阅读说明：本技术 用于监测增材制造过程中的荧光粘合剂 (Fluorescent adhesive for monitoring additive manufacturing process ) 是由 A·纳塔拉简 T·J·莫克 陈国邦 W·C.·阿尔伯茨 V·布朗伯格 于 2021-05-25 设计创作，主要内容包括：一种制造生坯部件的方法,包括：在工作表面(204)上沉积粉末层(202),以及将包含热塑性粘合剂(216)、荧光材料和粘合剂介质的粘合剂溶液(206)以代表所述生坯部件的层的结构的图案选择性地沉积到所述粉末层(202)中。热塑性粘合剂(216)包含溶解在溶剂介质中的一种或多种聚合物链,所述聚合物链的平均分子量从大于或等于7,000g/mol至小于或等于100,000g/mol。本发明还公开了包含荧光材料的粘合剂溶液和使用该粘合剂溶液粘结在一起的生坯部件。(A method of manufacturing a green part, comprising: depositing a layer of powder (202) on a working surface (204), and selectively depositing a binder solution (206) comprising a thermoplastic binder (216), a fluorescent material, and a binder medium into the layer of powder (202) in a pattern representative of the structure of the layers of the green part. The thermoplastic binder (216) comprises one or more polymer chains dissolved in a solvent medium, the polymer chains having an average molecular weight of from greater than or equal to 7,000g/mol to less than or equal to 100,000 g/mol. Binder solutions comprising fluorescent materials and green parts bonded together using the binder solutions are also disclosed.)

1. A method of manufacturing a green part, comprising:

depositing a powder layer (202) on a work surface (204); and

selectively depositing a binder solution (206) into the powder layer (202) in a pattern representative of the structure of the layers of the green part, the binder solution (206) comprising a thermoplastic binder (216), a fluorescent material, and a binder medium, wherein:

the thermoplastic binder (216) comprises one or more polymer chains dissolved in a solvent medium, the polymer chains having an average molecular weight greater than or equal to 7,000g/mol to less than or equal to 100,000 g/mol.

2. The method according to claim 1, wherein the fluorescent material is encapsulated prior to incorporation into the binder solution (206); or the fluorescent material is encapsulated when mixed into the binder solution (206).

3. The method of any of the preceding claims, wherein the one or more polymer chains in the thermoplastic binder (216) include a first polymer chain comprising a first functional group and a second polymer chain comprising a second functional group different from the first functional group, the first and second functional groups configured to non-covalently couple the first polymer chain with the second polymer chain, the second polymer chain having an average molecular weight greater than or equal to 100g/mol and less than or equal to 10,000 g/mol.

4. The method of claim 1, wherein the fluorescent material comprises an encapsulated aromatic dye.

5. The method of claim 4, wherein the aromatic dye is selected from stilbene dyes, pyrene dyes, coumarin dyes, anthracene dyes, naphthacene dyes, and combinations thereof.

6. The method according to any one of claims 1 to 3, wherein the fluorescent material comprises a chromophore having at least one sulfonate group or triazine group.

7. The method according to any of the preceding claims, wherein the fluorescent material is present in an amount of 0.01 to 5 wt. -%, based on the total weight of the binder solution (206).

8. The method according to any one of the preceding claims, wherein the method further comprises:

exposing a layer of the green part to electromagnetic radiation (302);

curing the layer of green part; and

monitoring an intensity of light emitted by the fluorescent material, wherein the curing is performed until the intensity of light emitted by the fluorescent material is below a predetermined threshold intensity.

9. A green part, wherein the green part comprises powder materials (202) bonded together with at least one binder comprising a fluorescent material.

10. A binder solution (206), wherein the binder solution (206) comprises:

a thermoplastic binder (216) comprising first polymer chains having an average molecular weight of greater than or equal to 7,000g/mol to less than or equal to 100,000 g/mol;

a fluorescent material; and

an adhesive medium.

Technical Field

The present disclosure relates to additive manufacturing, and more particularly, to adhesives for use in additive manufacturing processes.

Background

Additive manufacturing, also known as 3D printing, is a method of building up layers of material to form an object. Binder jetting is an additive manufacturing technique based on the use of a binder to bind powder particles to form a three-dimensional object. In particular, a binder is ejected from a printhead onto successive layers of powder in a build volume (build volume), where the powder layers and binder bond to each other to form a three-dimensional object. In some applications, the printing component is suitable for end use. In other applications, subsequent processing, such as removing the binder and sintering the powder, may be required to transform the printed three-dimensional object into a finished part.

The presence of too much or too little adhesive in the printed part can affect the quality of the final part. For example, if too little binder is applied to the powder layer (such as may be caused by clogging of the nozzles of the print head), the powder may not bond sufficiently and a portion of the layer may be removed when the part is de-powdered. As another example, if too much adhesive is applied, or if the adhesive does not cure at the expected rate, the part may shift or dusting before the part has sufficient strength, which may result in fracture or deformation of the part. In addition, applying too much adhesive can lead to bleed-out and lead to incorrect print geometries. However, conventional binders do not provide sufficient visual contrast to enable reliable optical observation of the amount of binder deposited into the powder bed, geometric fidelity, and degree of cure.

Therefore, there is a need for alternative binder solutions that are capable of monitoring an additive manufacturing process.

Disclosure of Invention

Various embodiments disclosed herein address these needs by providing an adhesive solution comprising an attachable thermoplastic adhesive, a fluorescent material, and an adhesive medium. In various embodiments, the fluorescent material is encapsulated prior to addition to the binder solution or by one or more other components in the binder solution to protect the fluorescent material from quenching by the materials in the powder bed. Thus, the binder solution fluoresces in response to exposure to electromagnetic radiation, enabling the amount of binder solution present to be monitored using an optical system. Other features and advantages will be described in more detail below.

According to a first aspect disclosed herein, a method of manufacturing a green part comprises: depositing a layer of powder on a work surface; and selectively depositing a binder solution comprising a thermoplastic binder, a fluorescent material, and a binder medium into the powder layer in a pattern representative of the structure of the layer of the green part. The thermoplastic binder comprises one or more polymer chains dissolved in a solvent medium, said polymer chains having an average molecular weight of from greater than or equal to 7,000g/mol to less than or equal to 100,000 g/mol.

According to a second aspect disclosed herein, a method of manufacturing a green component comprises a method according to the first aspect, wherein the fluorescent material is encapsulated prior to incorporation into the binder solution.

According to a third aspect disclosed herein, a method of manufacturing a green component comprises a method according to the first or second aspect, wherein the fluorescent material is encapsulated when mixed into the binder solution.

According to a fourth aspect disclosed herein, a method of manufacturing a green part comprises the method according to any one of the preceding aspects, wherein the first polymer chain comprises one or more polymer species selected from: polyvinyl alcohol (PVA), polyamide, polyacrylamide (PAAm), polyvinyl pyrrolidone (PVP), polyacrylic acid (PAA), polymethacrylic acid (PmAA), Polymethylmethacrylate (PMMA), polyvinylmethylether-maleic anhydride (PVME-MA), Polystyrene (PS), polyethylene oxide, polyethylene glycol (PEG), derivatives thereof, and combinations thereof.

According to a fifth aspect disclosed herein, a method of manufacturing a green part comprises the method according to any one of the preceding aspects, wherein the one or more polymer chains in the thermoplastic binder comprise a first polymer chain comprising a first functional group and a second polymer chain comprising a second functional group different from the first functional group, the first and second functional groups being configured to non-covalently couple the first polymer chain with the second polymer chain, the second polymer chain having an average molecular weight greater than or equal to 100g/mol and less than or equal to 10,000 g/mol.

According to a sixth aspect disclosed herein, a method of manufacturing a green part comprises the method according to any one of the preceding aspects, wherein the fluorescent material comprises an encapsulated aromatic dye.

According to a seventh aspect disclosed herein, a method of manufacturing a green part comprises a method according to the sixth aspect, wherein the aromatic dye is selected from the group consisting of stilbene dyes, pyrene dyes, coumarin dyes, anthracene dyes, tetracene dyes and combinations thereof.

According to an eighth aspect disclosed herein, a method of manufacturing a green part comprises the method according to any one of the preceding aspects, wherein the fluorescent material comprises a chromophore having at least one sulfonate or triazine group.

According to a ninth aspect disclosed herein, a method of manufacturing a green part comprises a method according to the eighth aspect, wherein the chromophore comprises two, three or four sulphonate groups.

According to a tenth aspect disclosed herein, a method of manufacturing a green part comprises a method according to the eighth aspect, wherein the chromophore is a stilbene-based chromophore.

According to an eleventh aspect disclosed herein, a method of manufacturing a green component comprises the method according to any one of the preceding aspects, wherein the binder solution is an aqueous binder solution.

According to a twelfth aspect disclosed herein, a method of manufacturing a green part comprises the method according to any one of the preceding aspects, wherein the encapsulated fluorescent material is present in an amount of 0.01 wt% to 5 wt%, based on the total weight of the binder solution.

According to a thirteenth aspect disclosed herein, a method of manufacturing a green part comprises the method of any one of the preceding aspects, wherein the encapsulated fluorescent material is present in an amount of 0.1 to 1 wt. -%, based on the total weight of the binder solution.

According to a fourteenth aspect disclosed herein, a method of manufacturing a green component comprises the method according to any one of the preceding aspects, the method further comprising: exposing the layer of the green part to electromagnetic radiation; curing the layer of green part; and monitoring the intensity of light emitted by the fluorescent material, wherein the curing is performed until the intensity of light emitted by the fluorescent material is below a predetermined threshold intensity.

According to a fifteenth aspect disclosed herein, a method of manufacturing a green part comprises the method according to the fourteenth aspect, wherein the electromagnetic radiation is Ultraviolet (UV) radiation.

According to a sixteenth aspect disclosed herein, a method of manufacturing a green component comprises the method according to the fifteenth aspect, wherein the UV radiation has a wavelength of greater than or equal to 340nm to less than or equal to 600 nm.

According to a seventeenth aspect disclosed herein, a method of manufacturing a green component comprises the method according to the fifteenth aspect, wherein the UV radiation has a wavelength of greater than or equal to 340nm to less than or equal to 400 nm.

According to an eighteenth aspect disclosed herein, a method of manufacturing a green component comprises the method according to any one of the preceding aspects, wherein the powder comprises a metal powder.

According to a nineteenth aspect disclosed herein, a green part includes powder materials bonded together with at least one binder comprising a fluorescent material.

According to a twentieth aspect of the present disclosure, an adhesive solution comprises a thermoplastic adhesive comprising first polymer chains having an average molecular weight of from greater than or equal to 7,000g/mol to less than or equal to 100,000 g/mol; a fluorescent material; and an adhesive medium.

Additional features and advantages of the embodiments disclosed herein will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the disclosed embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description and the following detailed description present embodiments that are intended to provide an overview or framework for understanding the nature and character of the claimed embodiments. The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the disclosure and, together with the description, serve to explain the principles and operations of the disclosure.

Drawings

FIG. 1 is a flow diagram of an exemplary method of manufacturing a part by additive manufacturing using an aqueous binder solution comprising a thermoplastic binder, according to one or more embodiments shown and described herein;

FIG. 2 is a block diagram of an embodiment of an additive manufacturing apparatus for manufacturing a component according to the method of FIG. 1; and

fig. 3 schematically depicts an Ultraviolet (UV) light sensor for monitoring the additive manufacturing process according to fig. 1.

Detailed Description

Reference will now be made in detail to the preferred embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Ranges may be expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

Directional terms used herein, such as upper, lower, right, left, front, rear, top, bottom, refer only to the illustrated drawings and are not meant to be absolutely oriented.

As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a" or "an" component includes aspects having more than two such components, unless the context clearly dictates otherwise.

As used herein, the term "thermoplastic adhesive" refers to an adhesive comprising one or more polymer chains having functional groups that can interact with each other via weak non-covalent forces (e.g., interactions, bonds) to connect or couple each respective thermoplastic polymer chain to each other.

As used herein, "non-covalent coupling" refers to a first functional group and a second functional group interacting with each other through weak non-covalent forces (e.g., interactions or bonds) to connect or couple chains of thermoplastic polymers. As used herein, the term "weak non-covalent forces" is intended to mean hydrogen bonds, ionic bonds, van der waals forces, and the like.

As discussed herein, the parameter "viscosity" of the adhesive solution is measured using a rheometer according to ASTM E3116.

As used herein, the terms "green metal component" and "green component" refer to a printed component that has not been heat treated to remove the chemical binder. As used herein, the terms "brown metal blank" and "brown blank" refer to a printed part that has been heat treated to remove at least a portion of the chemical bonding agent. As used herein, "metal part" refers to a part having a metal material. Although various embodiments are described in the context of metal components, the binder solutions described herein may be applicable to a wide variety of 3D printed components, including but not limited to polymeric and ceramic components.

As used herein, the term "debinding" refers to heating the green part above a first temperature such that the thermoplastic binder thermally decomposes to small oligomers and at least a portion of the thermoplastic binder is removed, thereby forming a brown blank.

As used herein, the term "sintering" refers to heating the brown blank above a second temperature to remove the remaining portion of the thermoplastic binder (e.g., oligomeric residues and pyrolysis byproducts formed during debinding) and consolidate the particles of the powder layer, thereby forming a consolidated component.

As discussed herein, the parameters "green strength" and "brown blank strength" of a part are measured using a three-point flexural strength test according to ASTM B312-14.

As used herein, unless otherwise specified, the term "water" includes deionized water, distilled water, and tap water. In embodiments, the water is ASTM D1193 type IV water or better.

In many binder-jet additive manufacturing processes, chemical binders (e.g., polymeric binders) are used to bond powder layers to one another to form a three-dimensional object. The chemical binder may be, for example, a polymeric binder that is selectively deposited onto the powder bed in a pattern representative of the layers of the fabricated part. However, conventional chemical binders do not readily enable visual monitoring of the selective deposition of the chemical binder, or allow monitoring of the removal of the chemical binder, for example during curing. Furthermore, conventional chemical binders cannot readily identify or locate the finished green part within the powder bed.

Thus, various embodiments described herein provide an adhesive solution comprising a connectable thermoplastic adhesive, a fluorescent material, and an adhesive medium. The fluorescent material is encapsulated in an encapsulating material prior to or at the time of addition to the binder medium such that the fluorescent material luminesces in response to exposure to electromagnetic radiation when deposited onto the powder bed. Such embodiments enable monitoring of various aspects of the additive manufacturing process, including, for example, monitoring the amount and/or location of binder solution deposited on the powder bed and the degree of cure of green parts formed using the binder solution. These and additional advantages will be described in more detail below.

As described above, in various embodiments, the binder solution includes a thermoplastic binder, a fluorescent material, and a binder medium. In embodiments, the fluorescent material is encapsulated such that when it is deposited into the powder layer and exposed to electromagnetic radiation, as will be described in more detail below, the fluorescent material emits light that can be sensed and monitored to provide information regarding the amount and/or location of binder solution deposited onto the powder bed, the degree of cure of the green part formed using the binder solution, and the like.

In various embodiments, the binder solution includes one or more fluorescent materials. As used herein, "fluorescent material" refers to a material that emits radiation of another wavelength (typically longer) during exposure to visible or invisible electromagnetic radiation. For example, fluorescent materials may include, but are not limited to, fluorescent dyes and fluorescent pigments.

The fluorescent pigment may include transparent organic plastic or resin particles containing a fluorescent dye molecularly dissolved or solid-solubilized. Such pigments can be prepared, for example, by dissolving fluorescent dye molecules in a liquid form of a thermosetting resin or a thermoplastic resin. The solvent or carrier resin is then hardened by cooling or curing and then crushed or broken to the desired particle size for use as a pigment. In various embodiments, the pigment particles range in size from greater than or equal to 0.1 μm to less than or equal to 1 μm and may have a high affinity for the agglomerates in the vehicle system. For example, the size of the pigment particles may be in the following range: greater than or equal to 0.1 μm to less than or equal to 1.0 μm, greater than or equal to 0.2 μm to less than or equal to 1.0 μm, greater than or equal to 0.3 μm to less than or equal to 1.0 μm, greater than or equal to 0.4 μm to less than or equal to 1.0 μm, greater than or equal to 0.5 μm to less than or equal to 1.0 μm, greater than or equal to 0.6 μm to less than or equal to 1.0 μm, greater than or equal to 0.7 μm to less than or equal to 1.0 μm, greater than or equal to 0.8 μm to less than or equal to 1.0 μm, greater than or equal to 0.9 μm to less than or equal to 1.0 μm, greater than or equal to 0.1 μm to less than or equal to 0.8 μm, greater than or equal to 0.2 μm to less than or equal to 0.8 μm, greater than or equal to 0.3 μm to less than or equal to 0.8 μm, greater than or equal to 0.4 μm to 0.8 μm, greater than or equal to 0.8 μm to 0.0.8 μm, greater than or equal to 0.8 μm, greater than or equal to 0.0.0.0.0.0.0.0.0.0.0.0.0.0 μm, Greater than or equal to 0.1 μm to less than or equal to 0.5 μm, greater than or equal to 0.2 μm to less than or equal to 0.5 μm, greater than or equal to 0.3 μm to less than or equal to 0.5 μm, or greater than or equal to 0.4 μm to less than or equal to 0.5 μm, including any and all ranges and subranges therein.

Resins suitable for use as a solvent or carrier for forming the pigment and forming the solid base of the pigment include melamine-formaldehyde, aryl monosulfonamide-aldehydes, and urea or melamine formaldehyde resins and condensation products. Other suitable resins and polymers may include acrylonitrile, polyamides, cellulose, polyvinyl alcohol, methyl cellulose, gum tar, polyvinyl acetate, polyvinyl chloride, polyesters, acetals, or combinations thereof. Other resins or polymers may be used provided that the fluorescent dye of the pigment is soluble therein.

When included in the binder solution, the fluorescent pigment is present in the binder solution in an amount of greater than or equal to 0.01 wt% to less than or equal to 5.0 wt%, based on the total weight of the binder solution. For example, the fluorescent pigment may be present in the following amounts: greater than or equal to 0.01 wt% to less than or equal to 5.0 wt%, greater than or equal to 0.05 wt% to less than or equal to 5.0 wt%, greater than or equal to 0.1 wt% to less than or equal to 5.0 wt%, greater than or equal to 1.0 wt% to less than or equal to 5.0 wt%, greater than or equal to 1.5 wt% to less than or equal to 5.0 wt%, greater than or equal to 2.0 wt% to less than or equal to 5.0 wt%, greater than or equal to 3.0 wt% to less than or equal to 5 wt%, greater than or equal to 0.01 wt% to less than or equal to 4.0 wt%, greater than or equal to 0.05 wt% to less than or equal to 4.0 wt%, greater than or equal to 0.1 wt% to less than or equal to 4.0 wt%, greater than or equal to 1.0 wt% to 4.0 wt%, greater than or equal to 4.0 wt% to 0 wt%, greater than or equal to 4.0 wt%, greater than or equal to 0 wt%, greater than 0 wt% to 4.0 wt%, greater than or equal to 4.0.0 wt%, greater than or equal to 0 wt%, greater than or equal to 4.0 wt%, greater than or equal to 0 wt%, greater than or equal to 0.0 wt%, greater than or equal to 4.0 wt%, greater than or equal to 0 wt%, greater than or equal to 4.0 wt%, greater than or equal to 4.0.0 wt%, greater than or equal to 4.0 wt%, greater than or equal to 0 wt%, greater than or equal to 4.0 wt%, less than or equal to 0 wt%, greater than or equal to 4.0 wt%, greater than or equal to 0 wt%, greater than or equal to 4.0 wt%, greater than or equal to 0 wt%, greater than 0 wt%, less than or equal to 4.0 wt%, less than 0 wt%, greater than or equal to 4.0.0 wt%, less than or equal to 0 wt%, greater than or equal to 4.0 wt%, greater than 0 wt%, less than or equal to 0 wt%, less than or equal to 0 wt%, greater than or equal to 4.0.0.0.0.0 wt%, less than or equal to 0 wt%, less than or equal to 4.0 wt%, greater than 4.0 wt%, less than or equal to 5 wt%, less than or equal to 4.0 wt%, less than or equal, greater than or equal to 0.01 wt% to less than or equal to 2.5 wt%, greater than or equal to 0.05 wt% to less than or equal to 2.5 wt%, greater than or equal to 0.1 wt% to less than or equal to 2.5 wt%, greater than or equal to 0.5 wt% to less than or equal to 2.5 wt%, greater than or equal to 1.5 wt% to less than or equal to 2.5 wt%, greater than or equal to 0.01 wt% to less than or equal to 1.0 wt%, greater than or equal to 0.05 wt% to less than or equal to 1.0 wt%, greater than or equal to 0.1 wt% to less than or equal to 1.0 wt%, or greater than or equal to 0.5 wt% to less than or equal to 1.0 wt%, including any and all ranges and subranges therein.

For example, commercially available pigments suitable for use may include, but are not limited to, SPL594N invisible blue and SPL18N Signal Green available from DayGlo^TMAnd A-305E yellow and A-303E red from UMC.

In various embodiments, the fluorescent material may be a fluorescent dye. Fluorescent dyes include aromatic dyes, for example, stilbene dyes, pyrene dyes, coumarin dyes, anthracene dyes, naphthacene dyes, and combinations thereof. In embodiments, such as when the binder medium is water, the fluorescent dye includes a chromophore having at least one sulfonate or triazine group. In some such embodiments, the chromophore comprises two, three, or four sulfonate groups. In embodiments, the chromophore is a stilbene-based chromophore. It is contemplated that different chromophores may be incorporated into the binder solution depending on the particular binder medium used.

When included in the binder solution, the fluorescent dye is present in the binder solution in an amount of greater than or equal to 0.01 wt% to less than or equal to 5.0 wt%, based on the total weight of the binder solution. For example, the fluorescent dye may be present in the following amounts: greater than or equal to 0.01 wt% to less than or equal to 5.0 wt%, greater than or equal to 0.05 wt% to less than or equal to 5.0 wt%, greater than or equal to 0.1 wt% to less than or equal to 5.0 wt%, greater than or equal to 1.0 wt% to less than or equal to 5.0 wt%, greater than or equal to 1.5 wt% to less than or equal to 5.0 wt%, greater than or equal to 2.0 wt% to less than or equal to 5.0 wt%, greater than or equal to 3.0 wt% to less than or equal to 5 wt%, greater than or equal to 0.01 wt% to less than or equal to 4.0 wt%, greater than or equal to 0.05 wt% to less than or equal to 4.0 wt%, greater than or equal to 0.1 wt% to less than or equal to 4.0 wt%, greater than or equal to 1.0 wt% to 4.0 wt%, greater than or equal to 4.0 wt% to 0 wt%, greater than or equal to 4.0 wt%, greater than or equal to 0 wt%, greater than 0 wt% to 4.0 wt%, greater than or equal to 4.0.0 wt%, greater than or equal to 0 wt%, greater than or equal to 4.0 wt%, greater than or equal to 0 wt%, greater than or equal to 0.0 wt%, greater than or equal to 4.0 wt%, greater than or equal to 0 wt%, greater than or equal to 4.0 wt%, greater than or equal to 4.0.0 wt%, greater than or equal to 4.0 wt%, greater than or equal to 0 wt%, greater than or equal to 4.0 wt%, less than or equal to 0 wt%, greater than or equal to 4.0 wt%, greater than or equal to 0 wt%, greater than or equal to 4.0 wt%, greater than or equal to 0 wt%, greater than 0 wt%, less than or equal to 4.0 wt%, less than 0 wt%, greater than or equal to 4.0.0 wt%, less than or equal to 0 wt%, greater than or equal to 4.0 wt%, greater than 0 wt%, less than or equal to 0 wt%, less than or equal to 0 wt%, greater than or equal to 4.0.0.0.0.0 wt%, less than or equal to 0 wt%, less than or equal to 4.0 wt%, greater than 4.0 wt%, less than or equal to 5 wt%, less than or equal to 4.0 wt%, less than or equal, greater than or equal to 0.01 wt% to less than or equal to 2.5 wt%, greater than or equal to 0.05 wt% to less than or equal to 2.5 wt%, greater than or equal to 0.1 wt% to less than or equal to 2.5 wt%, greater than or equal to 0.5 wt% to less than or equal to 2.5 wt%, greater than or equal to 1.5 wt% to less than or equal to 2.5 wt%, greater than or equal to 0.01 wt% to less than or equal to 1.0 wt%, greater than or equal to 0.05 wt% to less than or equal to 1.0 wt%, greater than or equal to 0.1 wt% to less than or equal to 1.0 wt%, or greater than or equal to 0.5 wt% to less than or equal to 1.0 wt%, including any and all ranges and subranges therein.

In various embodiments, the fluorescent dye is encapsulated in an encapsulating material. In embodiments, the encapsulating material may be, for example, a polymer or a polymer matrix, although other encapsulating materials are also contemplated. Without being bound by theory, it is believed that depositing a binder solution comprising unencapsulated fluorescent dye onto a powder bed comprising metal powder may result in fluorescence quenching primarily associated with non-radiative deactivation pathways. However, encapsulation of the fluorescent dye can block this quenching by blocking the formation of non-fluorescent complexes formed by the fluorescent dye and the metal powder, such that the fluorescent dye is able to fluoresce in response to exposure to electromagnetic radiation, even when in contact with the metal powder.

The fluorescent dye may be encapsulated prior to incorporation into the binder solution, or it may be encapsulated when mixed into the binder solution. For example, in some embodiments, the fluorescent dye is encapsulated in the polymer matrix prior to incorporation into the binder solution. In such embodiments, the fluorescent dye can be any of the dyes described above, such as an aromatic dye (e.g., stilbene dye, pyrene dye, coumarin dye, anthracene dye, naphthacene dye, and the like). The polymer matrix may be, for example, but not limited to, polyethylene glycol (PEG) polymers, polyethylene oxide (PEO), polyvinyl alcohol, and the like. For example, a commercially available encapsulated fluorescent dye suitable for use is Invisible Blue UV Reactive Waterdye available from GLO Effex, although other commercially available encapsulated fluorescent dyes are also contemplated.

In other embodiments, the fluorescent dye is encapsulated when mixed into the binder solution. In such embodiments, one or more polymers within the binder solution, such as polymers in the thermoplastic binder, encapsulate the fluorescent dye to prevent the formation of non-fluorescent complexes formed by the fluorescent dye and the metal powder. In such embodiments, the fluorescent dye can be any of the dyes described above, such as an aromatic dye (e.g., stilbene dye, pyrene dye, coumarin dye, anthracene dye, naphthacene dye, and the like). In particular embodiments, the fluorescent dye includes two, three, or four sodium sulfonate functional groups, but may additionally or alternatively include different functional groups depending on the binder medium. In embodiments, the fluorescent dye has a chromophore that includes at least one sulfonate or triazine group. Without being bound by theory, it is believed that the inclusion of such side chain functionality on the chromophore can protect the internal fluorescent chromophore from direct exposure to the metal powder and from quenching. For example, commercially suitable fluorescent dyes that can be added to the binder solution in pure (neat) (e.g., unencapsulated liquid) form include, but are not limited to, optical brighteners FB 210, FB 220, and FB 351, although other dyes can be used according to the specific embodiment, so long as they are soluble in the binder solution.

As mentioned above, the binder solution also includes at least one binder. The binder imparts strength to the green part by binding the particulate material and its layers together after a curing step in which some or all of the solvent in the binder solution is evaporated. Suitable binders include, but are not limited to, thermoplastic binders, thermosetting binders, and non-polymeric binders, such as waxes and sugars (e.g., glucose, fructose, derivatives thereof, or combinations thereof).

In an embodiment, the adhesive comprises a thermoplastic adhesive comprising one or more thermoplastic polymer chains. As used herein, the term "polymer chain" includes a polymer backbone and functional groups grafted thereto. In embodiments, the thermoplastic binder is selected from a class of thermoplastic polymers that generally decompose to small oligomers, carbon dioxide, and water in the absence of oxygen. Thus, in embodiments, the thermoplastic binder may be cleanly and easily removed during debinding and sintering to produce a consolidated portion that is substantially free of thermoplastic binder and decomposition products (e.g., coke and metal oxides).

In an embodiment, the one or more thermoplastic polymer chains comprise a first polymer chain. In an embodiment, the first polymer chain includes at least a first functional group. The functional groups of the first thermoplastic polymer chains can include, for example, but are not limited to, hydrogen bond donors, hydrogen bond acceptors, negatively charged groups, positively charged groups, or combinations thereof. In embodiments, the first functional group is part of the backbone of the first thermoplastic polymer chain. In embodiments, the first functional group of the first polymer chain may be complementary to a functional group of the second polymer chain of the thermoplastic binder to facilitate non-covalent coupling of the first polymer chain and the second polymer chain. For example, in embodiments, the first functional group is selected from a hydroxyl group, a carboxylate group, an amine group, a thiol group, an amide, or other suitable functional group capable of forming a weak non-covalent coupling of the first polymer chain and the second polymer chain.

In various embodiments, the first polymer chain includes one or more polymers such as, but not limited to, polyvinyl alcohol (PVA), polyamide, polyacrylamide (PAAm), polyvinyl methyl ether maleic anhydride (PVME-MA), polyvinyl pyrrolidone (PVP), polyacrylic acid (PAA), polymethyl methacrylate (PMMA), Polystyrene (PS), derivatives thereof, and/or combinations thereof. In embodiments, the first polymer chain has an average molecular weight (Mw or weight average molecular weight) of greater than or equal to 7,000g/mol to less than or equal to 100,000 g/mol. For example, the average molecular weight of the first polymer chain may be as follows: greater than or equal to 7,000g/mol to less than or equal to 100,000g/mol, greater than or equal to 7,000g/mol to less than or equal to 75,000g/mol, greater than or equal to 7,000g/mol to less than or equal to 50,000g/mol, greater than or equal to 7,000g/mol to less than or equal to 30,000g/mol, greater than or equal to 7,000g/mol to less than or equal to 25,000g/mol, greater than or equal to 7,000g/mol to less than or equal to 23,000g/mol, greater than or equal to 9,000g/mol to less than or equal to 50,000g/mol, greater than or equal to 9,000g/mol to less than or equal to 30,000g/mol, greater than or equal to 9,000g/mol to less than or equal to 25,000g/mol, greater than or equal to 9,000g/mol to less than or equal to 23,000g/mol, greater than or equal to 13,000g/mol to less than or equal to 50,000g/mol, Greater than or equal to 13,000g/mol to less than or equal to 30,000g/mol, greater than or equal to 13,000g/mol to less than or equal to 25,000g/mol, greater than or equal to 13,000g/mol to less than or equal to 23,000g/mol, greater than or equal to 23,000g/mol to less than or equal to 50,000g/mol, greater than or equal to 23,000g/mol to less than or equal to 30,000g/mol, greater than or equal to 23,000g/mol to less than or equal to 25,000g/mol, greater than or equal to 25,000g/mol to less than or equal to 50,000g/mol, greater than or equal to 25,000g/mol to less than or equal to 30,000g/mol, or greater than or equal to 30,000g/mol to less than or equal to 50,000g/mol, including any and all ranges and subranges therebetween.

The first polymer chains are present in the binder solution in the following amounts, based on the total weight of the aqueous binder solution: from greater than or equal to 1 wt% to less than or equal to 15 wt%, from greater than or equal to 1 wt% to less than or equal to 7 wt%, from greater than or equal to 3 wt% to less than or equal to 10 wt%, or from greater than or equal to 3 wt% to less than or equal to 9 wt%, including any and all ranges and subranges therebetween.

In an embodiment, the one or more thermoplastic polymer chains further comprise a second polymer chain. In an embodiment, the second polymer chains comprise at least a second functional group different from the first functional group of the first polymer chains. The functional groups of the second thermoplastic polymer chains can include, for example, but are not limited to, hydrogen bond donors, hydrogen bond acceptors, negatively charged groups, positively charged groups, or combinations thereof. In an embodiment, the second functional group of the second polymer chain is complementary to the first functional group of the first polymer chain of the thermoplastic adhesive to facilitate non-covalent coupling of the first polymer chain and the second polymer chain. For example, in various embodiments, the second functional group may be selected from a hydroxyl group, a carboxylate group, an amine group, a thiol group, an amide, or other suitable functional group capable of forming a weak non-covalent coupling of the first polymer chain and the second polymer chain.

In various embodiments, the second polymer chain comprises one or more other polymers such as, but not limited to, polyacrylic acid (PAA), polymethacrylic acid (PmAA), polyacrylamide (PAAm), derivatives thereof, and/or combinations thereof. In embodiments, the second polymer chain has an average molecular weight (Mw or weight average molecular weight) of greater than or equal to 100g/mol to less than or equal to 10,000g/mol, or greater than or equal to 500g/mol to less than or equal to 10,000 g/mol. For example, the average molecular weight of the second polymer chain may be as follows: from greater than or equal to 100g/mol to less than or equal to 10,000g/mol, from greater than or equal to 100g/mol to less than or equal to 5,000g/mol, from greater than or equal to 500g/mol to less than or equal to 10,000g/mol, from greater than or equal to 500g/mol to less than or equal to 5,000g/mol, or from greater than or equal to 5,000g/mol to less than or equal to 10,000g/mol, including any and all ranges and subranges therebetween.

In embodiments, the particular polymer selected as the second polymer chain may vary depending on the particular polymer selected as the first polymer chain. For example, the first polymer chain may be PVA and the second polymer chain may be PAA. Other polymer combinations may be used provided that their functional groups are capable of forming non-covalent bonds with each other. For example, in embodiments, one of the functional groups is a hydrogen donor and the other functional group is a hydrogen acceptor.

The second polymer chains are present in the binder solution in the following amounts, based on the total weight of the binder solution: greater than or equal to 1 wt% and less than or equal to 10 wt%, greater than or equal to 1 wt% and less than or equal to 9 wt%, greater than or equal to 1 wt% and less than or equal to 8 wt%, greater than or equal to 1 wt% and less than or equal to 7 wt%, greater than or equal to 1 wt% and less than or equal to 6 wt%, or even greater than or equal to 1 wt% and less than or equal to 5 wt%, or any range and all subranges formed by any of these endpoints.

The first polymer chains and the second polymer chains are contained in the binder solution in amounts such that: enabling a suitable degree of coupling between the first and second polymer chains to produce a green part having a green strength suitable for handling during a post-printing process. Further, the first polymer chains and the second polymer chains are present in amounts such that the binder solution has a viscosity of: the viscosity measured using a rheometer ranges from greater than or equal to about 2 centipoise (cP) to less than or equal to about 40 cP. In embodiments, the viscosity of the binder solution is from greater than or equal to 2cP to less than or equal to 40cP, from greater than or equal to 2cP to less than or equal to 35cP, from greater than or equal to 2cP to less than or equal to 30cP, from greater than or equal to 2cP to less than or equal to 25cP, from greater than or equal to 2cP to less than or equal to 15cP, from greater than or equal to 2cP to less than or equal to 12cP, from greater than or equal to 4cP to less than or equal to 40cP, from greater than or equal to 4cP to less than or equal to 30cP, from greater than or equal to 4cP to less than or equal to 25cP, from greater than or equal to 4cP to less than or equal to 20cP, from greater than or equal to 4cP to less than or equal to 15cP, from greater than or equal to 4cP to less than or equal to 12cP, from greater than or equal to 6cP to less than or equal to 40cP, from greater than or equal to 6cP to less than or equal to 35cP, Greater than or equal to 6cP to less than or equal to 30cP, greater than or equal to 6cP to less than or equal to 25cP, greater than or equal to 6cP to less than or equal to 20cP, greater than or equal to 6cP to less than or equal to 15cP, greater than or equal to 6cP to less than or equal to 12cP, greater than or equal to 8cP to less than or equal to 40cP, greater than or equal to 8cP to less than or equal to 35cP, greater than or equal to 8cP to less than or equal to 30cP, greater than or equal to 8cP to less than or equal to 25cP, greater than or equal to 8cP to less than or equal to 20cP, greater than or equal to 8cP to less than or equal to 15cP, greater than or equal to 8cP to less than or equal to 12cP, including any and all ranges and subranges therebetween. In various embodiments, the weight% ratio of the first polymer chains to the second polymer chains is 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 8:1, 10:1, or any other suitable ratio. In a specific embodiment, the first polymer chains are present in an amount of greater than or equal to 4 wt% to less than or equal to 6 wt%, the second polymer chains are present in an amount of greater than or equal to 1 wt% to less than or equal to 2 wt%, and the weight% ratio is 6:1 to 2: 1. Although various embodiments are described herein with reference to first polymer chains and second polymer strands, it is contemplated that in some embodiments, the thermoplastic binder may include three or more polymer chains.

In addition to the fluorescent material and the thermoplastic binder, the binder solution also contains a binder medium. The binder medium may include, for example, water, one or more non-aqueous solvents, or a combination thereof. The binder medium is typically non-reactive (e.g., inert) such that it does not react with the powder material or the thermoplastic binder in the binder solution to an extent that substantially adversely alters the resulting properties of the binder solution. Suitable non-aqueous solvents include, for example, but are not limited to, 2-methoxyethanol, butanol, 2-butanol, t-butanol, 1-methoxy-2-propanol, 2-butoxyethanol, isoamyl alcohol, isobutyl alcohol, ethylene glycol butyl ether, ethylene glycol, diethylene glycol, Tetrahydrofuran (THF), Methyl Ethyl Ketone (MEK), or combinations thereof. In embodiments, the solvent is present in the binder solution in an amount, based on the total weight of the binder solution, of: greater than or equal to 1 wt% and less than or equal to 75 wt%, greater than or equal to 1 wt% and less than or equal to 50 wt%, greater than or equal to 1 wt% and less than or equal to 25 wt%, greater than or equal to 1 wt% and less than or equal to 10 wt%, greater than or equal to 10 wt% and less than or equal to 75 wt%, greater than or equal to 10 wt% and less than or equal to 50 wt%, greater than or equal to 10 wt% and less than or equal to 25 wt%, greater than or equal to 25 wt% and less than or equal to 75 wt%, greater than or equal to 25 wt% and less than or equal to 50 wt%, or even greater than or equal to 50 wt% and less than or equal to 75 wt%, or any and all subranges formed by any one of these endpoints.

In various embodiments, the binder medium additionally or alternatively includes water, which in various embodiments constitutes the balance of the solution. In various embodiments, water is present in an amount greater than 80 wt.%, greater than 85 wt.%, or even greater than 90 wt.%, based on the total weight of the binder solution.

Although embodiments have been described with reference to binder solutions comprising relatively large amounts of water (e.g., water is the solvent present in the greatest amount (by volume); referred to herein as "aqueous binder solutions" or "water-based binder solutions"), it is contemplated that the binder solutions may be based on non-aqueous solvents (also referred to herein as "solvent-based" solutions) and, thus, may comprise small amounts of water or, in some embodiments, no water. Thus, it is contemplated that the fluorescent materials disclosed herein can be used in conjunction with a wide variety of binder solutions.

In embodiments, the binder solution may optionally include one or more additives, such as additives that may facilitate deposition of the thermoplastic binder into the powder material, facilitate dispersion of the fluorescent material in the binder medium, improve wetting of the powder material, modify the surface tension of the binder solution, and the like. Optional additives include surfactants, diluents, viscosity modifiers, dispersants, stabilizers, dyes or other colorants, or other additives known and used in the art. In some embodiments, the binder solution includes at least one surfactant.

Suitable surfactants for use in the binder solution include ionic (e.g., zwitterionic, cationic, or anionic) or nonionic surfactants, depending on the nature of the thermoplastic binder and/or the powdered material. In various embodiments, the surfactant may be 2- [4- (2,4, 4-trimethylpentan-2-yl) phenoxy]Ethanol (e.g., TRITON available from the dow chemical company)^TMX-100), polyoxyethylene (80) sorbitan monooleate (e.g., TWEEN available from Croda America Inc.)^TM80) Polyoxyethylene-23-lauryl ether (e.g., BRIJ)^TML23 available from Croda America), alkylene oxide copolymers (e.g., HYPERMER available from Croda Advanced Materials)^TMKD2), Sodium Dodecyl Sulfate (SDS), cetyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB), polypropoxy quaternary ammonium chlorides (e.g., VARIQUAT from Evonik Industries^TMCC 42NS), and combinations thereof.

Fig. 1 is a block diagram depicting an embodiment of a method 100 of manufacturing an article by additive manufacturing using a water-based binder solution as described herein. To facilitate discussion of aspects of the method 100, referring to fig. 2, fig. 2 is a block diagram depicting an embodiment of an additive manufacturing apparatus 200 that may be used to perform the method 100.

As shown in fig. 1, the method 100 begins by depositing a layer 202 of powder material for fabricating a component (block 102). In various embodiments, the layer of powder material 202 is deposited on a working surface 204 of the additive manufacturing apparatus. The powder material may be a metal powder, such as a nickel alloy (e.g., Inconel 625, Inconel 718, Rene '108, Rene '80, Rene '142, Rene '195, Rene ' M2, and/or Marm-247), a cobalt alloy (e.g., X40, X45, FSX414, Hans 188, and/or L605), a cobalt-chromium alloy, a titanium alloy, an aluminum-based alloy, tungsten, stainless steel, or a combination thereof. Other powder materials may be used depending on the particular implementation. For example, in an embodiment, the powder material 202 may include a ceramic material, such as alumina, aluminum nitride, zirconia, titania, silica, silicon nitride, silicon carbide, boron nitride, or a combination thereof. In an embodiment, the powder material 202 may include a high temperature polymer or glass material.

Next, the method 100 continues by selectively depositing a binder solution 206 into the layer of powder material 202 in a pattern representative of the structure of the layer of the component (block 104). The binder solution 206 may be, for example, any of the various embodiments of binder solutions described herein, which include a binder and a fluorescent material 220 in a solvent. In various embodiments, the binder solution 206 is selectively printed using a print head 208, the print head 208 being operated by a controller 210 based on a CAD design of a representative pattern of a layer comprising the part being printed.

In various embodiments, the controller 210 for controlling the print head 208 may comprise a distributed control system or any suitable or dedicated device employing a general purpose computer. The controller 210 generally includes a memory 212 that stores one or more instructions for controlling the operation of the printhead 208. In an embodiment, memory 212 stores a CAD design representing the structure of the part being manufactured. In an embodiment, the CAD design may include distortion compensation, and as such, the CAD design may not exactly match the geometry of the final desired part. Further, the controller 210 includes at least one processor 214 (e.g., a microprocessor), and the memory 212 may include one or more tangible, non-transitory machine-readable media that collectively store instructions executable by the processor 214 to control the actions described herein.

After the binder solution 206 is selectively deposited into the layer of powder material 202, the thermoplastic binder 216 in the binder solution 206 at least partially coats the outer surface of the powder particles, thereby creating binder-coated particles 218. As will be described, the thermoplastic binder 216 bonds to the binder coated particles 218 in a pattern of the binder solution 206 printed into the layer of powder material 202 to form a layer of the green part.

The method 100 may repeat the following steps: a layer of powder material is deposited (block 102), and optionally a binder solution 206 is deposited into the layer of powder material (block 104), and the component is built up continuously in a layer-by-layer fashion until the desired number of layers have been printed. The thermoplastic binder 216 of the binder solution 206 bonds each successive layer and provides the printed part with a degree of strength (e.g., green strength) such that the structural integrity of the printed green part is maintained during post-printing processing (e.g., transfer, inspection, and/or dusting). That is, the green strength provided by the thermoplastic binder 216 of the binder solution 206 maintains the bond between the layers and the particles of powder material 202 within the mass during handling of the green part and post-printing processing, e.g., resists and/or prevents separation of the layers.

In various embodiments, the green printed component fluoresces when exposed to electromagnetic radiation due to the fluorescent material 220 in the binder solution 206. The intensity of the fluorescence will depend on the fluorescent material 220 included, the particular powder material 202, and, in embodiments, the amount of binder solution 206 present in the green printed part. In various embodiments, fluorescence of the printed green part, and in particular the intensity of the emitted light, enables monitoring of the method of manufacturing the printed green part and curing of the printed green part to form a brown blank or consolidated part, as described in more detail below.

In various embodiments, the method 100 continues with curing the thermoplastic adhesive (block 106). For example, as described above, the binder solution 206 is a mixture of the fluorescent material 220, the thermoplastic binder 216, and a solvent. Although a portion of the solvent in the binder solution 206 may be evaporated during deposition (e.g., printing) of the binder solution 206, a certain amount of solvent may remain within the layer of powder material 202. Thus, in embodiments, the binder solution 206 may be thermally cured at a temperature suitable to evaporate the solvent, and in some embodiments, to allow a portion of the fluorescent material 220 to remain in the printed layer and allow for effective bonding of the printed layer to form the green part. The heat may be applied to the printed parts using IR lamps and/or a heating plate, or may be applied by placing the printed parts in an oven. In an embodiment, curing the binder solution 206 includes heating the print layer at a temperature that: greater than or equal to 25 ℃ and less than or equal to 100 ℃, greater than or equal to 30 ℃ and less than or equal to 90 ℃, greater than or equal to 35 ℃ and less than or equal to 80 ℃, or even greater than or equal to 40 ℃ and less than or equal to 70 ℃, or any and all ranges and subranges formed by any of these endpoints.

After the curing step of block 106, the unbonded particles from the powder layer (e.g., powder material that is not bonded by the binder solution 206) may be removed to prepare the green part for post-processing steps (e.g., debinding and sintering).

In embodiments, evaporation of the solvent from the green part results in a decrease in the intensity of light emitted by the green part upon exposure to electromagnetic radiation. Without being bound by theory, it is believed that in some embodiments, evaporation of the solvent results in the fluorescent material not being encapsulated and, as a result, may be passivated by the metal powder, thereby reducing the intensity of the fluorescent signal. It is further believed that in some embodiments, the powder absorbs photons more efficiently, thereby reducing the excitation of the fluorescent material by the UV light. Furthermore, in embodiments, at least a portion of the phosphor material may evaporate or decompose depending on the chemical structure of the phosphor material and the temperature at which the green part is cured. Thus, the intensity of the light emitted by the green part is related to the degree of curing, with lower intensities corresponding to greater curing of the green part. Thus, in embodiments, the green part may be cured until the intensity of light emitted by the green part is below a predetermined threshold intensity.

After curing, the green part may undergo an optional drying step (not shown in fig. 1) to remove any residual solvent and/or other volatile materials remaining in the green part. For example, the green part may be dried in vacuum, in an inert atmosphere (e.g., nitrogen or argon) or air, or at slightly elevated temperatures (e.g., up to 170 ℃ or even up to 200 ℃, depending on the particular solvent present in the binder solution).

In the embodiment shown in fig. 1, the method 100 includes removing (e.g., debinding) a portion of the thermoplastic binder 216 from the green part to produce a brown blank (block 108). In various embodiments, the binder provides strength (e.g., green strength) to the printed part such that only a portion (i.e., less than all) of the thermoplastic binder 216 is removed during debinding of the green part to increase the handling strength of the resulting brown blank prior to sintering.

During debinding at block 108, the green part is heated to decompose a portion of the polymer chains of the thermoplastic binder 216. For example, the green part may be heated to a temperature of about 600 ℃ or less, or about 450 ℃ or less. In an embodiment, the green part is heated to a temperature of 250 ℃ to 450 ℃. The heating may be performed, for example, in an oxygen-free environment (e.g., in a vacuum, an inert atmosphere, or a combination of both) or in air. In embodiments where the debonding is performed in an inert atmosphere, argon, nitrogen, or another substantially inert gas may be used. In some embodiments, the debinding step may be combined with the sintering step to produce the final consolidated component.

According to various embodiments, the debonding step of block 108 is effective to remove greater than about 95% of the thermoplastic adhesive 216. For example, greater than or equal to 95%, greater than or equal to 96%, greater than or equal to 97%, greater than or equal to 98%, or greater than or equal to 99% of the total amount of thermoplastic adhesive 216 is removed during debonding. In some embodiments, the portion of the thermoplastic adhesive 216 remaining in the brown blank is less than or equal to 5%, less than or equal to 4%, less than or equal to 3%, less than or equal to 2%, or less than or equal to 1% of the amount of thermoplastic adhesive 216 present prior to the debinding step. In embodiments, the portion of the thermoplastic binder 216 remaining in the brown blank is 0.05% to 2% or 0.1% to 1% of the amount of thermoplastic binder 216 that is present prior to the debinding step and removed in a later stage of the sintering process (e.g., above 600 ℃ and into the higher sintering temperature for stainless steel, nickel alloys, etc. described according to block 110).

After debinding at block 108, the method 100 continues with sintering the brown blank to form a consolidated component (block 110). During sintering, the remaining portion of the thermoplastic binder (e.g., oligomers formed during debinding) is removed from the brown blank and the powder particles are consolidated to form consolidated portions. Sintering imparts strength and integrity to the brown blank, making the consolidated component suitable for use in, for example, machinery after cooling.

In some embodiments, sintering may be performed according to a two-step process that includes a pre-sintering step in which the remaining portion of the thermoplastic binder is removed and a sintering step in which the powder particles are consolidated. In some embodiments, sintering may be performed as a single step. During sintering, the brown blank is heated to a temperature greater than 500 ℃, greater than 800 ℃, or greater than 1000 ℃. In embodiments, the heat may be applied by placing the brown blank in an oven, or by exposing the brown blank to a concentrated energy source (e.g., a laser beam, an electron beam, or another suitable energy source), depending on the particular embodiment.

Although the various embodiments described herein are described with reference to method 100, it is understood that the embodiments of the binder solution described herein may be used with various methods known and used by those skilled in the art. In particular, the curing and sintering may be accomplished in a number of different ways, in a number of different steps, and at a number of different locations.

As described above, embodiments of binder solutions including fluorescent materials enable visual monitoring of additive manufacturing processes. In embodiments, the fluorescent material may be visible to the human eye. Additionally, or alternatively, an optical imaging system may be used to observe the fluorescent material, and in embodiments, quantify the amount of binder solution present in the powder layer based on the observed fluorescence.

Thus, in embodiments, the adhesive solution is quantified or detected by observing the Ultraviolet (UV) fluorescence of the adhesive solution. In such embodiments, the powder material 202 of the powder layer may be irradiated with UV light having a wavelength of less than or equal to about 400nm and fluoresce at a wavelength of greater than or equal to 400nm at portions where the binder solution is present. For example, a UV light sensor 300 as shown in fig. 3 may be employed. Although various embodiments are described with respect to UV fluorescence, fluorescence at other wavelengths is contemplated, including but not limited to near Infrared (IR) wavelengths.

Referring now to fig. 3, the UV light sensor 300 is described in more detail. In various embodiments, the UV light sensor 300 is a luminescence sensor that emits UV light and detects a resulting visible glow (visible glow) caused by the interaction of the UV light with a phosphorescent material (e.g., an encapsulated fluorescent material). In particular, the UV light sensor 300 detects the resulting visible glow caused by the interaction of UV light in the region of the powder layer in the presence of the binder solution 206 (containing the fluorescent material 220). In an embodiment, UV light sensor 300 may emit one or more wavelengths of UV light less than or equal to 600nm, less than or equal to 400nm, less than or equal to 375nm, or less than or equal to 370 nm. For example, the UV light sensor 300 may emit light having a wavelength of greater than or equal to 150nm to less than or equal to 600nm, greater than or equal to 175nm to less than or equal to 500nm, greater than or equal to 340nm to less than or equal to 600nm, greater than or equal to 340nm to less than or equal to 400nm, or greater than or equal to 200nm to less than or equal to 400nm, including any and all ranges and subranges therein. In one particular embodiment, the UV light sensor 300 emits light at a wavelength of 365nm, although other wavelengths are contemplated and may be used depending on the particular fluorescent material used.

Furthermore, it is envisaged that in embodiments, different sources of electromagnetic radiation may be employed, for example a light source emitting light at a wavelength different from the UV wavelength. Thus, although the various embodiments described herein are described with reference to a "UV light sensor" and a "UV light source," it is contemplated that other light sensors and electromagnetic radiation sources may be employed depending on the particular fluorescent material 220 included in the adhesive solution 206. Specifically, suitable electromagnetic radiation sources include electromagnetic radiation sources that excite fluorescent material 220 and cause fluorescent material 220 to emit light in response to exposure to electromagnetic radiation emitted by the electromagnetic radiation source.

In various embodiments, the UV light sensor 300 includes a UV light source 301 that emits UV light 302, a photodetector 304 (e.g., a photodiode, etc.) that detects visible light 306 emitted by a target (e.g., the powder material 202 in a powder layer) when the UV light 302 is incident on the target, and a lens 308 that directs the UV light 302 toward the target (e.g., the powder material 202). The UV light source 301 may be, for example, a mercury lamp with a UV filter or a UV LED. The UV light sensor 300 may also include electronic circuitry 310, which electronic circuitry 310 powers the UV light source 301 and the photodetector 304 and produces an output indicative of the detected light. In an embodiment, the UV light sensor 300 further comprises a dichroic mirror 312, the dichroic mirror 312 separating reflected light 314 into UV light 316 away from the photodetector 304 and visible light 306 towards the photodetector 304.

As an alternative to using the UV light sensor 300 of fig. 3, in some embodiments, a UV light source may be used to illuminate the powder material 202 and fluorescence may be detected with the human eye or by using another type of camera or optical detector. Further, it is contemplated that the UV light sensor 300 and/or the photodetector or other optical detector may be located at a different location than on the print head 208. For example, the UV light sensor 300 may be located on a wall of a build box, or mounted within or on an additive manufacturing apparatus. In other embodiments, the UV light sensor 300 may be mounted in or on an oven or other accelerated curing device, such as in embodiments where the UV light sensor 300 is used to monitor the degree of curing of a printed part, as will be described in more detail below.

In various embodiments, the information collected by the photodetector 304 is processed (e.g., by the UV light sensor 300, by the controller 210, or by another computing device communicatively coupled to the UV light sensor 300) to determine the presence or amount of the binder solution 206 in the powder material 202 based on the intensity of the light emitted by the fluorescent material 220. For example, in an embodiment, the information collected by the photodetector 304 may be used to generate an image of each layer of the printed part, which may be compared to an expected image of that layer to identify spatial defects, including jet misfires, inaccurate adhesive amount deposition (e.g., saturation), and degree of adhesive cure. In particular, in the event that the expected image of the layer does not match the generated image, a problem may be identified by the system and an alarm may be generated. Alternatively, or in addition, the system may cause the print head 208 to be cleaned, the binder solution 206 to be refilled in a binder solution container, or other maintenance to the additive manufacturing apparatus. In embodiments, the system may cause all or part of the layer to be reprinted.

In an embodiment, the computing device that processes the information from the photodetector 304 includes information about the fluorescence of the binder solution 206 at various concentrations, which may be stored, for example, in a database. The information on the fluorescence includes, for example, the intensity of light emitted by the fluorescent material 220 and the position of light emitted by the fluorescent material 220. This information can be used to determine the concentration of the binder solution (e.g., how much solvent is present in the binder solution) based on the observed fluorescence level. In particular, when the solvent is evaporated or removed during curing, the fluorescence of the binder solution 206 decreases. Thus, in an embodiment, the amount of fluorescence observed by the photodetector 304 is used to determine the degree of curing (e.g., how much the printed part has cured and how much binder solution remains). In an embodiment, curing may be performed until the intensity of light emitted by the fluorescent material 220 is below a predetermined threshold intensity. The predetermined threshold strength may be determined based on the amount of binder solution 206 present in the green part having sufficient strength to enable the green part to be moved or subjected to other post-printing processing. In an embodiment, the predetermined threshold intensity is an intensity value that is greater than zero and less than the maximum intensity observed, and may be, for example, less than or equal to 75% of the maximum intensity, less than or equal to 50% of the maximum intensity, less than or equal to 35% of the maximum intensity, less than or equal to 25% of the maximum intensity, less than or equal to 15% of the maximum intensity, less than or equal to 10% of the maximum intensity, less than or equal to 5% of the maximum intensity, less than or equal to 2.5% of the maximum intensity, or less than or equal to 1% of the maximum intensity.

Additionally, or alternatively, the amount of fluorescence observed by the photodetector 304 is used to determine that the binder solution 206 has been concentrated (e.g., by evaporation of solvent from the binder solution).

Examples

The following examples are provided to illustrate various embodiments and are not intended to limit the scope of the claims. All parts and percentages are by weight unless otherwise indicated. The following provides approximate properties, characteristics, parameters, and the like for various working examples, comparative examples, and materials used in the working examples and comparative examples.

Example 1

To a binder solution comprising 1-7 wt% PVA, 0.5-3 wt% PAA,2-6 wt% ethylene glycol, 4-10 wt% ethylene glycol butyl ether and the balance water is added a pigment solution (pigment in water). The pigment solutions used for each of samples a-D are provided in table 1 below.

TABLE 1

When added at a concentration to give a 1,000 fold dilution of the pigment in the binder solution (0.1 wt% pigment in the binder solution), it can be observed that the fluorescent pigment particles float in the binder solution, giving the binder solution a slightly cloudy appearance. However, when diluted by 10,000 times (0.01 wt% pigment in the binder solution), the pigment particles are dissolved in the binder solution, and the binder solution is transparent.

Drops of each binder sample a-D were placed on a nickel alloy powder layer and the results were observed under ambient light and short UV wavelength light (365 nm). Fluorescence was observed at the droplet position at 1,000-fold dilution and 10,000-fold dilution concentration for each of samples a-D. Thus, it was determined that fluorescent pigments can be used to monitor an additive manufacturing process when incorporated into a binder solution.

Example 2

To prepare sample E, 0.25 wt% Glo Effex invisible blue UV reactive dye was added to a binder solution comprising 1-7 wt% PVA, 0.5-3 wt% PAA,2-6 wt% ethylene glycol, 4-10 wt% ethylene glycol butyl ether, and balance water. A drop of the binder solution was placed on the nickel alloy powder layer and the results were observed under ambient light and short UV wavelength light (365 nm). Bright blue fluorescence was observed when exposed to UV wavelength light, indicating that the encapsulated fluorescent material can be used to monitor the additive manufacturing process when incorporated into a binder solution.

Example 3

To determine whether a pure dye (e.g., unencapsulated) can be incorporated into the binder solution, various fluorescent materials were added to the binder solution to form samples F-H and comparative samples 1-5, which included 1-7 wt% PVA, 0.5-3 wt% PAA,2-6 wt% ethylene glycol, 4-10 wt% ethylene glycol butyl ether, and the balance water. Specifically, 0.2-0.5 wt% of a fluorescent material (DayGlo, UMC Corp., Aldrich) was added to the binder solution, and stirred on a hot plate at 50-70 ℃ to dissolve the dye into the binder solution. Droplets of each of the binder solutions of samples F-H and comparative samples 1-5 were added to a ren 108 nickel alloy powder layer and excited using 365nm UV light. The fluorescent materials and solubilities and fluorescence observations for each of these samples are given in table 2.

TABLE 2

In particular, at 0.5 wt% fluorescent dye in the binder solution, the dyes in samples F, G and H were completely soluble, resulting in a clear binder solution, while the dyes in comparative samples 2-5 were partially insoluble, resulting in a cloudy solution. Each dye of samples F-H produced a uniform signal at different emission levels when added to a Rene 108 nickel alloy powder layer and excited using 365nm UV light. Comparative sample 1 generated a sputter emission signal due to the insolubility of the dye in the binder solution.

To more fully understand the observations, the structure of the dye was studied. The structure of each dye is shown in table 3 below.

TABLE 3

By observing the structures of the respective dyes, it was concluded that the stilbene chromophore system disodium salt included in comparative samples 1 to 5 did not exhibit good solubility in the binder solution, but that the stilbene chromophore system tetrasodium salt in samples F and G exhibited good solubility. However, these stilbene chromophore based tetrasodium salts exhibit relatively weak fluorescence on the metal powder bed when compared to the biphenyl styryl chromophore disodium salt of sample H, which exhibits good solubility in the binder solution and bright uniform fluorescence on the metal powder bed.

Without being bound by theory, it is believed that certain functional or performance characteristics are important for the pure dye to be encapsulated by the polymer in the binder solution. In particular, it is believed that the disodium, trisodium, and tetrasodium sulfonate functional groups render the dye soluble in aqueous binder systems, such as the binder solutions used in the examples. In addition, it is believed that the pendant functional groups, such as sulfonate, triazine, etc., can protect the internal fluorescent chromophore from direct exposure to the metal powder, thereby protecting the internal fluorescent chromophore from quenching. However, it should be understood that the particular functional group may vary depending on the particular adhesive system, and may vary, for example, when: when the dye is incorporated into a solvent-based binder solution, or when the dye is applied to a different type of powder (e.g., ceramic or polymer-based powder).

Other aspects of the invention are provided by the subject matter of the following clauses:

1. a method of manufacturing a green part, comprising: depositing a layer of powder on a work surface; and selectively depositing a binder solution comprising a thermoplastic binder, a fluorescent material, and a binder medium into the powder layer in a pattern representative of the structure of the layer of the green part, wherein: the thermoplastic binder comprises one or more polymer chains dissolved in a solvent medium, the polymer chains having an average molecular weight of greater than or equal to 7,000g/mol to less than or equal to 100,000 g/mol.

2. The method of any one of the preceding clauses wherein the fluorescent material is encapsulated prior to incorporation into the binder solution.

3. The method of any one of the preceding clauses wherein the fluorescent material is encapsulated when mixed into the binder solution.

4. The method of any one of the preceding clauses wherein the one or more polymer chains comprise one or more polymer species selected from the group consisting of: polyvinyl alcohol (PVA), polyamide, polyacrylamide (PAAm), polyvinyl pyrrolidone (PVP), polyacrylic acid (PAA), polymethacrylic acid (PmAA), Polymethylmethacrylate (PMMA), polyvinylmethylether-maleic anhydride (PVME-MA), Polystyrene (PS), polyethylene oxide, polyethylene glycol (PEG), derivatives thereof, and combinations thereof.

5. The method of any one of the preceding clauses wherein the one or more polymer chains in the thermoplastic binder comprise a first polymer chain comprising a first functional group and a second polymer chain comprising a second functional group different from the first functional group, the first and second functional groups configured to non-covalently couple the first polymer chain to the second polymer chain, the second polymer chain having an average molecular weight greater than or equal to 100g/mol and less than or equal to 10,000 g/mol.

6. The method of any one of the preceding clauses wherein the fluorescent material comprises an encapsulated aromatic dye.

7. The method of any one of the preceding clauses wherein the aromatic dye is selected from the group consisting of: stilbene dyes, pyrene dyes, coumarin dyes, anthracene dyes, tetracene dyes, and combinations thereof.

8. The method of any one of the preceding clauses wherein the fluorescent material comprises a chromophore having at least one sulfonate or triazine group.

9. The method of any one of the preceding clauses wherein the chromophore comprises two, three, or four sulfonate groups.

10. The method of any one of the preceding clauses wherein the chromophore is a stilbene-based chromophore.

11. The method of any one of the preceding clauses wherein the binder solution is an aqueous binder solution.

12. The method of any of the preceding clauses wherein the encapsulated fluorescent material is present in an amount of 0.01 to 5 weight percent based on the total weight of the binder solution.

13. The method of any of the preceding clauses wherein the encapsulated fluorescent material is present in an amount of 0.1 to 1 weight percent based on the total weight of the adhesive solution.

14. The method of any of the preceding clauses wherein the method further comprises: exposing the layer of the green part to electromagnetic radiation; curing the layer of green part; and monitoring the intensity of light emitted by the fluorescent material, wherein the curing is performed until the intensity of light emitted by the fluorescent material is below a predetermined threshold intensity.

15. The method of any one of the preceding clauses wherein the electromagnetic radiation is Ultraviolet (UV) radiation.

16. The method of any one of the preceding clauses wherein the UV radiation has a wavelength of greater than or equal to 340nm to less than or equal to 600 nm.

17. The method of any one of the preceding clauses wherein the UV radiation has a wavelength of greater than or equal to 340nm to less than or equal to 400 nm.

18. The method of any one of the preceding clauses wherein the powder comprises a metal powder.

19. A green part formed by the method of any of the preceding clauses.

20. A green part comprising powdered materials bonded together with at least one binder comprising a fluorescent material.

21. A binder solution, wherein the binder solution comprises: a thermoplastic binder comprising first polymer chains having an average molecular weight of from greater than or equal to 7,000g/mol to less than or equal to 100,000 g/mol; a fluorescent material; and an adhesive medium.

22. The binder solution according to any one of the preceding clauses, wherein the fluorescent material is encapsulated prior to incorporation into the binder solution.

23. The binder solution according to any one of the preceding clauses, wherein the fluorescent material is encapsulated when mixed into the binder solution.

24. The adhesive solution of any one of the preceding clauses wherein the first polymer chain comprises one or more polymer species selected from the group consisting of: polyvinyl alcohol (PVA), polyamide, polyacrylamide (PAAm), polyvinyl pyrrolidone (PVP), polyacrylic acid (PAA), polymethacrylic acid (PmAA), Polymethylmethacrylate (PMMA), polyvinylmethylether-maleic anhydride (PVME-MA), Polystyrene (PS), polyethylene oxide, polyethylene glycol (PEG), derivatives thereof, and combinations thereof.

25. The binder solution according to any one of the preceding clauses, wherein the thermoplastic binder further comprises a second polymer chain, the first polymer chain comprising a first functional group, the second polymer chain comprising a second functional group different from the first functional group, the first and second functional groups configured to non-covalently couple the first polymer chain to the second polymer chain, the second polymer chain having an average molecular weight greater than or equal to 100g/mol and less than or equal to 10,000 g/mol.

26. The adhesive solution of any one of the preceding clauses wherein the fluorescent material comprises an encapsulated aromatic dye.

27. The binder solution according to any one of the preceding clauses wherein the aromatic dye is selected from the group consisting of: stilbene dyes, pyrene dyes, coumarin dyes, anthracene dyes, tetracene dyes, and combinations thereof.

28. The binder solution according to any one of the preceding clauses wherein the fluorescent material comprises a chromophore having at least one sulfonate or triazine group.

29. The adhesive solution of any one of the preceding clauses wherein the chromophore comprises two, three, or four sulfonate groups.

30. The adhesive solution of any one of the preceding clauses wherein the chromophore is a stilbene-based chromophore.

31. The binder solution according to any one of the preceding clauses wherein the binder solution is an aqueous binder solution.

32. The adhesive solution of any one of the preceding clauses wherein the encapsulated fluorescent material is present in an amount of 0.01 to 5 weight percent based on the total weight of the adhesive solution.

33. The adhesive solution of any one of the preceding clauses wherein the encapsulated fluorescent material is present in an amount of 0.1 to 1 weight percent based on the total weight of the adhesive solution.

34. A green part bonded together using the binder solution of any of the preceding clauses.

It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments of the present disclosure without departing from the spirit and scope of the disclosure. Thus, it is intended that the present disclosure cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.