IPC分类号：
B22F10/14 | B33Y10/00 | B33Y40/20 | B22F10/64 | B33Y30/00 | B29C64/30 | B29C64/165 | B22F12/10
当前申请(专利权)人：
UNIVERSITY OF FLORIDA RESEARCH FOUNDATION, INCORPORATED
原始申请(专利权)人：
UNIVERSITY OF FLORIDA RESEARCH FOUNDATION
当前申请(专利权)人地址：
223 GRINTER HALL, 32611, GAINESVILLE, FLORIDA
发明人：
HUANG, YONG | SOLE GRAS, MARC | REN, BING
摘要：
A three-dimensional (3D) printing method and apparatus are disclosed for freeform fabrication of metal articles. 3D printed articles are formed from a build material comprising metal powder(s), polymer(s), and solvent(s). A coagulation agent, such as a nebulized non-solvent, is disposed onto/about the build material during 3D printing to cause at least partial solidification of the build material to form a green body structure. Multiple build materials can be mixed at a variable ratio to achieve a composition gradient through the green body structure. The 3D printed green body structure can be heated to remove some or all of the polymer, solvent, and/or for debinding. The debinded green body structure can be sintered at a specific sintering temperature or over a temperature gradient, for a period of time, in accordance with the sintering properties of the particular metal powder in the debinded green body structure, to form a finished metal part.
技术问题语段：
However, conventional methods and compositions are typically not appropriate for printing metallic parts.
技术功效语段：
[0004]A three-dimensional (3D) printing method and associated apparatus are disclosed for fabrication of 3D printed metal structures and articles. In some embodiments, the fabrication may be freeform or additive fabrication. In some embodiments, the 3D printed structures and articles may be formed from a build material, such as a build material comprising one or more metal powders, one or more binder materials, and one or more solvents. In some embodiments, at least partial solidification of the build material after printing can be facilitated with one or more coagulation agents, such as a non-solvent material or the like. In some embodiments, the at least partially solidified article can be referred to as a green body structure, and may, optionally, be fully solidified by submerging the green body structure in to a coagulation bath or by other means of exposing the green body structure to one or more coagulation agents or the like. In some embodiments, the green body structure can be heated to remove some or all of the one or more polymeric materials, some or all of the one or more solvents, and/or other materials, impurities, and/or contaminants from the green body structure. In some embodiments, the green body structure can be sintered at one or more temperatures or over a temperature gradient, for a period of time, e.g., in accordance with the sintering properties of the particular one or more metal powders in the green body structure.
[0009]In some embodiments, a method can comprise, optionally, dissolving one or more polymeric materials in one or more solvents to form an intermediate build material, and then dispersing or otherwise disposing one or more metal powders into the intermediate build material to form a build material (also called herein “the liquid build material,”“the ink,”“the printing material,” or “the printing suspension”). In some embodiments, the build material can comprise any suitable polymeric material such as a thermoplastic. In some embodiments, the one or more polymeric materials can be dissolved or dispersed in the one or more solvents, which can comprise any suitable solvent, e.g., based upon the interaction/dissolution chemistry of the one or more polymeric materials and the chosen one or more solvents. In some embodiments, such a solvent can comprise dimethyl sulfoxide (DMSO), and/or the like. In some embodiments, to form the build material, the one or more polymeric materials can be dissolved in the one or more solvents partially or fully, at about room temperature (about 20° C. to about 25° C.), or at an elevated temperature, while being stirred, shaken, agitated, bombarded with electromagnetic radiation and/or ultrasonic sound waves, or the like. In some embodiments, one or more solvents can be chosen that are capable of breaking down the one or more polymeric materials without causing molecular degradation or a reduction in the degree of polymerization (DP). The build material can further be formed by dispersing or disposing one or more metal powders in the polymer/solvent solution. In some embodiments, the room temperature process for forming the build material, according to some embodiments described herein, may require little or no heating of the printing materials, may result in little or no thermal deterioration of the polymers, and can reduce or eliminate the need for heating and/or melting the one or more polymeric materials before printing the green body structure.
权利要求：
1. A method comprising:
disposing a printing material into a printing space according to a form factor associated with an article, the printing material comprising a plurality of metal particles, a binder material, and a non-aqueous solvent;
disposing a selective binding-enabling material into the printing space, thereby causing selective binding together of at least a portion of the printing material to maintain the printing material in the form factor, the selective binding-enabling material comprising one or more of: water, deionized water, water vapor, water having a miscible solvent dissolved therein, or a non-solvent having a mutual miscibility with the non-aqueous solvent that satisfies a predetermined miscibility threshold;
after disposing the printing material and the selective binding-enabling material into the printing space, heating the printing space to about a first temperature such that at least a portion of at least one of the non-aqueous solvent, the selective binding-enabling material, or the binder material volatilizes, forming a green body structure; and
heating the printing space to about a second temperature higher than the first temperature such that the green body structure sinters, forming the article.
2. The method of claim 1, wherein the plurality of metal particles comprise one or more from among: iron, nickel, copper, silver, chromium, tin, titanium, cobalt, tungsten, vanadium, scandium, palladium, platinum, aluminum, gold, molybdenum, manganese, tantalum, beryllium, bismuth, hafnium, iridium, lanthanum, magnesium, niobium, osmium, silicon, yttrium, zinc, or zirconium.
3. The method of claim 1, wherein the non-aqueous solvent comprises one or more of: dimethyl sulfoxide (DMSO), dimethylformamide (DMF), acetonitrile, ethanol, acetone, acrylic acid, benzene, benzyl alcohol, carbon tetrachloride, chloroform, cyclohexanol, dioxane, dimethylacetamide, ethyl acetate, ethyleneglycolmonobutylether, ethyleneglycolmonomethylether, formamide, methanol, methyl acetate, methylene dichloride, methyl-pyrrolidone, propanol, tetrahydrofuran, toluene, or trichloroethylene.
4. The method of claim 1, wherein the binder material comprises one or more of: a wax, a polymer, a gel, a semi-solid, or a metal.
5. A method comprising:
forming a green body structure having dimensions and a form factor associated with a digital design for a printed article, wherein forming the green body structure comprises:
preparing a print feedstock comprising metal particles, a binder material, and a non-aqueous solvent;
on a printing platform, forming an intermediary structure from the print feedstock;
contacting the intermediary structure with a selective binding-enabling material to cause selective binding of at least a portion of the print feedstock to form the green body structure, the selective binding-enabling material comprising one or more of: water, deionized water, water vapor, water having a miscible solvent dissolved therein, or a non-solvent having a mutual miscibility with the non-aqueous solvent that satisfies a predetermined miscibility threshold; and
debinding the green body structure at about a first temperature to remove at least a portion of one of: the non-aqueous solvent, the selective binding-enabling material, the or the binder volatilizes, thereby forming the green body structure, wherein
the method further comprises:
heating the green body structure to about a second temperature higher than the first temperature such that the green body structure sinters, forming the printed article.
6. The method of claim 5, wherein the metal particles comprise one or more from among: iron, nickel, copper, silver, chromium, tin, titanium, cobalt, tungsten, vanadium, scandium, palladium, platinum, aluminum, gold, molybdenum, manganese, tantalum, beryllium, bismuth, hafnium, iridium, lanthanum, magnesium, niobium, osmium, silicon, yttrium, zinc, or zirconium.
7. The method of claim 5, wherein the non-aqueous solvent comprises one or more of: dimethyl sulfoxide (DMSO), dimethylformamide (DMF), acetonitrile, ethanol, acetone, acrylic acid, benzene, benzyl alcohol, carbon tetrachloride, chloroform, cyclohexanol, dioxane, dimethylacetamide, ethyl acetate, ethyleneglycolmonobutylether, ethyleneglycolmonomethylether, formamide, methanol, methyl acetate, methylene dichloride, methyl-pyrrolidone, propanol, tetrahydrofuran, toluene, or trichloroethylene.
8. The method of claim 5, wherein the binder comprises one or more of: a wax, a polymer, a gel, a semi-solid, or a metal.
9. The method of claim 8, wherein the binder comprises one or more of: thermoplastic polymers, acrylonitrile-butadiene-styrene, polyurethane, acrylic, poly(acrylonitrile), polyolefins, polyvinyl chlorides, nylons, fluorocarbons, polystyrenes, polyethylene, ultra-high molecular weight polyethylene, polypropylene, polybutene, polymethylpentene, polyisoprene, polyethylene, ultra-high molecular weight polyethylene, polypropylene, ethylene-butene copolymers, ethylene-hexene copolymers, thermosetting plastics, polyimide (PI), poly amide (PA), poly amide imide (PAI), polypropylene (PP), polyethylene (PE), ethylene vinylacetate (EVA), poly(ethylene terephthalate) (PET), poly(vinyl acetate) (PVA), poly lactic-co-glycolic acid (PLGA), polylactic acid (PLA), polyamide (PA), acrylic adhesives, ultraviolet (UV)/electron beam (EB)/infrared (IR) curable resin, poly ether ether ketone (PEEK), polyethylene naphthalate (PEN), polyethersulfone (PES), polyphenylene sulfide (PPS), or polyphenylene oxide (PPO).
10. The method of claim 5, wherein:
the metal particles comprise iron, nickel, and silver,
the non-aqueous solvent comprises DMSO,
the binder comprises ABS, and
the selective binding-enabling material comprises deionized water particles.
11. The method of claim 10, further comprising:
disposing, using a nebulizer, a mist comprising the deionized water particles to a region about the intermediary article to cause partial coagulation of the intermediary article by exchanging the DMSO with the deionized water particles.
12. The method of claim 11, wherein forming the green body structure further comprises:
after partial coagulation of the intermediary article, disposing the intermediary structure in a coagulation bath for a duration of about one hour to further exchange the DMSO with the deionized water particles, thereby further coagulating the green body structure prior to sintering.
13. A method comprising:
forming a green body structure having dimensions and a form factor associated with a digital design for a printed article, wherein forming the green body structure comprises:
preparing a print feedstock comprising metal particles, a binder material, and a non-aqueous solvent;
on a printing platform, forming an intermediary structure from the print feedstock during a first time;
while forming the intermediary structure from the print feedstock, contacting the intermediary structure with a selective binding-enabling material to cause selective binding of at least a portion of the print feedstock to partially form the green body structure, the selective binding-enabling material comprising one or more of: water, deionized water, water vapor, water having a miscible solvent dissolved therein, or a non-solvent having a mutual miscibility with the non-aqueous solvent that satisfies a predetermined miscibility threshold; and
disposing the intermediary structure in a coagulation bath to cause further binding of the print feedstock to further form the green body structure, wherein the method further comprises:
after further binding of the print feedstock in the coagulation bath too further form the green body structure, heating the green body structure to above a predetermined temperature such that the green body structure sinters, forming the printed article.
14. The method of claim 13, wherein the metal particles comprise one or more from among: iron, nickel, copper, silver, chromium, tin, titanium, cobalt, tungsten, vanadium, scandium, palladium, platinum, aluminum, gold, molybdenum, manganese, tantalum, beryllium, bismuth, hafnium, iridium, lanthanum, magnesium, niobium, osmium, silicon, yttrium, zinc, or zirconium.
15. The method of claim 13, wherein the non-aqueous solvent comprises one or more of: dimethyl sulfoxide (DMSO), dimethylformamide (DMF), acetonitrile, ethanol, acetone, acrylic acid, benzene, benzyl alcohol, carbon tetrachloride, chloroform, cyclohexanol, dioxane, dimethylacetamide, ethyl acetate, ethyleneglycolmonobutylether, ethyleneglycolmonomethylether, formamide, methanol, methyl acetate, methylene dichloride, methyl-pyrrolidone, propanol, tetrahydrofuran, toluene, or trichloroethylene.
16. The method of claim 13, wherein the binder comprises one or more of: a wax, a polymer, a gel, a semi-solid, or a metal.
17. The method of claim 16, wherein the binder comprises one or more of: thermoplastic polymers, acrylonitrile-butadiene-styrene, polyurethane, acrylic, poly(acrylonitrile), polyolefins, polyvinyl chlorides, nylons, fluorocarbons, polystyrenes, polyethylene, ultra-high molecular weight polyethylene, polypropylene, polybutene, polymethylpentene, polyisoprene, polyethylene, ultra-high molecular weight polyethylene, polypropylene, ethylene-butene copolymers, ethylene-hexene copolymers, thermosetting plastics, polyimide (PI), poly amide (PA), poly amide imide (PAI), polypropylene (PP), polyethylene (PE), ethylene vinylacetate (EVA), poly(ethylene terephthalate) (PET), poly(vinyl acetate) (PVA), poly lactic-co-glycolic acid (PLGA), polylactic acid (PLA), polyamide (PA), acrylic adhesives, ultraviolet (UV)/electron beam (EB)/infrared (IR) curable resin, poly ether ether ketone (PEEK), polyethylene naphthalate (PEN), polyethersulfone (PES), polyphenylene sulfide (PPS), or polyphenylene oxide (PPO).
18. The method of claim 13, wherein:
the metal particles comprise iron, nickel, and silver,
the non-aqueous solvent comprises DMSO,
the binder comprises ABS, and
the selective binding-enabling material comprises deionized water particles.
19. The method of claim 18, further comprising:
disposing, using a nebulizer, a mist comprising the deionized water particles to a region about the intermediary article to cause partial coagulation of the intermediary article by exchanging the DMSO with the deionized water particles.
20. The method of claim 19, wherein the intermediary structure is disposed in the coagulation bath for a duration of about one hour to promote further exchange of the DMSO with the deionized water particles, thereby further coagulating the green body structure prior to sintering.
技术领域：
[0002]Embodiments described herein relate generally to additive manufacturing, and more particularly to freeform additive manufacturing of metal articles.
背景技术：
[0003]Additive manufacturing, also commonly known as three-dimensional (3D) printing, encompasses a range of technologies used to fabricate parts by adding material to build up the part rather than by subtracting unwanted material away from a bulk starting workpiece. For freeform 3D printing of functional structures, extrusion, sometimes known as direct ink writing, can be used due to its ease of implementation, high efficiency, and wide range of printable materials. However, conventional methods and compositions are typically not appropriate for printing metallic parts. Through applied effort, ingenuity, and innovation, solutions to improve such apparatuses, systems, and methods have been realized and are described in connection with embodiments of the present invention.
发明内容：
[0004]A three-dimensional (3D) printing method and associated apparatus are disclosed for fabrication of 3D printed metal structures and articles. In some embodiments, the fabrication may be freeform or additive fabrication. In some embodiments, the 3D printed structures and articles may be formed from a build material, such as a build material comprising one or more metal powders, one or more binder materials, and one or more solvents. In some embodiments, at least partial solidification of the build material after printing can be facilitated with one or more coagulation agents, such as a non-solvent material or the like. In some embodiments, the at least partially solidified article can be referred to as a green body structure, and may, optionally, be fully solidified by submerging the green body structure in to a coagulation bath or by other means of exposing the green body structure to one or more coagulation agents or the like. In some embodiments, the green body structure can be heated to remove some or all of the one or more polymeric materials, some or all of the one or more solvents, and/or other materials, impurities, and/or contaminants from the green body structure. In some embodiments, the green body structure can be sintered at one or more temperatures or over a temperature gradient, for a period of time, e.g., in accordance with the sintering properties of the particular one or more metal powders in the green body structure.
[0005]In some embodiments, 3D printed structures and articles may be fabricated under ambient conditions and/or without the use of printed support structures which would need to be removed after 3D printing in order to achieve the finished structure or article. In some embodiments, a build material can be generated by combining one or more polymers and one or more solvents, such as by dissolved the one or more polymers in the one or more solvents, and adding the one or more metal powders. In some embodiments, the build material can be referred to as “the ink,”“the printing material,” or the like. In some embodiments, the build material can be disposed within a printing volume or onto a printing platform without the use of supports or other structures being previously, concurrently, or subsequently printed to support the build material while the build material solidifies or partially solidifies. In some embodiments, freeform printing can be carried out at ambient temperature and pressure. In some embodiments, just previous to, concurrent with, or just following the disposition of the build material into the printing volume or onto the printing platform, a volume of one or more coagulation agents, such as a coagulant, a non-solvent, variations thereof, or combinations thereof, can be disposed, such as by an aerosol sprayer or other suitable dispensing mechanism, to a volume directly adjacent the disposed build material. Without wishing to be bound by any particular theory, the one or more coagulation agents can cause partial, substantially complete, or complete coagulation, solidification, polymerization, phase inversion, cross-linking, crystallization, calcification, concretion, setting, stiffening, hardening, amalgamation, strengthening, gelation, congealing, thickening, densification, annealing, shaping, forming, clotting, variations thereof, combinations thereof, or other suitable changes to the one or more polymeric materials, thus forming a green body structure. As such, in some embodiments, a first volume of the build material can be printed, e.g., by a nozzle or the like, in a freeform manner directly into air and the one or more polymeric materials can be partially or fully solidified by disposing a first volume of the one or more coagulation agents sufficiently close by the printed first volume of the build material. In some embodiments, the nozzle can then be moved a distance, in one or more directions within the printing volume or across the printing platform, from the previous printing location, and the nozzle can be used to print a second volume of the build material, e.g., adjacent the first volume of the build material which is now partially or fully solidified. In some embodiments, a second volume of the coagulation agent can be disposed nearby the second volume of printed build material to partially or fully solidify the second volume of build material. In some embodiments, such a method or approach can be continued along a predetermined path of travel by the nozzle through the printing volume or across the printing platform in order to completely print the green body structure without being required to melt the one or more polymeric materials in the build material and allow them to solidify once printed, without using support structures, and/or without using a support bath or the like to maintain the structure of the printed article prior to completion of printing of the article. In some embodiments, the green body structure may be one in which some or all of the one or more polymeric materials are only partially solidified or for which further processing is helpful or required to achieve the fully solidified or fully coagulated green body structure in which some, most, or all of the one or more solvents are removed and/or in which some, most, or all of the one or more polymeric materials are solidified or coagulated. In some embodiments, the green body structure, once the one or more polymeric materials are fully or substantially fully coagulated and solidified, can be heated to remove some or all of the one or more solvents and/or some or all of the one or more polymeric materials. In some embodiments, heating can comprise heating the green body structure at a particular rate, from a first particular temperature (e.g., ambient or room temperature) to a second particular temperature (e.g., at which the one or more solvents are vaporized). In some embodiments, the green body structure can then be sintered in order to remove some or all of the one or more polymeric materials and cause inter-particle fusing of the one or more metal powders, thereby forming the finished metal article.
[0006]In some embodiments, a method for three-dimensional printing of a metal article can comprise: providing a printing suspension comprising: one or more solvents, one or more binder materials, and one or more metal powders; printing the printing suspension into a printing space in accordance with one or more printing pathways; and disposing, concurrent with said printing, one or more non-solvents into the printing space at a location nearby the printed printing suspension, thereby forming a green body structure having dimensions that are within a predetermined range of the dimensions of the metal part. In some embodiments, the one or more non-solvents are operable to extract at least a portion of the one or more solvents from the green body structure. In some embodiments, once at least the portion of the one or more solvents are extracted from the green body structure, the one or more binder materials become at least partially solidified such that the green body structure experiences substantially no deformation, at a temperature, a pressure, and a humidity, over a period of time. In some embodiments, the one or more binder materials comprise one or more polymers that are configured to undergo a phase inversion in the presence of the one or more non-solvents. In some embodiments, the method can further comprise, in an instance in which only the portion of the one or more solvents are extracted from the green body structure such that the one or more binder materials become only partially solidified, disposing the green body structure into a coagulation bath to extract a remainder of the one or more solvents from the green body structure, thereby causing substantially complete solidification of the one or more binder materials. In some embodiments, the method can further comprise: heating the green body structure such that any remaining portion of the one or more solvents and the one or more binder materials are removed from the green body structure. In some embodiments, the heating causes at least partial vaporization of at least one of the remaining portion of the one or more solvents and the one or more binder materials. In some embodiments, the heating comprises sintering the green body structure, for a predetermined time, at a predetermined temperature, to form the metal part. In some embodiments, the printing is carried out using one or more printing nozzles. In some embodiments, the printing comprises an additive manufacturing process. In some embodiments, the method further comprises: providing a first material comprising the one or more solvents; disposing the one or more binder materials into the first material, causing the one or more binder materials to at least partially dissolve, and thereby forming a second material; and dispersing the one or more metal powders into the second material to form the printing suspension. In some embodiments, the printing comprises printing, using one or more nozzles, the printing suspension into the printing space at a first rate, wherein said disposing the one or more non-solvents comprises disposing the one or more non-solvents, at a second rate controlled according to the first rate of said printing of the printing suspension, nearby the one or more nozzles such that the one or more non-solvents are disposed sufficiently nearby the printing suspension as it is printed from the one or more nozzles. In some embodiments, the one or more binder materials have a volatilization temperature less than a sintering temperature of the one or more metal powders. In some embodiments, the printing is done at a first temperature substantially equivalent to room temperature. In some embodiments, the method can further comprise: vaporizing the one or more binder materials at a second temperature greater than the first temperature; and sintering the one or more metal powders at a third temperature greater than the second temperature. In some embodiments, the one or more metal powders may comprise at least one from among: iron, nickel, copper, silver, chromium, tin, titanium, cobalt, tungsten, vanadium, scandium, palladium, platinum, aluminum, gold, molybdenum, manganese, tantalum, beryllium, bismuth, hafnium, iridium, lanthanum, magnesium, niobium, osmium, silicon, yttrium, zinc, zirconium, other metals or metalloids, alloys thereof, mixtures thereof, or combinations thereof. In some embodiments, the one or more solvents may comprise at least one from among: dimethyl sulfoxide, dimethylformamide (DMF), acetonitrile, ethanol, acetone, acrylic acid, benzene, benzyl alcohol, carbon tetrachloride, chloroform, cyclohexanol, dioxane, dimethylacetamide, ethyl acetate, ethyleneglycolmonobutylether, ethyleneglycolmonomethylether, formamide, methanol, methyl acetate, methylene dichloride, methyl-pyrrolidone, propanol, tetrahydrofuran, toluene, trichloroethylene, other applicable solvents, variants thereof, mixtures thereof, or combinations thereof. In some embodiments, the one or more binder materials may comprise at least one from among: a wax, a polymer, a gel, a semi-solid, or a metal. In some embodiments, the one or more binder materials may comprise at least one from among: thermoplastic polymers, acrylonitrile-butadiene-styrene, polyurethane, acrylic, poly(acrylonitrile), polyolefins, polyvinyl chlorides, nylons, fluorocarbons, polystyrenes, polyethylene, ultra-high molecular weight polyethylene, polypropylene, polybutene, polymethylpentene, polyisoprene, polyethylene, ultra-high molecular weight polyethylene, polypropylene, ethylene-butene copolymers, ethylene-hexene copolymers, thermosetting plastics, polyimide (PI), poly amide (PA), poly amide imide (PAI), polypropylene (PP), polyethylene (PE), ethylene vinylacetate (EVA), poly(ethylene terephthalate) (PET), poly(vinyl acetate) (PVA), poly lactic-co-glycolic acid (PLGA), polylactic acid (PLA), polyamide (PA), acrylic adhesives, ultraviolet (UV)/electron beam (EB)/infrared (IR) curable resin, polyether ether ketone (PEEK), polyethylene naphthalate (PEN), polyethersulfone (PES), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), copolymers thereof, variants thereof, or combinations thereof. In some embodiments, the one or more non-solvents may comprise one or more of water, deionized water, water vapor, water having a miscible solvent dissolved therein, a non-solvent having a mutual miscibility with the chosen one or more solvents that satisfies a predetermined miscibility threshold, variants thereof, and combinations thereof.
[0007]In some embodiments, a method is provided for three-dimensional (3D) printing of a metal part, the method comprising: providing a first printing suspension comprising one or more first solvents, one or more first binder materials, and one or more first metal powders; providing a second printing suspension comprising one or more second solvents, one or more second binder materials, and one or more second metal powders; printing, during a first time, the first printing suspension into a printing space in accordance with one or more first printing pathways from the first nozzle; disposing, concurrent with said printing during the first time, one or more first non-solvents into the printing space at a first location nearby the printed first printing suspension, thereby forming a first portion of a green body structure; printing, during a second time, the second printing suspension into the printing space in accordance with one or more second printing pathways from the second nozzle; disposing, concurrent with said printing during the second time, one or more second non-solvents into the printing space at a second location nearby the printed second printing suspension, thereby forming a second portion of the green body structure, wherein the one or more first metal powder compositions are different from the one or more second metal powder compositions such that the first portion of the green body structure has a composition different from the composition of the second portion of the green body structure; vaporizing the remaining one or more solvents, the one or more first binder materials and the one or more second binder materials; and sintering the one or more first metal powders and the one or more second metal powders to form the metal part.
[0008]In some embodiments, a method is provided for three-dimensional (3D) printing of a metal part, the method comprising: providing a first printing suspension comprising one or more first solvents, one or more first binder materials, and one or more first metal powders; providing a second printing suspension comprising one or more second solvents, one or more second binder materials, and one or more second metal powders; mixing, actively or passively from two or more inlets, the two or more printing suspensions resulting on a controllable variable ratio of the obtained ink; printing, the resulting printing suspension into a printing space in accordance with one or more printing pathways from a single or multiple nozzles; disposing, concurrent with said printing during the time, one or more non-solvents into the printing space at the location nearby the printed printing suspension, thereby forming a green body structure; such that the composition of the green body structure has a varying composition at each deposition time; vaporizing the remaining one or more solvents, the one or more first binder materials and the one or more second binder materials; and sintering the one or more first metal powders and the one or more second metal powders to form the metal part.
[0009]In some embodiments, a method can comprise, optionally, dissolving one or more polymeric materials in one or more solvents to form an intermediate build material, and then dispersing or otherwise disposing one or more metal powders into the intermediate build material to form a build material (also called herein “the liquid build material,”“the ink,”“the printing material,” or “the printing suspension”). In some embodiments, the build material can comprise any suitable polymeric material such as a thermoplastic. In some embodiments, the one or more polymeric materials can be dissolved or dispersed in the one or more solvents, which can comprise any suitable solvent, e.g., based upon the interaction/dissolution chemistry of the one or more polymeric materials and the chosen one or more solvents. In some embodiments, such a solvent can comprise dimethyl sulfoxide (DMSO), and/or the like. In some embodiments, to form the build material, the one or more polymeric materials can be dissolved in the one or more solvents partially or fully, at about room temperature (about 20° C. to about 25° C.), or at an elevated temperature, while being stirred, shaken, agitated, bombarded with electromagnetic radiation and/or ultrasonic sound waves, or the like. In some embodiments, one or more solvents can be chosen that are capable of breaking down the one or more polymeric materials without causing molecular degradation or a reduction in the degree of polymerization (DP). The build material can further be formed by dispersing or disposing one or more metal powders in the polymer/solvent solution. In some embodiments, the room temperature process for forming the build material, according to some embodiments described herein, may require little or no heating of the printing materials, may result in little or no thermal deterioration of the polymers, and can reduce or eliminate the need for heating and/or melting the one or more polymeric materials before printing the green body structure.
[0010]According to another embodiment, an apparatus can be provided for 3D printing a metal article. In some embodiments, the apparatus can comprise: a printing space comprising an air-filled inner volume and a printing substrate; a reservoir configured to contain a supply of a liquid build material; a nozzle coupled to the reservoir and configured to dispose a volume of the liquid build material into the air-filled inner volume of the printing space; a nebulizer configured to nebulize a coagulation agent and disperse the nebulized coagulation agent within a predetermined distance of the disposed volume of liquid build material to at least partially coagulate the disposed volume of liquid build material; and a computing device configured to control movement of the nozzle and the disposing of the volume of the liquid build material into the air-filled inner volume of the printing space. In some embodiments, the nebulized coagulation agent may only partially coagulate the disposed volume of liquid build material to form an intermediate article. As such, in some embodiments, the apparatus can further comprise, optionally, a solidification bath comprising a coagulation solution, the solidification bath configured to, in an instance in which the nebulized coagulation agent only partially coagulates the disposed volume of liquid build material, receive the intermediate article and cause, via the coagulation fluid, the intermediate article to fully solidify, thereby forming the finished article.
[0011]According to an embodiment, a method can be carried out that comprises: disposing a printing material into a printing space according to a form factor associated with an article, the printing material comprising a plurality of metal particles, a binder material, and a solvent; and disposing a non-solvent into the printing space, thereby causing selective binding at least a portion of said printing material together to maintain said form factor of said article. In some embodiments, the printing material and the non-solvent are disposed into the printing space during a first time. In some embodiments, the method can further comprise: during a second time following the first time, heating said printing material to about a first temperature. In some embodiments, once the printing material is heated to said first temperature, a portion of at least one of the solvent, the non-solvent, or the binder volatilizes, forming a green body structure. In some embodiments, the method can further comprise: during a third time following the second time, heating said printing material to about a second temperature, the second temperature being higher than the first temperature. In some embodiments, once the printing material is heated to said second temperature, the green body structure sinters, forming the article.
[0012]According to another embodiment, an apparatus can be provided that comprises: means, such as a processor, a memory storing computer instructions, additive manufacturing equipment, a reservoir for storing build material or the like, one or more printing nozzles, a nebulizer, a printing volume, and/or the like. In some embodiments, the apparatus can comprise: means for disposing a printing material into a printing space according to a form factor associated with an article, the printing material comprising a plurality of metal particles, a binder material, and a solvent; and means for disposing a non-solvent into the printing space, thereby causing selective binding at least a portion of said printing material together to maintain said form factor of said article. In some embodiments, the printing material and the non-solvent are disposed into the printing space during a first time. In some embodiments, the apparatus can further comprise: means for, during a second time following the first time, heating said printing material to about a first temperature. In some embodiments, once the printing material is heated to said first temperature, a portion of at least one of the solvent, the non-solvent, or the binder volatilizes, forming a green body structure. In some embodiments, the apparatus can further comprise: means for, during a third time following the second time, heating said printing material to about a second temperature, the second temperature being higher than the first temperature. In some embodiments, once the printing material is heated to said second temperature, the green body structure sinters, forming a finished metal article.
[0013]According to yet another embodiment, a method for three-dimensional (3D) printing a metal part can be carried out, the method comprising: providing a printing suspension comprising: one or more solvents, one or more binder materials, and one or more metal powders; printing the printing suspension into a printing space in accordance with one or more printing pathways; and disposing, concurrent with said printing, one or more non-solvents into the printing space at a location nearby the printed printing suspension, thereby forming a green body structure having dimensions that are within a predetermined range of the dimensions of the metal part. In some embodiments, the one or more non-solvents are operable to extract at least a portion of the one or more solvents from the green body structure. In some embodiments, once at least the portion of the one or more solvents are extracted from the green body structure, the one or more binder materials become at least partially solidified such that the green body structure experiences substantially no deformation, at a temperature, a pressure, and a humidity, over a period of time. In some embodiments, the one or more binder materials comprise one or more polymers that are configured to undergo a phase inversion in the presence of the one or more non-solvents. In some embodiments, the method can further comprise: in an instance in which only the portion of the one or more solvents are extracted from the green body structure such that the one or more binder materials become only partially solidified, disposing the green body structure into a coagulation bath to extract a remainder of the one or more solvents from the green body structure, thereby causing substantially complete solidification of the one or more binder materials. In some embodiments, the method can further comprise: heating the green body structure such that any remaining portion of the one or more solvents and the one or more binder materials are removed from the green body structure. In some embodiments, said heating causes at least partial vaporization of at least one of the remaining portion of the one or more solvents and the one or more binder materials. In some embodiments, said heating comprises sintering the green body structure, for a predetermined time, at a predetermined temperature, to form the metal part. In some embodiments, said printing is carried out using one or more printing nozzles. In some embodiments, said printing comprises an additive manufacturing process. In some embodiments, the method can further comprise: providing a first material comprising the one or more solvents; disposing the one or more binder materials into the first material, causing the one or more binder materials to at least partially dissolve, and thereby forming a second material; and dispersing the one or more metal powders into the second material to form the printing suspension. In some embodiments, said printing comprises printing, using one or more nozzles, the printing suspension into the printing space at a first rate, wherein said disposing the one or more non-solvents comprises disposing the one or more non-solvents, at a second rate controlled according to the first rate of said printing of the printing suspension, nearby the one or more nozzles such that the one or more non-solvents are disposed sufficiently nearby the printing suspension as it is printed from the one or more nozzles. In some embodiments, the one or more binder materials have a volatilization temperature less than a sintering temperature of the one or more metal powders. In some embodiments, said printing is done at a first temperature substantially equivalent to room temperature, the method further comprising: vaporizing the one or more binder materials at a second temperature greater than the first temperature; and sintering the one or more metal powders at a third temperature greater than the second temperature. In some embodiments, the one or more metal powders may comprise at least one from among: iron, nickel, copper, silver, chromium, tin, titanium, cobalt, tungsten, vanadium, scandium, palladium, platinum, aluminum, gold, molybdenum, manganese, tantalum, beryllium, bismuth, hafnium, iridium, lanthanum, magnesium, niobium, osmium, silicon, yttrium, zinc, zirconium, other metals or metalloids, alloys thereof, variants thereof, mixtures thereof, or combinations thereof. In some embodiments, the one or more solvents may comprise at least one from among: dimethyl sulfoxide, dimethylformamide (DMF), acetonitrile, ethanol, acetone, acrylic acid, benzene, benzyl alcohol, carbon tetrachloride, chloroform, cyclohexanol, dioxane, dimethylacetamide, ethyl acetate, ethyleneglycolmonobutylether, ethyleneglycolmonomethylether, formamide, methanol, methyl acetate, methylene dichloride, methyl-pyrrolidone, propanol, tetrahydrofuran, toluene, trichloroethylene, other applicable solvents, variants thereof, mixtures thereof, or combinations thereof. In some embodiments, the one or more binder materials may comprise at least one from among: a wax, a polymer, a gel, a semi-solid, or a metal. In some embodiments, the one or more binder materials may comprise at least one from among: thermoplastic polymers, acrylonitrile-butadiene-styrene, polyurethane, acrylic, poly(acrylonitrile), polyolefins, polyvinyl chlorides, nylons, fluorocarbons, polystyrenes, polyethylene, ultra-high molecular weight polyethylene, polypropylene, polybutene, polymethylpentene, polyisoprene, polyethylene, ultra-high molecular weight polyethylene, polypropylene, ethylene-butene copolymers, ethylene-hexene copolymers, thermosetting plastics, polyimide (PI), poly amide (PA), poly amide imide (PAI), polypropylene (PP), polyethylene (PE), ethylene vinylacetate (EVA), poly(ethylene terephthalate) (PET), poly(vinyl acetate) (PVA), poly lactic-co-glycolic acid (PLGA), polylactic acid (PLA), polyamide (PA), acrylic adhesives, ultraviolet (UV)/electron beam (EB)/infrared (IR) curable resin, polyether ether ketone (PEEK), polyethylene naphthalate (PEN), polyethersulfone (PES), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), copolymers thereof, variants thereof, or combinations thereof. In some embodiments, the one or more non-solvents may comprise one or more of: water, deionized water, water vapor, steam, water droplets, water having a miscible solvent dissolved therein, a non-solvent having a mutual miscibility with the chosen one or more solvents that satisfies a predetermined miscibility threshold, variants thereof, or combinations thereof.
[0014]According to still another embodiment, a method for three-dimensional (3D) metal printing can be carried out, the method comprising: providing a first printing suspension comprising one or more first solvents, one or more first binder materials, and one or more first metal powders; providing a second printing suspension comprising one or more second solvents, one or more second binder materials, and one or more second metal powders; printing, during a first time, the first printing suspension into a printing space in accordance with one or more first printing pathways; disposing, concurrent with said printing during the first time, one or more first non-solvents into the printing space at a first location nearby the printed first printing suspension, thereby forming a first portion of a green body structure; printing, during a second time, the second printing suspension into the printing space in accordance with one or more second printing pathways; and disposing, concurrent with said printing during the second time, one or more second non-solvents into the printing space at a second location nearby the printed second printing suspension, thereby forming a second portion of the green body structure, wherein the one or more first metal powder compositions are different from the one or more second metal powder compositions such that the first portion of the green body structure has a composition different from the composition of the second portion of the green body structure. In some embodiments, the method can further comprise: vaporizing the remaining one or more solvents, the one or more first binder materials and the one or more second binder materials. In some embodiments, the method can further comprise: sintering the one or more first metal powders and the one or more second metal powders to form a metal part, said metal part having a form factor substantially similar to that of the green body structure. In some embodiments, at least one of the one or more first metal powders and the one or more second metal powders may comprise at least one from among: iron, nickel, copper, silver, chromium, tin, titanium, cobalt, tungsten, vanadium, scandium, palladium, platinum, aluminum, gold, molybdenum, manganese, tantalum, beryllium, bismuth, hafnium, iridium, lanthanum, magnesium, niobium, osmium, silicon, yttrium, zinc, zirconium, other metals or metalloids, alloys thereof, variants thereof, mixtures thereof, or combinations thereof. In some embodiments, at least one of the one or more first solvents or the one or more second solvents may comprise at least one from among: dimethyl sulfoxide, dimethylformamide (DMF), acetonitrile, ethanol, acetone, acrylic acid, benzene, benzyl alcohol, carbon tetrachloride, chloroform, cyclohexanol, dioxane, dimethylacetamide, ethyl acetate, ethyleneglycolmonobutylether, ethyleneglycolmonomethylether, formamide, methanol, methyl acetate, methylene dichloride, methyl-pyrrolidone, propanol, tetrahydrofuran, toluene, trichloroethylene, other applicable solvents, variants thereof, mixtures thereof, or combinations thereof. In some embodiments, at least one of the one or more first binder materials or the one or more second binder materials may comprise at least one from among: a wax, a polymer, a gel, a semi-solid, or a metal. In some embodiments, at least one of the one or more first binder materials or the one or more second binder materials may comprise at least one from among: thermoplastic polymers, acrylonitrile-butadiene-styrene, polyurethane, acrylic, poly(acrylonitrile), polyolefins, polyvinyl chlorides, nylons, fluorocarbons, polystyrenes, polyethylene, ultra-high molecular weight polyethylene, polypropylene, polybutene, polymethylpentene, polyisoprene, polyethylene, ultra-high molecular weight polyethylene, polypropylene, ethylene-butene copolymers, et
具体实施方式：
[0033]Various embodiments of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. The term “or” is used herein in both the alternative and conjunctive sense, unless otherwise indicated. The terms “illustrative,”“exemplary,” and “example” are often used to indicate preferred examples, but is not meant to convey any indication of quality level, either relative to other intrinsic examples or relative to extrinsic examples. Like numbers refer to like elements throughout.
[0034]As used herein, the terms “instructions,”“file,”“designs,”“data,”“content,”“information,” and similar terms may be used interchangeably, according to some example embodiments of the present invention, to refer to data capable of being transmitted, received, operated on, displayed, and/or stored. Thus, use of any such terms should not be taken to limit the spirit and scope of the disclosure. Further, where a computing device is described herein to receive data from another computing device, it will be appreciated that the data may be received directly from the other computing device or may be received indirectly via one or more computing devices, such as, for example, one or more servers, relays, routers, network access points, base stations, and/or the like.
[0035]As used herein, the term “computer-readable medium” as used herein refers to any medium configured to participate in providing information to a processor, including instructions for execution. Such a medium may take many forms, including, but not limited to a non-transitory computer-readable storage medium (for example, non-volatile media, volatile media), and transmission media. Transmission media include, for example, coaxial cables, copper wire, fiber optic cables, and carrier waves that travel through space without wires or cables, such as acoustic waves and electromagnetic waves, including radio, optical and infrared waves. Signals include man-made transient variations in amplitude, frequency, phase, polarization or other physical properties transmitted through the transmission media. Examples of non-transitory computer-readable media include a floppy disk, a flexible disk, hard disk, magnetic tape, any other non-transitory magnetic medium, a compact disc read only memory (CD-ROM), compact disc compact disc-rewritable (CD-RW), digital versatile disc (DVD), Blu-Ray, any other non-transitory optical medium, punch cards, paper tape, optical mark sheets, any other physical medium with patterns of holes or other optically recognizable indicia, a random access memory (RAM), a programmable read only memory (PROM), an erasable programmable read only memory (EPROM), a FLASH-EPROM, any other memory chip or cartridge, a carrier wave, or any other non-transitory medium from which a computer can read. The term computer-readable storage medium is used herein to refer to any computer-readable medium except transmission media. However, it will be appreciated that where embodiments are described to use a computer-readable storage medium, other types of computer-readable mediums may be substituted for or used in addition to the computer-readable storage medium in alternative embodiments. By way of example only, a design file for a printed article may be stored on a computer-readable medium and may be read by a computing device, such as described hereinbelow, for controlling part or all of a 3D printing process and associated apparatuses and components, according to various embodiments described herein.
[0036]As used herein, the term “circuitry” refers to all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry); (b) to combinations of circuits and computer program product(s) comprising software (and/or firmware instructions stored on one or more computer readable memories), such as (as applicable): (i) to a combination of processor(s) or (ii) to portions of processor(s)/software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions described herein); and (c) to circuits, such as, for example, a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present. This definition of “circuitry” applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term “circuitry” would also cover an implementation of merely a processor (or multiple processors) or portion of a processor and its (or their) accompanying software and/or firmware. The term “circuitry” would also cover, for example and if applicable to the particular claim element, a baseband integrated circuit or applications processor integrated circuit for a mobile phone or a similar integrated circuit in a server, a cellular network device, other network device, and/or other computing device.
[0037]As used herein, the term “computing device” refers to a specialized, centralized device, network, or system, comprising at least a processor and a memory device including computer program code, and configured to provide guidance or direction related to the charge transactions carried out in one or more charging networks.
[0038]As used herein, the terms “about,”“substantially,” and “approximately” generally mean plus or minus 10% of the value stated, e.g., about 250 μm would include 225 μm to 275 μm, about 1,000 μm would include 900 μm to 1,100 μm. Any provided value, whether or not it is modified by terms such as “about,”“substantially,” or “approximately,” all refer to and hereby disclose associated values or ranges of values thereabout, as described above.
[0039]Additive manufacturing, also referred to as three-dimensional (3D) printing, encompasses a range of technologies used to fabricate parts by building material up rather than by subtracting unwanted material away from a bulk starting workpiece.
[0040]Compared to traditional manufacturing, 3D printing enables mass customization, more freedom of designs to achieve complex structures, and reduced waste. Of various 3D printing build materials, metallic materials are particularly interesting due to their industrial application.
[0041]Conventionally, in order to achieve the goal of metal 3D printing, technologies such as energy-driven powder bed fusion and directed energy deposition have been discussed, however both technologies involve the partial or complete phase change of starting metallic power materials during printing. Such metal printing processes also typically require a high working temperature and controlled ambient environment. Likewise, these and other conventional technologies typically fail to achieve a suitably durable finished article with dimensions and a form factor that adequately reflect an initial digital design for the printed article.
[0042]Thus, the inventors have conceived of and diligently reduced to practice multiple embodiments of a system, method, compositions of matter, and apparatus for three-dimensional (3D) printing that enables freeform fabrication of metal structures and articles. According to some embodiments, such freeform fabrication can be carried out under ambient conditions. According to these and/or other embodiments, such freeform fabrication can be carried out without the use of support structures (e.g., printed support structures, solid support structures, support structures that are inherent to the printed article or the printing platform, support structures that should or must be removed after printing and before the printed article is ready for use, and/or the like). According to some embodiments, a build material (e.g., comprising one or more polymeric materials, one or more solvents, and one or more metal powders) can be prepared for printing according to a variety of possible printing methods (e.g., extrusion, injection, etc.) within an air-filled volume.
[0043]In some embodiments, an approach is provided for printing a 3D metallic green parts or green body structures from a build material comprising one or more sacrificial binder material-containing powder suspensions and solidified based on the phase inversion of the sacrificial binder material(s). According to some embodiments, the printed metallic green parts can be further sintered to for finished metallic parts while burning away the sacrificial binder material(s). In some embodiments, a metal printing approach is provided in which a sacrificial material (e.g., one or more polymeric materials) is used in the build material such that the build material can be directly printed to form the metallic green structures at room temperature. In some embodiments, the metallic green structures or green body structures can then be processed (e.g., thermally, chemically, radiologically, physically, via other suitable approaches, or combinations thereof) to remove the one or more polymeric materials and/or to sinter the metallic powders to form the finished metal article or part.
[0044]In some embodiments, the build material can be produced by mixing metallic powders with a polymeric solution, the polymeric solution comprising one or more polymeric materials disposed or dissolved in one or more solvents. In some embodiments, the one or more polymeric materials may function as a binder for the one or more metal powders and may act as a sacrificial material to be removed after green body formation and before or during sintering. In some embodiments, the build material is then printed into an air-filled printing space to form a 3D part. In some embodiments, one or more nozzles can be used to dispose or print the build material into the printing space at one or more particular points corresponding to a respective portion of a digital design of the part or article being printed. In some embodiments, a dispensing mechanism such as extrusion or ink-jetting nozzles may be used to print the build material into the printing space. In some embodiments, before, during, and/or after printing the build material, one or more coagulation agents (e.g., comprising a non-solvent agent) can be delivered to the part being printed (e.g., at or nearby the point within the printing space in which the building material is being printed). Without wishing to be bound by any particular theory, upon exposure of the printed, liquid build material to the one or more coagulation agents, the build material may become at least partially solidified at least in part due to a reaction between and/or an exchange of the one or more coagulation agents with the one or more solvents, which may result in the cross-linking and/or coagulation of the one or more polymeric materials. Once partially or fully solidified, the build material will retain the shape, size, position, and orientation as printed and the one or more nozzles can be moved further along a predetermined path of travel within the printing space and continue to be used to print other portions of the build material into the printing space at other points that correspond to other portions of the digital design for the part or article. Once all portions of the part or article are printed and the one or more coagulation agents are used to at least partially solidify each portion of the part or article, the green body structure is formed, the green body structure being substantially durable against deformation due to normal handling or moving of the green body structure, gravitational forces, loss due to evaporation or vaporization of solvents or other materials within the green body structure, and/or the like. In some embodiments, the green body structure may be only partially solidified, in which case further coagulation agents can be delivered to the green body structure or the green body structure can be submerged or partially submerged in a coagulation bath or the like in order to fully or substantially fully solidify the green body structure. IN some embodiments, the green body structure can have dimensions and a form factor that is similar to, an engineered relationship with, is substantially equal to, or is equal to the dimensions and form factor of the desired finished part or article, according to the digital design. In some embodiments, the green body structure may be engineered to be larger than or have a form factor that is intentionally different from the finished part or article in order to take into account an estimated, predicted, or known reduction in one or more dimensions and/or a change in part or all of the form factor of the green body structure relative to the finished metal structure, article, or part, due to the removal of binder materials and/or the like during sintering.
[0045]In some embodiments, since the build material is prepared as a suspension, various metal powders can be easily mixed at different ratios in situ and controllably deposited for parts with a functional gradient as designed. In some embodiments, the non-solvent may extract some or all of the solvent away from the green body structure due to a higher Hansen chemical solubility or affinity with the solvent and can then partially or fully solidifies the green body structure based on a phase inversion mechanism of the one or more polymeric materials. In some embodiments, the printed part can be further processed as needed in a coagulation bath for complete solidification as a green part. In some embodiments, at this stage, the partially or fully solidified one or more polymeric materials may act as a binding agent for the one or more metal powders (also referred to herein as “metal particles”). In some embodiments, the consumed solvent can be reclaimed for recycling and reuse. In some embodiments, the printed green part can be heated up to the sintering temperature of the one or more metallic powders to remove the sacrificial binder (e.g., one or more polymeric materials) and sinter the metallic powders to make the final metal part, structure, or article.
[0046]Described hereinbelow are examples in which different single metal powders, such as iron, copper, nickel, silver, and the like, were printed to form a 3D article by mixing each of them with a solution prepared from a sacrificial polymer (e.g., acrylonitrile-butadiene-styrene (ABS)) and a solvent (e.g., dimethyl sulfoxide (DMSO)) as example components of an example build material. In some embodiments, metal-ABS-DMSO build material was extruded in air to fabricate continuous conduits, shells and bulky parts for demonstration purposes. During printing, water was used as an example non-solvent for the metal-ABS-DMSO build material and was delivered to filaments being deposited using a nebulizer in an enclosed chamber where the extracted solvent was reclaimed. After printing, the semi-solidified part was submerged in a water-based coagulation bath for complete solidification and the residual solvent was reclaimed from the bath through a distillation process. The printed parts were then sintered under proper heating cycles according to the different example metal powders used. According to various examples, metal parts were 3D printed by using a dissolved sacrificial polymer binder and metal powder suspension as a printing platform while a non-solvent agent was simultaneously or nearly simultaneously delivered to form a green body structure (also described herein as “green part,”“green article,” or “green structure), allowing an in-air metal printing process that is quicker, safer for users, more energy efficient, requires less post processing, and results in mechanically superior printed metal parts, structures, and articles. In some embodiments, the green part was subjected to a sintering cycle to burn away the binding agent and sinter the metal particles, fusing them together and obtaining a fully metallic part. In some embodiments, part shrinkage and porosity during sintering were pre-compensated during the part design phase. In some embodiments, more than a single binder polymer may be used to minimize the possible porosity by removing them sequentially (e.g., at different times during the temperature ramping period due to the different binder polymers having different vaporization temperatures) during the post-processing phase.
[0047]Referring now to FIG. 1, a 3D printing process 10 for fabricating metal parts is provided which includes three or more steps, including for example: powder ink preparation, freeform printing, and post-printing sintering. While the one or more polymers are illustrated and/or described generally as being the binder/sacrificial materials in FIG. 1, other soluble binder materials can be used as sacrificial materials too, e.g., waxes, lower melting point metals, etc. According to some embodiments, the 3D printing process 10 comprises preparation of a first ink 11 by combining one or more first polymers 12a, one or more first solvents 12b, and one or more first metal powders 12c. The 3D printing process 10 can further comprise, optionally, preparation of a second ink 13 by combining one or more second polymers 14a, one or more second solvents 14b, and one or more first second powders 14c. In some embodiments, the mentioned mixture description serves the purpose of illustration of the multi-material capabilities of the proposed process, and it does not intend to limit the mixing method uniquely to two inks, as the described approach can be used to mix simultaneously more than two ink compositions.
[0048]In some embodiments, forming the ink or build material can involve mixing metal powders (e.g., 12c or 14c) with a respective polymer solution, which is prepared by dissolving one or more polymeric materials in one or more suitable solvents ((12a in 12b, or 14a in 14b, respectively) in order to obtain a homogeneous powder ink suspension for printing. In some embodiments, first one build material (e.g., A) and then the other build material (e.g., B) can be printed to form different portions of the printed article. In other embodiments, the 3D printing process 10 can further comprise, optionally, mixing 15 two or more build materials (inks) together to form a multi-metal printing material 16. In some embodiments, two or more different build materials (e.g., A and B) can be prepared and then combined according to any suitable ratio in order to achieve a specific composition to print a particular portion of the green body structure such that the corresponding portion of the finished metal article, part, piece, or structure likewise ha a corresponding ratio of a first and second (or more) metal particles. In such a manner, a particular portion, portions, or all of the finished article can comprise a binary, ternary, quaternary, quintenary, or other such metal composition. In some embodiments, a desired powder ink suspension containing different metal powders (e.g., A and B) can be prepared by mixing them at a given ratio by changing the mixing inputs from each starting ink.
[0049]In some embodiments, the 3D printing process 10 can further comprise printing and solidifying 17a the build material (e.g., A or B), or the multi-metal build material 16. In some embodiments, an applicable dispensing mechanism, such as material extrusion or material jetting, can be used to dispense the ink(s) or building material(s) into a printing space according to a layer-by-layer deposition approach or any other suitable approach, e.g., having an article building block of a material filament, a material droplet, or the like. In some embodiments, printing and solidifying 17a can be carried in an enclosed chamber to collect any released solvent and to minimize user exposure to the materials or process and to reduce contamination or detrimental external or environmental impacts on printing quality. In some embodiments, during printing and solidifying 17a, a polymer non-solvent agent 17b can be delivered to the location, space, position, environment, or sub-volume of the enclosed chamber where the metal-polymer composite part is being printed. In some embodiments, the polymer non-solvent agent 17b may solidify or partially solidify some or all of the polymer(s) in the build material (e.g., A, B, or 16) to retain deposited features and thereby entrapping the metal powders distributed in the deposited building block.
[0050]In some embodiments, the printing and solidification process 17a may be known as phase inversion in instances in which solidification is based on or includes the phase separation of a homogeneous polymer solution in a non-solvent medium in which the polymer does not dissolve and with which the solvent in the solution is fully miscible. In some embodiments, as the polymer non-solvent and polymer solvent present higher Hansen solubility than the Hansen solubility exhibited between the polymer and the solvent, the non-solvent, if properly chosen according to the particular polymer(s) and solvent(s) chosen, may have sufficient affinity to replace the solvent within the polymer solution. As such, in some embodiments, the rate at which phase inversion occurs may highly depend on the degree of solubility of the solvent in the non-solvent and the insolubility of the polymer in the non-solvent. In some embodiments, a similar principle may hold for systems in which more than one polymer, more than one solvent, and/or more than one non-solvent (also described herein as a “coagulation agent”) are used. In some embodiments, the phase inversion process may be induced, at least in part, by depositing the ink in a non-solvent-rich environment or disposing/deploying non-solvent or coagulation agent material nearby the printed or deposited ink.
[0051]In some embodiments, the phase inversion process may begin at or near an outer surface of deposited filaments/droplets when in contact with the active non-solvent agent in the printing environment. In some embodiments, once the surface is partially or fully solidified, a coagulation front may travel inwards within each filament/droplet of printed build material/ink, e.g., through diffusion of the non-solvent through each filament/droplet, and may extract some or all of the solvent from respective filaments/droplets of the printed structure. In some embodiments, this simultaneous or nearly simultaneous solidification of build material concurrent with printing of the build material may be controlled in such a way that solidification occurs only partially, e.g., in order to achieve a balance between achieving sufficient fusion between adjacently deposited layers, filaments, or droplets, due to the build material not being fully deposited, and achieving sufficient stiffness to support subsequently printed layers in air due to the existence of previously solidified or partially solidified build material (e.g., the one or more polymeric materials in the build material of a first layer may be coagulated or solidified enough such that a second layer of build material can be deposited on or supported on or stabilized by the first layer of build material). In some embodiments, through such phase inversion and other coagulation/solidification approaches, the 3D printing process 10 can further comprise formation of a green part 18 (also referred to herein as “green body structure”).
[0052]In an instance in which the green part 18 is only partially coagulated or solidified through exposure to the one or more coagulation agents/non-solvents, further coagulation or solidification may be necessary before the green part 18 is ready for post-printing processing. In some embodiments, in order to achieve complete or nearly complete solidification throughout a printed part, the green part 18 can be immersed, if needed, in a coagulation bath to fully remove the solvent. In some embodiments, the collected solvent-relevant solution from the printing chamber and coagulation bath are post-processed in order to reclaim the solvent for its reuse, minimizing its environmental impact. In some embodiments, variable metal powder suspensions can be mixed, prior to printing, to achieve a desired composition, and can be controllably deposited as a composition gradient structure during the printing and solidification process 17a. Said otherwise, in some embodiments, the ratio of a first and second build material (or a first, second, and third build material, etc.) can be changed dynamically during the printing and solidification process 17a such that a composition of the green part 18 achieves a compositional gradient between two locations, portions, regions, or sub-parts of the green part 18.
[0053]In some embodiments, the 3D printing process 10 can further comprise sintering 19a the green part 18 according to a suitably high temperature sintering cycle chosen from among a plurality of suitable sintering cycles according to the metal powder(s) used in the green part 18, to achieve the finished 3D printed metal part 19b. In some embodiments, the sintering cycle can comprise a binder/polymer removal process at lower temperatures than the sintering level. In some embodiments, the binder/polymer removal process (also referred to herein as “binder burnout process”) can be carried out to melt, decompose, vaporize, and/or evaporate the binder(s)/polymer(s) from the green part 18. In some embodiments, the binder burnout process must be carefully designed and controlled in order to avoid disruption of the macro structures of the printed part and/or the intra-/inter-metal particle fusing, ordering, structure, crystallization, etc. In some embodiments, the sintering 19a can occur at sufficiently high temperatures that are below the melting point of the metal powder or metal powders.
[0054]Without wishing to be bound by any particular theory, at such temperatures, the metal particles may start to fuse with each other due to atomic diffusion, as the atoms can move easily and migrate quicker along the particle-particle interfaces and inter-particle contact surfaces. Without wishing to be bound by any particular theory, at least some of the mechanisms that may contribute to sintering of a consolidated mass of crystalline particles are surface and grain boundary diffusion, which may be heavily dependent on the particle size and the material properties, and vapor transport and plastic flow, which entails the capability of the metal to permeate the gases obtained from the sintering process and which may impact the resulting porosity of the sintered metal part. In some embodiments, residual porosity may be found in powder metallurgy fabricated parts on the order of between about 1% and about 5%, however any suitable porosity can be achieved and is therefore contemplated as part of this disclosure. In some embodiments, the specifications of the thermal sintering cycle may depend on the binding polymers and metal powder(s) used, as well as the dimensions and/or form factor of the printed structure. In some embodiments, after sintering and taking into account the porous nature of the resulting part, the porous printed part can be, if needed, further infiltrated with suitable materials to ensure the pores are further filled, partially filled, nearly fully filled, or fully filled. In addition to the porosity, 3D printed metal parts may experience shrinkage during sintering. As such, the design, dimensions, and form factor for the green part 18 can be pre-compensated during the part design phase such that the sintered metal part adheres to the desired form factor and dimensions after the accounted-for sintering-induced shrinkage. In particular, in some embodiments, different binder polymers may be used to minimize the possible porosity by removing them sequentially during the post-processing phase.
[0055]In some embodiments, a system can be provided for carrying out the 3D printing process 10. In some embodiments, such a system may comprise an enclosed printing space, one or more printing nozzles, one or more coagulation agent delivery elements, one or more reservoirs configured to store a supply of one or more build materials, and a computing entity configured to: load and interpret a digital design of the green part 18, control movement of the printing nozzles, deliver build material via the printing nozzles, move the one or more coagulation agent delivery elements, deliver coagulation agent via the one or more coagulation agent delivery elements, and the like. In some embodiments, the system can further comprise a coagulation bath into which the green part 18 can be at least partially submerged in an instance in which the build material only partially or insufficiently solidifies during the interaction between the solvent and coagulation agent. In some embodiments, the system can further comprise a sintering oven operable to control a temperature, change in temperature, pressure, humidity, and/or other characteristics and parameters of an inner volume of the sintering oven. In some embodiments, the green part 18 can be loaded into the sintering oven and sintered to achieve the finished, printed metal article. In some embodiments, the enclosed printing space may function as the sintering oven such that the green part 18 can be printed in air and supported on a substrate within the enclosed printing space in the presence of coagulant, and then the green part 18 can be sintered without removing the green part 18 from the inner volume of the enclosed printing space.
[0056]In some embodiments, part of the 3D printing process 10 can, optionally, comprise the formation of a design for the green part 18 that accounts for any shrinkage during sintering. In some embodiments, the 3D printing process 10 can, optionally, comprise a computer-implemented or computer-controlled printing process whereby a computing entity or the like can interpret a digital design of the green part 18, map out one or more predetermined nozzle pathways within the enclosed printing space, move or cause movement of one or more nozzles according to the one or more predetermined nozzle pathways and a deposition rate of each nozzle to adequately deposit the build material at a suitable rate with respect to each location and rate of movement of each nozzle in order to deposit the correct type and quantity of build material at each location within the printing space that corresponds with a respective portion of the green part 18. In some embodiments, the 3D printing process 10 can, optionally, comprise a computer-implemented or computer-controlled printing process whereby a computing entity or the like can determine, for each nozzle of the one or more nozzles, a ratio of different build materials when a design for the green part 18 necessitates a build material that is achieved or achievable by combining two or more prepared build materials. In some embodiments, the 3D printing process 10 can, optionally, comprise a computer-implemented or computer-controlled printing process whereby a computing entity or the like can determine, based upon the one or more predetermined nozzle pathways, one or more predetermined nebulizer pathways for delivering one or more coagulation agents to the printed build material simultaneously or nearly simultaneously with the printing of the respective portions of the green part 18. In some embodiments, the 3D printing process 10 can, optionally, comprise a computer-implemented or computer-controlled printing process whereby a computing entity or the like can control a temperature and a temperature ramp rate for a vaporization/burnout process and/or the sintering 19a. As such, an aspect of this disclosure deals with the use of computing entities, either as part of an apparatus or system or external to the apparatus or system, to carry out these and other aspects of the 3D printing process 10, other tasks and processes described herein, the methods described and claimed, and the like.
[0057]Computer Program Products, Methods, and Computing Entities
[0058]Embodiments of the present invention may be implemented in various ways, including as computer program products that comprise articles of manufacture. Such computer program products may include one or more software components includin