U.S. patent application number 14/012889 was filed with the patent office on 2015-03-05 for systems and methods for additive manufacturing of three dimensional structures.
The applicant listed for this patent is Elwha LLC. Invention is credited to Roderick A. Hyde, Lowell L. Wood, JR..
Application Number | 20150064047 14/012889 |
Document ID | / |
Family ID | 52583528 |
Filed Date | 2015-03-05 |
United States Patent
Application |
20150064047 |
Kind Code |
A1 |
Hyde; Roderick A. ; et
al. |
March 5, 2015 |
SYSTEMS AND METHODS FOR ADDITIVE MANUFACTURING OF THREE DIMENSIONAL
STRUCTURES
Abstract
A method of fabricating a three dimensional structure includes
delivering a metal material to a printing site; and defining a
microstructure of the metal material at the printing site by
controlling the delivery of heating energy to the printing site and
controlling the delivery of ultrasonic vibrations to the printing
site.
Inventors: |
Hyde; Roderick A.; (Redmond,
WA) ; Wood, JR.; Lowell L.; (Bellevue, WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Elwha LLC |
Bellevue |
WA |
US |
|
|
Family ID: |
52583528 |
Appl. No.: |
14/012889 |
Filed: |
August 28, 2013 |
Current U.S.
Class: |
419/26 ; 164/113;
419/55 |
Current CPC
Class: |
B22F 3/1055 20130101;
Y02P 10/295 20151101; Y02P 10/25 20151101; B23K 26/144 20151001;
B22F 3/1028 20130101; B22F 2999/00 20130101; B22F 2999/00 20130101;
B22F 3/1055 20130101; B22F 2201/01 20130101; B22F 2203/11
20130101 |
Class at
Publication: |
419/26 ; 419/55;
164/113 |
International
Class: |
B22F 3/105 20060101
B22F003/105; B22F 3/115 20060101 B22F003/115; B22F 3/24 20060101
B22F003/24 |
Claims
1. A method of fabricating a three dimensional structure,
comprising: delivering a metal material to a printing site; and
defining a microstructure of the metal material at the printing
site by: controlling the delivery of heating energy to the printing
site; and controlling the delivery of ultrasonic vibrations to the
printing site.
2. The method of claim 1, wherein delivering the metal material to
the printing site includes delivering a metal powder to the
printing site.
3. The method of claim 1, wherein delivering the metal material to
the printing site includes delivering a metal wire to the printing
site.
4. The method of claim 1, wherein delivering the metal material to
the printing site includes using a liquid metal jet.
5. (canceled)
6. The method of claim 1, wherein the heating energy is delivered
to the printing site by a laser.
7. The method of claim 1, wherein the heating energy is delivered
to the printing site by an electron beam.
8-18. (canceled)
19. The method of claim 1, further comprising monitoring a
temperature at the printing site and controlling delivery of at
least one of the heating energy and the ultrasonic vibrations based
on the temperature.
20-22. (canceled)
23. The method of claim 1, wherein defining the microstructure
includes defining a grain boundary.
24. The method of claim 1, wherein defining the microstructure
includes defining a grain size.
25. The method of claim 1, wherein defining the microstructure
includes defining a pinning point for the microstructure.
26-27. (canceled)
28. The method of claim 1, further comprising delivering a
vaporizable coolant to the printing site.
29-47. (canceled)
48. The method of claim 28, further comprising varying the pattern
of delivery of the vaporizable coolant between different portions
of the metal at the printing site.
49. The method of claim 28, further comprising varying an amount of
vaporizable coolant delivered to different portions of the metal at
the printing site.
50-51. (canceled)
52. A method of fabricating a three dimensional structure,
comprising: delivering a metal material to a printing site;
delivering heating energy to the printing site; delivering a
vaporizable coolant to the printing site; and defining a
microstructure for the three dimensional structure based on
providing the heating energy to the metal material at the printing
site and vaporizing the vaporizable coolant.
53-76. (canceled)
77. The method of claim 52, wherein the boiling point of the
vaporizable coolant corresponds to a predetermined quenching
temperature for the metal delivered to the printing site.
78. The method of claim 52, further comprising modifying the
boiling point of the vaporizable coolant.
79. The method of claim 78, wherein modifying the boiling point of
the vaporizable coolant includes modifying the composition of the
vaporizable coolant.
80. The method of claim 78, wherein modifying the boiling point of
the vaporizable coolant includes modifying a pressure of a delivery
environment for the vaporizable coolant.
81. (canceled)
82. The method of claim 52, further comprising varying the pattern
of delivery of the vaporizable coolant between different portions
of the metal at the printing site.
83-90. (canceled)
91. The method of claim 52, wherein the printing site is a first
printing site, the metal material is a first portion of metal
material, the heating energy is a first amount of heating energy,
and the vaporizable coolant is a first vaporizable coolant, and
further comprising: delivering a second portion of metal material
to a second printing site; delivering a second amount of heating
energy to the second printing site; and delivering a second
vaporizable coolant to the second printing site.
92. The method of claim 91, wherein the first portion of metal
material differs from the second portion of metal material in at
least one of an amount of metal and a type of metal.
93. The method of claim 91, wherein the first amount of heating
energy differs from the second amount of heating energy in at least
one of a duration of delivery of heating energy and an intensity of
delivery of heating energy.
94. The method of claim 91, wherein the first vaporizable coolant
varies from the second vaporizable coolant in at least one of a
type of coolant, a temperature of coolant, and an amount of
coolant.
95. A method of fabricating a three dimensional structure,
comprising: delivering a first metal material to a first printing
site; delivering a first amount of heating energy to the first
printing site; delivering a first vaporizable coolant to the first
printing site; agitating the first printing site; and forming a
first portion of a printed metal structure by providing the first
amount of heating energy to the first metal material at the first
printing site and vaporizing the first vaporizable coolant while
agitating the first printing site.
96-104. (canceled)
105. The method of claim 95, wherein agitating the first printing
site includes delivering ultrasonic vibrations to the first
printing site by a transducer.
106. The method of claim 95, wherein agitating the first printing
site includes delivering bulk acoustic waves.
107. The method of claim 95, wherein agitating the first printing
site includes delivering surface acoustic waves.
108. The method of claim 95, wherein agitating the first printing
site includes delivering ultrasonic vibrations to the first
printing site by phase conjugation.
109-110. (canceled)
111. The method of claim 95, wherein agitating the first printing
site includes generating a standing wave ultrasonic field.
112-115. (canceled)
116. The method of claim 95, further comprising varying the pattern
of delivery of the first vaporizable coolant between different
portions of the first printing site.
117. The method of claim 95, further comprising varying an amount
of the first vaporizable coolant delivered to different portions of
the first printing site.
118-121. (canceled)
122. The method of claim 95, further comprising delivering a second
metal material, a second amount of heating energy, and a second
vaporizable coolant to a second printing site, and agitating the
second printing site.
123. The method of claim 122, wherein the first metal material
differs from the second metal material in at least one of an amount
of material delivered and a type of material delivered.
124. The method of claim 122, wherein the first amount of heating
energy differs from the second amount of heating energy.
125. The method of claim 122, wherein the first vaporizable coolant
differs from the second vaporizable coolant in at least one of type
of coolant, a temperature of coolant, and amount of coolant
delivered.
126-242. (canceled)
Description
BACKGROUND
[0001] The present disclosure relates generally to the field of
additive manufacturing (also referred to as three dimensional (3D)
printing). Additive manufacturing has become more prevalent in
recent years as an option not only to rapidly produce prototypes,
but also to manufacture final products. While more commonly used to
produce polymer objects, current advances have allowed additive
manufacturing to also be used to produce metal objects.
SUMMARY
[0002] One embodiment relates to a method of fabricating a three
dimensional structure, comprising delivering a metal material to a
printing site; and defining a microstructure of the metal material
at the printing site by controlling the delivery of heating energy
to the printing site; and controlling the delivery of ultrasonic
vibrations to the printing site.
[0003] Another embodiment relates to a method of fabricating a
three dimensional structure, comprising delivering a metal material
to a printing site; delivering heating energy to the printing site;
delivering a vaporizable coolant to the printing site; and defining
a microstructure for the metal structure based on providing the
heating energy to the metal material at the printing site and
vaporizing the vaporizable coolant.
[0004] Another embodiment relates to a method of fabricating a
three dimensional structure, comprising delivering a first metal
material to a first printing site; delivering a first amount of
heating energy to the first printing site; delivering a first
vaporizable coolant to the first printing site; agitating the first
printing site; and forming a first portion of a printed metal
structure by providing the first amount of heating energy to the
first metal material at the first printing site and vaporizing the
first vaporizable coolant while agitating the first printing
site.
[0005] Another embodiment relates to a system for fabricating a
three dimensional structure, comprising a support for supporting
the structure; a material delivery device configured to provide a
metal material to a printing site; a heating energy delivery device
configured to heat the material at the printing site; and a
vibration delivery device configured to provide ultrasonic
vibrations to the printing site.
[0006] Another embodiment relates to a system for fabricating a
three dimensional structure, comprising a material delivery device
configured to deliver a metal material to a printing site; a
heating energy delivery device configured to deliver heating energy
to the printing site; a coolant delivery device configured to
deliver a vaporizable coolant to the printing site; and an
ultrasonic vibration delivery device configured to deliver
ultrasonic vibrations to the printing site.
[0007] Another embodiment relates to a method of forming a three
dimensional structure comprising delivering material, heating
energy, and vibrations to a first printing site to define a first
grain structure at the first printing site; and delivering
material, heating energy, and vibrations to a second printing site
to define a second grain structure at a second printing site;
wherein at least one of the delivered material, heating energy, and
vibrations differs between the first and second printing sites to
modify the second grain structure relative to the first grain
structure.
[0008] The foregoing summary is illustrative only and is not
intended to be in any way limiting. In addition to the illustrative
aspects, embodiments, and features descried above, further aspects,
embodiments, and features will become apparent by reference to the
drawings and the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a schematic perspective view of a system for
fabricating a three dimensional structure according to one
embodiment.
[0010] FIG. 2 is a schematic side view of a printing device of the
system of FIG. 1 according to one embodiment.
[0011] FIG. 3 is a schematic side view of a printing device of the
system of FIG. 1 according to another embodiment.
[0012] FIG. 4 is a schematic side view of a printing device of the
system of FIG. 1 according to another embodiment.
[0013] FIG. 5 is a schematic view of a microstructure of a three
dimensional structure according to one embodiment.
[0014] FIG. 6 is a block diagram of a control system for a device
for fabricating a three dimensional structure according to one
embodiment.
[0015] FIG. 7 is a flowchart of a method of fabricating a three
dimensional structure according to one embodiment.
[0016] FIG. 8 is a flowchart of a method of fabricating a three
dimensional structure according to another embodiment.
[0017] FIG. 9 is a flowchart of a method of fabricating a three
dimensional structure according to another embodiment.
DETAILED DESCRIPTION
[0018] In the following detailed description, reference is made to
the accompanying drawings, which form a part hereof. In the
drawings, similar symbols typically identify similar components,
unless context dictates otherwise. The illustrative embodiments
described in the detailed description, drawings, and claims are not
meant to be limiting. Other embodiments may be utilized, and other
changes may be made, without departing from the spirit or scope of
the subject matter presented here.
[0019] Additive manufacturing is a process in which an object is
built up layer by layer, with the desired geometry typically being
read from a computer file and recreated by extrapolating the
geometry into a series of thin layers. The layers may be cut and
joined together with a lamination process, formed by selectively
curing portions of a substance (e.g., stereolithography, etc.), or
formed by transforming a powdered material to a solid mass by
melting or otherwise fusing the powdered material together (e.g.,
selective laser sintering, fused deposition, laser deposition,
etc.). Current additive manufacturing processes often do not
produce objects with material properties that are suitable for use
as a final product. Instead, the objects are often more suitable
for display or prototype and proof-of-concept purposes.
[0020] Referring to the figures generally, systems and methods for
fabricating a metal object with an additive manufacturing process
are shown. In some embodiments, additive manufacturing is used to
form an object by depositing material at various printing sites, or
areas, in succession to eventually form a completed object. The
additive manufacturing process can be configured such that the
delivery of heating energy, material, cooling, and other processing
is controlled locally at each individual printing site (or,
alternatively, at sub-areas within an individual printing site).
The microstructure of the fabricated object may therefore be
controlled at each printing site and/or varied between printing
sites to achieve a desired grain size, phase concentration,
impurity concentration, pinning point distribution, or other
characteristic. In this way, the fabricated object can be
engineered to have superior material properties relative to objects
provided with more conventional processes.
[0021] Referring now to FIG. 1, printing system 10 (e.g., an
additive manufacturing system, etc.) configured to fabricate a
metal structure is shown according to one embodiment. Printing
system 10 includes printing device 12 (e.g., an additive or 3D
printing device, etc.) operated by control system 14. Printing
system 10 can form object 18 using digital data, such as a 3D
computer-aided design (CAD) model. Control system 14 may receive
additional instructions or data from auxiliary system 16. Auxiliary
system 16 may be, for example, an external drive or storage device
containing a CAD model and/or other control data. The CAD model may
be generated with any suitable CAD program, and may be stored in
any suitable digital file format. According to various alternative
embodiments, one or both of control system 14 and auxiliary system
16 can be integrated into device 12.
[0022] According to one embodiment, printing device 12 includes
frame 20 and delivery device 22 movable relative to frame 20 via
positioning system 24. Printing device 12 may include a multitude
of delivery devices configured to deliver a material (e.g., a
powdered metal, a metal wire, a liquid metal, etc.) to form object
18, as well as heating energy, cooling, agitation, or other means
of manipulating the material, as described in more detail below.
Printing device 12 forms object 18 by delivering and manipulating
the material at successive printing sites 19 (e.g. printing zones
or areas, work zones, delivery zones, fabrication zones, etc.).
Object 18 is formed in interior 38 of printing device 12. Interior
38 is defined by sidewalls 36. According to one embodiment,
interior 38 can be a sealed interior, which can have
characteristics different from the characteristics of the
surrounding environment. For example, the temperature, pressure, or
other characteristics (e.g., composition of atmospheric gases,
etc.) of interior 38 can be controlled to facilitate improved
fabrication of object 18. According to one embodiment, interior 38
can be maintained at a partial vacuum or in an atmosphere of an
inert gas (e.g., argon, helium, etc.).
[0023] According to one embodiment, positioning system 24 is
configured to position delivery device 22 using, for example,
coordinates provided to printing device 12 from control system 14.
Positioning system 24 can use a Cartesian coordinate system, with
delivery device 22 movable via carriage system 26. Carriage system
26 includes a rail oriented in the X direction and a rail in the Y
direction (providing X-Y horizontal movement), and a vertical
adjustment member 28 (providing Z direction vertical movement).
[0024] Object 18 is supported by object support platform 30, which
is in turn supported by frame 20. Platform 30 can be coupled to
frame 20 via positioning system 32. Positioning system 32 can be
configured to position support platform 30 using coordinates
provided to printing device 12 from control system 14. According to
one embodiment, support platform 30 is movable relative to frame 20
on a horizontal X-Y plane through carriage system 34. According to
a further embodiment, support platform 30 is further movable in a
vertical direction using a vertical adjustment member (e.g., a
vertical adjustment member similar to vertical adjustment member
28, etc.). According to another embodiment, support platform 30 may
not be movable and may instead be rigidly coupled to frame 20.
[0025] According to another embodiment, rather than using an X-Y-Z
Cartesian coordinate system, positioning systems 24 and 32 may use
an alternative coordinate system, such as a cylindrical coordinate
system, to position delivery device 22 and/or support platform 30.
According to other embodiments, positioning systems 24 and 32 may
be configured to tilt or rotate support platform 30 or delivery
device 22 about any of the X, Y, Z, or another positioning
axis.
[0026] Positioning systems 24, 32 are configured to properly
position object 18 relative to delivery device 22 during the 3D
printing of object 18. Object 18 is formed through an additive
process, with material being selectively added to object 18 by
delivery device 22 at printing site 19. The added material is
joined together or fused with material in neighboring printing
sites (e.g., material below the printing site 19 on another plane,
material surrounding the printing site 19 on the same plane, etc.)
to form a solid object.
[0027] Referring now to FIG. 2, a portion of printing device 50 is
shown according to one embodiment as a laser deposition device.
Printing device 50 can be incorporated into a 3D printing system
such as system 10 or a similar system. Printing device 50 forms
object 52 supported by platform 54. Object 52 is formed from
material 56 delivered from first delivery device 58 to printing
site 60. Material 56 is melted by heating energy 62 delivered to
printing site 60 from first delivery device 58 (e.g., via a laser,
etc.). According to one embodiment, material 56 can be melted by
heating energy 62 (e.g., heat or energy provided as radiant energy,
etc.) and manipulated during and/or after the application of
heating energy 62 with coolant 64 delivered to the printing site 60
from second delivery device 66, and/or energy such as ultrasonic
vibrations generated by a transducer shown as agitation device 68.
The manipulation of material 56 during formation at printing site
60 enables the controlled formation of a desired microstructure of
material 56.
[0028] According to one embodiment, material 56 is or includes a
powdered metal material (e.g., tool steel, stainless steel (e.g.,
420, 316, 304, etc.), nickel alloys, cobalt alloys, titanium
alloys, etc.). The powdered metal is supplied to first delivery
device 58 from a supply (e.g., hopper, feeder, bin, etc.). The
powdered metal is ejected from first delivery device 58 from one or
more nozzles 59. Multiple nozzles 59 can be angled relative to one
another to focus the streams of material 56 at printing site 60
spaced a distance away from first delivery device 58. The flow rate
of material 56 and the speed at which first delivery device 58 is
moved relative to object 52 can be controlled to achieve a desired
thickness for each printing site and/or layer of material forming
object 52.
[0029] While in some embodiments, material 56 is delivered to
printing site 60 as a metal powder, according to other embodiments,
material 56 may be a metal delivered in another form. For example,
material 56 may be a solid metal delivered as a wire fed from first
delivery device 58 to printing site 60, or alternatively, may be a
liquid metal delivered as a liquid metal stream or jet from first
delivery device 58 to printing site 60. Material 56 can be
delivered in various other forms according to various alternative
embodiments.
[0030] According to further embodiments, material 56 may be
provided by material streams from several different supplies. For
example, a primary material may be mixed with additives, such as
particles configured to act as catalysts for nucleation, or grain
refiners configured to retard the growth of dendritic grains. In
other embodiments, material 56 may be provided by different
elemental streams, with the flow rate of the different streams
varied during the fabrication of object 52 to achieve different
alloy compositions in different portions of object 52.
[0031] According to one embodiment, first delivery device 58 is
configured to provide a first material at a first printing site and
a second material at a second printing site. For example, the
amount of material, the rate of deposition of material, the
composition of the material, or other parameters may be varied
between the first material delivered to the first printing site and
the second material delivered to the second printing site. Varying
various parameters associated with the delivery of material to
different printing sites enables variation of the microstructure
(e.g., grain structure, etc.) between printing sites.
[0032] Referring further to FIG. 2, in one embodiment, heating
energy 62 is provided by a laser directed at printing site 60 by
first delivery device 58. The laser may be any suitable laser
capable of providing the heating energy needed to melt material 56.
For example, the laser may be a fiber laser with an optical fiber
doped with a rare-earth element (e.g., erbium, ytterbium,
neodymium, etc.), another type of solid-state laser, or a gas
laser. In some embodiments, first delivery device 58 may further
provide a volume (e.g., envelope, sleeve, etc.) of a shielding gas
surrounding the laser and/or material 56 that differs from the
atmosphere in the interior of the printing device to provide a more
favorable environment for the fabrication of object 52 (e.g., to
limit oxidation, etc.).
[0033] The laser provided by first delivery device 58 is configured
to generate a "melt pool" of molten material, and provide precise
control of the size and depth of the melt pool. As such, a
relatively narrow heat-affected zone surrounds the melt pool,
thereby minimizing thermal distortion of the portions of object 52
surrounding printing site 60. Printing site 60 can be heated by any
method or combination of methods, including through the use of a
laser. According to other embodiments, heating energy 62 can be
provided via first delivery device 58 in another form, such as an
electron beam or a micro-arc. According to still another
embodiment, heating energy 62 can be delivered to printing site 60
through conduction by local resistance heating of object 52, by
thermal conduction from a (small) heat source contacting printing
site 60, or by controlling the temperature of material 56 delivered
to printing site 60.
[0034] In one embodiment, first delivery device 58 focuses heating
energy 62 at printing site 60 (e.g., with a lens, etc.), and
material 56 melts to form a melt pool. First delivery device 58
forms a bead of material (e.g., a weld bead, etc.) as it is moved
relative to platform 54. The bead includes material deposited at
successive printing sites, and forms a layer of solidified material
on the X-Y plane. The bead may be a continuous bead of material, or
alternatively, a non-continuous bead of material. Successive layers
of material are fused together to form object 52. By controlling
the delivery of heating energy 62 to printing site 60, the melting
of material 56 can be controlled. Although controlling only the
delivery of heating energy 62 provides some control over the
post-melting solidification of material 56 and of the resulting
microstructure of object 52, more precise control is possible, as
in conventional metal formation, by also controlling the quenching
(i.e., the cooling) of the molten metal.
[0035] According to one embodiment, first delivery device 58 is
configured to vary the heating energy provided to first and second
printing sites. For example, the amount of heating energy, the
intensity of heating energy, the delivery method, or other
parameters may be varied between the first and second printing
sites. Varying various parameters associated with the delivery of
heating energy to different printing sites enables variation of the
microstructure (e.g., grain structure, etc.) between printing
sites.
[0036] In one embodiment, the microstructure of object 52 is
further controlled through cooling of the melt pool (e.g., material
56) at printing site 60. For example, a coolant 64 can be locally
delivered by second delivery device 66. Second delivery device 66
can be any mechanism suitable for the delivery of coolant 64 to
printing site 60. Coolant 64 can be delivered directly to printing
site 60, or alternatively, can be delivered indirectly to printing
site 60 by, for example, cooling areas of object 52 surrounding
printing site 60 (i.e., neighboring printing sites) or by cooling
platform 54 supporting object 52. By locally cooling printing site
60, the microstructure of different portions of object 52 can be
individually controlled and/or varied.
[0037] The material at printing site 60 is locally cooled in a
controlled manner, either through the direct or indirect cooling of
the material. Local, controlled cooling allows the quenching of the
material to be controlled to a greater degree than, for example,
bulk cooling object 52, or allowing object 52 to cool slowly to
room temperature. Controlling the quenching of the material enables
for the controlled formation of a desired microstructure (e.g., the
transformation of austenite to martensite in steel, etc.) in object
52. In some embodiments, the delivery of coolant 64 can be delayed
to allow the material to remain at an elevated temperature for a
period of time.
[0038] Printing site 60 can be locally cooled by thermal conduction
to a small cooling probe such as a thermoelectric cooler, a heat
pipe, a mini-cooling loop, or the like. In other embodiments,
printing site 60 can be cooled by applying coolant 64 which absorbs
energy from printing site 60. Coolant 64 can respond to the
absorbed heat by increasing its temperature (i.e., via its specific
heat) and/or by undergoing a phase change (i.e., via latent heat).
A vaporizable liquid coolant provides an effective embodiment of
coolant 64, because vaporization of the liquid provides an
efficient way to absorb heat and because the coolant is directly
removed from the site as it vaporizes, without leaving residuals.
Coolant 64 can be a liquid with a relatively low boiling point, or
alternatively, a liquid with a relatively high boiling point, with
coolant 64 chosen such that the boiling point of coolant 64
corresponds to a desired quench temperature and/or cooling rate for
the material at printing site 60. Coolant 64 can be or include
water, alcohol, an oil, a solvent, or a liquid metal, including,
but not limited to, sodium, sodium-potassium alloy, sodium-lithium
alloy, lithium, or a mixture of liquid metals. In some embodiments,
the boiling point of coolant 64 can be varied by controlling the
pressure of the interior of printing device 50, by modifying the
composition of coolant 64, etc.
[0039] According to one embodiment, delivery device 66 is
configured to deliver a high-speed stream of coolant 64 in the form
of a vaporizable liquid to printing site 60. According to another
embodiment, delivery device 66 is an atomizer configured to deliver
liquid coolant 64 as a mist. According to yet another embodiment,
delivery device 66 is or includes a device such as a wick, brush,
or tube that directs a low-speed stream of a liquid coolant to
printing site 60. According to a further embodiment, delivery
device 66 can be a fan configured to direct a stream of coolant 64
in the form of a gas (e.g., air, an inert gas, etc.) at printing
site 60 to cool material by convection. According to various
alternative embodiments, combinations of one or more coolant
delivery devices can be used to deliver coolant 64.
[0040] In one embodiment, coolant 64 is not delivered directly to
material to printing site 60, but rather is provided as a part of a
heat pipe or similar system incorporated into or separate from
delivery device 66. A heat pipe can include a casing with a first
end proximate the melt pool at printing site 60 (e.g., on the
surface of the object 52). The first end of the heat pipe absorbs
heat through the walls of the casing and vaporizes a liquefied
coolant contained within the casing. The vaporized coolant releases
latent heat at a second end and condenses back to a liquid. One or
both ends of the heat pipe can include features such as a heat sink
to facilitate the transfer of heat between the outside environment
and the coolant contained within the heat pipe. The coolant
contained within the heat pipe can be chosen to achieve a preferred
heat transfer from printing site 60. The internal pressure of the
heat pipe can also be chosen and/or varied to control the phase
changes of the coolant and further control the heat transfer from
the printing site.
[0041] According to one embodiment, coolant 64 can be delivered
continuously to printing site 60. Alternatively, coolant 64 can be
delivered intermittently (e.g., in a digital manner, etc.) to
printing site 60 to achieve a desired microstructure. Various
coolants, delivery devices, and delivery durations may be utilized
for object 52 to form a metallic structure with varied
microstructures. In some embodiments, delivery device 66 can be
operated based on feedback data collected from sensors monitoring
the fabrication of object 52, as described in more detail
below.
[0042] Printing device 50 may further include a system for removing
coolant (e.g., vaporized or heated liquid coolant) from the surface
of object 52 or the interior of printing device 50, after the
coolant has been utilized to cool printing site 60. For example,
printing device 50 may include a gas circulation system (e.g.,
incorporated into delivery device 66 or another component of the
printing system) configured to remove gas from the interior of
printing device 50 through an outlet duct and introduce gas to the
interior of the printing device through an inlet duct. After being
removed from the interior of printing device 50, the gas may be
scrubbed, cooled or otherwise processed and returned back to the
interior of printing device 50. Printing device 50 may include
multiple inlet and outlet ducts such that the ducts can be opened,
closed, or reversed to advantageously control the movement of gas
within the interior of printing device 50 and across the surface of
object 52, including proximate printing site 60.
[0043] According to one embodiment, delivery device 66 is
configured to provide a first coolant to a first printing site and
a second coolant to a second printing site. For example, the type
of coolant, the amount of coolant, the timing or rate of delivery
of coolant, the predefined delivery temperature of the coolant, the
composition of the coolant, or other parameters may be varied
between the first and second printing sites. In some embodiments,
the delivery of heating energy (e.g., from delivery device 58) may
be interrupted during the delivery of the coolant. In some
embodiments, the delivery of coolant can be nonsimultaneous with
the delivery of heating energy at a site. In some embodiments, the
delivery of coolant can begin after the delivery of heat energy
begins at a site. In some embodiments the delivery of coolant can
continue after the delivery of heat energy has stopped at a site.
Varying various parameters associated with the delivery of coolant
to different printing sites enables variation of the microstructure
(e.g., grain structure, etc.) between printing sites.
[0044] In some embodiments, the microstructure of object 52 is
further controlled by subjecting the material at printing site 60
to agitation, such as by sound waves (e.g., acoustic waves,
ultrasonic waves, etc.). According to one embodiment, the waves are
generated by agitation device 68 (e.g., agitator, wave generator,
etc.) and directed at object 52. Agitation device 68 is positioned
and configured to direct the waves to printing site 60 to induce
local vibration in object 52. According to various alternative
embodiments, agitation device 68 can be a piezoelectric transducer,
a magnetostrictive transducer, a surface acoustic wave (SAW)
generator, a bulk acoustic wave (BAW) generator, or a standing wave
field generator (e.g., an ultrasonic wave field generator, etc.).
According to one embodiment, as shown in FIG. 2, agitation device
68 can be positioned remote from printing site 60 and can be
configured such that the waves are steered to or focused at
printing site 60. Wave generation and steering and/or focusing can
utilize a coherent array of wave generators (e.g., with phase
and/or amplitude control of each); phase conjugation can be used to
help control such remote wave delivery. According to another
embodiment, agitation device 68 can be positioned proximate to
printing site 60.
[0045] In one embodiment, agitation device 68 provides ultrasonic
vibrations to printing site 60. Ultrasonic vibrations applied to a
solidifying metal or alloy can decrease the size of the grains,
increase the soundness of the grains, and/or decrease the
occurrence of dendritic grain formation in the material. When
molten material in the melt pool at printing site 60 is near the
melting point (for a pure metal) or liquidus temperature (for an
alloy), ultrasonic waves can influence the formation of solid
nuclei, which leads to the corresponding formation of grains in the
solidifying material, the grains being increased in number and
decreased in size.
[0046] The amplitude and frequency of the waves produced by
agitation device 68 can be controlled to produce grains of a
desired size. According to one embodiment, agitation device 68 is
configured to produce waves with a frequency selected based on a
desired microstructure (e.g., grain size, etc.). The frequency
produced by agitation device 68 can be maintained at a constant
level for the entire fabrication process, or alternatively, can be
altered to facilitate the growth of grains of different desired
sizes in different portions of object 52. The wavelength of the
waves produced by agitation device 68 can also be configured to
produce grains of a desired size. In some embodiments, the delivery
of waves can be nonsimultaneous with the delivery of heating energy
at a site. In some embodiments, the delivery of waves can begin
after the delivery of heat energy begins at a site. In some
embodiments, the delivery of waves can continue after the delivery
of heat energy has stopped at a site, e.g., to perform ultrasonic
peening. In some embodiments, agitation device 68 may be operated
based on feedback data collected from sensors monitoring the
fabrication of object 52, as described in more detail below.
[0047] According to one embodiment, agitation device 68 is
configured to provide differing waves to induce different
vibrations at first and second printing sites. For example, the
amplitude, wavelength, or other parameters associated with the
delivery of the waves may be varied between the first and second
printing sites. Varying various parameters associated with
providing vibrations to different printing sites enables variation
of the microstructure (e.g., grain structure, etc.) between
printing sites.
[0048] According to one embodiment, the microstructure of object 52
can be further controlled by subjecting the material in the melt
pool at printing site 60 to other processing or conditions. For
example, magnet 69 can be provided proximate to printing site 60.
Magnet 69 produces a magnetic field that passes through printing
site 60. For magnetic materials (e.g., many steel alloys) the
magnetic field influences the grain formation as the material in
the melt pool solidifies and cools. Magnet 69 can be a permanent
magnet generating a constant magnetic field, or may be a variable
magnet (e.g., an electromagnet) that can be controlled to produce a
variable magnetic field.
[0049] Referring further to FIG. 2, in some embodiments, printing
site 60 is monitored to provide feedback data to printing device
12. The data may then be utilized by printing device 12 to control
the printing process to achieve the desired microstructure in
object 52. According to one embodiment, printing device 50 may
include image monitoring device 70, and one or more sensors 72 to
collect data from printing site 60.
[0050] In one embodiment, image monitoring device 70 (e.g., an
image capturing device, etc.) is configured to monitor the
microstructure of object 52. Image monitoring device 70 can be an
optical microscope, an electron microscope, an x-ray microscope,
etc. Optical microscopes can be used to examine relatively large
microstructures, while electron microscopes and x-ray microscopes
can be used to examine relatively small images (e.g., features or
structures smaller than approximately one half micron). Image
monitoring device 70 may include multiple devices, allowing the
microstructure of object 52 to be examined at different scales
simultaneously. Image monitoring device 70 captures an image (e.g.,
a still image or a video) of object 52. The image may be
transferred to an analysis device and be utilized to collect data
concerning the microstructure at printing site 60, such as an
average grain size, or the formation of various phases of the
material. According to one embodiment, image monitoring device 70
captures images of object 52 after the material at printing site 60
has solidified. Image monitoring device 70 may therefore be
configured to capture images of an area trailing the current
printing site 60. Image monitoring device 70 may be configured to
collect further visual data, such as by capturing an image of a
portion of object 52 surrounding the current printing site 60. The
additional image data may be utilized, for example, to monitor the
heat-induced distortions in the microstructure of object 52
surrounding printing site 60, as caused by the heating energy
provided to create the melt pool at printing site 60.
[0051] Sensors 72 may be configured to collect a wide variety of
data concerning the portions of object 52 at printing site 60.
According to one embodiment, sensor 72 can be or include a
thermometer configured to monitor the temperature of printing site
60 or the portion of object 52 surrounding printing site 60. For
example, sensor 72 may be a contact thermometer, such as a
thermocouple in direct contact with object 52, or may be a
non-contact thermometer, such as an infrared thermometer that is
disposed away from object 52. Sensor 72 may be an array of multiple
thermometers configured to monitor the temperature at several
locations at and/or surrounding printing site 60. According to
another embodiment, sensor 72 can be or include a vibration
transducer configured to monitor the longitudinal or shear waves
produced by agitation device 68. According to other embodiments,
sensor 72 may include multiple types of sensors that operate
together to monitor multiple phenomena related to the
solidification of the material forming object 52.
[0052] Referring now to FIG. 3, a portion of printing device 80 is
shown according to one embodiment as a laser deposition device.
Printing device 80 forms object 82 supported by a platform 84 in a
manner similar to the printing device 50 shown and discussed with
respect to FIG. 2. Object 82 is formed from a material 86 delivered
from a first delivery device 87 to printing site 90. Material 86 is
melted by heating energy 92 delivered to printing site 90 from a
second delivery device 89. According to one embodiment, material 86
is manipulated during and/or after the application of heating
energy 92 with substances such as coolant 94 delivered to printing
site 90 from third delivery device 97, energy such as vibrations
generated by agitation device 98, or by a magnetic field generated
by magnet 99. The delivery of material 86 and heating energy 92 via
separate delivery devices 87 and 89 may advantageously provide for
the improved melting of material 86 and/or creation of a melt pool
at printing site 90.
[0053] According to one embodiment, the additive manufacturing
system is configured to provide, or define, different
microstructure at or within different portions of an object. For
example, as discussed in greater detail below, one or more image
capture devices, sensors, etc. may be configured to provide
feedback regarding the formation of an object, and in response, one
or more parameters associated with the delivery of material,
heating energy, vibrations, coolant, etc. can be varied between
printing sites.
[0054] After being formed with a printing process, the fabricated
object may be subjected to further processing, such as heat
treating (e.g., annealing, tempering, etc.) and the like. Such
post-printing processing enables further altering of the
microstructure and the mechanical properties of the material beyond
what may be possible during the 3D printing process.
[0055] Referring now to FIG. 4, a schematic top view of a portion
of printed metal object 100 is shown according to one embodiment.
Material from delivery device 102 is melted and solidified at
printing site 104. In one embodiment, as delivery device 102 is
moved relative to object 100, bead 106 of solidified material is
formed on the surface of object 100 (the surface of the object
being material printed at previous print sites and/or in previous
layers). By controlling the delivery of material and heating energy
to printing site 104, as well as the delivery of ultrasonic or
acoustic waves and the rate of cooling through the delivery of a
coolant, the mechanical properties of object 100 can be controlled.
The heat affected zone 108 can be minimized by providing heating
energy to printing site 104 in the form of a laser or an electron
beam. Locally controlling the heating energy, material, agitation,
cooling, and other factors, as opposed to subjecting the entirety
of object 100 to "bulk" conditions (e.g., with a bulk cooling
process, etc.), allows the mechanical properties of object 100 to
be varied between different areas/printing sites of object 100.
Mechanical properties may be further controlled within different
portions of printing site 104 (e.g., local cooling or quenching of
material may generate a microstructure in center 110 of printing
site 104 that is different than the microstructure at the periphery
of printing site 104).
[0056] Referring now to FIG. 5, an example microstructure of an
object formed by the printing devices disclosed herein is shown. A
desired microstructure is created by locally controlling the
heating energy, material, agitation, cooling, and other factors as
the material is printed, thereby allowing the fabricated object to
have desired mechanical properties (e.g., strength, toughness,
ductility, hardness, etc.). According to one embodiment, the
microstructure is configured to have a relatively small grain
structure including a multitude of small grains 120 (e.g.,
crystallites) separated by grain boundaries 122. Grain boundaries
122 represent disconnects between crystal lattices of neighboring
grains 120, and impede the movement of dislocations through the
material. A fine grain structure increases the number of grain
boundaries 122, and increases the yield strength of the material. A
large grain structure, conversely, lowers the yield strength of the
material, but increases ductility and electrical and thermal
conductivity. Local control of heating energy, material, agitation,
cooling, and other factors allows the grain structure to be
written, or printed, as desired, allowing different portions of the
manufactured object to have different mechanical properties. The
local control of the printing process may also be used to vary the
mechanical properties of the material in other ways, such as by
varying the presence and/or concentrations of different phases of
the material, the presence and/or concentration of dislocations,
pinning points, impurities, etc.
[0057] Referring now to FIG. 6, a schematic block diagram of
printing system 130 is shown according to one embodiment. Printing
system 130 includes 3D printing device 132 operated by control
system 134. Printing device 132 forms an object using digital data,
such as a 3D computer-aided design (CAD) model. Printing device 132
can be the same or similar to any of the other printing devices
discussed herein. Furthermore, printing system 130 may include one
or more auxiliary systems 136 (e.g., computer systems, etc.).
[0058] According to one embodiment, control system 134 includes
processor 140 and memory 142. Processor 140 may be implemented on a
chip, integrated circuit, circuit board, etc., as a general purpose
processor, an application specific integrated circuit (ASIC), one
or more field programmable gate arrays (FPGAs), a group of
processing components, or other suitable electronic processing
components. Memory 142 can be or include one or more devices (e.g.,
RAM, ROM, Flash memory, hard disk storage, etc.) for storing data
and/or computer code for completing and/or facilitating the various
processes described herein. Memory 142 can be or include
non-transient volatile memory or non-volatile memory or
non-transitory computer readable storage media. Memory 142 can
include database components, object code components, script
components, or any other type of information structure for
supporting the various activities and information structures
described herein. Memory 142 can be communicably connected to the
processor and include computer code or instructions executable by
the processor for executing one or more processes described herein.
Control system 134 can include one or more modules configured to
use data and code stored in memory 142 to execute a process via
processor 140.
[0059] Control system 134 further includes input device 144 and
output device 146. Input device 144 can be a mouse, keyboard,
trackball, touchscreen or any other device that allows a user to
input instructions to control system 134. Input device 144 can be
used, for example, in combination with a graphical user interface
to allow a user to control various parameters associated with the
operation and monitoring of printing device 132 or auxiliary
systems 136. Output device 146 can be a visual output device, such
as a monitor (e.g., a CRT monitor, LCD monitor, LED monitor, etc.),
an audio device, or another device.
[0060] Control system 134 can receive additional instructions or
data from auxiliary system 136. Auxiliary system 136 can be, for
example, an external drive or storage device containing the CAD
model and other control data. The CAD model can be generated with
any suitable CAD program and can be stored in any suitable digital
file format. The geometry of the CAD model is analyzed and divided
into a multitude of slices, layers, or portions that correspond to
portions to be printed by printing device 132.
[0061] As shown in FIG. 6, printing device 132 includes positioning
system 150, material delivery system 152, heating energy delivery
system 154, coolant delivery system 156, and agitation system 158.
Positioning system 150 controls the positions of the delivery
devices relative to the platform on which the object is fabricated,
and can be or include any of the positioning systems discussed
herein. Positioning system 150 controls the delivery devices to
form a bead of material in a desired path on the X-Y plane. In some
embodiments, multiple passes of the delivery device in the X-Y
(horizontal) plane forms a slice or layer of the object as defined
by the CAD model. Movement of the delivery devices in the Z
(vertical) direction positions the delivery devices to form
successive layers. According to one embodiment, positioning system
150 may further control the position of the platform on which the
object is formed, either in addition to or instead of controlling
the position of the delivery devices. Positioning system 150 may
further control the orientation of the delivery devices and/or the
platform through rotation about one or more axis (e.g., the X-axis,
Y-axis, Z-axis, etc.).
[0062] Material delivery system 152 controls the delivery of
material from a supply to the printing site via a material delivery
device, and can include any of the material delivery devices
discussed herein. Material delivery system 152 can, for example,
control the flow rate of a powdered or a liquid metal or the feed
rate for a solid wire to the printing site. Material delivery
system 152 can control the delivery ratio of two or more materials
to a printing site to alter the composition of the material of
different portions of the fabricated object. As such, different
materials can be delivered to different printing sites of an
object.
[0063] Heating energy delivery system 154 controls the delivery of
heating energy to the printing site via a heating energy delivery
device, and can include any of the heating energy delivery devices
discussed herein. Heating energy delivery system 154 can control
the operation of a laser, including focusing the laser at the
printing site and controlling the power output of the laser. The
heating energy delivery system 154 can operate the laser to provide
continuous heating energy to the printing site, or can activate and
deactivate the laser to provide intermittent heating energy to the
printing site. According to other embodiments, heating energy
delivery system 154 can be configured to control an electron beam
or another heating energy delivery device, such as resistance
heater configured to supply an electrical voltage applied to the
object to heat the printing site by resistance heating.
[0064] Coolant delivery system 156 controls the delivery of coolant
(e.g., a liquid or gas coolant) to the printing site via a coolant
delivery device to reduce the temperature of the material at a
desired rate, and can include any of the coolant delivery devices
discussed herein. For example, coolant delivery system 156 can
control the flow rate of a high pressure stream of a liquid coolant
directed at the printing site or at a portion of the fabricated
object proximate to the printing site. Coolant delivery system 156
can vary the type of coolant delivered or the rate/amount of
coolant delivered depending on the material used and the desired
cooling time. In some embodiments, the delivery of coolant can be
delayed to allow the material to remain at an elevated temperature
for a period of time.
[0065] Agitation system 158 controls the generation and delivery of
sound energy to the printing site. Agitation system 158 can operate
an agitation device (e.g., agitator, wave generator, etc.) to
generate ultrasonic or acoustic waves at a desired amplitude and
frequency, and can include any of the agitation devices discussed
herein. Agitation system 158 can be configured to continuously
generate waves, or alternatively, can be configured to engage and
disengage the agitation device to intermittently generate
waves.
[0066] Printing device 132 can further include other systems 159.
Other systems 159 can be utilized to, for example, control a magnet
(e.g., an electromagnet) to generate a desired magnetic field at
the printing site, or any other suitable device. Furthermore, it
should be noted that according to various alternative embodiments,
one or both of systems 156, 158 may be omitted.
[0067] Printing device 132 further includes a monitoring system 160
for monitoring the operation of the other systems of printing
device 132 and the object fabricated by printing device 132.
Monitoring system 160 can be configured to visually monitor the
printing site and the portions of the object surrounding the
printing site. Monitoring system 160 can adjust the focus and/or
magnification of a monitoring device (e.g., an optical microscope,
electron microscope, etc.) to obtain an image of the microstructure
of the material. In one embodiment, monitoring system 160 is
configured to collect other data, such as pressure data (e.g., to
monitor ultrasonic vibrations) and temperature, with a variety of
sensors. The sensors can be positioned on the surface of the
fabricated object or away from the object. The sensors are
configured to collect data from the printing site, a portion of the
object near the printing site, an area of the object away from the
printing site, or the interior of the printing device. Data
collected by monitoring system 160 is used to provide feedback on
the formation of the object. The data can be used to adjust the
parameters of one of the other systems (e.g., positioning system
150, material delivery system 152, heating energy delivery system
154, coolant delivery system 156, agitation system 158 or other
systems 159) to adjust the microstructure of the object. The
adjustments can be initiated automatically (e.g., by processor 140)
or alternatively can be initiated manually (e.g., by a user with
input device 144). For example, in one embodiment, processor 140
receives inputs from monitoring system 160 (e.g., temperature data,
pressure data, etc.), and provides control signals to one or more
of systems 150, 152, 154, 156, 158, and 159 based on the
inputs.
[0068] Referring now to FIG. 7, method 170 of fabricating a 3D
metal structure with an additive manufacturing system is shown
according to one embodiment. A material (e.g., material 56 or
material 86) is delivered to a printing site (172). According to
various embodiments, the amount, location, type, etc. of material
provided can be controlled, and can vary within and between
printing sites. Heating energy (e.g., heating energy 62 or heating
energy 92) is delivered to the printing site (174). As discussed
above, heating energy can be provided in a variety of ways, and the
amount of heating energy and other parameters can be varied within
and between printing sites. The printing site is agitated (e.g., by
way of ultrasonic or acoustic waves generated by agitation device
68 or agitation device 98) (176). For example, various types of
ultrasonic waves can be continuously and/or intermittently
provided, and various characteristics of the waves (e.g.,
frequency, amplitude, etc.) can be varied within and between
printing sites. The resulting properties of the fabricated metal
structure are then monitored and the data is utilized to adjust the
control parameters for the delivery of material, heating energy,
and agitation to the printing site, or alternatively, to a
subsequently printed portion of the printing site or a subsequently
printed printing site (178). The process can then continue for
subsequent printing sites until the object is formed.
[0069] Referring now to FIG. 8, method 180 of fabricating a 3D
metal structure using an additive manufacturing system is shown
according to another embodiment. Material (e.g., material 56 or
material 86) is delivered to a printing site (182). Heating energy
(e.g., heating energy 62 or heating energy 92) is delivered to the
printing site (184). The delivery of material and/or heating energy
to the printing site can be controlled in a manner similar to that
discussed with respect of FIG. 7. A coolant (e.g., coolant 64 or
coolant 94) is delivered to the printing site (186). The amount,
location, type etc. of coolant provided can be varied within and
between printing sites. The resulting properties of the fabricated
metal structure are then monitored and the data is utilized to
adjust the control parameters for the delivery of material, heating
energy, and coolant to the printing site, or alternatively, to a
subsequently printed portion of the printing site or a subsequently
printed printing site (188).
[0070] Referring now to FIG. 9, method 190 of fabricating a 3D
metal structure using an additive manufacturing system is shown
according to another embodiment. Material (e.g., material 56 or
material 86) is delivered to a printing site (192). Heating energy
(e.g., heating energy 62 or heating energy 92) is delivered to the
printing site (194). The printing site is agitated (e.g., by way of
ultrasonic or acoustic waves generated by agitation device 68 or
agitation device 98) (195). A coolant (e.g., coolant 64 or coolant
94) is delivered to the printing site (196). Other process
parameters, such as the delivery of a magnetic field, etc. to the
printing site can further be controlled (197). The resulting
properties of the fabricated metal structure are then monitored and
the data is utilized to adjust the control parameters for the
delivery of material, heating energy, agitation, coolant and other
processes (198). The method illustrated in FIG. 9 may control the
delivery of material, heating energy, agitation, coolant, or other
processes in a manner similar to that discussed with respect of
FIGS. 7 and 8.
[0071] While the systems and methods described herein relate to the
fabrication of a metal part with laser deposition or similar
technology, the local control of printing variables, along with
monitoring and feedback systems, may be useful for other additive
manufacturing processes involving metals or non-metals. For
example, a selective laser sintering process may be utilized to
form an object, and the process can be monitored to detect the size
and concentration of pores in the fabricated object. This data may
then be utilized to control, for example, the power output of the
laser to achieve a desired final product. The systems and methods
disclosed herein may be used in combination with other fabrication
techniques according to various other alternative embodiments.
[0072] The present disclosure contemplates methods, systems, and
program products on any machine-readable media for accomplishing
various operations. The embodiments of the present disclosure may
be implemented using existing computer processors, or by a special
purpose computer processor for an appropriate system, incorporated
for this or another purpose, or by a hardwired system. Embodiments
within the scope of the present disclosure include program products
comprising machine-readable media for carrying or having
machine-executable instructions or data structures stored thereon.
Such machine-readable media can be any available media that can be
accessed by a general purpose or special purpose computer or other
machine with a processor. By way of example, such machine-readable
media can comprise RAM, ROM, EPROM, EEPROM, CD-ROM or other optical
disk storage, magnetic disk storage or other magnetic storage
devices, or any other medium which can be used to carry or store
desired program code in the form of machine-executable instructions
or data structures and which can be accessed by a general purpose
or special purpose computer or other machine with a processor. When
information is transferred or provided over a network or another
communications connection (either hardwired, wireless, or a
combination of hardwired or wireless) to a machine, the machine
properly views the connection as a machine-readable medium. Thus,
any such connection is properly termed a machine-readable medium.
Combinations of the above are also included within the scope of
machine-readable media. Machine-executable instructions include,
for example, instructions and data which cause a general purpose
computer, special purpose computer, or special purpose processing
machines to perform a certain function or group of functions.
[0073] Although the figures may show a specific order of method
steps, the order of the steps may differ from what is depicted.
Also two or more steps may be performed concurrently or with
partial concurrence. Such variation will depend on the software and
hardware systems chosen and on designer choice. All such variations
are within the scope of the disclosure. Likewise, software
implementations could be accomplished with standard programming
techniques with rule based logic and other logic to accomplish the
various connection steps, processing steps, comparison steps and
decision steps.
[0074] While various aspects and embodiments have been disclosed
herein, other aspects and embodiments will be apparent to those
skilled in the art. The various aspects and embodiments disclosed
herein are for purposes of illustration and are not intended to be
limiting, with the true scope and spirit being indicated by the
following claims.
* * * * *