irregular features. Thus, the process of
stream-cutting a green body can be performed so that smooth
surfaces and rounded features are formed in the external surface
without any re-deposited materials forming irregular features
adjacent to, or on, the stream-cut surface.
[0141] While various features and embodiments of stream-cutting
equipment, systems and processes have been discussed in connection
with the present invention various modifications can be made
thereto and still retain the inventive concept. As such, various
other streams of energy or streams of matter may be used in order
to cut the green body materials so as to provide the desired shape.
Additionally, the stream-cutting equipment, systems and processes
can be modified and changed, and still use streams of energy or
streams of matter to shape a green body intermediate.
IX. Sintering Green Bodies
[0142] A method of making a sintered body is in accordance with the
present invention in order to provide a sintered article prepared
from a shaped green body. Briefly, the sintered body can be
obtained from a green body that was prepared by molding a mixture
of sinterable particles and binder into the shape of a green body
intermediate. After the green body intermediate has been formed in
the mold, the process includes shaping with a stream of energy
and/or matter in order to obtain a green body having a desired
shape. The shaped green body can then be sintered in order to yield
a sintered article having the desired shape. The sintering can be
performed in a sintering apparatus 126 as depicted in FIG. 5. In
any event, sintering a shaped green body can result in an article
of manufacture that is either ready for use, or requires additional
processing or finishing.
[0143] In one embodiment, a de-binding process can be carried out
to remove the binder prior to sintering the shaped green body. As
such, the de-binding can be performed by heat treatment in an
oxidizing or non-oxidizing atmosphere, for instance, under a vacuum
or low pressure. For example, the de-binding can be performed at
about 1.times.10.sup.-1 Torr (13.3 Pa) to about 1.times.10.sup.-6
Torr (1.3.times.10.sup.-4 Pa). Alternatively, the de-binding can be
performed at a higher pressure such as 1.times.10.sup.-1 Torr (13.3
Pa) to about 1.times.10.sup.3 Torr (1.3.times.10.sup.5 Pa) or above
1.times.10.sup.3 Torr in nitrogen, argon, or other inert gas. Also,
the de-binding temperature can be within the range of about
80.degree. C. to about 750.degree. C., more preferably about
100.degree. C. to about 600.degree. C., and most preferably about
150.degree. C. to about 450.degree. C. In any event, the de-binding
can occur by melting, evaporating, or decomposing the binder.
[0144] In one embodiment, the sintering process can be performed in
an oxidizing or an inert gas at a low pressure from about
1.times.10.sup.-1 Torr (13.3 Pa) to about 1.times.10.sup.-6 Torr
(1.3.times.10.sup.-4 Pa) at an elevated temperature. Alternatively,
the sintering can be performed at a higher pressure such as
1.times.10.sup.-1 Torr (13.3 Pa) to about 1.times.10.sup.3 Torr
(1.3.times.10.sup.5 Pa) or above 1.times.10.sup.3 Torr at an
elevated temperature. As such, the binder can substantially removed
during the sintering process. Alternatively, the sintering process
can remove a substantial amount, but not all of binder, wherein
some of the binder can remain depending on the binding system. The
sintering temperature can range from about 750.degree. C. to about
2,500.degree. C., more preferably about 900.degree. C. to about
2,000.degree. C., and most preferably 1000.degree. C. to about
1500.degree. C.
[0145] Additionally, the sintering times can range from about 0.5
hours to about 15 hours, more preferably about 1 hour to about 10
hours, and most preferably about 2 hours to about 8 hours.
Sometimes, however, sintering can last up to about 24 hours.
Additionally, the sintering process should be modulated in order to
grow the sinterable powder grains into a dense sintered body.
Accordingly, the sintered body should have a high density with a
low porosity compared to the green body.
[0146] When the green body is sintered, the volume shrinks as the
porosity decreases and the density increases. This can happen as
the majority of the binder is melting and/or evaporating so as to
draw the individual sinterable particles closer together. As such,
the green body can be fabricated and shaped to be larger than the
resultant sintered article in order to accommodate for the volume
lost during sintering. The volume decrease between the size of a
green body and the size of a sintered article can range from about
10% to about 35%, more preferably about 12% to about 30%, and most
preferably about 15% to about 25%; however, a typical volume
decrease can be about 20%.
[0147] Since the volume of the green body will gradually decrease
during sintering, the various features carved into the shaped green
body can be fabricated so as to take shrinkage into account. This
can allow for the stream-cut features to be cut with a margin of
error, or to cut larger features than will be present after the
sintering process. Thus, when the green body is stream-cut, the
intricate shaping can result in even more precise and intricate
features after sintering.
[0148] Another result of the shrinkage can include the topology of
the sintered body becoming smoother when compared to the green body
prior to sintering. More particularly, when irregular features are
formed during stream-cutting, these features can be smoothed out
during sintering. On the other hand, this smoothing effect does not
necessarily have to remove any of rough features, but can create a
better surface with less obtuse or sharp edges.
[0149] In one embodiment, the sintering or de-binding process can
remove impurities or unfavorable deposits from the surface of the
sintered body. When the green body is cut with a stream of energy,
such as a laser, electron beam, ion beam and the like, that
generates heat in order to melt and/or vaporize the binder before
being sintering, the heat-cut surface on the sintered body can be
substantially devoid of being charred after the sintering process.
For example, when a sintered piece is laser-cut, these laser-cut
surfaces tend to be charred and blackened and require additional
processing or finishing in order to remove the charred or blackened
material. Charred bodies can present unfavorable characteristics
for many applications.
[0150] Accordingly, the sintering process and/or the de-binding
process can function to partially or substantially de-char the
particles, and hence the sintered body can be substantially devoid
of being charred or blackened at the heat-cut surfaces. Without
being bound to theory, it is thought that when the binder melts or
is otherwise removed from the green body the binder draws the
charred material away from the green body. This can occur during
the sintering or de-binding process because a portion of the binder
will melt and flow over the heat-cut surface and leech the charred
material away from the particles. Thus, when a green body is cut
with a heat generating stream of energy, the heat-cut surfaces can
similarly have charred surfaces; however, the heat-cut surface can
be less charred after being sintered compared to the same heat-cut
surface on the green body prior to being sintered.
[0151] Also, without being bound to any particular theory, it is
thought that an oxidized layer forms over the exterior surface of
the green body as it is being sintered, especially when in an
oxidizing atmosphere. Accordingly, shaping the green body with a
stream of energy or matter prior to sintering can allow for the
oxidized layer to form on the stream-cut surface during sintering.
The oxidized layer is thought to impart favorable characteristics
such as corrosion resistance, biocompatibility, and the like. On
the other hand, cutting a sintered article can destroy the oxidized
surface layer, and decrease or inhibit these favorable
characteristics. Thus, at least one stream-cut surface on the
sintered body can have a topology characterized by an oxidized
surface formed by sintering, wherein the sintering is conducted
after the green body has been cut and shaped as described
herein.
[0152] Additionally, the sintered body can be further processed
after sintering such as by grinding, sanding, or the like to
provide enhanced surface characteristics. Thus, at least one
stream-cut surface on the exterior surface of the sintered body can
have a smoother topology compared to at least one stream-cut
surface on an exterior surface of the shaped green body.
[0153] The present invention may be embodied in other specific
forms without departing from its spirit or essential
characteristics. The described embodiments are to be considered in
all respects only as illustrative and not restrictive. The scope of
the invention is, therefore, indicated by the appended claims
rather than by the foregoing description. All changes which come
within the meaning and range of equivalency of the claims are to be
embraced within their scope.
* * * * *