U.S. patent application number 15/324672 was filed with the patent office on 2017-07-20 for layerwise heating, linewise heating, plasma heating and multiple feed materials in additive manufacturing.
The applicant listed for this patent is APPLIED MATERIALS ,INC.. Invention is credited to Thomas B. Brezoczky, Kasiraman Krishnan, Srinivas D. Nemani, Hou T. Ng, Nag B. Patibandla, Kartik Ramaswamy, Christopher A. Rowland, Swaminathan Srinivasan, Anantha K. Subramani, Jennifer Y. Sun, Simon Yavelberg.
Application Number | 20170203363 15/324672 |
Document ID | / |
Family ID | 55064857 |
Filed Date | 2017-07-20 |
United States Patent
Application |
20170203363 |
Kind Code |
A1 |
Rowland; Christopher A. ; et
al. |
July 20, 2017 |
LAYERWISE HEATING, LINEWISE HEATING, PLASMA HEATING AND MULTIPLE
FEED MATERIALS IN ADDITIVE MANUFACTURING
Abstract
An additive manufacturing system that includes a platen, a feed
material delivery system configured to deliver feed material to a
location on the platen specified by a computer aided design program
and a heat source configured to raise a temperature of the feed
material simultaneously across all of the layer or across a region
that extends across a width of the platen and scans the region
across a length of the platen. The heat source can be an array of
heat lamps, or a plasma source.
Inventors: |
Rowland; Christopher A.;
(Rockport, MA) ; Subramani; Anantha K.; (San Jose,
CA) ; Krishnan; Kasiraman; (Milpitas, CA) ;
Ramaswamy; Kartik; (San Jose, CA) ; Brezoczky; Thomas
B.; (Los Gatos, CA) ; Srinivasan; Swaminathan;
(Pleasanton, CA) ; Sun; Jennifer Y.; (Mountain
View, CA) ; Yavelberg; Simon; (Cupertino, CA)
; Nemani; Srinivas D.; (Sunnyvale, CA) ;
Patibandla; Nag B.; (Pleasanton, CA) ; Ng; Hou
T.; (Campbell, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
APPLIED MATERIALS ,INC. |
Santa Clara |
CA |
US |
|
|
Family ID: |
55064857 |
Appl. No.: |
15/324672 |
Filed: |
July 8, 2015 |
PCT Filed: |
July 8, 2015 |
PCT NO: |
PCT/US2015/039609 |
371 Date: |
January 6, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62022428 |
Jul 9, 2014 |
|
|
|
62183522 |
Jun 23, 2015 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22F 2003/1057 20130101;
B29C 64/153 20170801; B23K 10/027 20130101; B22F 2003/1051
20130101; B22F 2998/10 20130101; B22F 3/008 20130101; H05B 3/0061
20130101; B33Y 30/00 20141201; B23K 10/006 20130101; B28B 1/001
20130101; B33Y 10/00 20141201; B33Y 50/02 20141201 |
International
Class: |
B22F 3/00 20060101
B22F003/00; B33Y 10/00 20060101 B33Y010/00; H05B 3/00 20060101
H05B003/00; B33Y 50/02 20060101 B33Y050/02; B23K 10/02 20060101
B23K010/02; B23K 10/00 20060101 B23K010/00; B28B 1/00 20060101
B28B001/00; B33Y 30/00 20060101 B33Y030/00 |
Claims
1. An additive manufacturing system comprising: a platen; a feed
material dispenser assembly configured to deliver a first feed
material over the platen in a pattern specified in a
computer-readable medium to form a layer of feed material over the
platen; a heat source configured to apply heat to all of the layer
of feed material simultaneously; and a controller configured to
cause the heat source to raise a temperature of all of the layer of
feed material simultaneously to a temperature sufficient to cause
the first feed material to fuse.
2. The system of claim 1, wherein the heat source comprises an
array of heat lamps configured to heat all of the layer
simultaneously.
3. The system of claim 1, wherein the heat source comprises a
plasma source.
4. An additive manufacturing system comprising: a platen; a feed
material dispenser apparatus configured to deliver a first feed
material over the platen in a pattern specified in a
computer-readable medium to form a layer of feed material over the
platen; a heat source configured to apply heat simultaneously to a
region of the layer of feed material extending across a width of
the platen and to scan the region across a length of the platen;
and a controller configured to cause the heat source to raise a
temperature of the region of the layer of feed material
simultaneously to a temperature sufficient to cause the first feed
material to fuse.
5. The system of claim 4, wherein the region is substantially
linear and the heat source is configured to scan the region in a
direction perpendicular to a primary axis of the region.
6. The system of claim 5, wherein the heat source comprises a laser
to generate a laser beam and the system comprises optics that
receive the laser beam and expand a cross section of the laser beam
along the width of the platen.
7. The system of claim 4, wherein the heat source comprises a
linear array of heat lamps.
8. The system of claim 4, comprising an actuator coupled to at
least one of the heat source or platen to cause the region to scan
across the length of the platen.
9-15. (canceled)
16. The system of claim 1 or 4, comprising a secondary heat source
configured to raise the layer of feed material to a temperature
below a temperature at which the first feed material fuses.
17-18. (canceled)
19. The system of claim 16, wherein the controller is configured to
cause the heat source to apply heat to all of the layer of feed
material simultaneously after the secondary heat source heats the
layer of feed material.
20. The system of claim 1 or 4 wherein the feed material delivery
system comprises a first dispenser configured to dispense the first
feed material and a second dispenser configured to dispense a
second feed material, the layer of feed material comprising the
first material and the second material.
21. The system of claim 20, wherein the first feed material fuses
at a first temperature and the second feed material fuses at a
second temperature, the first temperature being lower than the
second temperature.
22. The system of claim 21, wherein the controller is configured to
cause the heat source to raise the temperature of the layer of feed
material simultaneously to a temperature below the second
temperature.
23-26. (canceled)
27. The system of claim 20, wherein the first dispenser and the
second dispenser each comprises a gate that is individually
controllable and the gate is configured to release respective first
or second feed material at locations on the platen according to the
pattern specified in the computer-readable medium.
28. The system of claim 27, wherein the gate comprises an element
selected from the group consisting of a piezoelectric printhead, a
pneumatic valve, a microelectromechanical systems (MEMS) valve, a
solenoid valve and a magnetic valve.
29. The system of claim 1 or 4, wherein the feed material delivery
system comprises a line of dispensers configured to deliver a line
of feed material simultaneously, the line of dispensers configured
to be translated across the platen to deliver a layer of feed
material.
30. The system of claim 1 or 4, wherein the feed material delivery
system comprises a two dimensional array of dispensers configured
to deliver all of the layer simultaneously.
31. A method of additive manufacturing, comprising: dispensing a
layer of a first feed material over a platen in a pattern specified
in a computer-readable medium; and heating all of the layer of feed
material simultaneously above a temperature at which the first feed
material fuses.
32. A method of additive manufacturing, comprising: dispensing a
layer of feed material over a platen in a pattern specified in a
computer-readable medium; simultaneously heating a region of the
layer of feed material that extends across a width of the platen to
a temperature above a temperature at which the feed material fuses;
and scanning the region across a length of the platen.
33. (canceled)
Description
CLAIM OF PRIORITY
[0001] This application claims priority under 35 USC .sctn.119(e)
to U.S. Patent Application Ser. No. 62/022,428, filed on Jul. 9,
2014 and to U.S. Patent Application Ser. No. 62/183,522, filed on
Jun. 23, 2015.
TECHNICAL FIELD
[0002] This present invention relates to additive manufacturing,
also known as 3D printing.
BACKGROUND
[0003] Additive manufacturing (AM), also known as solid freeform
fabrication or 3D printing, refers to any manufacturing process
where three-dimensional objects are built up from raw material
(generally powders, liquids, suspensions, or molten solids) in a
series of two-dimensional layers or cross-sections. In contrast,
traditional machining techniques involve subtractive processes and
produce objects that are cut out of a stock material such as a
block of wood, plastic or metal.
[0004] A variety of additive processes can be used in additive
manufacturing. The various processes differ in the way layers are
deposited to create the finished objects and in the materials that
are compatible for use in each process. Some methods melt or soften
material to produce layers, e.g., selective laser melting (SLM) or
direct metal laser sintering (DMLS), selective laser sintering
(SLS), fused deposition modeling (FDM), while others cure liquid
materials using different technologies, e.g. stereolithography
(SLA).
[0005] Sintering is a process of fusing small grains, e.g.,
powders, to creating objects from smaller grains, e.g., powders
using atomic diffusion. Sintering usually involves heating a
powder. The powder used in sintering need not reach a liquid phase
during the sintering process, in contrast to melting. When a
powdered material is heated to a temperature below the melting
point in a sintering process, the atoms in the powder particles
diffuse across the boundaries of the particles, fusing the
particles together to form a solid piece. As the sintering
temperature does not have to reach the melting point of the
material, sintering is often used for materials with high melting
points such as tungsten and molybdenum.
[0006] Both sintering and melting can be used in additive
manufacturing. The material being used determines which process
occurs. An amorphous solid, such as acrylonitrile butadiene styrene
(ABS), is actually a supercooled viscous liquid, and does not
actually melt; as melting involves a phase transition from a solid
to a liquid state. Thus, selective laser sintering (SLS) is the
relevant process for ABS, while selective laser melting (SLM) is
used for crystalline and semi-crystalline materials such as nylon
and metals, which have a discrete melting/freezing temperature and
undergo melting during the SLM process.
[0007] Conventional systems that use a laser beam as the energy
source for sintering or melting a powdered material typically
direct the laser beam on a selected point in a layer of the
powdered material and selectively raster scan the laser beam to
locations across the layer. Once all the selected locations on the
first layer are sintered or melted, a new layer of powdered
material is deposited on top of the completed layer and the process
is repeated layer by layer until the desired object is produced. As
the density of the finished object depends on the peak laser power
and not on the duration of the laser irradiation, conventional
systems typically use a pulsed laser.
[0008] An electron beam can also be used as the energy source to
cause sintering or melting in a material. Once again, the electron
beam needs to be raster scanned across the layer to complete the
processing of a particular layer.
SUMMARY
[0009] In one aspect, an additive manufacturing system includes a
platen, a feed material dispenser apparatus configured to deliver a
first feed material onto the platen in a pattern specified by a
computer aided design program to form a layer of the feed material
on the platen, a heat source configured to apply heat to all of the
layer of feed material simultaneously; and a controller configured
to cause the heat source to raise a temperature of all of the layer
of feed material simultaneously to a temperature sufficient to
cause the first feed material to fuse.
[0010] In another aspect an additive manufacturing system includes
a platen, a feed material dispenser apparatus configured to deliver
a first feed material onto the platen in a pattern specified by a
computer aided design program to form a layer of feed material on
the platen, a heat source configured to apply heat simultaneously
to a region of the layer of feed material extending across a width
of the platen and to scan the region across a length of the platen;
and a controller configured to cause the heat source to raise a
temperature of the region of the layer of feed material
simultaneously to a temperature sufficient to cause the first feed
material to fuse.
[0011] In another aspect, an additive manufacturing system, the
system includes a platen, a feed material delivery system
configured to deliver feed material to a location on the platen
specified by a computer aided design program, and a heat source
configured to raise a temperature of the feed material at two or
more locations on the platen simultaneously.
[0012] In another aspect, a method of additive manufacturing
includes dispensing a layer of feed material on a platen, the layer
of feed material including a first plurality of cells formed of a
first feed material and a second plurality of cells formed of a
second feed material. The first feed material has a first sintering
or melting temperature and the second feed material has having a
different second sintering or melting temperature, and the method
includes heating all of the layer of feed material simultaneously
to a temperature above the first sintering or melting temperature
and below the second sintering or melting temperature.
[0013] In another aspect, a method of additive manufacturing
includes dispensing a layer of feed material on a platen, the layer
of feed material including a first plurality of cells formed of a
first feed material and a second plurality of cells formed of a
second feed material. The first feed material has a first sintering
or melting temperature and the second feed material has having a
different second sintering or melting temperature. The method
includes simultaneously heating a region of the layer of feed
material that extends across a width of the platen to a temperature
above the first sintering or melting temperature and below the
second sintering or melting temperature, and scanning the region
across a length of the platen.
[0014] In another aspect, an additive manufacturing system includes
a platen, a feed material dispenser apparatus configured to deliver
a feed material onto the platen in a pattern specified by a
computer aided design program to form a layer of the feed material
on the platen, and a plasma source configured to generate an
electrical potential in all of the layer of feed material
simultaneously, the electrical potential being sufficient to cause
fusing of the feed material.
[0015] In another aspect, an additive manufacturing system includes
a platen, a feed material dispenser assembly configured to deliver
a first feed material over the platen in a pattern specified in a
computer-readable medium to form a layer of feed material over the
platen, a heat source configured to apply heat to all of the layer
of feed material simultaneously, and a controller configured to
cause the heat source to raise a temperature of all of the layer of
feed material simultaneously to a temperature sufficient to cause
the first feed material to fuse.
[0016] In another aspect, a method of additive manufacturing
includes dispensing a layer of a first feed material over a platen
in a pattern specified in a computer-readable medium, and heating
all of the layer of feed material simultaneously above a
temperature at which the first feed material fuses.
[0017] Implementations of either the above system or method can
include one or more of the following features.
[0018] The heat source may include an array of heat lamps
configured to heat all of the layer simultaneously. The array of
heat lamps may be positioned directly above the platen. The heat
source may include a plasma source. The plasma source may be
configured to cause charged particles to bombard the layer of feed
material. Th plasma source may be configured to generate an
electrical potential in portions of the layer of feed material
simultaneously, the electrical potential being sufficient to cause
fusing of the first feed material. The system may include a
secondary heat source configured to raise the layer of feed
material to a temperature below a temperature at which the first
feed material fuses. The secondary heat source may include a
resistive heater embedded in the platen. The controller may be
configured to cause the heat source to apply heat to all of the
layer of feed material simultaneously after the secondary heat
source heats the layer of feed material.
[0019] The feed material delivery system may include a first
dispenser configured to dispense the first feed material and a
second dispenser configured to dispense a second feed material, the
layer of feed material comprising the first material and the second
material. The first feed material may fuse at a first temperature
and the second feed material may fuse at a second temperature that
is higher than the first temperature. The controller may be is
configured to cause the heat source to raise the temperature of the
layer of feed material simultaneously to a temperature below the
second temperature. The first dispenser and the second dispenser
may each include a gate that is individually controllable and the
gate may be configured to release respective first or second feed
material at locations on the platen according to the pattern
specified in the computer-readable medium. The gate may be a
piezoelectric printhead, a pneumatic valve, a
microelectromechanical systems (MEMS) valve, a solenoid valve or a
magnetic valve. The system may include a second heat source in the
platen. The controller may be configured to cause the second heat
source to maintain a base temperature of the platen at an elevated
temperature lower than both the first and second temperature.
[0020] The heat source may be positioned on a same side of the
platen as the dispenser and be configured to apply radiant heat to
all of the layer simultaneously. The heat source may be spaced from
the platen sufficiently for the dispenser to pass between the heat
source and the platen. The heat source may include an array of heat
lamps configured to heat all of the layer simultaneously. The heat
source may be positioned on a side of the platen farther from the
dispenser. The heat source may be embedded in the platen and be
configured to apply conductive heat to the layer.
[0021] The feed material delivery system may include a line of
dispensers configured to deliver a line of feed material
simultaneously. The line of dispensers may be configured to be
translated across the platen to deliver a layer of feed material.
The feed material delivery system may include a two dimensional
array of dispensers configured to deliver all of the layer
simultaneously. A piston may be configured to actuate the platen
vertically. The controller may be configured to cause the piston to
be lowered after a layer of feed material has been heated and prior
to the feed material delivery system delivering a second layer of
feed material above the layer of feed material that has been
heated.
[0022] In another aspect, an additive manufacturing system includes
a platen, a feed material dispenser apparatus configured to deliver
a first feed material over the platen in a pattern specified in a
computer-readable medium to form a layer of feed material over the
platen, a heat source configured to apply heat simultaneously to a
region of the layer of feed material extending across a width of
the platen and to scan the region across a length of the platen,
and a controller configured to cause the heat source to raise a
temperature of the region of the layer of feed material
simultaneously to a temperature sufficient to cause the first feed
material to fuse.
[0023] In another aspect, a method of additive manufacturing
includes dispensing a layer of feed material over a platen in a
pattern specified in a computer-readable medium, simultaneously
heating a region of the layer of feed material that extends across
a width of the platen to a temperature above the first sintering or
melting temperature and below the second sintering or melting
temperature, and scanning the region across a length of the
platen.
[0024] Implementations of either the above system or method can
include one or more of the following features.
[0025] The region may be substantially linear, and the heat source
may be configured to scan the region in a direction perpendicular
to a primary axis of the region. The heat source may include a
laser to generate a laser beam and optics may receive the laser
beam and expand a cross section of the laser beam along the width
of the platen. The optics may include a beam expander and a
cylindrical lens. A mirror galvanometer to cause the region to scan
across the length of the platen. The heat source may include a
linear array of heat lamps. An actuator may be coupled to at least
one of the heat source or platen to cause the region to scan across
the length of the platen. A secondary heat source may be configured
to raise the layer of feed material to a temperature below a
temperature at which the first feed material fuses. The secondary
heat source may include a resistive heater embedded in the
platen.
[0026] The feed material delivery system may include a first
dispenser configured to dispense the first feed material and a
second dispenser configured to dispense a second feed material, so
that the layer of feed material includes the first material and the
second material. The first feed material may fuses at a first
temperature and the second feed material may fuses at a second
temperature higher than the first temperature. The controller may
be configured to cause the heat source to raise the temperature of
the layer of feed material simultaneously to a temperature below
the second temperature. A second heat source may be located in the
platen, and the controller may be configured to cause the second
heat source to maintain a base temperature of the platen at an
elevated temperature lower than both the first and second
temperature.
[0027] In another aspect, an additive manufacturing system includes
a platen, a feed material dispenser apparatus configured to deliver
a first feed material over the platen, and a plasma source
configured to generate a plasma that causes fusing of the first
feed material.
[0028] In another aspect, a method of additive manufacturing
includes dispensing a layer of feed material over a platen, and
generating a plasma that causes fusing of the first feed
material.
[0029] Implementations of either the above system or method can
include one or more of the following features.
[0030] The plasma source may include two electrodes and a power
source to supply a radio frequency voltage to at least one of the
two electrodes. A first electrode of the two electrodes may be in
or on the platen. A second electrode of the two electrodes may be
suspended above the platen. The power supply may be configured to
supply a radio frequency voltages having a first frequency to one
of the two electrodes, and to supply a radio frequency voltage
having a second frequency to the other one of the two electrodes,
with the first frequency different from the second frequency.
[0031] The platen may be supported in a chamber, e.g., a vacuum
chamber. A gas inlet may be configured to introduce a gas into the
chamber. The gas may be configured to form ions, and the power
source may be configured drive the electrodes at a power and
frequency such that the ions are caused to be embedded into the
layer.
[0032] The plasma source may be configured to generate a plasma
that extends across the platen and raise all of the layer of feed
material simultaneously to a temperature sufficient to cause the
first feed material to fuse. The dispenser may be configured to
deliver the first feed material in a pattern specified in a
computer-readable medium.
[0033] The feed material delivery system may include a first
dispenser configured to dispense the first feed material and a
second dispenser configured to dispense a second feed material, so
that the layer of feed material includes the first material and the
second material. The first feed material may fuse at a first
temperature and the second feed material may fuses at a second
temperature that is higher than the first temperature. The plasma
source may be configured to generate plasma that does not cause
fusing of the second feed material. A second heat source may be
configured raise the layer of feed material to an elevated
temperature lower than both the first and second temperature.
[0034] In another aspect, an additive manufacturing system includes
a platen, a feed material dispenser apparatus to dispense a layer
of feed material over the platen, a heat source, and a controller.
The feed material dispenser apparatus includes a first dispenser
configured to dispense a first feed material and a second dispenser
configured to dispense a second feed material, such that the layer
of feed material comprises the first feed material and the second
feed material. The first feed material may fuses at a first
temperature and the second feed material may fuses at a higher
second temperature. The a heat source may be configured to heat to
the layer of feed material to a temperature sufficient to cause the
first feed material to fuse but insufficient to cause the second
feed material to fuse. The controller may be configured to cause
the dispenser to dispense the first feed material in a pattern
specified in a computer-readable medium.
[0035] Implementations may include one or more of the following
features. The controller may be configured to cause the feed
material dispenser to dispense one of either the first feed
material or the second configured at each voxel in the layer of
feed material. The heat source may be configured to heat all of the
layer of feed material to the temperature simultaneously. The first
dispenser and the second dispenser may each include a gate that is
individually controllable, and the gate may be configured to
release respective first or second feed material at locations on
the platen according to the pattern specified in the
computer-readable medium. The gate may include an element selected
from the group consisting of a piezoelectric printhead, a pneumatic
valve, a microelectromechanical systems (MEMS) valve, a solenoid
valve and a magnetic valve.
[0036] In another aspect, an additive manufacturing system includes
a platen, a feed material dispenser apparatus to dispense a layer
of feed material over the platen, a heat source and a controller.
The feed material dispenser apparatus includes a first dispenser
configured to dispense a first feed material and a second dispenser
configured to dispense a second feed material, such that the layer
of feed material comprises the first feed material and the second
feed material. The first feed material fuses at a first temperature
and the second feed material fuses at a higher second temperature.
The heat source is configured to apply heat to all of the layer of
feed material simultaneously. The controller is configured to cause
the dispenser to dispense the first feed material in a pattern
specified in a computer-readable medium and to cause the heat
source to raise a temperature of all of the layer of feed material
simultaneously to a temperature above the first temperature and
below the second temperature.
[0037] In another aspect, a method of additive manufacturing
includes dispensing a layer of feed material on a platen, the layer
of feed material including a first plurality of cells formed of a
first feed material and a second plurality of cells formed of a
second feed material, wherein the first feed material fuses at a
first temperature and the second feed material fuses at a different
second temperature, and heating all of the layer of feed material
simultaneously to a temperature above the first temperature and
below the second temperature.
[0038] Implementations can provide one or more of the following
advantages. The number and size of thermal fluctuations experience
by the material can be reduced. Material properties of the
fabricated object can be more spatially uniform. The time needed to
fabricate an object can be reduced. For example, for a cube having
a length L, the time needed to fabricate the cube can scale as L or
L.sup.2 rather than L.sup.3.
[0039] The details of one or more embodiments of the invention are
set forth in the accompanying drawings and the description below.
Other aspects, features, and advantages of the invention will be
apparent from the description and drawings, and from the
claims.
DESCRIPTION OF DRAWINGS
[0040] FIG. 1A is a schematic view of an additive manufacturing
system.
[0041] FIG. 1B is a schematic view of the additive manufacturing
system after a few layers of material have been fabricated.
[0042] FIG. 2A is a schematic view of a point dispenser.
[0043] FIG. 2B is a schematic view of a line dispenser.
[0044] FIG. 2C is a schematic view of an array dispenser.
[0045] FIG. 2D is a schematic of a through-silicon-via in two
different modes of operation.
[0046] FIG. 3A is a schematic view of an additive manufacturing
system.
[0047] FIG. 3B is a schematic view of a particle on a cathode.
[0048] FIG. 3C is a schematic view of driving pulse sequence. Like
reference symbols in the various drawings indicate like
elements.
DETAILED DESCRIPTION
[0049] A point on a layer of a powdered material that is being
sintered or melted by a pulsed laser beam experiences a series of
abrupt temperature fluctuations as the laser beam delivers energy
to locations in the vicinity of that point during raster scanning.
When a new layer of powdered material is deposited over a completed
layer, the same point on the completed layer experiences another
series of abrupt temperature fluctuation as heat deposited by the
pulsed laser beam is conducted from the top layer to the completed
layer. Such temperature fluctuations can cause changes in
temperature of more than 1500.degree. C. at a particular point in
the layer and can repeat every 2-3 second, depending on the scan
rate of the laser beam.
[0050] The large temperature fluctuations caused by the
point-by-point sintering or melting of a powdered material can
create thermal stresses within the printed object. Furthermore,
material properties, such as the grain size of the sintered
material may vary due to variations in the thermal history at
different locations in the finished object. For example, the
increase in temperature may cause localized regions of the sintered
or melted portion to recrystallize and form a region that has a
different grain size from a neighboring region. In order to obtain
more repeatable material properties in the fabricated object,
better control of grain size is desired.
[0051] The time needed to fabricate objects using point-to-point
sintering or melting techniques scales with the third power of a
linear dimension of the object. For example, for a cube having a
length L, the time needed to fabricate the cube would scale as
L.sup.3.
[0052] FIG. 1A shows a schematic of an exemplary additive
manufacturing system 100. The system 100 includes and is enclosed
by a housing 102. The housing 102 can, for example, allow a vacuum
environment to be maintained in a chamber 103 inside the housing,
but alternatively the interior of the chamber 103 can be a
substantially pure gas or mixture of gases, e.g., a gas or mixture
of gases that has been filtered to remove particulates, or the
chamber can be vented to atmosphere. The vacuum environment or the
filtered gas can reduce defects during manufacture of a part. For
some implementations, the chamber 103 can be maintained at a
positive pressure, i.e., above atmospheric pressure. This can help
prevent the external atmosphere from entering the chamber 103.
[0053] The additive manufacturing system 100 includes a material
dispenser assembly 104 positioned above a platen 120. A vertical
position of the platen 120 can be controlled by a piston 132. After
each layer of powder has been dispensed and fused, the piston 132
can lower the platen 120 and any layers of powder thereon, by the
thickness of one layer, so that the assembly is ready to receive a
new layer of powder.
[0054] The platen 120 can be sufficiently large to accommodate
fabrication of large-scale industrial parts. For example, the
platen 120 can be at least 500 mm across, e.g., 500 mm by 500 mm
square. For example, the platen can be at least 1 meter across,
e.g., 1 meter square.
[0055] A controller 140 controls a drive system (not shown), e.g.,
a linear actuator, connected to the dispenser assembly 104. The
drive system is configured such that, during operation, the
dispenser assembly is movable back and forth parallel to the top
surface of the platen 120 (along the direction indicated by arrow
106). For example, the dispenser assembly 104 can be supported on a
rail that extends across the chamber 103. Alternatively, the
dispenser assembly 104 could be held in a fixed position, while the
platen 120 is moved by the drive system. As the dispenser assembly
104 scans across the platen, the dispenser assembly 104 deposits
feed materials at an appropriate location on the platen 120. The
dispenser assembly 104 can store and dispense two or more different
feed materials. The dispenser assembly includes a first dispenser
104a having a first reservoir 108a to hold first feed material
114a, and a second dispenser 104b having a second reservoir 108b to
hold a second feed material 114b. Release of the first feed
material 114a and second feed material 114b is controlled by a
first gate 112a and a second gate 112b, respectively. Gates 112a
and 112b are controlled independently so that one of the two feed
materials is deposited at a particular location on the platen
120.
[0056] The controller 140 directs the dispenser assembly 104 to
deposit either the first feed material 114a or the second feed
material 114b at locations on the platen according to a printing
pattern that can be stored in non-transitory computer-readable
medium. For example, the printing pattern can be stored as a file,
e.g., a computer aided design (CAD)-compatible file, that is then
read by a processor associated with the controller 140. Electronic
control signals are then sent to the gates 112a and 112b to
dispense the respective feed material when the respective
dispensers 104a and 104b are translated to a position specified by
the CAD-compatible file.
[0057] In some implementations, each dispenser 104a, 104b includes
a plurality of openings through which feed material can be
dispensed. Each opening can have an independently controllable
gate, so that delivery of the feed material through each opening
can be independently controlled.
[0058] In some implementations, the plurality of openings extend
across the width of the platen, e.g., in direction perpendicular to
the direction of travel 106 of the dispensers 104a, 104b. In this
case, in operation, the dispensers 104a, 104b can scan across the
platen 120 in a single sweep in the direction 106. In some
implementations, for alternating layers the dispensers 104a, 104b
can scan across the platen 120 in alternating directions, e.g., a
first sweep in the direction 106 and a second sweep in the opposite
direction.
[0059] Alternatively, e.g., where the plurality of openings do not
extend across the width of the platen, the dispensing system 104
can be configured such that the dispensers 104a, 104b move in two
directions to scan across the platen 120, e.g., a raster scan
across the platen 120, to deliver the material for a layer.
[0060] The gates 112a, 112b of the dispensers 104a, 104b can be
provided by a piezoelectric printhead, and/or one or more of
pneumatic valves, microelectromechanical systems (MEMS) valves,
solenoid valves, or magnetic valves, to control the release of feed
material from the each dispenser 104a, 104b. The dispensers 104a,
104b can deposit a selected feed material at selected locations on
the platen 120. The higher the spatial resolution of the voxels,
the smaller the volume of the voxels and thus the lower the
quantity of feed material that would be dispensed per voxel.
[0061] The feed material can be dry powders of metallic or ceramic
particles, metallic or ceramic powders in liquid suspension, or a
slurry suspension of a material. For example, for a dispenser that
uses a piezoelectric printhead, the feed material would typically
be particles in a liquid suspension. For example, either or both
dispensers 104a, 104b can deliver their powder in a carrier fluid,
e.g. a high vapor pressure carrier, e.g., Isopropyl Alcohol (IPA),
ethanol, or N-Methyl-2-pyrrolidone (NMP), to form the layers of
powder material. The carrier fluid can evaporate prior to the
sintering step for the layer. Alternatively, a dry dispensing
mechanism, e.g., an array of nozzles assisted by ultrasonic
agitation and pressurized inert gas, can be employed to dispense
the first particles.
[0062] Examples of metallic particles include metals, alloys and
intermetallic alloys. Examples of materials for the metallic
particles include titanium, stainless steel, nickel, cobalt,
chromium, vanadium, and various alloys or intermetallic alloys of
these metals. Examples of ceramic materials include metal oxide,
such as ceria, alumina, silica, aluminum nitride, silicon nitride,
silicon carbide, or a combination of these materials.
[0063] Optionally, the system 100 can include a compaction and/or
levelling mechanism to compact and/or smooth the layer of feed
materials deposited over the platen 120. For example, the system
can include a roller or blade that is movable parallel to the
platen surface by a drive system, e.g., a linear actuator. The
height of the roller or blade relative to the platen 120 is set to
compact and/or smooth the outermost layer of feed material. The
roller can rotate as it translates across the platen.
[0064] During manufacturing, layers of feed materials are
progressively deposited and sintered or melted. For example, the
first and second feed materials 114a and 114b are dispensed from
the dispenser assembly 104 to form a first layer 152 that contacts
the platen 120, as shown in FIG. 1B. Subsequently deposited layers
of feed material can form additional layers, e.g., layers 154 and
156, each of which is supported on an underlying layer, e.g., layer
154 and 152, respectively.
[0065] After each layer is deposited, the outermost layer is
processed to cause at least some of the layer to fuse, e.g., by
sintering or by melting and resolidifying.
[0066] The second feed material 114b can have a higher sintering or
melting point than the first feed material 114a. For example, the
temperature difference in melting point between the first feed
material 114a and the second feed material 114b may be greater than
200.degree. C.
[0067] The system 100 includes a heat source 134 configured to
raise the temperature of an entire deposited layer simultaneously.
In operation, the heat source 134 raises the temperature of the
whole outermost layer 156 to a temperature that is above a first
temperature at which the first feed material 114a fuses, but below
above a second temperature at which the second feed material 114b
fuses. Consequently, a deposited cluster of the first feed material
114a can melt and thus fuse together to form fused material 160,
whereas the second feed material 114b remains in loose (e.g.,
powder) form. The heat source 134 can be a radiative heater. For
example, the heat source 134 can be a two-dimensional array of heat
lamps 136.
[0068] The heat source 134 can be triggered after each layer has
been deposited by the dispensing system 104. In contrast to a
point-by-point raster scan, in which the time needed to fuse the
material in an object scales as L.sup.3, the time needed to fuse
the material in the object using system 100 scales with L, the
thickness (i.e., the number of layers) of the object. This permits
a significant increase in throughput, and may make additive
manufacturing economically feasible over a wider range of products
or at larger sizes.
[0069] As illustrated in FIGS. 1A and 1B, the heat source 134 can
be positioned "above" the platen, i.e., on the same side of the
platen 120 on which the feed material is deposited, and spaced away
sufficiently from the platen 120 so that the dispensers 104a, 104b
can pass between the platen 120 and the heat source 134. As shown
in FIGS. 1A and 1B, the array of heat lamps 136 is disposed
directly above the platen 120, and the heat lamps 136 are arranged
in a plane parallel to the surface of the platen 120 with the
individual lamps oriented perpendicular to the platen surface.
However, the heat lamps 136 could be above the platen but partially
or entirely off to the lateral sides of the platen, with the lamps
oriented at angle such that the heat radiation is at a non-zero
angle of incidence on the layer of feed material on the platen.
[0070] In some implementations the heat source 134 could be
positioned "below" the platen, i.e., on the side of the platen 120
opposite the surface on which the feed material is deposited.
However, having the heat source 134 above the platen is
advantageous in that the heat can be delivered primarily to the
outermost layer, e.g., layer 156, rather than transmitting heat to
the platen and underlying layers 152, 154.
[0071] A secondary heat source can be used to raise the temperature
of the layer of feed material(s) to a temperature below the
temperature at which the first feed material fuses. In general, the
secondary heat source applies heat to the outermost layer 156 of
feed material before the heat source 134. For example, the
secondary heat source could be operated continuously, e.g., while
the layer is being deposited. For example, the platen 120 can be
heated by an embedded heater 126 to a base temperature that is
below the melting points of both the first and second feed
materials. As another example, additional heat lamps could provide
the secondary heat source.
[0072] The heat source 134 is triggered to impart sufficient energy
to sinter or melt the first feed material without sintering or
melting the second feed material. In this way, the heat source 134
can be configured to provide a smaller temperature increase to the
deposited material to selectively melt the first feed material.
Transitioning through a small temperature difference can enable
each deposited layer of feed materials to be processed more
quickly. Transitioning through a small temperature difference can
also reduce thermal stress and thus improve quality of the
fabricated object. For example, the base temperature of the platen
120 can be about 500-1700.degree. C., e.g., 1500.degree. C., and
the heat source 134 can be triggered to impart energy to cause a
temperature increase of about 50.degree. C.
[0073] For example, considering the case of titanium, which has a
melting point of 1668.degree. C., heat of fusion of 14.15 kJ/mol, a
molar heat capacity of 25.06 J/mol/K and a density of 4.506
g/cm.sup.3. Assuming the feed material is titanium spheres having a
diameter of 10 microns, the energy needed to raise one titanium
sphere by 50.degree. C. and melt it is .about.0.7 .mu.J. Assuming
heating a square area having sides of 10 cm on the platen 120 for 1
second using the heat lamps each time they are used to melt a layer
having a thickness of a single sphere, the array of heat lamps 136
can have a power rating of at least .about.75 W, assuming all the
energy from the heat lamps is absorbed by the titanium spheres. In
other words, reflection and scattering of the thermal radiation
from the heater lamps have not been taken into account above.
[0074] In contrast, without the base temperature of the platen been
maintained at, for example, 50.degree. C. below the melting point
of the first feed material, the power rating of the array 134 would
have to be at least .about.270 W to raise the temperature of the
first feed material from room temperature to the melting point of
the material and to melt the material.
[0075] Alternatively, the heat source 134 could be used to heat the
platen 120 to the base temperature, and the embedded heater 126
could be triggered to impart sufficient energy to melt the first
feed material without melting the second feed material. However,
having the heat source 134 be triggered is advantageous in that the
change in temperature can occur primarily in the outermost layer,
e.g., layer 156, rather than having to propagate through the platen
and underlying layers 152, 154.
[0076] As shown in FIG. 1B, the platen 120 can include side walls
122 and 124 that are each heated by heaters 128 and 130,
respectively.
[0077] In some implementations, rather than the heat source 134 can
be configured to raise the temperature of a generally linear region
that extends across the platen. The heated region can be scanned
linearly across the platen, e.g., in a direction perpendicular to
the primary axis of the linear region (i.e., assuming the length is
greater than the width, the primary axis is the length direction).
In such a system, the time needed to fuse the material in an object
scales as L.sup.2 rather than L.sup.3. The heat source 134 can
include a laser beam that is appropriately shaped, for example,
using cylindrical lenses, to achieve a line shape. When a line of
laser beam is used, the laser beam would be scanned across the
platen to cover an entire layer of deposited feed material.
Alternatively or in addition, the heat source 134 could include a
linear array of heat lamps.
[0078] Relative motion of the linear region heated by the heat
source 134 across the outermost layer of feed material can be
accomplished by holding the platen 120 fixed while the heat source
134 moves, e.g., with a linear actuator, by holding the heat source
134 stationary while the platen 120 moves, e.g., with a linear
actuator, or by scanning the beam generated by the heat source,
e.g., by a mirror galvanometer.
[0079] In operation, after each layer has been deposited and heat
treated, the platen 120 is lowered by an amount substantially equal
to the thickness of layer. Then the dispenser assembly 104, which
does not need to be translated in the vertical direction, scans
horizontally across the platen to deposit a new layer that overlays
the previously deposited layer, and the new layer can then be heat
treated to fuse the first feed material. This process can be
repeated until the full 3-dimensional object is fabricated. The
fused material 160 derived by heat treatment of the first feed
material provides the additively manufactured object, and the loose
second feed material 114b can be removed and cleaned off after the
object is formed.
[0080] As noted above, the first feed material 114a and the second
feed material 114b are deposited in each layer by the dispenser
assembly 104 in a pattern stored in a 3D drawing computer program
controlled by the controller 140. For some implementations, the
controller 140 controls the dispenser assembly 104 so that each
voxel in a layer is filled by one of the feed materials, e.g.,
there are no empty voxels. For example, assuming that two feed
materials are used, any voxel in to which the first dispenser 104a
does not deliver the first feed material 114a, the second dispenser
104b will deliver the second feed material 114b. This can ensure
that each voxel in subsequently dispensed layers will be supported
by an underlying material.
[0081] Using a heat source that raises the temperature of the
entire layer simultaneously, e.g., 2-dimensional array of heater
lamps, allows layerwise heating of the feed materials, speeding up
the fabrication process. In addition, the entire layer of feed
material is exposed to the heat from the array of heater lamps at
the same time, which can provide better control to the thermal
history across the layer. In particular, the number of fluctuations
of temperature experienced by a particular point in the layer can
be reduced. As a result, better control of grain sizes of the fused
material can be achieved.
[0082] As shown in FIG. 2A, a dispenser 204, which could be used
for the dispenser 104a and/or 104b, may be a single point dispenser
and the dispenser would be translated across the x and y direction
of the platen 210 to deposit a complete layer of feed material 206,
which can be feed material 114a and/or feed material 114b, on the
platen 210.
[0083] Alternatively, as shown in FIG. 2B, a dispenser 214, which
could be used for the dispenser 104a and/or 104b, can be a line
dispenser that extends across the width of the platen. For example,
the dispenser 214 could include a linear array of individually
controllable openings, e.g., nozzles. The dispenser 214 can be
translated only along one dimension to deposit a complete layer of
feed material on the platen.
[0084] Alternatively, as shown in FIG. 1C, a dispenser 224, which
could be used for the dispenser 104a and/or 104b, includes a
two-dimensional array of individually controllable openings, e.g.,
nozzles. For example, the dispenser 224 can be a large area voxel
nozzle print (LAVoN). LAVoN 224 allows a complete two dimensional
layer of feed material to be deposited simultaneously. LAVoN 224
may be a dense grid of through-silicon via (TSV) 228 formed in bulk
silicon 226. Each TSV 228 can be controlled by a piezoelectric gate
230 that closes an exit opening of a particular 228 when an
appropriate voltage is applied such that the feed material 206 is
retained within the TSV. When a different voltage is applied to the
TSV 228, the piezoelectric gate 230 can open an exit opening of a
particular TSV 228, allowing feed material to be deposited on a
platen. Each of the TSV 228 in the LAVoN 224 is individually
accessed by control signals produced from a controller based on a
CAD-file that defines the fabricated object. LAVoN 224 can be used
to deposit a single feed material only. In such a case, no feed
material is deposited at regions of void in the fabricated object
or in regions beyond the fabricate object. Alternatively, each
"pixel" of the LAVoN 224 can be served by two TSV 228, each holding
one of the two types of feed material. When the TSV 228 for one
feed material is turned on, the TSV 228 for the other feed material
at that pixel is turned off. The embodiments shown in FIGS. 2B-2D
would speed up the deposition process of the feed material on the
platen.
[0085] As an alternative or in addition to the radiative and/or
conductive heat sources described for the implementations of FIGS.
1A and 1B, plasma based systems can also be used to achieve
layer-wise fusing of feed materials. As shown in FIG. 3A, an
additive manufacturing system 300 is similar to the additive
manufacturing system 100 of FIGS. 1A and 1B, but includes a plasma
generation system 302, which provides a plasma source. The additive
manufacturing system 300 includes chamber walls 304 that define the
chamber 103.
[0086] The plasma generation system 302 includes an electrode 310,
i.e., a first electrode. The electrode 310 can be a conductive
layer on or in the platen 120. This permits the electrode 310 to
can be translated vertically, similar to the piston 132 in FIGS. 1A
and 1B. The electrode 310 can serve as the anode.
[0087] The additive manufacturing system 300 also include a
counter-electrode 312, i.e., as second electrode. The
counter-electrode 312 can serve as an anode. Although FIG. 3A
illustrates the counter-electrode 312 as a plate suspended in the
chamber 103, the counter-electrode 312 could have other shapes or
be provided by portions of the chamber walls 304.
[0088] At least one of the electrode 310 and/or counter-electrode
312 is connected to an RF power supply, e.g., an RF voltage source.
For example, the electrode 310 can be connected to an RF power
supply 320 and the counter-electrode can be connected to an RF
power supply 322. In some implementations, one of the electrode 310
or counter-electrode 312 is connected to an RF power supply and the
other of the electrode 310 or counter-electrode 312 is grounded or
connected to an impedance matching network.
[0089] By application of an RF signal of appropriate power and
frequency, a plasma 340 forms in a discharge space 342 between the
electrode 310 and the counter-electrode 312. A plasma is an
electrically neutral medium of positive and negative particles
(i.e. the overall charge of a plasma is roughly zero). The plasma
340 is depicted as elliptical only for illustrative purposes. In
general, the plasma fills the region between the electrode 310 and
the counter-electrode 312, excluding a "dead zone" near the anode
surface.
[0090] Optionally, the system 300 can include a magnet assembly 350
which can create a magnetic field of, for example, 50 Gauss to 400
Gauss. The magnet assembly 350 can include a permanent magnet in
the platen 120, e.g., located near a top surface 314 of the platen
120. Alternatively, the magnet assembly can include an
electromagnet, e.g., an antenna coil wound about the exterior
surface of a dielectric (e.g., quartz) portion of the walls 304 of
the vacuum chamber 103. An RF current is passed through the antenna
coil. When operated in a resonance mode with the applied RF power,
the antenna coil generates an axial magnetic field within the
chamber 103. The magnetic field can confine charged particles,
e.g., negative particles such as electrons, to a helical
motion.
[0091] The chamber 103 defined by the chamber walls 304 can be
enclosed in the housing 102. The chamber walls 304 can, for
example, allow a vacuum environment to be maintained in a chamber
103 inside the housing 102. A vacuum pump in the housing 102 can be
connected to the chamber 103 by a vacuum vent 306 to exhaust gases
from within the chamber 103. Process gases, such as argon and
helium, which are non-reactive, can be introduced into the chamber
103 via a gas inlet 308. Depending on the processes, different
gases can be introduced to the chamber 103. For example, oxygen can
be introduced to cause chemical reactions.
[0092] A dispenser assembly 104, similar to the one shown in FIGS.
1A and 1B, or in alternative forms as those shown in FIGS. 2A-2C,
can be used to deposit feed materials 114a and 114b over the platen
120. The controller 140 similarly controls a drive system (not
shown), e.g., a linear actuator, connected to the dispenser
assembly 104. The drive system is configured such that, during
operation, the dispenser assembly is movable back and forth
parallel to the top surface of the platen 120.
[0093] The left side of FIG. 3B shows a profile 362 (exaggerated,
not to scale) of a particle 360 of the feed material 114a. The
particle 360 is in point contact with the top surface 314 of the
electrode 310 or a previously deposited conductive underlying layer
that is on the platen 120. In short, with "point contact", due to
surface roughness and/or curvature of the particle, only a limited
surface area of the particle contacts the top surface 314.
[0094] Without being limited to any particular theory, upon
applying RF power on the electrode 310 to produce the plasma 340,
parts of the particle 360 that are not in direct contact with the
top surface 314 can experience a large voltage, e.g., due to plasma
bias. The feed material need not be non-metallic or non-conductive
to experience the large voltage due to the plasma bias. In the case
of a metallic particle conductivity decreases as cross-section
decreases. Thus, the point contact basically acts as a resistor for
a metallic particle.
[0095] Again without being limited to any particular theory,
localized arcing across a gap 366 between the particle 360 and
either the electrode 310 or underlying conductive layer can cause
fusing, e.g., melting or sintering to occur. In general, a larger
gap causes a smaller the amount of arcing, for a given voltage
differential between the cathode and the particle. Even though the
arcing/melting is localized to regions of the particles that are
not in direct contact with the cathode, the heat generated by the
arcing is sufficient to fuse the material, e.g., by melting the
entire particle 360 or sintering of the particle 360 to adjacent
particles.
[0096] In general, there exists enough curvature (in some (e.g.,
all) of the particles of the first feed material 114a for arcing to
occur. Thus, the particles need not be oriented to be deposited on
the cathode in a particular way. The second feed material 114b,
which is not fused in the part to be additively manufactured, has a
much higher melting point such that even arcing in the plasma would
not lead to melting or fusing of the first feed material 114a. For
example, the temperature difference in melting point between the
first feed material 114a and the second feed material 114b may be
greater than 200.degree. C.
[0097] The right side of FIG. 3B shows a profile 363 of the
particle 360 after it has been fused/melting by localized arcing
into a fused particle 361. After fusing, gaps between the particle
361 and the top surface 314 are reduced (e.g., eliminated) to such
an extent that local arcing no longer occurs in the fused particle
361.
[0098] It should be understood that the above explanation is not
limiting. It may be that heating of the layer of feed material is
partially or entire due to heat transfer from the plasma, e.g., due
to kinetic bombardment.
[0099] As described in reference to FIGS. 1A and 1B, the dispenser
assembly 104 deposits either the first feed material 114a or the
second feed material 114b at locations over the platen 120
according to a printing pattern that can be stored as a computer
aided design (CAD)-compatible file that is then read by a computer
associated with the controller 140.
[0100] While FIG. 3B shows only a single particle on the electrode
310 for illustration purposes, in practice, an entire layer of feed
material is deposited over the platen 120 before the plasma 340 is
formed in the system 300. For example, the plasma formation may be
timed to a drive pulse 370, as shown in FIG. 3C, that is applied to
control a supply of power to the electrode 310 and/or the
counter-electrode 330.
[0101] During an on-state 372 of the drive pulse 370, the plasma
340 is formed between the electrode and the counter-electrode 330,
and localized fusing/melting occurs in the deposited first feed
material 114a. During the off-state 374 of the drive pulse 370, the
plasma 340 is not formed and the dispenser assembly 104 can be
translated across the platen 120 to deposit a new layer of feed
material to be processed by the plasma 340. The on-state and the
off-state can last, for example, 0.5 seconds.
[0102] Similar to the system 100, the system 300 also processes the
feed materials 114a and 114b one layer at a time, allowing
processing time to scale with L. When a new layer of feed material
is deposited on top of a layer of feed material that has been
fused/melted, the localized arcing/melting that occurs on the top
layer of feed material does not influence the underlying processed
or fused/melted layers of feed material. The platen 120 can be
lowered after each layer has been processed and fused such that the
dispenser assembly 104 need not be translated vertically.
[0103] Operating the system 300 under a vacuum environment may
provide quality control for the material formed from processes
occurring in the system 300. Nonetheless, in some implementations
the plasma 340 can also be produced under atmospheric pressure.
[0104] A higher frequency (e.g., more than 50 MHz) drive voltage
can be applied to one of the electrodes (either the cathode or the
anode), while a lower frequency (e.g., less than 20 MHz) bias
voltage can be applied to the other electrode. In general, the
higher frequency signal creates the flux of plasma. A higher
frequency RF drive voltage creates a higher flux (i.e., more ions
and electrons in the plasma). The lower frequency RF bias voltage
controls the energy of the ions in the plasma. At low enough
frequencies (e.g., 2 MHz), the bias signal can cause the ions in
the plasma to have enough energy to vaporize a feed material (e.g.,
aluminum powder) that is deposited on a substrate (e.g., silicon
wafer). In contrast, at a higher frequency bias signal (e.g., 13
MHz), melting of the feed material can occur. Varying the RF
frequency and point of application would cause different melting
performance of the feed material. Melting performance can determine
the recrystallization of the feed material, which could lead to
different stresses within the metal and different relaxation
behavior.
[0105] The use of plasma to cause a temperature jump in a layer of
feed material also enables layer characteristics of the feed
material to be easily controlled. For example, the layer of feed
material can be doped by selectively implanting ions from the
plasma. The doping concentration can be varied layer by layer. The
implantation of ions can help release point stress in the layer of
feed material. Examples of dopants include phosphorous.
[0106] Indeed, the plasma can be biased such that gaps between the
powder particles of the feed material and the electrode cause a
sufficiently large voltage to be developed on the powder, causing
electron or ion bombardment on the feed material. The electrons or
ions used in the bombardment can come from the plasma, and be
accelerated to the feed material when either a DC or an AC bias is
applied on the feed material. Bombardment can be used to treat a
layer, to etch material, to chemically alter (e.g., in reactive ion
etch) the feed material, to dope the feed material (e.g., to add a
nitride layer), or be used for surface treatment.
[0107] Referring to either FIGS. 1A or 3A, the controller 140 of
system 100 or 300 is connected to the various components of the
system, e.g., actuators, valves, and voltage sources, to generate
signals to those components and coordinate the operation and cause
the system to carry out the various functional operations or
sequence of steps described above. The controller can be
implemented in digital electronic circuitry, or in computer
software, firmware, or hardware. For example, the controller can
include a processor to execute a computer program as stored in a
computer program product, e.g., in a non-transitory machine
readable storage medium. Such a computer program (also known as a
program, software, software application, or code) can be written in
any form of programming language, including compiled or interpreted
languages, and it can be deployed in any form, including as a
standalone program or as a module, component, subroutine, or other
unit suitable for use in a computing environment.
[0108] As noted above, the controller 140 can include
non-transitory computer readable medium to store a data object,
e.g., a computer aided design (CAD)-compatible file, that
identifies the pattern in which the feed material should be
deposited for each layer. For example, the data object could be a
STL-formatted file, a 3D Manufacturing Format (3MF) file, or an
Additive Manufacturing File Format (AMF) file. For example, the
controller could receive the data object from a remote computer. A
processor in the controller 140, e.g., as controlled by firmware or
software, can interpret the data object received from the computer
to generate the set of signals necessary to control the components
of the system to print the specified pattern for each layer.
[0109] The processing conditions for additive manufacturing of
metals and ceramics are significantly different than those for
plastics. For example, in general, metals and ceramics require
significantly higher processing temperatures. For example, metals
need to processed at temperature on the order of 400.degree. C. or
higher, e.g., 700.degree. C. for aluminum. In addition, processing
of metal should occur in vacuum environment, e.g., to prevent
oxidation. Thus 3D printing techniques for plastic may not be
applicable to metal or ceramic processing and equipment may not be
equivalent. In addition, the fabrication conditions for large
scale-industrial parts can be significantly more stringent.
[0110] However, some techniques described here could be applicable
to plastic powders. Examples of plastic powders include nylon,
acrylonitrile butadiene styrene (ABS), polyurethane, acrylate,
epoxy, polyetherimide, polyetheretherketone (PEEK),
polyetherketoneketone (PEKK), polystyrene or polyamides.
[0111] Certain features that are described in the context of
separate embodiments can also be implemented in combination in a
single embodiment, and conversely, various features that are
described in the context of a single embodiment can also be
implemented singly without the other features of that
embodiment.
[0112] For example, although the description above has focused on
the use of multiple feed materials having different temperatures,
the technique of raising the temperature of the entire layer or
raising the temperature of a linear region that scans across the
platen, either by radiated heat or plasma, can be applied even if
just a single feed material is being used in each layer. In this
case, only a single dispenser assembly is needed. In addition, the
controller can cause the dispenser assembly 104 to deliver the
single feed material to desired voxels over the platen 120. The
object being fabricated can be subject to certain constraints,
e.g., each voxel of feed material in a new layer would be deposited
only over voxels in the underlying layer where material was
delivered.
[0113] As another example, although the description above has
focused on raising the temperature of the entire layer or raising
the temperature of a linear region that scans across the platen,
the technique of dispensing multiple feed materials could be used
with a heat source that scans across the layer of material to
controllably apply heat on a voxel-by-voxel basis. For example, the
heat source can be a laser that generates a laser beam that scans
across the platen and has an intensity that is modulated to control
which voxels are fused. Relative motion of the region heated by the
heat source can be provided by holding the platen 120 fixed while
the heat source 134 moves, e.g., with a pair of linear actuators,
by holding the heat source 134 stationary while the platen 120
moves, e.g., with a pair of linear actuators, or by scanning the
beam generated by the heat source, e.g., by a mirror
galvanometer.
[0114] As another example, although the description above has
focused on applying plasma to the entire layer of feed material,
plasma could be generated in an area that is smaller than the layer
of feed material. For example, the area in which the plasma is
generated can be sized to control fusing of a region the layer of
feed material, e.g., a single voxel, a region of multiple voxels
that does not span the platen, or an elongated region that spans
the width of the platen. This region can be scanned across the
platen. The region affected by the plasma can be controlled by
appropriate configuration of the electrodes, e.g., a
counter-electrode of appropriate size can be placed in proximity to
the platen. Where voxel-by-voxel control is possible, a continuous
layer of a single feed material can be dispensed over the platen,
and the plasma can be used to determine whether a particular voxel
is fused. Relative motion of the volume in which plasma is
generated can be provided by holding the platen 120 fixed while the
counter-electrode moves, e.g., with a pair of linear actuators, or
by holding the counter-electrode stationary while the platen 120
moves, e.g., with a pair of linear actuators.
[0115] As another example, the radiative heat source 134, e.g., an
array of heat lamps 135, and the plasma generation system 302 have
been described above as part of separate implementations, some
implementations can include both the radiative heat source 134 and
the plasma generation system 302.
[0116] A number of implementations have been described.
Nevertheless, it will be understood that various modifications may
be made. Accordingly, other implementations are within the scope of
the following claims.
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