Fracturable support structure and method of forming the structure

Abstract

To provide a three-dimensional structure that includes a support structure attached to an article at a fracturable interface, and a method of additive manufacturing for making the three-dimensional structure.SOLUTION: A method of additive manufacturing comprises: i) forming a first layer comprising at least one material chosen from an article material, a support structure material and a fracturable material; ii) forming an additional layer on the first layer, the additional layer comprising at least one material chosen from the article material, the support structure material and the fracturable material; and iii) repeating the step of ii) one or more times to form a three-dimensional structure comprising an article and at least one support structure attached to the article at an interface, the interface comprising the fracturable material formed during one or more of the steps i), ii) or iii), the fracturable material being formed by exposing a print material to a gas reactant.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure is directed to a three-dimensional structure including a support structure attached to an article at a breakable interface, and a method of additive manufacturing for fabricating the three-dimensional structure.

Background Art

[0002] Additive manufacturing is often performed one layer at a time, and support structures are often used to support the structure during the printing process. These support structures can take the form of, for example, a plurality of pillars that support overhang structures of the printed part. Support structures serve multiple functions. For example, these support structures provide structural stability to the deposited layer as the printed article (sometimes referred to as a "part") spreads from a narrow base region. The support provided by these structures can enable printing of more complex geometries and can enable weight reduction of the final part. Further, support structures enable improved thermal management during printing, especially when printing metals. These structures provide a path for thermal energy to move from the part to the heat sink or from the heat source to the part. Support structures can be developed using the same material used to fabricate the part or, if the printer has the ability to print multiple materials, can be printed from a second material.

[0003] One problem with many support structures, especially in metal printing, is that they are not easily removed from the part. A significant amount of time and / or cost can be expended during "post-processing" to completely remove the support structure and smooth or polish the remaining rough areas left on the part surface. Further, such support structures can result in degradation of the quality of the final printed part surface.

[0004] Improved support structures and additive manufacturing methods using support structures would be desirable advancements in the art.

Summary of the Invention

[0005] One embodiment of the present disclosure relates to a method of additive manufacturing. The method includes: i) forming a first layer comprising at least one material selected from article material, support structure material and shatterable material; ii) forming an additional layer on the first layer comprising at least one material selected from article material, support structure material and shatterable material; and repeating ii) and iii) one or more times to form a three-dimensional structure comprising an article and at least one support structure attached to the article at an interface, wherein the interface comprises shatterable material formed between one or more of i), ii) or iii), and the shatterable material is formed by exposing a printing material to a gaseous reactant to form a three-dimensional structure.

[0006] Another embodiment of the present disclosure relates to an additive manufacturing method. The method includes i) spraying a droplet containing metal to form a first layer containing at least one material selected from article material, support structure material and shatterable material; ii) spraying an additional droplet containing metal to form an additional layer on the first layer containing at least one material selected from article material, support structure material and shatterable material; and repeating ii) and iii) one or more times to form a three-dimensional structure comprising an article and at least one support structure attached to the article at an interface, wherein the interface includes shatterable material formed between one or more of i), ii) or iii), and the shatterable material is formed by exposing a portion of metal in the form of at least one selected from the droplet, additional droplet, first layer and additional layer to a gaseous reactant.

[0007] Another embodiment of this disclosure relates to a three-dimensional structure, which comprises an article containing a printing material. At least one support structure is attached to the article at a shatterable interface, which comprises a natural nonmetallic material distinct from the printing material.

[0008] Please understand that the general explanation above and the detailed explanation below are for illustrative and explanatory purposes only and do not limit this instruction as requested. [Brief explanation of the drawing]

[0009] The accompanying drawings incorporated herein and constituting part of this specification illustrate embodiments of this teaching and, together with the description, serve to illustrate the principles of this teaching. [Figure 1] This is a flowchart of a method for additive manufacturing according to one embodiment of the present disclosure. [Figure 2A] This is a schematic side view of a first layer deposited on a 3D printer construction plate according to one embodiment of the present disclosure. [Figure 2B] An example of a partially completed three-dimensional structure after multiple layers have been formed, according to one embodiment of the present disclosure, is shown. [Figure 2C] An example of a completed, pre-post-processing three-dimensional structure comprising an article and at least one support structure attached to the article at an interface is shown according to one embodiment of the present disclosure. [Figure 3] This is a schematic cross-sectional view of a single liquid ejector jet configured to spray a modified metal composition, according to one embodiment of the present disclosure.

[0010] Please note that some details in the figures have been simplified, and strict structural accuracy, detail, and scale are not maintained; they are depicted to facilitate understanding of the embodiments. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments of this teaching will be referred to in detail, and these embodiments are shown in the accompanying drawings. In the drawings, similar reference numerals are used throughout to designate the same elements. The following description will refer to the accompanying drawings, which form part of it and illustrate specific exemplary embodiments that can put this teaching into practice. Therefore, the following description is merely illustrative.

[0012] This disclosure relates to a method for manufacturing a three-dimensional structure and a structure formed thereby. The three-dimensional structure includes an article containing a printing material. At least one support structure is attached to the article at a shatterable interface. The shatterable interface contains a natural nonmetal (e.g., a natural oxide, natural oxynitride, or natural nitride) different from the printing material. Small amounts of natural nonmetals at the interface between the support structure and the 3D article may weaken the desired support of the 3D article and / or the desired conduction of thermal energy from the 3D article, for example, to a heat sink. Unbonded or weakly bonded areas at the interface create shatter or crack zones that allow the support structure to be easily removed after printing.

[0013] Figure 1 is a flowchart of an additive manufacturing method 100 according to one embodiment of the present disclosure. As shown in Figure 102, the method includes forming a first layer. The first layer includes at least one material selected from article material, support structure material, and shatterable material. Figure 2A is a schematic side view of an example of the first layer 120 deposited on a construction plate 122 of a 3D printer (not shown). As used herein, the term “on” is broadly defined as not requiring direct physical contact and encompasses configurations of both direct and indirect physical contact. Thus, an intervening layer can be placed between the first layer and the construction plate, or the first layer can be placed directly on the construction plate, for example. Unless otherwise expressly expressed herein, the appearance of the term “on” herein provides support for the concept of direct physical contact.

[0014] As shown in Figure 1, an additional layer is formed on the first layer. The additional layer may also include at least one material selected from article material, support structure material, and shatterable material. As shown in Figure 1, the layering process is repeated one or more times, as shown in Figure 106, to form a three-dimensional structure.

[0015] Each layer deposited to form a three-dimensional structure can contain one or more types of material. Figure 2B shows an example of a partially completed three-dimensional structure 126 after multiple layers have been formed. The top of the partially completed three-dimensional structure 126 is shown to contain article material 128, support structure material 130, and shatterable material 132. On the other hand, the layer in Figure 2A is shown to contain only article material 128 and support structure material 130. Furthermore, a single layer can contain only article material, only support material, only shatterable material, or any combination of these materials. The article material may be the same as or different from the support material. The advantage of both the article material and support material being the same printing material is the possibility of improving the thermal conductivity of the structural support, as the article and support have similar thermal conductivity and the ability to print the entire structure with fewer (e.g., single) printing nozzles.

[0016] The completed three-dimensional structure includes an article and at least one support structure attached to the article at an interface. The interface may include a shatterable material formed in one or more of the layering processes of Method 100. As will be described in more detail below, the shatterable material is formed, for example, by exposing a printing material, such as a support structure material, to a gaseous reactant. Figure 2C shows an example of a completed three-dimensional structure 126 comprising an article 136 and at least one support structure 138 attached to the article at an interface 140.

[0017] Article 136 may include any suitable material that can be deposited by additive manufacturing. In one embodiment, the article material is a metal such as aluminum, aluminum alloys (e.g., alloys 4008 and 6061 or any other), copper, copper alloys, silver, silver alloys, iron, or iron alloys such as steel, or other metals.

[0018] At least one support structure 138 may include any suitable material that can be deposited by additive manufacturing to provide the desired support. In one embodiment, the support structure material is a metal such as aluminum, aluminum alloys (e.g., alloys 4008 and 6061 or any other), copper, copper alloys, silver, silver alloys, iron, or iron alloys such as steel, or other metals. The width and spacing of the support structures 138 may vary depending on both the material being printed and the geometric shape of the article 136. Examples of width dimensions of the support structures 138 include diameters of about 0.5 mm to about 5 mm, such as about 1 mm to about 2 mm for cylindrical pillar-type structures. For support structures with non-circular cross-sections, these same width dimensions may apply to the shortest width dimension intersecting the longitudinal axis of the support structure. Examples of spacing between support structures 138 include distances of about 2 mm to about 20 mm, such as about 4 mm to about 8 mm. The longer the overhang (for example, the overhang shown in Figure 2C), the narrower the spacing between the support structures 138 can be to provide the desired support. In one example, the ratio of the total length of the overhang to the total width (e.g., diameter) of all the support structures providing support to the overhang is in the range of approximately 10:1 to approximately 2:1.

[0019] At least one interface 140 can be formed by reacting a gas with the printing material used to form the support structure and may include any suitable shatterable material that is easily shatterable while providing the desired support. The shatterable material may have one or more or all of the following properties: limited reactivity with the metal to be printed; printable; thermally stable at the construction temperature; sufficient thermal conductivity that does not excessively interfere with the growth of local microstructures; and the ability to deposit the desired metal or other printing material thereon (e.g., wettable by the printed metal).

[0020] The frangible material can be a natural non-metal. As used herein, the term "natural non-metal" means that the non-metal is formed by reacting a metal in solid or liquid form with a gas to form the non-metal. In one embodiment, the frangible material is a natural non-metal that is an oxide, nitride, or oxynitride of any of the metals described herein for making an article or a support structure. As an example, the printing material for making both article 136 and support structure 138 is aluminum or an aluminum alloy, and the frangible material is an oxide of aluminum or an aluminum alloy.

[0021] Examples of reaction gases that can be used to convert a metal to a frangible non-metal during the additive manufacturing process include oxygen-containing gases such as oxygen gas (O2), oxygen plasma, ozone (O3), and water gas (H2O), and nitrogen-containing gases such as ammonia (NH3) or nitrogen gas (N2).

[0022] FIG. 2C shows that the frangible interface 140 is disposed only at one or more ends of the support structure attached to the article 136, but other configurations of the interface 140 that allow for easy removal of the support structure can also be used. For example, any suitable amount of the support structure can include the frangible material. In one embodiment, the entire support structure 138, or substantially the entire support structure 138, includes a natural non-metal frangible material.

[0023] In one embodiment, the entire cross-section of the interface 140 can include the frangible material 132. In another embodiment, only a portion of the cross-section of the interface 140 reacts with the reactant gas to form the frangible material 132. This can make it possible to maintain the thermal conductivity and / or electrical conductivity while reducing the strength of the interface that allows for easy fracturing. If the goal is to use the article 136 without performing a post-print heat treatment, it may be desirable to react only a portion of the interface to maintain the electrical conductivity.

[0024] In one embodiment, the article material, the support structure material, and the frangible material are formed by printing layers using a printable material that is a liquid metal. For example, forming the layers can include jetting the liquid metal in an ambient atmosphere onto a printing substrate such as the build plate 122. As will be described in more detail below, the ambient atmosphere can be modified to form a metal or a non-metal. For example, when forming the frangible material, the ambient atmosphere can include a sufficient amount of a reactive gas greater than 10%, such as from about 15 vol% to about 100 vol%, or from about 20 vol% to about 90 vol%, to convert the metal printable material to a non-metal. When forming the metal portions of the article 136 or the support structure 138, the ambient atmosphere does not include a substantial amount of the reactive gas and instead uses an inert or substantially inert atmosphere such as an inert gas or a vacuum. For example, the amount of oxygen or other reactive gas can be in the range of 0% to less than 10 vol%, such as less than 5 vol%, less than 1 vol%, or less than 0.1 vol%, depending on the reactivity of the system being printed.

[0025] After the three-dimensional structure 126 has been printed, the method can further include cooling the article 136 and the support structure 138. If the additive manufacturing process uses liquid metal jetting, the process can be carried out without sintering the article 136. In other 3D printing processes, sintering can be carried out on the three-dimensional structure either before or after removal of the support structure 138.

[0026] The method may further include, for example, removing the support structure 138 by fracturing the fractible material at interface 140. The fracturing and removal of the support structure can be carried out without using mechanical cutting devices such as saws, wire cutters, or other such devices. For example, fracturing can be performed using techniques selected from vibrating the support structure, such as using an ultrasonic bath or bringing the structural support into contact with a pressurized fluid such as a water jet. A fractible interface combined with such a removal process may enable one or more of the following advantages: easy removal of the structural support, removal from the internal structure of the support that is difficult or impossible to address with cutting tools, and / or improvement of the surface quality of the final 3D article.

[0027] The method of this disclosure can be employed in any type of additive manufacturing process, such as extrusion or jetting. In one embodiment, the process is carried out in liquid metal deposition printing, such as a metal jetting process. One known technique for jetting metal is a magnetohydrodynamic (MHD) printer, which is suitable for forming 3D metallic objects by jetting a liquid metal layer onto a layer.

[0028] Figure 3 is a schematic cross-sectional view of a single liquid ejector jet configured to eject a modified metal composition, such as a shatterable material, in a metal injection process according to one embodiment of the present disclosure. The liquid ejector jet 200 is shown in Figure 3, and the liquid ejector jet 200 defines a nozzle 202 portion having a gas shield 204 surrounding the nozzle 202 portion. The gas shield 204 surrounds the nozzle 202 and contains a first gas 206, also called a cover gas. The cover gas surrounds the nozzle 202 with the cover gas 206. This gas or air shield 204 provides an air shield around the outer portion of the nozzle 202. The gas shield 204 surrounds the printing operation with an inert cover gas 206 which can be used to regulate the temperature and atmosphere around the liquid ejector jet 200.

[0029] The 3D printer and its associated liquid ejector jet 200 may also include one or more gas control devices that may be a source of cover gas 206 or contain it. The gas source may be configured to introduce the cover gas 206. The cover gas 206 may be or contain an inert gas such as helium, neon, argon, krypton, and / or xenon. In another embodiment, the gas may be or contain nitrogen. The gas may contain less than about 10 vol% oxygen, less than about 5 vol% oxygen, or less than about 1 vol% oxygen. In at least one embodiment, the gas may be introduced via a gas line that includes a gas regulator configured to regulate the flow or rate of one or more gases introduced from the gas source into and / or around the liquid ejector jet 200. For example, the gas may be introduced above a heating element for heating the liquid ejector jet 200 and / or the gas (not shown). This may allow a gas (e.g., argon) to form a shroud / sheath that acts as an air shield around the liquid ejector jet 200, droplet 214, 3D object, and / or substrate, thereby reducing / preventing the formation of oxides (e.g., aluminum oxide). In one embodiment, controlling the gas temperature may help control (e.g., minimize) the rate at which oxide formation occurs. Reducing the formation of oxides or other nonmetals is generally desirable when forming articles and / or support structures that contain metals that are readily oxidized at the printing temperature.

[0030] The liquid ejector jet 200 may have a defined internal volume, also referred to as an internal cavity, which holds the molten or liquid printing material 210 within its internal volume. The printing material 210 may be or contain metals, polymers, etc. For example, the printing material 210 may be or contain aluminum or an aluminum alloy, and may be introduced via a printing material supply unit or a printing material wire feed 208 (e.g., an aluminum or other metal wire). Certain embodiments may not utilize a wire feed introduction of the printing material, but may instead include a powder feed, a liquid feed, or other method or form for introducing the printing material into the liquid ejector jet 200.

[0031] The nozzle 202 of the liquid ejector jet 200 also defines a nozzle orifice 212. The printing material 210 held within the nozzle 202 is ejected through the nozzle orifice 212 in the form of one or more droplets 214. These droplets 214 of liquid printing material can be ejected onto a substrate such as a construction plate, a layer of previously ejected droplets, or both, forming one or more layers of solidified droplets 216 to ultimately form a 3D object.

[0032] Referring to Figure 3, in one embodiment of the present disclosure, an additive source 218 is in fluid communication with the nozzle 202. For example, this additive source 218 is coupled to the nozzle 202 of the liquid ejector jet 200 by an additive inlet 220. The additive inlet 220 delivers a reaction gas 222 from the additive source 218 to a gas shield 204, where the reaction gas 222 is combined with a first gas 206 and then carried toward the nozzle 202 and nozzle orifice 212, where the reaction gas 222 is brought close to the outer portion of the nozzle 202 and combined with modified droplets 214 of the liquid printing material 210. This process involves the interaction of the reaction gas 222 and the droplets 214 of the printing material through chemical or physical mixing or reaction, resulting in the formation of an in-situ modified printing material. This in-situ modified printing material may have a different composition from the original liquid printing material 210.

[0033] In one embodiment, the reaction gas 222 is mixed with the cover gas 206 and delivered to an area adjacent to the nozzle orifice 212 of the nozzle 202. In one embodiment, only a portion of the 3D printed part has droplets or already formed layers of printed material with in-situ modification of the molten or liquid printing material, forming shatterable material. For example, a portion of the printed material, such as the interface 140 or the entire support structure 138, can be formed as shatterable material.

[0034] In one embodiment, the shatterable material can be formed by exposing one or more of the printing materials before, after, or both of the deposition on the substrate. For example, exposure of the metal to the reaction gas can be performed during droplet deposition, after deposition of the metal layer, or both. By adding an oxygen-containing gas, which is the reaction gas 222, a metal oxide (e.g., aluminum oxide) can be formed as a shatterable material by oxidizing a formed or formed metal layer, such as a layer containing aluminum or an aluminum alloy, but not limited to this. By adding nitrogen, ammonia, or other nitrogen-containing gas to a nitride-forming alloy such as aluminum or an aluminum alloy, but not limited to this, a metal nitride (e.g., aluminum nitride (AlN)) or other potentially shatterable material can be formed. Similarly, a combination of oxygen-containing and nitrogen-containing gases can be used to form oxynitrides of metals such as aluminum oxynitride.

[0035] While the numerical ranges and parameters described in this disclosure are approximations, the numerical values ​​described in specific examples are reported as accurately as possible. However, any numerical value inherently contains certain errors that inevitably arise from the standard deviation observed in each test measurement. Furthermore, all ranges disclosed herein should be understood to encompass any and all subranges contained therein.

[0036] While this teaching is presented in relation to one or more implementations, modifications and / or alterations can be made to the exemplary embodiments without departing from the spirit and scope of the attached claims. In addition, certain features of this teaching may be disclosed in relation to only one of several implementations, but such features may be combined with one or more other features of other implementations as desired and advantageous for any given function or particular function. Furthermore, to the extent that the terms “including,” “includes,” “having,” “has,” and “with,” or their variations thereof, are used in any of the modes for carrying out the invention and in the claims, such terms are intended to be comprehensive in the same manner as the term “comprising.” Furthermore, the term “about” in the discussion and claims herein indicates that the enumerated values ​​may be modified to some extent, provided that the modifications do not result in process or structural incompatibility to the implementations shown. Finally, “exemplary” indicates that the descriptions are used as examples, not that they are ideal.

[0037] Other embodiments of this teaching may be apparent to those skilled in the art, taking into account this specification and the practices of this teaching disclosed herein. This specification and the examples are intended to be illustrative only, and the true scope and spirit of this teaching are set forth by the following claims.

Claims

1. 1. A method of additive manufacturing, comprising: i) forming a first layer comprising at least one material selected from an article material, a support structure material, and a crushable material; ii) forming an additional layer on the first layer, the additional layer comprising at least one material selected from the article material, the support structure material, and the crushable material; iii) repeating ii) one or more times to form a three-dimensional construct comprising an article and at least one support structure attached to the article at an interface, wherein the interface comprises the fractureable material formed between one or more of i), ii), or iii), wherein the fractureable material is formed by exposing a printing material to a reactive gas, wherein the fractureable material is a naturally occurring non-metallic material comprising an oxynitride of the article material, and wherein the reactive gas comprises a nitrogen-containing gas; A method comprising:

2. The method of claim 1 , wherein the article material is a metal.

3. The method of claim 2 wherein said reactive gas further comprises an oxygen-containing gas and said naturally occurring non-metal further comprises an oxide of said metal.

4. The method of claim 1 , wherein the support structure material and the article material are metallic and the crushable material is non-metallic in nature.

5. The method of claim 1 , wherein the article material is a metal, the crushable material is a non-metallic in nature, and the at least one support structure entirely comprises the non-metallic in nature.

6. 10. The method of claim 1, wherein the printing material is a liquid metal, and forming both the first layer and the additional layer comprises jetting the liquid metal onto a printing substrate in an ambient atmosphere, and wherein the ambient atmosphere comprises more than 10% by volume of the reactive gas when forming the friable material, and the ambient atmosphere comprises less than 10% by volume of the reactive gas when forming the article material.

7. The method of claim 1 , further comprising cooling the article and the at least one support structure without sintering the printed material.

8. 10. The method of claim 1, further comprising removing at least one support structure by fracturing the fracturable material at the interface, wherein the fracturing is performed without the use of a mechanical cutting device.

9. The method of claim 8 , wherein the fracturing is carried out using a technique selected from vibrating the support structure and contacting the support structure with a pressurized fluid.

10. 1. A method of additive manufacturing, comprising: i) ejecting droplets comprising a metal to form a first layer comprising at least one material selected from an article material, a support structure material, and a fracturable material; ii) ejecting additional droplets comprising the metal to form an additional layer on the first layer comprising at least one material selected from the article material, the support structure material, and the fracturable material; iii) repeating ii) one or more times to form a three-dimensional construct comprising an article and at least one support structure attached to the article at an interface, wherein the interface comprises a fractureable material formed between one or more of i), ii), or iii), wherein the fractureable material is formed by exposing portions of at least one form of metal selected from the droplets, the additional droplets, the first layer, and the additional layer to a reactive gas, wherein the fractureable material is a naturally occurring non-metallic material comprising an oxynitride of the article material, and wherein the reactive gas comprises a nitrogen-containing gas; A method comprising:

11. The method of claim 10 , wherein the reactive gas further comprises an oxygen-containing gas and the friable material further comprises an oxide of the metal.

12. The method of claim 10 , wherein the support structure material and the article material comprise the metal and the crushable material is non-metallic in nature.

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