U.S. patent application number 16/900884 was filed with the patent office on 2020-12-03 for blue laser metal additive manufacturing system.
This patent application is currently assigned to Nuburu, Inc.. The applicant listed for this patent is Nuburu, Inc.. Invention is credited to Eric Boese, Mathew Finuf, Ian Lee, Jean Michel Pelaprat, Mark S. Zediker.
Application Number | 20200376764 16/900884 |
Document ID | / |
Family ID | 1000005022816 |
Filed Date | 2020-12-03 |
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United States Patent
Application |
20200376764 |
Kind Code |
A1 |
Zediker; Mark S. ; et
al. |
December 3, 2020 |
Blue Laser Metal Additive Manufacturing System
Abstract
A high-resolution additive manufacturing system based on a
parallel printing method using a spatial light modulator. A method
and system for additive manufacturing using a DMD in the laser beam
path. The use of a pre-heat laser beam in combination with a build
laser beam having a DMD along the build laser beam path.
Inventors: |
Zediker; Mark S.; (Castle
Rock, CO) ; Lee; Ian; (Highlands Ranch, CO) ;
Pelaprat; Jean Michel; (Saratoga, CA) ; Boese;
Eric; (Centennial, CO) ; Finuf; Mathew;
(Castle Rock, CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nuburu, Inc. |
Centennial |
CO |
US |
|
|
Assignee: |
Nuburu, Inc.
Centennial
CO
|
Family ID: |
1000005022816 |
Appl. No.: |
16/900884 |
Filed: |
June 13, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16550216 |
Aug 24, 2019 |
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16900884 |
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15581494 |
Apr 28, 2017 |
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16550216 |
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62722198 |
Aug 24, 2018 |
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62726233 |
Sep 1, 2018 |
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62329786 |
Apr 29, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B23K 26/123 20130101;
B22F 3/1055 20130101; B29C 64/153 20170801; B23K 26/703 20151001;
B23K 26/0643 20130101; B22F 2003/1056 20130101; B33Y 30/00
20141201; B29C 64/268 20170801; B23K 26/127 20130101 |
International
Class: |
B29C 64/268 20060101
B29C064/268; B23K 26/12 20060101 B23K026/12; B23K 26/70 20060101
B23K026/70; B22F 3/105 20060101 B22F003/105; B29C 64/153 20060101
B29C064/153; B33Y 30/00 20060101 B33Y030/00; B23K 26/06 20060101
B23K026/06 |
Claims
1-124. (canceled)
125. An additive manufacturing system for metals comprising: a
laser; a spatial light modulator in optical communication with the
laser; wherein the spatial light modulator is configured to form a
pattern on a powder metal layer that is fused to the layer below; a
gantry system to step and repeat an image across the powder metal
layer; a motion control system; an elevator to displace a part down
after the powder metal layer is fused; a powder distribution system
that can both spread the powder and compact it before fusing; a
controlled atmosphere build chamber; and a means for cooling the
spatial light modulator.
126. The system of claim 125, wherein the laser provides a laser
beam having a wavelength selected from the group consisting of blue
wavelengths and green wavelengths.
127. The system of claim 126, wherein the laser has a power from
about 1 kW to about 20 kW; and the pattern on the powder metal
layer has a peak power density of from about 2 kW/cm.sup.2 to about
5 kW/cm.sup.2.
128. The system of claim 127, wherein the laser has a bandwidth
selected from the group consisting of about 5 nm, about 10 nm and
about 20 nm.
129. The system of claim 125, comprising a beam dump.
130. The system of claim 125, comprising a means to provide a gray
scale pattern.
131. An additive manufacturing system for forming metal objects
from metal powders, the system comprising: a. a laser source to
provide a build laser beam along a build laser beam path; b. a
means for heating a layer of a metal powder; c. a digital
micro-mirror device (DMD) having an average rated power density; d.
the DMD on the build laser beam path; whereby the build laser beam
is directed onto the DMD, wherein the DMD is configured to create a
2-D image pattern that is reflected from the DMD along the build
laser beam path to an optical assembly; e. the optical assembly
configured to direct the 2-D image pattern to a surface of a layer
of metal powder; wherein the 2-D image pattern has a peak power
density at the surface of the layer of metal powder; f. wherein the
peak power density is greater than the average rated power density
for the DMD.
132. The system of claim 131, wherein the means for heating is
selected from the group consisting of an electric heater, a radiant
heater, an IR heater and a laser beam.
133. The system of claim 132, comprising an homogenizer on the
build laser beam path positioned between the laser source and the
DMD.
134. The system of claim 131, wherein the peak power density is at
least 500.times. greater than a maximum average rated power density
of the DMD.
135. The systems of claims 131, comprising a means to provide a
gray scale pattern.
136. The system of claim 131, comprising a beam dump in optical
communication with the DMD.
137. The system of claim 131, wherein the DMD is cooled.
138. The system of claim 137, wherein the DMD is cooled by a means
selected from the group consisting of air cooled, water cooled,
micro-channel cooler, and a Peltier cooler.
139. The system of claim 132, wherein the metal powder forms a bed
of metal powder.
140. The system of claim 132, wherein the laser beam has a wave
length select from the group consisting of blue and green.
141. The system of claim 132, wherein the laser beam has a
wavelength selected from the group consisting of about 450 nm,
about 460 nm, about 515 nm, about 532 nm and about 550 nm.
142. The system of claim 132, wherein the laser source has a power
of about 150 W to about 20 kW.
143. The system of claim 132, wherein the peak power density is
from about 2 kW/cm.sup.2 to about 5 kW/cm.sup.2.
144. The system of claim 132, wherein the system has a resolution
of about 0.5 .mu.m to about 10 .mu.m.
145. An additive manufacturing system for forming metal objects
from metal powders, the system comprising: a. a laser source to
provide a laser beam along a laser beam path; b. a digital
micro-mirror device (DMD) having an average rated power density; c.
the DMD on the laser beam path; whereby the laser beam is directed
onto the DMD, wherein the DMD is configured to create a 2-D image
pattern that is reflected from the DMD along the laser beam path to
a surface of a bed of metal powder; and, d. the 2-D image having a
wavelength and a power density; whereby the 2-D image is configured
to conduction mode weld the bed of metal powder.
146. The system of claim 145, wherein a peak power density of the
2-D image is from about 2 kW/cm.sup.2 to about 5 kW/cm.sup.2.
147. The system of claim 146, wherein a peak power density of the
2-D image is at least from 10.times. to 1000.times. greater than an
average rated power density for the DMD.
148. The system of claim 146, wherein a peak power density level of
the 2-D image on the metal powder is at least 500.times. greater
than a maximum average power density level of the DMD
149. The system of claim 148, comprising a means for cooling the
DMD.
150. The system of claim 149, wherein the wavelength is selected
from the group consisting of blue and green.
151. The system of claim 150, wherein the metal powder comprises a
material selected from the group consisting of brass, brass alloys,
titanium, titanium alloys, steel, steel alloys, stainless steel,
stainless steel alloys, nickel, nickel alloys, gold, gold alloys,
silver, silver alloys, platinum, platinum alloys, copper, copper
alloys, anodized aluminum, anodized aluminum alloys, aluminum and
aluminum alloys.
152. The system of claim 151, wherein the conduction mode weld is
spherical.
153. The system of claim 150, wherein the laser beam has a
wavelength selected from the group consisting of about 450 nm,
about 460 nm, about 515 nm, about 532 nm and about 550 nm.
154. An additive manufacturing system for forming metal objects
from metal powders, the system comprising: a. a laser source to
provide a build laser beam along a build laser beam path; wherein
the build laser beam has a wavelength selected from the group
consisting of blue and green; b. an homogenizer on the build laser
beam path; c. a digital micro-mirror device (DMD) on the build
laser beam path; d. a means for cooling the DMD; e. a beam dump; f.
whereby the DMD is configured to create a 2-D image pattern on a
surface layer of a metal powder; g. whereby the 2-D image pattern
has a sufficient power density to fuse the surface layer of the
metal powder to a layer below the surface layer; and, h. wherein
the metal powder comprises a material selected from the group
consisting of brass, brass alloys, titanium, titanium alloys,
steel, steel alloys, stainless steel, stainless steel alloys,
nickel, nickel alloys, gold, gold alloys, silver, silver alloys,
platinum, platinum alloys, copper, copper alloys, anodized
aluminum, anodized aluminum alloys, aluminum and aluminum alloys.
Description
[0001] This application: (i) claims under 35 U.S.C. .sctn.
119(e)(1) the benefit of the filing date of, and claims the benefit
of priority to, U.S. provisional application Ser. No. 62/722,198
filed Aug. 24, 2018; (ii) claims under 35 U.S.C. .sctn. 119(e)(1)
the benefit of the filing date of, and claims the benefit of
priority to, U.S. provisional application Ser. No. 62/726,233 filed
Sep. 1, 2018; and, (iii) is a continuation-in-part of U.S. patent
application Ser. No. 15/581,494, which claims under 35 U.S.C.
.sctn. 119(e)(1) the benefit of the filing date of U.S. provisional
application Ser. No. 62/329,786 filed Apr. 29, 2016, the entire
disclosure of each of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present inventions relate to laser processing of
materials and in particular laser building of materials including
laser additive manufacturing processes using laser beams having
wavelengths from about 350 nm to about 700 nm.
[0003] Infrared red (IR) based (e.g., having wavelengths greater
than 700 nm, and in particular wavelengths greater than 1,000 nm)
additive manufacturing systems suffer from, among other things, two
short comings, which limit both the build volume and the build
speed. In these IR systems the build volume is limited by the
finite size of the scanning systems and the spot that can be
created for a given focal length collimator and f-theta lens. For
example, in such prior IR systems, when using a 14 mm focal length
collimator and a 500 mm F-theta focal length lens the spot size is
on the order of 350 .mu.m for a diffraction limited IR laser beam.
This gives an addressable foot print on the raw build material,
e.g., a powder bed, of approximately 85 mm.times.85 mm, which in
turn creates or establishes the finite limitation on the build
volume for that given resolution (e.g., spot size). The second
limitation on the build speed for IR laser systems is the
absorption of the laser beam by the materials. While originally,
most raw build materials had a modest to low reflectivity for
wavelengths in the infrared spectrum, as additivity manufacturing
started to use metals, such as gold, silver, platinum, copper and
aluminum and alloys thereof, which materials have high and very
high IR reflectivity, problems were encountered with using these
high reflective IR types of build materials in IR additive
manufacturing. As a consequence, the coupling of the infrared laser
energy into the raw build materials, e.g., powder bed or particles,
is limited with a significant portion of the energy being reflected
away, backward or deeper into the raw build material. These
limitations are in a way further tied or linked together,
compounding the problems and deficiencies of IR additive systems.
Thus, the finite penetration depth of the Infrared laser light
determines the optimum layer thickness and as a consequence, limits
the resolution of the process. Thus, IR laser systems, because of
their reflectivity to the typical raw build material have limited
layer thicknesses and thus limited resolution.
[0004] As used herein, unless expressly stated otherwise, "UV",
"ultra violet", "UV spectrum", and "UV portion of the spectrum" and
similar terms, should be given their broadest meaning, and would
include light in the wavelengths of from about 10 nm to about 400
nm, and from 10 nm to 400 nm.
[0005] As used herein, unless expressly stated otherwise, the terms
"visible", "visible spectrum", and "visible portion of the
spectrum" and similar terms, should be given their broadest
meaning, and would include light in the wavelengths of from about
380 nm to about 750 nm, and 400 nm to 700 nm.
[0006] As used herein, unless expressly stated otherwise, the terms
"blue laser beams", "blue lasers" and "blue" should be given their
broadest meaning, and in general refer to systems that provide
laser beams, laser beams, laser sources, e.g., lasers and diodes
lasers, that provide, e.g., propagate, a laser beam, or light
having a wavelength from 400 nm (nanometer) to 500 nm, and about
400 nm to about 500 nm. Blue lasers include wavelengths of 450 nm,
of about 450 nm, of 460 nm, of about 460 nm. Blue lasers can have
bandwidths of from about 10 pm (picometer) to about 10 nm, about 5
nm, about 10 nm and about 20 nm, as well as greater and smaller
values.
[0007] As used herein, unless expressly stated otherwise, the terms
"green laser beams", "green lasers" and "green" should be given
their broadest meaning, and in general refer to systems that
provide laser beams, laser beams, laser sources, e.g., lasers and
diodes lasers, that provide, e.g., propagate, a laser beam, or
light having a wavelength from 500 nm to 575 nm, about 500 nm to
about 575 nm. Green lasers include wavelengths of 515 nm, of about
515 nm, of 532 nm, about 532 nm, of 550 nm, and of about 550 nm.
Green lasers can have bandwidths of from about 10 pm to 10 nm,
about 5 nm, about 10 nm and about 20 nm, as well as greater and
smaller values.
[0008] Generally, the term "about" and the symbol ".about." as used
herein, unless specified otherwise, is meant to encompass a
variance or range of .+-.10%, the experimental or instrument error
associated with obtaining the stated value, and preferably the
larger of these.
[0009] As used herein, unless stated otherwise, room temperature is
25.degree. C. And, standard ambient temperature and pressure is
25.degree. C. and 1 atmosphere. Unless expressly stated otherwise
all tests, test results, physical properties, and values that are
temperature dependent, pressure dependent, or both, are provided at
standard ambient temperature and pressure, this would include
viscosities.
[0010] As used herein unless specified otherwise, the recitation of
ranges of values herein is merely intended to serve as a shorthand
method of referring individually to each separate value falling
within the range. Unless otherwise indicated herein, each
individual value within a range is incorporated into the
specification as if it were individually recited herein.
[0011] Typically, a method employed today in additive manufacturing
is the use of an infrared laser and a galvanometer to scan the
laser beam across the surface of a powder bed in a predetermined
pattern. The IR laser beam is of sufficient intensity to create a
keyhole welding process that melts and fuses the liquified powder
to the lower layer or substrate. This approach has several
limitations that determines the speed of the process. For example,
a single laser beam is used to scan the surface and the build rate
is limited by the maximum scanning speed of the galvanometers (7
m/sec). Manufactures strongly embrace IR technology, and typically
believe that it is the only viable wavelength, thus they are
working, but with limited success, to overcome this limitation by
integrating two or more IR laser/galvanometers into a system, where
the two can work in conjunction to build a single part or they can
work independently to build parts in parallel. These efforts are
aimed at improving the throughput of the additive manufacturing
systems, but have been focused solely on IR and have been of
limited success, not meeting the long felt need for improved
additive manufacturing.
[0012] An example of another limitation in IR processing is the
finite volume that can be addressed by the IR laser/galvanometer
system. In a stationary head system the build volume is defined by
the focal length of the f-theta lens, the scanning angle of the
galvanometer, the wavelength of the IR laser and the beam quality
of the infrared laser. For example, with a 500 mm F-theta lens the
IR laser creates a spot size on the order of 50 .mu.m for a
diffraction limited infrared laser. If the laser beam is operating
at 100 Watts optical power, then the intensity of the beam is
greater than the intensity required to initiate a keyhole welding
mode. The keyhole welding mode creates a plume of vaporized
material that must be removed out of the path of the laser beam by
a cross jet otherwise the laser beam is scattered and absorbed by
the vaporized metal. In addition, because the keyhole mode of
welding relies on creating a hole in the liquid metal surface that
is maintained by the vapor pressure of the vaporized metal,
material other than vaporized metal can be ejected from the
keyhole. This material is referred to as spatter and results in
molten materials being deposited elsewhere on the build plane that
can lead to defects in the final part. While the manufactures of
additive manufacturing systems have had some limited success in
developing rapid prototyping machines, they have failed to meet the
long felt need, and achieve the requirements needed to produce
commercial or actual parts in volume. To accomplish this a
breakthrough in the method of patterning the parts, which prior to
the present inventions the art has not achieved.
[0013] In general, a problem and failing with IR processing and
systems is the requirement or need to fuse the powder in a keyhole
welding mode. This can be typically because of the use of a single
beam to process the powder. If the laser beam is operating at 100
Watts optical power, then the intensity of the beam is greater than
the intensity required to initiate a keyhole welding mode. The
keyhole welding mode creates a plume of vaporized material that
must be removed out of the path of the laser beam by a cross jet
otherwise the laser beam is scattered and absorbed by the vaporized
metal. In addition, because the keyhole mode of welding relies on
creating a hole in the liquid metal surface that is maintained by
the vapor pressure of the vaporized metal, material such as the
vaporized metal can be ejected from the keyhole. This material is
referred to as spatter and results in molten materials being
deposited elsewhere on the build plane that can lead to defects in
the final part.
[0014] Recent work by Lawrence Livermore National Laboratories
using an Optically Activated Light Valve (OALV) has been attempted
to address these IR limitations. The OALV is a high-power spatial
light modulator that is used to create a light pattern using high
power lasers. While the pattern on the OALV is created with a blue
LED or laser source from a projector, the output power from the
four laser diode arrays are transmitted through the spatial light
modulator and used to heat the image to the melting point and a
Q-switched IR laser is required to initiate a keyhole weld. The IR
laser is used in the keyhole mode to initiate the weld, especially
when fusing copper or aluminum materials, and is generally required
for these materials. This keyhole weld process typically creates
spatter, porosity in the part, as well as high surface roughness.
Thus, the OALV systems as do typical IR systems does not eliminate
the adverse effects of keyhole initiation of the building process.
While it would be better to completely avoid the keyhole welding
step, the art has failed to overcome this problem and has not
provided this solution. This failure has primarily occurred because
at the IR wavelengths the absorption properties of many metals are
so low that a high peak power laser is necessary to initiate the
process. Since the OALV is only transparent in the IR region of the
spectrum, it is not feasible to build, or use this type of system
using a visible laser source as the high energy light source. The
cost of the components in this system are very high especially the
OALV which is a custom unit.
[0015] Prior metal based additive manufacturing machines are very
limited in that they are either based on a binder being sprayed
into a powder bed followed by a consolidation step at high
temperatures, or a high-power single mode laser beam scanned over
the powder bed by a galvanometer system at high speeds. Both of
these systems have significant fallings that the art has been
unable to overcome. The first system is capable of high volume
manufacturing of parts with loose tolerances due to the shrinkage
of the parts during the consolidation process. The second process
is limited in build speed by the scan speeds of the galvanometer
limiting the maximum power level laser that can be used and
consequently, the build rate. Builders of scanning based additive
manufacturing systems have worked to overcome this limitation by
building machines with multiple scan heads and laser systems, which
has not provided an adequate solution to these problems. This does
indeed increase the throughput, but the scaling law is linear, in
other words a system with two laser scanners can only build twice
as many parts as a system with one scanner or build a single part
twice as fast. Thus, there is a need for a high throughput,
laser-based metal additive manufacturing system that does not
suffer from the limitations of the currently available systems.
[0016] This Background of the Invention section is intended to
introduce various aspects of the art, which may be associated with
embodiments of the present inventions. Thus, the forgoing
discussion in this section provides a framework for better
understanding the present inventions, and is not to be viewed as an
admission of prior art.
SUMMARY
[0017] The present inventions solve these and other problems with
IR additive manufacturing systems and process, and address these
and other long felt needs, as well as future needs as additive
manufacturing process and systems achieve greater prevalence. The
present inventions, among other things, solve these problems and
needs by providing the articles of manufacture, devices and
processes taught, and disclosed herein.
[0018] Thus, there is provided 3-D systems using a spatial light
modulator, an array of spatial light modulators and both to form an
energy pattern on a powder bed to either directly fuse a plastic or
nylon material or to simply control the temperature of the zone to
just below the melt point of the region where the primary laser is
about to be scanned. It is theorized that the reason for
considering this approach is to improve the energy efficiency of
the system. At present either a radiant heater, a zone radiant heat
or a build plate temperature control system is used to pre-heat the
entire bead to be processed. By reducing the size of the region to
be pre-heated, the overall energy consumption of the system can be
reduced.
[0019] Further, an embodiment of the present inventions are based
on using a Digital Mirror Device (DMD) spatial light modulator, an
array of DMD devices and both assumes that the power density must
be limited to 100 W/cm.sup.2 or less when operating in a continuous
mode which is sufficient to melt and flow plastics but insufficient
to melt and fuse metals.
[0020] There is provided an additive manufacturing system for
metals that uses a laser and a spatial light modulator, an array of
spatial light modulators and both to form an energy pattern on a
powder metal layer that is fused to the layer below, a gantry
system to step and repeat the image across the powder bed, a motion
control system, an elevator to displace the part down as each layer
is fused, and a powder distribution system that can both spread the
powder and compact it before fusing, and an air tight build
chamber.
[0021] Moreover, there is provided these lasers, systems and
methods having one or more of the following features: a laser in
the wavelength range of 300-400 nm; a laser in the wavelength range
of 400-500 nm; a laser in the wavelength range of 500-600 nm; a
laser in the wavelength range of 600-800 nm; an infrared laser in
the range of 800 nm-2000 nm; the laser is homogenized by a light
pipe, micro-lens homogenizer, a diffractive element and
combinations and variations of these; the laser is time shared
between multiple print heads or multiple printer systems; the
spatial light modulator is a Digital Micro-Mirror Device (DMD)
array which is an array of micro-mirrors; the spatial light
modulator is any of a class of spatial light modulator capable of
handling multi-W to mutli-kW power levels; the DMD is air cooled;
the DMD is water cooled; the DMD is water cooled by a water cooler
such as a micro-channel cooler; the DMD is cooled by a Peltier
cooler; includes zonal radiant heaters for maintaining the build
chamber temperature; includes a heated build plate; includes a
pyrometer or a FLIR camera to monitor or control the build plate
temperature; includes a thermocouple or RTD embedded in the build
plate to monitor or control the temperature of the build plate;
includes software for determining the optimum build strategy;
includes a separate secondary laser for heating the powder bed only
where the pattern will be illuminated; uses an inert atmosphere for
the part build; uses an inert atmosphere for keeping the optics in
the system clean; and wherein the laser-spatial modulator
combination creates and image on the powder bed that has a
multi-kW/cm.sup.2 power density which is required for fusing
metals.
[0022] Moreover, there is provided an additive manufacturing system
for metals that uses a laser and a spatial light modulator, an
array of spatial light modulators, and both to form an energy
pattern on a powder metal layer that is fused to the layer below,
by for example, using a conduction mode welding process with the
aid of a second laser to pre-heat the powder bed, a gantry system
to step and repeat the image across the powder bed, to continuously
print the image by scrolling the image across the DMD synchronized
with the movement of the head, the bed and both to provide a time,
and preferably a greater amount of time to melt the powder, a
motion control system an elevator to displace the part down as each
layer is fused, and a powder distribution system that can both
spread the powder and compact it before fusing, and an air tight
build chamber.
[0023] Further, there is provided these systems and methods having
the feature of the build plate include any number of metal
materials, including aluminum, anodized aluminum, titanium, steel,
stainless steel, nickel, copper, combinations of these, as well as,
any other material which may be the same material as the powder or
different.
[0024] Still further, there is provided these lasers, systems and
methods having one or more of the following features: wherein the
laser is approximately a 450 nm blue laser; wherein the laser is in
the wavelength range of 300-400 nm; wherein the laser is in the
wavelength range of 400-500 nm; wherein the laser is in the
wavelength range of 500-600 nm; wherein the laser is in the
wavelength range of 600-800 nm; wherein the laser is an infrared
laser in the range of 800 nm-2000 nm; wherein the laser is
homogenized by either a light pipe or micro-lens homogenizer;
wherein the laser can be time shared between multiple print heads
or multiple printer systems; wherein there is a secondary laser;
wherein the secondary laser is a 450 nm blue laser; wherein the
second laser is in the wavelength range of 300-400 nm; wherein the
secondary laser is in the wavelength range of 400-500 nm; wherein
the secondary laser is in the wavelength range of 500-600 nm;
wherein the secondary laser is in the wavelength range of 600-800
nm; wherein the secondary laser is an infrared laser in the range
of 800 nm-2000 nm; is homogenized by either a light pipe,
micro-lens homogenizer or a diffractive optical element; wherein
the secondary laser is time shared between multiple print heads or
multiple printer systems; wherein the system has a spatial light
modulator; wherein the spatial light modulator is a Digital
Micro-Mirror Device (DMD); wherein the spatial light modulator is
any of a class of spatial light modulator capable of handling
multi-Watts to mutli-kW power levels; wherein the system includes
zonal radiant heaters for maintain the build chamber temperature;
wherein the system includes a heated build plate; wherein the
system includes a pyrometer or a FLIR camera to monitor or control
the build plate temperature; wherein the system includes a
thermocouple or RTD embedded in the build plate to monitor or
control the temperature of the build plate; wherein the system
includes software for determining the optimum build strategy;
wherein the system uses an inert atmosphere for the part build;
wherein the system uses an inert atmosphere for keeping the optics
in the system clean; wherein the system includes a laser-spatial
modulator combination that creates and image on the powder bed that
has a multi-Watt to multi-kWatt power density.
[0025] Moreover, there is provided these lasers, systems and
methods having one or more of the following features: having a
second laser, wherein in the second laser is used for preheat in
the system and creates and region overlapping the image of the
spatial-filter laser system on the powder bed that has a multi-Watt
to multi-kWatt power density; and, wherein laser system has a
powder bed that has a multi-Watt to multi-kWatt power density.
[0026] Yet further, there is provided an additive manufacturing
system for metals that uses a laser and a spatial light modulator
to form a pattern on a powder metal layer that is fused to the
layer below, a gantry system to step and repeat the image across
the powder bed, a motion control system, an elevator to displace
the part down as each layer is fused, and a powder distribution
system that can both spread the powder and compact it before
fusing, and an air tight build chamber.
[0027] Additionally, there is provided these systems, subsystems
and methods having one or more of the following features: wherein
the laser is is in the wavelength of a 450 nm blue laser; wherein
the laser has a wavelength range of 300-400 nm; wherein the laser
has a wavelength range of 400-500 nm; wherein the laser has a
wavelength range of 500-600 nm; wherein the laser has a wavelength
range of 600-800 nm; wherein the laser is an infrared laser in the
range of 800 nm-2,000 nm; wherein the laser is homogenized by
either a light pipe or micro-lens homogenizer; wherein the laser is
time shared between multiple print heads or multiple printer
systems; wherein the spatial light modulator is a Digital
Micro-Mirror Device (DMD) array which is an array of micro-mirrors;
wherein the spatial light modulator is any of a class of spatial
light modulator capable of handling mutli-W to multi-kW power
levels; wherein the DMD is air cooled; wherein the DMD is water
cooled by a water heat exchanger such as a micro-channel cooler;
wherein the laser is the DMD is cooled by a Peltier cooler; wherein
the system includes zonal radiant heaters for maintain the build
chamber temperature; wherein the system includes a heated build
plate; wherein the system includes a pyrometer or a FLIR camera to
monitor or control the build plate temperature; wherein the system
includes a thermocouple or RTD embedded in the build plate to
monitor or control the temperature of the build plate; wherein the
system includes software for determining the optimum build
strategy; wherein the system of claim 1 that includes a separate
secondary laser for heating the powder bed only where the pattern
will be illuminated; wherein the system uses an inert atmosphere
for the part build; wherein the system uses an inert atmosphere for
keeping the optics in the system clean; and wherein the
laser-spatial modulator combination of the system creates and image
on the powder bed that has a multi-kW power density.
[0028] Yet further there is provided an additive manufacturing
system for metals that uses a laser and a spatial light modulator
to form a pattern on a powder metal layer that is fused to the
layer below with the aid of a second laser to pre-heat the powder
bed, a gantry system to step and repeat the image across the powder
bed, a motion control system an elevator to displace the part down
as each layer is fused, and a powder distribution system that can
both spread the powder and compact it before fusing, and an air
tight build chamber.
[0029] Still further there is provided an additive manufacturing
system for metals that uses multiple lasers and multiple spatial
light modulators to form a single larger pattern on a powder metal
layer that is fused to the layer below, a gantry system to step and
repeat the image across the powder bed, a motion control system, an
elevator to displace the part down as each layer is fused, and a
powder distribution system that can both spread the powder and
compact it before fusing, and an air tight build chamber.
[0030] Moreover there is provided an additive manufacturing system
for metals that uses multiple lasers and multiple spatial light
modulators to form a checkboard pattern of images and non-images on
a powder metal layer that is fused to the layer below, a gantry
system to step and repeat the image across the powder bed, a motion
control system, an elevator to displace the part down as each layer
is fused, and a powder distribution system that can both spread the
powder and compact it before fusing, and an air tight build
chamber.
[0031] Yet further there is provided a laser spatial-light
modulator combination that creates an image and moves the image
across the DMD to create a stationary image on the moving gantry
system to extend the exposure time for printing the pattern in the
material being fused. Still further there is provided an additive
manufacturing system for forming metal objects from metal powders,
the system having: a laser source to provide a build laser beam
along a build laser beam path; a heating means for heating a metal
powder; a Digital Micro-Mirror Device (DMD) on the laser beam path,
whereby the build laser beam is directed into the DMD, wherein the
DMD creates a 2-D image pattern that is reflected from the DMD
along the laser beam path to an optical assembly; and, the optical
assembly directing the laser beam to the metal powder, whereby the
2-D image pattern is delivered to the metal powder.
[0032] Additionally, there is provided these systems, subsystems
and methods having one or more of the following features: wherein
the heating means is selected from the group consisting of electric
heaters, radiant heaters, IR heaters and a laser beam; wherein the
heating means is a laser beam having a wave length in the blue wave
length range; wherein the metal powder forms a bed of metal powder;
wherein the laser beam has a wave length select from the group
consisting of blue and green; wherein the laser beam has a wave
length selected from the group consisting of about 450 nm, about
460 nm, about 515 nm, about 532 and about 550 nm; wherein the laser
source has a power of about 1 kW to about 20 kW; wherein and the
2-D image delivers a peak power density to the metal powder of from
about 2 kW/cm.sup.2 to about 5 kW/cm.sup.2; wherein the DMD has
maximum average power density level; and wherein the peak power
density level of the 2-D image on the metal powder is at least
500.times. greater than the maximum average power density level of
the DMD; wherein the DMD has maximum average power density level;
and wherein the peak power density level of the 2-D image on the
metal powder is at least 1,000.times. greater than the maximum
average power density level of the DMD.; wherein the heating means
is configured to heat the powder to within 200.degree. C. of a
melting point of the metal powder; wherein the heating means is
configured to heat the powder to within 100.degree. C. of a melting
point of the metal powder; wherein the heating means is configured
to heat the powder to about 400.degree. C. of a melting point of
the metal powder; wherein the heating means is configured to heat
the powder to about 600.degree. C. of a melting point of the metal
powder; wherein the heating means is configured to heat the powder
to about 400.degree. C. of a melting point of the metal powder and
maintain the powder at that temperature; wherein the heating means
is configured to heat the powder to about 600.degree. C. of a
melting point of the metal powder and maintain the powder at that
temperature; wherein the heating means is configured to heat the
powder to within 200.degree. C. of a melting point of the metal
powder and maintain the powder at that temperature; having a second
laser source to provide a second build laser beam along a second
build laser beam path; a second Digital Micro-Mirror Device (DMD)
on the second laser beam path, whereby the second build laser beam
is directed into the second DMD, wherein the second DMD creates a
second 2-D image pattern that is reflected from the second DMD
along the second laser beam path to a second optical assembly;
wherein the 2-D image pattern is delivered to a first area of the
metal powder, and the second 2-D image pattern is delivered to a
second area of the metal powder; wherein the first area and the
second area are different; and, wherein the first area and the
second area are adjacent.
[0033] Additionally, there is provided these systems, subsystems
and methods having one or more of the following features: wherein
the DMD array is optimized for wavelengths in at least one of the
following wavelengths: the blue wavelength range, 400 nm, about 440
nm, 450 nm, and about 450 nm, 460 nm and about 460 nm, the green
wavelength range, 515 nm, about 515 nm, 532 nm, about 532 nm, and
the red wavelength range of 600 nm to 700 nm.
[0034] Additionally, there is provided these systems, subsystems
and methods having one or more of the following features: wherein
the build laser beam has a wavelength selected from at least one of
the following wavelengths: the blue wavelength range, 400 nm, about
440 nm, 450 nm, and about 450 nm, 460 nm and about 460 nm, the
green wavelength range, 515 nm, about 515 nm, 532 nm, about 532 nm,
and the red wavelength range of 600 nm to 700 nm.
[0035] Yet further there is provided an additive manufacturing
system for forming metal objects from metal powders, the system
having: a laser source to provide a build laser beam along a build
laser beam path; a second laser source for providing a heating
laser beam; a Digital Micro-Mirror Device (DMD) on the laser beam
path, whereby the build laser beam is directed into the DMD,
wherein the DMD creates a image that is reflected from the DMD
along the laser beam path to an optical assembly; and, the optical
assembly directing the laser beam to the metal powder, whereby the
image is delivered to the metal powder.
[0036] Still further there is provided a laser spatial-light
modulator combination that projects a 2-D pattern onto a powder bed
with an optimized grey scale in time or in the pattern, such that
the heat manipulates the molten puddle into the desired build shape
yielding sharper transitions and denser parts.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] FIG. 1 is perspective view of an embodiment of an additive
manufacturing system in accordance with the present inventions.
[0038] FIG. 2 is a cut away perspective view an embodiment of a
laser DMD print head in accordance with the present inventions.
[0039] FIG. 3 is chart comparing pulse width to repetition rate for
embodiments of a given power in accordance with the present
inventions.
[0040] FIGS. 4A and 4B are photographs of printed patterns using an
embodiment of a laser spatial light modulator in accordance with
the present inventions.
[0041] FIG. 5 is chart comparing blue light absorption in powder
bed for embodiments of systems in accordance with the present
inventions, in comparison to IR laser systems.
[0042] FIG. 6 is a schematic view of an embodiment of an overlap
pre-heat beam and build laser beam in accordance with the present
inventions.
[0043] FIG. 7 is a flow diagram of an embodiment of the timing for
a system and method in accordance with the present inventions.
[0044] FIG. 8 is a flow diagram of an embodiment of the timing for
a system and method in accordance with the present inventions.
[0045] FIG. 9 is a schematic diagram of an embodiment of a
multi-DMD laser printer system in accordance with the present
inventions.
[0046] FIG. 10 is a schematic diagram of an embodiment of a
multi-DMD laser printer system in accordance with the present
inventions.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0047] In general, the present inventions relate to laser
processing of materials, laser processing by matching preselected
laser beam wavelengths to the material to be processed to have high
or increased levels of absorptivity by the materials, systems
configurations that provide for greater speed, efficiency and size
of objects that are built, and in particular laser additive
manufacture of raw materials into large structures, parts,
components and articles with laser beams having high absorptivity
by starting raw materials.
[0048] An embodiment of the present systems and methods can use any
laser wavelengths, but the preferred embodiment is to use a pair of
blue lasers to print and fuse the layers of the part in a parallel
fashion using a spatial light modulator as the means of defining
the pattern on the powder bed that is to be fused. The laser source
and the laser beam in embodiments can have wavelengths in the blue
wavelength range and preferably can be 450 nm, about 450 nm, 460
nm, about 460 nm and have bandwidths of about 10 pm, about 5 nm,
about 10 nm and about 20 nm, and from about 2 nm to about 10 nm, as
well as greater and smaller values. The laser source and the laser
beam in embodiments can have wavelengths in the green wavelength
range and, for example, can be 515 nm, about 515 nm, 532 nm, about
532, nm, 550 nm, about 550 nm and have bandwidths of about 10 pm,
about 5 nm, about 10 nm and about 20 nm, and from about 2 nm to
about 10 nm, as well as greater and smaller values. Combinations
and variations of these various wavelengths can be use in a
system.
[0049] The print engine for an embodiment of the present systems
and methods is based on a Digital Micro-Mirror Device (DMD) array,
embodiments of which can be obtained from Texas Instruments (TI),
which creates the 2-D energy pattern to be printed. All of the DMD
products made by TI are candidates for this process, the DMD used
to print the pattern in FIGS. 4a & b is a DLP9500. By 2-D
energy pattern it is meant the image that the laser beam, or laser
beam pattern forms on the bed of powder to be fused. As discussed
in this specification while this image is observed as a 2-D energy
pattern, i.e., an image on the bed of powder, it will have depth,
i.e., 3-D properties as the energy penetrates into the bed and
fuses the material to lower layers of the build object. These print
engines can be used with any of the laser additive manufacturing
systems and methods provided in this specification, as well as
others. A blue laser reflected off the DMD array which when
reimaged can provide multi-Watt to multi-kWatt power densities in a
2-D energy pattern on the powder bed. A second blue laser can be
added to preheat the powder bed in the exact spot where the 2-D
energy pattern is imaged to reduce the energy required from the
laser-spatial light modulator pair to fuse the patterned powder to
the underlying layers. This print engine is mounted on a precision
gantry system that allows the 2-D image to be stitched together to
form a larger 2-D image which is a single layer of the part. The
system preferably includes a powder spreader as part of the gantry
system or separate from the gantry system and an elevator as part
of the build volume. The build volume is preferably very low oxygen
and more preferably oxygen free and can be filled with either an
inert gas such as Argon, or a mixture of gases to promote the
fusing process such as Argon-CO.sub.2. The powder bed and chamber
can be directly heated by electric heaters, radiant heaters, and
combinations and variations of these and other types of heaters, to
reduce the heat loss from the part during the manufacturing
process. In an embodiment, the conduction mode welding process is
the preferred method for fusing each layer together which
eliminates the spatter normally encountered in the keyhole process
which is the typical process for all additive manufacturing scanned
laser systems, prior to the present embodiments taught and
disclosed in this specification.
[0050] In general, a Digital Micromirror Device (DMD), is a device
that uses very small mirrors that can be made of aluminum to
reflect light to make an image. The DMD may also be referred to as
DLP chip. Embodiments of these devices can be a couple of
centimeters (cm), from about 1 cm to about 3 cm, from about 1 cm to
about 2 cm, a centimeter or less, less than 0.5 cm, less than 0.2
cm, or smaller, for their cross sectional dimension, (e.g., side of
square, diameter of a circle, or long side of a rectangle, these
devices may also be other shapes). These DMDs can contain from
about 100,000 to 4 million, at least about 100,000, at least about
500,000, at least about 1 million, about 2 million, or more,
mirrors, with each mirror, measuring about 4 .mu.m or less, about
7.56 .mu.m or less, about 10.8 .mu.m or less, about 10 .mu.m or
less, from about 4 .mu.m to about 20 .mu.m and combinations and
variations of these and larger and smaller sizes, The mirrors can
be laid out in a predetermined pattern, such as matrix, for
example, like a photo mosaic, with each mirror representing one
pixel.
[0051] In an embodiment the DMD includes: a CMOS DDR SRAM chip,
which is a memory cell that will electrostatically cause the mirror
to tilt to the on or off position, depending on its logic value (0
or 1); a heat sink; an optical window, which allows the laser to
pass through while protecting the mirrors from dust and debris.
[0052] In embodiments the DMD has on its surface several hundred
thousand microscopic mirrors, or more, arranged in typically a
rectangular array which correspond to the pixels in the image to be
formed and displayed. The mirrors can be individually rotated,
e.g., .+-.10-12.degree., or more or less, to an on or off state. In
the on state, the laser from the laser source, e.g., the build
laser and build laser beam, is reflected into the lens making the
pixel direct the build laser energy into the image on the powder
bed. In the off state, the laser beam, e.g., the build laser, is
directed elsewhere, e.g., to a beam dump, making the pixel not
contribute to the image or the fusing of the powder. It being
understood that in embodiments the pre-heat laser beam many also be
directed to and reflected from a DMD device to form a pre-heat
image on the powder in the bed.
[0053] In an embodiment, which could be theorized as being
analogous to greyscales of picture, the mirror is toggled on and
off very quickly, and the ratio of on time to off time determines
the amount of fusion or bonding of the powder in the powder bed.
This provides the capability to control laser power, and power
density (e.g., kW/cm.sup.2), of the laser beam on the powder bed,
without changing the power of the output beam from the laser
source. In some embodiments more than 500 different powers and
power densities, more than 700 different powers and power
densities, and more than 100,000 different powers and power
densities can be obtained. An alternative method to achieve a grey
scale affect is to pixelate the image, dropping out individual
pixels that are small in size compared to the thermal diffusion
length in the material being processed. This effectively reduces
the average power delivered to the image. This grey scale, whether
in time or in space can be used to manipulate the melt pool and
force it into a preferred shape.
[0054] Embodiments of DMDs for use in the present systems, print
heads and print engines, can be obtained from TI, these DMDs would
include: DLP2010, DLP3000, DLP3010, DLP4500, DLP4710, DLP5500,
DLP6500, DLP7000, DLP9000, DLP9000x, DLP9500, with digital
controllers; DLPA2000, DLPA3000, DLPA3005, DLPC3430, DLPC3433,
DLPC3435, DLPC3438, DLPC3439, DLPC3470, DLPC3478.
[0055] Turning to FIG. 1 there is shown an embodiment an additive
manufacturing system 100. The system 100 has a base 108 that has a
gantry system 101 mounted on the base 108. The gantry system 101
provides for movement of the DMD print head 103. This movement can
be in the x-axis 102, or in the y-axis 102a. The system 100 has a
powder bed elevator 104 (for moving the part down as it is built
allowing the next layer to be deposited on the part), a powder bed
spreader 105 and a powder roller 106. An image 107 from the DMD
print head 103 is shown in the figure on the surface of the powder.
The system has a laminar flow air knife 109 and a pyrometer or FLIR
camera 110. The base 108 and the gantry system 101 have wiring
harness 111, that can contain for example, gantry power, control
lines and fiber optics for laser beam transmission. The laser
source, or a part of it, in embodiments may be located on and move
with the gantry. In embodiments the laser source is located away
from the base, away from the laser head, or both, and is connected
to, e.g., placed in optical communication with, the laser head 103
by optical fibers. The laser source may also be connected by a
flying optic head design where the laser beam traverses free space
to the print head.
[0056] Turning to FIG. 2 there is shown a cut away perspective view
of an embodiment of a laser DMD print head 200. This embodiment can
be used with any of the systems of the present inventions,
including the system of FIG. 1, as well as others. The laser DMD
print head 200 has a housing 230, which contains the optical
components, and has first laser input 201 and a second laser input
212, and an output or exit window 209. The laser beams travel into
the housing 230 are directed and shaped by the optics and then exit
the housing 230 through exit window 209 to form patterns (on the
powder bed, which is not shown in this figure). In an embodiment
these laser inputs 201, 212 are connectors and fibers for
transmitting the laser beam from the laser source, such as QBH
fiber optic cables that are in optical communication, e.g.,
connected to, the laser source to transmit the laser beams to the
print head. The optics within the house 230 define two laser beam
paths, one for each input. Along the first laser beam path, in the
direction of the laser beam propagation, are input 201, a
collimating lens 205, a turning mirror 206, DMD 202 (which is
cooled by cooler 203), an off state beam dump 204 (which may also
have cooling), and DMD imaging lens 208, from which the laser beam
travels through window 209 to form image 210. Along the second
laser beam path, in the direction of the laser beam propagation,
are input 212, a collimating lens 210, turning mirror 207, (imaging
lens 208, may or may not be in the second beam path and a second or
separate imaging lens may be employed), and then through the window
209 to a location on the powder bed.
[0057] In an embodiment, of the additive manufacturing systems, the
first laser beam path is the build laser beam and the build laser
beam path, as it is the laser beam that fuses the powder to build
an object. The build laser beam can have a wavelength in the blue
wavelength range and preferably 440 nm, about 440 nm, 450 nm, and
about 450 nm, 460 nm and about 460 nm, in the green wavelength
range and, for example, can be 515 nm, about 515 nm, 532 nm, about
532 nm. The build laser beam can have any of the powers, power
densities, peak powers and repetition rates set forth in this
specification. The second laser beam path and the second laser beam
which travels along that path, is a pre-heat laser beam. It does
not need to be the same wavelength, and can be anything from 440 nm
to 1,100 microns, or it can be the same wavelength as the build
laser, it has a lower, similar or higher power density on the
powder bed and is used to pre-heat the powder bed, as well as
maintain the temperature of the powder bed, to facilitate the build
laser's ability to fuse the powder to build an object.
[0058] In an embodiment of printer head 230, the second laser input
212 is connected to a laser source for pre-heating the bed of
powder. In this manner, the second laser beam path, and its
associate optics are for a pre-heating system. Thus, in this
embodiment the first beam path and components from connector 201
through window 209 to image 210, as described above, provides a
laser beam for fusing the powder bed material together, i.e., a
build laser beam, or fusing laser beam; and the second beam path is
for providing a pre-heating laser beam.
[0059] An embodiment of the present systems and methods can use any
laser wavelength, but the preferred embodiment is to use a pair of
blue lasers to print and fuse the layers of the part in a parallel
fashion using an array of spatial light modulators combined with an
array of lasers as a means to define a 2-D energy pattern on the
powder bed to be fused. The energy pattern may be contiguous or
separate, when separate portions of the part or separate parts are
processed in parallel. By combining multiple energy patterning
systems together, a higher total power can be delivered to the
surface of the powder bed and as a result a larger part can be
printed with a single pulse resulting in a substantial improvement
in the build rate for the machine. Multiple DMDs are used because
of the limitation on the power handling capability of the DMD. An
off the shelf DMD system is capable of handling from 25 W/cm.sup.2
up to 75 W/cm.sup.2 of blue laser light on a continuous basis
depending on the backplane temperature and cooling method. The
larger the part to be produced, the greater the amount of total
power required to completely melt the 2-D pattern across the
surface. Since the DMD in embodiments can be the limiting factor
for the power delivered, multiple DMDs in parallel can be used to
provide the area scaling necessary to achieve the high build rates
desired. Furthermore, this print engine can be mounted on a
precision gantry system that allows the 2-D image to be stitched
together to form a larger 2-D image which is a single layer of the
part. Embodiments of the system can include a powder spreader as
part of the gantry system or separate from the gantry, and an
elevator as part of the build volume. The build volume should have
reduced oxygen, and preferably is oxygen free and can be filled,
for example, with either an inert gas such as Argon, or a mixture
of gases to promote the fusing process such as Argon-CO.sub.2. The
energy patterned areas can be pre-heated by a secondary laser
source or directly heated by electric heaters and radiant heaters
to reduce the heat loss from the part during the manufacturing
process. The secondary laser or secondary heat source raises the
base temperature of the powder bed and reduces the energy
requirements for melting the powder by the laser/spatial modulator
system, i.e., the fusing or build laser beam or sub-system of the
additive manufacturing system. In embodiments, the conduction mode
welding process is the preferred method for fusing each layer
together which eliminates the spatter normally encountered in the
keyhole process which is the baseline process for all additive
manufacturing scanned laser systems.
[0060] 2-D Energy Patterning System (for 3-D Build)
[0061] A preferred embodiment for this system is a Digital
Micro-Mirror Device (DMD) from TI. This array consists of
micro-mirrors that tilt when commanded to turn-off or turn-on the
transmitted light. Grey scale is accomplished by modulating the
position of the mirrors or the power setting of the laser at a high
speed during the process to set the amount of energy to be
delivered to the surface or by randomly turning mirrors to the off
state throughout the image to reduce the average power density in
the image. A preferred DMD arrays is one that has been optimized
for use with the wavelength of the laser beam, e.g., optimized for
wavelengths in the blue wavelength range and preferably 400 nm,
about 440 nm, 450 nm, and about 450 nm, 460 nm and about 460 nm
optimized for wavelengths in the green wavelength range and, for
example, can be 515 nm, about 515 nm, 532 nm, about 532 nm and in
the red wavelength range of 600 nm to 700 nm. Typical DMDs for
light in the visible wavelengths have a reflectivity of 88% at 450
nm and a diffraction efficiency in excess of 64%. This high
transmissivity enables these devices to handle an average power
density of 25 W/cm.sup.2 or greater depending on the cooling
method, and to handle build laser beams in the blue, green and red
wavelengths, (visible light). Tests conducted on the DMD with a
micro-channel cooler have shown that it is safe to operate the
device at power densities of up to 75 W/cm.sup.2. DMDs can have
operating power densities, e.g., average power density rating, of
from about 25 W/cm.sup.2 to 160 W/cm.sup.2, about 50 W/cm.sup.2to
100 W/cm.sup.2, and about 25 W/cm.sup.2 to 75 W/cm.sup.2, as well
as greater and smaller values. The average power density rating is
the continuous heat load rating for this device. Because of the
high reflectivity, short pulses at low repetition rates can have a
substantially higher power density than the continuous power rating
of the device. Turning to FIG. 3 there is shown a chart providing
the calculation of the maximum pulse width for a given repetition
rate to maintain this average power density. The calculation is
performed for laser power levels ranging from 150 W (Watts) to 6 kW
(kiloWatts). At 6 kW, the instantaneous power density, or peak
power, on the DMD device is 2.5 kW/cm.sup.2 for a DLP9500 device, a
factor of 1,000 greater than the average power density rating of
the device. This level of power throughput can be achieved because
the laser pulse width is short, and the duty cycle is low resulting
in the average power on the device not exceeding maximum ratings.
Optical coatings, in this case, enhanced aluminum, are capable of
sustaining very high peak power levels as long as the energy
absorbed does not exceed the damage threshold of the coating or
mirror. The damage level of an aluminum optical coating in the
pulsed mode is typically 10-50 MW/cm.sup.2 for short pulses, this
application in the present systems is well below this damage limit.
In addition, the thermal mass of the mirror serves to absorb the
12% of incident energy and determines the maximum exposure time for
a given power density to maintain the temperature of the mirror to
within the recommended operating range. Consequently, the present
DMD systems and methods can deliver peak intensities to the powder
bed that are capable of directly fusing metal powders, without
damaging the DMDs.
[0062] Thus, in embodiments of the present system the DMD devices
in additive manufacturing systems and methods are subject to, and
reflect and direct laser beams to form an image on the powder bed,
where the laser beams have a peak power density (kW/cm.sup.2) on
the powder bed that is 2.times., 10.times., 100.times.,
1,500.times., from 100.times. to 1,000.times. and greater, than the
average rated power density for the DMD.
[0063] Turning to FIGS. 4A and 4B, there are shown photographs of
printed patterns. In FIG. 4A there is shown a directly fused metal
powder, in this case it is a copper powder layer that is 100 .mu.m
thick, and the image of the "N" is directly printed by the
laser/spatial modulator system. The melting point of the copper
powder is 1085.degree. C. FIG. 4B shows a second letter "U"
directly printed by the laser/spatial modulator system. The powder
was pre-placed by hand and heated to 100.degree. C. to drive off
impurities before processing. The printing process begins by
downloading an image of the letter N to the DMD. The blue laser
system is then pulsed on for 4 mseconds at a duty cycle that
maintains the 25 W/cm.sup.2 recommended operating point and
delivers 85 Watts peak power on the surface of the powder bed which
corresponds to a power density of 3.7 kW/cm.sup.2. Since a low
power laser was used for this test, the image on the DMD was
scrolled in such a way that the image on the moving gantry system
was stationary until sufficient energy was deposited to heat the
powder and fuse it into an image. The image was then changed to the
next letter and the process repeated. The powder bed was at
20.degree. C., so all the energy for heating and melting the powder
came from the laser/spatial light modulator system. The letters are
approximately 500 .mu.m high and 500 .mu.m wide. With higher laser
powers and a heated bed, it is feasible to melt the powder with a
single pulse.
[0064] In an embodiment, a 6 kW blue laser source (a build laser
beam) is operated with a pulse width of 6.5 mseconds and a
repetition rate of 3 Hz, this corresponds to a build rate in excess
of 75 cc/hr when using copper powder. A homogenizer is used to
evenly distribute the laser energy across the DMD. The power
density on the DMD is 2.5 kW/cm.sup.2 which is 2 cm wide by 1.1 cm
high. The DMD has a resolution of 1,920 mirrors by 1,080 mirrors on
a 10.8 .mu.m pitch. The reflectivity of the DMD mirrors at this
wavelength is approximately 88%, the transmissivity of the device's
window is 97%, the diffraction efficiency of the DMD is .about.62%
at this wavelength and the transmissivity of the imaging optic is
assumed to be 99%. Using a 2:1 imaging optic, a 10 mm.times.5.5 mm
image is relayed to the powder bed and the estimated losses results
in .about.6 kW/cm.sup.2 power density on the powder bed from the
laser-spatial light modulator combination which is a factor of
1.6.times. above the intensity used in the test in FIGS. 4A and 4B,
and the total energy deposited is greater by a factor of 60.times..
The "system" image resolution is approximately 5.04 .mu.m, giving
the system higher resolution than any other laser sintering
approach. Since the published average power density of the DMD chip
is limited to 25 W/cm.sup.2, a pulse width of 6.5 msec was chosen
for the 6 kW laser source which corresponds to approximately 21
Joules of energy being deposited in the powder bed. In the
experiment shown in FIGS. 4A and 4B, significantly lower energy
deposition (0.34 Joules) was required because the illuminated
region was only 0.5 mm.times.0.5 mm. Assuming a bed temperature of
600.degree. C., it is estimated that it takes 14 Joules of energy
to melt a volume of copper powder that is 10 mm.times.5.5
mm.times.0.1 mm with a 25% void content. This analysis does not
consider any heating of the substrate, which can drive the energy
requirements higher. The highest energy requirement occurs when
printing the first layer of the part, there the diffusion of
thermal energy into the substrate can increase the energy
requirements by a factor of 3 to melt and fuse the powder. The
secondary heating laser can be used to supplement the imaging
system to deliver the extra energy required at this step. As the
build progresses, the thermal diffusion is now a factor of the mass
in the preceding layer, the thinner the part, the lower the power
requirement, the greater the dimension of the preceding layer, the
greater the power requirement, with the highest power requirement
occurring during bonding of the first layer to the build plate.
[0065] By resolution of the system or method, it is meant that
objects built by the system can have their smallest part, or
smallest dimension, equal to the stated resolution, e.g., the
resolution defines the smallest dimension of an object that can be
built. Thus, by resolution of the laser systems, resolution of the
method, it is meant that the system and method have the ability to
build a part, or have features in that part, that are at the
resolution. Thus, by way of example a 75 .mu.m resolution would
provide the ability to build parts having their smallest dimension
at 75 .mu.m, having their smallest feature at 75 .mu.m, or both.
Embodiments of the blue laser 3-D additive manufacturing systems,
e.g., 3-D blue laser printers, and embodiments of the blue laser
3-D additive manufacturing methods have resolutions from about 0.5
.mu.m to about 200 .mu.m, and larger, about 0.5 .mu.m to about 100
.mu.m, about 0.5 .mu.m to about 50 .mu.m, less than about 100
.mu.m, less than about 75 .mu.m, less than about 50 .mu.m, less
than about 25 .mu.m, less than about 10 .mu.m, and less than about
5 .mu.m. The systems can have both the capability for large
resolution, e.g., greater than 200 .mu.m, and very fine resolution
of about 0.5 .mu.m to about 10 .mu.m, and 1 .mu.m to about 5 .mu.m.
Further, embodiments of the present systems and methods, including
the embodiments and examples in the specification, as well as those
embodiments having, wavelengths of blue, 440 nm, about 440 nm, 460
nm, green, 515 nm, about 515 nm, 532 nm, about 532 nm, 550 nm,
about 550 nm, have resolutions from about 10 .mu.m to about 0.5
.mu.m, less than 10 .mu.m. less than 5 .mu.m, less than 2 .mu.m,
from about 3 .mu.m to about 0.9 .mu.m, about 1 .mu.m, and smaller
values, as well as the other values in this paragraph.
[0066] FIG. 5 is a comparison of how rapidly the blue laser light
is absorbed in a copper powder bed compared to an IR laser. The
high absorption rate of the blue laser light is a factor for making
this process obtain the desired resolutions, build speeds and both,
since the IR laser would be scattered into the powder bed outside
of the pattern to be fused and much higher power level lasers would
be necessary and the resolution is limited in the IR by the high
scattering factor. Therefore, the assumption that 100% of the light
is absorbed can be used. If the powder layer is 75% dense, then the
energy required to heat the powder layer to 1085.degree. C. from
600.degree. C., which is the melting point of copper, can be
calculated based on the heat capacity equation. Since a phase
transition is involved, the heat of fusion is included in the
energy requirement calculation. Based on the sum of the two
components, the energy required to melt a 10 mm.times.5.5
mm.times.100 .mu.m volume of copper is approximately 14 Joules.
Based on this calculation, typical DMD arrays available today are
suitable for use in a metal based additive manufacturing system,
preferably if the base temperature of the powder is adjusted to
compensate for the energy required to melt the metal or a secondary
laser is used to pre-heat the image area.
[0067] An embodiment using a 500 Watt blue laser source to heat the
copper powder bed through the DMD, can provide a pulse wide of up
to 78 msec when pulsed at a 1.5 Hz repetition rate. Under these
conditions, the 500 Watt blue laser source would deliver 39 Joules
to the copper powder bed which is sufficient energy to go from a
400.degree. C. background bed temperature to melting the
copper.
[0068] In some embodiments, while the laser-spatial light modulator
combination is capable of providing sufficient energy to melt the
50 .mu.m thick powder layer, it may not be sufficient energy to
fuse to the layers below. Since a conduction mode weld proceeds
through the layers of material in a spherical fashion, the weld is
as wide as it is deep. For example, a 50 .mu.m deep weld bead would
be at least 50 .mu.m wide. To make certain that the powder layer is
fused to the layer beneath it, then the minimum feature size will
have to be at least 1.5-2.times. the depth of the powder layer.
This means that a 75-100 .mu.m wide bead is used to fuse the powder
layer to the lower layer. Taking the energy required to fuse to the
lower solid layers into consideration increases the energy required
to melt and fuse the powder from 36 Joules to 86 Joules when going
from 400.degree. C. to the melting point of copper. In embodiments,
this is not achievable with just the laser-spatial filter
combination, so either the bed temperature is raised or a separate
source of heat is added. By adding a second laser, preferably
without a spatial light modulator, the additional heat is added to
raise the temperature of the powder, without melting it. Thus, this
second laser, can pre-heat the powder and maintain the temperature
of the powder layer and the build object above ambient temperature,
for example the powder can be pre-heated to and maintained at
temperature of greater than 100.degree. C., greater than
200.degree. C., greater than 300.degree. C., greater than
400.degree. C., from about 300.degree. C. to about 600.degree. C.,
within 300.degree. C. of the melting point of the powder, within
200.degree. C. of the melting point of the powder, within
100.degree. C. of the melting point of the powder, up to and just
below the melting temperature of the powder, and high and lower
temperatures.
[0069] As used herein, unless expressly stated otherwise, spatial
light modulator, laser/spatial light modulator, DMD systems,
laser-spatial, and similar such terms, refer to the same general
type of system, or subsystem, using micro-mirrors, micro-reflective
assemblies, or similar reflective components having micro level or
sub-micro level resolutions, to create the laser pattern and images
for the build laser beam on the powder bed as well as liquid
crystal and other types of crystal based spatial light
modulators.
[0070] The second laser (e.g., second beam path of FIG. 2, as
discussed above) illuminates the same area as the laser-spatial
light modulator does as shown in FIG. 6. In FIG. 6 there is a bed
of metal powder 600. The pre-heat laser beam forms a pre-heat laser
pattern 601 that heats an area 605 of the bed 600. There is also
shown build laser patters 602 and 603 on the bed of metal powder
600. Thus, the material in area 605 is heated by the second laser
beam, e.g., the pre-heat laser beam, and the heated material in
laser patterns 602 and 603 is fused into an object. For the case
discussed above, 86 Joules of heating is required to melt and fuse
the powder. If the 500 Watt laser-spatial filter combination
provides 39 Joules to the pattern, then the second laser provides
the balance or 47 Joules. To accommodate the time to move, coat and
perform other functions, the pulse width of the pre-heat laser can
be 10% of the duty cycle or 66 msec. This corresponds to a pre-heat
laser power of 750 Watts. Assuming the second laser heats the
powder bed region to within 200.degree. C. of the melt point, then
when the laser-spatial light modulator illuminates the part, it
raises the temperature of the patterned area on the powder bed and
the lower layers to the melting point of the copper. FIG. 7
illustrates the timing for the system. This sequence results in the
melt and complete fusion of the 50 .mu.m powder layer to the fully
dense layer below it.
[0071] In an embodiment, the laser-spatial light modulator pair is
based on a 6,000 Watt blue laser operating at a repetition rate of
1.5 Hz. The pre-heat laser is a 750 Watt laser. The pre-heat laser
operates for the same duration as mentioned above (66 msec) to
increase the powder bed temperature to within 200.degree. C. of the
melt temperature of the material to be melted (e.g. the powder in
the powder bed), in this case copper. A pyrometer or FLIR camera is
used to monitor the temperature of the powder bed during this
pre-heat process and controls the laser power to maintain that
temperature until the laser-spatial light modulator image
illuminates the powder bed region and fuses the powder to the lower
layer. The 6,000 Watt laser is on for 6.5 msec, while the 750 Watt
laser may be on for 66 msec or longer. In this embodiment, the
chamber temperature is assumed to be at or near room
temperature.
[0072] In an embodiment, the laser-spatial light modulator pair is
based on a 500 Watt blue laser operating at a maximum repetition
rate of 1.5 Hz. The pre-heat is a 1,000 Watt laser. The pre-heat
laser operates for the same duration as the case above, about 78
msecs. However, the pre-heat laser with the higher power level now
operates for only 25 msecs, giving additional time to reposition
the pattern. In this embodiment, the chamber is assumed to be at or
near room temperature.
[0073] The laser printing engine described is mounted on a
precision gantry system, such as the embodiment of FIG. 1, in an
air-tight enclosure. The air-tight enclosure if filled with an
inert gas, which is continuously circulated to clear out any
welding fumes as the process proceeds. The inert gas environment
ensures there is no surface oxidation during the build which can
lead to porosity in the part. The gantry system allows the head to
be positioned in the x-y direction, while an elevator is used to
move the part down as each new layer is printed. In principle, this
approach to step and repeat of the 2-D energy pattern can be
applied to any large volume, e.g., 0.5 m.sup.3, 1 m.sup.3, 2
m.sup.3, 3 m.sup.3, 10 m.sup.3, from 1 m.sup.3, to 10 m.sup.3, and
larger and smaller volumes, with the constraint being the accuracy
of the gantry system employed.
[0074] The build begins with a Computer Assisted Design file,
typically a step file. Software first divides the object into 50
.mu.m slices, less or greater depending on resolution and shape.
The surface revealed after the slicing is then divided up into
sections that are the same image size as the spatial light
modulator. The build strategy is then decided by the software as to
which portion of the pattern to expose first, what the exposure
levels should be and what support structure if any should be used.
The software also determines the optimum on-time for the pre-heat
laser as well as the laser-spatial modulator system. The pre-heat
time may vary depending on the density of the base material, the
melt temperature of the base material, the amount of material in
the layer below the layer to be fused and the density of the
material in the layer below the layer to be fused. Based on the
size of the part, the part complexity and the orientation of the
part, radiant heaters may be used to keep the bed, walls or ceiling
of the build chamber at an optimum temperature to prevent heat loss
at the wrong rate to the build environment. This processing
sequence is outlined in FIG. 8.
[0075] The following examples are provided to illustrate various
embodiments of the present laser systems and components of the
present inventions. These examples are for illustrative purposes,
may be prophetic, and should not be viewed as limiting, and do not
otherwise limit the scope of the present inventions.
EXAMPLE 1
[0076] An embodiment of an additive manufacturing system as
generally shown in FIG. 1. The system 100 consists of an x-y Gantry
System 101 mounted on a vibration isolation platform. The x-axis of
the gantry system 102 consists of a pair of air bearings and a
linear motor capable of positioning to an absolution position of 1
micron or less. The motor for the x-axis of the gantry system can
also move the Powder Spreader 105 in a bi-direction fashion to
spread the powder. The powder can be delivered either by a second
elevator section filled with powder or a powder hopper that drops
the powder onto the powder bed. The powder hoppers are not shown in
this figure but would be mounted at the front and back of the
gantry system. The entire system will be enclosed in an air-tight
enclosure which is also not shown in this figure. The DMD laser
print head 103 is mounted on the y-axis of the gantry system and
can traverse the bed and be positioned to within a micron of any
position along the axis repeatably. The powder bed 104 is on a high
precision elevator that enables the bed to be lowered a minimum of
10 .mu.m after each process step. This allows the powder spreader
105 to place a uniform layer of powder over the previously fused
image. A roller 106 which rotates in the opposite direction of the
motion is used to smooth and compress the powder layer. The powder
bed has built in heaters to enable elevated temperatures to be used
in the build cycle. A laminar flow air knife is placed directly
below the DMD laser print head 109 to prevent debris or smoke from
reaching the window that the DMD image and secondary pre-heat laser
emerge from. The DMD image 107 is positioned on the powder bed
according to the slicing software and the pattern is varied as the
image is stepped over the width of the image to complete the
adjacent portion of the part. The image may also be stepped further
away depending on the management of the heat buildup in the part
and the desire to minimize warpage and stress in the part.
EXAMPLE 2
[0077] An embodiment of the DMD print head as generally shown in
FIG. 2. The main laser power to be modulated is delivered to the
print head 200 through an industry standard QBH fiber cable 201.
The second laser that will be used for pre-heating is also
delivered through an industry standard QBH fiber cable 212. These
cables are designed to be robust and provide a seal to the external
environment during operation. The cables both 400 .mu.m or smaller
diameter fibers inside of a protective sheath. A pair of 40 mm
collimating lens 205, 210 are used to collimate the output of each
of the optical fibers. Depending on the shape and the uniformity of
the beam from the optical fiber, a homogenizer and beam shaping
optic would be inserted just after the collimating optic. Both the
primary laser source (build laser) and the secondary laser source
(pre-heat laser) may use the homogenizer to provide a uniform
enough intensity that the fused print is uniform. A turning mirror
206 is used to direct the collimated beam from the main laser's
optical fiber 201 onto the DMD at the requisite angle of 24 degrees
from the surface normal of the DMD. When the laser is in the on
state, the DMD 202 mirrors are tilted toward the incoming beam and
redirect the beam normal to the DMD surface. When the laser is in
the off state, the DMD 202 mirrors are tilted away from the
incoming beam and redirect the incoming beam 48 degrees away from
the incoming beam from the vector normal to the DMD surface. This
is where the beam dump 204 is located because it has to intercept
any beam energy that will be in an off state in the image. The beam
from the DMD 202 is now reimaged with a 100 mm FL lens to a spot
200 mm below the laser printing head. This is a 1:1 imaging
arrangement, other ratios may be employed depending on the size and
accuracy of the part required. The secondary laser's optical fiber
output 212 is collimated by the lens 205 and may go through a beam
homogenizer to achieve the desired uniformity of fusing. After the
beam conditioning of the secondary beam, it is directed or reimaged
onto the same spot as the DMD image using mirror 207. This system
does not go through the same imaging lens as the DMD beam. The two
beams, both the DMD beam and the secondary beam do however exit the
print head through a common window 209. However, a second window
can be used to allow the pre-heat laser to exit depending on the
geometry of the system. The net result is the overlapped DMD image
210 with the secondary laser beam on the powder bead as depicted in
FIG. 6.
EXAMPLE 3
[0078] An embodiment of the present invention relates to using
multiple DMD within the same imaging aperture or parallel imaging
apertures. Turing to FIG. 9 there is shown a schematic of a
multi-DMD laser printing system 200. The system has two laser build
subsystems 941, 942. Subsystem 941 has a laser source 901, a
collimator/homogenizer 903, a DMD 905, a mirror 905a, a 2:1 image
size reduction optical assembly having lens 907 and lens 909, a
mirror 911, and imaging lens 920, which are located along laser
beam path 913. In this manner the laser beam for fusing the powder,
e.g., the build laser beam, travels along laser beam path 913
through these various components and provides an image as image
tile 950a. Is it seen that the image tiles 950a, 950b, 950c, 950d
form a tiled image that can have a large number of tiles. Subsystem
942 has a laser source 902, a collimator/homogenizer 904, a DMD
906, a mirror 906a, a 2:1 image size reduction optical assembly
having lens 908 and lens 910, a mirror 912, and imaging lens 920,
which are located along laser beam path 914. In this manner the
laser beam for fusing the powder, e.g., the build laser beam,
travels along laser beam path 914 through these various components
and provides an image as image tile 950b.
[0079] Two additional laser build subsystems of the same
configuration as system 941, 942, would be used in this system, but
are not shown in the drawing. These additional two systems would
provide images for image tiles 950c, 950d. In this embodiment the
tile images are preferably adjacent.
[0080] For additional laser build subsystems of the same
configuration as system 941, 942, would be used in this system, but
not shown in the drawing. These four additional systems would
provide images for image tiles adjacent to 950a, 950b, 950c and
950d into the paper to create a 2-d tiled image.
[0081] This system can have lens configurations that provide either
an inverting or non-inverting image.
[0082] Each DMD has its own laser source and the image space of
each DMD can be tiled used shearing mirrors to create a continuous
image space over a much larger area than a single DMD system can
achieve. There can be some dead space between each DMD image space
which can be minimized with proper positioning of the shearing
mirrors. The image space can also be effectively spliced together
by adjusting the tilt and position of each shearing mirror. FIG. 9
shows the tiling of 2 DMD image spaces together in one axis to make
a larger composite image on the powder bed surface. This can be
extended to N.times.M DMD image spaces by compressing each DMD
image with a reducing optic, shearing each reduced image together,
then using a single lens to reimage or magnify the image back to
the desired size.
EXAMPLE 4
[0083] An embodiment of the present invention relates to using
multiple DMD within different imaging apertures to create a
parallel build capability. Turning to FIG. 10 there is shown a
multi-DMD system 1000, which has a first DMD subsystem 1040 and a
second DMD subsystem 1041 for providing two parallel build laser
beams to create separate images on the powder bed. Subsystem 1040
has a DMD 1005 that is positioned along a laser beam path 1013.
Subsystem 1040 provides image 1050a. Subsystem 1041 has a DMD 1006
that is positioned along a laser beam path 1014. Subsystem 1041
provides image 1050b.
[0084] Each DMD has its own laser source and the image space of
each DMD is tiled on the surface of the powder bed creating a
checkboard pattern of images and non-image areas. The build
strategy can be to either use each single DMD image space to build
an individual part. Or to use each individual DMD image space to
build a larger part by building multiple sections in parallel.
[0085] A second, third or fourth set of systems extending into the
paper or adjacent to the shown systems can be added to expand the
addressable image area on the powder bed.
[0086] This system can have lens configurations that provide either
an inverting or non-inverting image.
EXAMPLE 5
[0087] An embodiment of the present invention relates to using
laser beams having visible laser beams, and in particular having
wavelengths from 350 nm to 700 nm, in additive laser manufacturing
process, and in an additive laser manufacturing system, to build
articles (e.g., structures, devices, components, parts, films,
volumetric shapes, etc.) from raw materials, such as starting
powders, nanoparticles, particles, pellets, beds, powder beds,
spray powders, liquids, suspensions, emulsions and combinations and
variations of these and other starting materials known, or later
developed, in the laser additive manufacturing arts, including the
3-D printing arts.
EXAMPLE 6
[0088] In an embodiment to build articles from raw materials in
laser additive processes, wavelengths are used that have lower
reflectivity, high absorptivity, and preferably both for the
starting raw material. In particular, in an embodiment laser beam
wavelengths are predetermined based upon the starting materials to
preferably have absorption of about 10% and more, about 40% and
more, about 50% and more, and about 60% and more, and in the range
of 10% to 85%, 10% to 50%, about and about 40% to about 50%. In
particular, in an embodiment laser beam wavelengths are
predetermined based upon the starting materials to preferably have
reflectivity's of about 97% and less, about 60% and less, about 30%
and less, and in the range of 70% to 20%, in the range of 80% to
30%, and in the range of about 75% to about 25%. In embodiments
combinations of both these high absorptions and these low
reflectivities can be present. In a preferred embodiment of the
systems and processes, the laser beam or beams have wavelengths
from about 400 nm to about 500 nm are used to build articles from
starting materials made up of gold, copper, brass, silver,
aluminum, nickel, alloys of these metals, and other metals,
non-metals, materials, and alloys and combinations and variations
of these.
EXAMPLE 7
[0089] In an embodiment the use of blue lasers, e.g., about 380 nm
to about 495 nm wavelength, to additive manufacture articles from
gold, copper, brass, nickel, nickel plated copper, stainless steel,
and other, materials, metals, non-metals and alloys, is preferred.
Blue laser beams are highly absorbed by these materials at room
temperature, e.g., absorptivities of greater than about 50%. One of
several advantages of the present inventions is the ability of a
preselected wavelength laser beam, such as the blue laser beam,
that is better able to better couple the laser energy into the
material during the laser operation, e.g., the additive
manufacturing process. By better coupling the laser energy to the
material being built into an article, the chance of a runaway
process, which typically can occur with the infrared lasers is
greatly reduced and preferably eliminated. Better coupling of the
laser energy also allows for a lower power laser to be used, which
provides capital cost savings or enables multi-laser systems to be
cost effective. Better coupling also provides for greater control,
higher tolerances and thus greater reproducibility of built
articles. These features, which are not found with IR lasers and in
IR laser additive manufacturing operations, are important, to among
other products, products in the electronics, micro-mechanical
systems, medical components, engine components and power storage
fields.
EXAMPLE 8
[0090] In an embodiment a blue laser that operates in a CW mode is
used. CW operation can be preferred over a short pulse laser, in
many additive manufacturing applications, because of the ability to
rapidly modulate the laser output and control the building process
in a feedback loop, resulting in a highly repeatable process with
optimum mechanical and other physical and esthetic properties, such
as reduced surface roughness, improved porosity and improved
electrical characteristics.
EXAMPLE 9
[0091] Preferably, in some embodiments active monitoring of the
article being build is used to check the quality of the article and
the efficiency of the additive manufacturing process and systems.
For example, when the laser is processing a high resolution region
of the part being printed, a thermal camera can be used to monitor
the average temperature of the surface and a feedback loop can be
used to decrease or increase the laser power to improve the weld
puddle and ultimately the surface quality of the part. Similarly,
when the laser beam is defocused to sweep through a large low
resolution region of the part, the feedback loop can command more
laser power to keep the average temperature at the optimum
processing point, greatly reducing the time to print a part.
EXAMPLE 10
[0092] Examples of scanners and optics that can be used with the
present systems include mirrors mounted on high speed motors,
rotating polygon mirrors or high speed galvanometers. A mirror
mounted on axis of a high speed motor can create a scanning beam as
the mirror is rotated through 360 degrees. The higher the speed of
the motor, the faster the scan. The only issue with this approach
is that the laser must be turned off once the mirror is no longer
reflecting the beam as the back side of the mirror passes by the
laser beam entrance aperture. The high speed mirror can be used to
scan either the x axis or the y axis, whichever axis is chosen, the
mirror which scans the other axis must scan at a slow speed
proportional to the time it takes to complete one full scan in the
initial axis. It is preferred to use a high speed stepper motor in
this axis to enable the mirror to be moved in discrete steps while
remaining stationary while the first axis is completing its scan.
Similarly, a multi-faceted mirror or polygon mirror can be used to
perform the high speed scan function allowing higher scan speeds
because the scan is reset to the starting position as the beam
transitions across each facet of the mirror. These types of mirrors
are currently being used in supermarket scanners to scan a
product's bar code as it passes by. The primary axis can also be
scanned with a high speed galvanometer type mirror which is a
resonant type motor and oscillates at a continuous frequency
producing high speed movement of the beam. It is also possible to
precisely position galvanometer mirrors to a predetermined
position, allow systems based on the first and second axis being a
galvanometer driven mirror to draw in a vector mode where any point
on the process bed can be rapidly addressed by simultaneously
moving both mirrors. It is also feasible to combine mirrors mounted
on translation stages in a "flying optic" type design where the
beam is delivered through free space to a mirror mounted on a
gantry style system and is moved in a two dimensional, raster or
vector mode at very high speeds.
EXAMPLE 11
[0093] Embodiments of the present system do not contain and do not
require a scanner to build an object.
EXAMPLE 12
[0094] The systems and methods of examples 1-11 where the build
laser beam has a wavelength selected from one of the following wave
lengths: the blue wavelength range, 400 nm, about 440 nm, 450 nm,
and about 450 nm, 460 nm and about 460 nm, the green wavelength
range, 515 nm, about 515 nm, 532 nm, about 532 nm, and the red
wavelength range of 600 nm to 700 nm. And, were the build laser
beam has one or more of the beam properties, e.g., power, power
density, repetition rate, etc. set forth in these
specifications.
[0095] It is noted that there is no requirement to provide or
address the theory underlying the novel and groundbreaking
processes, materials, performance or other beneficial features and
properties that are the subject of, or associated with, embodiments
of the present inventions. Nevertheless, various theories are
provided in this specification to further advance the art in this
area. The theories put forth in this specification, and unless
expressly stated otherwise, in no way limit, restrict or narrow the
scope of protection to be afforded the claimed inventions. These
theories many not be required or practiced to utilize the present
inventions. It is further understood that the present inventions
may lead to new, and heretofore unknown theories to explain the
function-features of embodiments of the methods, articles,
materials, devices and system of the present inventions; and such
later developed theories shall not limit the scope of protection
afforded the present inventions.
[0096] It should be understood that the use of headings in this
specification is for the purpose of clarity, and is not limiting in
any way. Thus, the processes and disclosures described under a
heading should be read in context with the entirely of this
specification, including the various examples. The use of headings
in this specification should not limit the scope of protection
afford the present inventions.
[0097] The various embodiments of systems, equipment, techniques,
methods, activities and operations set forth in this specification
may be used for various other activities and in other fields in
addition to those set forth herein. Among others, embodiments of
the present inventions can be used with the methods, devices and
system of Patent Application Publication Nos. WO 2014/179345,
2016/0067780, 2016/0067827, 2016/0322777, 2017/0343729,
2017/0341180, and 2017/0341144 the entire disclosure of each of
which are incorporated herein by reference. Additionally, these
embodiments, for example, may be used with: other equipment or
activities that may be developed in the future; and with existing
equipment or activities which may be modified, in-part, based on
the teachings of this specification. Further, the various
embodiments set forth in this specification may be used with each
other in different and various combinations. Thus, for example, the
configurations provided in the various embodiments of this
specification may be used with each other. For example, the
components of an embodiment having A, A' and B and the components
of an embodiment having A'', C and D can be used with each other in
various combination, e.g., A, C, D, and A. A'' C and D, etc., in
accordance with the teaching of this Specification. Thus, the scope
of protection afforded the present inventions should not be limited
to a particular embodiment, configuration or arrangement that is
set forth in a particular embodiment, example, or in an embodiment
in a particular Figure.
[0098] The invention may be embodied in other forms than those
specifically disclosed herein without departing from its spirit or
essential characteristics. The described embodiments are to be
considered in all respects only as illustrative and not
restrictive.
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