3D printing

Abstract

Kits, methods, and systems for printing metal three-dimensional objects are described herein. In one example, a multi-fluid kit for three-dimensional printing is described, comprising: a first fluid comprising a first liquid vehicle comprising metal or metal precursor particles; and a second fluid comprising a second liquid vehicle comprising latex polymer particles dispersed therein, wherein the latex polymer particles have an average particle size of about 10 nm to about 300 nm, and wherein the metal or metal precursor particles comprise metal nanoparticles, metal oxide nanoparticles, metal oxide nanoparticles and a reducing agent, or a combination thereof.

Description

[0001] background

[0002] Three-dimensional (3D) printing is an additive printing method used to create three-dimensional solid parts from digital models. 3D printing is commonly used for rapid product prototyping, mold creation, master pattern generation, and low-volume manufacturing. Some 3D printing techniques are considered additive because they involve applying successive layers of material. This differs from conventional machining methods, which typically rely on removing material to create the final part. 3D printing often utilizes the solidification or sintering of build materials, which for some materials can be achieved using heat-assisted extrusion, melting, or sintering. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Features of examples of the present disclosure will become apparent with reference to the following detailed description and accompanying drawings, in which like reference numerals correspond to similar, but possibly different, components. For the sake of brevity, reference numerals or features having a previously described function may or may not be described in connection with other drawings in which they appear.

[0005] Figure 1 is a simplified isometric view of an exemplary 3D printing system disclosed herein;

[0006] Figures 2A to 2F is a schematic diagram depicting the formation of a patterned green part, a cured green part, an at least substantially polymer-free gray part, and a 3D metal part using an example of a 3D printing method disclosed herein;

[0007] Figure 3 is a flow chart illustrating another example of the 3D printing method disclosed herein;

[0008] Figure 4 (a)–(d) Scanning electron microscopy (SEM) images showing the evolution of a latex polymer binder fluid deposited on stainless steel powder and then pulse-heated through different temperatures.

[0009] Figure 5 (a)-(f) SEM images showing the evolution of metal oxide binder fluid and latex polymer binder fluid sequentially deposited on stainless steel powder and then pulse-heated through different temperatures;

[0010] Figure 6 (a)-(c) SEM images showing the evolution of metal oxide binder fluids and latex polymer binder fluids deposited in different sequences and layers on stainless steel powder and then pulse heated through different temperatures; and

[0011] Figure 7 show Figure 6 (c) 2500X magnified image.

[0012] Details

[0013] In some examples of three-dimensional (3D) printing, a binder fluid (also known as a liquid functional agent / material) is selectively applied to a layer of build material in a powder bed. Application of a layer of build material and then a layer of binder fluid can, as these steps are repeated, result in the formation of a green body part (also known as a green body) in the powder bed. The binder fluid can include a binder that holds the build materials of the green body part together. The green body part can then be exposed to electromagnetic radiation and / or heat to sinter the build materials in the green body part to form a 3D part.

[0014] Examples of the 3D printing kits, methods, and systems disclosed herein utilize a single binder fluid or a multi-fluid binder. One of the fluids in the single binder fluid or multi-fluid binder contains polymer particles to produce patterned green blank parts from metal powder build materials and also utilizes heat to activate the polymer particles and create a solidified green blank part. The solidified green blank part can be removed from the metal powder build material that has not been patterned with the binder fluid without adversely affecting the structure of the solidified green blank part. The removed solidified green blank part can then be de-binded to produce a gray blank part that is at least substantially free of polymer, and the at least substantially free of polymer gray blank part can then be sintered to form the final 3D printed part / object.

[0015] The single binder fluid may further comprise metal or metal precursor particles, which may comprise metal nanoparticles, metal oxide nanoparticles, metal oxide nanoparticles and a reducing agent, or a combination thereof, to produce patterned green blank parts from metal powder build materials and also utilize heat to form metallic connections and create solidified green blank parts. The solidified green blank parts can be removed from the metal powder build material that was not patterned with the binder fluid without adversely affecting the structure of the solidified green blank parts. The removed solidified green blank parts can then be degreased to produce at least substantially polymer-free grey blank parts, and the at least substantially polymer-free grey blank parts can then be sintered to form the final 3D-printed part / object.

[0016] The multi-fluid binder may comprise a binder fluid that is separate from a fluid containing polymer particles. This separate binder fluid may comprise metal or metal precursor particles, which may comprise metal nanoparticles, metal oxide nanoparticles, metal oxide nanoparticles and a reducing agent, or a combination thereof, to produce patterned green blank parts from metal powder build materials and also utilize heat to form metal connections and create solidified green blank parts. The solidified green blank parts may be removed from the metal powder build material that was not patterned with the binder fluid without adversely affecting the structure of the solidified green blank parts. The removed solidified green blank parts may then be degreased to produce at least substantially polymer-free grey blank parts, and the at least substantially polymer-free grey blank parts may then undergo sintering to form the final 3D printed part / object.

[0017] As used herein, the terms "bound metal object" or "patterned green-blank part" refer to an intermediate part having a shape representative of a final 3D-printed part and comprising a metal powder build material patterned with a binder fluid. In the patterned green-blank part, the metal powder build material particles may or may not be weakly bound together by one or more components of the binder fluid and / or by one or more attractive forces between the metal powder build material particles and the binder fluid. In some cases, the mechanical strength of the patterned green-blank part is such that it cannot be handled or removed from the build material platform. Furthermore, it is understood that any metal powder build material that is not patterned with the binder fluid is not considered part of the patterned green-blank part, even if it is adjacent to or surrounds the patterned green-blank part.

[0018] As used herein, the term "cured green blank part" refers to a patterned green blank part that has been exposed to a heating process that induces melting of polymer particles and / or induces melting of metal or metal precursor particles. This heating process may also facilitate evaporation of the liquid component of one or more binder fluids. Cured green blank parts have greater mechanical strength than patterned green blank parts and, in some cases, can be moved or removed from the build material platform.

[0019] It is to be understood that the term "green blank" when referring to a patterned green blank part or a cured green blank part does not connote a color, but rather indicates that the part has not yet been fully processed and / or finished.

[0020] As used herein, the term "at least substantially polymer-free grey green component" refers to a cured green green component that has been exposed to a heating process that induces thermal decomposition of polymer particles, thereby at least partially removing the polymer particles. In some cases, the volatile organic components of, or generated by, the thermally decomposed polymer particles are completely removed, and a minimal amount of non-volatile residue from the thermally decomposed polymer particles may remain (e.g., <1% by weight of the initial binder). In other cases, the thermally decomposed polymer particles (including any products and residues) are completely removed. In other words, an "at least substantially polymer-free grey green component" refers to an intermediate component having a shape representative of the final 3D printed part and comprising metal powder build material held together by i) weak sintering (i.e., a low level of necking between particles that enables the part shape to be maintained), or ii) residual small amounts of cured polymer particles, or iii) capillary and / or van der Waals forces resulting from the removal of the polymer particles, and / or iv) any combination of i, ii, and / or iii.

[0021] It is to be understood that the term "grey blank" when referring to a grey blank component that is at least substantially free of polymer does not connote color, but rather indicates that the component has not yet been fully processed.

[0022] The at least substantially polymer-free grey green part may have a porosity similar to or greater than that of the cured green green part (due to the removal of polymer particles), but this porosity is at least substantially eliminated during conversion to a 3D printed part.

[0023] As used herein, the terms "three-dimensional object," "3D object," "3D printed part," "3D part," or "metal part" refer to a finished sintered part.

[0024] In the examples disclosed herein, when a single adhesive fluid or a multi-fluid adhesive is applied to a layer of metal powder build material, the liquid vehicle in the one or more fluids is capable of wetting the build material, and the polymer particles and / or metal or metal precursor particles are capable of penetrating into the microscopic pores of the layer (i.e., the spaces between the particles of the metal powder build material).

[0025] 3D printing kit

[0026] Multi-fluid set

[0027] In examples disclosed herein, a multi-fluid kit for 3D printing is described. The multi-fluid kit may include a first fluid comprising a first liquid vehicle comprising metal or metal precursor particles; and a second fluid comprising a second liquid vehicle comprising latex polymer particles dispersed therein, wherein the latex polymer particles have an average particle size of about 10 nm to about 300 nm, and wherein the metal or metal precursor particles comprise metal nanoparticles, metal oxide nanoparticles, metal oxide nanoparticles and a reducing agent, or a combination thereof.

[0028] The latex polymer particles may be composed of (A) a copolymerizable surfactant selected from polyoxyethylene alkylphenyl ether ammonium sulfate, polyoxyethylene alkyl ether sodium sulfate, polyoxyethylene styrenated phenyl ether ammonium sulfate or a mixture thereof, and (B) 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, isopropyl acrylate, Bornyl ester, tetrahydrofurfuryl acrylate, 2-phenoxyethyl methacrylate, benzyl methacrylate, benzyl acrylate, ethoxylated nonylphenol methacrylate, ethoxylated behenyl methacrylate, polypropylene glycol monoacrylate, isobornyl methacrylate, cyclohexyl methacrylate, cyclohexyl acrylate, tert-butyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, alkoxylated tetrahydrofurfuryl acrylate, isodecyl acrylate, isobornyl methacrylate, isobornyl acrylate, acetoacetoxyethyl methacrylate or a combination thereof.

[0029] The latex polymer particles can include 2-phenoxyethyl methacrylate, cyclohexyl methacrylate, cyclohexyl acrylate, methacrylic acid, or a combination thereof.

[0030] The latex polymer particles can comprise styrene, methyl methacrylate, butyl acrylate, methacrylic acid, or combinations thereof.

[0031] The latex polymer particles may be present in the second fluid in an amount from about 5 wt % to about 40 wt % based on the total weight of the second fluid.

[0032] The first liquid vehicle and the second liquid vehicle may each contain water in an amount of about 45 wt % to about 75 wt %, based on the total weight of the first liquid vehicle and the second liquid vehicle, respectively.

[0033] The metal nanoparticles may comprise nickel, silver, gold, copper, platinum, or a combination thereof.

[0034] The metal oxide nanoparticles may comprise oxides of iron, nickel, silver, gold, copper, platinum, cobalt, manganese, vanadium, molybdenum, or combinations thereof.

[0035] The reducing agent may be selected from an aldehyde, a hydrazide, a hydrazine, ascorbic acid, a reducing sugar, or a combination thereof.

[0036] Single Fluid Kit

[0037] In examples disclosed herein, a kit for three-dimensional printing is described. The kit may include a powdered metal build material; and a binding fluid comprising a liquid vehicle, metal or metal precursor particles dispersed in the liquid vehicle, and latex polymer particles, wherein the latex polymer particles have an average particle size of about 10 nm to about 300 nm, and wherein the metal or metal precursor particles comprise metal nanoparticles, metal oxide nanoparticles, metal oxide nanoparticles and a reducing agent, or a combination thereof.

[0038] The latex polymer particles may be composed of (A) a copolymerizable surfactant selected from polyoxyethylene alkylphenyl ether ammonium sulfate, polyoxyethylene alkyl ether sodium sulfate, polyoxyethylene styrenated phenyl ether ammonium sulfate or a mixture thereof, and (B) 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, isopropyl acrylate, Bornyl ester, tetrahydrofurfuryl acrylate, 2-phenoxyethyl methacrylate, benzyl methacrylate, benzyl acrylate, ethoxylated nonylphenol methacrylate, ethoxylated behenyl methacrylate, polypropylene glycol monoacrylate, isobornyl methacrylate, cyclohexyl methacrylate, cyclohexyl acrylate, tert-butyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, alkoxylated tetrahydrofurfuryl acrylate, isodecyl acrylate, isobornyl methacrylate, isobornyl acrylate, acetoacetoxyethyl methacrylate or a combination thereof.

[0039] The latex polymer particles can include 2-phenoxyethyl methacrylate, cyclohexyl methacrylate, cyclohexyl acrylate, methacrylic acid, or a combination thereof.

[0040] The latex polymer particles can comprise styrene, methyl methacrylate, butyl acrylate, methacrylic acid, or combinations thereof.

[0041] The powdered metal build material may include steel, bronze, titanium and its alloys, aluminum and its alloys, nickel and its alloys, cobalt and its alloys, iron and its alloys, nickel-cobalt alloys, gold and its alloys, silver and its alloys, platinum and its alloys, copper and its alloys, or combinations thereof.

[0042] The metal nanoparticles may comprise nickel, silver, gold, copper, platinum, or a combination thereof.

[0043] The metal oxide nanoparticles may comprise oxides of iron, nickel, silver, gold, copper, platinum, cobalt, manganese, vanadium, molybdenum, or combinations thereof.

[0044] The reducing agent is selected from the group consisting of aldehydes, hydrazides, hydrazines, ascorbic acid, reducing sugars, or combinations thereof.

[0045] The latex polymer particles may be present in the bonding fluid in an amount from about 5 wt % to about 40 wt % based on the total weight of the bonding fluid.

[0046] 3D printing methods

[0047] Multi-fluid method

[0048] In an example disclosed herein, a method for printing a three-dimensional object is described. The method may include (i) depositing a metal powder build material in a powder bed; (ii) selectively applying a first fluid and a second fluid to the metal powder build material in the powder bed based on a model of the three-dimensional object, wherein the first fluid comprises a first liquid vehicle comprising metal or metal precursor particles, wherein the metal or metal precursor particles comprise metal nanoparticles, metal oxide nanoparticles, metal oxide nanoparticles and a reducing agent, or a combination thereof, and the second fluid comprises a second liquid vehicle comprising latex polymer particles dispersed therein, wherein the latex polymer particles have an average particle size of about 10 nm to about 300 nm; (iii) repeating (i) and (ii) at least once to form the three-dimensional object; and (iv) heating the powder bed to a temperature of up to about 200°C.

[0049] The method may further comprise (v) removing the three-dimensional object from the powder bed and heating the three-dimensional object to a temperature of up to about 500°C.

[0050] The heating to a temperature of up to about 500° C. can include removing at least about 95% by weight of the latex polymer particles by thermally decomposing the latex polymer particles and initiating bonding of the metal powder particles to the metal or metal precursor particles.

[0051] The latex polymer particles may be present in the second fluid in an amount from about 1 wt % to about 50 wt % based on the total weight of the second fluid.

[0052] The method may further include (vi) heating the three-dimensional object to a sintering temperature greater than about 500° C. in a sintering furnace.

[0053] Single-fluid method

[0054] In an example disclosed herein, a method for printing a three-dimensional object is disclosed. The method may include (i) depositing a metal powder build material in a powder bed; (ii) selectively applying a binding fluid to the metal powder build material in the powder bed based on a model of the three-dimensional object, wherein the binding fluid comprises a liquid vehicle, metal or metal precursor particles dispersed in the liquid vehicle, and latex polymer particles, wherein the metal or metal precursor particles comprise metal nanoparticles, metal oxide nanoparticles, metal oxide nanoparticles and a reducing agent, or a combination thereof, and wherein the latex polymer particles have an average particle size of about 10 nm to about 300 nm; (iii) repeating (i) and (ii) at least once to form the three-dimensional object; and (iv) heating the powder bed to a temperature of up to about 200°C.

[0055] The method may further comprise (v) heating the three-dimensional object in the powder bed to a temperature of up to about 500°C.

[0056] The method may further include (vi) heating the three-dimensional object to a sintering temperature greater than about 500°C.

[0057] Methods using a single fluid kit may include applying a powdered build material and then applying a binding fluid to a 3D printing bed.

[0058] 3D printing system

[0059] In an example disclosed herein, a printing system for printing a three-dimensional object is disclosed. The printing system may include a supply of one or more binding fluids; a supply of metal powdered build material; a build material dispenser; a fluid applicator for selectively dispensing the binding fluid; a heat source; a controller; and a non-transitory computer-readable medium storing computer-executable instructions for causing the controller to print the three-dimensional object by iteratively forming at least one layer of the powdered metal build material with the selectively applied binding fluid using the build material dispenser and the fluid applicator, and heating the selectively applied binding fluid to the powdered metal build material using the heat source to form the three-dimensional object.

[0060] The powdered metal build material may include steel, bronze, titanium and its alloys, aluminum and its alloys, nickel and its alloys, cobalt and its alloys, iron and its alloys, nickel-cobalt alloys, gold and its alloys, silver and its alloys, platinum and its alloys, copper and its alloys, or combinations thereof.

[0061] In some examples, the first fluid may include a first liquid vehicle containing metal or metal precursor particles. In some examples, the second fluid may include a second liquid vehicle containing latex polymer particles dispersed therein, wherein the latex polymer particles have an average particle size of about 10 nm to about 300 nm.

[0062] In the multi-fluid example, the metal or metal precursor particles can comprise metal nanoparticles, metal oxide nanoparticles, metal oxide nanoparticles and a reducing agent, or a combination thereof.

[0063] In the single-fluid example, the metal or metal precursor particles can include metal nanoparticles, metal oxide nanoparticles, metal oxide nanoparticles and a reducing agent, or a combination thereof.

[0064] Now refer to Figure 1 , depicting an example of a 3D printing system 10. It is understood that the 3D printing system 10 may include additional components and that some of the components described herein may be removed and / or modified. Additionally, Figure 1 The components of 3D printing system 10 depicted in FIG. 1 may not be drawn to scale, and thus, 3D printing system 10 may have different sizes and / or configurations than those shown therein.

[0065] Three-dimensional (3D) printing system 10 generally includes a supply 14 of metal powder build material 16; a build material dispenser 18; a supply of binder fluid 36; an inkjet applicator 24 for selectively dispensing binder fluid 36 ( Figure 2C ); at least one heat source 32; controller 28; and a non-transitory computer readable medium having computer executable instructions stored thereon to cause controller 28 to: iteratively form a plurality of layers 34 of metal powder build material 16 using build material dispenser 18 and inkjet applicator 24 ( Figure 2B ), which layer is applied by build material dispenser 18 and has received binder fluid 36, thereby creating patterned green blank part 42 ( Figure 2E ), and heating the patterned green blank part 42 using the at least one heat source 32 to create a solidified green blank part 42′. In some examples, the solidified green blank part 42′ is heated to create an at least substantially polymer-free gray blank part 48. The at least substantially polymer-free gray blank part 48 or the solidified green blank part 42′ is heated to a sintering temperature to form a metal part 50.

[0066] like Figure 1As shown in FIG, printing system 10 includes a build area platform 12, a build material supply 14 containing metal powder build material particles 16, and a build material dispenser 18.

[0067] Build area platform 12 (sometimes referred to herein as a powder bed) receives metal powder build material 16 from a build material supply 14. Build area platform 12 may be integrated with printing system 10 or may be a component that can be separately inserted into printing system 10. For example, build area platform 12 may be a module that can be supplied independently of printing system 10. The illustrated build area platform 12 is also an example and may be replaced by another support member, such as a platen, a build / print bed, a glass plate, or another build surface.

[0068] The build area platform 12 can be moved in the direction indicated by arrow 20, such as along the z-axis, to deliver metal powder build material 16 to the platform 12, or to a previously formed layer of metal powder build material 16 (see FIG. Figure 2D In one example, when metal powder build material particles 16 are to be delivered, build area platform 12 may be programmed to advance sufficiently (e.g., downward) so that build material dispenser 18 can push metal powder build material particles 16 onto platform 12 to form layer 34 of metal powder build material 16 thereon (see, e.g., Figure 2A and 2B ). The build area platform 12 can also be returned to its original position, for example when a new part is to be built.

[0069] Build material supply 14 can be a container, bed, or other surface that holds metal powder build material particles 16 between build material dispenser 18 and build area platform 12. In some examples, build material supply 14 can include a surface onto which metal powder build material particles 16 can be supplied, for example, from a build material source (not shown) located above build material supply 14. Examples of build material sources can include hoppers, screw conveyors, and the like. Additionally or alternatively, build material supply 14 can include a mechanism (e.g., a delivery piston) to provide (e.g., move) metal powder build material particles 16 from a storage location to a location to be spread onto build area platform 12 or onto a previously formed layer of metal powder build material 16.

[0070] Build material dispenser 18 can move above build material supply 14 and across build area platform 12 in the direction indicated by arrow 22, e.g., along the y-axis, to spread a layer of metal powder build material 16 on build area platform 12. Build material dispenser 18 can also return to a position adjacent to build material supply 14 after spreading metal powder build material 16. Build material dispenser 18 can be a blade (e.g., a scraper), a roller, a combination of a roller and a blade, and / or any other device capable of spreading metal powder build material particles 16 on build area platform 12. For example, build material dispenser 18 can be a counter-rotating roller.

[0071] Metal powder build material 16 can be any particulate metal material. In one example, metal powder build material 16 can be a powder. In another example, metal powder build material 16 can have a property of sintering into a continuous body to form metal part 50 when heated to a sintering temperature (e.g., a temperature of about 850° C. to about 1400° C.) (see, e.g., Figure 2F By "continuum" is meant that the metal powder build material particles are fused together to form a single component having little or no porosity and having sufficient mechanical strength to meet the requirements of the desired final metal component 50.

[0072] While an exemplary sintering temperature range is provided, it is understood that this temperature may vary, depending in part on the composition and phase or phases of metal powder build material 16 .

[0073] Applicator 24 can scan across build area platform 12 in the direction indicated by arrow 26, for example, along the y-axis. Applicator 24 can be, for example, an inkjet applicator, such as a thermal inkjet printhead, a piezoelectric printhead, or a combination thereof, and can extend the width of build area platform 12. Although applicator 24 is Figure 1 1. Although shown as a single applicator in FIG. 1, it is understood that applicator 24 may include multiple applicators spanning the width of build area platform 12. In some examples, a single or multiple applicators 24 may be used to apply a single-fluid adhesive or a multi-fluid adhesive.

[0074] In addition, applicator 24 can be arranged in multiple print bars. Applicator 24 can also scan along the x-axis, for example in a configuration where applicator 24 does not span the width of build area platform 12, so that applicator 24 can deposit binder fluid 36 over a large area of ​​the layer of metal powder build material 16. Applicator 24 can therefore be attached to a movable XY stage or translation carriage (neither shown) that moves applicator 24 in close proximity to build area platform 12 to deposit binder fluid 36 in predetermined areas of the layer of metal powder build material 16 formed on build area platform 12 according to one or more methods disclosed herein. Applicator 24 can include multiple nozzles (not shown) through which binder fluid 36 is sprayed.

[0075] As used herein, "adhesive fluid 36" refers to either a single-fluid adhesive or a multi-fluid adhesive.

[0076] As discussed above, a multi-fluid binder kit for three-dimensional printing comprises a first fluid comprising a first liquid vehicle comprising metal or metal precursor particles; and a second fluid comprising a second liquid vehicle comprising latex polymer particles dispersed therein, wherein the latex polymer particles have an average particle size of about 10 nm to about 300 nm, and wherein the metal or metal precursor particles comprise metal nanoparticles, metal oxide nanoparticles, metal oxide nanoparticles and a reducing agent, or a combination thereof.

[0077] As discussed above, a single-fluid adhesive for three-dimensional printing comprises a binding fluid comprising a liquid vehicle, metal or metal precursor particles dispersed in the liquid vehicle, and latex polymer particles, wherein the latex polymer particles have an average particle size of about 10 nm to about 300 nm, and wherein the metal or metal precursor particles comprise metal nanoparticles, metal oxide nanoparticles, metal oxide nanoparticles and a reducing agent, or a combination thereof.

[0078] The applicator 24 can deliver droplets of the adhesive fluid 36 at a resolution of approximately 300 dots per inch (DPI) to approximately 1200 DPI. In other examples, the applicator 24 can deliver droplets of the adhesive fluid 36 at a higher or lower resolution. The droplet velocity can be approximately 2 m / s to approximately 24 m / s and the jetting frequency can be approximately 1 kHz to approximately 100 kHz. In one example, each droplet can be approximately 10 picoliters (pl) per droplet, although higher or lower droplet sizes are contemplated. For example, the droplet size can be approximately 1 pl to approximately 400 pl. In some examples, the applicator 24 is capable of delivering droplets of the adhesive fluid 36 of varying sizes.

[0079] Each of the aforementioned physical elements may be tangibly connected to a controller 28 of printing system 10. Controller 28 may control the operation of build area platform 12, build material supply 14, build material dispenser 18, and applicator 24. As one example, controller 28 may control actuators (not shown) to control various operations of the components of 3D printing system 10. Controller 28 may be a computing device, a semiconductor-based microprocessor, a central processing unit (CPU), an application-specific integrated circuit (ASIC), and / or another hardware device. Although not shown, controller 28 may be connected to the components of 3D printing system 10 via communication lines.

[0080] Controller 28 manipulates and converts data, which may be represented as physical (electronic) quantities within the printer's registers and memory, in order to control the physical elements to create 3D part 50. Thus, controller 28 is depicted as being in communication with data storage 30. Data storage 30 may include data regarding 3D part 50 to be printed by 3D printing system 10. Data for selectively delivering metal powder build material particles 16 and / or binder fluid 36 may be derived from a model of 3D part 50 to be formed. For example, this data may include the positions at which applicator 24 deposits binder fluid 36 on each layer of metal powder build material particles 16. In one example, controller 28 may use the data to control applicator 24 to selectively apply binder fluid 36. Data storage 30 may also include machine-readable instructions (stored on a non-transitory computer-readable medium) that enable controller 28 to control the amount of metal powder build material particles 16 supplied by build material supply 14, the movement of build area platform 12, the movement of build material dispenser 18, and the movement of applicator 24.

[0081] like Figure 1 As shown in FIG, printing system 10 may further include a heater 32. In some examples, heater 32 comprises a conventional furnace or oven, a microwave, or a device capable of mixed heating (i.e., conventional heating and microwave heating). This type of heater 32 may be used to heat the entire build material cake 44 after printing is complete (see FIG. Figure 2E ), or for heating the cured green blank part 42', or for heating the at least substantially polymer-free grey blank part 48 after the cured green blank part 42' is removed from the build material cake 44 (see Figure 2F In some examples, patterning may be performed in printing system 10 and then build material platform 12 with patterned green blank part 42 thereon may be detached from system 10 and placed in heater 32 for various heating stages.

[0082] In other examples, heater 32 may be a conductive heater or a radiant heater (e.g., an infrared lamp) integrated into system 10. These other types of heaters 32 may be positioned below build area platform 12 (e.g., conductive heating from below platform 12), or may be positioned above build area platform 12 (e.g., radiant heating of the surface of the build material layer). Combinations of these types of heating may also be used. These other types of heaters 32 may be used throughout the 3D printing process. In still other examples, heater 32 may be a radiant heat source (e.g., a curing lamp) positioned to heat each layer 34 after adhesive fluid 36 has been applied (see Figure 2C ).exist Figure 1 In the example shown in , the heater 32 is attached to the side of the applicator 24, which allows printing and heating to be achieved in a single pass.

[0083] It is to be understood that in this context, e.g. Figures 2A-2F The corresponding text discusses in detail Figure 3 An example of method 300 is shown in FIG.

[0084] Now refer to Figures 2A to 2F , depicting an example of a 3D printing method. Before executing the method or as part of the method, which may be method 300, controller 28 may access data stored in data storage 30 regarding 3D part 50 to be printed. Controller 28 may determine the number of layers of metal powder build material particles 16 to be formed and the locations at which applicator 24 deposits binder fluid 36 on each layer.

[0085] like Figure 2A and 2B As shown in , the 3D printing method may include applying a metal powder build material 16. Figure 2A In the embodiment of the present invention, build material supply 14 can supply metal powder build material particles 16 to a certain position so that they are ready to be spread onto build area platform 12. Figure 2B In the embodiment, the building material dispenser 18 can spread the supplied metal powder building material particles 16 onto the building area platform 12. The controller 28 can execute the control building material supply instruction to control the building material supplier 14 to appropriately place the metal powder building material particles 16, and can execute the control spreader instruction to control the building material dispenser 18 to spread the supplied metal powder building material particles 16 on the building area platform 12 to form a layer 34 of metal powder building material particles 16 thereon. Figure 2B As shown in FIG, a layer 34 of metal powder build material particles 16 has been applied.

[0086] Layer 34 has a substantially uniform thickness across build area platform 12. In one example, layer 34 has a thickness of about 30 μm to about 300 μm, although thinner or thicker layers may be used. For example, layer 34 may have a thickness of about 20 μm to about 500 μm. For finer feature definition, the layer thickness may be as low as about 2× the particle size (e.g., Figure 2B ). In some examples, the layer thickness can be approximately 1.2x (i.e., 1.2 times) the particle size.

[0087] Now refer to Figure 2C The method continues by selectively applying a bonding fluid (also referred to as a binder fluid) 36 to portions 38 of metal powder build material 16. Binder fluid 36 may be dispensed by one or more applicators 24. Applicators 24 may be thermal inkjet printheads or piezoelectric printheads, and may enable selective application of binder fluid 36 using related printing technologies. Thus, selective application of binder fluid 36 may be achieved through thermal inkjet printing or piezoelectric inkjet printing.

[0088] Controller 28 can execute instructions to control applicator 24 (e.g., in the direction indicated by arrow 26) to deposit binder fluid 36 onto one or more predetermined portions 38 of metal powder build material 16 that are to become part of patterned green blank part 42 and that are to be ultimately sintered to form 3D part 50. Applicator 24 can be programmed to receive commands from controller 28 and deposit binder fluid 36 according to a cross-sectional pattern of a layer of 3D part 50 to be formed. As used herein, a cross-section of a layer of 3D part 50 to be formed refers to a cross-section parallel to the surface of build area platform 12. Figure 2C In the example shown in , applicator 24 selectively applies binder fluid 36 to those portions 38 of layer 34 that are to be fused to form the first layer of 3D part 50. As an example, if the shape of the 3D part to be formed resembles a cube or a cylinder, binder fluid 36 is deposited in a square pattern or a circular pattern (top view) on at least a portion of layer 34 of metal powder build material particles 16, respectively. Figure 2C In the example shown in FIG. 4 , adhesive fluid 36 is deposited in a square pattern on portions 38 of layer 34 and not on portions 40 .

[0089] Applicator 24 (although shown as one, multiple applicators may be present) may apply binder fluid 36 or a first fluid and a second fluid (not shown) simultaneously, continuously, or sequentially. When the first and second fluids are applied simultaneously, the components of the fluids may be mixed in situ on metal powder build material 16. When the first and second fluids are applied continuously or sequentially, the two fluids may not be limited to mixing in situ on metal powder build material 16. The sequential application of the first and second fluids may be performed in any order, depending on the desired final properties of the final part.

[0090] When binder fluid 36 is selectively applied to one or more desired portions 38, the polymer particles and metal or metal precursor particles (present in binder fluid 36) infiltrate the inter-particle spaces between metal powder build material particles 16. The volume of binder fluid 36 applied per unit of metal powder build material 16 in patterned portion 38 may be sufficient to fill a substantial portion, or a majority, of the pores present within the thickness of portion 38 of layer 34.

[0091] It is understood that portions 40 of metal powder build material 16 that do not have binder fluid 36 applied thereto also do not have polymer particles and metal or metal precursor particles introduced therein. Therefore, these portions do not become part of the ultimately formed patterned green blank part 42.

[0092] Repeatable Figures 2A to 2C The process shown in FIG is used to iteratively build up several patterned layers and form a patterned green blank part 42 (see Figure 2E ).

[0093] Figure 2D The diagram illustrates the initial formation of a second layer of metal powder build material 16 on layer 34 patterned with binder fluid 36. Figure 2D , after depositing binder fluid 36 onto one or more predetermined portions 38 of layer 34 of metal powder build material 16, controller 28 may execute instructions to move build area platform 12 a relatively short distance in the direction indicated by arrow 20. In other words, build area platform 12 may be lowered to enable the formation of the next layer of metal powder build material 16. For example, build material platform 12 may be lowered a distance equal to the height of layer 34. Furthermore, after build area platform 12 is lowered, controller 28 may control build material supply 14 to supply additional metal powder build material 16 (e.g., via operation of an elevator, auger, etc.) and control build material dispenser 18 to form another layer of metal powder build material 16 with the additional metal powder build material 16 above the previously formed layer 34. The newly formed layer may be patterned with binder fluid 36.

[0094] Back to Figure 2C In another example of this method, after applying binder fluid 36 to layer 34 and before forming another layer, layer 34 may be exposed to heat using heater 32. Heater 32 may be used for layer-by-layer heating and / or for heating intermediate components. Heating to form a solidified green blank component may be performed at an activation temperature that activates (or solidifies) the polymer particles in binder fluid 36 but does not melt or sinter metal powder build material 16. Heating to form a solidified green blank component may further be performed at a curing temperature that forms metallic bonds between the metal or metal precursor particles in binder fluid 36.

[0095] In some examples, heater 32 may be a photon fusion source, such as a xenon (Xe) strobe lamp.

[0096] In some examples, the at least one energy source can be a continuous wave discharge lamp containing xenon, argon, neon, krypton, sodium vapor, metal halide, or mercury vapor. In another example, heater 32 can be an array of pulsed lasers, continuous wave lasers, light-emitting diode (LED) lasers, or a combination thereof. In this example, the array can produce a uniformly dispersed light beam. In yet another example, heater 32 can be a flash discharge lamp containing xenon or krypton. In yet another example, heater 32 can be a tungsten-halogen continuous wave lamp. In yet another example, heater 32 can be a synchrotron radiation source emitting light with a wavelength greater than 200 nm.

[0097] Heater 32 is capable of emitting sufficient energy to fuse metal powder build material 16 by rapidly sintering polymer particles and metal or metal precursor particles. When heater 32 is a single pulse light source, heater 32 is capable of delivering about 0.5 J to about 100 J / cm 2 The amount of energy that heater 32 can deliver can be less than 70 J / cm when heater 32 is a multi-pulse light source. 2 And when the heater 32 is a continuous wave light source, it can be greater than 50 J / cm 2 .

[0098] The activation temperature and the sintering temperature are not capable of melting or sintering metal powder build material 16 .

[0099] In one example, the activation temperature is near the glass transition temperature of the polymer particles. Additional examples of suitable activation temperatures are provided below. In one example, the sintering temperature can be from about 80°C to about 250°C, or from about 90°C to about 240°C, or from about 100°C to about 230°C.

[0100] In some instances, you can repeat Figures 2A to 2C The process shown in FIG (including the heating of layer 34) is iteratively built up several solidified layers (one layer at a time) to produce a solidified green blank part 42'. The solidified green blank part 42' can then be exposed to a reference Figure 2F In some examples, instead of heating layer by layer to activation and sintering temperatures, a cake of build material or intermediate component 44 is heated to activation and sintering temperatures.

[0101] Repeatedly forming and patterning new layers (without curing each layer) results in the formation of Figure 2E , which includes patterned green blank part 42 residing within unpatterned portions 40 of layers 34 of metal powder build material 16. Patterned green blank part 42 is the volume of build material cake 44 that is filled with metal powder build material 16 and binder fluid 36 within the inter-particle spaces. The remainder of build material cake 44 is comprised of unpatterned metal powder build material 16.

[0102] like Figure 2E As shown in FIG, a cake of build material 44 can be exposed to heat or radiation as indicated by arrow 46 to generate heat. The applied heat can be sufficient to activate and fuse particles in the binder fluid 36 in the patterned green blank part 42 and produce a stabilized and solidified green blank part 42'. In one example, a heat source 32 can be used to apply heat to the cake of build material 44. Figure 2EIn the example shown in FIG, build material cake 44 can remain on build area platform 12 while being heated by heat source 32. In another example, build area platform 12, with build material cake 44 thereon, can be detached from applicator 24 and placed in heat source 32.

[0103] The activation / curing temperature may depend in part on one or more of the following: the T of the polymer particles; g , the melt viscosity of the polymer particles, and / or whether and what type of coalescing solvent is used. In one example, heating to form the solidified green blank part 42' can be performed at a temperature that activates (or cures) the binder fluid 36 but does not sinter the metal powder build material 16 or thermally degrade the polymer particles of the binder fluid 36. In one example, the activation temperature is approximately the minimum film forming temperature (MFFT) or glass transition temperature of the bulk material of the polymer particles of the binder fluid 36 and below the thermal decomposition temperature of the polymer particles (i.e., below the temperature threshold at which thermal decomposition occurs). For most suitable latex-based polymer particles, the upper limit of the activation / curing temperature is approximately 250°C to approximately 270°C. Above this temperature threshold, the polymer particles chemically degrade into volatile species and exit the patterned green blank part 42, thereby ceasing to perform their function. In other examples, the binder fluid 36 activation temperature can be higher than the MFFT or glass transition temperature of the polymer particles. As an example, the binder fluid activation temperature can be approximately 20°C to approximately 200°C. As another example, the adhesive fluid activation temperature may be from about 100° C. to about 200° C. As yet another example, the adhesive fluid activation temperature may be from about 80° C. to about 200° C. As yet another example, the adhesive fluid activation temperature may be about 90° C.

[0104] The length of time that heat 46 is applied and the rate at which patterned green blank part 42 is heated may depend on, for example, one or more of the following: characteristics of heat or radiation source 32, characteristics of the polymer particles, characteristics of the metal or metal precursor particles, characteristics of metal powder build material 16 (e.g., metal type, particle size, or combinations thereof), and / or characteristics of 3D part 50 (e.g., wall thickness).

[0105] The patterned green blank part 42 may be heated at the binder fluid activation temperature for an activation and sintering time period of approximately 1 minute to approximately 360 minutes. In one example, the activation / curing time period is 30 minutes. In another example, the activation and sintering time period may be approximately 2 minutes to approximately 240 minutes. The patterned green blank part 42 may be heated to the binder fluid activation and sintering temperature at a rate of approximately 1°C / minute to approximately 10°C / minute, although slower or faster heating rates are contemplated. The heating rate may depend in part on one or more of the following: the binder fluid 36 used, the dimensions (i.e., thickness and / or area (across the xy plane)) of the layer 34 of the metal powder build material 16, and / or the characteristics of the 3D part 50 (e.g., dimensions, wall thickness, or a combination thereof). In one example, the patterned green blank part 42 is heated to the binder fluid activation and sintering temperature at a rate of approximately 2.25°C / minute.

[0106] Heating to near the MFFT, or glass transition temperature, of the polymer particles causes the polymer particles to coalesce into a continuous polymer phase between the metal powder build material particles 16 of the patterned green blank part 42. As mentioned above, the coalescing solvent (when included in the binder fluid 36) plasticizes the polymer particles and enhances the coalescence of the polymer particles. This continuous polymer phase can act as a heat-activated adhesive between the metal powder build material particles 16 to form a stabilized, solidified green blank part 42'.

[0107] Heating to form a solidified green blank part may further be performed at a sintering temperature capable of forming a metallic bond between the metal or metal precursor particles in the binder fluid 36. In one example, the sintering temperature may be from about 100° C. to about 300° C., or from about 90° C. to about 240° C., or from about 200° C. to about 300° C. The metallic bond acts as an adhesive between the metal powder build material particles 16 to form a stabilized solidified green blank part 42′.

[0108] In some examples, one of the continuous polymer phase or the metal links acts as a binder between the metal powder build material particles 16 to form the stabilized solidified green blank part 42'. In some examples, both the continuous polymer phase or the metal links act as a binder between the metal powder build material particles 16 to form the stabilized solidified green blank part 42'.

[0109] Heating to form the solidified green blank part 42' may also result in evaporation of a significant portion of the fluid from the patterned green blank part 42. The evaporated fluid may include any adhesive fluid component or the first and second fluid components. Fluid evaporation may result in some densification of the solidified green blank part 42' by capillary action.

[0110] The stabilized cured green blank part 42 ′ exhibits handleable mechanical durability.

[0111] The solidified green blank part 42' can then be removed from the build material cake 44. The solidified green blank part 42' can be removed by any suitable means. In one example, the solidified green blank part 42' can be removed by lifting the solidified green blank part 42' from the unpatterned metal powder build material particles 16. An extraction tool including a piston and a spring can be used.

[0112] When the cured green blank part 42 ′ is removed from the build material cake 44 , the cured green blank part 42 ′ can be removed from the build area platform 12 and placed in a heating mechanism. The heating mechanism can be a heater 32 .

[0113] In some examples, cured green blank part 42' may be cleaned to remove unpatterned metal powder build material particles 16 from its surface. In one example, cured green blank part 42' may be cleaned with a brush and / or an air jet.

[0114] After removing and / or cleaning the cured green blank part 42', as shown in FIG. Figure 2F As shown in FIG, the green blank part 42′ can be heat cured to remove the activated polymer particles (which have coalesced into a continuous polymer phase) to produce an at least substantially polymer-free grey blank part 48. In other words, the green blank part 42′ can be heat cured to remove the continuous polymer phase. However, the metal or metal precursor particles remain in the polymer-free grey blank part 48. Then, as also shown in FIG. Figure 2F As shown in FIG, the at least substantially polymer-free ash green part 48 can be sintered to form the final 3D part 50. The heating for debinding and the heating for sintering occur at two different temperatures, wherein the temperature for debinding is lower than the temperature for sintering. The debinding and sintering heating stages are generally depicted in FIG. Figure 2F wherein heat or radiation for generating heat may be applied by a heat source 32 as indicated by arrow 46 .

[0115] In one example, the thermal decomposition temperature is from about 250°C to about 600°C. In another example, the thermal decomposition temperature is from about 280°C to about 600°C, or to about 500°C. The continuous polymer phase can have a clean thermal decomposition mechanism (e.g., leaving less than 5% by weight of the original binder as a solid residue, and in some cases less than 1% by weight of the original binder as a solid residue). A smaller residual percentage (e.g., approaching 0%) is more desirable. During the debinding stage, the long chains of the continuous polymer phase first break down into shorter molecular fragments, which become a liquid phase with lower viscosity. The capillary pressure generated during the evaporation of this liquid pulls the metal powder build material particles 16 together, resulting in further densification and forming an at least substantially polymer-free soot blank part 48.

[0116] While not being bound by any theory, it is believed that the at least substantially polymer-free soot blank component 48 can maintain its shape due to, for example, one or more of the following: i) low levels of stress experienced by the at least substantially polymer-free soot blank component 48 due to the lack of physical manipulation thereof, ii) low levels of necking occurring between the metal powder build material particles 16 and the polymer particles and metal or metal precursor particles, and / or iii) capillary forces generated by the removal of the continuous polymer phase that push the metal powder build material particles 16 together. Despite the at least substantial removal of the continuous polymer phase and the unsintered metal powder build material particles 16, the at least substantially polymer-free soot blank component 48 can maintain its shape due at least to metallic connections between the metal or metal precursor particles in the interstitial spaces between the powder build material particles 16.

[0117] Heating and sintering are achieved at a sintering temperature sufficient to sinter the remaining metal powder build material particles 16. The sintering temperature depends on the composition of the metal powder build material particles 16. During the heating / sintering process, the at least substantially polymer-free soot blank component 48 can be heated to a temperature between approximately 80% and approximately 99.9% of the melting point, solidus temperature, eutectic temperature, or transfusion temperature of the metal powder build material 16. In another example, the at least substantially polymer-free soot blank component 48 can be heated to a temperature between approximately 90% and approximately 95% of the melting point, solidus temperature, eutectic temperature, or transfusion temperature of the metal powder build material 16. In yet another example, the at least substantially polymer-free soot blank component 48 can be heated to a temperature between approximately 60% and approximately 85% of the melting point, solidus temperature, eutectic temperature, or transfusion temperature of the metal powder build material 16. The sintering heating temperature may also depend on the particle size and the sintering time (i.e., the high temperature exposure time).

[0118] As an example, the sintering temperature can be from about 850°C to about 1400°C. In another example, the sintering temperature is at least 900°C. An example of a sintering temperature for bronze is about 850°C, and an example of a sintering temperature for stainless steel is about 1200°C to 1500°C. While these temperatures are provided as examples of sintering temperatures, it is to be understood that the sintering heating temperature depends on the metal powder build material 16 used. Heating at the appropriate temperature sinters and fuses the metal powder build material particles 16 to form the finished 3D part 50, which is further densified relative to the at least substantially polymer-free gray blank part 48. For example, due to sintering, the density can go from 50% density to over 90%, in some cases very close to 100% of theoretical density.

[0119] During the sintering process, the metal or metal precursor particles (metal nanoparticles) can adjust their shape and diffuse between the metal powder build material particles 16 to form a strong mechanical bond. The sintering process can improve the adhesion between the metal nanoparticles and the metal powder build material particles 16. Sintering can also be used to increase the density of the component. For example, small voids in the polymer-free ash blank component 48 can be filled with diffused metal nanoparticles during the sintering process. Diffusion sintering protocols and reshape sintering protocols are within the knowledge of the skilled person, and useful texts provide guidance and models for such operations, such as Randall German, 1994, Metal Powder Industries Federation, Princeton, NJ.

[0120] The length of time that heat 46 is applied (for debinding and sintering, respectively) and the rate at which parts 42 ′, 48 are heated may depend on, for example, one or more of the following: characteristics of heat or radiation source 32 , characteristics of the polymer particles, characteristics of the metal nanoparticles, characteristics of metal powder build material 16 (e.g., metal type, particle size, or a combination thereof), and / or characteristics of 3D part 50 (e.g., wall thickness).

[0121] The cured green blank part 42' can be heated to the thermal decomposition temperature for a thermal decomposition period of about 10 minutes to about 72 hours. In one example, the thermal decomposition period is 60 minutes. In another example, the thermal decomposition period is 180 minutes. The cured green blank part 42' can be heated to the thermal decomposition temperature at a rate of about 0.5°C / minute to about 20°C / minute. The heating rate can depend in part on one or more of the following: the amount of continuous polymer phase in the cured green blank part 42', the porosity of the cured green blank part 42', and / or the characteristics of the cured green blank part 42' / 3D part 50 (e.g., dimensions, wall thickness, or a combination thereof).

[0122] The at least substantially polymer-free ash green component 48 can be heated at the sintering temperature for a sintering time period of approximately 20 minutes to approximately 15 hours. In one example, the sintering time period is 240 minutes. In another example, the sintering time period is 360 minutes. The at least substantially polymer-free ash green component 48 can be heated to the sintering temperature at a rate of approximately 1°C / minute to approximately 20°C / minute. In one example, the at least substantially polymer-free ash green component 48 is heated to the sintering temperature at a rate of approximately 10°C / minute to approximately 20°C / minute. A high ramp rate to the sintering temperature may be desirable to produce a more favorable grain structure or microstructure. However, in some cases, a slower ramp rate may be desirable. Thus, in another example, the at least substantially polymer-free ash green component 48 is heated to the sintering temperature at a rate of approximately 1°C / minute to approximately 3°C / minute. In yet another example, the at least substantially polymer-free ash green component 48 is heated to the sintering temperature at a rate of approximately 1.2°C / minute. In yet another example, the at least substantially polymer-free soot component 48 is heated to the sintering temperature at a rate of approximately 2.5°C / minute.

[0123] In an example of the method, the cured green green part 42' is heated to a thermal decomposition temperature for a thermal decomposition period of about 30 minutes to about 72 hours, and the at least substantially polymer-free gray green part 48 is heated to a sintering temperature for a sintering period of about 20 minutes to about 15 hours. In another example of the method, the cured green green part 42' is heated to the thermal decomposition temperature at a rate of about 0.5°C / minute to about 10°C / minute, and the at least substantially polymer-free gray green part 48 is heated to the sintering temperature at a rate of about 1°C / minute to about 20°C / minute.

[0124] In some examples of the method, heat 46 (for both debinding and sintering) is applied in an environment containing an inert gas, a low-reactivity gas, a reducing gas, or a combination thereof. In other words, heating the solidified green green part 42' to a thermal decomposition temperature and heating the at least substantially polymer-free grey green part 48 to a sintering temperature is performed in an environment containing an inert gas, a low-reactivity gas, a reducing gas, or a combination thereof. Debinding can be performed in an environment containing an inert gas, a low-reactivity gas, and / or a reducing gas to thermally decompose the continuous polymer phase rather than undergoing alternative reactions that would prevent the production of the at least substantially polymer-free grey green part 48 and / or to prevent oxidation of the metal powder build material 16. Sintering can be performed in an environment containing an inert gas, a low-reactivity gas, and / or a reducing gas to sinter the metal powder build material 16 rather than undergoing alternative reactions (e.g., oxidation reactions) that would prevent the production of the metal 3D part 50. Examples of inert gases include argon, helium, or other similar noble inert gases. Examples of low-reactivity gases include nitrogen, and examples of reducing gases include hydrogen, carbon monoxide, or mixtures thereof.

[0125] In other examples of the method, heat 46 is applied (each for debinding (i.e., heating the solidified green body 42′ to a thermal decomposition temperature) and sintering (i.e., heating the at least substantially polymer-free grey body part to a sintering temperature)) in an environment that contains carbon in addition to an inert gas, a low-reactivity gas, a reducing gas, or a combination thereof. Debinding and sintering can be accomplished in an environment containing carbon to reduce the oxygen partial pressure in the environment and further prevent oxidation of metal powder build material 16 during the debinding and sintering processes. One example of carbon that can be placed in the heated environment includes graphite rods. In other examples, a graphite furnace can be used.

[0126] In still other examples of the method, heat 46 is applied (for debinding and sintering, respectively) in a low pressure or vacuum environment. Debinding and sintering can be achieved in a low pressure or vacuum environment to thermally decompose the continuous polymer phase and / or prevent oxidation of the metal powder build material 16. In addition, sintering at low pressure or under vacuum can achieve more complete or faster pore collapse, and therefore higher density parts. However, when the metal powder build material 16 (e.g., Cr) is capable of evaporating under such conditions, a vacuum cannot be used during the sintering process. In one example, the low pressure environment is at about 1E-5 Torr (1×10 -5 Torr) to a pressure of about 10 Torr.

[0127] Although not shown, Figure 2E and 2F The operations depicted in can be automated, and the controller 28 can control these operations.

[0128] exist Figure 3 In the flowchart, a method (300) for printing a three-dimensional object is shown, which includes: (i) depositing a metal powder build material in a powder bed (310); (ii) selectively applying a first fluid and a second fluid (320) to the metal powder build material in the powder bed based on a model of the three-dimensional object, wherein the first fluid comprises a first liquid vehicle comprising metal or metal precursor particles, wherein the metal or metal precursor particles comprise metal nanoparticles, metal oxide nanoparticles, metal oxide nanoparticles and a first reducing agent, a metal salt, a metal salt and a second reducing agent, or a combination thereof, and the second fluid comprises a second liquid vehicle comprising latex polymer particles dispersed therein, wherein the latex polymer particles have an average particle size of about 10 nm to about 300 nm; (iii) repeating (i) and (ii) at least once to form a three-dimensional object (330); and (iv) heating the powder bed to a temperature of up to about 200°C (340).

[0129] Metal powder building materials

[0130] In one example, the metal powder building material 16 is a single-phase metal material composed of one element. In this example, the sintering temperature may be lower than the melting point of the single element.

[0131] In another example, the metal powder build material 16 is composed of two or more elements and may be in the form of a single-phase metal alloy or a multi-phase metal alloy. In these other examples, melting generally occurs within a certain temperature range. For some single-phase metal alloys, melting begins just above the solidus temperature (where melting is initiated) and is not complete until the liquidus temperature (the temperature at which all the solid is melted) is exceeded. For other single-phase metal alloys, melting begins just above the transfusion temperature. The transfusion temperature is defined as the point at which a single-phase solid transforms into a two-phase solid-liquid mixture, where the solid above the transfusion temperature has a different phase than the solid below the transfusion temperature. When the metal powder build material 16 is composed of two or more phases (such as a multi-phase alloy made of two or more elements), melting generally begins above the eutectic temperature or transfusion temperature. The eutectic temperature is defined as the temperature at which a single-phase liquid completely solidifies into a two-phase solid. Typically, melting of a single-phase metal alloy or a multi-phase metal alloy begins just above the solidus temperature, eutectic temperature, or transfusion temperature and is not complete until the liquidus temperature is exceeded. In some instances, sintering can occur below the solidus temperature, transfusion temperature or eutectic temperature. In other instances, sintering occurs above the solidus temperature, transfusion temperature or eutectic temperature. The sintering above the solidus temperature is called super solidus sintering, and when using larger building material particles and / or to achieve high density, this technology may be ideal. In an example, the building material composition can be selected to make at least 40 volume % of the metal powder building material consist of one or more phases having a melting point higher than the required sintering temperature. It will be appreciated that the sintering temperature may be high enough to provide sufficient energy to allow atomic migration between adjacent particles.

[0132] A single element or an alloy may be used as the metal powder build material 16. Some examples of metal powder build materials 16 include steel, stainless steel, bronze, titanium (Ti) and its alloys, aluminum (Al) and its alloys, nickel (Ni) and its alloys, cobalt (Co) and its alloys, iron (Fe) and its alloys, nickel-cobalt (NiCo) alloys, gold (Au) and its alloys, silver (Ag) and its alloys, platinum (Pt) and its alloys, and copper (Cu) and its alloys. Some specific examples include AlSi10Mg, 2xxx series aluminum, 4xxx series aluminum, CoCr MP1, CoCrSP2, Maraging Steel MS1, Hastelloy C, Hastelloy X, Nickel Alloy HX, Inconel IN625, Inconel IN718, SS GP1, SS 17-4PH, SS 316L, Ti6Al4V, and Ti-6Al-4V ELI7. While several exemplary alloys have been provided, it is understood that other alloy build materials may be used, such as PbSn brazing alloys.

[0133] Any metal powder build material 16 that is in powder form at the outset of one or more of the 3D printing methods disclosed herein can be used. Thus, the melting point, solidus temperature, eutectic temperature, and / or transfusion temperature of the metal powder build material 16 can be higher than the temperature of the environment in which the patterning portion of the 3D printing method is performed (e.g., higher than 40°C). In some examples, the metal powder build material 16 can have a melting point of approximately 850°C to approximately 3500°C. In other examples, the metal powder build material 16 can be an alloy having a range of melting points. The alloy can include metals or combinations thereof with melting points as low as -39°C (e.g., mercury), 30°C (e.g., gallium), or 157°C (indium).

[0134] The metal powder build material 16 can be composed of particles of similar size or particles of different sizes. In the example shown herein ( Figure 1 and Figures 2A-2F ), the metal powder building material 16 includes particles of similar size. The term "size" as used herein with respect to the metal powder building material 16 refers to the diameter of a substantially spherical particle (i.e., a spherical or nearly spherical particle with a sphericity > 0.84), or the average diameter of a non-spherical particle (i.e., the average of multiple diameters across the particle). Substantially spherical particles of this size have good flowability and can be spread relatively easily. As an example, the average particle size of the particles of the metal powder building material 16 can be from about 1 μm to about 200 μm. As another example, the average particle size of the particles of the metal powder building material 16 is from about 10 μm to about 150 μm. As yet another example, the average particle size of the particles of the metal powder building material 16 is from 15 μm to about 100 μm.

[0135] Adhesive fluid or first fluid and second fluid

[0136] like Figure 1 As shown in FIG, the printing system 10 also includes an applicator 24, which may contain an adhesive fluid 36 disclosed herein (shown in FIG. Figure 2C In some examples, the adhesive fluid 36 (also referred to herein as the adhesive fluid 36) can be created, stored, and applied as two separate fluids: a first fluid and a second fluid. As discussed above, the first fluid can include a first liquid vehicle containing metal or metal precursor particles, and the second fluid can include a second liquid vehicle containing latex polymer particles dispersed therein. The latex polymer particles have an average particle size of approximately 10 nm to approximately 300 nm, and the metal or metal precursor particles include metal nanoparticles, metal oxide nanoparticles, metal oxide nanoparticles and a reducing agent, or a combination thereof.

[0137] Although not shown Figure 2C , but binder fluid 36 may be a single fluid or two separate fluids—a first fluid and a second fluid—that are sprayed onto metal powder build material 16 from one or more applicators 24 (only one applicator is shown).

[0138] Binder fluid 36 includes at least a liquid vehicle, polymer particles, and metal or metal precursor particles. In some cases, binder fluid 36 consists of the liquid vehicle, polymer particles, and metal or metal precursor particles, without any other components.

[0139] In some examples, the bonding fluid (also referred to herein as adhesive fluid) has a pH of about 6.5 to about 9, or less than about 8.5, or less than about 8, or less than about 7.5, or at least about 6.8, or at least about 6.9, or at least about 7, or at least about 7.5.

[0140] In some examples, the viscosity of the adhesive fluid composition is less than about 10 cps, or less than about 15 cps, or less than about 14 cps, or less than about 13 cps, or less than about 12 cps, or less than about 11 cps, or less than about 10 cps, or less than about 9 cps, or less than about 8 cps, or less than about 7 cps, or less than about 6 cps, or less than about 5 cps, or less than about 4 cps, or less than about 3 cps.

[0141] In some examples, the first fluid can include a first liquid vehicle containing metal or metal precursor particles and no other components, and the second fluid can include a second liquid vehicle containing latex polymer particles dispersed therein and no other components.

[0142] All of the liquid vehicles described herein—in the bonding fluid 36, in the first fluid, and in the second fluid—can all be the same or similar. The pH of the first and second fluids can be between about 6.5 and about 9, or less than about 8.5, or less than about 8, or less than about 7.5, or at least about 6.8, or at least about 6.9, or at least about 7, or at least about 7.5. The viscosity of the first and second fluids can be less than about 10 cps, or less than about 15 cps, or less than about 14 cps, or less than about 13 cps, or less than about 12 cps, or less than about 11 cps, or less than about 10 cps, or less than about 9 cps, or less than about 8 cps, or less than about 7 cps, or less than about 6 cps, or less than about 5 cps, or less than about 4 cps, or less than about 3 cps.

[0143] polymer particles

[0144] In the examples disclosed herein, the polymer particles can be dispersed in a liquid vehicle.The polymer particles can have any morphology - for example, single phase, or core-shell, partially occluded, multilobal, or a combination thereof.

[0145] In one example, polymer particles can be made from two different copolymer compositions. These can be completely separate "core-shell" polymers, partially embedded mixtures, or intimately mixed as a "polymer solution." In another example, the polymer particle morphology can resemble a raspberry, with a hydrophobic core surrounded by a large number of smaller hydrophilic particles attached to the core. In yet another example, a polymer particle can include two, three, four, or more relatively large particle "leaves" surrounding a smaller polymer core.

[0146] The polymer particles can be any latex polymer (i.e., a polymer capable of being dispersed in an aqueous medium) that can be jetted via inkjet printing (e.g., thermal inkjet printing or piezoelectric inkjet printing). In some examples disclosed herein, the polymer particles are heteropolymers or copolymers. The heteropolymers can contain a more hydrophobic component and a more hydrophilic component. In these examples, the hydrophilic component allows the particles to be dispersed in binder fluid 36, while the hydrophobic component can coalesce upon exposure to heat to temporarily bond metal powder build material particles 16 together to form a cured green blank part 42′.

[0147] Can be used to form low T hydrophobic components gExamples of monomers include C4 to C8 alkyl acrylates or methacrylates, styrene, substituted methylstyrenes, polyol acrylates or methacrylates, vinyl monomers, vinyl esters, and the like. Some specific examples include methyl methacrylate, butyl acrylate, butyl methacrylate, hexyl acrylate, hexyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, hydroxyethyl acrylate, dodecyl acrylate, dodecyl methacrylate, octadecyl acrylate, octadecyl methacrylate, isobornyl acrylate, isobornyl methacrylate, stearyl methacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetrahydrofurfuryl acrylate, alkoxylated tetrahydrofurfuryl acrylate, 2-phenoxyethyl methacrylate, benzyl acrylate, ethoxylated nonylphenol methyl acrylate, acrylate, cyclohexyl methacrylate, trimethylcyclohexyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, tridecyl methacrylate, isodecyl acrylate, dimethyl maleate, dioctyl maleate, acetoacetoxyethyl methacrylate, diacetone acrylamide, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, divinylbenzene, styrene, methylstyrene (e.g., α-methylstyrene, p-methylstyrene), vinyl chloride, vinylidene chloride, vinylbenzyl chloride, acrylonitrile, methacrylonitrile, N-vinylimidazole, N-vinylcarbazole, N-vinyl-caprolactam, combinations thereof, derivatives thereof, or mixtures thereof.

[0148] Examples of monomers that can be used to form the polymer particles include acrylic acid, methacrylic acid, ethacrylic acid, dimethacrylic acid, maleic anhydride, maleic acid, vinyl sulfonate, cyanoacrylic acid, vinyl acetic acid, allyl acetic acid, ethylidine acetic acid, propylidine acetic acid, crotonic acid, fumaric acid, itaconic acid, sorbic acid, angelic acid, cinnamic acid, styryl acrylic acid, citraconic acid, glutaconic acid, aconitic acid, phenyl acrylic acid, acryloyloxypropionic acid, aconitic acid, phenyl acrylic acid, acryloyloxypropionic acid, vinylbenzene. Formic acid, N-vinylsuccinamic acid, mesaconic acid, methacryloylalanine, acryloylhydroxyglycine, sulfoethyl methacrylic acid, sulfopropyl acrylic acid, styrenesulfonic acid, sulfoethyl acrylic acid, 2-methacryloyloxymethane-1-sulfonic acid, 3-methacryloyloxypropane-1-sulfonic acid, 3-(vinyloxy)propane-1-sulfonic acid, ethylenesulfonic acid, vinylsulfuric acid, 4-vinylphenylsulfuric acid, ethylenephosphonic acid, vinylphosphonic acid, vinylbenzoic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid, combinations thereof, derivatives thereof, or mixtures thereof. High T gOther examples of hydrophilic monomers include acrylamide, methacrylamide, monohydroxylated monomers, monoethoxylated monomers, polyhydroxylated monomers, or polyethoxylated monomers.

[0149] In one example, one or more selected monomers are polymerized to form a polymer, heteropolymer, or copolymer. In some examples, one or more monomers are polymerized with a copolymerizable surfactant. In some examples, the copolymerizable surfactant may be a polyoxyethylene compound. In some examples, the copolymerizable surfactant may be a Hitenol® compound, such as polyoxyethylene alkylphenyl ether ammonium sulfate, polyoxyethylene alkyl ether sodium sulfate, polyoxyethylene styrenated phenyl ether ammonium sulfate, or a mixture thereof. Any suitable polymerization method may be used. The polymer particles may have a particle size that can be ejected via thermal inkjet printing, piezoelectric printing, or continuous inkjet printing. In one example, the particle size of the polymer particles is from about 10 nm to about 300 nm.

[0150] In some examples, the polymer particles have a MFFT or glass transition temperature (T g In other examples, the polymer particles have a MFFT or glass transition temperature (T g ) (i.e., at least 15°C higher than the ambient temperature). As used herein, "ambient temperature" may refer to room temperature (e.g., about 18°C ​​to about 22°C), or to the temperature of the environment in which the 3D printing process is performed. An example of a 3D printing ambient temperature may be about 40°C to about 50°C. The MFFT or glass transition temperature T of the bulk material (e.g., the more hydrophobic portion) of the polymer particle is g It can be from 25° C. to about 125° C. In one example, the MFFT or glass transition temperature T of the bulk material (eg, the more hydrophobic portion) of the polymer particle is g The MFFT or glass transition temperature T of the bulk material is about 40°C or higher. g This can be any temperature that allows the polymer particles to be inkjet printed without becoming too soft at the operating temperature of the printer.

[0151] The polymer particles may have a MFFT or glass transition temperature of about 125° C. to about 200° C. In one example, the polymer particles may have a MFFT or glass transition temperature of about 160° C.

[0152] The polymer particles may have a weight average molecular weight of about 10,000 Mw to about 500,000 Mw. In some examples, the polymer particles have a weight average molecular weight of about 100,000 Mw to about 500,000 Mw. In other examples, the polymer particles have a weight average molecular weight of about 150,000 Mw to 300,000 Mw.

[0153] When each polymer particle contains low T g Hydrophobic components and high T g When the hydrophilic component is present, the polymer particles can be prepared by any suitable method. For example, the polymer particles can be prepared by one of the following methods.

[0154] In one example, by making the high T g Hydrophilic monomers polymerize to form high T g Hydrophilic components and high T g The hydrophilic component is attached to the low T g The polymer particles are prepared by coating the surface of a hydrophobic component.

[0155] In another example, each polymer particle can be formed by making a low T g Hydrophobic monomer and high T g Hydrophilic monomers with low T ratios of 5:95 to 30:70 g Hydrophobic monomer: high T g Hydrophilic monomers are prepared by polymerization. In this example, soft low T g Hydrophobic monomers may dissolve in hard high T g Hydrophilic monomer.

[0156] In yet another example, each polymer particle can be formed by using a low T g The polymerization process starts with a hydrophobic monomer and then a high T g In this example, the polymerization method may result in a higher concentration of high T g Hydrophilic monomers are polymerized at low T g At or near the surface of the hydrophobic component.

[0157] In yet another example, each polymer particle can be formed by using a low T g Hydrophobic monomer and high T g The hydrophilic monomer starts the copolymerization process and then adds additional high T g In this example, the copolymerization method may result in a higher concentration of high T g Hydrophilic monomer copolymerization at low T g At or near the surface of the hydrophobic component.

[0158] The low T used in any of these examples g Hydrophobic monomers and / or high T g The hydrophilic monomers can be (respectively) the low T g Hydrophobic monomers and / or high T g Any of the hydrophilic monomers. In one embodiment, low T gThe hydrophobic monomer is selected from the group consisting of C4 to C8 alkyl acrylate monomers, C4 to C8 alkyl methacrylate monomers, styrene monomers, substituted methylstyrene monomers, vinyl monomers, vinyl ester monomers, and combinations thereof; and high T g The hydrophilic monomer is selected from the group consisting of acidic monomers, unsubstituted amide monomers, alcohol-containing acrylate monomers, alcohol-containing methacrylate monomers, C1 to C2 alkyl acrylate monomers, C1 to C2 alkyl methacrylate monomers, and combinations thereof.

[0159] The resulting polymer particles may exhibit a core-shell structure, a mixed or co-polymeric structure, or some other morphology.

[0160] The polymer particles may be present in the adhesive fluid 36 in an amount of about 2 wt % to about 50 wt %, or about 3 wt % to about 40 wt %, or about 5 wt % to about 30 wt %, or about 10 wt % to about 20 wt %, or about 12 wt % to about 18 wt %, or about 15 wt % (based on the total wt % of the adhesive fluid 36). In another example, the polymer particles may be present in the adhesive fluid 36 in an amount of about 20 vol % to about 40 vol % (based on the total vol % of the adhesive fluid 36). It is believed that these polymer particle loadings provide a balance between an adhesive fluid 36 having jetting reliability and bonding efficiency. In one example, the polymer particles are present in the adhesive fluid in an amount of about 2 wt % to about 30 wt %, and the coalescing solvent is present in the adhesive fluid in an amount of about 0.1 wt % to about 50 wt %.

[0161] In one example, the latex polymer particles have an average particle size of about 10 nm to about 300 nm, or about 50 nm to about 300 nm, or about 100 nm to about 300 nm, or about 110 nm to about 300 nm, about 120 nm to about 300 nm, or about 130 nm to about 300 nm, or about 140 nm to about 300 nm, or about 150 nm to about 300 nm, or about 160 nm to about 290 nm, or about 170 nm to about 300 nm, or about 180 nm to about 2700 nm, or about 190 nm to about 250 nm, or about 190 nm to about 230 nm, or about 190 nm to about 220 nm, or about 190 nm to about 210 nm, or about 200 nm.

[0162] Metal or metal precursor particles

[0163] In some examples, the metal or metal precursor particles can include metal nanoparticles, metal oxide nanoparticles, metal oxide nanoparticles and a reducing agent, or a combination thereof.

[0164] The metal nanoparticles may comprise nickel, silver, gold, copper, platinum, or a combination thereof. The metal oxide nanoparticles may comprise oxides of iron, nickel, silver, gold, copper, platinum, cobalt, manganese, vanadium, molybdenum, or a combination thereof. The reducing agent may be selected from an aldehyde, a hydrazide, hydrazine, ascorbic acid, a reducing sugar, or a combination thereof.

[0165] The metal or metal precursor particles can comprise a variety of shapes, sizes, distributions, and materials. Regardless of the shape, size, distribution, or material used, the particles maintain their shape during application to the metal powder material 16 and during formation of metallic connections between the metal powder material particles 16. The metal or metal precursor particles can be of any shape. The metal or metal precursor particles can be formed by processing. The metal or metal precursor particles can be naturally formed materials. The metal or metal precursor particles can include a variety of different shapes. The metal or metal precursor particles can be selected and / or sorted to have a given geometry. The metal or metal precursor particles can include flakes, sheets, plates, or similar flat, primarily two-dimensional geometric shapes. The metal or metal precursor particles can include rods, spindles, spheres, or blocks. The metal or metal precursor particles can have an average and / or median particle size of less than about 1000 nm, or less than about 500 nm, or less than about 200 nm, or less than about 100 nm, or from about 10 nm to about 100 nm, or from about 1 μm to about 1000 μm, or from about 10 μm to 500 μm, or from about 50 μm to about 200 μm.

[0166] The metal or metal precursor particles used may have a single particle size distribution. They may also include a mixture of multiple particle size distributions. The metal or metal precursor particles may all have similar and / or identical compositions. Alternatively, several different types of metal or metal precursor particles may be combined. For example, multiple types of metal or metal precursor particles may be combined to form an alloy after a secondary heating operation. Alternatively, composition gradients may be formed. For example, areas of a component requiring ductility may have a higher nickel concentration. In contrast, the nickel concentration may be lower near the surface that will contact the skin. Structured / supporting electrodes may be formed. For example, small areas of precious metals such as platinum or gold may be formed within areas of a high-melting-point metal such as titanium. The high-melting-point metal may oxidize in a post-forming process to form an insulator, leaving the precious metal areas to act as electrodes. Because both the metal or metal precursor particles and the deposited metal can be selected and applied with high precision, a variety of heterogeneous materials can be easily formed. Thus, composition gradients in the consolidated component can be created by varying the particles, varying the deposited metal connections, or both.

[0167] In some examples, the metal or metal precursor particles can be formed from a variety of materials, including but not limited to: metals, metal oxides, metal carbides, metal nitrides, ceramics, non-metals, metalloids, semiconductors, polymers (particularly thermosets, but including thermoplastic polymers), minerals, carbon black, graphite, diamond, organic materials, or combinations thereof. The metal or metal precursor particles are stable during the formation of the metallic joint. While this can be achieved in various forms as described below, different materials may be more and / or less suitable for a particular method. Furthermore, the material selection has a significant impact on the properties of the consolidated part and the types of secondary processes that can be used. Clearly, the particles selected will also affect the properties of the final part.

[0168] The metal or metal precursor particles can be formed from a variety of metals. However, the surface of some metals is easily oxidized to form metal oxides. In some examples, it is advantageous to coat the metal or metal precursor particles to prevent or reduce surface oxidation. The coating can be a second metal. For example, iron nanoparticles can be coated with silver to prevent oxidation. The coating can be a polymer. For example, nickel nanoparticles can be coated with polyethylene. The coating can be a suitable organic or inorganic coating that reduces and / or prevents oxidation of the coated metal or metal precursor particles. In some examples, the coating is designed to decompose or volatilize at a temperature below the melting point of the nanoparticles. This can help prevent the coating from inhibiting the bonding between the metal or metal precursor particles and adjacent metal powder building material particles 16. In another example, a reducing agent is provided to the metal oxide coated nanoparticles - as part of the particles, as a coating, or applied separately. The reducing agent is activated to reduce the metal oxide and form a metallic connection.

[0169] The polymer-free ash blank component 48 with metal or metal precursor particles reorganizes within the interstitial spaces of the polymer-free ash blank component 48 to form metallic connections between the metal or metal precursor particles. These metallic connections preferably occupy the spaces between the metal powder build material particles 16 due to the high volume to new surface area ratio these locations provide. However, not every junction needs to be connected to form a solid, consolidated component. There is a random component as to which metal powder build material particles 16 are connected together via metallic connections and which are not. Therefore, there is a certain threshold below which the weight percentage of metal or metal precursor particles does not provide acceptable strength. In some cases, components with lower metal or metal precursor particle loadings may be brittle or easily damaged, even if they are solid. However, because metal or metal precursor particles tend to be more expensive than metal powder build material particles 16, there is a trade-off between mechanical robustness and the percentage of metal or metal precursor particles used as a percentage of the total weight of the component.

[0170] Functional components can be made using a binding fluid composition or first fluid composition having from about 0.1% to about 15% by weight of the final component of metal or metal precursor particles. Higher loadings of metal or metal precursor particles appear to reduce the temperature required to achieve consolidation, resulting in higher density and potentially reducing shrinkage observed during subsequent heating / sintering operations. This is consistent with the model in which the metal or metal precursor particles bind the metal powder build material particles 16 together and fill the gaps between the metal powder build material particles 16.

[0171] solvent

[0172] In some examples, the adhesive fluid 36, the first fluid, and the second fluid each comprise a liquid vehicle, each comprising at least one solvent.

[0173] In some examples, when present with the polymer particles, the solvent acts as a coalescing solvent in the binder fluid 36 and in the second fluid by plasticizing the polymer particles and enhancing their coalescence when exposed to heat. In some examples, the liquid vehicle can consist of the polymer particles and the coalescing solvent (without other components). In these examples, the liquid vehicle consists of the coalescing solvent (without other components), and the coalescing solvent constitutes the balance of the binder fluid 36.

[0174] In some instances, solvent can be lactam, such as 2-pyrrolidone, 1-(2-hydroxyethyl)-2-pyrrolidone or a combination thereof. In other instances, solvent can be glycol ether or glycol ether ester, such as tripropylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, tripropylene glycol mono-n-butyl ether, propylene glycol phenyl ether, dipropylene glycol methyl ether acetate, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, ethylene glycol phenyl ether, diethylene glycol mono-n-butyl ether acetate, ethylene glycol mono-n-butyl ether acetate or a combination thereof. In further instances, solvent can be a water-soluble polyol, such as 2-methyl-1,3-propylene glycol or a combination thereof. In further instances, solvent can be a combination of any of the above-mentioned examples. In still other examples, the solvent is selected from 2-pyrrolidone, 1-(2-hydroxyethyl)-2-pyrrolidone, tripropylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, tripropylene glycol mono-n-butyl ether, propylene glycol phenyl ether, dipropylene glycol methyl ether acetate, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, ethylene glycol phenyl ether, diethylene glycol mono-n-butyl ether acetate, ethylene glycol mono-n-butyl ether acetate, 2-methyl-1,3-propanediol, or a combination thereof.

[0175] The solvent may be present in the liquid vehicle in an amount of about 0.1 wt % to about 50 wt % (based on the total weight of the adhesive fluid, the first fluid, or the second fluid). In some examples, larger or smaller amounts of solvent may be used, depending in part on the jetting architecture of the applicator 24.

[0176] As used herein, "liquid vehicle" may refer to a liquid fluid in which polymer particles and / or metal or metal precursor particles are dispersed. A variety of liquid vehicles may be used, including aqueous and non-aqueous vehicles. In some cases, the liquid vehicle consists primarily of a solvent and no other components. In other instances, the liquid vehicle may include other components, depending in part on the applicator 24 used to dispense the adhesive fluid or the first and second fluids.

[0177] The primary solvent can be water or a non-aqueous solvent (e.g., ethanol, acetone, n-methylpyrrolidone, an aliphatic hydrocarbon, or a combination thereof). In some examples, the liquid vehicle consists of polymer particles and / or metal or metal precursor particles and the primary solvent (without other components). In these examples, the primary solvent constitutes the balance of the liquid vehicle.

[0178] The classes of organic cosolvents that can be used in water-based liquid vehicles include aliphatic alcohols, aromatic alcohols, glycols, glycol ethers, polyglycol ethers, 2-pyrrolidones, caprolactams, formamides, acetamides, glycols, long-chain alcohols, or combinations thereof. Examples of these cosolvents include higher homologs (C6-C8) of aliphatic primary alcohols, aliphatic secondary alcohols, 1,2-alcohols, 1,3-alcohols, 1,5-alcohols, ethylene glycol alkyl ethers, propylene glycol alkyl ethers, and polyethylene glycol alkyl ethers. 12 ), N-alkyl caprolactam, unsubstituted caprolactam, substituted and unsubstituted formamide, substituted and unsubstituted acetamide or a combination thereof.

[0179] Some examples of suitable co-solvents include water-soluble high-boiling point solvents (i.e., humectants) having a boiling point of at least 120°C or higher. Some examples of high-boiling point solvents include 2-pyrrolidone (boiling point of approximately 245°C), 2-methyl-1,3-propanediol (boiling point of approximately 212°C), and combinations thereof. The one or more co-solvents may be present in the liquid vehicle in a total amount of approximately 1 wt % to approximately 50 wt % based on the total weight of the adhesive fluid, the first fluid, or the second fluid, depending on the jetting architecture of the applicator 24.

[0180] In some examples, water is present in the bonding fluid 36, the first fluid, or the second fluid in an amount of at least about 30 wt%, or at least about 35 wt%, or at least about 40 wt%, or at least about 45 wt%, or at least about 50 wt%, or at least about 55 wt%, or at least about 60 wt%, or at least about 65 wt%, or at least about 70 wt%, or at least about 75 wt%, or at least about 80 wt%, or at least about 85 wt%, or at least about 90 wt%, based on the total weight of the bonding fluid 36, or the first fluid, or the second fluid.

[0181] additive

[0182] Examples of other suitable binder fluid or first and second fluid components include one or more cosolvents, one or more surfactants, one or more antimicrobial agents, one or more antifouling agents, one or more viscosity modifiers, one or more pH adjusters, and / or one or more chelating agents. The presence of cosolvents and / or surfactants in the binder fluid or the first and second fluids can help achieve specific wetting behavior for metal powder build material 16.

[0183] One or more surfactants can be used to improve the wetting properties and sprayability of the adhesive fluid or the first and second fluids. Examples of suitable surfactants include self-emulsifiable nonionic wetting agents based on acetylenic diol chemistry (e.g., SURFYNOL® SEF from Air Products and Chemicals, Inc.), nonionic fluorosurfactants (e.g., CAPSTONE® fluorosurfactants, formerly known as ZONYL FSO from DuPont), and combinations thereof. In other examples, the surfactant is an ethoxylated low-foaming wetting agent (e.g., SURFYNOL® 440 or SURFYNOL® CT-111 from Air Products and Chemical Inc.) or an ethoxylated wetting agent and a molecular defoamer (e.g., SURFYNOL® 420 from Air Products and Chemical Inc.). Still other suitable surfactants include nonionic wetting agents and molecular defoamers (e.g., SURFYNOL® 104E from Air Products and Chemical Inc.) or water-soluble nonionic surfactants (e.g., TERGITOL™ TMN-6 or TERGITOL™ 15-S-7 from The Dow Chemical Company). In some instances, it may be desirable to use a surfactant having a hydrophile-lipophile balance (HLB) of less than 10.

[0184] Whether a single surfactant or a combination of surfactants is used, the total amount of one or more surfactants in the adhesive fluid or the first and second fluids can be from about 0.01 wt % to about 10 wt % based on the total weight of the adhesive fluid or the first or second fluid. In another example, the total amount of one or more surfactants in the adhesive fluid 36 can be from about 0.5 wt % to about 2.5 wt % based on the total weight of the adhesive fluid or the first or second fluid.

[0185] The liquid vehicle may also include one or more antimicrobial agents. Suitable antimicrobial agents include biocides and fungicides. Exemplary antimicrobial agents may include NUOSEPT™ (Troy Corp.), UCARCIDE™ (Dow Chemical Co.), ACTICIDE® M20 (Thor), and combinations thereof. Examples of suitable biocides include aqueous solutions of 1,2-benzisothiazolin-3-one (e.g., PROXEL® GXL from Arch Chemicals, Inc.), quaternary ammonium compounds (e.g., Bardac® 2250 and 2280, Barquat® 50-65B, and Carboquat® 250-T, all from Lonza Ltd. Corp.), and aqueous solutions of methylisothiazolone (e.g., Kordek® MLX from Dow Chemical Co.). The biocide or antimicrobial agent may be added in any amount from about 0.05% by weight to about 0.5% by weight relative to the total weight of the adhesive fluid or the first or second fluid (as indicated by regulatory use levels).

[0186] An anti-fouling agent may be included in the binder fluid or the first and second fluids. Fogging refers to the deposition of dried ink (e.g., the binder fluid or the first and second fluids) on the heating element of the thermal inkjet printhead. One or more anti-fouling agents are included to help prevent the accumulation of fouling. Examples of suitable anti-fouling agents include oleyl polyoxyethylene (3) ether phosphate (e.g., available from Croda as CRODAFOS™ O3A or CRODAFOS™ N-3 Acid), or a combination of oleyl polyoxyethylene (3) ether phosphate and a low molecular weight (e.g., <5,000) polyacrylic acid polymer (e.g., available from Lubrizol as CARBOSPERSE™ K-7028 Polyacrylate). Whether a single anti-fouling agent or a combination of anti-fouling agents is used, the total amount of the one or more anti-fouling agents in the binder fluid or the first and second fluids may be from greater than 0.20 wt % to about 0.62 wt % based on the total weight of the binder fluid or the first and second fluids. In one example, oleyl polyoxyethylene (3) ether phosphate is included in an amount of about 0.20 wt % to about 0.60 wt %, and the low molecular weight polyacrylic acid polymer is included in an amount of about 0.005 wt % to about 0.03 wt %.

[0187] Chelating agents, such as EDTA (ethylenediaminetetraacetic acid), may be included to eliminate the deleterious effects of heavy metal impurities, and buffer solutions may be used to control the pH of the adhesive fluid 36. For example, 0.01% to 2% by weight of each of these components may be used. Viscosity modifiers and buffers may also be present, as desired, along with other additives known to those skilled in the art to modify the properties of the adhesive fluid 36. Such additives may be present in amounts ranging from approximately 0.01% to approximately 20% by weight.

[0188] Unless otherwise stated, any feature described above may be combined with any example or any other feature described herein.

[0189] In describing and claiming the examples disclosed herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0190] It will be appreciated that concentration, amount, and other numerical data may be represented or presented in a range format herein. It will be appreciated that such a range format is used only for convenience and brevity, and therefore should be flexibly interpreted as not only including the numerical values ​​clearly enumerated as the endpoints of the range, but also including all independent numerical values ​​or subranges contained within the range, just as each numerical value and subrange are clearly enumerated. For example, a numerical range of "about 1 wt % to about 5 wt %" should be interpreted as not only including the clearly enumerated values ​​of about 1 wt % to about 5 wt %, but also including independent values ​​and subranges within the range shown. Therefore, independent values, such as 2, 3.5, and 4, and subranges, such as 1-3, 2-4, and 3-5, etc., are included in this numerical range. This also applies to the scope of enumerating a single numerical value.

[0191] References throughout this specification to "one example," "some examples," "another example," "an example," etc., mean that a particular element (e.g., feature, structure, and / or characteristic) described in connection with that example is included in at least one example described herein and may or may not be present in other examples. Furthermore, it is understood that elements described for any example may be combined in any suitable manner in the various examples unless the context clearly dictates otherwise.

[0192] Unless otherwise indicated, references herein to the "weight %" of a component refer to the weight of the component as a percentage of the entire composition in which the component is contained. For example, references herein to the "weight %" of, for example, solid materials such as one or more polyurethanes or one or more colorants dispersed in a liquid composition should refer to the weight percentage of these solids in the composition, rather than the amount of solids as a percentage of the total non-volatile solids of the composition.

[0193] Where a standard test is referred to herein, unless otherwise indicated, the version of the test to be referenced is the most recent version at the time this patent application was filed.

[0194] Unless otherwise indicated, all amounts disclosed herein and in the following examples are in weight %.

[0195] To further illustrate the present disclosure, examples are given herein. It is to be understood that these examples are for illustration and should not be construed as limiting the scope of the present disclosure. Example

[0196] Stainless steel build material particles with diameters ranging from 10 μm to 60 μm were layered with a first fluid containing copper oxide nanoparticles (having an average particle size of 100 nm) and a second fluid containing latex polymer particles. The first and second fluid formulations are shown in Tables 1 and 2 below, respectively. The adhesives were deposited separately (one at a time), but at the same deposition rate (a single pen pass deposited the same amount of each adhesive).

[0197] In all cases, whether using a single adhesive fluid or two separate fluids, the total deposited adhesive volume was approximately 50 g / m 2 / Powder layer thickness of approximately 100 µm.

[0198] Table 1 - First Fluid

[0199] Components weight% 2-Methyl-1,3-propanediol 18.0 2-Pyrrolidone 34.0 Tergitol® 15-S-7 0.9 Tergitol® TMN-6 0.9 Capstone® FS-35 0.5 Metalon™ ICI-002HV Jettable Copper Ink 15.0 Acticide® B20 0.15 water margin

[0200] Table 2 – Secondary Fluid

[0201] Components weight% 2-Methyl-1,3-propanediol 9.0 2-Pyrrolidone 16.0 Tergitol® 15-S-7 0.9 Capstone® FS-35 0.5 Acrylic latex 16.0 Acticide® B20 0.15 water margin

[0202] To simplify the experiment, the heating in these examples was performed using a rapidly heating xenon (Xe) discharge lamp system capable of raising the powder temperature to a point where the metal particles could sinter and fuse. The material temperature was raised by precisely controlling the energy and duration of the Xe lamp discharge. The estimated error in the temperature "dialing" in this experiment ranged from approximately 20–30°C to approximately 500°C.

[0203] It is to be understood that the other heaters discussed above may be used in place of the Xe lamp.

[0204] Example 1

[0205] Figure 4 (a)-(d) show the evolution of the second fluid deposited on stainless steel powder and then pulse heating these layers. Figure 4 (a) shows stainless steel powder with an as-deposited second fluid (comprising a latex polymer); Figure 4 (b) shows a peak at 5.2 J / cm 2 Film formation of latex polymer on stainless steel powder after heating at 400°C (approximately 190°C); Figure 4 (c) shows a peak at 7.9 J / cm 2 The bonding state of the latex polymer on the stainless steel powder after further heating at 400°C (about 250°C); and Figure 4 (d) shows 11.2 J / cm 2 Stainless steel powder with some remaining pyrolyzed latex polymer after further heating at 400°C (approximately 300°C). 30 ms pulses were used.

[0206] Figure 4 (a)-(d) show stainless steel metal powder particles onto which the second fluid is printed. 2When heated by the Xe pulse energy (equivalent to temperatures of approximately 300°C-350°C, which initiates pyrolysis of the latex polymer particles), the heating of the particles leads to the initial slow and then rapid disappearance of the binder. In this case, due to the thickness of the stainless steel powder layer and the second fluid layer, the latex polymer is removed once pyrolysis is initiated.

[0207] Example 2

[0208] Figure 5 (a)-(f) show the evolution of the first and second fluids deposited successively. Figure 5 The test samples shown in (a)-(f) were made by depositing the first and second fluids on stainless steel powder in the following order: a layer of first fluid, then a layer of second fluid, repeated 3 times. Figure 5 (a) shows stainless steel powder and the first and second fluids as deposited; Figure 5 (b) shows that the 2 (about 300 ° C) after heating; Figure 5 (c) shows 15.2 J / cm 2 (about 440 ° C) after further heating; Figure 5 (d) shows a peak at 19.7 J / cm 2 (about 650 ° C) after further heating; Figure 5 (e) shows 24.8 J / cm 2 The layer was further heated at 500°C (approximately 800°C) using a 30 ms pulse. Figure 5 (f) Detail showing the bonding pattern in these layers at the highest pulse energy (approximately 800°C). Figure 5 In (f), metallic links (from the molten copper nanoparticles) connecting the stainless steel powder particles can be seen.

[0209] Example 3

[0210] Figure 6 (a) shows (second fluid + first fluid) repeated 3 times. Figure 6 (b) shows (first fluid + second fluid) repeated 3 times. Figure 6 (c) shows the first fluid repeated 3 times, followed by the second fluid repeated 2 times.

[0211] Figure 6 (a)-(c) Comparison of sintering of stainless steel powder particles at temperatures above the pyrolysis temperature of the latex polymer (less than about 300°C). Depositing the second fluid first appears to form large flakes of copper connecting the particles. Whereas, in the case of depositing the first fluid first, these flakes are smaller, break off more frequently, and may provide better adhesion. Without wishing to be bound by theory, Figure 6 (a) and Figure 6 The possible reason for the difference between (b) and (c) is related to the removal of the latex polymer particles via pyrolysis. When a layer of copper oxide (first fluid) is deposited first and then a layer of latex polymer particles (second fluid) is deposited, Figure 6 The difference can be seen in (c). The latex polymer particles can be pyrolyzed when on the top layer ( Figure 6 (c)), while the underlying copper oxide layer is reduced to elemental copper to form well-defined bridges or metallic links connecting adjacent stainless steel particles.

[0212] Figure 7 yes Figure 6 (c) A 2500X magnification shows the stainless steel powder particles bonding together when first depositing several layers of the first fluid on the stainless steel powder. The copper forms a "neck" or metal connection connecting adjacent stainless steel powder particles. In this case, the powder was heated to approximately 450°C.

[0213] While several examples have been described in detail, it will be appreciated that the disclosed examples may be modified. Therefore, the above description should be considered non-limiting.

Claims

1. A multi-fluid kit for three-dimensional printing, comprising: a first fluid comprising a first liquid vehicle comprising metal or metal precursor particles; and a second fluid comprising a second liquid vehicle having latex polymer particles dispersed therein, wherein the latex polymer particles have an average particle size of 10 nm to 300 nm, and The metal or metal precursor particles comprise metal nanoparticles, metal oxide nanoparticles, metal oxide nanoparticles and a reducing agent, or a combination thereof.

2. The multi-fluid kit of claim 1 , wherein the latex polymer particles are composed of (A) a copolymerizable surfactant selected from the group consisting of polyoxyethylene alkylphenyl ether ammonium sulfate, polyoxyethylene alkyl ether sodium sulfate, polyoxyethylene styrenated phenyl ether ammonium sulfate, or mixtures thereof, and (B) 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, acrylic acid The present invention is prepared from propyl carboxylate, propyl methacrylate, octadecyl acrylate, octadecyl methacrylate, stearyl methacrylate, isobornyl acrylate, tetrahydrofurfuryl acrylate, 2-phenoxyethyl methacrylate, benzyl methacrylate, benzyl acrylate, ethoxylated nonylphenol methacrylate, ethoxylated behenyl methacrylate, polypropylene glycol monoacrylate, isobornyl methacrylate, cyclohexyl methacrylate, cyclohexyl acrylate, tert-butyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, alkoxylated tetrahydrofurfuryl acrylate, isodecyl acrylate, isobornyl methacrylate, isobornyl acrylate, acetoacetoxyethyl methacrylate or a combination thereof.

3. The multi-fluid kit of claim 1, wherein the latex polymer particles comprise 2-phenoxyethyl methacrylate, cyclohexyl methacrylate, cyclohexyl acrylate, methacrylic acid, or a combination thereof.

4. The multi-fluid kit of claim 1, wherein the latex polymer particles comprise styrene, methyl methacrylate, butyl acrylate, methacrylic acid, or a combination thereof.

5. The multi-fluid kit of claim 1, wherein the latex polymer particles are present in the second fluid in an amount of 5 wt% to 40 wt% based on the total weight of the second fluid.

6. The multi-fluid set of claim 1, wherein the first liquid vehicle and the second liquid vehicle each comprise water in an amount of 45% to 75% by weight, based on the total weight of the first liquid vehicle and the second liquid vehicle, respectively.

7. The multi-fluid kit of claim 1, wherein the metal nanoparticles comprise nickel, silver, gold, copper, platinum, or a combination thereof.

8. The multi-fluid kit of claim 1, wherein the metal oxide nanoparticles comprise oxides of iron, nickel, silver, gold, copper, platinum, cobalt, manganese, vanadium, molybdenum, or combinations thereof.

9. The multi-fluid kit of claim 1, wherein the reducing agent is selected from the group consisting of aldehydes, hydrazides, hydrazines, ascorbic acid, reducing sugars, or combinations thereof.

10. A method for printing a three-dimensional object, comprising: (i) depositing a metal powder build material in a powder bed; (ii) selectively applying a first fluid and a second fluid to the metal powder build material in the powder bed based on the three-dimensional object model, in The first fluid comprises a first liquid vehicle comprising metal or metal precursor particles, wherein the metal or metal precursor particles comprise metal nanoparticles, metal oxide nanoparticles, metal oxide nanoparticles and a first reducing agent, a metal salt, a metal salt and a second reducing agent, or a combination thereof, and The second fluid comprises a second liquid vehicle having latex polymer particles dispersed therein, wherein the latex polymer particles have an average particle size of 10 nm to 300 nm; (iii) repeating (i) and (ii) at least once to form a three-dimensional object; and (iv) heating the powder bed to a temperature of at most 200°C.

11. The method according to claim 10, further comprising: (v) removing the three-dimensional object from the powder bed and heating the three-dimensional object to a temperature of at most 500°C.

12. The method of claim 11, wherein the heating to a temperature of up to 500°C comprises removing at least 95 weight percent of the latex polymer particles by thermally decomposing the latex polymer particles and initiating bonding of the metal powder particles to the metal or metal precursor particles.

13. The method of claim 10, wherein the latex polymer particles are present in the second fluid in an amount of 1 wt% to 50 wt% based on the total weight of the second fluid.

14. The method according to claim 11, further comprising: (vi) heating the three-dimensional object to a sintering temperature greater than 500° C. in a sintering furnace.

15. The method of claim 14, wherein the three-dimensional object is heated in a sintering furnace to a sintering temperature greater than 800°C.

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