Method for multi-material laser powder bed fusion using a sacrificial adaptable platform

Abstract

A laser powder bed fusion method of forming a layer includes dispensing a sacrificial layer in a build zone, on a substrate or a previous layer of a build. The method includes forming first cavities in the sacrificial layer in the build zone, depositing a first metal powder in the first cavities, and using a laser to fuse the first metal powder in the first cavities. Any unmelted first metal powder that is outside the first cavities is removed from the build zone. The method further includes forming second cavities in the sacrificial layer only when the sacrificial layer is in the build zone, depositing a second metal powder in the second cavities, using the laser to fuse the second metal powder in the second cavities, and removing from the build zone any of the second metal powder that is outside the one or more second cavities.

Description

METHOD FOR MULTI-MATERIAL LASER POWDER BED FUSION USING A SACRIFICIAL ADAPTABLE PLATFORMRELATED APPLICATION

[0001] This application claims the benefit of priority to the Singapore patent application no. 10202402142T filed on July 18, 2024, the contents of which are hereby incorporated by reference in entirety for all purposes.TECHNICAL FIELD

[0002] The present disclosure relates to additive manufacturing and more specifically to laser powder bed fusion (LPBF) systems and methods.BACKGROUND

[0003] Conventional methods to produce a multi -material metal 3D-printed articles with LPBF often result in significant cross-contamination of the metal powder feedstock. The dispensed but unused powder feedstock of one metal material often cannot be simply returned to the dispenser as it would have been cross contaminated by powders of other metal materials. It is understandably costly and resource-intensive to purify the crosscontaminated powder feedstock. Conventionally, such cross-contaminated powder feedstock cannot be recycled or reused as its material composition would be unpredictable and too inconsistent from batch to batch.SUMMARY

[0004] A method is proposed herein, the method including: forming a layer, the forming of the layer including: dispensing a sacrificial layer in a build zone, the sacrificial layer being dispensed on a substrate or a previous layer of a build; using a laser to form one or more first cavities in the sacrificial layer, the one or more cavities being formed only when the sacrificial layer is in the build zone; depositing a first metal powder in the one or more first cavities; using the laser to fuse the first metal powder in the one or more first cavities; removing from the build zone any unmelted first metal powder that is outside the one or more first cavities; using the laser to form one or more second cavities in the sacrificial layer, the one or more second cavities being formed only when the sacrificial layer is in thebuild zone; depositing a second metal powder in the one or more second cavities; using the laser to fuse the second metal powder in the one or more second cavities; and removing from the build zone any of the second metal powder that is outside the one or more second cavities.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] To aid understanding, various embodiments of the present disclosure will be described with reference to the following figures:

[0006] FIG. 1 a schematic flowchart of a method of multi-material laser powder bed printing using sacrificial material according to embodiments of the present disclosure;

[0007] FIG. 2 is a schematic diagram of an apparatus capable of multi-material laser printing according to embodiments of the present disclosure;

[0008] FIG. 3 is a schematic diagram illustrating a fabricated multi-material article made using the method; and

[0009] FIG. 4 to FIG. 13 are schematic diagrams of the apparatus at various steps of the method.DETAILED DESCRIPTION

[0010] The following detailed description is made with reference to the accompanying drawings, showing details and embodiments of the present disclosure for the purposes of illustration. Features that are described in the context of an embodiment may correspondingly be applicable to the same or similar features in the other embodiments, even if not explicitly described in these other embodiments. Additions and / or combinations and / or alternatives as described for a feature in the context of an embodiment may correspondingly be applicable to the same or similar feature in the other embodiments.

[0011] The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. As used herein, the singular ‘a’ and ‘an’ may be construed as including the plural “one or more” unless apparent from the context to be otherwise. In the context of various embodiments, the articles “a”, “an” and “the” as used with regard to a feature or element include a reference to one or more of the features or elements.

[0012] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0013] In the context of various embodiments, the term “about” or “approximately” as applied to a numeric value encompasses the exact value and a reasonable variance as generally understood in the relevant technical field, e.g., within 10% of the specified value.

[0014] Terms such as “first” and “second” are used in the description and claims only for the sake of brevity and clarity, and do not necessarily imply a priority or order, unless required by the context.

[0015] Some methods may be described in terms of steps, stages, phases, or the like, merely to aid understanding and / or for convenient reference. The delineation between one step and another step may be merely for convenient reference in the present disclosure. It will be understood that in actual implementation there may not be a clear division or transition from one step to another subsequent step. There may be a certain amount of overlap among the steps and / or more than one step may occur or be performed concurrently in time, etc., unless the context dictates otherwise.

[0016] To address the issues noted above, a novel technique employing sacrificial material is proposed. The sacrificial material enables the formation of temporary cavities that can later be selectively filled with the intended alloys. This approach serves as a physical barrier, effectively preventing cross-contamination and overcoming current challenges in multi-material fabrication.

[0017] FIG. 1 is a schematic flow diagram illustrating a method 200 of using an adaptable sacrificial build platform to conduct multi-material laser printing according to embodiments of the present disclosure, solely to aid understanding. In one aspect, the method 200 includes a process of melting a powder feedstock with the aid of a laser such that upon cooling, the powder fuses to form an article. In another aspect, the method 200 may be described as an additive manufacturing method or 3D printing. As used herein, the terms “additive manufacturing”, “3D printing”, “laser powder bed fusion printing” and “laser printing” may be used interchangeably. Additive manufacturing or 3D printing refers to a technology where an article is formed by building layer by layer using various physical and / or chemical processes. A diverse range of materials may be used in AM, including polymers, metals, ceramics, and composites. Taking a type of 3D printing, e g., laser powder bed fusion (LPBF), for example, a metal powder is laid evenly on a build platform andmelted by a laser in a predetermined geometry. The melt would then solidify to form a physical slice of a three-dimensional article. This process of laying metal powder, melting through laser exposure, and solidification is then repeated layer-by-layer until the article is formed.

[0018] The method 200 includes iteratively forming one layer upon another layer until a predetermined article is formed. In the forming of one layer, the method 200 described herein is capable using different metal powders to form different parts of the same layer. In the forming of each multi-material metal 3D-printed layer, the method 200 includes a first stage 210 of sacrificial material deposition and a second stage 220 of selective deposition and melting of metal powders.

[0019] In one example, in each layer of the build, i.e., for each single layer that is to be formed from multiple or different metal powders, the method 200 may include performing the first stage 210 of sacrificial material deposition, and performing two or more rounds of the second stage 220 of selective deposition and melting of a plurality of metal powders, in which only one metal powder is selected (from a plurality of metal powders) and used in each round of the second stage 220. In the course of a build, if a layer is to be formed from one metal powder, the layer may be 3D printed in a conventional manner. Advantageously, the present method does not require a change of equipment to switch between 3D printing a single metal powder in a layer and 3D printing a plurality of metal powders in a subsequent layer, or vice versa.

[0020] In another example, if the layer is to be formed from multiple different metal powders, the method 200 may include, after a process start (step 201), performing the first stage 210 of sacrificial material deposition, and performing the second stage 220 of selective deposition and melting of one of a plurality of metal powders. The method 200 includes, after performing the second stage using a first metal powder, determining if the layer requires a different metal (e.g., a second metal powder) in the same layer, e.g., before moving on to form the next layer.

[0021] If it is determined that a different metal powder (e.g., the second metal powder) is required for the same layer, the method includes performing or repeating the second stage of selective deposition and melting with the different metal powder (the second metal powder) selected from the plurality of metal powders.

[0022] If it is determined that a first layer does not require a different metal and that the build is not completed (e.g., another layer is to be formed), the method includes performing the first stage 210 of sacrificial material deposition, followed by performing the second stage 220 of selective deposition and melting of metal powders, for a next layer (e g., a second layer). The second stage may be performed only once or repeatedly (multiple times), in which each round of the second stage uses a different metal powder selected from a plurality of metal powders.

[0023] If it is determined that the layer does not require a different metal and that the build is completed, the method 200 includes proceeding to the process end 250. Unpacking of the completed build from the 3D printing apparatus may be carried out.

[0024] According to various embodiments of the present disclosure, the first stage 210 or the stage of sacrificial material deposition includes a step 211 of dispensing a sacrificial material over a substrate. The term "dispensing" as used herein refers generally to providing a material. In some examples, a section of a sheet-like material may be dispensed from a roller in roll-to-roll step up. In other examples, an amount of material may be dispensed (e.g., extruded, ejected, fed) via a nozzle or nozzle-like tool. In the present disclosure, the term "disposing" and "dispensing" may also be interchangeably used unless dictated otherwise by the context. The step 211 may include moving the sacrificial material into a predetermined position relative to the substrate.

[0025] The first stage 210 or the stage of sacrificial material deposition may further include a step 212 of raising a substrate plate. Raising or elevating the substrate plate has an effect of applying the sacrificial material to the substrate or to the partially completed build.

[0026] The first stage 210 or the stage of sacrificial material deposition may further include a step 213 of performing laser ablation of a perimeter of the sacrificial material.

[0027] The first stage 210 or the stage of sacrificial material deposition may further include a step 214 of lowering the substrate platform.

[0028] The first stage 210 or the stage of sacrificial material deposition may further include a step 215 of moving away the sacrificial material dispensing mechanism away from the substrate.

[0029] The second stage 220 or the stage of selective deposition and melting of metal powders may include a step 221 of laser ablation of a geometry of material composition N in the sacrificial material, forming an ablated cavity (e.g., one or more first cavities).

[0030] The second stage 220 or the stage of selective deposition and melting of metal powders may include a step 222 of depositing the material of composition N (e.g., first metal powder) into the ablated cavity.

[0031] The second stage 220 or the stage of selective deposition and melting of metal powders may include a step 223 of laser melting of the material composition N and allowing the material to solidify.

[0032] If another material is to be formed in the same layer, the second stage 220 is repeated with another material, e.g., material composition N+l (e.g., second metal powder) and respective cavities (e.g., one or more second cavities). The one or more cavities (e.g., first cavities, second cavities, etc.) are formed in-situ (e.g., only when the sacrificial layer is in the build zone). After fusing the first metal powder in the one or more first cavities, any excess or unmelted first metal powder that is outside of the first cavities will be removed from the build zone. Similarly, after fusing the second metal powder in the one or more second cavities, any excess or unmelted second metal powder that is outside of the second cavities will be removed from the build zone

[0033] FIG. 2 schematically illustrates an apparatus 300 according to embodiments of the present disclosure. The apparatus 300 may include a laser 310. The apparatus 300 may include a sheet dispenser, also referred to herein as a sacrificial material (SM) dispenser 500. The apparatus 300 includes a multi chambered hopper, 600 and a re-coater device 340. The re-coater device 340 may include one or more re-coater blade 342. The apparatus 300 includes a build platform 350 (also referred to as a heatable build platform or a heated build platform). The build platform 350 provides one or more overflow collection chute 360. The apparatus 300 may be entirely housed in a build chamber.

[0034] In one aspect, the apparatus 300 is configured to enable performance of the method 200. In another aspect, the apparatus 300 enables laser printing of an article 400 using any combination of one or more materials. To aid understanding, a non-limiting example of the article 400 is schematically illustrated in FIG. 3. That is, the method 200 may be executed to make articles of various configurations, not limited to the example illustrated

[0035] The article 400 of the present disclosure can be formed of a plurality of different materials. The article 400 may be built by forming layers 402, one layer upon another layer, with any one or more of the plurality of materials may be disposed in a same layer. Forexample, one or more first parts 410 of the article 400 may be made of one metal material, and one or more second parts 420 of the article 400 may be made of another metal material. Yet another part 430 of the article 400 may be made of a different metal material. Another part 440 of the article 400 may be made of yet another metal material. The layers 402 may not be distinguishable in the completed article 400 and are schematically represented by way of dotted lines merely to aid understanding

[0036] For the sake of convenient reference and to aid understanding, the build platform 350 may define a first axis or a build axis 101 along which the layers may be built up. The apparatus 300 may be configured to enable displacement of the SM dispenser 500 and the hopper 600 along a second axis 102 that is perpendicularly oriented relative to the build axis 101 and a recoating axis 103.

[0037] FIG. 4 shows a step of dispensing a sacrificial layer 510 on the build platform 350. According to embodiments of the present disclosure, the sacrificial layer 510 includes a homogeneous sheet of a sacrificial material. For example, the sacrificial layer 510 is configured to be uniform in density and in surface topography. The sacrificial material is selected from materials that may be drawn into a sheet form of a thickness similar to a thickness of one layer of the build (also referred to as a “layer thickness”). In some examples, the sacrificial material is selected to be capable of being drawn into a thin sheet of uniform thickness. The sacrificial material is selected from materials capable of withstanding temperatures in the build chamber that may arise in the operation of the apparatus 300. The sacrificial material is selected from materials that can be formed into a sacrificial layer capable of adhering to itself and / or other surfaces by any one or more of a physical or chemical method. The sacrificial material is selected from materials that can be formed into a sacrificial layer capable of being removed or decoupled from the build platform and / or the build, e.g., after laser printing, by any one or more of a physical, chemical, or thermal method. For instance, when fabricating a combination of steel and copper on a mild steel base plate, a polymer based sacrificial material may be used The lower melting point of the polymer would allow a thermal based removal method in separating sacrificial material from the intended metallic components. The sacrificial material is selected from materials capable of forming a sacrificial layer with at least one smooth surface. The sacrificial material may be a polymer. Examples of the sacrificial material include but are not limited to polyamide.

[0038] Tn one example, a sacrificial material of polyamide (PT) may be selected for use in the method to make an article from stainless steel (SS) 316L and pure copper (Cu). After formation of a layer, any remaining sacrificial material may be removed by laser ablation before forming the next layer or before laying on a new layer of the sacrificial material.

[0039] FIG. 4 further shows the sacrificial material being dispensed on the build platform. For the sake of brevity, reference to the build platform in this context may refer to the sacrificial material being dispensed on the substrate. In some examples, an individual sheet of the sacrificial material may be dispensed on the build platform or on a previously formed layer of the build. For the sake of brevity, the following description will refer to a “previous layer”, which may be understood to refer to a previously formed layer of the build, or to the substrate in a case where the layer being formed is the first layer.

[0040] In some examples, the sacrificial material may be dispensed from a roll-to-roll assembly 520. For example, in some embodiments, the SM dispenser 500 includes a roll- to-roll assembly 520. The roll-to-roll assembly 520 may include a dispensing roller 521 and a collection roller 522. A roll of the sacrificial material may be extended between the dispensing roller 521 and the collection roller 522 to provide a substantially flat or planar area of the sacrificial material. The roll-to-roll assembly 520 may be displaced along the second axis 102 until the substantially flat or planar area of the sacrificial material is aligned with the build platform along the first axis 101. The roll-to-roll assembly 520 advantageously enables a quick application of a flat and uniform surface with the sacrificial layer 510 being capable of serving both as a support layer and as a mask.

[0041] FIG. 5 shows the sacrificial layer 510 being defined and adhered to the previous layer. At the same time, the rest of the sacrificial material provided by the roll-to-roll assembly 520 remains supported by the roll-to-roll assembly 520. At this step, the sacrificial material dispenser 500 or the roll-to-roll assembly 520 may be described as being in a SM dispensing position 502 relative to the build platform 350. For the sake of brevity, the space at or above the build platform 350 may also be referred to in the present disclosure as a build zone. In the SM dispensing position, 502, the roll-to-roll assembly 520 is positioned to feed or provide a flat area of the sacrificial material in the build zone so that a part of the sacrificial material can be coupled with the previous layer.

[0042] FIG. 6 shows that, with the sacrificial layer 510 being coupled with or adhered to the previous layer, the rest of the sheet of sacrificial material (or the rest of the flat areaof the sacrificial material) is physically displaced along the build axis or the first axis 101 until the unadhered part of the sacrificial material is clear of the build zone.

[0043] In other words, after the sacrificial layer 510 is applied and adhered to the previous layer, the SM dispenser 500 may be displaced away from the build platform 350. As illustrated in FIG. 7, the roll-to-roll assembly 520 is at least displaced transversely (e.g., sideways along the second axis 102) until the roll-to-roll assembly 520 is positioned in a non-SM dispensing position 501, transversely spaced apart from the build zone or the build platform 350. For example, the roll-to-roll assembly 520 in the non-SM dispensing position 501 leaves the space above the build platform clear of obstruction to the laser 310 or the hopper 600. The sacrificial layer 510, or the flat layer of the sacrificial material covering the previous layer is exposed for further processing. At this step, the sacrificial layer 510 covers the entire area of the previous layer of the build.

[0044] As illustrated in FIG. 8, one or more selected areas of the sacrificial layer 510 is exposed to laser irradiation according to the slice geometry of a first material. One or more parts of the sacrificial layer 510 is burnt away (e g., by the laser irradiation) to correspondingly produce one or more “cut-outs” or cavities 550. In other words, a first set of one or more cavities 550 may be formed in the sacrificial layer 510. In this example, a first cavity 551 or a first opening is formed in the sacrificial layer 10. In other words, the method 200 includes forming a mask “in-situ” in the build zone itself. The mask is formed by selective laser irradiation of the sacrificial layer 510 after disposing the sacrificial material on the previous layer.

[0045] As illustrated in FIG. 9, the hopper 600 may be displaced along a third axis 103 until the hopper 600 is above the build platform 350 or in the build zone. The hopper 600 is controllably operated to dispense a first metal powder in the one or more cavities 550 which have been formed at this step. In the example illustrated, the apparatus 300 is configured so that the hopper 600 can be moved along the third axis 103 in a direction that is normal to the first axis 101 and the second axis 102. The hopper 600 is controlled to dispense one type of metal powder in the first cavity 551.

[0046] Any excess of the first metal powder that is not deposited inside the first cavity 551 is swept by the re-coater blade 342 into an overflow collection chute 360. At this step, there is only one type of metal powder on the build platform. The first metal powdercollected in the overflow collection chute 360 is essentially free of cross-contamination from the other metal powders.

[0047] After dispensing the first metal powder, the hopper 600 is displaced away from the build zone.

[0048] The laser 10 is used to irradiate the first metal powder deposited in the first cavity 551 to fuse the first metal powder and form a solidified part 410 of the layer from the first metal powder.

[0049] As illustrated schematically in FIG. 10, the laser 310 is then used to form one or more cavities (e.g., second cavity 552) to receive a second metal powder. For example, a second set of one or more cavities may be formed in the sacrificial layer 510. The method 200 includes configuring (or re-configuring) the mask (i.e., the sacrificial layer 510) in-situ repeatedly, in which each configuration (or re-configuration) is performed before deposition of a different metal powder. As the sacrificial layer 510 was disposed and adhered to the previous layer before the first configuration (forming of one or more of the first cavities 551 ), there is no gap between the sacrificial layer and the build, eliminating the risk of metal powders being trapped under a mask and cross-contaminating subsequently deposited metal powders.

[0050] After the sacrificial layer 510 is re-configured to serve as a mask for a second metal material, the hopper 600 is displaced to the build zone. The hopper 600 may be controllab ly operated to dispense a second metal powder into the second cavity 552. Excess amount of the second metal powder may be swept by the re-coater blade 342 into another overflow collection chute 360. In this step, the only loose powder present on the build platform would be the second metal powder. The second metal powder collected by the overflow collection chute 360 in this step would essentially be composed of the second metal powder with negligible or no cross-contamination by the first metal powder.

[0051] As illustrated schematically in FIG. 11, the hopper 600 may traverse in opposite directions along a third axis 103 in sequential dispensation of the respective metal powders. After the second metal powder has been dispensed and excess metal powder collected, the laser 310 can be used to irradiate the second metal powder to form a solid part of the layer from the second metal powder.

[0052] The steps may be repeated for the next metal powder until all the different materials are printed for this layer (FIG. 12). Cross contamination is prevented as a laserspot size that ranges from 120 pm to 60 pm will not melt unused metal powders or the surfaces of formed metal parts. Coupled with the cleaning step before a second alloy is deposited, two powder alloys are prevented from coming into contact with one another. Before printing the next layer, any remaining part of the sacrificial layer 510 may be removed in-situ, e.g., the remaining part of the sacrificial layer may be removed from the build without uninstalling the build from the build platform. In some examples, optionally, one or more parts of the sacrificial layer 510 may be used as a support layer.

[0053] The steps above may be repeated for each of the remaining layers. For example, to make a new layer of the build, the roll-to-roll assembly 520 may be operated to dispense, expose, or otherwise provide a new planar area of the sacrificial material. The roll-to-roll assembly 520 may be again displaced and positioned in the SM-dispensing position (FIG. 4). A new sacrificial layer 510 may be formed (FIG. 5 and FIG. 6). The roll-to-roll assembly 520 may be moved back to its non-SM dispensing position (FIG. 7). The laser 310 may be used to create one or more cavities in the sacrificial layer 510 (e.g., FIG. 8 and FIG. 10). The hopper 600 may be moved into the build zone to dispense or deposit powders of one metal material into the one or more cavities in the sacrificial layer 510 (e.g., FIG. 11 and FIG. 12)

[0054] During the deposition process, powders may be spread over the sacrificial material layer (e.g., if a re-coater arm is used). The re-coater arm 352 may be operated to push unmeted and excessive powder out of the build area, e.g., into a designated overflow collection chute 360. To avoid obfuscation, the apparatus 300 is drawn with two overflow collection chutes 360. In some embodiments, a hopper 600 with five compartments may be used with a build platform 350 that has correspondingly five distinct overflow collection chutes 360. As illustrated in the simplified example of FIG. 2, the plurality of overflow collection chutes is distributed outside the perimeter of the sacrificial layer 510 or the build, with the overflow collection chutes 360 being circumferentially distributed and spaced apart from one another. For example, the build platform 350 may include separate overflow collection chutes for each of the types of powders. The re-coater blade 342 may be operated to sweep off the excess powder into a different overflow collection chute for each type of powder. For example, the overflow collection chutes may be positioned with only one of the overflow collection chutes opened at any one time to receive the excess powder.Advantageously, any cross-contamination of the powders is minimal or negligible such that future recycling of the collected powders is made possible.

[0055] In some embodiments, the method 200 may include a step of removing excess first metal powder from the build zone using a first re-coater blade. For example, the first re-coater blade may be operated to push first metal powder in a first removal direction across a surface of the sacrificial layer into a first overflow collection chute. As the first re-coater blade is moved across the surface of the sacrificial layer, only the first metal powder that is not in the one or more first cavities would be displaced and swept into the first overflow collection chute.

[0056] The method may further include a later step of removing the second metal powder from the build zone. The second re-coater blade may be operated to push excess second metal powder in a second removal direction across the surface of the sacrificial layer in a second overflow collection chute. As the second re-coater blade is moved across the surface of the sacrificial layer, only the second metal powder that is not in the one or more second cavities would be displaced and swept into the second overflow collection chute.

[0057] The first removal direction and the second removal direction are different from one another. If there are more than two types of powders (or powder mixtures) used, a corresponding number of re-coater blades and overflow collection chutes will be provided. For example, each type of powder or powder mixture will come into contact with only one of a plurality of re-coater blades, and each type or powder or powder mixture will be removed to a separate overflow collection chute.

[0058] Steps of the method 200 may be executed until the entire three-dimensional geometry of the article (e.g., FIG. 3) has been formed (FIG. 13).

[0059] At the end of the build process, the build platform 350 may be raised to reveal or expose the article consolidating multiple materials. The 3D printed article 400 may be surrounded or partially encased in the sacrificial material that was applied at every layer that requires masking (e.g., FIG. 13). Extraction of the article requires removal of the surrounding sacrificial material, either through physical, thermal, or chemical methods. For example, the surrounding sacrificial material may be removed by laser ablation. At the end of the sacrificial material removal process, there should no longer be any residue on the printed part, and appropriate methods (such as washing in a solvent) may be used to produce the article (e.g., FIG. 3).

[0060] Advantageously, various embodiments of the apparatus 300 may be built by retrofitting a conventional laser powder bed fusion (LPBF) system.

[0061] There are numerous industrial goods that incorporate parts of different materials. For example, a heat exchanger may include an interior system of copper tubes (for thermal conductivity) and a steel exterior (for load-bearing capabilities). Conventionally, the copper tubes and the steel exterior are manufactured separately before they are assembled, which places constraints on the dimensions and geometries of the copper tubes and the steel exterior. It can thus be appreciated that the method 200 is useful for maintaining part quality, efficiency, and economic feasibility, and can find numerous practical applications in the making of industrially-useful articles and consumer items. Advantageously, the apparatus 300 can be used to 3D print a multi -material article with multiple materials and functional gradients in a single build. Eliminating the need for multiple builds to make one 3D print multi-material part would address inherent precision and efficiency issues of some conventional processes. Articles integrating various different metal materials may be made using the proposed method of adaptable multi -material laser printing

[0062] Advantageously, the method 200 can achieve the good surface finish and geometrical precision of conventional LPBF-fabricated parts. The method 200 can thus provide a viable (or a preferred) alternative to conventional methods such as the directed energy deposition (DED) method, especially for precision engineering parts.

[0063] The method 200 enables the unused portions of respective powder feedstock of the respective materials to be maintained in a pristine state in which there is little or minimal cross-contamination of the powder feedstock. According to various embodiments of the present disclosure, the hopper 600 is configured to provide separate deposition mechanisms for each powder material. As a result, there is minimal or negligible mixing of metal powders throughout the entire deposition and printing process. In some examples, the hopper 600 includes a plurality of compartments, each with its own delivery nozzle. For example, in a step to deposit a first metal powder, only a first delivery nozzle of the hopper 600 is opened, and only a first metal powder stored in a first compartment of the hopper 600 is delivered to the build via the first delivery nozzle. In a step to deposit a second metal powder, the first delivery nozzle is not opened and only a second delivery nozzle is opened. The only powder delivered to the build is the second metal powder stored in a second compartment of the hopper 600, which is delivered to the build via the second deliverynozzle. Tn some embodiments, the hopper 600 may include one or more re-coater blades to aid in delivering metal powder to the respective one or more cavities. In some embodiments, the hopper 600 may include an ultrasonic nozzle to aid in delivering metal powder to the respective one or more cavities. In some embodiments, the hopper 600 may include five or more compartments, each of the compartments being used for one type of powder. In some applications, a compartment of the hopper 600 may hold a pre-mix or a powder mixture. Advantageously, the hopper with multiple compartments and multiple corresponding delivery nozzles enables printing of a wide range of materials, including but not limited to high-entropy alloys.

[0064] Advantageously, the method 200 can be used to form functional gradients. The term “functional gradients” as used in the present disclosure refers to a physical part having a spatial variation in material composition as such that the part is characterized by specific functional properties. Unlike conventional multi-material parts where distinct material interfaces result in abrupt transitions, a functionally graded material enables a smooth and continuous transformation between different alloy compositions. This gradient minimizes discontinuities and enhances performance by tailoring properties throughout the component. Functional properties may include but are not limited to thermal properties, magnetic properties, structural strength, toughness, wettability, etc. The method 200 having the capability to deposit multiple materials within the same layer, functional gradients can be printed by using selective deposition methods (such as ultrasonic nozzle) to deposit and mix metal powders in the cavities formed in the sacrificial layer 510. Alternatively, provision of pre-mixed powders in the (compartmentalized) hopper 600 can also achieve functional graded printing. In one example, mixtures of a first metal powder and a second metal powder are provided in different ratios in each of the compartments of the hopper 600. For example, the first metal powder and the second metal powder may be mixtures of similar materials in different ratios. For example, a step of printing a first section using a first powder mixture having M1 :M2 of 1: 2 (in which Ml and M2 are two different metal materials) may be followed by a step of printing a second section immediately adjacent to the first section. The second section is printed using a second powder mixture having Ml :M2 of 1 :3. The step of printing the second section may be followed by printing a third section having Ml :M2 of 1 :5, in which the third section is immediately adjacent to the second section. The resulting part is characterized by a functional gradient in the material composition of M1 :M2. Theuse of multiple materials may be integrated with laser configurations (e g., laser scanning strategy, scanning parameters, etc.) to enable the 3D printing of the target functional gradients.

[0065] The method 200 brings significant improvements over conventional methods, particularly in the aspects of powder recyclability and sustainability. The method 200 enables minimal cross-contamination of metal powders throughout the entire printing process. This eliminates the need to conduct resource-intensive powder separation techniques and improves the recyclability of the metal powders used, which in turn represents significant cost reduction and sustainability of the process. Advantageously, the amount of powder used will be close to the final volume of the part, making significant improvements towards achieving close-to-zero wastage of raw materials. Material usage is no longer limited by powder recycling methods. For example, the metal powders selected are no longer limited to one magnetic powder and one non-magnetic powder solely to enable separation of cross-contaminated powders using a magnet. The range of potential applications is therefore significantly broader as more material combinations can be used with the method 200 without regard to the magnetic / non-magnetic nature of the metal powders. As mentioned above, it was additionally found that the method 200 can produce multi-material / functional graded parts with high surface quality and part density that compare favorably to parts made by DED.

[0066] According to various embodiments of the present disclosure, the proposed method includes: forming a layer, the forming of the layer including: dispensing a sacrificial layer in a build zone, the sacrificial layer being dispensed on a substrate or a previous layer of a build, using a laser to form one or more first cavities in the sacrificial layer, the one or more cavities being formed only when the sacrificial layer is in the build zone; depositing a first metal powder in the one or more first cavities; using the laser to fuse the first metal powder in the one or more first cavities; removing from the build zone any unmelted first metal powder that is outside the one or more first cavities; using the laser to form one or more second cavities in the sacrificial layer, the one or more second cavities being formed only when the sacrificial layer is in the build zone; depositing a second metal powder in the one or more second cavities; using the laser to fuse the second metal powder in the one or more second cavities; and removing from the build zone any of the second metal powder that is outside the one or more second cavities.

[0067] The depositing of the first metal powder and depositing of the second metal powder may include dispensing the first metal powder and the second metal powder from a hopper.

[0068] The disposing of the sacrificial layer in the build zone may include: dispending a planar area of a sacrificial material using a roll-to-roll mechanism; adhering the planar area of the sacrificial material to the substrate or the previous layer of the build; and laser cutting to form a sacrificial layer, the laser cutting being made along a perimeter of an adhered planar area of the sacrificial material, wherein the sacrificial layer covers an entirety of the substrate or the previous layer of the build.

[0069] The laser cutting to form the sacrificial layer may be performed before the using of the laser to form one or more first cavities in the sacrificial layer.

[0070] The sacrificial layer may have a thickness similar to a layer thickness of the build.

[0071] The depositing of the first metal powder in the one or more first cavities may include dispensing the first metal powder from a first compartment of a hopper.

[0072] The depositing of the second metal powder in the one or more second cavities may include dispensing the second metal powder from a second compartment of a hopper.

[0073] The hopper may include a plurality of compartments, in which the hopper is controllably operated to dispense from only one of the plurality of compartments at any one time.

[0074] The removing of the first metal powder from the build zone may include using a first re-coater blade to push the first metal powder in a first removal direction across a surface of the sacrificial layer into a first overflow collection chute.

[0075] The second metal powder from the build zone may include using a second recoater blade to push the second metal powder in a second removal direction across the surface of the sacrificial layer in a second overflow collection chute.

[0076] The first removal direction and the second removal direction may be different from one another, in which the first overflow collection chute and the second overflow collection chute are spaced apart from one another.

[0077] The first metal powder and the second metal powder may be mixtures of similar materials in different ratios, in which the method produces an article characterized by a functional gradient.

[0078] The sacrificial material may be a polymer.

[0079] The method may further include: forming a second layer including: dispensing a second sacrificial layer in the build zone, the sacrificial layer being disposed on the layer, using the laser to form one or more third cavities in the second sacrificial layer, the one or more third cavities being formed only when the second sacrificial layer is in the build zone; depositing a third metal powder in the one or more third cavities, in which any third metal powder not deposited in the one or more third cavities is removed to a third overflow collection chute, and using the laser to fuse the third metal powder in the one or more third cavities.

[0080] The method may further include removing the sacrificial layer from a completed article.

[0081] All examples described herein, whether of apparatus, methods, materials, or products, are presented for the purpose of illustration and to aid understanding and are not intended to be limiting or exhaustive. Modifications may be made by one of ordinary skill in the art without departing from the scope of the claimed invention.

Claims

CLAIMS1. A method comprising: forming a layer, the forming of the layer including: dispensing a sacrificial layer in a build zone, the sacrificial layer being dispensed on a substrate or a previous layer of a build; using a laser to form one or more first cavities in the sacrificial layer, the one or more cavities being formed only when the sacrificial layer is in the build zone; depositing a first metal powder in the one or more first cavities; using the laser to fuse the first metal powder in the one or more first cavities; removing from the build zone any unmelted first metal powder that is outside the one or more first cavities, using the laser to form one or more second cavities in the sacrificial layer, the one or more second cavities being formed only when the sacrificial layer is in the build zone; depositing a second metal powder in the one or more second cavities; using the laser to fuse the second metal powder in the one or more second cavities; and removing from the build zone any of the second metal powder that is outside the one or more second cavities.

2. The method as recited in claim 1, wherein the depositing of the first metal powder and depositing of the second metal powder comprises dispensing the first metal powder and the second metal powder from a hopper.

3. The method as recited in claim 1 or claim 2, wherein the disposing of the sacrificial layer in the build zone comprises: dispending a planar area of a sacrificial material using a roll-to-roll mechanism; adhering the planar area of the sacrificial material to the substrate or the previous layer of the build; and laser cutting to form a sacrificial layer, the laser cutting being made along a perimeter of an adhered planar area of the sacrificial material, wherein the sacrificial layer covers an entirety of the substrate or the previous layer of the build.

4. The method as recited in claim 3, wherein the laser cutting to form the sacrificial layer is performed before the using of the laser to form one or more first cavities in the sacrificial layer.

5. The method as recited in any one of claims 1 to 4, wherein the sacrificial layer has a thickness similar to a layer thickness of the build6. The method as recited in claim 2, wherein the depositing of the first metal powder in the one or more first cavities comprises dispensing the first metal powder from a first compartment of a hopper.

7. The method as recited in claim 6, wherein the depositing of the second metal powder in the one or more second cavities comprises dispensing the second metal powder from a second compartment of a hopper.

8. The method as recited in claim 2, wherein the hopper comprises a plurality of compartments, and wherein the hopper is controllably operated to dispense from only one of the plurality of compartments at any one time.

9. The method as recited in any one of claims 1 to 8, wherein the removing of the first metal powder from the build zone comprises using a first re-coater blade to push the first metal powder in a first removal direction across a surface of the sacrificial layer into a first overflow collection chute.

10. The method as recited in claim 9, wherein the removing of the second metal powder from the build zone comprises using a second re-coater blade to push the second metal powder in a second removal direction across the surface of the sacrificial layer in a second overflow collection chute.

11. The method as recited in claim 10, wherein the first removal direction and the second removal direction are different from one another, and wherein the first overflow collection chute and the second overflow collection chute are spaced apart from one another.

12. The method as recited in any one of claims 1 to 11, wherein the first metal powder and the second metal powder are mixtures of similar materials in different ratios, and wherein the method produces an article characterized by a functional gradient.

13. The method as recited in any one of claims 1 to 12, wherein the sacrificial material is a polymer.

14. The method as recited in any one of claims 1 to 13, further comprising: forming a second layer including: dispensing a second sacrificial layer in the build zone, the sacrificial layer being disposed on the layer; using the laser to form one or more third cavities in the second sacrificial layer, the one or more third cavities being formed only when the second sacrificial layer is in the build zone; depositing a third metal powder in the one or more third cavities, in which any third metal powder not deposited in the one or more third cavities is removed to a third overflow collection chute; and using the laser to fuse the third metal powder in the one or more third cavities.

15. The method as recited in claim 14, further comprising: removing the sacrificial layer from a completed article.

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