Three-dimensional printing kit, method and system using support coating agent

Abstract

A 3D printing kit may include a particulate build material, a binder, and a supportive coating agent. The particulate build material may include about 80 wt% to about 100 wt% of metal particles, based on the total weight of the particulate build material. The binder may include binder particles dispersed in a binder liquid carrier. The supportive coating agent may include ceramic particles having a negative coefficient of thermal expansion, a gelling compound, and a supportive coating liquid carrier.

Description

Technical Field

[0001] The present disclosure relates to three-dimensional printing kits, methods, and systems utilizing supportive coating agents. Background Art

[0002] Three-dimensional (3D) printing can be defined as an additive printing process used to create three-dimensional solid parts from digital models. 3D printing is commonly used for rapid product prototyping, mold generation, master pattern generation, and low-volume manufacturing. Some 3D printing techniques are considered additive processes because they involve the application of successive layers of material. This is different from other machining processes, which typically rely on removing material to create the final part. Some 3D printing methods use chemical binders or adhesives to bind the build materials together. Other 3D printing methods involve partial sintering, melting, etc. of the build material. For some materials, partial melting can be achieved using heat-assisted extrusion, while for some other materials, curing or melting can be achieved using, for example, ultraviolet or infrared light. Summary of the Invention

[0003] A three-dimensional printing kit comprises: a particulate building material, the particulate building material comprising 80 wt% to 100 wt% of metal particles based on the total weight of the particulate building material; a binder, the binder comprising binder particles dispersed in a binder liquid carrier; and a supportive coating agent, the supportive coating agent comprising ceramic particles having a negative thermal expansion coefficient, a gelling compound, and a supportive coating liquid carrier, wherein the ceramic particles comprise zirconium tungstate, wherein the gelling compound is an inorganic gelling compound, and the inorganic gelling compound comprises sodium metasilicate, potassium metasilicate, sodium orthosilicate, sodium disilicate, an organic orthosilicate, tetraethyl orthosilicate, or a combination thereof; and wherein the weight ratio of the ceramic particles to the gelling compound ranges from 1:1 to 1:9.

[0004] A method for three-dimensional printing comprises: repeatedly applying a single build material layer of a particulate build material, the particulate build material comprising 80 wt% to 100 wt% metal particles based on the total weight of the particulate build material; repeatedly applying a binder to the single build material layer based on a three-dimensional object model to define a single patterned object layer, the object layers becoming adhered to each other to form a green object; coating the green object with a supportive coating agent, the supportive coating agent comprising ceramic particles having a negative coefficient of thermal expansion, a gelling compound, and a supportive coating liquid carrier; heating the green object to a coating hardening temperature to harden the supportive coating agent thereon and form a supportive coating on the green object; and heating the green object to a melting temperature of the metal particles that is higher than the coating hardening temperature to form a hot-melt three-dimensional object.

[0005] A three-dimensional printing system comprises: a particulate build material comprising 80 wt% to 100 wt% metal particles, based on the total weight of the particulate build material; a binder applicator fluidly coupled or capable of being coupled to a binder to repeatedly apply the binder to the particulate build material to form a single patterned object layer of a green object; a supportive coating agent comprising ceramic particles having a negative coefficient of thermal expansion, a gelling compound, and a supportive coating liquid carrier to be applied to the green object; and a heat source to heat the green object with the supportive coating agent thereon to a coating hardening temperature to harden the supportive coating agent and form a supportive coating on the green object. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 The figures illustrate an example three-dimensional printing kit according to the present disclosure;

[0007] Figure 2 A flowchart illustrating an example method of three-dimensional printing according to the present disclosure;

[0008] Figure 3A The figures illustrate an example green body having a supportive coating agent applied thereto according to the present disclosure;

[0009] Figure 3B The diagram illustrates an example green body having a supportive coating agent applied thereto according to the present disclosure; and

[0010] Figure 4 The diagrams illustrate an example three-dimensional printing system according to the present disclosure. DETAILED DESCRIPTION

[0011] Three-dimensional printing can be an additive process that includes applying continuous layers of particulate building material (on which a binder is printed) to bind the continuous layers of particulate building material together. In some processes, the application of a binder having a binder can be used to form a green object or product, and then a hot-melt three-dimensional object can be formed, for example, by sintering, annealing, melting, etc. More specifically, a binder can be selectively applied to a layer of particulate building material on a support bed (e.g., a building platform supporting the particulate building material) to pattern selected areas of the particulate building material layer, and then another layer of particulate building material can be applied thereon. The binder can be applied again and then repeated to form a green part (also called a green object or green product), which is then hot-melted to form a hot-melt three-dimensional object. In three-dimensional printing using metal particles, the binder may burn off before the individual metal particles fuse with each other. As a result, during the hot melting process of the particulate building material, the green object may deform by bending, warping, curling, or sagging. In areas where gravity and / or mechanical forces act on the green object, such as in unsupported or protruding areas, the three-dimensional printed article will experience greater deformation.

[0012] Accordingly, the three-dimensional printing kit may include a particulate building material, a binder and a supporting coating agent. Based on the total weight of the particulate building material, the particulate building material may include about 80wt% to about 100wt% of metal particles. The binder may include binder particles dispersed in a binder liquid carrier. The supporting coating agent may include ceramic particles with a negative thermal expansion coefficient, a gelling compound and a supporting coating liquid carrier (e.g., water, alcohol, a combination of water and alcohol, etc.). In one example, the metal particles may be selected from aluminum, titanium, copper, cobalt, chromium, nickel, vanadium, tungsten, tungsten carbide, tantalum, molybdenum, magnesium, gold, silver, stainless steel, steel, its alloy or its mixture. In another example, the metal particles may have a D50 particle size distribution value of about 2μm to about 150μm. In yet another example, the ceramic particles may be selected from zirconium tungstate, titanium carbide, silicon nitride, silicon carbide, boron nitride, kaolin silicate, eucryptite (LiAlSiO4), cordierite (Mg2Al4Si5O 18 ), cyanide, cadmium cyanamide (Cd(CN)2), or a combination thereof. In a further example, the gelling compound can be an inorganic gelling compound selected from sodium metasilicate, potassium metasilicate, sodium orthosilicate, sodium disilicate, an organic orthosilicate, tetraethyl orthosilicate, or a combination thereof. In one example, the weight ratio of the ceramic particles to the gelling compound can range from about 1:1 to about 1:9. In another example, the ceramic particles can include zirconium tungstate and the gelling compound can include sodium metasilicate. The zirconium tungstate can be in the form of particles dispersed in a gel formed by the sodium metasilicate and the supportive coating liquid carrier.

[0013] A method of three-dimensional printing may include repeatedly applying a single build material layer of a particulate build material, the particulate build material comprising from about 80 wt% to about 100 wt% metal particles based on the total weight of the particulate build material; repeatedly applying a binder to the single build material layer based on a three-dimensional object model, the single build material layer defining a single patterned object layer, the object layers becoming adhered to each other to form a green object; coating the green object with a supportive coating agent, the supportive coating agent comprising ceramic particles having a negative coefficient of thermal expansion, a gelling compound, and a supportive coating liquid carrier; heating the green object to a coating hardening temperature to harden the supportive coating agent thereon and form a supportive coating on the green object; and heating the green object to a melting temperature of the metal particles that may be above the coating hardening temperature to form a heat-molten three-dimensional object. In one example, the method may further include removing the supportive coating from the heat-molten three-dimensional object. In another example, removing the supportive coating may include sandblasting, water blasting, dry ice blasting, ice blasting, vacuuming, ultrasonication, brushing, or a combination thereof. In one example, the method can further include preparing a supportive coating agent by dispersing ceramic particles in a gel of a supportive coating liquid carrier and a gelling compound. In another example, coating the green object can include applying a coating having a thickness ranging from about 0.2 mm to about 2 mm. In a further example, heating the green object to a first temperature to harden the supportive coating agent can be performed at a temperature of about 100° C. to about 200° C.; and heating the green object to a second temperature higher than the first temperature can be performed at a temperature of about 10° C. to about 1,050° C. below the melting temperature of the metal particles of the particulate build material for a period of about half an hour to about 24 hours.

[0014] In another example, a three-dimensional printing system may include a particulate building material, a binder applicator, a binder, a supportive coating agent, and a heat source. Based on the total weight of the particulate building material, the particulate building material may include about 80 wt% to about 100 wt% of metal particles. The binder applicator may be fluidically coupled or may be coupled to the binder to repeatedly apply the binder to the particulate building material to form a single patterned object layer of a green object. The supportive coating agent may include ceramic particles having a negative thermal expansion coefficient, a gelling compound, and a supportive coating liquid carrier to be applied to the green object. The heat source is operable to heat the green object with the supportive coating agent thereon to a coating hardening temperature to harden the supportive coating agent and form a supportive coating on the green object. In another example, the system may further include a sintering oven to receive the green object with the supportive coating thereon and heat the green object with the supportive coating thereon to a melting temperature of the metal particles to form a hot-melt three-dimensional object; or the heat source may be a sintering oven to heat the green object with the supportive coating thereon to a melting temperature of the metal particles that may be higher than the hardening temperature of the coating, thereby heating the green object to a temperature sufficient to form a hot-melt three-dimensional object.

[0015] When discussing a 3D printing kit, a 3D printing method, and / or a 3D printing system herein, such discussion is considered to apply to each other, regardless of whether or not such discussion is explicitly made in the context of that example. Thus, for example, when discussing a support coating agent in relation to a 3D printing kit, such disclosure is also relevant to and directly supported in the context of a 3D printing method or system, and vice versa.

[0016] Unless otherwise specified, the terms used herein will have their ordinary meanings in the technical field. In some cases, some terms are more specifically defined throughout the specification or included at the end of this specification, and therefore, these terms may have the meanings as described herein.

[0017] 3D printing kit

[0018] According to an example of the present disclosure, a three-dimensional (3D) printing kit 100 is displayed on Figure 1 The three-dimensional printing kit may include a particulate building material 110, a binder 120, and a supportive coating agent 130. Based on the total weight of the particulate building material, the particulate building material may include about 80 wt% to about 100 wt% of metal particles 112. The binder may include binder particles 122 dispersed in a binder liquid carrier 124. The supportive coating agent may include ceramic particles 132 having a negative thermal expansion coefficient (e.g., metal oxide ceramic particles, non-oxide ceramic particles, etc.), as well as a gelling compound 134 and a supportive coating liquid carrier 136 (which may include water, alcohol, or a combination thereof). The particulate building material may be packaged together with the binder and / or supportive coating agent or packaged together in a separate container, and / or may be combined with each other during printing, for example, loaded together in a three-dimensional printing system.

[0019] As used herein, the term "ceramic particles" refers to inorganic crystalline particles of oxides, nitrides, tungstates, silicates, eucryptite, cordierite, cyanide, cyanamide, carbides, titanates, or aluminates, in the form of crystalline particles. Ceramics may include metal oxide ceramics or non-metallic ceramics. Examples include zirconium tungstate, titanium carbide, silicon nitride, silicon carbide, boron nitride, kaolin silicate, eucryptite, cordierite, cyanide, calcium cyanamide, or combinations thereof.

[0020] 3D printing method

[0021] A flowchart of an example method 200 of three-dimensional (3D) printing is shown in FIG. Figure 2The method may include repeatedly applying 210 a single build material layer of a particulate build material, the particulate build material may include about 80 wt% to about 100 wt% metal particles based on the total weight of the particulate build material; and repeatedly applying 220 a binder to the single build material layer based on the three-dimensional object model to define a single patterned object layer, the object layers may become adhered to each other to form a green object. The method may further include coating 230 the green object with a supportive coating agent, the supportive coating agent may include ceramic particles having a negative thermal expansion coefficient, a gelling compound, and a supportive coating liquid carrier; heating 240 the green object to a coating hardening temperature to harden the supportive coating agent thereon and form a supportive coating on the green object; and heating 250 the green object to a melting temperature of the metal particles, which may be higher than the coating hardening temperature, to form a heat-molten three-dimensional object.

[0022] In a layer-by-layer printing process, the particulate building material can be spread out, a binder can be applied, and then the build platform can be lowered a certain distance (x), which in one example can be about 5 μm to about 1 mm, which can correspond to the thickness of the printed layer of the green object, so that another layer of particulate building material can be added thereon to receive another application of the binder, and so on. This process can be repeated on a layer-by-layer basis until the entire green object is formed. A "green" object (or a single layer) can refer to any component or mixture of components that has not yet been sintered or annealed, but they are combined together in a manner sufficient to allow heat fusion, for example, to process, move or otherwise prepare the part for subsequent coating with a supportive coating agent and heat fusion. During the build process, in one example, heat can be applied from above and / or can be provided by the build platform from below the particulate building material to remove water and / or other liquid components and further solidify the layers of the green object. In other examples, the particulate building material can be heated before being dispensed.

[0023] After the green object is formed, a supportive coating agent 312 may be applied as a partial coating along selected areas of the green object 310 that may otherwise be unsupported during the hot melt process, e.g. Figure 3A In yet another example, the support coating agent 312 can be applied as a coating around a portion of the outer surface of the green object 310, such as Figure 3B As shown. In a further example, the supportive coating agent can be applied as a complete coating on all outer surfaces of the green object. Applying the supportive coating agent to the green object can include any application process. For example, application can include dipping, spraying, brushing, or extrusion. The supportive coating agent can be applied to the surface of the green object in a thickness range of about 0.2 mm to about 2 mm, about 0.75 mm to about 1.75 mm, about 1 mm to about 2, or about 0.5 mm to about 1.5 mm.

[0024] After coating the green body object with the supportive coating agent thereon, the whole green body object with the supportive coating agent thereon can be moved to a heat source. The heat source is not limited and can include, for example, an oven (which can be the same oven for subsequently sintering the green body object), a hot plate, a gas incubator, an infrared radiation source, an electromagnetic radiation source or an electron beam source etc. The heat source can be used to heat the green body object with the supportive coating agent thereon to a coating hardening temperature to harden the supportive coating agent. The coating hardening temperature can vary according to the supportive coating agent. In some instances, the scope of the coating hardening temperature can be about 75 ℃ to about 300 ℃, about 100 ℃ to about 200 ℃, about 125 ℃ to about 175 ℃ or about 100 ℃ to about 120 ℃.

[0025] The green body object with the supportive coating agent of hardening can then be further heated to a temperature that can be higher than the coating hardening temperature to form a three-dimensional object of heat melting. The heat source is not limited and can include any of the above-mentioned heat sources. The heat source can be the same heat source as the heat source for hardening the supportive coating agent, or it can be a heat source different from the heat source for hardening the supportive coating agent. In an example, the green body object can be heat-melted by sintering and / or annealing. The term "sintering" or "sintering" refers to a combination of solid-state diffusion bonding, partial melting of metal particles or solid-state diffusion bonding and partial melting, and metal particles are consolidated and physically bonded together (after using a binder to temporarily bond). The term "annealing" or "annealing" refers to the heating and cooling continuous events of controlling heating process and cooling process, for example, slowly cooling can remove internal stress and / or make the three-dimensional object of heat melting become tough in some cases.

[0026] The temperature at which the particles of the particulate building material fuse to each other can vary depending on the metal particles of the particulate building material. In one example, the thermal melting temperature can range from about 10°C below the melting temperature of the metal particles of the particulate building material to about 1,500°C below the melting temperature of the metal particles of the particulate building material. In another example, the thermal melting temperature can range from about 400°C below the melting temperature of the metal particles of the particulate building material to about 500°C below the melting temperature of the metal particles of the particulate building material. In yet another example, the thermal melting temperature can range from about 500°C below the melting temperature of the metal particles of the particulate building material to about 1,000°C below the melting temperature of the metal particles of the particulate building material.

[0027] The hot melt temperature may also depend on the particle size and the time period over which heating occurs, e.g., sufficient time at high temperature to allow the particle surfaces to become physically fused or composited together. For example, stainless steel may have a hot melt temperature of about 1400°C, and examples of hot melt temperatures for aluminum or aluminum alloys may range from about 550°C to about 620°C. In one example, the hot melt temperature may range from about 400°C to about 3,500°C. In another example, the temperature may range from about 600°C to about 1,500°C or from about 800°C to about 1200°C. The hot melt temperature may fuse the particles of the particulate building material to each other, thereby forming a hot-melt three-dimensional object.

[0028] In some examples, the heat source can be configured to include a controlled atmosphere. For example, the controlled atmosphere can include an inert atmosphere of a noble gas, an inert gas, a reactive gas, or a combination thereof. In another example, the heat source can be associated with a vacuum. The vacuum can be configured to vary the pressure within the heat source. In yet another example, the heat source can maintain ambient conditions.

[0029] In a further example, the method may include removing the hardened support coating from the hot melt three-dimensional object. The hardened support coating may be removed by sandblasting, water blasting, dry ice blasting, ice blasting, vacuum treatment, ultrasonic treatment, brushing, or a combination thereof. In one example, the hardened support coating may be removed by sandblasting and brushing the hardened support coating off the hot melt three-dimensional object.

[0030] 3D printing system

[0031] 3D printing system 400 by Figure 4 . The three-dimensional printing system may include a particulate building material 110, a binder applicator 420, a binder 120, a supportive coating agent 130, and a heat source 430. Based on the total weight of the particulate building material, the particulate building material may include about 80 wt% to about 100 wt% of metal particles 112. The binder applicator may be fluidly coupled or coupled to the binder to repeatedly apply the binder to the particulate building material to form a single patterned object layer of the green object. The supportive coating agent may include ceramic particles 132 (e.g., metal oxide particles, non-oxide particles, etc.) having a negative thermal expansion coefficient, a gelling compound 134, and a supportive coating liquid carrier 136. The supportive coating agent may be formulated to be applied as a coating to the green object. The heat source is operable to heat the green object having the supportive coating agent thereon to a coating hardening temperature to harden the supportive coating agent and form a supportive coating on the green object.

[0032] The binder applicator can be any type of device capable of selectively applying a binder. For example, the binder applicator can be a fluid ejector or a digital fluid ejector, such as an inkjet print head, for example, a piezoelectric print head, a thermal print head, a continuous print head, etc. The binder applicator can also be a sprayer, a dropper, or other similar structure for applying a binder to a particulate building material. Figure 4 In the illustrated example, the binder applicator is shown on the carriage track 422, but can be supported by any of several structures. The binder applicator can be fluidically coupled or can be coupled to the binder and can directly apply the binder to the particulate building material to form a layered green object. Therefore, in some examples, the application can be performed by spraying or ejecting from a digital fluid jet applicator similar to an inkjet pen. In another example, the binder applicator can include a motor and, when positioned above or near the powder bed of the build platform, can be operated to move back and forth along the carriage track above the particulate building material.

[0033] Other aspects of the three-dimensional printing system may include a building platform that supports particulate building materials. The building platform may be positioned to receive a binder from a binder applicator onto a layer of particulate building materials. The building platform may be configured to drop in height, thereby allowing a continuous layer of particulate building materials to be applied by a supply and / or applicator. The particulate building materials may be layered in the building platform with a thickness ranging from about 5 μm to about 1 mm. In some instances, a single layer may have a relatively uniform thickness. In one example, the thickness of a layer of particulate building materials may range from about 10 μm to about 500 μm or from about 30 μm to about 200 μm.

[0034] Microparticle building materials

[0035] As described herein, a particulate building material 110 that can be used in a three-dimensional (3D) printing method or present in a 3D printing kit or 3D printing system can include about 80 wt% to 100 wt%, about 90 wt% to 100 wt%, about 95 wt% to 100 wt%, or about 99 wt% to 100 wt% of metal particles 112, based on the total weight of the particulate building material. In one example, the metal particles can be elemental metals, such as elemental transition metals. Examples can include titanium, copper, cobalt, chromium, nickel, vanadium, tungsten, tungsten carbide, tantalum, molybdenum, gold, silver, etc. The metal particles can also be aluminum (which is not a transition metal), or can be alloys of multiple metals, or can include metalloids. In some examples, the alloy can be steel or stainless steel. Even if the steel includes carbon, according to examples of the present disclosure, it is still considered a metal due to its metalloid properties. The metal particles can be a mixture of any of these materials. In one example, the metal particles can include aluminum, titanium, copper, cobalt, chromium, nickel, vanadium, tungsten, tungsten carbide, tantalum, molybdenum, gold, silver, aluminum, stainless steel, steel, alloys thereof, or mixtures thereof.

[0036] The metal particles can exhibit good flowability and can have shapes such as spherical, irregularly spherical, round, semi-round, disc-shaped, angular, slightly angular, cubic, cylindrical, or any combination thereof, to name a few. In one example, the metal particles can include spherical particles, irregularly spherical particles, round particles, or other particle shapes having an aspect ratio of 1.5:1 to 1:1, 1.2:1 to 1:1. In some examples, the shape of the metal particles can be uniform or substantially uniform, which can allow for relatively uniform melting or sintering of the particles after the three-dimensional green part is formed and then thermally melted in, for example, a sintering or annealing oven.

[0037] The particle size distribution may also vary. Accordingly, in one example, the metal particles may have a D50 particle size distribution value that can range from about 2 μm to about 150 μm, about 5 μm to about 125 μm, or about 50 μm to about 100 μm. In other examples, the metal particles may have a D10 particle size distribution value that can range from about 1 μm to about 125 μm, about 1 μm to about 100 μm, or about 2 μm to about 125 μm. In another example, the D90 particle size distribution value of the metal particles may range from about 2.5 μm to about 200 μm or about 4 μm to about 150 μm. As used herein, particle size may refer to the diameter value of a spherical particle, or in non-spherical particles, may refer to the equivalent spherical diameter of the particle. Particle size may be a Gaussian distribution or a Gaussian-like distribution (or a normal or quasi-normal distribution). A quasi-Gaussian distribution is a distribution curve that appears to be in the shape of a Gaussian distribution curve, but it may be slightly skewed in one direction or the other (towards the smaller end of the particle size distribution range or towards the larger end of the particle size distribution range). In these or other types of particle distributions, the particle size may be characterized in a manner using the 50th percentile of the particle size (sometimes referred to as the "D50" particle size). For example, a D50 value of about 25 μm means that about 50% of the particles (by volume) have a particle size greater than about 25 μm and about 50% of the particles have a particle size less than about 25 μm. Regardless of whether the particle size distribution is Gaussian, quasi-Gaussian, or otherwise, the particle size distribution may be expressed in terms of a D50 particle size, which may generally be close to the average particle size, but may also be different. In the examples herein, the particle size range may be modified to refer to the "average particle size," sometimes providing a slightly different size distribution range.

[0038] The metal particles can be produced using any manufacturing method. However, in one example, the metal particles can be produced using a gas atomization process. In gas atomization, molten metal is atomized by an inert gas jet into fine metal droplets, which cool as they fall into an atomization tower. Gas atomization can allow for the formation of particles that are largely spherical. In another example, the metal particles can be produced using a liquid atomization process.

[0039] binder

[0040] In more detail, as described herein, for a binder 120 that can be used in a three-dimensional (3D) printing method or present in a 3D printing kit or 3D printing system, the binder can include binder particles 122 and a binder liquid carrier 124. The term "binder particles" can include any material that is used to physically bind individual metal particles together or facilitate adhesion to the surfaces of adjacent metal particles in order to prepare a green part or green object in preparation for subsequent thermal fusion (e.g., sintering, annealing, melting, etc.). During the 3D printing process, the binder can be applied to the particulate build material on a layer-by-layer basis. For example, the binder liquid carrier of the binder can wet the particulate build material, and the binder particles can move into the spaces between the metal particles of the particulate build material.

[0041] The binder can provide bonding to the particulate building material after application, or in some cases, can be activated to provide bonding after application. The binder particles can be activated or cured by heating the binder particles (this can be achieved by heating the entire layer of particulate building material on a portion of the binder that has been selectively applied). If the binder particles include a polymeric binder, this can occur, for example, at about the glass transition temperature of the polymeric binder particles. When activated or cured, the binder particles can form a network that can bond or glue the metal particles of the particulate building material together, thereby providing cohesion when forming and / or maintaining the shape of the green object or its printed layer.

[0042] Thus, in one example, the green object can have the mechanical strength to withstand extraction from the powder bed, coating with a support coating agent, and heat melting. Once the green object is heat melted, the object is referred to herein as a "fused" three-dimensional article, component, or object. In some examples, the binder particles contained in the binder can undergo a pyrolysis or burnout process at about 250°C to about 700°C, where the binder particles can be removed during sintering or annealing. This occurs when the thermal energy applied to the green component or object removes inorganic or organic volatiles and / or other materials that may be present by decomposing or by burning the binder.

[0043] As described above, the binder particles can be included in a binder liquid carrier for application to the particulate build material. For example, the binder particles can be present in the binder at about 1 wt% to about 50 wt%, about 2 wt% to about 30 wt%, about 5 wt% to about 25 wt%, about 10 wt% to about 20 wt%, about 7.5 wt% to about 15 wt%, about 15 wt% to about 30 wt%, about 20 wt% to about 30 wt%, or about 2 wt% to about 12 wt% of the binder.

[0044] In one example, the binder particles may include a copper nitrate binder. In another example, the binder particles may include polymer particles, such as latex polymer particles. The polymer particles may have an average particle size that may range from about 100 nm to about 1 μm. In other examples, the polymer particles may have an average particle size that may range from about 150 nm to about 300 nm, from about 200 nm to about 500 nm, or from about 250 nm to 750 nm.

[0045] In one example, the latex particles may include any of several comonomers, and in some cases, co-surfactants, such as polyoxyethylene compounds, polyoxyethylene alkylphenyl ether ammonium sulfate, polyoxyethylene alkyl ether sodium sulfate, polyoxyethylene styrenated phenyl ether ammonium sulfate, etc. The comonomers may be derived from monomers such as styrene, p-methylstyrene, α-methylstyrene, methacrylic acid, acrylic acid, acrylamide, methacrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, methyl methacrylate, hexyl acrylate, hexyl methacrylate, butyl acrylate, butyl methacrylate, ethyl acrylate, ethyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, propyl acrylate, propyl methacrylate, octadecyl acrylate, octadecyl methacrylate, stearyl methacrylate, vinylbenzyl chloride, isobornyl acrylate, tetrahydrofurfuryl acrylate, methyl 2-phenoxyethyl acrylate, benzyl methacrylate, benzyl acrylate, ethoxylated nonylphenol methacrylate, ethoxylated behenyl methacrylate, polypropylene glycol monoacrylate, isobornyl methacrylate, cyclohexyl methacrylate, cyclohexyl acrylate, t-butyl methacrylate, n-octyl methacrylate, lauryl methacrylate, tridecyl methacrylate, alkoxylated tetrahydrofurfuryl acrylate, isodecyl acrylate, isobornyl methacrylate, isobornyl acrylate, dimethyl maleate, dioctyl maleate, acetoacetoxyethyl methacrylate, diacetone acrylamide, N-vinyl imidazole, N-vinyl carbazole, N-vinyl-caprolactam, or a combination thereof. In some examples, the latex particles may include acrylic acid. In other examples, the latex particles may include 2-phenoxyethyl methacrylate, cyclohexyl methacrylate, cyclohexyl acrylate, methacrylic acid, a combination thereof, a derivative thereof, or a mixture thereof. In another example, the latex particles can include styrene, methyl methacrylate, butyl acrylate, methacrylic acid, combinations thereof, derivatives thereof, or mixtures thereof.

[0046] For the binder liquid carrier, based on the weight of the binder as a whole, the binder may include about 50wt% to about 99wt%, about 70wt% to about 98wt%, about 80wt% to about 98wt%, about 60wt% to about 95wt% or about 70wt% to about 95wt% binder liquid carrier. In one example, the binder liquid carrier may include water as the main solvent, for example, when compared with other cosolvents, the solvent is present in the highest concentration. In another example, the binder liquid carrier may further include about 0.1wt% to about 70wt%, about 0.1wt% to about 50wt% or about 1wt% to about 30wt% of liquid components other than water. Other liquid components may include organic cosolvents, surfactants, additives that inhibit the growth of harmful microorganisms, viscosity modifiers, pH modifiers, chelating agents, preservatives, etc.

[0047] When present, the organic co-solvent can include a high boiling point solvent and / or wetting agent, for example, an aliphatic alcohol, an aromatic alcohol, an alkyl glycol, a glycol ether, a polyethylene glycol ether, 2-pyrrolidone, caprolactam, formamide, acetamide, a C6 to C24 aliphatic alcohol (e.g., a medium (C6-C12) to long (C13-C24) chain length fatty alcohol), or a mixture thereof. The organic co-solvent in the aggregate can be present in the binder at 0 wt % to about 50 wt %. In other examples, the organic co-solvent can be present in the binder at about 5 wt % to about 25 wt %, about 2 wt % to about 20 wt %, or about 10 wt % to about 30 wt %.

[0048] Support coating agent

[0049] Before the particles of the particulate building material are melted, a supportive coating agent can be applied to the green object and hardened to form a supportive coating or shell for the green object. Thus, the supportive coating agent can counteract deformation of the green object that may occur during the hot melt process, which can occur between the burnout of the binder and the melting of the particles of the particulate building material. For example, the supportive coating agent can form a structure that prevents the green object from bending, warping, curling, or sagging during the hot melt process.

[0050] A supportive coating agent that can be used as described herein can include ceramic particles having a negative coefficient of thermal expansion, a gelling compound, and a supportive coating liquid carrier 136 (e.g., water, alcohol, water and alcohol, etc.). In some examples, the supportive coating agent can be prepared by dispersing the ceramic particles in a gel that can include the supportive coating liquid carrier and the gelling compound.

[0051] In one example, the ceramic particles may have a negative thermal expansion coefficient. The negative thermal expansion coefficient may allow the supportive coating to shrink in size during the hot melt process, thereby allowing the supportive coating to shrink along with the green object. The ceramic particles may have a negative thermal expansion coefficient. The ceramic particles may be metal oxide ceramic particles, non-oxide ceramic particles, etc. For example, the ceramic particles may include zirconium tungstate, titanium carbide, silicon nitride, silicon carbide, boron nitride, kaolin silicate, eucryptite (LiAlSiO4), cordierite (Mg2Al4Si5O 18 ), cyanide, cadmium cyanamide (CdCN2), or a combination thereof. In one example, the ceramic particles may include zirconium tungstate. The ceramic particles may be present in the supportive coating agent at about 10 wt% to about 50 wt%. In another example, the ceramic particles may be present in the supportive coating agent at about 15 wt% to about 30 wt%, about 20 wt% to about 40 wt%, or about 30 wt% to about 50 wt%.

[0052] The ceramic particles may have a D50 particle size of about 0.5 μm to about 150 μm, about 0.5 μm to about 100 μm, about 1 μm to about 100 μm, or about 2 μm to about 150 μm. In other examples, the ceramic particles may have a D10 particle size distribution value that may range from about 0.1 μm to about 100 μm, about 1 μm to about 50 μm, or about 20 μm to about 100 μm. In another example, the ceramic particles may have a D90 particle size distribution value that ranges from about 2 μm to about 200 μm or from about 5 μm to about 150 μm.

[0053] In more detail, the gelling compound may be an inorganic gelling compound including a silicate. For example, the gelling compound may be selected from sodium metasilicate, potassium metasilicate, sodium orthosilicate, sodium disilicate, organic orthosilicate, tetraethyl orthosilicate, or a combination thereof. In one example, the gelling compound may include sodium metasilicate.

[0054] In one example, the ceramic particles may include zirconium tungstate and the gelling compound may include sodium metasilicate. The zirconium tungstate may be in the form of particles dispersed in a gel formed from the sodium metasilicate and a supportive coating liquid carrier. The weight ratio of the ceramic particles to the gelling compound may range from about 1:1 to about 1:9, about 1:1 to about 1:5, or about 1:2 to about 1:7.

[0055] The supportive coating liquid carrier can be similar to the carrier used for the binder liquid carrier. However, in one example, the supportive coating liquid carrier can be water. In another example, the supportive coating liquid carrier can be an alcohol, such as methanol, ethanol, isopropanol, n-propanol, etc. In another example, the supportive coating liquid carrier can include both water and alcohol. In still other examples, the supportive coating liquid carrier can further include an organic cosolvent (other than or in addition to the alcohol), a surfactant, a biocide, and / or other liquid carrier components that may be suitable for a given formulation.

[0056] definition

[0057] It must be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates otherwise.

[0058] When referring to a numerical value or range, the term "about" as used herein allows for a certain degree of variability in the value or range, for example, within 10% of the stated value or the limits of the stated range, or within 5% in one aspect. When modifying a numerical range, the term "about" is also understood to include the range defined by the precise numerical value indicated as a numerical subrange, for example, a range of about 1 wt% to about 5 wt% includes 1 wt% to 5 wt% as an explicitly supported subrange.

[0059] As used herein, the term "green body" is used to describe any of several intermediate structures of particles before the melting of the particle material, such as a green body article, a green body object, a green body layer, etc. As a "green body" structure, the particulate building material can be (weakly) bound together by a binder. Typically, the mechanical strength of the green body is such that the green body can be handled or extracted from the particulate building material on a build platform to be placed in, for example, a sintering oven. It should be understood that any particulate building material that is not patterned with a binder is not considered to be part of a "green body" structure, even if the particulate building material is adjacent to or around a green body object or layer thereof. For example, unprinted particulate building material can be used to support a green body object while being contained therein, but the particulate building material is not part of a green body structure unless the particulate building material is printed with a binder or some other fluid for generating a solidified part before melting (e.g., sintering, annealing, melting, etc.).

[0060] As used herein, "kit" may be synonymous with a plurality of compositions comprising a plurality of components, and may be understood to include a plurality of compositions comprising a plurality of components, wherein different compositions may be contained separately before use (although in some cases packaged together in separate containers), but these components may be combined together during use (such as the three-dimensional object construction process described herein). The container may be any type of vessel, box, or container made of any material.

[0061] As used herein, "applying," when referring to a binder that can be used, refers to, for example, any technique that can be used to place or deposit a fluid agent (e.g., a binder) onto or within a layer of a particulate build material for forming a green object. For example, "applying" can refer to "spraying," "squirting," "drip," or "spraying," among others.

[0062] As used herein, "jetting" or "ejection" refers to a fluid reagent or other composition discharged from a jetting or ejection structure (such as an inkjet structure). The inkjet structure may include a thermal structure or a piezoelectric structure. In addition, this structure can be configured to print different drop sizes, such as up to about 20 picoliters, up to about 30 picoliters, or up to about 50 picoliters. Example ranges may include from about 2 picoliters to about 50 picoliters or from about 3 picoliters to about 12 picoliters.

[0063] As used herein, for convenience, multiple items, structural elements, compositional elements, and / or materials may appear in a common list. However, these lists should be interpreted as if the individual items in the list were identified as separate and unique items. Therefore, in the absence of contrary indications, no individual item in the list should be interpreted as a de facto equivalent based on any other item in the same list presented in a common group.

[0064] Concentration, size, amount and other numerical data can be presented in range form in this article.It should be understood that this range form is used only for convenience and brevity, and should be flexibly interpreted as including the numerical value clearly enumerated as the limit of range, and including all single numerical values or subranges contained in the range when clearly enumerating single numerical value and / or subrange.For example, the weight ratio range of about 1wt% to about 20wt% should be interpreted as including the limit of 1wt% and 20wt% clearly enumerated, and including separate weight, such as about 2wt%, about 11wt%, about 14wt%, and subrange, such as about 10wt% to about 20wt%, about 5wt% to about 15wt% etc.

[0065] The following illustrates embodiments of the present disclosure. However, it should be understood that the following is merely an illustration of the application of the principles of the present disclosure. Numerous modifications and alternative compositions, methods, and systems may be devised without departing from the present disclosure. The appended claims are intended to cover such modifications and arrangements.

[0066] Example

[0067] Two three-dimensional objects (control object and object A) were produced using a layer-by-layer powder bed printing process. All particulate build materials selected for use comprised 99 wt% copper particles with an average particle size of 50 μm. The binder comprised copper nitrate binder. The object build process was as follows:

[0068] 1) Spread the particulate building material evenly on the building platform with an average thickness of about 70 μm to form a building material layer.

[0069] 2) Selectively applying a binding agent comprising binder particles to portions of the build material layer.

[0070] 3) The spreading of the particulate building material (1) and the application of the binder (2) are then repeated until a green object having multiple layers is formed.

[0071] 4) Heating the powder bed to a temperature in the range of about 70°C to about 100°C for about 1 hour to remove a portion of the solvent in the binder.

[0072] 5) The resulting green object had a staple-like shape with the support beams being 28 mm long, which were removed from the particulate build material.

[0073] 6) A "control object" was set aside for hot melting with no support coating applied thereto.

[0074] 7) Prepare the support coating agent according to the following general procedure:

[0075] a. Mix about 1,600 mg to about 3,500 mg of sodium metasilicate in about 300 mL to 450 mL of distilled water over a hot plate.

[0076] b. After a dark white viscous gel is formed, the mixture is removed from the hot plate and about 3,000 mg to 15,000 mg of zirconium tungstate (which has a negative coefficient of thermal expansion) is added thereto.

[0077] 8) "Object A" (one of the prepared green objects) is dip-coated with a support coating agent before heat melting. Object A is then immersed in the support coating agent and quickly removed therefrom. Object A, with the support coating thereon, is then slowly heated to approximately 100°C to evaporate water from the support coating and cure the coating on Object A.

[0078] 9) The control object and Object A (with the cured supportive coating) were heat-fused in a sintering oven. The sintering cycle involved increasing the oven's internal temperature by 2.5°C to 5°C per minute to a target sintering temperature of 1040°C, maintaining the temperature at various levels (e.g., 300°C) for several one- to two-hour intervals. Once the temperature reached 1040°C, it was maintained for four hours. The sintering cycle degraded and removed the binder, sintering the copper particles together.

[0079] 10) Allow both objects to cool.

[0080] 11) Object A including the support coating applied thereto is sandblasted and brushed to remove remaining support coating agent residues.

[0081] In contrast, the control object deformed during the hot melt process. The resulting "staple" configuration of the three-dimensional object included a downward arc along the support beam crossbars, which was absent when the green object was placed in the melting oven. Object A, on the other hand, maintained the horizontal shape of the support beam crossbars during the hot melt process, as exhibited by the original green object. Therefore, the supportive coating agent applied to the surface of the green object prevented the object from deforming during the sintering process.

Claims

1. A three-dimensional printing kit comprising: a particulate building material comprising from 80 wt % to 100 wt % of metal particles, based on the total weight of the particulate building material; a binder comprising binder particles dispersed in a binder liquid carrier; as well as a supportive coating agent comprising ceramic particles having a negative coefficient of thermal expansion, a gelling compound, and a supportive coating liquid carrier, wherein the ceramic particles include zirconium tungstate, wherein the gelling compound is an inorganic gelling compound, and the inorganic gelling compound comprises sodium metasilicate, potassium metasilicate, sodium orthosilicate, sodium disilicate, organic orthosilicate, tetraethyl orthosilicate or a combination thereof; and The weight ratio of the ceramic particles to the gelling compound is in the range of 1:2 to 1:

7.

2. The three-dimensional printing kit of claim 1, wherein the metal particles are selected from aluminum, titanium, copper, cobalt, chromium, nickel, vanadium, tungsten, tungsten carbide, tantalum, molybdenum, magnesium, gold, silver, stainless steel, steel, or mixtures thereof. 3 . The three-dimensional printing kit of claim 1 , wherein the metal particles have a D50 particle size distribution value of 2 μm to 150 μm.

4. The three-dimensional printing kit of claim 1 , wherein the ceramic particles comprise zirconium tungstate and the gelling compound comprises sodium metasilicate, and wherein the zirconium tungstate is in the form of particles dispersed in a gel formed by the sodium metasilicate and the supportive coating liquid carrier.

5. A three-dimensional printing method comprising: repeatedly applying a single build material layer of a particulate build material comprising from 80 wt % to 100 wt % metal particles, based on the total weight of the particulate build material; repeatedly applying a binding agent to a single build material layer based on the three-dimensional object model to define a single patterned object layer, the object layers becoming adhered to each other to form a green object; coating the green object with a supportive coating agent comprising ceramic particles having a negative coefficient of thermal expansion, a gelling compound, and a supportive coating liquid carrier; heating the green object to a coating hardening temperature to harden the supportive coating agent thereon and form a supportive coating on the green object; as well as heating the green object to a melting temperature of the metal particles above the hardening temperature of the coating to form a hot-fused three-dimensional object, wherein the ceramic particles include zirconium tungstate, wherein the gelling compound is an inorganic gelling compound, and the inorganic gelling compound comprises sodium metasilicate, potassium metasilicate, sodium orthosilicate, sodium disilicate, organic orthosilicate, tetraethyl orthosilicate or a combination thereof; and The weight ratio of the ceramic particles to the gelling compound is in the range of 1:2 to 1:

7.

6. The method of claim 5, further comprising removing the support coating from the heat-fused three-dimensional object.

7. The method of claim 6, wherein the removing of the supportive coating comprises sandblasting, water blasting, dry ice blasting, ice blasting, vacuum treatment, ultrasonic treatment, brushing, or a combination thereof.

8. The method of claim 5, wherein the method further comprises preparing the supportive coating agent by dispersing the ceramic particles in a gel of the supportive coating liquid carrier and the gelling compound.

9. The method of claim 5, wherein coating the green object comprises applying the coating at a thickness of 0.2 mm to 2 mm.

10. The method of claim 5, wherein heating the green object to a first temperature to harden the supportive coating agent is performed at a temperature of 100° C. to 200° C.; and heating the green object to a second temperature higher than the first temperature is performed at a temperature of 10° C. to 1,050° C. below the melting temperature of the metal particles of the particulate build material for a period of time of half an hour to 24 hours.

11. A three-dimensional printing system comprising: a particulate building material comprising from 80 wt % to 100 wt % of metal particles, based on the total weight of the particulate building material; a binder applicator fluidly coupled or coupleable to a binder to repeatedly apply the binder to the particulate build material to form a single patterned object layer of a green object; a supportive coating agent comprising ceramic particles having a negative coefficient of thermal expansion, a gelling compound, and a supportive coating liquid carrier for application to the green object; as well as a heat source to heat the green object having the supportive coating agent thereon to a coating hardening temperature to harden the supportive coating agent and form a supportive coating on the green object, wherein the ceramic particles include zirconium tungstate, wherein the gelling compound is an inorganic gelling compound, and the inorganic gelling compound comprises sodium metasilicate, potassium metasilicate, sodium orthosilicate, sodium disilicate, organic orthosilicate, tetraethyl orthosilicate or a combination thereof; and The weight ratio of the ceramic particles to the gelling compound is in the range of 1:2 to 1:

7.

12. The three-dimensional printing system of claim 11, wherein: The system further comprises a sintering oven to receive the green object with the supportive coating thereon and heat the green object with the supportive coating thereon to a metal particle melting temperature to form a hot-fused three-dimensional object; or The heat source is a sintering oven to heat the green object with the supportive coating thereon to a melting temperature of the metal particles above the hardening temperature of the coating, thereby heating the green object sufficiently to form a heat-fused three-dimensional object.

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