3D ceramic printing

Abstract

An example of the present disclosure relates to a method for manufacturing a ceramic article, the method comprising: forming a ceramic structure by 3D printing the ceramic structure with a binder jet 3D ceramic printer using a ceramic powder and an inorganic binder, where the ceramic powder comprises a sintered ceramic material; and firing the ceramic structure to form the ceramic article.

Description

[Technical field]

[0001] An example of the present disclosure relates to 3D ceramic printing. One example relates to a method for producing ceramic articles obtained from binder jet 3D printing of ceramic structures without prejudice to the above-mentioned scope. One particular example relates to a method for producing a ceramic casting filter for filtration of molten metal without prejudice to the above-mentioned scope, and a ceramic casting filter for filtration of metal produced by such a method. [Background technology]

[0002] 3D printing, also known as additive manufacturing, is a well-known technique for manufacturing articles. 3D printing encompasses a variety of different techniques and processes that use different printing media / materials to synthesize three-dimensional articles. Typically, in 3D printing, successive layers of material are formed under computer control, e.g., based on a virtual 3D model or CAD design, which allows for the formation of articles of almost any shape or geometry.

[0003] Typically, to form a ceramic article by 3D printing, an initial ceramic structure / model is 3D printed by a 3D ceramic printer, such initial ceramic structure serving as a precursor of the resulting ceramic article, which is formed upon sintering of said ceramic structure.

[0004] One form of 3D ceramic printer technology is binder jet additive manufacturing / binder jet 3D printing (also referred to as "powder bed and inkjet", "drop-on powder" printing), which uses a binder that is selectively deposited in specific parts of a layer of powder, for example using an inkjet printer head, to assist in the construction of the part in an additive layer-by-layer process.

[0005] In a typical binder jet process, a thin layer of powder from a powder supply is spread on top of a build platform. One or more inkjet nozzles selectively deposit / jet droplets of a binder that bonds the powder particles together in a pattern that forms the layer of the 3D printed part. Wherever the binder is placed on the ceramic powder layer, the ceramic powder bonds and solidifies. Once the layer is complete, the build platform moves down and the powder supply moves up (e.g., via a build piston that lowers the build platform and a powder feed piston that raises the powder supply), and another thin layer of powder is spread on the build platform (e.g., via a leveling roller). This process is repeated, building portions until the entire part is complete. After the 3D printing process, the build part encapsulated in the powder bed is removed from the powder bed and any loose unbonded excess powder is removed / cleaned to fully expose the completed ceramic structure. The 3D printed part, i.e., the initial ceramic structure in the "green state," must then be fired to sinter, e.g., melt / vitrify / solidify the 3D printed ceramic structure to form the resulting ceramic article, whereby the 3D printed initial ceramic structure in effect forms a ceramic precursor structure, which, once fired / sintered, forms the ceramic article. Summary of the Invention [Problem to be solved by the invention]

[0006] Ceramic powders for binder jet 3D ceramic printers, i.e., ceramic powder feedstock / ceramic printing material / media, are typically produced by a spray drying process. In this method, dry powders are formed from ceramic slurries by rapidly drying the ceramic slurry with hot gases to form dry free-flowing powders with particle sizes of 50-100 microns suitable for use in binder jet 3D ceramic printers. However, binder jet 3D ceramic printers using such conventional ceramic printing materials to form ceramic structures may experience significant shrinkage, e.g., on the order of 40%, when fired / sintered to form the resulting ceramic article. This may cause asymmetric deformation of the resulting ceramic article, and structural defects such as cracks. Thus, the resulting ceramic article, i.e., the ceramic article obtained from the fired / sintered 3D printed ceramic structure, may have a low net shape and low fidelity to the initial shape / dimensions of the 3D printed ceramic structure before firing. When the resulting ceramic article is a ceramic casting filter, e.g., in the case of a direct injection casting process, shrinkage affects the porosity of the filter, reducing the filter's pores per inch (PPI), decreasing the filtration efficiency and flow rate of the filter, which increases the injection time during the casting process and increases the risk of molten metal freezing during the casting process, e.g., in the filter or crucible during the casting process.

[0007] Conventional 3D ceramic printing techniques are not always optimal. In some situations, it may be desirable to provide an improved binder jet 3D ceramic printing technique that reduces shrinkage during firing of a 3D printed ceramic structure to form a resulting 3D printed ceramic article. In some situations, it may be desirable to reduce asymmetric deformation and structural defects in the resulting ceramic article, i.e., resulting from the fired 3D printed structure, and improve fidelity to the initial shape / dimension of the pre-fired 3D printed structure.

[0008] The listing or discussion of a prior document or background in this specification should not necessarily be construed as an admission that the document or background is part of the prior art or is common general knowledge. One or more aspects / embodiments of the present disclosure may or may not address one or more background problems. [Means for solving the problem]

[0009] The invention is defined in the independent claims.

[0010] In at least some embodiments of the present disclosure, 1. A method of making a ceramic article, comprising: forming a ceramic structure by 3D printing the ceramic structure with a binder jet 3D ceramic printer using a ceramic powder and an inorganic binder, the ceramic powder comprising a sintered ceramic material; firing the ceramic structure to form the ceramic article; A method is provided comprising:

[0011] In at least some embodiments of the present disclosure, there is provided a ceramic article made by the aforementioned method.

[0012] In accordance with at least some embodiments of the present disclosure, there is provided a ceramic cast filter for metal filtration manufactured according to the aforementioned method.

[0013] In at least some embodiments of the present disclosure, embodiments are provided that are set forth in the accompanying claims.

[0014] For a better understanding of various examples of the present disclosure which are helpful in understanding the detailed description and specific embodiments of the present invention, reference will now be made to the accompanying drawings, which are merely examples and in which: [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram illustrating the method of the present disclosure. [Diagram 2] FIG. 2 is a schematic diagram illustrating another method of the present disclosure. [Diagram 3] FIG. 1 is a schematic diagram outlining the process of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The drawings (and with particular reference to FIGS. 1-3 ) generally illustrate a method 100 for making a ceramic article 304. The method includes: In 101, a ceramic structure 303 is formed by 3D printing with a binder jet 3D ceramic printer (not shown) using a ceramic powder 302 and an inorganic binder, where the ceramic powder comprises a sintered ceramic material 301; At 102 , the ceramic structure is fired to form the ceramic article 304 .

[0017] In the examples of the present disclosure, the ceramic powder for binder jet 3D ceramic printers (such ceramic powders are ceramic feedstocks or ceramic print media / materials for binder jet 3D ceramic printers) has ceramic material that has already been sintered, i.e., it is "pre-sintered" and has already been sintered to form individual particles of ceramic material that have already been sintered / fused / vitrified. This reduces the porosity of the individual particles of sintered ceramic material that make up the ceramic powder and increases the density of the ceramic powder. Such pre-sintered particles of ceramic material that form the ceramic powder for binder jet 3D printing are in contrast to conventional ceramic powders for binder jet 3D printing that are unsintered (e.g., "green" / "green state" and / or unfired ceramic materials) that have a relatively high porosity.

[0018] In the embodiments of the present disclosure, when the 3D printed ceramic structure is itself fired, thereby sintering / melting / vitrifying itself to form the resulting ceramic article, the use of pre-sintered ceramic materials in the ceramic powder (i.e., ceramic materials that have already been sintered) significantly reduces the shrinkage of the 3D printed ceramic structure in the formation of the resulting ceramic article after firing, compared to when conventional unsintered ceramic powders are used. For example, by using pre-sintered ceramic materials in the ceramic powder, the shrinkage of the 3D printed article after firing (i.e., the 3D printed product in the green body / state) can be on the order of less than 10% or 5% (compared to the 40% shrinkage of conventional ceramic powders for binder jet 3D ceramic printing). This can reduce asymmetric deformation and structural defects in the resulting ceramic article, and improve the fidelity of the resulting ceramic article to the initial shape / dimension of the 3D printed structure before firing.

[0019] Some examples of ceramic articles produced by the methods of the present disclosure include ceramic filters, such as, for example, ceramic cast filters for filtering molten metal, which in particular require ceramic articles with high heat resistance (e.g., the ability to withstand temperatures in excess of 1,650° C.) and high structural strength / integrity. However, it will be understood that the methods of the present disclosure are not limited to the production of ceramic cast filters, and any suitable ceramic article may be produced.

[0020] FIG. 1 illustrates generally a method 100 for making a ceramic article (eg, ceramic article 304 of FIG. 3).

[0021] In block 101, a ceramic structure is first formed by 3D printing the ceramic structure using a binder jet 3D ceramic printer. The binder jet 3D ceramic printer uses a ceramic powder and an inorganic binder. Further, the ceramic powder includes a sintered ceramic material.

[0022] In various examples, the binder jet 3D ceramic printer jetting material is an inorganic binder (i.e., no organic binding agent is included). The inorganic binder may include, for example, at least one of a ceramic binder, a silicate, a phosphate, an aluminate, an aluminum phosphate, a phosphoric acid, and an alumina gel.

[0023] Thereby, the 3D ceramic printer prints an initial ceramic structure / model, which in effect forms a ceramic precursor to the resulting ceramic article once it has undergone a firing process. In this application, "precursor" may be used to describe a material from which another material is formed.

[0024] In block 102, the 3D printed ceramic structure is fired to form the ceramic article.

[0025] In some examples, firing the ceramic structure includes firing the ceramic structure to a temperature greater than 1,000°C, 1,200°C, 1,400°C, or 1,600°C. The firing temperature is selected to be appropriate for the ceramic material and its refractory materials used, including at least one or more of silicon carbide, silica, clay, alumina (aluminum dioxide Al2O3), zirconia (zirconium dioxide ZrO2), magnesium oxide (MGO), calcium oxide (CaO), mullite, yttria / yttria oxide (Y2O3), and fused zirconia mullite.

[0026] In the examples of the present disclosure, ceramic powders for binder jet 3D ceramic printers (i.e., ceramic print media / materials used in combination with jetted binders to form ceramic structures in 3D printers) include pre-fired ceramic materials to form grains / grains including pre-sintered / fused / vitrified ceramic materials, i.e., particles of ceramic material are sintered / fused / vitrified together to form grains / grains of sintered ceramic material. Such pre-sintered ceramic materials have lower porosity and higher density than unsintered ceramic materials. The use of such pre-sintered ceramic materials in ceramic powders for binder jet 3D printers allows the 3D printed ceramic structures to reduce the amount of shrinkage during firing to form the resulting ceramic article.

[0027] In the examples of the present disclosure, the ceramic powder (i.e., ceramic print medium / material) is a ceramic powder whose grains / grains are formed from smaller particles that are sintered together to form a sintered granular ceramic material, or a sintered agglomerate of particles of the ceramic material. For example, ceramic material having grains initially (prior to granulation and sintering) on ​​the order of 2-50 microns in size is combined with one another and sintered to form sintered grains / grains having larger particle sizes, for example on the order of 50-150 microns.

[0028] The ceramic powder may have a substantially sintered granular ceramic material, i.e., the sintered granular ceramic material may have a substantial proportion, e.g., weight ratio and / or volume ratio, of ceramic powder. For example, the sintered ceramic material may comprise 90-100% by weight of ceramic powder. Other materials / additives that may be present in the ceramic powder (i.e., other materials / additives that form less than 10% by weight of the ceramic print medium / material of the binder jet 3D printer material) include microsilica / silica fume (which may be used to enhance the absorption of the ceramic powder of the jetted binder), and clay (which may be used to enhance the green strength of the 3D printed structure).

[0029] In some examples, the sintered particulate ceramic material has grains / grains of sintered granular particles, agglomerated particles, or agglomerated particles of the ceramic material. For example, referring to Figure 3, individual separate particles of ceramic material 301 are granulated / agglomerated / agglomerated and sintered to each other (such granulation / agglomeration / agglomeration and sintering is represented diagrammatically by arrows 200) to form grains / granules / particles of sintered particles / agglomerated / agglomerated particles of the ceramic material that form the ceramic powder for a binder jet 3D ceramic printer.

[0030] In some examples, the sintered ceramic material has a porosity of less than 10% or less than 5%, i.e., the porosity of the individual particles is less than 10% or less than 5%. Significantly, such low porosity levels of the ceramic powders reduce the amount of shrinkage when the 3D printed ceramic structure is fired / sintered to form the ceramic article in step 102. In some examples, the ceramic powders are configured such that the printed ceramic structure 3D experiences less than 10% or 5% shrinkage upon firing to form the ceramic article.

[0031] In some examples, the ceramic powder is configured to be a substantially free-flowing powder of the sintered ceramic material, i.e., the grains of the ceramic powder are configured to be substantially non-agglomerated and not stuck to each other. Such free-flowing characteristics of the ceramic powder may be advantageous due to the morphology of the grains / granules / particles of the sintered ceramic material, particularly with respect to their particle size (e.g., less than 150 microns), shape (e.g., substantially spherical), and surface characteristics (e.g., configured to be smooth to reduce frictional forces).

[0032] In some examples, the sintered ceramic material includes particles of sintered ceramic material having a size less than 200 microns, less than 150 microns, less than 100 microns, or less than 50 microns.

[0033] In some examples, the sintered ceramic material comprises particles of sintered ceramic material having a size greater than 10 microns, greater than 30 microns, greater than 50 microns, or greater than 70 microns.

[0034] An advantage of the disclosed 3D printing process and the specific examples of ceramic powders used thereby is that the firing process 201 can be carried out in the presence of oxygen, rather than alternative 3D printing processes that include carbonizing the 3D printed ceramic structure (i.e., impregnating or coating the 3D printed ceramic structure with a carbon precursor such as an organic material / carbon-containing compound, and pyrolyzing the 3D printed ceramic structure (i.e., firing the 3D printed ceramic structure in the absence of air / oxygen), whereby the organic material in / around the 3D printed ceramic structure is carbonized, thereby forming a network of carbon bonds in / around the resulting ceramic article). Thus, a simpler and less expensive manufacturing process can be employed, which can be carried out in open air, and deoxygenation is not required. This also allows for a continuous firing process to be utilized instead of a batch process that requires firing in a deoxygenated environment. Additionally, in alternative 3D printing processes that include carbonizing the 3D printed ceramic structure, the resulting pyrolyzed carbonized 3D printed ceramic article oxidizes at temperatures of about 600°C. Significantly, the exemplary 3D printing process of the present disclosure results in a ceramic article that does not oxidize at 600° C. This is significant when the resulting ceramic article is a ceramic cast filter for metal filtration, as the filter can be preheated (which can inhibit metal freezing upon initial impact with the filter during the metal filtration process).

[0035] FIG. 2 illustrates generally an example method 200 for producing ceramic powder (e.g., ceramic printing material 302 in FIG. 3) for a 3D ceramic printer.

[0036] In block 201, a first plurality of particles of a ceramic material 301 (e.g., powder: alumina, silica and / or zirconia) is granulated to form a second plurality of grains, each grain being formed of a plurality of particles 301.

[0037] In block 202, the second plurality of grains of ceramic material are sintered to form a second plurality of sintered grains of ceramic material 302. This results in a ceramic powder comprising (larger) particles (e.g., on the order of 100 microns) of (smaller) particles (e.g., on the order of 2-50 microns) of ceramic material sintered together, which are inorganically bonded to each other. In embodiments of the present disclosure, such sintered grains of ceramic material 302 are used as ceramic powder in a binder jet 3D ceramic printer. In some examples, such sintered particles of ceramic material 302 may correspond to ceramic beads or artificial sand.

[0038] FIG. 3 shows a schematic diagram of the process of the present disclosure and the methods described above.

[0039] 3 shows diagrammatically that a plurality of particles of ceramic material (301) are granulated, aggregated and / or agglomerated and then sintered to form grains, each of which has a plurality of sintered particles (302). In effect, (larger) grains / granules / particles are formed from the granulation / aggregation / agglomeration of (smaller) particles of ceramic material, which are sintered together to form the larger grains / granules / particles. The granulation / aggregation / agglomeration and sintering process is represented by arrows 200 and corresponds to the process in FIG. 2. Such pre-sintered particles are used as ceramic powder for binder jet 3D printing.

[0040] In some examples, initially, the unsintered particles of the ceramic material (301) have a particle size on the order of 2-50 microns. These are granulated / aggregated / agglomerated, for example, with water and an organic binder, to form larger granulated / aggregated / agglomerated grains having a particle size on the order of 50-150 microns. These grains are then sintered to form sintered granulated / aggregated / agglomerated particles of the ceramic material. Following the sintering process, any grains larger than a threshold size (e.g., 150 microns) and smaller than a threshold size (e.g., 50 microns) are sieved / filtered to leave behind grains having a particle size range (e.g., 50-150 microns). Such particle sizes are optimal / preferred for providing a free-flowing powder and therefore optimal / preferred for use as ceramic powder 302 for binder jet 3D ceramic printers. The granulation / aggregation / agglomeration process may be configured to form substantially spherical grains, which is optimal / suitable for providing a free-flowing powder and therefore for use as a ceramic powder in a binder jet 3D ceramic printer.

[0041] The ceramic powder 302 is then used in a binder jet 3D ceramic printer to 3D print a ceramic structure 303 formed with the ceramic powder 302 and the jet binder. Such a printing process is represented by arrow 101 and corresponds to process 101 in FIG.

[0042] Ceramic structure 303 is then fired to form ceramic article 307. Such a firing process is represented by arrow 102 in FIG.

[0043] The aforementioned methods and processes may be used to manufacture ceramic articles, particularly ceramic filters, such as ceramic porous cast filters for metal filtration, where an initial ceramic porous structure (similar to the structure and shape of a ceramic cast foam filter) is printed by a 3D ceramic printer and then fired to form the resulting ceramic cast filter. However, it is understood that the disclosed methods are not limited to the manufacture of ceramic cast filters, and any suitable ceramic article may be manufactured, such as ceramic nozzles (e.g., for metal metering), ceramic flow control devices, technical ceramics / ceramics for engineering, medical ceramics (e.g., for implants), electrical ceramics, and insulators.

[0044] Examples of the present disclosure are described using flow charts and schematic block diagrams. It is understood that each block and combination of blocks (of the flow charts and block diagrams) can be implemented by any means, device, or machine suitable for implementing the functions specified in one or more blocks. Thus, the blocks support combinations of means, devices, or machines that implement the specified functions, and combinations of operations that implement the specified functions.

[0045] Although features are described with reference to certain embodiments, these features may also be present in other embodiments, whether or not described. In the preceding paragraphs, various embodiments of the present disclosure have been described, but it should be understood that modifications may be made to a given embodiment without departing from the scope of the invention as set forth in the claims. For example, the various embodiments (and process methods) may be combined.

[0046] The term "comprising" as used in this application is used in an inclusive sense, not an exclusive sense, i.e., any reference to X having Y means that X may include only one Y, or may include two or more Y. If the exclusive sense of "comprising" is intended, this will be clarified in the context by saying "comprising only" or by using "consisting of."

[0047] In this application, reference is made to various embodiments. A description of a feature or function with respect to an embodiment indicates that the feature or function is present in that embodiment. The use of the term "example" or "for example" or "may" in a sentence, whether or not explicitly stated, means that such feature or function is present in at least the described example, whether or not it is described as an example, and that it may, but need not, be present in some or all other examples. Thus, "example," "for example," or "may" refers to a particular event in a class of events. A property of an event may be a property of only that event, a property of the class, or a property of a subclass of the class that includes some but not all of the events in the class.

[0048] In this application, reference to "a / an / the" [feature, element, precipitation agent, means...] is understood as meaning "at least one" [feature, element, precipitation agent, means...], unless expressly specified otherwise.

[0049] Although the foregoing description attempts to draw attention to features of the examples of the present disclosure which are believed to be of particular importance, it should be understood that applicants claim protection for any patentable feature or combination of features previously mentioned and / or shown in the drawings in this application, whether or not specifically emphasized.

[0050] The examples of the present disclosure and the claims below may be combined in any suitable manner apparent to one of ordinary skill in the art.

Claims

1. 1. A method of making a ceramic article, comprising: forming a ceramic structure by 3D printing the ceramic structure with a binder jet 3D ceramic printer using a ceramic powder and an inorganic binder, the ceramic powder comprising a sintered ceramic material, the sintered ceramic material having particles of the sintered ceramic material having a size greater than 10 microns and less than 200 microns; firing the ceramic structure to form the ceramic article, the ceramic article comprising a ceramic cast filter for metal filtration; The method comprising:

2. The method of claim 1 , wherein the sintered ceramic material comprises a sintered particulate ceramic material.

3. The method of claim 1 or 2, wherein the sintered ceramic material has a porosity of less than 10% or less than 5%.

4. 4. The method of claim 1, wherein the ceramic structure undergoes shrinkage of less than 10% or less than 5% upon firing to form the ceramic article.

5. 5. The method of claim 1, wherein the ceramic powder comprises a free-flowing powder of a sintered ceramic material.

6. 6. The method of claim 1, wherein the sintered ceramic material comprises particles of sintered ceramic material having a size of less than 150 microns, less than 100 microns, or less than 50 microns.

7. 7. The method of claim 1, wherein the sintered ceramic material comprises particles of sintered ceramic material having a size greater than 30 microns, greater than 50 microns, or greater than 70 microns.

8. 8. The method of claim 1, wherein firing the ceramic structure comprises firing the ceramic structure to a temperature greater than 1,000°C, 1,200°C, 1,400°C, or 1,600°C.

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