U.S. patent application number 15/968123 was filed with the patent office on 2018-08-30 for ceramic support structure.
The applicant listed for this patent is Stratasys, Inc.. Invention is credited to Benjamin A. Demuth, Adam R. Pawloski.
Application Number | 20180243941 15/968123 |
Document ID | / |
Family ID | 51581318 |
Filed Date | 2018-08-30 |
United States Patent
Application |
20180243941 |
Kind Code |
A1 |
Demuth; Benjamin A. ; et
al. |
August 30, 2018 |
CERAMIC SUPPORT STRUCTURE
Abstract
A pre-ceramic support structure for additive manufacturing, that
upon thermal processing, is soluble in various solvents.
Inventors: |
Demuth; Benjamin A.; (River
Falls, WI) ; Pawloski; Adam R.; (Lake Elmo,
MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Stratasys, Inc. |
Eden Prairie |
MN |
US |
|
|
Family ID: |
51581318 |
Appl. No.: |
15/968123 |
Filed: |
May 1, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14776007 |
Sep 14, 2015 |
10022889 |
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PCT/US2014/027775 |
Mar 14, 2014 |
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15968123 |
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61781997 |
Mar 14, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B28B 1/001 20130101;
C04B 35/62227 20130101; C08K 2003/265 20130101; C04B 2235/365
20130101; C04B 2235/602 20130101; C04B 2111/40 20130101; C04B
2235/6021 20130101; B29C 64/106 20170801; C04B 35/62695 20130101;
C04B 2235/94 20130101; C04B 2235/445 20130101; C04B 2235/3244
20130101; C04B 2235/6026 20130101; C08K 3/26 20130101; B29K 2309/02
20130101; B29C 64/118 20170801; D01F 1/02 20130101; B33Y 10/00
20141201; C04B 35/63408 20130101; C09D 5/00 20130101; C04B
2235/3201 20130101; C04B 2235/604 20130101; B28B 11/243 20130101;
C04B 35/634 20130101; C04B 35/524 20130101; C04B 2235/3203
20130101; C09D 7/61 20180101; C04B 2235/449 20130101; C04B 2235/442
20130101; C09D 123/0815 20130101; C04B 2235/3418 20130101; B33Y
70/00 20141201; C04B 2235/3208 20130101; C04B 2235/3222 20130101;
C04B 38/04 20130101; C04B 2235/3232 20130101; C04B 38/04 20130101;
C04B 35/524 20130101 |
International
Class: |
B28B 1/00 20060101
B28B001/00; C04B 35/634 20060101 C04B035/634; C04B 35/622 20060101
C04B035/622; B29C 64/106 20060101 B29C064/106; C04B 35/626 20060101
C04B035/626; C04B 35/524 20060101 C04B035/524 |
Claims
1-15. (canceled)
16. A feedstock material in filament form for use as a support
material in an additive manufacturing system, the feedstock
material comprising: a pre-ceramic material in powder form, the
preceramic material comprises calcium carbonate, sodium carbonate,
sodium aluminate or combinations thereof, wherein the pre-ceramic
material is at least about 50 weight % of the feedstock material;
and a thermoplastic binder up to about 25 weight % of the feedstock
material, and having the pre-ceramic material dispersed therein,
wherein the thermoplastic binder comprising one or more of
polyolefins, polylactic acid polymers, and acrylonitrile butadiene
styrene polymers or combinations thereof; wherein the filament is
configured to be melted and extruded to form a support structure in
a layer by layer manner for a sinterable article formed in a layer
by layer manner; and wherein the support structure does not soften
below 700 degrees C.; and does not melt below 1200 degrees C.; and
wherein the support structure is removable in a solvent after
sintering.
17. The feedstock material of claim 16, wherein the pre-ceramic
material is at least about 75% of the feedstock material.
18. The feedstock material of claim 16, and further comprising one
or more of fluxing materials, a polymer processing additive or
combinations thereof.
19. The feedstock material of claim 18, wherein the fluxing
material comprises glass frits having boron trioxide, silicon
oxide, zirconium dioxide, lithium oxide, fluorine, titanium
dioxide, and combinations thereof.
20. A method of printing a three-dimensional article with an
extrusion based additive manufacturing system, the method
comprising: providing a filled thermoplastic build material in the
form of a filament feedstock; providing a support material in the
form of a filament feedstock; printing the article in a layer by
layer manner by extruding the build material; printing a
corresponding support structure in a layer by layer manner by
extruding the support material, wherein the support material
comprises: a pre-ceramic material in powder form, the preceramic
material comprises calcium carbonate, sodium carbonate, sodium
aluminate or combinations thereof, wherein the pre-ceramic material
is at least about 50 weight % of the support material feedstock;
and a thermoplastic binder up to about 25 weight % of the support
material filament feedstock, and having the pre-ceramic material
dispersed therein, wherein the thermoplastic binder is a comprising
one or more of polyolefins, polylactic acid polymers, and
acrylonitrile butadiene styrene polymers or combinations thereof;
and wherein the support structure does not soften below 700 degrees
C.; and does not melt below 1200 degrees C.; and wherein the
support structure is removable in a solvent after sintering.
21. The method of claim 21, and further comprising heating the
three-dimensional article and the corresponding support structure
to a first temperature to remove the thermoplastic binder from both
the build material and support material.
22. The method of claim 21, and further comprising heating the
three-dimensional article and the corresponding support structure
to a second temperature that is higher than the first temperature
to sinter the article and the corresponding support structure,
wherein the support structure maintains shape and provides
structural support of the 3D article during the sintering
process.
23. The method of claim 22, further comprising subjecting the
ceramic article and corresponding support structure to a solvent to
remove the support structure from the article.
24. The method of claim 23, wherein the solvent comprises water,
carbonated solutions, acidic solutions and combinations
thereof.
25. The method of claim 20, wherein the feedstock material further
comprises one or more of fluxing materials, a polymer processing
additive or combinations thereof.
26. The method of claim 20, wherein the pre-ceramic material is at
least about 75% of the feedstock material.
27. A method of printing a three-dimensional article with an
extrusion based additive manufacturing system, the method
comprising: providing a filled thermoplastic build material in the
form of a filament feedstock; providing a support material in the
form of a filament feedstock; printing the article in a layer by
layer manner by extruding the build material; printing a
corresponding support structure in a layer by layer manner by
extruding the support material, wherein the support material
comprises: a pre-ceramic material in powder form, the preceramic
material comprises calcium carbonate, sodium carbonate, sodium
aluminate or combinations thereof, wherein the pre-ceramic material
is at least about 50 weight % of the support material feedstock; a
thermoplastic binder up to about 25 weight % of the support
material filament feedstock, and having the pre-ceramic material
dispersed therein, wherein the thermoplastic binder is a comprising
one or more of polyolefins, polylactic acid polymers, and
acrylonitrile butadiene styrene polymers or combinations thereof,
and wherein the support structure does not soften below 700 degrees
C.; and does not melt below 1200 degrees C.; and wherein the
support structure is removable in a solvent after sintering;
heating the three-dimensional article and the corresponding support
structure to a first temperature to remove the thermoplastic binder
from both the build material and support material by thermally
degrading the thermoplastic binder, heating the three-dimensional
article and the corresponding support structure to a second
temperature that is higher than the first temperature to sinter the
article and the corresponding support structure, wherein the
support structure maintains shape and provides structural support
of the 3D article during the sintering process, and subjecting the
ceramic article and corresponding support structure to a solvent to
remove the support structure from the article.
28. The method of claim 27, wherein the pre-ceramic material is at
least about 75% of the feedstock material.
29. The method of claim 27, and wherein the support material
further comprising one or more of fluxing materials, a polymer
processing additive or combinations thereof.
30. The method of claim 29, wherein the fluxing material comprises
glass frits having boron trioxide, silicon oxide, zirconium
dioxide, lithium oxide, fluorine, titanium dioxide, and
combinations thereof.
Description
TECHNICAL FIELD
[0001] The disclosure is related to the use of a melt processable
pre-ceramic materials for applications as a support structure in
additive manufacturing.
BACKGROUND
[0002] Additive manufacturing technology, also recognized as three
dimensional printing technology, builds three-dimensional objects
through layer-by-layer deposition of thermoplastic materials. A
plastic filament is utilized to deliver materials to an extrusion
nozzle. The nozzle is heated to melt the material and can be moved
in both horizontal and vertical directions by computer control. The
three dimensional object is produced by extruding small beads of
thermoplastic material to form layers. The layers of thermoplastic
material harden after extrusion. Support materials are often
employed to assist in building certain three dimensional objects.
The support structures are thermoplastic materials that can be
removed from contact with other extruded materials by physical or
chemical means. Certain support materials are selectively soluble
in certain liquids. The composition of a thermoplastic support
materials and the liquid can be selected so that the liquid
dissolves the support material, but not the intended material of
construction for the desired object.
SUMMARY
[0003] One embodiment involving additive manufacturing of ceramics
is a process where thermoplastic filaments of pre-ceramic powders
are extruded to form a three dimensional article. In certain
applications of additive manufacturing, a sacrificial "support"
layer is utilized to assist in forming "build" layers that create
the intended three-dimensional product. The support layer will be
subsequently removed to create a final object. During the additive
manufacturing of ceramics in accordance with this disclosure,
thermoplastic polymers carry the pre-ceramic powders to form
three-dimensional green ceramic parts that contain the
thermoplastic binder. For purposes of this disclosure, the
thermoplastic polymers with the pre-ceramic can be intended as
either the support layer as well as the build layer. The parts are
then subjected to a binder removal and sintering cycle during
firing of the object, resulting in certain embodiments in
ceramification. Due to the elevated temperatures for sintering,
conventional thermoplastic support layers are not suitable simply
because the temperatures are far above the degradation temperatures
of the polymer. The degradation of the support structure in turn
may adversely affect the build layer and the intended article. This
has limited the types of three-dimensional ceramic objects produced
utilizing conventional additive manufacturing practices.
[0004] This disclosure is directed to the use of a pre-sintered
support layer or structure for additive manufacturing, that upon
firing or sintering, is soluble in various solvents. The
compositions are additive manufacturing feedstocks, having a
polymeric matrix and a pre-ceramic compound, wherein the
post-sintered support layer is soluble or removable in a solvent.
In general, the feedstocks are produced using melt processing
techniques to form filaments that are suitable in applications with
additive manufacturing processes and equipment.
[0005] For purposes of this disclosure, ceramic means a material
that has been subject to a thermal process, or firing, to form an
anhydrous or substantially anhydrous material. A green ceramic is a
material that has not been subjected to a thermal process. Green
ceramifiable articles can be produced with additive manufacturing
wherein a pre-sintered build layer is supported by a pre-sintered
support layer. Upon firing of the green article, the polymeric
binders from both the build and support layers are removed by
thermal degradation, and in doing so, the build layer is
transformed into a ceramic composition by additional thermal
processing or sintering. The support layer maintains shape and
structural support of the build layer during this process. With the
removal of polymeric binder, the remaining material of the support
layer is soluble or removable in a solvent. The entire object of
the now ceramic support structure can be subject to a solvent where
it is removed, thereby leaving the finished ceramic article formed
by the build layer.
DETAILED DESCRIPTION
[0006] A pre-sintered support structure for additive manufacturing
can be used to assist in the formation of three-dimensional ceramic
articles. The feedstocks for the pre-sintered support structure are
produced using melt processing techniques to form, in certain
embodiments, filaments that are suitable in applications with
additive manufacturing processes and equipment. The support
structure filaments are employed with build structure filaments to
create three-dimensional objects by additive manufacturing.
[0007] In certain embodiments, green ceramifiable articles may be
produced with additive manufacturing techniques. The green
ceramifiable article is supported by a support composition of a
polymeric matrix and a pre-ceramic compound. Upon firing of the
green article at elevated temperatures, the entire object including
the post sintered support structure can be subject to a solvent
bath where the ceramic support structure is removed, thereby
leaving the finished ceramic article.
[0008] The support layer feedstock intended as the support
structure is primarily a pre-ceramic powder or powder blend in a
polymeric matrix. The polymer serves as a binder for the
pre-ceramic powder or powder blend. The polymeric matrix imparts
the necessary strength for the creation of a molded or printed
support structure. Additionally, it imparts the desired physical
properties required to make the feedstock for the additive
manufacturing process. The polymeric matrix may be any
thermoplastic polymer capable of melt processing and functioning as
a feedstock for additive manufacturing. They include both
hydrocarbon and non-hydrocarbon polymers. In certain embodiments,
the polymeric matrix may be a polyethylene, an ethylene-octene
copolymer. or combinations thereof. Other non-limiting examples of
polymeric matrices include other polyolefins, polylactic acid
polymers, and acrylonitrile butadiene styrene polymers or
combinations thereof. The polymeric matrix may be included in the
pre-ceramic feedstock in amounts ranging from about 0.1% to about
25% by weight. In certain embodiments, the polymeric matrix may be
included at about 0.5% to about 5% by weight. In some embodiments,
the feedstock is generally in the form of an extruded filament.
[0009] The pre-ceramic materials suitable for additive
manufacturing are powders or micron sized compounds that are
soluble in either a pre-ceramic or sintered state in various
solvents. In some embodiments, the pre-ceramic is an acid labile
mineral capable of forming a semi-solid under high heat. The
intended application suggests that in certain embodiments the
support structure, upon formation, must not soften below
700.degree. C. Additionally, the support structure must not melt
below 1200.degree. C. Non-limiting examples of pre-ceramic
materials include calcium carbonate, sodium carbonate, sodium
aluminate or calcium carbide. Those of ordinary skill in the art
with knowledge of this disclosure are capable of selecting a
specific material to match the intended additive manufacturing
article. For example, in applications where sintering does not
exceed 850.degree. C. sodium carbonate may also be used. In
applications exceeding the 950.degree. C. limits of calcium
carbonate, sodium aluminate may be used up to 1500.degree. C. In
applications requiring extreme heat, calcium carbide may be
employed, up to 2000.degree. C. The amount of pre-ceramic material
in the feedstock may be at least 50%. In certain embodiments the
pre-ceramic material is greater than 75% and even greater than
95%.
[0010] In some embodiments, a flux is used to reduce the overall
melting point of the pre-ceramic material and thereby enhance the
efficiency of the sintering process. The flux may be any glass or
ceramic material, which flows below the softening point of the
pre-ceramic material. Non-limiting examples of flux materials
include glass frits comprised of boron trioxide. silicon oxide,
zirconium dioxide, lithium oxide, fluorine, titanium dioxide, and
combinations thereof. The flux may be included in the feedstock
composition in amounts up to 20%. In one embodiment, a suitable
flux is Ferro Frits 90 740 F from the Ferro Corporation, Frankfurt,
Del. In another embodiment, the flux may include silicates with
melting points from 600.degree. C. to 1000.degree. C. The flux may
be added to the feedstock during melt processing.
[0011] In alternative embodiment, various processing additives may
be utilized in the formation of the feedstock. Non-limiting
examples of processing aids include waxes, moisture scavengers,
lubricants and debinders. The processing additives are included in
the melt processable composition in an amount of about 0.5 wt % to
about 5 wt %.
[0012] The components comprising the feedstock are blended and
subjected to melt processing. The feedstock can be pelletized and
then subsequently formed into a filament suitable for additive
manufacturing. In some embodiments, the filament has a modulus of
approximately 300 MPato 1600 MPa.
[0013] The melt processing of the feedstock is generally performed
in a twin-screw extruder. In certain embodiments, the processing is
performed in co-rotating, segmented twin-screw extruder. In such
instances, the length:diameter ratio of the twin screw extruder is
at least 32:1. In another embodiment, the length:diameter ratio of
the twin screw extruder is at least 40:1. Typical temperature
profiles may range from 120-220.degree. C. with typical screw
speeds potentially in the range of about 200-300 RPM. Die pressures
can be minimized to ensure incorporation of all pre-ceramic
materials into the thermoplastic binder. Those who are skilled in
the art will recognize preferred screw designs and temperature
profiles to achieve optimal blending of the melt process sable
compositions of this invention.
[0014] The feedstock containing pre-ceramic materials is used in
additive manufacturing as a support structure for ceramic articles.
The support structure or layers are utilized with build layers to
form a three-dimensional article or object. The materials are
capable of withstanding the elevated temperatures necessary to
place a green ceramic article into its desired ceramic form. Those
of ordinary skill in the art are capable of selecting an
appropriate feedstock to match a particular ceramic. Additionally,
additive manufacturing equipment and techniques may be selected
depending upon the desired finished article. One example of an
additive manufacturing device is a Makerbot Replicator 2.times.
additive manufacturing printer, available from Stratasys Ltd,
Minneapolis, Minn.
[0015] An article created with a pre-sintered build structure,
along with the pre-sintered support structure or layer, is fired at
elevated temperatures. During the firing of the green ceramic
article the support structure or layers withstand the elevated
temperatures and do not deform and thereby do not adversely affect
the intended ceramic article. The support structure or layers may
then be removed in suitable solvents. The removal of the support
structure or layers results in the finished ceramic article.
Suitable solvents will depend upon the pre-ceramic material used in
the feedstock. Non-limiting examples include: water, carbonated
solutions, and acidic solutions. Those of ordinary skill in the art
are capable of selecting a specific solvent based on the
pre-ceramic material selected in the feedstock.
EXAMPLES
TABLE-US-00001 [0016] Material Supplier PE1 Engage 8003,
ethylene-octene copolymer. commercially available from Dow Chemical
Corporation. Midland. MI. Calcium GLC-1012d. 12 micron CaCO.sub.3.
commercially Carbonate available from Great Lakes Calcium, Green
Bay. WI.
Compounding Procedure for Example 1
[0017] For Example 1. ethylene-octene copolymer resin PEL and
Calcium Carbonate powder were dry blended and then fed using a
gravimetric feeder into a 27 mm co-rotating twin screw extruder
(32:1. L:D) fitted with a strand die (commercially available from
Leistritz Corporation. Allendale. N.J.). Samples were processed
with a screw rotational speed of 250 rpm using the following
temperature profile: Zone 1-10=180.degree. C. Die=160.degree. C.
The resulting strands of extrudate were subsequently continuously
processed onto a belt, cooled to room temperature by fans, and
pelletized into 0.64 cm pellets. The resulting pellets were used to
press 6 mm square plaques. 6 mm in depth.
Pressing Procedure for CE1 and Example 2
[0018] Plaques in Example 2 were made using a heated platen
hydraulic press (commercially available from Dake Corporation.
Grand Haven. Mich.). Approximately 1 lOg of pellets from example 1
were spread in an aluminum frame equating to the dimensions
previously listed, and covered with aluminum foil. The top and
bottom platens, heated to 175.degree. C. were made to contact the
pellets of example 1 in the aluminum frame for 3 min. under minimal
pressure. After 3 min, 15 tons of pressure was applied to the
material for 5 min. after which time, the material was removed and
allowed to cool to room temperature at an unspecified rate. This
procedure was repeated using, previously demonstrated, ceramifiable
polymer to produce 10.times.10.times.0.6 cm plaques of CEL
[0019] Three aluminum frames were stacked vertically. A plaque of
CE1 was placed in the bottom. The plaque of example 1 was cut into
a cross of equal legs, 5 cm wide with an outer diameter of 4
inches, fitting into the aluminum frame previously used. Pellets of
a ceramifiable material used to make CE1 were placed in the
cavities of the second frame. A third plaque of CE1 was placed on
top and the sample pressing procedure was followed to make example
2. Example 2 having final dimensions of 10.times.10.times.0.6 cm,
made of CE1 and having a cross of example 1 centered
internally.
Ceramification and Dissolution of Example 2 into Example 3
[0020] Example 2 was heated in a muffle furnace (commercially
available from ThermoFisher Scientific Corporation, Weldham, Mass.)
to 950.degree. C. for 20 min at an unspecified rate. This material
was removed from the furnace and allowed to cool to room
temperature at an unspecified rate. This conversion yielded a
wholly ceramified. intact article of similar initial dimensions of
example 2. Upon immersion in a water bath, the CaCCb material from
example 1 was entirely dissolved leaving example 3 of dimensions
equal to the CE1 material only, in example 2.
Example 4
[0021] A filament containing a pre-ceramic material suitable as a
support layer, is extruded in a manner similar to that of Example
1. and wound onto a spool. A second filament containing a
pre-ceramic material suitable as a build layer is also produced in
a manner similar to Example 1 and wound onto a spool. The spools
are loaded into a MakerBot Replicator 2.times. additive
manufacturing printer, available from Stratasys Ltd. Minneapolis.
Minn. The filament from each spool is fed into the MakerBot
2.times. extruder nozzles in accordance with the printers loading
procedures.
[0022] A CAD file of a three-dimensional article requiring a
support layer and a build layer with 90.degree. overhangs of the
build layer is selected and loaded into the MakerBot 2.lamda..
[0023] The loaded filaments are printed at temperature of about 160
to 200.degree. C. and at printing speeds ranging between 20 and 100
mm/sec with acceleration enabled. The materials are printed onto a
standard Kapton tape heated to about 100.degree. C. Filament are
printed with an infill between 5 and 95%. Layer heights are between
0.10 and 0.35 mm.
[0024] The printed article having a build and support layer
constructed from pre-ceramic filaments is subjected to a thermal
treatment. The printed article is placed in a muffle furnace and
heated to about 450.degree. C., under an inert, oxidizing, or
reducing gas, to thermally remove any thermoplastic material and
water. The printed article is then further heated to in excess of
750.degree. C. under an inert, oxidizing, or reducing gas, to
enable sintering and thereby create a ceramic, or substantially
ceramic, article.
[0025] The article is cooled at an appropriate rate so as not to
produce thermal cracking or warping. The article does not exhibit
any warping of either the support layer or the build layer. The
structure of the build layer is supported by the support layer
material that remains post-thermal treatment. The article is then
submersed in an appropriate solvent to dissolve or disperse the
support layer. The article comprising the remaining build material
is removed from solvent and dried.
[0026] Table 1 gives the formulations for example 1
TABLE-US-00002 TABLE 1 Formulation for Example 1 PE1 CaCO.sub.3 CE1
25 75
* * * * *