A method of manufacturing a ceramic object using 3D ceramic printing

Abstract

Certain examples of the present disclosure relate to a method for manufacturing a ceramic object, the method comprising: forming a ceramic structure by 3D printing by using a binder jet 3D ceramic printer of a ceramic powder and an inorganic binder, wherein the ceramic powder comprises a sinterable ceramic material; and firing the ceramic structure to form the ceramic object.

Description

TECHNICAL FIELD

[0001] Examples of the present disclosure relate to 3D ceramic printing. Some examples, without prejudice to the foregoing, relate to a method of manufacturing a ceramic object obtained by binder jetting a 3D printed ceramic structure. Certain specific examples, without prejudice to the foregoing, relate to a method of manufacturing a ceramic foundry filter for molten metal filtration, and a ceramic foundry filter for metal filtration manufactured according to such a method. BACKGROUND

[0002] 3D printing, also known as additive manufacturing, is a well-known technique for manufacturing objects. 3D printing techniques encompass various different techniques and processes using different printing media / printing materials for synthesizing three-dimensional objects. 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 can facilitate creating objects of almost any shape or geometry.

[0003] Typically, to form a ceramic object by 3D printing, an initial ceramic structure / model is 3D printed by a 3D ceramic printer. This initial ceramic structure serves as a precursor for the resulting ceramic object, which is formed when the ceramic structure is sintered.

[0004] One form of 3D ceramic printer technology is binder jetting additive manufacturing / binder jetting 3D printing, which is also known as “powder bed and inkjet” and “drop-on- powder” printing, which uses a binder selectively applied to specific portions of a powder layer, e.g. using an inkjet printer head, to facilitate building a part in a layer-by-layer additive process.

[0005] In a typical binder jetting process, a thin layer of powder from a powder supply is spread on a build platform. One or more inkjet nozzles selectively deposit / jet droplets of a binder that bind together the powder particles to form a pattern that forms a layer of a part to be 3D printed. Wherever the binder is applied to the layer of ceramic powder, the ceramic powder binds and solidifies. When the layer is complete, the build platform is moved downward, the powder supply is moved upward (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). The process is repeated to build the part until the entire part is complete. After the 3D printing process, the built part encapsulated in the powder bed is removed from the powder bed, and the loose unbound excess powder is removed / cleaned to fully expose the completed ceramic structure. Then, the 3D printed part, i.e., the initial ceramic structure in a “green state,” needs to be fired to sinter, e.g., fuse / vitrify / solidify, the 3D printed ceramic structure, thereby forming the resulting ceramic object. The 3D printed initial ceramic structure thus effectively forms a ceramic precursor structure that, once fired / sintered, forms the resulting ceramic object.

[0006] Ceramic powders, i.e., ceramic powder feedstocks / ceramic printing materials / media, for binder jetting 3D ceramic printers are typically manufactured by a spray drying process. Here, a dried powder is formed from a ceramic slurry by rapidly drying the ceramic slurry with hot gas to produce a dry free-flowing powder having a particle size of 50-100 microns suitable for use in a binder jetting 3D ceramic printer. However, binder jetting 3D ceramic printers that use such conventional ceramic printing materials to form ceramic structures can suffer from significant shrinkage, e.g., on the order of about 40%, when fired / sintered to form the resulting ceramic object. This can result in asymmetric distortion of the resulting ceramic object and structural weaknesses such as cracks. Thus, the resulting ceramic object, i.e., the ceramic object derived from the 3D printed ceramic structure that is fired / sintered, can have a poor net shape and low fidelity to the initial shape / dimensions of the 3D printed ceramic structure prior to its firing. In the case where the resulting ceramic object is a ceramic casting filter, e.g., for a direct pour casting process, the shrinkage affects the porosity of the filter, reduces the pores per inch (PPI) of the filter, thereby reducing the filtration efficiency and flow rate of the filter, thereby lengthening the pour time during the casting process and risking solidification of the molten metal during the casting process, e.g., in the filter or in the crucible.

[0007] Conventional 3D ceramic printing techniques are not always optimal. In some cases, it can be desirable to provide improved binder jet 3D ceramic printing techniques that can reduce shrinkage when firing a 3D printed ceramic structure to form a resulting 3D printed ceramic object. In some cases, it can be desirable to reduce asymmetric distortion and structural weaknesses in the resulting ceramic object, i.e., asymmetric distortion and structural weaknesses resulting from the fired 3D printed structure, and improve fidelity of the resulting ceramic object to the initial shape / dimensions of the 3D printed structure prior to firing.

[0008] The listing or discussion of an apparently prior-published document or a document in the background art does not constitute an admission that the document or background art is part of the prior art of the present disclosure or that it is common general knowledge. One or more aspects / examples of the present disclosure can address or can not address one or more of the problems in the background art. SUMMARY

[0009] The present invention is described by way of example in relation to examples / embodiments provided herein.

[0010] According to at least some examples of the present disclosure, there is provided a method of manufacturing a ceramic object, the method comprising:

[0011] 3D printing a ceramic structure by using a binder jet 3D ceramic printer to form a ceramic structure, wherein the ceramic powder comprises a sinterable ceramic material; and

[0012] firing the ceramic structure to form a ceramic object.

[0013] According to at least some examples of the present disclosure, there is provided a ceramic object manufactured according to the method described above.

[0014] According to at least some examples of the present disclosure, there is provided a ceramic foundry filter for metal filtration manufactured according to the method described above.

[0015] Further examples / embodiments are also provided herein. BRIEF DESCRIPTION OF DRAWINGS

[0016] For a better understanding of the various examples of the present disclosure, reference will now be made, by way of example only, to the accompanying drawings in which:

[0017] Figure 1 A method of the present disclosure is schematically illustrated;

[0018] Figure 2 Another method of the present disclosure is schematically illustrated; and

[0019] Figure 3 An overview of the process of the present disclosure is schematically illustrated. DETAILED DESCRIPTION

[0020] The accompanying drawings (at least with respect to Figure 1 and Figure 3 ) schematically illustrate a method 100 of manufacturing a ceramic object 304, the method comprising:

[0021] a forming step 101 of forming a ceramic structure 303 by 3D printing the ceramic structure 303 using a ceramic powder 302 and an inorganic binder with a binder jet 3D ceramic printer (not shown), wherein the ceramic powder 302 comprises a sintered ceramic material 301; and

[0022] a firing step 102 of firing the ceramic structure to form the ceramic object 304.

[0023] In examples of the present disclosure, the ceramic powder for the binder jet 3D ceramic printer (such a ceramic powder is a ceramic feedstock or ceramic printing medium / material for the binder jet 3D ceramic printer) comprises a ceramic material that has already been sintered, i.e. it is “pre-sintered” in that it has already been pre-exposed to firing to form individual grains of sintered / fused / vitrified ceramic material. Advantageously, this reduces the porosity of the individual grains of sintered ceramic material that make up the ceramic powder, and increases the density of the ceramic powder. Such pre-sintered grains of ceramic material forming the ceramic powder for binder jet 3D printing will be compared and contrasted with conventional ceramic powders for binder jet 3D printing, which comprise unsintered, e.g. “green” / “green state” and / or unfired, ceramic material having a relatively higher porosity.

[0024] In examples of the present disclosure, the use of a pre-sintered ceramic material for the ceramic powder (i.e. a ceramic material that has been pre-sintered) advantageously results in less shrinkage of the 3D printed ceramic structure in the formation of the resulting ceramic object after firing, compared to the case of using a conventional non-sintered ceramic powder, when the 3D printed ceramic structure itself is exposed to firing and thereby itself becomes sintered / fused / vitrified to form the resulting ceramic object. For example, the use of a pre-sintered ceramic material for the ceramic powder can enable the 3D printed object (i.e. the green body / state 3D printed object) to shrink by an order of magnitude of less than 10% or 5% after its firing (compared to a 40% shrinkage for conventional ceramic powders for binder jet 3D ceramic printing). Advantageously, this can reduce asymmetric distortion and structural weaknesses in the resulting ceramic object, and improve the fidelity of the resulting ceramic object to the initial shape / dimensions of the 3D printed structure before its firing.

[0025] Certain examples of ceramic objects that can be manufactured according to the methods of the present disclosure include, but are not limited to, for example, ceramic filters, such as ceramic foundry filters for filtering molten metal, particularly where ceramic objects having high refractory qualities (e.g., the ability to withstand temperatures in excess of 1650°C) as well as high structural strength / integrity are required. However, it should be appreciated that the methods of the present invention are not limited to the manufacture of ceramic foundry filters, and can manufacture any suitable ceramic object.

[0026] Figure 1 A method 100 for manufacturing a ceramic object (e.g., a ceramic object 304) is schematically illustrated. Figure 3

[0027] In block 101, a ceramic structure is first formed by 3D printing a 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 sinterable ceramic material.

[0028] In various examples, the jetted material of the binder jet 3D ceramic printer is an inorganic binder (i.e., does not contain an organic binder). The inorganic binder can include, for example, at least one of: a ceramic binder, a silicate, a phosphate, an aluminate, an aluminum phosphate, phosphoric acid, and an alumina oxide gel.

[0029] The 3D ceramic printer thereby prints an initial ceramic structure / model that is essentially a ceramic precursor to the resulting ceramic object after the ceramic object undergoes a firing process. As used herein, "precursor" can be used to refer to a substance that forms another substance.

[0030] In block 102, the 3D printed ceramic structure is fired to form a ceramic object.

[0031] In some examples, the firing of the ceramic structure includes firing the ceramic structure to a temperature that is higher than: 1000°C, 1200°C, 1400°C, or 1600°C. The firing temperature can be selected so as to be suitable for the ceramic material used and the refractory material therein, such materials including, but not limited to at least one or more of: silicon carbide, silica, clay, alumina (aluminum dioxide Al203), zirconia (zirconium dioxide Zr02), magnesia (MGO), calcia (CaO), mullite, yttria / yttrium oxide (Y203), fused zirconia mullite.

[0032] ​In examples of the present disclosure, the ceramic powder (i.e., the ceramic printing medium / material used by the binder jet 3D printer, which is combined with the jetted binder to form the ceramic structure) for the binder jet 3D ceramic printer includes a ceramic material that has been subjected to firing to form granules, which include ceramic material that has been pre-sintered / fused / glassed, i.e., the particles of the ceramic material have been sintered / fused / glassed together to form the granules of the sintered ceramic material. Such pre-sintered ceramic material has reduced porosity and higher density compared to unsintered ceramic material. Using such pre-sintered ceramic material as the ceramic powder for the binder jet 3D printer results in the 3D printed ceramic structure undergoing a reduced amount of shrinkage upon firing when forming the resulting ceramic object.

[0033] In examples of the present disclosure, the ceramic powder (i.e., the ceramic printing medium / material) is a ceramic powder whose granules / particles are themselves formed from smaller particles that have been sintered together, thereby forming a sintered granulated ceramic material or a sintered agglomeration of particles of the ceramic material. For example, a ceramic material that initially (prior to granulation and sintering) has a particle size on the order of 2-50 microns can be combined together and sintered to form sintered granules / particles having a larger particle size, e.g., on the order of 50-150 microns.

[0034] The ceramic powder can include substantially sintered granulated ceramic material, i.e., the sintered granulated ceramic material can include a substantial proportion of the ceramic powder, e.g., by weight and / or volume. For example, the sintered ceramic material can include 90-100% of the ceramic powder by weight. Other materials / additives that can be present in the ceramic powder (i.e., other materials / additives that form less than 10% of the ceramic printing medium / material by weight for the binder jet 3D printer material) include: microsilica / Silica fume (which can be used to enhance the absorption of the jetted binder to the ceramic powder) and clay (which can be used to enhance the green strength of the 3D printed structure).

[0035] In some examples, the sintered granulated ceramic material includes granules / particles of sintered granulated, agglomerated, or aggregated particles of the ceramic material. For example, with respect to Figure 3 , the individual single particles of the ceramic material 301 can be granulated / agglomerated / aggregated and sintered together (such granulation / agglomeration / aggregation and sintering is schematically represented by arrow 200) to form the granules / particles of the sintered granulated / agglomerated / aggregated particles of the ceramic material, which forms the ceramic powder for the binder jet 3D ceramic printer.

[0036] In some examples, the sintered ceramic material comprises a porosity of less than 10% or 5%, i.e. the porosity of the individual grains is less than 10% or 5%. Advantageously, this low porosity level of the ceramic powder reduces the amount of shrinkage when the 3D printed ceramic structure is fired / sintered in step 102 to form the ceramic object. In some examples, the ceramic powder is configured (i.e. at least by virtue of its porosity) such that the ceramic structure 3D printed therefrom experiences a shrinkage of less than 10% or 5% when fired to form the ceramic object.

[0037] 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 not cohesive and bonded together. This free-flowing property of the ceramic powder can be influenced by the configuration of the grains / particles of the sintered ceramic material, especially for example in relation to their: particle size (e.g. less than 150 microns), shape (e.g. substantially spherical) and surface properties (e.g. smooth and configured so as to reduce friction).

[0038] In some examples, the sintered ceramic material comprises particles of the sintered ceramic material having a size of: less than 200 microns, less than 150 microns, less than 100 microns or less than 50 microns.

[0039] In some examples, the sintered ceramic material comprises particles of the sintered ceramic material having a size of: greater than 10 microns, greater than 30 microns, greater than 50 microns or greater than 70 microns.

[0040] Certain examples of the 3D printing process of the present disclosure, and the ceramic powder used thereby, are advantageous over alternative 3D printing processes that involve carbonizing a 3D printed ceramic structure (i.e., impregnating or coating a 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] such that the organic material within / around the 3D printed ceramic structure is carbonized, thereby forming a network of carbon bonds within / around the resulting ceramic object), the firing process 201 can be performed in the presence of oxygen. Thus, a simpler and less expensive manufacturing process can be employed, which can be performed in an open atmospheric environment and does not require deoxygenation. This can also enable the use of a continuous firing process, rather than an intermittent process as required in a deoxygenated environment. Furthermore, for alternative 3D printing processes that involve carbonizing a 3D printed ceramic structure, the resulting pyrolyzed carbonized 3D printed ceramic object will oxidize at temperatures of about 600°C. Advantageously, examples of the 3D printing method of the present disclosure produce ceramic objects that do not oxidize at 600°C. This can be advantageous in the case where the resulting ceramic object is a ceramic cast filter for metal filtration, as this enables the filter to be pre-heated (thereby reducing metal solidification upon initial impact with the filter during a metal filtration process).

[0041] Figure 2 An example of a method 200 for manufacturing a ceramic powder (e.g., such as a ceramic printing material 302 for a 3D ceramic printer) is schematically illustrated. Figure 3 An example of a method 200 for manufacturing a ceramic powder (e.g., such as a ceramic printing material 302 for a 3D ceramic printer) is schematically illustrated.

[0042] In block 201, a plurality of first particles of a ceramic material 301 (e.g., but not limited to powdered: alumina, silica, and / or zirconia) are granulated to form a plurality of second granules, each granule formed from a plurality of particles 301.

[0043] In block 202, the plurality of second granules of the ceramic material are sintered to form a plurality of second sintered granules 302 of the ceramic material. The ceramic powder thereby comprises (larger) particles (e.g., on the order of 100 microns) that are composed of (smaller) particles (e.g., on the order of 2-50 microns) of the ceramic material that are sintered together such that they are ceramicly bonded together. Such sintered granules 302 of the ceramic material are used in examples of the present disclosure as the ceramic powder for a binder jet 3D ceramic printer. In some cases, such sintered granules of the ceramic material 302 can correspond to ceramic beads or artificial sand.

[0044] Figure 3 An overview of the processes and methods described above of the present disclosure is schematically illustrated.

[0045] Figure 3The diagram schematically illustrates multiple particles (301) of a ceramic material that are granulated, agglomerated, and / or aggregated and then sintered to form grains, each particle comprising multiple sintered particles (302). In practice, (larger) grains / fine particles / microparticles are formed by the granulation / agglomeration / agglomeration of (smaller) particles of the ceramic material sintered together to form larger grains / fine particles / microparticles. The granulation / agglomeration / agglomeration and sintering processes are indicated by arrow 200 and correspond to... Figure 2 The process involves using pre-fired crystalline particles as a binder to spray ceramic powder for 3D printing.

[0046] In some examples, initially, the unsintered ceramic material particles (301) have a particle size on the order of 2-50 micrometers. These are granulated / agglomerated / aggregated, for example, using water and an organic binder, to form larger granulated / agglomerated / agglomerated grains with a particle size on the order of 50-150 micrometers. These grains are then sintered to form sintered granulated / agglomerated / agglomerated particles of ceramic material. After the sintering process, any grains larger than a threshold size (e.g., 150 micrometers) and smaller than a threshold size (e.g., 50 micrometers) are sieved / filtered to obtain grains with a particle size range (e.g., 50-150 micrometers) that is optimal / suitable for providing free-flowing powder, and therefore optimal / suitable for use as ceramic powder 302 for binder jet 3D ceramic printers. The granulation / agglomeration / agglomeration process can be configured to produce substantially spherical grains, such grain shape being optimal / suitable for providing free-flowing powder, and therefore optimal / suitable for use as ceramic powder for binder jet 3D ceramic printers.

[0047] Then, the ceramic powder 302 is used by a binder jetting 3D ceramic printer to 3D print a ceramic structure 303 formed from the ceramic powder 302 and the jetted binder. This printing process is indicated by arrow 101 and corresponds to... Figure 1 Process 101.

[0048] Then the ceramic structure 303 is fired to form the ceramic object 307. This firing process is carried out by... Figure 1 Arrow 102 indicates.

[0049] The above method and process can be used to manufacture ceramic objects, not limited to ceramic filters such as ceramic porous cast filters for metal filtration, wherein an initial ceramic porous structure (similar in structure and form to a ceramic cast foam filter) is printed by a 3D ceramic printer and then fired to form the resulting ceramic cast filter. However, it should be appreciated that the method of the present invention is not limited to the manufacture of ceramic cast filters and can manufacture any suitable ceramic object, not limited to, for example: ceramic nozzles (e.g. for metering metal), ceramic flow control devices, technical / engineering ceramics, medical ceramics (e.g. for implants), electroceramics and insulators.

[0050] Examples of the present disclosure have been described using flow diagrams and schematic block diagrams. It should be understood that each block of (the flow diagrams and block diagrams) and combinations of blocks in the multiple blocks can be implemented by any apparatus, device, or machine, such as a computer having at least one processor, that is adapted for performing the functions of the blocks. The plurality of blocks can be implemented by a combination of analog and digital circuits, discrete components, and / or computer hardware and / or software that are adapted for performing the functions of the blocks. Thus, the multiple blocks support combinations of analog and digital circuits, discrete components, and / or computer hardware and / or software that are adapted for performing the functions of the blocks.

[0051] Although features have been described with reference to certain examples, those features can also be present in other examples whether described or not. Although various examples of the present disclosure have been described in the preceding paragraphs, it should be appreciated that modifications can be made to the examples given without departing from the scope of the application as set out in the claims. For example, various examples (and methods of treatment) can be combined.

[0052] The term "comprising" is used in this document to mean "including, but not limited to". Any reference to an element herein using a designation such as "at least one of A and B" should be understood as referring to the element A or the element B, or both element A and element B. Any reference to an element herein using a designation such as "one of A or B" should be understood as referring to the element A or the element B, but not both element A and element B. Any reference to an element herein using a designation such as "one of A, B, or C" should be understood as referring to the element A or the element B or the element C, but not both the element A and the element B, both the element A and the element C, or both the element B and the element C. Any reference to an element herein using a designation such as "one of A, B, and C" should be understood as referring to the element A or the element B or the element C, but not both the element A and the element B, both the element A and the element C, or both the element B and the element C.

[0053] In this specification, reference has been made to various examples. The description of features or functions in relation to an example indicates that the features or functions are present in that example. The use of the term "example" or "for example" or "may" in the text denotes one or more examples. Thus, "example" or "for example" or "may" or "for instance" or "in an example" or "in one example" or "for example" means "one or more examples". Thus, the use of "example" or "for example" or "may" or "for instance" or "in an example" or "in one example" or "for example" does not mean that the example described is the only example possible.

[0054] In this specification, unless expressly stated otherwise, reference to "a / an / the" [feature, element, component, means, etc.] shall be construed to mean "at least one" [feature, element, component, means, etc.].

[0055] While efforts have been made to accord the foregoing specification the attention of those skilled in the art to what is considered to be the most relevant and therefore representative examples of the present disclosure, it should be understood that any ascertainable feature or combination of features that can be granted patent protection under the applicable statutory law can be protected and is reserved, whether or not it is particularly emphasized.

[0056] Examples of the present disclosure and the appended claims can be appropriately combined in any manner apparent to those of ordinary skill in the art.

Claims

1. A method of manufacturing a ceramic object, characterized in that, The ceramic object includes a ceramic foundry filter for metal filtration, and the method includes: 3D printing a ceramic structure by using a binder jet 3D ceramic printer of ceramic powder and an inorganic binder, wherein the ceramic powder includes a sintered ceramic material, the sintered ceramic material includes particles of sintered ceramic material, the particles of sintered ceramic material have a size that is greater than 10 microns and less than 200 microns; and firing the ceramic structure to form the ceramic object.

2. The method of claim 1, wherein, The sintered ceramic material includes a sintered granular ceramic material.

3. The method according to claim 1 or 2, characterized in that, The sintered ceramic material has a porosity that is less than 10%.

4. The method of claim 1, wherein, The ceramic structure undergoes a shrinkage of less than 10% when fired to form the ceramic object.

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

6. The method of claim 1, wherein, The particles of sintered ceramic material have a size that is less than 150 microns.

7. The method of claim 1, wherein, The particles of sintered ceramic material have a size that is greater than 30 microns.

8. The method of claim 1, wherein, Firing the ceramic structure includes firing the ceramic structure to a temperature that is greater than 1000 °C.

9. The method of claim 1 or 2, wherein, The sintered ceramic material has a porosity that is less than 5%.

10. The method of claim 1, wherein, The ceramic structure undergoes a shrinkage of less than 5% when fired to form the ceramic object.

11. The method of claim 1, wherein, The particles of sintered ceramic material have a size that is less than 100 microns.

12. The method of claim 1, wherein, The particles of sintered ceramic material have a size that is less than 50 microns.

13. The method of claim 1, wherein, The particles of sintered ceramic material have a size that is greater than 50 microns.

14. The method of claim 1, wherein, The particles of sintered ceramic material have a size that is greater than 70 microns.

15. The method of claim 1, wherein, Firing the ceramic structure includes firing the ceramic structure to a temperature that is greater than 1200 °C.

16. The method of claim 1, wherein, Firing the ceramic structure includes firing the ceramic structure to a temperature that is greater than 1400 °C.

17. The method of claim 1, wherein, Firing the ceramic structure includes firing the ceramic structure to a temperature that is greater than 1600 °C.

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