U.S. patent application number 16/490922 was filed with the patent office on 2021-10-28 for three-dimensional printing.
The applicant listed for this patent is HEWLETT-PACKARD DEVELOPMENT COMPANY, L.P.. Invention is credited to David A Champion, Vladek Kasperchik, James McKinnell, Mohammed S Shaarawi.
Application Number | 20210331243 16/490922 |
Document ID | / |
Family ID | 1000005741484 |
Filed Date | 2021-10-28 |
United States Patent
Application |
20210331243 |
Kind Code |
A1 |
Shaarawi; Mohammed S ; et
al. |
October 28, 2021 |
THREE-DIMENSIONAL PRINTING
Abstract
In an example of a method for three-dimensional (3D) printing,
build material layers are patterned to form an intermediate
structure. During patterning, a binding agent is selectively
applied to define: a build material support structure and a
patterned intermediate part. Also during patterning, i) the binding
agent and a separate agent including a gas precursor or ii) a
combined agent including a binder and the gas precursor are
selectively applied to define a patterned breakable connection
between at least a portion of the build material support structure
and at least a portion patterned intermediate part. The
intermediate structure is heated to a temperature that activates
the gas precursor to create gas pockets in the patterned breakable
connection.
Inventors: |
Shaarawi; Mohammed S;
(Corvallis, OR) ; McKinnell; James; (Corvallis,
OR) ; Champion; David A; (Corvallis, OR) ;
Kasperchik; Vladek; (Corvallis, OR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HEWLETT-PACKARD DEVELOPMENT COMPANY, L.P. |
Spring |
TX |
US |
|
|
Family ID: |
1000005741484 |
Appl. No.: |
16/490922 |
Filed: |
February 28, 2018 |
PCT Filed: |
February 28, 2018 |
PCT NO: |
PCT/US2018/020169 |
371 Date: |
September 4, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B33Y 40/00 20141201;
B22F 10/14 20210101; B33Y 10/00 20141201; B33Y 80/00 20141201; C09D
11/033 20130101; B22F 10/47 20210101; C09D 11/38 20130101; B33Y
70/00 20141201 |
International
Class: |
B22F 10/14 20060101
B22F010/14; B33Y 10/00 20060101 B33Y010/00; B33Y 80/00 20060101
B33Y080/00; B33Y 70/00 20060101 B33Y070/00; B22F 10/47 20060101
B22F010/47; B33Y 40/00 20060101 B33Y040/00; C09D 11/38 20060101
C09D011/38; C09D 11/033 20060101 C09D011/033 |
Claims
1. A method for three-dimensional (3D) printing, comprising:
patterning build material layers to form an intermediate structure,
the patterning including: selectively applying a binding agent to
define: a build material support structure and a patterned
intermediate part; and selectively applying i) the binding agent
and a separate agent including a gas precursor or ii) a combined
agent including a binder and the gas precursor to define a
patterned breakable connection between at least a portion of the
build material support structure and at least a portion of the
patterned intermediate part; and heating the intermediate structure
to a temperature that activates the gas precursor to create gas
pockets in the patterned breakable connection.
2. The method as defined in claim 1 wherein the heating involves
exposure to a series of temperatures that form: a 3D object from
the patterned intermediate part; a 3D support structure from the
build material support structure; and an irreversibly breakable
connection from the patterned breakable connection, the
irreversibly breakable connection including the gas pockets and
being positioned between the 3D object and the 3D support
structure.
3. The method as defined in claim 2 wherein the heating involves:
heating the intermediate structure to a de-binding temperature; and
then heating the intermediate structure to an initial sintering
temperature, followed by a gas pocket formation temperature,
followed by a final sintering temperature.
4. The method as defined in claim 2, further comprising removing
the 3D support structure from the 3D object by breaking the
irreversibly breakable connection.
5. The method as defined in claim 1 wherein the patterned
intermediate part at least partially overlies the build material
support structure.
6. The method as defined in claim 1 wherein patterning the build
material layers includes: patterning a first build material layer
by selectively applying the binding agent to define: a layer of the
build material support structure and a layer of the patterned
intermediate part separated by non-patterned build material;
applying an other layer of build material on the patterned first
build material layer; patterning the other layer of build material
by: selectively applying i) the binding agent and the separate
agent or ii) the combined agent on a portion of the other layer of
build material that overlies the build material support structure,
thereby forming the patterned breakable connection; and selectively
applying the binding agent on an other portion of the other layer
of build material to define an outer layer of a region of the
patterned intermediate part; and forming a remaining region of the
patterned intermediate part on the patterned breakable connection
and in contact with the region of the patterned intermediate part,
thereby forming the intermediate structure including the patterned
intermediate part and the build material support structure
temporarily bound together at the patterned breakable
connection.
7. The method as defined in claim 6 wherein the build material
support structure is a multi-layer structure, and wherein prior to
patterning the other layer of build material the method further
comprises iteratively applying additional build material layers and
selectively applying the binding agent to the additional build
material layers to define several layers of the build material
support structure and several layers of the region of the patterned
intermediate part, wherein the several layers of the build material
support structure and the several layers of the region of the
patterned intermediate part are separated by additional
non-patterned build material.
8. The method as defined in claim 7 wherein the forming of the
remaining region of the patterned intermediate part includes:
applying a further layer of build material on the patterned
breakable connection and the outer layer of the region of the
patterned intermediate part; and selectively applying the binding
agent to the further layer to define a patterned layer of the
remaining region of the patterned intermediate part.
9. The method as defined in claim 1 wherein patterning the build
material layers includes: iteratively applying individual build
material layers; selectively applying the binding agent to each of
the individual build material layers to define several layers of
the build material support structure and several layers of the
patterned intermediate part; and selectively applying the i) the
binding agent and the separate agent or ii) the combined agent on
each of the individual build material layers to define the
patterned breakable connection between the several layers of the
build material support structure and the several layers of the
patterned intermediate part.
10. The method as defined in claim 1 wherein the gas precursor is
selected from the group consisting of a transition metal hydride,
an alkaline earth carbonate that releases carbon dioxide when
activated, and a solid state mixture of an oxidizable species and
an oxidizing agent to produce an oxidation product in a gas state
at a sintering temperature used during the heating.
11. The method as defined in claim 10 wherein one of: the gas
precursor is the transition metal hydride, and the method further
comprises exposing the intermediate structure to hydrogen gas
during the heating; or the gas precursor is the solid state
mixture, and the method further comprises exposing the intermediate
structure to an inert gas or a vacuum environment during the
heating.
12. A liquid functional agent for three-dimensional (3D) printing,
comprising: a compound that is to be activated at a temperature
within a sintering temperature range of a build material of an
intermediate structure to generate gas pockets within a portion of
the intermediate structure that is patterned with the liquid
functional agent, the compound being selected from the group
consisting of a transition metal hydride, an alkaline earth
carbonate selected from the group consisting of barium carbonate
and strontium carbonate, and a solid state mixture of an oxidizable
species and an oxidizing agent to produce an oxidation product in a
gas state in the sintering temperature range; any of a surfactant
or a dispersing aid; a co-solvent; and a balance of water.
13. The liquid functional agent as defined in claim 12 wherein: the
compound is the transition metal hydride, and the transition metal
hydride is titanium hydride; or the compound is the solid state
mixture and the oxidizable species includes carbon particles and
the oxidizing agent is a transition metal oxide selected from the
group consisting of Fe.sub.2O.sub.3, Mn.sub.2O.sub.3,
Cr.sub.2O.sub.3, and Co.sub.3O.sub.4.
14. The liquid functional agent as defined in claim 12, further
comprising a binder.
15. A three-dimensional (3D) printed article, comprising: a first
object; a second object; and an irreversibly breakable connection
between the first and second objects, wherein the irreversibly
breakable connection comprises gas pockets.
Description
BACKGROUND
[0001] Three-dimensional (3D) printing may be an additive printing
process used to make three-dimensional solid parts from a digital
model. 3D printing is often used in rapid product prototyping, mold
generation, mold master generation, and short run manufacturing.
Some 3D printing techniques are considered additive processes
because they involve the application of successive layers of
material. This is unlike traditional machining processes, which
often rely upon the removal of material to create the final part.
Some 3D printing methods use chemical binders or adhesives to bind
build materials together. Other 3D printing methods involve at
least partial curing, thermal merging/fusing, melting, sintering,
etc. of the build material. For some materials, at least partial
melting may be accomplished using heat-assisted extrusion, and for
some other materials (e.g., polymerizable materials), curing or
fusing may be accomplished using, for example, ultra-violet light
or infrared light.
BRIEF DESCRIPTION OF THE DRAWINGS
[0002] Features of examples of the present disclosure will become
apparent by reference to the following detailed description and
drawings, in which like reference numerals correspond to similar,
though perhaps not identical, components. For the sake of brevity,
reference numerals or features having a previously described
function may or may not be described in connection with other
drawings in which they appear.
[0003] FIG. 1 is a flow diagram illustrating an example of a 3D
printing method disclosed herein;
[0004] FIGS. 2A through 2D are schematic views of different
examples of intermediate structures, each of which includes a build
material support structure, a patterned intermediate part, and a
patterned breakable connection defined between at least a portion
of the build material support structure and the patterned
intermediate part;
[0005] FIG. 3 is a flow diagram illustrating another example of the
3D printing method disclosed herein;
[0006] FIGS. 4A through 4J are schematic and partially
cross-sectional views depicting the formation of a 3D object and a
3D support structure using an example of the 3D printing method
disclosed herein; and
[0007] FIG. 5 is a simplified isometric and schematic view of an
example of a 3D printing system disclosed herein.
DETAILED DESCRIPTION
[0008] In some examples of three-dimensional (3D) printing, a
liquid functional agent is selectively applied to a layer of build
material on a build platform to pattern a selected region of the
layer, and then another layer of the build material is applied
thereon. The liquid functional agent may be applied to this other
layer of build material, and these processes may be repeated to
form a green part (also known as a green body, and referred to
herein as a patterned intermediate part) of the 3D part that is
ultimately to be formed. The liquid functional agent is capable of
penetrating the layer of build material onto which it is applied,
and spreading onto the exterior surface of the build material
particles of that layer. The liquid functional agent may include a
binder that holds the build material particles of the patterned
intermediate part together. The patterned intermediate part may
then be exposed to heat to sinter the build material in the
patterned intermediate part to form the 3D object/part.
[0009] In some 3D printing methods, sections of a patterned
intermediate part may not directly be supported by the build
platform during the patterning process, and/or may not be supported
by a heating mechanism platform during the sintering process. A
lack of support can lead to deformation of those sections during
patterning and/or sintering. The lack of support may be undesirable
because it may render the final finished part otherwise unusable,
aesthetically unpleasing, etc. In the examples disclosed herein, a
build material support structure is built as the patterned
intermediate part is built, which provides support to the patterned
intermediate part during patterning. Also in the examples disclosed
herein, the build material support structure is temporarily bound
to the patterned intermediate part and thus can be moved to a
heating mechanism platform with the patterned intermediate part to
provide support during sintering.
[0010] As mentioned herein, the build material support structure is
temporarily bound to the patterned intermediate part at a patterned
breakable connection. During sintering, the patterned breakable
connection forms an irreversibly breakable connection that includes
a plurality of gas pockets. These gas pockets provide the
irreversibly breakable connection with fragility, which allows the
3D support structure to be easily removed from the 3D object.
Definitions
[0011] Throughout this disclosure, it is to be understood that
terms used herein will take on their ordinary meaning in the
relevant art unless specified otherwise. Several terms used herein
and their meanings are set forth below.
[0012] The singular forms "a", "an", and "the" include plural
referents unless the context clearly dictates otherwise.
[0013] The terms comprising, including, containing and various
forms of these terms are synonymous with each other and are meant
to be equally broad.
[0014] As used herein, the terms "remaining region of the patterned
intermediate part," "portion of the patterned intermediate part,"
or "layer of the patterned intermediate part" refers to a
subsection of the intermediate part that does not have a shape
representative of the final 3D printed part, and that includes
build material particles patterned with a binding liquid functional
agent (i.e., binding agent). In the remaining portion, the portion,
or the layer of the patterned intermediate part, the build material
particles may or may not be weakly bound together by one or more
components of the binding liquid functional agent and/or by
attractive force(s) between the build material particles and the
binding agent. Moreover, it is to be understood that any build
material that is not patterned with the binding agent is not
considered to be part of the portion of the patterned intermediate
part, even if it is adjacent to or surrounds the portion of the
patterned intermediate part.
[0015] As used herein, the term "patterned intermediate part"
refers to an intermediate part that has a shape representative of
the final 3D printed part, and that includes build material
particles patterned with the binding agent. In the patterned
intermediate part, the build material particles may or may not be
weakly bound together by one or more components of the binding
agent and/or by attractive force(s) between the build material
particles and the binding agent. In some instances, the mechanical
strength of the patterned intermediate part is such that it cannot
be handled or extracted from a build platform. Moreover, it is to
be understood that any build material that is not patterned with
the binding liquid functional agent is not considered to be part of
the patterned intermediate part, even if it is adjacent to or
surrounds the patterned intermediate part.
[0016] As used herein, the term "build material support structure"
refers to at least one layer of build material that is patterned
with the binding agent and that provides support for i) an
additional layer of build material that is patterned with the gas
generating liquid functional agent, ii) additional layer(s) of
build material that are patterned with the binding agent, and/or
iii) patterned layers during sintering.
[0017] Also as used herein, a "patterned breakable connection"
refers to a layer of build material patterned with the gas
generating liquid functional agent and positioned between at least
a portion of the build material support structure and at least a
portion of the patterned intermediate part.
[0018] As used herein, the term "intermediate structure" includes
the patterned intermediate part and the build material support
structure temporarily bound together by the patterned breakable
connection.
[0019] As used herein, the term "densified intermediate part"
refers to a patterned intermediate part from which the liquid
components of the binding agent have at least substantially
evaporated. At least substantial evaporation of the liquid
components of the binding agent leads to densification of the
intermediate part, which may be due to capillary compaction. The at
least substantial evaporation of the binding agent may also allow
the binder to bind the build material particles of the densified
intermediate part. In other words, the "densified intermediate
part" is an intermediate part with a shape representative of the
final 3D printed part and that includes the build material
particles bound together by the binder. Compared to the patterned
intermediate part, the mechanical strength of the densified
intermediate part is greater, and the densified intermediate part
can be handled or extracted from the build area platform.
[0020] The patterned or densified intermediate part may be known as
a green part, but it is to be understood that the term "green" when
referring to the patterned intermediate/green part or the densified
intermediate/green part does not connote color, but rather
indicates that the part is not yet fully processed.
[0021] As used herein, the term "at least substantially binder-free
intermediate part" refers to an intermediate part that has been
exposed to a heating process that initiates thermal decomposition
of the binder so that the temporary binder is at least partially
removed. In some instances, volatile organic components of, or
produced by the thermally decomposed binder are completely removed
and a very small amount of non-volatile residue from the thermally
decomposed binders may remain. The small amount of the non-volatile
residue is generally <2 wt % of the initial binder amount, and
in some instances is <0.1 wt % of the initial binder amount. In
other instances, the thermally decomposed binder (including any
products and residues) is completely removed. In other words, the
"at least substantially binder-free intermediate part" refers to an
intermediate part with a shape representative of the final 3D
printed part and that includes build material particles bound
together as a result of i) weak sintering (i.e., low level necking
between the particles, which is able to preserve the part shape),
or ii) a small amount of the non-volatile binder residue remaining,
and/or iii) a combination of i and ii.
[0022] The at least substantially binder-free intermediate part may
have porosity similar to or greater than the densified intermediate
part (due to temporary binder removal), but the porosity is at
least substantially eliminated during the transition to the 3D
printed part/object.
[0023] The at least substantially binder-free intermediate part may
be known as a gray part, but it is to be understood that the term
"gray" when referring to the at least substantially binder-free
gray part does not connote color, but rather indicates that the
part is not yet fully processed.
[0024] As used herein, the terms "3D printed part or object," "3D
part," and "3D object" refer to a completed, sintered part.
[0025] As used herein, the "gas generating liquid functional agent"
refers to a liquid functional agent that includes a compound that
will decompose or react with an oxidizing agent during heating of
the intermediate structure to generate gas pockets within a portion
of the intermediate structure that is patterned with the gas
generating liquid functional agent. "Gas pockets" are voids,
spaces, or pores that are formed among build material and/or
coalesced (e.g., sintered) build material as a reaction product of
a reaction involving the compound during heating of the
intermediate structure. In some examples, the gas generating liquid
functional agent is a separate agent used in combination with the
binding agent. In these examples, the gas generating liquid
functional agent does not include a binder. In other examples, the
gas generating liquid functional agent may also include the binder
that can temporarily bind the build material of the patterned
breakable connection. In these examples, the gas generating liquid
functional agent may be referred to as a combined agent, and a
separate binding agent may not be used for patterning the breakable
connection. Examples of the gas generating liquid functional agent
are described further herein below.
[0026] Also as used herein, the "binding liquid functional agent"
or "binding agent" refers to a patterning fluid that includes a
binder, but that does not include the compound that will decompose
or react to form the gas pockets upon heating. Examples of the
binding agent are described further herein below.
[0027] It is to be understood that the weight percentages provided
herein may vary, depending upon the weight percentage of the active
components within a solution, dispersion, etc. used to form the
binding agent, gas generating liquid functional agent, etc., and
also on the desired weight percentage of the active components
within the binding agent, gas generating liquid functional agent,
etc. For example, if a dispersion (to be added to the binding
agent) includes 10% of the active component, and the target weight
percentage of the active component in the binding agent is 0.01%,
then the amount of the dispersion that is added is 0.1% to account
for the non-active components in the dispersion.
[0028] The examples disclosed herein provide several methods for
forming the intermediate structure, and the final sintered object,
support, and connection. In some examples, both the gas generating
liquid functional agent and the binding liquid functional agent are
utilized in forming the patterned breakable connection. In other
examples, the patterned breakable connection is formed using the
combined agent. In the examples disclosed herein, the same types of
build material, gas generating liquid functional agents, and/or
binding liquid functional agents may be used. Each of the
components will now be described.
[0029] Build Material
[0030] In examples of the method disclosed herein, the same build
material may be used for generating the 3D part, the support
structure, and the irreversibly breakable connection. The build
material can include metal build material.
[0031] In an example, the build material particles are a single
phase metallic material composed of one element. In this example,
the sintering temperature may be below the melting point of the
single element.
[0032] In another example, the build material particles are
composed of two or more elements, which may be in the form of a
single phase metallic alloy or a multiple phase metallic alloy. In
these other examples, sintering generally occurs over a range of
temperatures.
[0033] The build material particles may be composed of a single
element or alloys. Some examples of the metallic build material
particles include steels, stainless steel, bronzes, titanium (Ti)
and alloys thereof, aluminum (Al) and alloys thereof, nickel (Ni)
and alloys thereof, cobalt (Co) and alloys thereof, iron (Fe) and
alloys thereof, nickel cobalt (NiCo) alloys, gold (Au) and alloys
thereof, silver (Ag) and alloys thereof, platinum (Pt) and alloys
thereof, and copper (Cu) and alloys thereof. Some specific examples
include AlSi10Mg, 2xxx series aluminum, 4xxx series aluminum, CoCr
MP1, CoCr SP2, MaragingSteel MS1, Hastelloy C, Hastelloy X,
NickelAlloy HX, Inconel IN625, Inconel IN718, SS GP1, SS 17-4PH, SS
316L, SS 430L, Ti6Al4V, and Ti-6Al-4V ELI7. While several example
alloys have been provided, it is to be understood that other alloys
may be used.
[0034] The temperature(s) at which the metallic particles sinter
is/are above the temperature of the environment in which the
patterning portion of the 3D printing method is performed (e.g.,
above 100.degree. C.). In some examples, the metallic build
material particles may have a melting point ranging from about
500.degree. C. to about 3500.degree. C. In other examples, the
metallic build material particles may be an alloy having a range of
melting points.
[0035] The build material particles may be similarly sized
particles or differently sized particles. The individual particle
size of each of the build material particles is up to 100 .mu.m. In
an example, the build material particles may be particles, having a
particle size ranging from about 1 .mu.m to about 100 .mu.m. In
another example, the individual particle size of the build material
particles ranges from about 1 .mu.m to about 30 .mu.m. In still
another example, the individual particle size of the build material
particles ranges from about 2 .mu.m to about 50 .mu.m. In yet
another example, the individual particle size of the build material
particles ranges from about 5 .mu.m to about 15 .mu.m. In yet
another example, the individual particle size of the build material
particles ranges from about 3.25 .mu.m to about 5 .mu.m. In yet
another example, the individual particle size of the build material
particles is about 10 .mu.m. As used herein, the term "individual
particle size" refers to the particle size of each individual build
material particle. As such, when the build material particles have
an individual particle size ranging from about 1 .mu.m to about 100
.mu.m, the particle size of each individual build material particle
is within the disclosed range, although individual build material
particles may have particle sizes that are different than the
particle size of other individual build material particles. In
other words, the particle size distribution may be within the given
range. The particle size of the build material particles generally
refers to the diameter or volume weighted average/mean diameter of
the build material particle, which may vary, depending upon the
morphology of the particle. The build material particles may also
be non-spherical, spherical, random shapes, or combinations
thereof.
[0036] Gas Generating Liquid Functional Agent
[0037] The gas generating liquid functional agent may be used to
pattern build material where it is desirable to form the
irreversibly breakable connection. Some examples of the gas
generating liquid functional agent are used with a separate binding
agent; and other examples of the gas generating liquid functional
agent are a combined agent that includes the binder, and thus are
not used with a separate binding agent.
[0038] Whether a separate agent or a combined agent, in some
examples, the gas generating liquid functional agents disclosed
herein are aqueous (i.e., water) based liquids including a gas
precursor compound(s). In other examples, the gas generating liquid
functional agents disclosed herein are solvent based liquids
including the gas precursor compound(s).
[0039] The gas precursor includes a compound that is to be
activated, at a temperature within a sintering temperature range of
a build material of an intermediate structure, to generate gas
pockets within a portion of the intermediate structure that is
patterned with the gas generating liquid functional agent, the
compound being selected from the group consisting of a transition
metal hydride, an alkaline earth carbonate selected from the group
consisting of barium carbonate and strontium carbonate, and a solid
state mixture of an oxidizable species and an oxidizing agent to
produce an oxidation product in a gas state in the sintering
temperature range. As such, the gas precursor compound(s) is
selected such that it undergoes reaction(s) to initiate gas
formation at the high temperatures used in the sintering stage(s)
of the printing process. This high activation temperature property,
therefore, limits the type of gas precursor compounds that are
capable of producing the mechanically weak junctions between the
sintered object/part and the sintered support structure. In the
examples disclosed herein, the gas precursor compound(s) may
undergo thermal decomposition or oxidation when exposed to
temperature(s) within a sintering temperature range of the printing
process.
[0040] Some examples of the gas precursor compound(s) include
inorganic materials that produce gas through thermal decomposition.
Suitable inorganic materials include transition metal hydrides (for
example, titanium hydride, TiH.sub.(2-X)) and alkaline earth
carbonates (for example, calcium carbonate, barium carbonate,
strontium carbonate).
[0041] At temperatures between about 300.degree. C. to about
500.degree. C., titanium hydride decomposes slowly, releasing
hydrogen. Given its non-stoichiometric nature, however, its rate of
decomposition increases with further increase in temperature until
the melting temperature of metallic titanium is reached. Thus,
titanium hydride can be used as a gas precursor compound when it is
desirable to form gas pockets at a temperature range of from about
500.degree. C. to about 900.degree. C. Titanium hydride may be a
suitable gas precursor compound with an aluminum build material.
Titanium hydride is hydrolytically stable, and thus can be readily
incorporated into the aqueous based agents disclosed herein.
[0042] Alkaline earth carbonates decompose releasing carbon dioxide
(CO.sub.2) at elevated temperatures. In other words, the gas
precursor is an alkaline earth carbonate that releases CO.sub.2
when activated. Examples of the alkaline earth carbonates that may
be suitable gas precursor compound(s) include calcium carbonate
(which thermally decomposes at about 840.degree. C.), barium
carbonate (which thermally decomposes at about 1,360.degree. C.),
and strontium carbonate (which thermally decomposes at temperatures
ranging from about 1,100.degree. C. up to about 1,500.degree. C.).
In an example, the alkaline earth carbonate has a particle size
less than 100 nm. A greater CO.sub.2 concentration in the
atmosphere during thermal decomposition can increase the carbonate
decomposition temperature. As such, it may be desirable for
alkaline earth carbonate decomposition to take place in an inert,
reducing, or vacuum environment.
[0043] Some other examples of the gas precursor compound(s) include
materials that produce gas through oxidation. Examples of these
materials include solid state mixtures of oxidizable species with
oxidizing agents. Components for the solid state mixtures are
chosen such that i) the gas forming redox reactions in the mixtures
are activated at the sintering temperatures of the metal part, and
ii) the reducing and oxidizing components in the mixtures are
present in stoichiometric ratio, thereby enabling a maximum yield
of gas produced by the redox reaction. In examples of the solid
state mixtures, the oxidizable species includes carbon particles
and the oxidizing agent is a transition metal oxide selected from
the group consisting of Fe.sub.2O.sub.3 (iron (III) oxide),
Mn.sub.2O.sub.3 (manganese (III) oxide), Cr.sub.2O.sub.3 (chromium
(III) oxide), Co.sub.3O.sub.4 (cobalt (II, III) oxide), etc. The
gas produced from such oxides may include the carbon oxide gases,
carbon dioxide (CO.sub.2) and carbon monoxide (CO). The gas
production from such oxides may proceed according to the scheme
illustrated in equations I to IV below:
2Me.sub.2O.sub.3+3C.fwdarw.4Me+3CO.sub.2 (I)
2Me.sub.2O.sub.3+3C.fwdarw.4Me+6CO (II)
Me.sub.3O.sub.4+2C.fwdarw.3Me+2CO.sub.2 (III)
Me.sub.3O.sub.4+4C.fwdarw.3Me+4CO (IV)
where Me represents metal. When ferrous oxides are used in the
reactions above, the reactions proceed with rates and yield at
temperatures typically higher than about 900.degree. C. to about
1000.degree. C., which overlaps with the temperature range used for
the sintering of ferrous alloy powders.
[0044] The gas precursor compound may be present in the gas
generating liquid functional agent in an amount ranging from about
1 wt % to about 75 wt % of the total weight of the gas generating
liquid functional agent. In another example, the gas precursor
compound may be present in the gas generating liquid functional
agent in an amount ranging from about 2 wt % to about 40 wt % or
about 50 wt % of the total weight of the gas generating liquid
functional agent. These percentages may include both active gas
precursor compound and other non-active components present with the
compound. It is to be understood that the upper limit may be
increased as long as the gas generating liquid functional agent can
be jetted via a desired inkjet printhead.
[0045] When the gas generating liquid functional agent is used with
a separate binding agent, the gas generating liquid functional
agent may include the previously described compound (i.e., gas
precursor compound), any of a surfactant or a dispersing aid, a
co-solvent, and a balance of water. The separate gas generating
liquid functional agent may also include antimicrobial agent(s)
and/or anti-kogation agent(s), but does not include a binder.
[0046] The co-solvent may be an organic co-solvent present in the
gas generating liquid functional agent in an amount ranging from
about 0.5 wt % to about 50 wt % (based on the total weight of the
gas generating liquid functional agent). It is to be understood
that other amounts outside of this range may also be used
depending, at least in part, on the jetting architecture used to
dispense the gas generating liquid functional agent. The organic
co-solvent may be any water miscible, high-boiling point solvent,
which has a boiling point of at least 120.degree. C. Classes of
organic co-solvents that may be used include aliphatic alcohols,
aromatic alcohols, diols, glycol ethers, polyglycol ethers,
2-pyrrolidones/pyrrolidinones, caprolactams, formamides,
acetamides, glycols, and long chain alcohols. Examples of these
co-solvents include primary aliphatic alcohols, secondary aliphatic
alcohols, 1,2-alcohols, 1,3-alcohols, 1,5-alcohols, ethylene glycol
alkyl ethers, propylene glycol alkyl ethers, higher homologs
(C.sub.6-C.sub.12) of polyethylene glycol alkyl ethers, N-alkyl
caprolactams, unsubstituted caprolactams, both substituted and
unsubstituted formamides, both substituted and unsubstituted
acetamides, and the like. In some examples, the gas generating
liquid functional agent may include 2-pyrrolidone, 1,2-butanediol,
2-methyl-1,3-propanediol, 1-(2-hydroxyethyl)-2-pyrrolidone, or
combinations thereof.
[0047] The gas generating liquid functional agent may also include
surfactant(s) and/or dispersing aid(s). Surfactant(s) and/or
dispersing aid(s) may be used to improve the wetting properties and
the jettability of the gas generating liquid functional agent.
Examples of suitable surfactants and dispersing aids include those
that are non-ionic, cationic, or anionic. Examples of suitable
surfactants/wetting agents include a self-emulsifiable, non-ionic
wetting agent based on acetylenic diol chemistry (e.g.,
SURFYNOL.RTM. SEF from Air Products and Chemicals, Inc.), a
non-ionic fluorosurfactant (e.g., CAPSTONE.RTM. fluorosurfactants
from DuPont, previously known as ZONYL FSO), and combinations
thereof. In a specific example, the surfactant is a non-ionic,
ethoxylated acetylenic diol (e.g., SURFYNOL.RTM. 465 from Air
Products and Chemical Inc.). In other examples, the surfactant is
an ethoxylated low-foam wetting agent (e.g., SURFYNOL.RTM. 440 or
SURFYNOL.RTM. CT-111 from Air Products and Chemical Inc.) or an
ethoxylated wetting agent and molecular defoamer (e.g.,
SURFYNOL.RTM. 420 from Air Products and Chemical Inc.). Still other
suitable surfactants include non-ionic wetting agents and molecular
defoamers (e.g., SURFYNOL.RTM. 104E from Air Products and Chemical
Inc.) or secondary alcohol ethoxylates (commercially available as
TERGITOL.RTM. TMN-6, TERGITOL.RTM. 15-S-7, TERGITOL.RTM. 15-S-9,
etc. from The Dow Chemical Co.). In some examples, it may be
desirable to utilize a surfactant having a hydrophilic-lipophilic
balance (HLB) less than 10. Examples of suitable dispersing aid(s)
include those of the SILQUEST.TM. series from Momentive, including
SILQUEST.TM. A-1230. Whether a single surfactant or dispersing aid
is used or a combination of surfactants and/or dispersing aids is
used, the total amount of surfactant(s) and/or dispersing aid(s) in
the gas generating liquid functional agent may range from about 0.1
wt % to about 6 wt % based on the total weight of the gas
generating liquid functional agent.
[0048] The gas generating liquid functional agent may also include
antimicrobial agent(s). Suitable antimicrobial agents include
biocides and fungicides. Example antimicrobial agents may include
the NUOSEPT.RTM. (Ashland Inc.), UCARCIDE.TM. or KORDEK.TM. or
ROCIMA.TM. (Dow Chemical Co.), PROXEL.RTM. (Arch Chemicals) series,
ACTICIDE.RTM. B20 and ACTICIDE.RTM. M20 and ACTICIDE.RTM. MBL
(blends of 2-methyl-4-isothiazolin-3-one (MIT),
1,2-benzisothiazolin-3-one (BIT), and Bronopol) (Thor Chemicals),
AXIDE.TM. (Planet Chemical), NIPACIDE.TM. (Clariant), blends of
5-chloro-2-methyl-4-isothiazolin-3-one (CIT or CMIT) and MIT under
the tradename KATHON.TM. (Dow Chemical Co.), and combinations
thereof. In an example, the gas generating liquid functional agent
may include a total amount of antimicrobial agents that ranges from
about 0.01 wt % to about 1 wt %. In an example, the antimicrobial
agent is a biocide and is present in the gas generating liquid
functional agent in an amount of about 0.1 wt % (based on the total
weight of the gas generating liquid functional agent). These
percentages may include both active antimicrobial agent and other
non-active components present with the antimicrobial agent.
[0049] An anti-kogation agent may also be included in the gas
generating liquid functional agent. Kogation refers to the deposit
of dried solids on a heating element of a thermal inkjet printhead.
Anti-kogation agent(s) is/are included to assist in preventing the
buildup of kogation, and thus may be included when the gas
generating liquid functional agent is to be dispensed using a
thermal inkjet printhead. Examples of suitable anti-kogation agents
include oleth-3-phosphate (commercially available as CRODAFOS.TM.
O3A or CRODAFOS.TM. N-3 acid) or dextran 500k. Other suitable
examples of the anti-kogation agents include CRODAFOS.TM. HCE
(phosphate-ester from Croda Int.), CRODAFOS.RTM. N10
(oleth-10-phosphate from Croda Int.), or DISPERSOGEN.RTM. LFH
(polymeric dispersing agent with aromatic anchoring groups, acid
form, anionic, from Clariant), etc. The anti-kogation agent may be
present in the gas generating liquid functional agent in an amount
ranging from about 0.1 wt % to about 1 wt % of the total weight of
the gas generating liquid functional agent.
[0050] In some examples, the balance of the gas generating liquid
functional agent is water (e.g., deionized water). In these
examples, the amount of water may vary depending upon the weight
percent of the other gas generating liquid functional agent
components. In other examples, the balance of the gas generating
liquid functional agent is a solvent (e.g., any of the previously
listed co-solvents).
[0051] An example formulation of the gas generating liquid
functional agent that does not include a binder, and thus may be
used in combination with a separate binding agent, is shown in
Table 1. This example includes calcium carbonate as the gas
precursor compound.
TABLE-US-00001 TABLE 1 Component Actives Target Formulation Type
Specific Components (wt %) (wt %) (wt %) Co-solvent
1-(2-Hydroxyethyl)-2- 100.00 20.00 20.00 pyrrolidone (HE-2P)
Surfactant/ Silquest .TM. 100.00 5.00 5.00 Dispersing aid Momentive
A-1230 Surfynol .RTM. 465 100.00 0.40 0.40 Antimicrobial Acticide
.RTM. M20 10.00 0.01 0.10 (stock solution) Gas Precursor Calcium
carbonate 32.00 20.00 62.50 Compound (CaCO.sub.3) 50 nm- 100 nm
dispersion Water Deionized Water -- -- Balance
[0052] As mentioned herein, other examples of the gas generating
liquid functional agent are combined agents that may be used to
pattern build material to form the patterned breakable connection
without using a separate binding agent. In these other examples,
the gas generating liquid functional agent (or combined agent)
includes the binder, the gas precursor, water or a solvent,
co-solvent(s), and surfactant(s) and/or dispersing aid(s), and in
some instances, may also include antimicrobial agent(s) and/or
anti-kogation agent(s). In these examples, any of the previously
described gas precursors, co-solvent(s), surfactant(s) and/or
dispersing aid(s), antimicrobial agent(s), and/or anti-kogation
agent(s) may be used in any of the given amounts.
[0053] Examples of suitable binders include latexes (i.e., an
aqueous dispersion of polymer particles), polyvinyl alcohol,
polyvinylpyrrolidone, and combinations thereof.
[0054] Examples of polyvinyl alcohol include low weight average
molecular weight polyvinyl alcohols (e.g., from about 13,000 to
about 50,000), such as SELVOL.TM. PVOH 17 from Sekisui. Examples of
polyvinylpyrrolidones include low weight average molecular weight
polyvinylpyrrolidones (e.g., from about 15,000 to about 19,000),
such as LUVITEC.TM. K 17 from BASF Corp.
[0055] The polymer particles of the latex may have several
different morphologies. For example, the polymer particles may be
individual spherical particles containing polymer compositions of
hydrophilic (hard) component(s) and/or hydrophobic (soft)
component(s) that may be interdispersed according to IPN
(interpenetrating networks), although it is contemplated that the
hydrophilic and hydrophobic components may be interdispersed in
other ways. For another example, the polymer particles may be made
of a hydrophobic core surrounded by a continuous or discontinuous
hydrophilic shell. For another example, the polymer particle
morphology may resemble a raspberry, in which a hydrophobic core is
surrounded by several smaller hydrophilic particles that are
attached to the core. For still another example, the polymer
particles may include 2, 3, or 4 particles that are at least
partially attached to one another.
[0056] The latex polymer particles may have a weight average
molecular weight ranging from about 5,000 to about 500,000. As
examples, the weight average molecular weight of the latex
particles may range from about 100,000 to about 500,000, or from
about 150,000 to about 300,000.
[0057] Latex particles may include a heteropolymer including a
hydrophobic component that makes up from about 65% to about 99.9%
(by weight) of the heteropolymer, and a hydrophilic component that
makes up from about 0.1% to about 35% (by weight) of the
heteropolymer, where the hydrophobic component may have a lower
glass transition temperature than the hydrophilic component. In
general, a lower content of the hydrophilic component is associated
with easier use of the latex particles under typical ambient
conditions. As used herein, typical ambient conditions include a
temperature range from about 20.degree. C. to about 25.degree. C.,
an atmospheric pressure of about 100 kPa (kilopascals), and a
relative humidity ranging from about 30% to about 90%. The glass
transition temperature of the latex particles may range from about
-20.degree. C. to about 130.degree. C., or in a specific example,
from about 60.degree. C. to about 105.degree. C.
[0058] Examples of monomers that may be used to form the
hydrophobic component include C.sub.1 to C.sub.8 alkyl acrylates or
methacrylates, styrene, substituted methyl styrenes, polyol
acrylates or methacrylates, vinyl monomers, vinyl esters, ethylene,
maleate esters, fumarate esters, itaconate esters, or the like.
Some specific examples include methyl methacrylate, butyl acrylate,
butyl methacrylate, hexyl acrylate, hexyl methacrylate, ethyl
acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate,
2-ethylhexyl acrylate, 2-ethylhexy methacrylate, hydroxyethyl
acrylate, lauryl acrylate, lauryl methacrylate, octadecyl acrylate,
octadecyl methacrylate, isobornyl acrylate, isobornyl methacrylate,
stearyl methacrylate, ethylene glycol dimethacrylate, diethylene
glycol dimethacrylate, triethylene glycol dimethacrylate,
tetrahydrofurfuryl acrylate, alkoxylated tetrahydrofurfuryl
acrylate, 2-phenoxyethyl methacrylate, benzyl acrylate, ethoxylated
nonyl phenol methacrylate, cyclohexyl methacrylate, trimethyl
cyclohexyl methacrylate, t-butyl methacrylate, n-octyl
methacrylate, tridecyl methacrylate, isodecyl acrylate, dimethyl
maleate, dioctyl maleate, acetoacetoxyethyl methacrylate, diacetone
acrylamide, pentaerythritol tri-acrylate, pentaerythritol
tetra-acrylate, pentaerythritol tri-methacrylate, pentaerythritol
tetra-methacrylate, divinylbenzene, styrene, methylstyrenes (e.g.,
.alpha.-methyl styrene, p-methyl styrene), 1,3-butadiene, vinyl
chloride, vinylidene chloride, vinylbenzyl chloride, acrylonitrile,
methacrylonitrile, N-vinyl imidazole, N-vinylcarbazole,
N-vinyl-caprolactam, combinations thereof, derivatives thereof, or
mixtures thereof.
[0059] The heteropolymer may be formed of at least two of the
previously listed monomers, or at least one of the previously
listed monomers and a higher T.sub.g hydrophilic monomer, such as
an acidic monomer. Examples of acidic monomers that can be
polymerized in forming the latex polymer particles include acrylic
acid, methacrylic acid, ethacrylic acid, dimethylacrylic acid,
maleic anhydride, maleic acid, vinylsulfonate, cyanoacrylic acid,
vinylacetic acid, allylacetic acid, ethylidineacetic acid,
propylidineacetic acid, crotonoic acid, fumaric acid, itaconic
acid, sorbic acid, angelic acid, cinnamic acid, styrylacrylic acid,
citraconic acid, glutaconic acid, aconitic acid, phenylacrylic
acid, acryloxypropionic acid, aconitic acid, phenylacrylic acid,
acryloxypropionic acid, vinylbenzoic acid, N-vinylsuccinamidic
acid, mesaconic acid, methacroylalanine, acryloylhydroxyglycine,
sulfoethyl methacrylic acid, sulfopropyl acrylic acid, styrene
sulfonic acid, sulfoethylacrylic acid,
2-methacryloyloxymethane-1-sulfonic acid,
3-methacryoyloxypropane-1-sulfonic acid,
3-(vinyloxy)propane-1-sulfonic acid, ethylenesulfonic acid, vinyl
sulfuric acid, 4-vinylphenyl sulfuric acid, ethylene phosphonic
acid, vinyl phosphoric acid, vinyl benzoic acid, 2
acrylamido-2-methyl-1-propanesulfonic acid, combinations thereof,
derivatives thereof, or mixtures thereof. Other examples of high
T.sub.g hydrophilic monomers include acrylamide, methacrylamide,
monohydroxylated monomers, monoethoxylated monomers,
polyhydroxylated monomers, or polyethoxylated monomers.
[0060] In examples, the aqueous dispersion of polymer particles
(latexes) may be produced by emulsion polymerization or
co-polymerization of any of the previously listed monomers. Other
suitable techniques, specifically for generating a core-shell
structure, may be used, such as: i) grafting a hydrophilic shell
onto the surface of a hydrophobic core, ii) copolymerizing
hydrophobic and hydrophilic monomers using ratios that lead to a
more hydrophilic shell, iii) adding hydrophilic monomer (or excess
hydrophilic monomer) toward the end of the copolymerization process
so there is a higher concentration of hydrophilic monomer
copolymerized at or near the surface, or iv) any other method known
in the art to generate a more hydrophilic shell relative to the
core.
[0061] In an example, the binder is present in the combined agent
in an amount ranging from about 1 wt % to about 30 wt % based on a
total weight of the combined agent. In another example, the binder
is present in the combined agent in an amount ranging from about 2
wt % to about 25 wt % based on the total weight of combined agent.
As shown in Table 2 below, these percentages may include both
active binder and other non-active components present with the
binder.
[0062] In examples of the combined agent, it is desirable that the
total volume fraction of solids be about 50 vol. % or less, so that
the combined agent is jettable via the desired inkjet printhead
(e.g., thermal inkjet printhead, piezoelectric inkjet printhead,
etc.). As such, the volume fraction of the gas precursor compound
and the binder may be adjusted so that together, the components do
not exceed, for example, from about 40 vol. % to about 50 vol. % of
the total volume of the combined agent.
[0063] An example formulation of the gas generating liquid
functional agent that does include a binder, and thus may be used
without a separate binding agent, is shown in Table 2. This example
includes calcium carbonate as the gas precursor compound.
TABLE-US-00002 TABLE 2 Component Actives Target Formulation Type
Specific Components (wt %) (wt %) (wt %) Co-solvent 2-methyl-1,3-
99.00 9.60 9.70 propanediol 2-pyrrolidinone 95.00 17.00 17.89
Surfactant/ Tergitol .RTM. 15-S-7 100.00 0.90 0.90 Dispersing aid
Antimicrobial Acticide .RTM. M20 10.00 0.01 0.10 (stock solution)
Gas Precursor Calcium carbonate 32.00 15.00 46.88 Compound
(CaCO.sub.3) 50 nm- 100 nm dispersion Binder Acrylic latex 41.40
9.00 21.74 dispersion Water Deionized Water -- -- 2.79
[0064] Binding Liquid Functional Agent
[0065] The binding liquid functional agent (i.e., binding agent)
may be used to pattern build material where it is desirable to form
the 3D object and where it is desirable to form the 3D support
structure. The binding agent may also be used in combination with
examples of the gas generating liquid functional agent that do not
include a binder to pattern build material where it is desirable to
form the irreversibly breakable connection.
[0066] The binding agent includes the binder. Any of the binders
set forth herein for examples of the combined agent may be used in
the binding agent. In an example, the binder is present in the
binding agent in an amount ranging from about 1 wt % to about 30 wt
% based on a total weight of the binding agent. In another example,
the binder is present in the binding agent in an amount ranging
from about 2 wt % to about 20 wt % based on the total weight of
binding agent. These percentages may include active binder, and the
percentages may be higher when other non-active components are
considered (e.g., in Table 3).
[0067] In addition to the binder, the binding agent may also
include water, co-solvent(s), surfactant(s) and/or dispersing
aid(s), antimicrobial agent(s), and/or anti-kogation agent(s). In
these examples, any of the previously described co-solvent(s),
surfactant(s) and/or dispersing aid(s), antimicrobial agent(s),
and/or anti-kogation agent(s) may be used in any of the given
amounts, except that the weight percentages are with respect to a
total weight of the binding agent.
[0068] The composition of the binding liquid functional agent is
similar to examples of the gas generating liquid functional agent
except that the gas precursor compound(s) is excluded from the
formulation of the binding liquid functional agent.
[0069] An example formulation of the binding liquid functional
agent is shown in Table 3.
TABLE-US-00003 TABLE 3 Component Actives Target Formulation Type
Components (wt %) (wt %) (wt %) Co-solvent 2-methyl-1,3- 99.00 9.60
9.70 propanediol 2-pyrrolidinone 95.00 17.00 17.89 Surfactant/
Tergitol .RTM. 15-S-7 100.00 0.90 0.90 Dispersing aid Antimicrobial
Acticide .RTM. M20 10.00 0.01 0.1 (stock solution) Binder Acrylic
latex 41.40 16.00 38.65 dispersion Water Deionized Water -- --
Balance
[0070] Methods
[0071] An example of the 3D printing method 100, in which a gas
generating liquid functional agent and a binding agent are used, is
depicted in FIG. 1. Generally, the method 100 includes patterning
build material layers to form an intermediate structure, the
patterning including: selectively applying a binding agent to
define: a build material support structure and a patterned
intermediate part; and selectively applying i) the binding agent
and a separate agent including a gas precursor or ii) a combined
agent including a binder and the gas precursor to define a
patterned breakable connection between at least a portion of the
build material support structure and at least a portion of the
patterned intermediate part (reference numeral 102); and heating
the intermediate structure to a temperature that activates the gas
precursor to create gas pockets in the patterned breakable
connection (reference numeral 104).
[0072] Any examples of the build material, the binding agent, and
the gas generating liquid functional agent described herein may be
used in the method 100. Furthermore, the method 100 may be used to
form 3D objects, 3D support structures, and irreversibly breakable
connections of any size and/or shape, as long as the irreversibly
breakable connection is located between at least a portion of the
3D object and the 3D support structure, and provides a breakable
junction between the 3D object and the 3D support structure.
[0073] At reference numeral 102 in FIG. 1, build material layers
are patterned to form the intermediate structure, which is
ultimately heated to form the 3D object, 3D support structure, and
irreversibly breakable connection. FIGS. 2A through 2D depict
various examples of the intermediate structures 40A, 40B, 40C, 40D
that may be made using the method 100.
[0074] In an example, patterning the build material layers
includes: iteratively applying individual build material layers 12,
12A, 12B, etc.; selectively applying the binding agent to at least
some, or to each, of the individual build material layers to define
several layers of the build material support structure 23 and
several layers of the patterned intermediate part 25; and
selectively applying i) the binding agent and the separate agent or
ii) the combined agent on each of the individual build material
layers to define the patterned breakable connection between the
several layers of the build material support structure 23 and the
several layers of the patterned intermediate part 25. In some
examples (e.g., FIGS. 2A and 2D), the patterned breakable
connection 23 alone separates the build material support structure
23 from the patterned intermediate part 25, and in other examples
(e.g., FIGS. 2B and 2C), one or more layers of non-patterned build
material 28 and the patterned breakable connection 23 separate the
build material support structure 23 from the patterned intermediate
part 25.
[0075] In the examples shown in FIGS. 2A through 2D, several build
material layers 12, 12A, 12B . . . 12H (FIG. 2A), etc. have been
applied and patterned to define different examples of the build
material support structure 23, the patterned intermediate part 25,
and the patterned breakable connection 32. Repeated application and
patterning may be performed until the total number of build
material layers that are patterned form a complete build material
support structure 23 according to a 3D model of the 3D support
structure, a complete patterned intermediate part 25 according to a
3D model of the 3D object, and a complete patterned breakable
connection 32 according to a 3D model of the irreversibly breakable
connection.
[0076] The build material 14 may be spread to form the layers 12,
12A, 12B, etc. on a build area platform 16, and the respective
layers 12, 12A, 12B, etc. may be patterned with the binding agent
and/or an example of the gas generating liquid functional agent one
layer at a time. Examples of the spreading of the build material 14
and the application of the various agents to pattern are described
in more detail in reference to FIGS. 4A-4J. The agent(s) used to
pattern any individual build material layer 12, 12A, 12B, etc. will
depend upon whether the patterned portion is part of the build
material support structure 23, the patterned intermediate part 25,
or the patterned breakable connection 32. The binding agent is used
to pattern the build material support structure 23 and the
patterned intermediate part 25, and either i) the binding agent and
the separate agent including the gas precursor or ii) the combined
agent including both the binder and the gas precursor is used to
pattern the patterned breakable connection 32.
[0077] As shown in FIGS. 2A through 2C, the patterned breakable
connection 32 is defined between at least a portion of the build
material support structure 23 and the patterned intermediate part
25. In these examples, the build material support structure 23
provides support for at least some of the build material 14 of the
patterned intermediate part 25 during the patterning process and
during the subsequent heating process. Also in these examples, the
patterned intermediate part 25 at least partially overlies the
build material support structure 23.
[0078] In the example shown in FIG. 2A, the patterned breakable
connection 32 is built up vertically between one surface of the
build material support structure 23 and one surface of the
patterned intermediate part 25, and then is curved so that it
overlies a portion of the build material support structure 23. In
this example, the build material support structure 23 provides
support at least for the curved portion of the patterned
intermediate part 25. To form this intermediate structure 40A, the
binder agent is selectively applied on layers 12 through 12H to
define the patterned intermediate part 25; the binder agent is
selectively applied on layers 12 through 12D to define the build
material support structure 23; and either i) the binding agent and
the separate agent including the gas precursor or ii) the combined
agent is selectively applied on layers 12 through 12E to define the
patterned breakable connection 32.
[0079] In the example shown in FIG. 2B, the patterned breakable
connection 32 is horizontally defined between one surface of the
build material support structure 23 and one surface of the
patterned intermediate part 25. In this example, the patterned
breakable connection 32 completely overlies the build material
support structure 23, which provides support for the overlying
portion of the patterned intermediate part 25. To form this
intermediate structure 40B, the binder agent is selectively applied
on layers 12 through 12W to define the patterned intermediate part
25; the binder agent is selectively applied on layers 12 through
12R to define the build material support structure 23; and either
i) the binding agent and the separate agent including the gas
precursor or ii) the combined agent is selectively applied on
layers 12S and 12T to define the patterned breakable connection 32.
Also in this example, some of the build material 14 between the
patterned intermediate part 25 and the build material support
structure 23 remains non-patterned (shown at reference numeral 28).
The non-patterned build material 28 can be easily removed after
patterning and before heating, and thus can create a space between
the patterned intermediate part 25 and the build material support
structure 23.
[0080] In the example shown in FIG. 2C, the patterned breakable
connection 32 is built up vertically between one surface of the
build material support structure 23 and a portion of one surface of
the patterned intermediate part 25. To form this intermediate
structure 40C, the binder agent is selectively applied on layers 12
through 12H to define the patterned intermediate part 25; the
binder agent is selectively applied on layers 12C through 12E to
define the build material support structure 23; and either i) the
binding agent and the separate agent including the gas precursor or
ii) the combined agent is selective applied on layers 12C through
12E to define the patterned breakable connection 32. Also in this
example, some of the build material 14 between the patterned
intermediate part 25 and the build material support structure 23
remains non-patterned 28, and thus can create spaces between the
patterned intermediate part 25 and the build material support
structure 23. In this example, the build material support structure
23, in combination with the non-patterned build material 28,
provides support for the overlying portion of the patterned
intermediate part 25 formed thereon during patterning.
[0081] In the example shown in FIG. 2C, the intermediate structure
40C can be extracted from any non-patterned build material 14, 28
surrounding the structure 40C and in the spaces, and then rotated
(e.g., 90.degree.) so that the build material support structure 23
contacts a surface of a heating mechanism and so that the curved
center portion of the horseshoe or C-shaped part is substantially
parallel to the surface of the heating mechanism. In these
examples, the build material support structure 23 provides support
for a different portion of the patterned intermediate part 25
during heating than during patterning.
[0082] As shown in FIG. 2D, the patterned breakable connection 32
is defined between the build material support structure 23 and the
patterned intermediate part 25. In this example, the patterned
breakable connection 32 is at least partially perpendicular to the
build area platform 16. In this and other similar examples, the
build material support structure 23 may be next to the patterned
breakable connection 32, which is next to the patterned
intermediate part 25 on the build area platform 16. In these
examples, there is no non-patterned build material 28 between the
build material support structure 23 and the patterned intermediate
part 25, and the patterned intermediate part 25 does not overly the
build material support structure 23 during patterning.
[0083] In the example shown in FIG. 2D, the intermediate structure
40D can be extracted from any non-patterned build material 14, 28
surrounding the structure 40D, and then rotated (e.g., 90.degree.)
so that the build material support structure 23 contacts a surface
of a heating mechanism and the patterned breakable connection 32 is
at least partially parallel to the surface of the heating
mechanism. In these examples, the build material support structure
23 provides support for the patterned intermediate part 25 during
heating, but not during the printing/patterning process.
[0084] Several examples of the intermediate structure 40 and the
patterned breakable connection 32 have been illustrated in FIGS. 2A
through 2D. It is to be understood that the components 23, 25, 32
of the intermediate structure 40 may have other configurations, as
long as the geometry of the irreversibly breakable connection can
be broken to separate the 3D object from the 3D support
structure.
[0085] Another, more specific example of the 3D printing method,
shown at reference numeral 200, is depicted in FIG. 3. Generally,
the method 200 includes patterning a build material layer by
selectively applying a binding agent to define: a layer of a build
material support structure and a layer of a patterned intermediate
part separated by non-patterned build material (reference numeral
202); applying another layer of build material on the patterned
build material layer (reference numeral 204); patterning the other
layer of build material by: selectively applying i) the binding
agent and a separate agent including a gas precursor or ii) a
combined agent including a binder and the gas precursor on a
portion of the other layer of build material that overlies the
build material support structure, thereby forming a patterned
breakable connection (reference numeral 206); selectively applying
the binding agent on another portion of the other layer of build
material to define an outer layer of a region of the patterned
intermediate part (reference numeral 208); forming a remaining
region of the patterned intermediate part on the patterned
breakable connection and in contact with the region of the
patterned intermediate part, thereby forming an intermediate
structure including the patterned intermediate part and the build
material support structure temporarily bound together at the
patterned breakable connection (reference numeral 210); and heating
the intermediate structure to a temperature that activates the gas
precursor to create gas pockets in the patterned breakable
connection (reference numeral 212).
[0086] Any examples of the build material, the binding agent, and
the gas generating liquid functional agent described herein may be
used in the method 200.
[0087] It is to be understood that the method 200 shown in FIG. 3
will be discussed in detail in conjunction with FIGS. 4A through
4J, and FIG. 5.
[0088] As shown in reference numeral 202, the method 200 includes
patterning a build material layer by selectively applying a binding
agent to define a layer of a build material support structure and a
layer of a patterned intermediate part, where the patterned layers
are separated by non-patterned build material. An example of the
patterning of the build material layer is shown in cross-section in
FIG. 4A. Prior to patterning, build material particles 14 may be
applied to form a build material layer 12, and then the layer 12
may be patterned. In the example shown in FIG. 4A, one build
material layer 12 including build material particles 14 has been
deposited on (i.e., applied to, formed on, etc.) a build area
platform 16 and patterned.
[0089] Forming and patterning the build material layer 12 may
include the use of a printing system (an example of which is shown
at reference numeral 60 in FIG. 5). The printing system 60 may
include the build area platform 16, a build material supply 11
containing build material particles 14, a build material
distributor 13, and an applicator 17.
[0090] The build area platform 16 receives the build material
particles 14 from the build material supply 11. The build area
platform 16 may be moved in the directions as denoted by the arrow
15 (FIG. 5), e.g., along the z-axis, so that the build material
particles 14 may be delivered to the build area platform 16 or to a
previously patterned layer (see, e.g., FIG. 4C). In an example,
when the build material particles 14 are to be delivered, the build
area platform 16 may be programmed to advance (e.g., downward)
enough so that the build material distributor 13 can push the build
material particles 14 onto the build area platform 16 to form a
substantially uniform build material layer 12 thereon. The build
area platform 16 may also be returned to its original position, for
example, when a new object is to be built.
[0091] The build material supply 11 may be a container, bed, or
other surface that is to position the build material particles 14
between the build material distributor 13 and the build area
platform 16.
[0092] The build material distributor 13 may be moved in the
directions as denoted by the arrow 15' (FIG. 5), over the build
material supply 11 and across the build area platform 16 to spread
the build material particles 14 over the build area platform 16.
The build material distributor 13 may also be returned to a
position adjacent to the build material supply 11 following the
spreading of the build material particles 14. The build material
distributor 13 may be a blade (e.g., a doctor blade), a roller, a
combination of a roller and a blade, and/or any other device
capable of spreading the build material 16 over the build area
platform 16. For instance, the build material distributor 13 may be
a counter-rotating roller. In some examples, the build material
supply 11 or a portion of the build material supply 11 may
translate along with the build material distributor 13 such that
build material particles 14 are delivered continuously to the
material distributor 13, rather than being supplied from a single
location (as shown in FIG. 5).
[0093] A controller (shown as 62 in FIG. 5) may process build
material supply data, and in response, may control the build
material supply 11 to appropriately position the build material
particles 14, and may process spreader data, and in response, may
control the build material distributor 13 to spread the supplied
build material particles 14 over the build area platform 16 to form
the build material layer 12 thereon. As shown in FIG. 4A, one build
material layer 12 has been formed. The layers 12, 12A, etc. shown
in FIGS. 2A through 2D may be formed in a similar manner.
[0094] The build material layer 12 has a substantially uniform
thickness across the build area platform 16. In an example, the
thickness of the build material layer 12 ranges from about 90 .mu.m
to about 110 .mu.m, although thinner or thicker layers may be used.
For example, the thickness of the build material layer 12 may range
from about 50 .mu.m to about 200 .mu.m. In another example, the
thickness of the build material layer 12 ranges from about 30 .mu.m
to about 300 .mu.m. In yet another example, the thickness of the
build material layer 12 may range from about 20 .mu.m to about 500
.mu.m. The layer 12 thickness may be about 2.times. (i.e., 2 times)
the particle diameter at a minimum for finer part definition. In
some examples, the layer 12 thickness may be about 1.2.times. the
particle diameter.
[0095] A binding agent 18 is selectively applied to different
portions of the build material layer 12 in order to pattern the
layer 12. The different portions 20, 24 of the build material layer
12 to which the binding agent 18 is selectively applied may be
respectively defined by a 3D model of the support structure that is
to be formed and a 3D model of the 3D object that is to be formed.
In FIG. 4A, the binding agent 18 is selectively applied to the
portion/area 20 of the build material layer 12 to define one
patterned layer 22 (shown in FIG. 4B) of a build material support
structure 23 (shown in FIG. 4D), and the binding agent 18 is
selectively applied to the portion(s)/area(s) 24 of the build
material layer 12 to define one patterned layer 26 (shown in FIG.
4B) of a patterned intermediate part 25 (shown in FIG. 4F).
[0096] The applicator 17 may be used to selectively apply the
binding agent 18. The applicator 17 may include nozzles, fluid
slots, and/or fluidics for dispensing the binding agent 18. The
applicator 17 may be a thermal inkjet printhead or print bar, a
piezoelectric printhead or print bar, or a continuous inkjet
printhead or print bar. While a single applicator 17 is shown in
FIG. 4B, it is to be understood that multiple applicators 17 may be
used.
[0097] The applicator 17 may be scanned across the build area
platform 16, for example, in the directions as denoted by the arrow
15'' in FIG. 5. The applicator 17 may extend a width of the build
area platform 16. The applicator 17 may also be scanned along the
x-axis, for instance, in configurations in which the applicator 17
does not span the width of the build area platform 16 to enable the
applicator 17 to deposit the binding agent 18 over a large area of
a build material layer 12. The applicator 17 may thus be attached
to a moving XY stage or a translational carriage that moves the
applicator 17 adjacent to the build area platform 16 in order to
deposit the binding agent 18 in predetermined areas 20, 24 of the
build material layer 12.
[0098] The applicator 17 may deliver drops of the binding agent 18
at a resolution ranging from about 300 dots per inch (DPI) to about
1200 DPI. In other examples, the applicator 17 may deliver drops of
the binding agent 18 at a higher or lower resolution. The drop
velocity may range from about 5 m/s to about 24 m/s and the firing
frequency may range from about 1 kHz to about 100 kHz. In one
example, the volume of each drop may be in the order of about 3
picoliters (pl) to about 18 pl, although it is contemplated that a
higher or lower drop volume may be used. In some examples, the
applicator 17 is able to deliver variable drop volumes of the
binding agent 18. One example of a suitable printhead has 600 DPI
resolution and can deliver drop volumes ranging from about 6 pl to
about 14 pl.
[0099] The binding agent 18 is deposited interstitially in the
openings or voids between the build material particles 14.
Capillary flow can move the binding agent 18 between the individual
build material particles 14 in the areas 20, 24.
[0100] In this example, it is desirable for the patterned layers
22, 26 to be separated by non-patterned build material 28, (i.e.,
particles 14 without any binding agent 18 applied thereto) so that
the layers 22, 26 are not in direct contact with one another. The
non-patterned build material 28 is not intended to be used in
forming the build material support structure 23 or the patterned
intermediate part 25. In this example, as shown in FIGS. 4A and 4B,
some of the non-patterned build material 28 is located at the outer
edges of the patterned layer 26 of the patterned intermediate part
25. The build material particles 14 that are directly adjacent to
the edges of the build area platform 16 may be exposed to a
different environment (a metal wall, air, etc.) than the build
material particles 14 that are surrounded by other build material
particles 14. The different environment can lead to non-uniformity
at the edges. As such, it may be desirable to have non-patterned
build material 28 at the outer edges of the patterned layer 26.
[0101] Referring specifically now to FIG. 4B, the selective
application of the binding agent 18 onto the build material
particles 14 within the area 24 results in the formation of a
patterned layer 26, which is to become part of a patterned
intermediate part 25 (FIG. 4F), which is ultimately to be sintered
to form the 3D object/part. More particularly, in the example shown
in FIG. 4B, the patterned layer 26 is the first layer of the 3D
object being formed. Similarly, as shown in FIG. 4B, the selective
application of the binding agent 18 onto the build material
particles 14 within the area 20 results in the formation of a
patterned layer 22, which is to become part of the build material
support structure 23 (FIG. 4D). More particularly, in the example
shown in FIG. 4B, the patterned layer 22 is the first layer of the
build material support structure 23 being formed.
[0102] In examples of the method 200 where the build material
support structure 23 is a single layer, the method 200 may continue
with reference numerals 204 and 206 of FIG. 3. In other examples,
the build material support structure 23 (FIG. 3D) is a multi-layer
structure, and thus the method 200 may further include iteratively
applying additional build material layers (e.g., 12A, 12B, 12C,
shown in FIG. 4C) and selectively applying the binding agent 18 to
the additional build material layers 12A, 12B, 12C to define
several layers of the build material support structure 23 and
several layers of a region 27 of the patterned intermediate part
25, wherein the several layers of the build material support
structure 23 and the several layers of the region 27 of the
patterned intermediate part 25 are separated by additional
non-patterned build material 28.
[0103] FIG. 4C depicts the repeated application of build material
particles 14 to form the other build material layers 12A, 12B, 12C
and the repeated patterning of these additional build material
layers 12A, 12B, 12C over the first layer 12 of patterned build
material. As mentioned above and as shown in FIG. 4D, repeated
application and patterning may be performed to iteratively build
additional layers of the build material support structure 23, as
well as additional layers of the region 27 of the patterned
intermediate part 25. Repeated application and patterning may be
performed until the total number of build material layers 30 that
are patterned form a complete build material support structure 23
according to a 3D object model of a 3D support structure 48 (FIG.
4I). As such, the total number of build material layers 30 that are
patterned will depend on the desired dimensions of the build
material support structure 23 and the ultimately formed 3D support
structure 48. In the example depicted in FIGS. 4C and 4D, four
build material layers 12, 12A, 12B, 12C are applied and patterned
to form the complete build material support structure 23.
[0104] As shown in reference numerals 204, 206, and 208 of FIG. 3
and in FIGS. 4D and 4E, after the desired total number of build
material layers 30 are patterned to form the build material support
structure 23, the method 200 continues by applying another layer of
build material 12D (reference numeral 204), and patterning this
other build material layer 12D. Patterning the layer 12D may be
accomplished by selectively applying (i) the binding agent 18 and a
separate agent 21 including a gas precursor and not including a
binder (i.e., one example of the gas generating liquid functional
agent disclosed herein), or (ii) a combined agent 19 including the
binder and the gas precursor (i.e., another example of the gas
generating liquid functional agent disclosed herein) on a portion
of the other layer 12D of build material that overlies the build
material support structure 23, thereby forming a patterned
breakable connection 32 (reference numeral 206); and selectively
applying the binding agent 18 on another portion of the other layer
12D of build material to define an outer layer 34 of the region 27
of the patterned intermediate part 25 (reference numeral 208).
[0105] Any example of the binding agent 18 described herein may be
utilized in combination with any example of the separate gas
generating liquid functional agent 21 that does not include a
binder in order to define the patterned breakable connection 32.
The binder from the binding agent 18 can temporarily bind the build
material particles 14 of the patterned breakable connection 32 and
the gas precursor of the separate gas generating liquid functional
agent 21 forms gas pockets 36 (FIGS. 4H and 4I) within the
irreversibly breakable connection 38 (FIG. 4I) that is formed
during sintering.
[0106] When the agents 18 and 21 are used to define the patterned
breakable connection 32, the binding agent 18 may be dispensed from
the applicator 17, and the separate gas generating liquid
functional agent 21 may be dispensed from a separate applicator.
The separate applicator may be similar to applicator 17 (i.e., may
be a thermal inkjet printhead, a piezoelectric printhead, etc.),
and may be operated in the same manner as previously described
herein. In another example, the applicator 17 may have separate
chambers that contain the binding agent 18 and the separate gas
generating liquid functional agent 21, and may also have separate
printheads, nozzles, etc. to separately and selectively dispense
the two agents 18, 21. In these examples, the applicator(s) may be
programmed to receive commands from the controller 62 and to
deposit the agents 18 and 21 according to a 3D object model of the
irreversibly breakable connection 38. In the example shown in FIG.
2D, the applicator(s) sequentially or simultaneously apply the
agents 18 and 21 to the build material particles 14 of the layer
12D which overly the build material support structure 23. This
defines the patterned breakable connection 32 on a surface of the
build material support structure 23. The agents 18 and 21 are
deposited interstitially in the openings or voids between the build
material particles 14. Capillary flow can move the agents 18 and 21
between the individual build material particles 14 in the layer
12D.
[0107] Alternatively, any example of the combined agent 19,
including both the binder and the gas precursor, may be used to
define the patterned breakable connection 32. When the combined
agent 19 is used, a separate binding agent 18 is not utilized to
define the patterned breakable connection 32. In these examples,
the binder from the combined agent 19 can temporarily bind the
build material particles 14 of the patterned breakable connection
32 and the gas precursor of the combined agent 19 forms gas pockets
36 (FIGS. 4H and 4I) within the irreversibly breakable connection
38 (FIG. 4I) that is formed during sintering.
[0108] When the combined agent 19 is used to define the patterned
breakable connection 32, the combined agent 19 may be dispensed
from an applicator that is similar to applicator 17 (i.e., may be a
thermal inkjet printhead, a piezoelectric printhead, etc.), and
that may be operated in the same manner as previously described
herein for the applicator 17. In another example, the applicator 17
may have separate chambers that contain the combined agent 21 and
the binding agent 18 (e.g., used to pattern the build material
support structure 23 and the patterned intermediate part 25), and
may also have separate printheads, nozzles, etc. for separately and
selectively dispensing the two agents 19, 18. In these examples,
the applicator may be programmed to receive commands from the
controller 62 and to deposit the combined agent 19 according to a
3D object model of the irreversibly breakable connection 38. In the
example shown in FIG. 4D, the applicator applies the agent 19 to
the build material particles 14 of the layer 12D which overly the
build material support structure 23. This defines the patterned
breakable connection 32 on a surface of the build material support
structure 23. The combined agent 19 is deposited interstitially in
the openings or voids between the build material particles 14.
Capillary flow can move the agent 19 between the individual build
material particles 14 in the layer 12D.
[0109] Also in the example shown in FIG. 4D, the applicator 17
selectively applies the binding agent 18 on those portion(s) of the
build material layer 12D in order to define the outer layer 34 of
the region 27 of the patterned intermediate part 25. In these
examples, the applicator 17 may be programmed to receive commands
from the controller 62 and to deposit the binding agent 18
according to a 3D object model of the 3D object being formed.
[0110] As shown at reference numeral 210 in FIG. 3 and in FIGS. 4E
and 4F, the method 200 further includes forming a remaining region
29 of the patterned intermediate part 25 on the patterned breakable
connection 32 and in contact with the (previously patterned) region
27 of the patterned intermediate part 25, thereby forming an
intermediate structure 40 including the patterned intermediate part
25 and the build material support structure 23, temporarily bound
together at the patterned breakable connection 32. The remaining
region 29 of the patterned intermediate part 25 is formed by
applying a further layer 12E of build material on the patterned
breakable connection 32 and the outer layer 34 of the region 27 of
the patterned intermediate part 25, and selectively applying the
binding agent 18 to the further layer 12E to define a patterned
layer 42 of the remaining region 29 of the patterned intermediate
part 25. This patterned layer 42 of the remaining region 29 is in
direct contact with at least some of the region 27, so that the two
regions 27, 29 can be sintered together to form the 3D object.
Moreover, this patterned layer 42 of the remaining region 29
overlies the patterned breakable connection 32 and the support
structure 23, both of which provide physical support to the
patterned layer 42 and any other layers applied and patterned to
form the remaining region 29.
[0111] In examples of the method 200 where the remaining region 29
is a single layer, the method 200 may continue with reference
numeral 212 of FIG. 3. In other examples, the remaining region 29
(FIG. 4F) is a multi-layer structure, and thus the method 100 may
further include iteratively applying additional build material
layers (e.g., 12E, 12F, 12G, 12H shown in FIG. 4F) and selectively
applying the binding agent 18 to the additional build material
layers 12E, 12F, 12G, 12H to define several layers of the remaining
region 29 of the patterned intermediate part 25.
[0112] After the layer(s) 12E, 12F, 12G, 12H of the remaining
region 29 are patterned, the intermediate structure 40 is formed.
The intermediate structure 40 is similar to intermediate structures
40, 40A, 40B, 40C, or 40D, in that each of the structures 40, 40A,
40B, 40C, 40D includes the patterned intermediate part 25, the
build material support structure 23, and the patterned breakable
connection 32 which temporarily binds the patterned intermediate
part 25 and the build material support structure 23. As such, the
following discussion of evaporation and heating may be applicable
for both methods 100 and 200, and for any intermediate structure
40, 40A, 40B, 40C, 40D that may be formed.
[0113] In any of the examples disclosed herein, the intermediate
structure 40, 40A, 40B, 40C, 40D may be part of a build material
cake including the intermediate structure 40, 40A, 40B, 40C, 40D
and any non-patterned build material 28. In the example shown in
FIG. 4F, the non-patterned build material 28 may be positioned
between surfaces of the patterned intermediate part 25 and surfaces
of the build material support structure 23 and/or surrounding the
patterned intermediate part 25.
[0114] During and/or after the formation of the intermediate
structure 40, 40A, 40B, 40C, 40D, the liquid components of the
binding agent 18, and the separate agent 21 or the combined agent
19 may be at least substantially evaporated to form a densified
intermediate part 25', a densified build material support structure
23', and a densified patterned breakable connection 23' (which
together make up the densified intermediate structure 40' shown in
FIG. 4G). In some examples, the liquid components (e.g., water,
solvents) may be substantially evaporated during the layer by layer
patterning process and/or while the intermediate structure 40' is
on the build area platform, and thus a post excavation baking
process may not be used. In these examples, additional heating may
be used in order to remove water and solvents, which may activate
the binder to generate a densified intermediate structure 40'. In
other examples, enough of the liquid components may be evaporated
in the layer by layer patterning process and/or while the
intermediate structure 40' is on the build area platform to render
the structure 40' handleable, and then a post excavation baking
process may be used to remove additional solvent and activate the
binder to generate the densified intermediate structure 40'.
[0115] It is to be understood that at least substantial evaporation
of the liquid components may be partial evaporation or complete
evaporation. At least substantial evaporation may be partial
evaporation when the presence of residual liquid components does
not deleteriously affect the desired structural integrity of the
intermediate structure 40 or the final 3D object that is being
formed. As an example, the densified intermediate part 25' formed
by the at least substantial evaporation of the liquid components of
the agent(s) 18 may contain a residual amount of the agent 18, but
the agent 18 is completely removed during subsequent heating.
[0116] As mentioned, at least substantial evaporation of the liquid
components (e.g., water and solvents) activates the binder in the
binding agent 18, and when used, in the combined agent 19. For
example, accelerated evaporation and binder activation may occur
when heating to a glass transition temperature or a minimum film
formation temperature of the binder. When activated, the binder
coalesces and forms a polymer glue that coats and binds together
the build material particles 14 patterned with the binding agent
18, and when used, the combined agent 19. At least substantial
evaporation of the liquid components also may result in the
densification of the patterned build material particles 14 through
capillary compaction. As such, at least substantial evaporation
forms the densified intermediate structure 40', shown in FIG.
4G.
[0117] In an example when an acrylic latex is used as the binder, a
first solvent of the binding agent 18 and/or combined agent 21 may
evaporate and allow a second solvent of the binding agent 18 and/or
combined agent 21 to come into contact with and soften the acrylic
latex particles. Then, as the second solvent evaporates, the
softened acrylic latex particles may merge or coalesce to form the
continuous network or film to bind the patterned volumes of build
material particles 14 into, for example, a densified intermediate
part 25', a densified build material support structure 23', and a
densified patterned breakable connection 32' (which together make
up the densified intermediate structure 40' shown in FIG. 4G).
[0118] The liquid components may be volatile enough to evaporate at
ambient temperature, or the densification/evaporation temperature
may be above ambient temperature. As used therein, "ambient
temperature" may refer to room temperature (e.g., ranging about
18.degree. C. to about 22.degree. C.), or to the temperature of the
environment in which the 3D printing method is performed (e.g., the
temperature of the build area platform 16 during the forming and
patterning of new layers). The temperature of the environment in
which the 3D printing method is performed (e.g., the temperature of
the build area platform 16 during the forming and patterning of new
layers) is about 5.degree. C. to about 50.degree. C. below the
boiling point of the agent 18 and 19 or 21. In an example, the
temperature of the build area platform 16 during the forming and
patterning of new layers ranges from about 50.degree. C. to about
95.degree. C. Other examples of the 3D printing environment
temperature may range from about 40.degree. C. to about 65.degree.
C. The densification/evaporation temperature may also be below a
temperature at which the binder would be damaged (i.e., be unable
to bind). For a majority of suitable binders, the upper limit of
the densification/evaporation temperature ranges from about
180.degree. C. to about 220.degree. C. Above this temperature
threshold, the binder would chemically degrade into volatile
species and leave the patterned components 23, 25, 32, and thus
would stop performing their function. For some agents 18, and when
used 19, the densification/evaporation temperature ranges from
about 50.degree. C. to about 220.degree. C. As still another
example, the densification/evaporation temperature may range from
about 70.degree. C. to about 90.degree. C.
[0119] During evaporation, the gas precursor (in the patterned
breakable connection 32) can collect across the surfaces of the
build material particles 14 in the patterned breakable connection
32.
[0120] In some examples of the method 100 or 200, the binding agent
18, and when used, the combined agent 19, may be allowed to
evaporate without heating. For example, more volatile solvents can
evaporate in seconds at ambient temperature. In these examples, the
build material cake is not exposed to heat or radiation to generate
heat, and the water and/or solvent(s) in the binding agent 18, and
when used, in the combined agent 19 evaporate(s) over time. In an
example, the water and/or solvent(s) in the binding agent 18, and
when used, the combined agent 19 may evaporate without heating
within a time period ranging from about 1 second to about 1
minute.
[0121] In other examples of the method 100 or 200, the intermediate
structure 40, 40A, 40B, 40C, 40D may be heated to an evaporation
temperature at a rate of about 1.degree. C./minute to about
10.degree. C./minute, although it is contemplated that a slower or
faster heating rate may be used. The heating rate may depend, in
part, on one or more of: the agents 18, 19, 21 used, the size
(i.e., thickness and/or area (across the x-y plane)) of the layers,
and/or the characteristics of the structure 40, 40A, 40B, 40C, 40D
(e.g., size, wall thickness, etc.). In an example, intermediate
structure 40, 40A, 40B, 40C, 40D is heated to the
densification/evaporation temperature at a rate of about
2.25.degree. C./minute.
[0122] At least substantially evaporating (with or without heating)
activates the binder, and the activated binder provides enough
adhesive strength to hold the densified intermediate structure 40'
together with enough mechanical stability to survive removal from
the build material cake. As such, the densified intermediate
structure 40' exhibits handleable mechanical durability, and is
capable of being separated from the non-patterned build material
28. FIG. 4G depicts the densified intermediate structure 40' after
the non-patterned build material 18 has been removed.
[0123] If after excavation from the build area platform 16, the
densified intermediate structure 40' still contains an undesirable
amount of less-volatile solvent(s), the post-excavation baking may
be performed at a temperature that will evaporate these
solvent(s).
[0124] While not shown, it is to be understood that the
intermediate structures 40A, 40B, 40C, 40D may be densified in a
similar manner.
[0125] The densified intermediate structure 40' may be extracted
from the build material cake or separated from the non-patterned
build material 28 by any suitable means. In an example, the
densified intermediate structure 40' may be extracted by lifting
the densified intermediate structure 40' from the non-patterned
build material 28. Any suitable extraction tool may be used. In
some examples, the densified intermediate structure 40' may be
cleaned to remove non-patterned build material 28 from its surface.
In an example, the densified intermediate structure 40' may be
cleaned with a brush and/or an air jet, may be exposed to
mechanical shaking, or may be exposed to other techniques that can
remove the non-patterned build material 28. As shown in FIG. 4G,
removal of the non-patterned build material 28 can expose outer
edges of the densified intermediate structure 40' and any spaces 50
between the densified build material support structure 23' and
portions of the densified patterned intermediate part 25' that had
been occupied by the non-patterned build material 28 during the
printing process.
[0126] When the densified intermediate structure 40' is extracted
from the build material cake and/or cleaned of the non-patterned
build material 28, the densified intermediate structure 40' may be
removed from the build area platform 16 and placed in a heating
mechanism 44 (as shown in FIG. 4H).
[0127] The heating mechanism 44 may be used to perform a heating
sequence, which involves exposing the intermediate structure 40'
(or the densified version of the intermediate structures 40A, 40B,
40C, or 40D) to a temperature that activates the gas precursor to
create gas pockets 36 in the patterned breakable connection 32. The
heating sequence may form a 3D particle article 10, as shown in
FIG. 4I. In some examples, heating involves exposure to a series of
temperatures that form a 3D object 46 from the patterned
intermediate part 25, 25', a 3D support structure 48 from the build
material support structure 23, 23' and the irreversibly breakable
connection 38 from the patterned breakable connection 32, 32', the
irreversibly breakable connection 38 including the gas pockets 36
and being positioned between the 3D object 46 and the 3D support
structure 48.
[0128] The series of temperatures may involve heating the
(densified) intermediate structure 40' (or the densified version of
the intermediate structures 40A, 40B, 40C, or 40D) to a de-binding
temperature, and then to an initial sintering temperature, followed
by a gas pocket formation temperature, followed by a final
sintering temperature. Briefly, the de-binding temperature removes
the binder from the densified intermediate structure 40' to produce
an at least substantially binder-free intermediate structure, and
the at least substantially binder-free intermediate structure may
be sintered at the various temperatures to form the final 3D object
46, the irreversibly breakable connection 38, and the 3D support
structure 48, and to create the gas pockets 36 within the
irreversibly breakable connection 38. Heating to de-bind and
heating to sinter and create the gas pockets 36 may take place at
several different temperatures, where the temperature for
de-binding is lower than the temperatures for sintering and gas
pocket creation.
[0129] Heating to de-bind is accomplished at a thermal
decomposition temperature that is sufficient to thermally decompose
the binder. As such, the temperature for de-binding depends upon
the binder in the agents 18, 19 used. In an example, the thermal
decomposition temperature ranges from about 250.degree. C. to about
600.degree. C. In another example, the thermal decomposition
temperature ranges from about 300.degree. C. to about 550.degree.
C. The binder may have a clean thermal decomposition mechanism
(e.g., leaves non-volatile residue in an amount <5 wt % of the
initial binder, and in some instances non-volatile residue in an
amount <1 wt % of the initial binder). The smaller residue
percentage (e.g., close to 0%) is more desirable. During the
de-binding stage, the binder decomposes first into a liquid phase
of lower viscosity. Evaporation of this liquid may initially
increase the open porosity in the substantially binder-free
intermediate structure.
[0130] While not being bound to any theory, it is believed that the
at least substantially binder-free intermediate structure may
maintain its shape due, for example, to one or more of: i) the low
amount of stress experienced by the at least substantially
binder-free i part due to it not being physically handled, and/or
ii) low level necking occurring between the build material
particles 14 at the thermal decomposition temperature of the
binder. The at least substantially binder-free intermediate
structure may maintain its shape although the binder is at least
substantially removed and the build material particles 14 are not
yet sintered.
[0131] The temperature may be raised to begin the initial stages of
sintering of the substantially binder-free intermediate structure,
which can result in the formation of weak bonds that are
strengthened during final sintering. The initial sintering
temperature is selected to further densify the substantially
binder-free intermediate structure and to decrease or eliminate the
open porosity throughout the substantially binder-free intermediate
structure. Open pores are pores that are interconnected to other
pores, and thus can undesirably allow gas(es) generated by the gas
precursor to be vented out of the patterned breakable connection 32
as it is sintered to form the irreversibly breakable connection 38.
The initial sintering temperature may be well above the de-binding
temperature, may be capable of softening the build material
particles 14, and may be below the activation temperature of the
gas precursor, so that the open pores are transformed into closed
pores (through the build material particles 14 beginning to sinter
together) and so that gas(es) are not yet generated by the gas
precursor. As such, the initial sintering temperature allows the
build material particles 14 in the patterned breakable connection
32 to soften and merge together enough to surround or enclose the
gas precursor without generating pocket forming gases.
[0132] The initial sintering temperature may thus be dependent upon
the build material used, as well as the gas precursor in the agent
19 or 21 used to pattern the patterned breakable connection 32.
Moreover, the initial sintering temperature may also be dependent
on the sintering rate of build material. For example, metal powders
with a smaller particle size can be sintered at a higher rate at
lower temperatures than the same metal powders with a larger
particle size. In this example, the previously described open to
closed porosity transition in the breakable connection 38 created
from smaller particle size metal powders may occur relatively
rapidly at lower temperatures, which enables the use of a lower
initial sintering temperature.
[0133] The heating temperature may then be raised to activate the
gas precursor in order to create/form the gas pockets 36 at the
patterned breakable connection 32 and in the irreversibly breakable
connection 38. Sintering has been initiated to form the 3D object
46, 3D support structure 48, and the irreversibly breakable
connection 38, which means that the build material particles 14 of
the patterned breakable connection 32 have begun to coalesce and
that open pores (i.e., pores that connect to other pores) have
begun to transform to closed pores (i.e., pores completely
surrounded by coalesced build material). As such, the gas precursor
is either residing inside the bulk build material particles 14 or
is trapped inside the closed pores, and thus is isolated from open
porosity. Thus, the gas precursor may be activated, as the
generated gas will be trapped within the irreversibly breakable
connection 38.
[0134] The gas pocket formation temperature may be dependent upon
the properties of build material. The gas pocket formation
temperature may be below the final sintering temperature and the
melting temperature of the build material. For example, when
aluminum/aluminum alloy build materials (melting temperature may be
as low as about 550.degree. C.) are used, it may be desirable for
the gas pocket activation or formation temperature to be within the
range of from about 500.degree. C. to about 590.degree. C., and the
gas precursor may be selected accordingly. As an example, titanium
hydride may be a suitable gas precursor to be used with aluminum
build material. For another example, when ferrous build material is
used, it may be desirable for the gas pocket activation or
formation temperature to be within the range from about 900.degree.
C. to about 1400.degree. C., and the gas precursor may be selected
accordingly.
[0135] The gas pocket formation temperature may also be dependent
on the sintering rate of the build material. As previously
described herein, metal powders with a smaller particle size can be
sintered at a higher rate and at lower temperatures than the same
metal powders with a larger particle size, and thus the open to
closed porosity transition may occur relatively rapidly at lower
temperatures. This would enable the use of gas precursors with
lower activation temperatures. As one specific example, a stainless
steel alloy build material having a particle size distribution of
D10=8.92 .mu.m, D50=14.8 .mu.m, and D90=23.25 .mu.m may have a gas
pocket formation temperature ranging from about 1100.degree. C. to
about 1390.degree. C. For smaller particle size distributions of
the stainless steel alloy build material, the gas pocket formation
temperature will shift to temperatures lower than 1100.degree.
C.
[0136] The following are some other examples of suitable gas
precursors and their corresponding activation or gas pocket
formation temperatures. Transition metal hydrides can generate
substantial amounts of hydrogen gas at a temperature ranging from
about 500.degree. C. to about 900.degree. C. Alkaline earth
carbonates can generate carbon dioxide at a temperature ranging
from about 840.degree. C. to about 1500.degree. C. Solid state
mixtures of oxidizable species and oxidizing agents can generate
carbon oxide gases, such as carbon dioxide or carbon monoxide, at
temperatures ranging from about 800.degree. C. to about
1400.degree. C.
[0137] Heating to create the gas pockets 36 may take place in an
environment/atmosphere that is compatible with the gas precursor
and build material used to form the patterned breakable connection
32. As one example, when the gas precursor in the agent 19 or 21
used to pattern the patterned breakable connection 32 is titanium
hydride or another transition metal hydride, a hydrogen gas
(H.sub.2) environment may be used during heating. As another
example, when the gas precursor in the agent 19 or 21 used to
pattern the patterned breakable connection 32 is an alkaline earth
carbonate, any gas environment (e.g., inert, reducing, vacuum,
etc.) may be used during heating. As still another example, when
the gas precursor in the agent 19 or 21 used to pattern the
patterned breakable connection 32 is the solid state mixture, a
non-reducing environment (e.g., argon, nitrogen, or vacuum) may be
used during heating.
[0138] FIG. 4H illustrates the intermediate structure 40' during
heating to the gas pocket formation temperature. As depicted, the
build material particles 14 have begun to coalesce in each of the
densified patterned intermediate part 25', the densified build
material support structure 23', and the densified patterned
breakable connection 32'. As such, the formation of the 3D
object/part 46, the 3D support structure 48, and the irreversibly
breakable connection 38 has been initiated. The initial coalescence
of the build material particles 14 has formed the closed pores 52
in each of the densified patterned intermediate part 25', the
densified build material support structure 23', and the densified
patterned breakable connection 32'. Within the densified patterned
breakable connection 32', the closed pores 52 entrap the gas
precursor, which has generated the gas pockets 36 as a result of
being exposed to the gas pocket formation temperature.
[0139] The temperature may be raised again to finish the stages of
sintering. During final sintering, the build material particles 14
continue to coalesce to form the 3D object 46, the 3D support
structure 48, and the irreversibly breakable connection 38, and so
that a desired density of at least the 3D object 46 is achieved.
The final sintering temperature is a temperature that is sufficient
to sinter the remaining build material particles 14. The sintering
temperature is highly depending upon the composition of the build
material particles. During final sintering, the at least
substantially binder-free intermediate structure may be heated to a
temperature ranging from about 80% to about 99.9% of the melting
point(s) of the build material particles 14. In another example,
the at least substantially binder-free intermediate structure may
be heated to a temperature ranging from about 90% to about 95% of
the melting point(s) of the build material particles 14. In still
another example, the at least substantially binder-free
intermediate structure may be heated to a temperature ranging from
about 60% to about 90% of the melting point(s) of the build
material particles 14. In still another example, the final
sintering temperature may range from about 10.degree. C. below the
melting temperature of the build material particles 14 to about
50.degree. C. below the melting temperature of the build material
particles 14. In still another example, the final sintering
temperature may range from about 100.degree. C. below the melting
temperature of the build material particles 14 to about 200.degree.
C. below the melting temperature of the build material particles
14. The final sintering temperature may also depend upon the
particle size and time for sintering (i.e., high temperature
exposure time). As an example, the sintering temperature may range
from about 500.degree. C. to about 1800.degree. C. In another
example, the sintering temperature is at least 900.degree. C. An
example of a final sintering temperature for bronze is about
850.degree. C., and an example of a final sintering temperature for
stainless steel is about 1400.degree. C., and an example of a final
sintering temperature for aluminum or aluminum alloys may range
from about 550.degree. C. to about 620.degree. C. While these
temperatures are provided as final sintering temperature examples,
it is to be understood that the final sintering temperature depends
upon the build material particles that are utilized, and may be
higher or lower than the provided examples. Heating at a suitable
final sintering temperature sinters and fuses the build material
particles 14 to form a completed 3D object 46, a completed 3D
support structure 48, and a completed irreversibly breakable
connection, each of which may be even further densified relative to
the corresponding components of the at least substantially
binder-free intermediate structure. For example, as a result of
final sintering, the density may go from 50% density to well over
90%, and in some cases very close to 100% of the theoretical
density.
[0140] The length of time at which the heat (for each of
de-binding, gas pocket generation, and sintering) is applied and
the rate at which the structure is heated may be dependent, for
example, on one or more of: characteristics of the heating
mechanism 44, characteristics of the binder, characteristics of the
build material particles (e.g., metal type, particle size, etc.),
characteristics of the gas precursor, and/or the characteristics of
the 3D object/part 46 (e.g., wall thickness).
[0141] The densified intermediate structure 40' (or the densified
version of the intermediate structures 40A, 40B, 40C, or 40D) may
be heated at the de-binding temperature for a time period ranging
from about 10 minutes to about 72 hours. When the structure 40'
contains open porosity to vent out binder pyrolysis, and/or the
amount of the binder in the densified intermediate structure 40' is
low (e.g., from about 0.01 wt % to about 4.0 wt % based on the
total weight of the build material particles 14) and/or the wall
thickness of the structure 40' is relatively thin, the time period
for de-binding may be 3 hours (180 minutes) or less. Longer times
may be used if the structure 40' has less open porosity, if the
structure 40' has thicker walls, and/or if the structure 40' has a
higher concentration of binder. In an example, the de-binding time
period is about 60 minutes. In another example, the de-binding time
period is about 180 minutes. The densified green part may be heated
to the de-binding temperature at a rate ranging from about
0.5.degree. C./minute to about 20.degree. C./minute. The heating
rate may depend, in part, on one or more of: the amount of the
binder in the densified intermediate structure 40', the porosity of
the densified intermediate structure 40', and/or the
characteristics of the densified intermediate structure 40'.
[0142] The at least substantially binder-free intermediate
structure may be heated at each of the initial sintering
temperature, the gas formation temperature, and the final sintering
temperature for respective time periods ranging from about 20
minutes to about 15 hours. In an example, each time period is 60
minutes. In another example, each time period is 90 minutes. In
still another example, each of the initial sintering time period,
the gas formation time period, and the final sintering time period
is less than or equal to 3 hours. The at least substantially
binder-free intermediate structure may be heated to each of the
initial sintering temperature, the gas formation temperature, and
the final sintering temperature at a rate ranging from about
1.degree. C./minute to about 20.degree. C./minute. In an example,
the at least substantially binder-free intermediate structure is
heated to each of the initial sintering temperature, the gas
formation temperature, and the final sintering temperature at a
rate ranging from about 10.degree. C./minute to about 20.degree.
C./minute. In a specific example, the at least substantially
binder-free intermediate structure is heated to the initial
sintering temperature at a rate of about 10.degree. C./minute and
is held at the initial sintering temperature for about 60 minutes;
and then is heated to the gas formation temperature at a rate of
about 10.degree. C./minute, is held at the gas formation
temperature for about 60 minutes; and then is heated to the final
sintering temperature at a rate of about 10.degree. C./minute, is
held at the final sintering temperature for about 60 minutes.
[0143] An example of the resulting 3D printed article 10 is shown
in FIG. 4I. After heating, the 3D printed article 10 may be cooled.
It is to be understood that the gas pockets 36 remain in the
irreversibly breakable connection 38 when cooled.
[0144] The 3D printed article 10 includes a first object (e.g., the
3D object 46), a second object (e.g., the 3D support structure 48),
and the irreversibly breakable connection 38 between the first and
second objects 46, 48, wherein the irreversibly breakable
connection 38 includes the gas pockets 36. In an example, the first
object is a metal 3D part, the second object is a metal 3D support
structure, and the irreversibly breakable connection 38 is a metal
object including the gas pockets 36.
[0145] The gas pockets 36 are localized to the irreversibly
breakable connection 38, and thus add fragility to the irreversibly
breakable connection 38. As such, the irreversibly breakable
connection 38 provides a weak junction or a fault line domain
between the first object (e.g., the 3D object 46) and the second
object (e.g., the 3D support structure 48). As such, the second
object (e.g., the 3D support structure 48) can be easily removed
from the first object (e.g., the 3D object 46) by breaking the
irreversibly breaking connection 38. Breaking may be accomplished
with human hands, or with simple tools, such as pliers and/or a
vise. Cutting tools may be used, but may not have to be used in
order to break the second object (e.g., the 3D support structure
48) from the first object (e.g., the 3D object 46).
[0146] An example of the 3D object 46 after the irreversibly
breakable connection 38 has been broken is depicted in FIG. 4J. The
break at the irreversibly breakable connection 38 enables the 3D
support structure 48 to be separated from the 3D object and removed
(and thus it is not shown in FIG. 4J). At most, some remnants 68 of
metal pieces from the irreversibly breakable connection 38 may
remain attached to the 3D object 46. It is to be understood that
once the irreversibly breakable connection 38 is broken, the gas
within the gas pockets 36 may be released.
[0147] Printing System
[0148] Referring now to FIG. 5, an example of the 3D printing
system 60 that may be used to perform examples of the method 100
disclosed herein is depicted. It is to be understood that the 3D
printing system 10 may include additional components (some of which
are described herein) and that some of the components described
herein may be removed and/or modified. Furthermore, components of
the 3D printing system 60 depicted in FIG. 5 may not be drawn to
scale and thus, the 3D printing system 60 may have a different size
and/or configuration other than as shown therein.
[0149] In an example, the three-dimensional (3D) printing system
60, comprises: a supply 11 of build material particles 14; a build
material distributor 13; a supply of a binding agent 18 and a
supply of a separate gas generating liquid functional agent 21, or
a supply of a combined agent 19; applicator(s) 17 for selectively
dispensing the binding agent 18 and the separate gas generating
liquid functional agent 21 or the combined agent 19; a controller
62; and a non-transitory computer readable medium having stored
thereon computer executable instructions to cause the controller 62
to cause the printing system to perform some or all of the method
disclosed herein.
[0150] As mentioned above, the build area platform 16 receives the
build material particles 14 from the build material supply 11. The
build area platform 16 may be integrated with the printing system
60 or may be a component that is separately insertable into the
printing system 60. For example, the build area platform 16 may be
a module that is available separately from the printing system 60.
The build area platform 16 that is shown is one example, and could
be replaced with another support member, such as a platen, a
fabrication/print bed, a glass plate, or another build surface.
[0151] While not shown, it is to be understood that the build area
platform 16 may also include built-in heater(s) for achieving and
maintaining the temperature of the environment in which the 3D
printing method is performed.
[0152] Also as mentioned above, the build material supply 11 may be
a container, bed, or other surface that is to position the build
material particles 14 between the build material distributor 13 and
the build area platform 16. In some examples, the build material
supply 11 may include a surface upon which the build material
particles 14 may be supplied, for instance, from a build material
source (not shown) located above the build material supply 11.
Examples of the build material source may include a hopper, an
auger conveyer, or the like. Additionally, or alternatively, the
build material supply 11 may include a mechanism (e.g., a delivery
piston) to provide, e.g., move, the build material particles 14
from a storage location to a position to be spread onto the build
area platform 16 or onto a previously patterned layer.
[0153] As shown in FIG. 5, the printing system 60 also the build
material distributor 18 and the applicator(s) 17, both of which
have been described in reference to the method 200.
[0154] Each of the previously described physical elements may be
operatively connected to the controller 62 of the printing system
60. The controller 62 may process print data that is based on a 3D
object model of the 3D object/part 46 and of the 3D support
structure 48 to be generated. In response to data processing, the
controller 62 may control the operations of the build area platform
16, the build material supply 11, the build material distributor
13, and the applicator(s) 17. As an example, the controller 62 may
control actuators (not shown) to control various operations of the
3D printing system 62 components. The controller 60 may be a
computing device, a semiconductor-based microprocessor, a central
processing unit (CPU), an application specific integrated circuit
(ASIC), and/or another hardware device. Although not shown, the
controller 62 may be connected to the 3D printing system 60
components via communication lines.
[0155] The controller 62 manipulates and transforms data, which may
be represented as physical (electronic) quantities within the
printer's registers and memories, in order to control the physical
elements to create the printed article 10. As such, the controller
62 is depicted as being in communication with a data store 64. The
data store 64 may include data pertaining to a 3D object 46, a 3D
support structure 48, and an irreversibly breakable connection 38
to be printed by the 3D printing system 60. The data for the
selective delivery of the build material 16, the binding agent 18,
the gas generating liquid functional agent 19 or 21, etc. may be
derived from a model of the components 46, 48 and 38 to be formed.
For instance, the data may include the locations on each build
material layer 12, etc. that the applicator 17 is to deposit the
binding agent 18. In one example, the controller 62 may use the
data to control the applicator 17 to selectively apply the binding
agent 18. The data store 64 may also include machine readable
instructions (stored on a non-transitory computer readable medium)
that are to cause the controller 62 to control the amount of build
material particles 14 that is supplied by the build material supply
11, the movement of the build area platform 16, the movement of the
build material distributor 13, the movement of the applicator 17,
etc.
[0156] As shown in FIG. 5, the printing system 60 also includes the
heating mechanism 44. Examples of the heating mechanism 44 include
a conventional furnace or oven, a microwave, or devices capable of
hybrid heating (i.e., conventional heating and microwave heating).
As shown in FIG. 5, the heating mechanism 44 may be a module that
is available separately from the printing system 60. In other
examples, the heating mechanism 44 may be integrated with the
printing system 60.
[0157] The heating mechanism 44 and/or the heater(s) in the build
area platform 16 may be operatively connected to a driver, an
input/output temperature controller, and temperature sensors, which
are collectively shown as heating system components 66. The heating
system components 66 may operate together to control the heating
mechanism 44 and/or the heater(s) in the build area platform 16.
The temperature recipe (e.g., heating exposure rates and times) may
be submitted to the input/output temperature controller. During
heating, the temperature sensors may sense the temperature of the
build material particles 14 on the platform 16 or in the
intermediate structure 40, 40', and the temperature measurements
may be transmitted to the input/output temperature controller. For
example, a thermometer associated with the heated area can provide
temperature feedback. The input/output temperature controller may
adjust the heating mechanism 44 and/or the heater(s) in the build
area platform 16 power set points based on any difference between
the recipe and the real-time measurements. These power set points
are sent to the drivers, which transmit appropriate voltages to the
heating mechanism 44 and/or the heater(s) in the build area
platform 16. This is one example of the heating system components
66, and it is to be understood that other heat control systems may
be used. For example, the controller 62 may be configured to
control the heating mechanism 44 and/or the heater(s) in the build
area platform 16.
[0158] It is to be understood that the ranges provided herein
include the stated range and any value or sub-range within the
stated range. For example, from about 500.degree. C. to about
3500.degree. C. should be interpreted to include not only the
explicitly recited limits of from about 500.degree. C. to about
3500.degree. C., but also to include individual values, such as
about 690.degree. C., 1000.5.degree. C., 2055.degree. C.,
2750.degree. C., etc., and sub-ranges, such as from about
900.degree. C. to about 3250.degree. C., from about 525.degree. C.
to about 2500.degree. C., from about 1020.degree. C. to about
2020.degree. C., etc. Furthermore, when "about" is utilized to
describe a value, this is meant to encompass minor variations (up
to +/-10%) from the stated value.
[0159] Reference throughout the specification to "one example",
"another example", "an example", and so forth, means that a
particular element (e.g., feature, structure, and/or
characteristic) described in connection with the example is
included in at least one example described herein, and may or may
not be present in other examples. In addition, it is to be
understood that the described elements for any example may be
combined in any suitable manner in the various examples unless the
context clearly dictates otherwise.
[0160] While several examples have been described in detail, it is
to be understood that the disclosed examples may be modified.
Therefore, the foregoing description is to be considered
non-limiting.
* * * * *