Additive manufacturing system, article, and method of manufacturing an article

A method of additively manufacturing an article includes forming a first portion of the article by three-dimensional printing of a plurality of first layers from a first powder material cut having a first average particle size corresponding to a first feature resolution. The first layers have a first average layer thickness. The method also includes forming a second portion of the article by three-dimensional printing of a plurality of second layers from a second powder material cut having a second average particle size corresponding to a second feature resolution less than the first feature resolution. The second portion includes at least one feature. The second layers have a second average layer thickness less than the first average layer thickness. A three-dimensional printing system and an article formed from a powder material by three-dimensional printing are also disclosed.

FIELD OF THE INVENTION

The present embodiments are directed to methods, systems, and articles achieving high feature fidelity. More specifically, the present embodiments achieve high feature fidelity articles by additive manufacturing without subsequent machining.

BACKGROUND OF THE INVENTION

Three-dimensional (3D) printing is an additive manufacturing technique enabling creation of an article by forming successive layers of material under computer control to create a 3D structure. The process typically includes selectively heating portions of a layer of powder of the material to melt or sinter the powder to the previously-placed layers to form the article layer by layer. Plastic, ceramic, glass, and metal articles may be formed by 3D printing from powders of plastic, ceramic, glass, and metal, respectively. A 3D printer lays down powder material, and a focused energy source melts or sinters that powder material in certain predetermined locations based on a model from a computer-aided design (CAD) file. Heating methods include direct metal laser melting (DMLM), direct metal laser sintering (DMLS), selective laser melting (SLM), selective laser sintering (SLS), and electron beam melting (EBM). Once one layer is melted or sintered and formed, the 3D printer repeats the process by placing additional layers of material on top of the first layer or where otherwise instructed, one layer at a time, until the entire article is fabricated. 3D printing may be accomplished by powder bed processing or other methods of powder processing.

Metal 3D printing enables manufacturers to create end-use metal articles that often outperform those produced with traditional casting techniques. Once those articles are installed for end-use, they continue to save money because of their light weight, high strength, and precise fit. In conventional article manufacturing, however, achieving high feature fidelity in an article formed by 3D printing may be difficult, if not impossible, without machining the article after formation by printing. For metal articles having features with tolerances in the range of +/−25 μm (+/−1.0 mil), it is not conventionally possible to achieve such high feature fidelity by metal 3D printing alone. The current lower limit is about 76 μm (3.0 mil). In the current conventional metal 3D printers, a single powder hopper and a single powder cut (powder size distribution) is used. A conventional metal powder cut for DMLM has an average particle size of about 30 μm (about 1.2 mil), with the particle size distribution being in the range of about 10 μm to about 45 μm (about 0.4 to about 1.8 mil). Such metal powder cuts are appropriate for build layer thicknesses of about 50 μm (2.0 mil) or greater. In order to achieve tolerances below about 76 μm (3.0 mil) with such build layers, a machining step is required after the metal 3D printing.

Conventional ceramic powder cuts have an average particle size and a particle size distribution similar to conventional metal powder cuts.

BRIEF DESCRIPTION OF THE INVENTION

In an embodiment, a method of additively manufacturing an article includes forming a first portion of the article by three-dimensional printing of a plurality of first layers from a first powder material cut having a first average particle size corresponding to a first feature resolution. The first layers have a first average layer thickness. The method also includes forming a second portion of the article by three-dimensional printing of a plurality of second layers from a second powder material cut having a second average particle size corresponding to a second feature resolution less than the first feature resolution. The second portion includes at least one feature. The second layers have a second average layer thickness less than the first average layer thickness.

In another embodiment, a three-dimensional printing system includes a printing platform, a powder deposition assembly, and a focused energy source. The powder deposition assembly is configured to controllably and selectively provide a first powder material cut having a first average particle size corresponding to a first feature resolution or a second powder material cut having a second average particle size corresponding to a second feature resolution to the printing platform. The second average particle size is less than the first average particle size. The focused energy source is configured to supply heating energy to powder material on the printing platform.

In another embodiment, an article includes a first portion including a plurality of first layers from a first powder material cut having a first average particle size corresponding to a first feature resolution. The first layers have a first average layer thickness. The article also includes a second portion including a plurality of second layers from a second powder material cut having a second average particle size corresponding to a second feature resolution less than the first feature resolution. The second portion includes at least one feature. The second layers have a second average layer thickness less than the first average layer thickness.

DETAILED DESCRIPTION OF THE INVENTION

Provided are methods, systems, and articles achieving high feature fidelity by additive manufacturing without subsequent machining.

Embodiments of the present disclosure, for example, in comparison to concepts failing to include one or more of the features disclosed herein, achieve higher feature fidelity by additive manufacturing, achieve high feature fidelity by additive manufacturing without subsequent machining, eliminate machining in high feature fidelity formation, reduce manufacturing time for formation of high feature fidelity articles, reduce manufacturing cost for high feature fidelity articles, or combinations thereof.

In some embodiments, the high fidelity feature is formed from a powder cut having an average particle size of about 25 μm (about 1.0 mil), alternatively about 20 μm (about 0.8 mil), alternatively about 15 μm (about 0.6 mil), alternatively about 10 μm (about 0.4 mil), or any value therebetween.

In some embodiments, the high fidelity feature is formed from a powder cut having a particle size distribution in the range of about 10 μm to about 40 μm (about 0.4 mil to about 1.6 mil), alternatively in the range of about 10 μm to about 35 μm (about 0.4 mil to about 1.4 mil), alternatively in the range of about 10 μm to about 30 μm (about 0.4 mil to about 1.2 mil), alternatively in the range of about 10 μm to about 25 μm (about 0.4 mil to about 1.0 mil), alternatively in the range of about 10 μm to about 20 μm (about 0.4 mil to about 0.8 mil), alternatively in the range of about 5 μm to about 15 μm (about 0.2 mil to about 0.6 mil), or any range or sub-range therebetween.

Referring toFIG. 1, the additive manufacturing process may be performed with a 3D printing system400, where the powder deposition assembly500includes a first hopper501, a second hopper502, a powder delivery assembly401, and a focused energy source310. The powder delivery assembly401includes at least one powder material feeder405supplied with a first powder material cut301from the first hopper501or supplied with a second powder material cut302from the second hopper502. The powder material feeder405deposits and spreads the material of the first powder material cut301or the second powder material cut302across the surface406of the powder bed above the printing platform407as a new layer to be sintered or melted. The hoppers501,502may move with the powder material feeders405during deposition of the new layer or the hoppers501,502may alternatively be stationary within the 3D printing system400. Although two powder material feeders405are shown inFIG. 1, one for each hopper501,502, a single powder material feeder405may alternatively be used for both hoppers501,502, as shown inFIG. 2, since only one powder cut301,302is delivered at a time.

The 3D printing system400includes a focused energy source310to fuse powder plastic, powder metal, powder ceramic, or powder glass to form the article200. In some embodiments, the focused energy source310is a high power laser. In some embodiments, the high power laser is a carbon dioxide laser. In some embodiments, the focused energy beam409is a pulsed beam. The focused energy beam409is directed by a scanner320to selectively fuse powder material by scanning cross-sections generated from a 3D digital description, such as, for example, a CAD file or scan data, of the article200on the surface of a powder bed on a printing platform407. Before each cross-section is scanned, the powder bed is lowered by one layer thickness by actuating a fabrication piston420to lower the printing platform407and one of the powder material feeders405is actuated to deposit the material of the first powder material cut301from the first hopper501or to deposit the material of the second powder material cut302from the second hopper502as a new layer of powder material on top of the powder bed. The process is repeated until the article200is completed.

The article200being constructed is surrounded by un-sintered powder material at all times, which allows for the construction of previously-impossible geometries. The articles200being formed inFIG. 1andFIG. 2include two first portions210having a first layer thickness based on a first feature resolution separated by a second portion220having a second layer thickness based on a second feature resolution. The second portion220includes a feature230having a high fidelity.

FIG. 3shows a perspective view of an interior portion of an embodiment of a 3D printing system400such as those shown schematically inFIG. 1andFIG. 2. In addition to a printing platform407, a powder material feeder405, and a first hopper501, a control system505, a powder supply line510to the first hopper501and tracks520for translation of the powder material feeder405across the printing platform407are also visible. In some embodiments, the powder material feeder405shown inFIG. 3is referred to as a recorder.

FIG. 4shows a perspective view of an embodiment of a first hopper501, such as the first hopper shown inFIG. 1andFIG. 2. The control system505below the powder chamber of the first hopper501selectively permits the material of the first powder material cut301to leave the first hopper501and go into the powder material feeder405.

The 3D printing process may alternatively be performed with a 3D printing system400, where the powder deposition assembly500includes a first hopper501, a second hopper502, and a powder delivery assembly401, as shown inFIG. 5. The powder delivery assembly401includes at least one powder material feeder405supplied with a first powder material cut301from the first hopper501or supplied with a second powder material cut302from the second hopper502, and at least one spreader530spreading the material of the first powder material cut301or the second powder material cut302on the surface406as a layer across the top of the powder bed above the printing platform407as a new layer to be sintered or melted. At least one valve450selectively controls whether the first powder material cut301, the second powder material cut302, or no powder material is fed to the surface406.

Although two powder material feeders405, two valves450, and two spreaders530are shown inFIG. 5, one for each hopper501,502, a single powder material feeder405, a single valve450, and/or a single spreader530may alternatively be used for both hoppers501,502, since preferably only one powder cut301,302is delivered to the surface406at a time. The spreader530may be any device capable of moving powder material across the surface406to form a layer above the printing platform407. In some embodiments, the spreaders530are rollers. In some embodiments, the spreaders530are blades. Although the powder material feeders405are shown as depositing powder material on either side of the printing platform407, the first powder material cut301and the second powder material cut302may alternatively be deposited on the same side of the printing platform407or directly above the printing platform407.

The 3D printing process includes a focused energy source310to fuse powder plastic, powder metal, powder ceramic, or powder glass to form the article200. In some embodiments, the focused energy source310is a high power laser. In some embodiments, the high power laser is a carbon dioxide laser. In some embodiments, the focused energy beam409is a pulsed beam. The focused energy beam409is directed by a scanner320to selectively fuse powder material by scanning cross-sections generated from a 3D digital description, such as, for example, a CAD file or scan data, of the article200on the surface406of a powder bed on a printing platform407. Before each cross-section is scanned, the powder bed is lowered by one layer thickness by actuating a fabrication piston420to lower the printing platform407, the first powder material cut301from the first hopper501or the second powder material cut302from the second hopper502is directed onto the surface406in an amount of material that is about the equivalent of one layer thickness of the powder bed, and the spreader530applies the new material as a new layer on top of the powder bed by the spreader530. The process is repeated until the article200is completed.

The article200being constructed is surrounded by un-sintered powder material at all times, which allows for the construction of previously-impossible geometries. The article200being formed inFIG. 5includes two first portions210having a first layer thickness based on a first feature resolution separated by a second portion220having a second layer thickness based on a second feature resolution. The second portion220includes a feature230having a high fidelity.

FIG. 6schematically shows a model of an article200having a tubular geometry. The article200includes two first portions210having a first layer thickness based on a first feature resolution separated by a second portion220having a second layer thickness based on a second feature resolution. The second portion220includes at least one feature230having a high fidelity. The first layer thickness is about 50 μm (2 mil) and the second layer thickness is about 20 μm (0.8 mil).

FIG. 7shows a photograph of multiple articles200formed by 3D printing by a system disclosed herein. The articles200have a cylindrical geometry and include two first portions210having a first metal layer thickness based on a first feature resolution separated by a second portion220having a second metal layer thickness based on a second feature resolution. The first layer thickness is about 50 μm (2 mil) and the second layer thickness is about 20 μm (0.8 mil). As seen inFIG. 7, the first portions210have a different surface appearance than the second portion220, resulting from a greater surface roughness for the first portions210, with both portions210,220having a different surface texture and appearance than a machined surface.

FIG. 8shows an enlarged photograph of a feature230having a high fidelity in the second portion220with the second layer thickness. The feature230formed with a 20-μm (0.8 mil) build layer thickness has a higher feature fidelity than a feature formed with a 50-μm (2 mil) build layer thickness. Being able to use different size and distribution powder material for the same build job significantly improves the capability of metal 3D printing as a stand-alone manufacturing process, even beyond what conventional metal 3D printing in combination with machine finishing is able to achieve in some cases.

In some embodiments, movement of the printing platform407and/or the powder deposition assembly500of the 3D printing system400is controlled by software configured to automate the process and/or form the added material on the article200based upon a CAD model. In some embodiments, the process is an automated 3D printing process. In some embodiments, the relative movement of the printing platform407and/or the powder deposition assembly500provides a dimensional accuracy of at least +/−25 μm (+/−1 mil). Feedback sensors350evaluate the precision of the article200by measuring the actual dimensions of the deposited layers in comparison to the dimensions of the layer of the article200from the 3D CAD model.

In some embodiments, the powder material is a powder metal and the 3D printing is metal 3D printing. In some embodiments, the powder metal is a high-temperature superalloy. In some embodiments, the powder metal is an aluminum-based alloy, a titanium-based alloy, a steel-based alloy, a nickel-based superalloy, or a cobalt-based superalloy.

In some embodiments, the powder material is a powder ceramic and the 3D printing is ceramic 3D printing. The composition of the powder ceramic may include, but is not limited to, zirconia, silica, and alumina.

The method of manufacturing the article200may be by any additive manufacturing method or technique including melting or sintering layers of a powder material. In some embodiments, the 3D printing includes selective laser sintering (SLS), direct metal laser sintering (DMLS), selective laser melting (SLM), direct metal laser melting (DMLM), electron beam melting (EBM), powder bed processing, or combinations thereof. In some embodiments, the 3D printing includes SLS with a powder bed.

In some embodiments, the SLS process includes a focused energy source310to fuse powder plastic, powder metal, powder ceramic, or powder glass to form the article200. In some embodiments, the focused energy source310is a high power laser. In some embodiments, the high power laser is a carbon dioxide laser. In some embodiments, the focused energy beam409is a pulsed beam. The focused energy beam409selectively fuses powder material by scanning cross-sections generated from a 3D digital description, such as, for example, a CAD file or scan data, of the article200on the surface406of a powder bed on a printing platform407. After each cross-section is scanned, the powder bed is lowered by one layer thickness by lowering the printing platform407, a new layer of powder material is applied on top, and the process is repeated until the article200is completed.

In some embodiments, the DMLS process includes a focused energy source310firing into a bed of powder metal. In some embodiments, the focused energy source310is a ytterbium (Yb)-fiber laser, or more specifically a high-power 200-watt Yb-fiber optic laser. The focused energy source310is automatically fired at points in space defined by a 3D CAD model to heat the powder metal and sinter it to the article200being formed. In some embodiments, computer software on a computer directs the focused energy source310. Inside a build chamber area, the powder delivery assembly401includes a material dispensing platform dispensing the powder metal to a printing platform407and a recoater blade as the spreader530moving new powder material over the printing platform407. The article200is built up additively, layer by layer. In some embodiments, the layers of the added material are about 20 micrometers thick.

In some embodiments, the DMLM process is performed with a powder delivery assembly401including one or more powder material feeders405. During the DMLM process, the powder material feeders405selectively deliver the powder material and/or any other material directly as a new layer on the powder bed above the printing platform407or alternatively to the surface406, where at least one spreader530directs the powder material toward the printing platform407.

The relative movement of the printing platform407and/or the scanner320during the DMLM process may provide a dimensional accuracy of at least 25 μm (1 mil), at least 130 μm (5 mil), at least 250 μm (10 mil), between 25 μm and 250 μm (1 and 10 mil), between 25 μm and 130 μm (1 and 5 mil), or any combination, sub-combination, range, or sub-range thereof. Additionally, the DMLM process provides a fully dense metal in the article200formed therefrom.

Suitable focused energy sources310for the DMLM process include any focused energy source310operating in a power range and travel speed for melting a layer of the first powder material cut301or the second powder material cut302on the powder bed. In some embodiments, the focused energy source310is a laser. In one embodiment, the power range of the focused energy source310in the DMLM process includes, but is not limited to, between 100 and 3,000 watts, between 200 and 2,500 watts, between 300 and 2,000 watts, or any combination, sub-combination, range, or sub-range thereof. In another embodiment, the travel speed includes, but is not limited to, up to 300 mm/sec, between 1 and 300 mm/sec, between 4 and 250 mm/sec, or any combination, sub-combination, range, or sub-range thereof. For example, in a further embodiment, the focused energy source310operates in the power range of between 300 and 2,000 watts, at a travel speed of between 4 and 250 mm/sec. In another embodiment, a deposition rate for standard steels, titanium, and/or nickel alloys includes, for example, up to 1 kg/hour, up to 0.75 kg/hr, up to 0.5 kg/hour, between 0.1 and 0.5 kg/hour, up to 0.4 kg/hour, up to 0.3 kg/hour, or any combination, sub-combination, range, or sub-range thereof. The parameters of the focused energy source310and the deposition rate, however, may be adjusted and/or set depending on whether the first powder material cut301or the second powder material cut302is being supplied and/or on the layer thickness.

In some embodiments, the directing of the focused energy beam409includes moving the scanner320and/or the printing platform407relative to each other, the moving providing the shape and geometry of the added material on the article200. To provide relative movement, the printing platform407may be fixed and the scanner320may be adjusted, the scanner320may be fixed and the printing platform407may be moved, or both the scanner320and the printing platform407may be adjusted independently of each other. For example, in one embodiment, the printing platform407includes three or more axes of rotation for moving relative to the scanner320.

In some embodiments, the SLM process includes 3D CAD data as a digital information source and a focused energy source310. In some embodiments, the focused energy source310is a high-power (hundreds of watts) laser, and more specifically a Yb-fiber laser. The focused energy beam409melts a fine powder material to build the article200. The powder material is added layer-by-layer, the layers usually being about 20 μm to 100 μm (0.8 to 4 mil) in thickness. The focused energy beam409selectively melts thin layers of atomized fine powder material that are evenly distributed by a powder material feeder405onto the article200being formed. This occurs in a controlled inert-gas chamber. The inert gas is typically either argon or nitrogen with oxygen levels below 500 parts per million. The focused energy source310energy is intense enough to permit full melting of the powder material particles.

In some embodiments, the EBM process is similar to the SLM process, but an electron beam is used as the focused energy beam409rather than a laser beam. The EBM process may operate at higher temperatures, such as, for example, up to 1000° C. (1830° F.), and has the capability for higher pre-heats.

In some embodiments, the powder bed process includes a focused energy source310to fuse (e.g., sinter or melt) a powder material. The powder bed process builds up the added material200layer by layer from fine powders, typically about 5 μm to 50 μm (0.2 to 2 mil) in size. A powder bed system typically includes a powder supply, a printing platform407, a powder delivery assembly401including a powder material feeder405, a laser as the focused energy source310, and a laser directing system. The powder material feeder405spreads a thin layer of powder material on the powder bed on the printing platform407. The laser melts or sinters the powder material in locations where the build is to be made. The spreading and melting/sintering process is repeated as the article200is built layer-by-layer.

The selective control permits switching between the formation of a first layer thickness from the first powder material cut301and the formation of a second layer thickness from the second powder material cut302. In some embodiments, each layer is formed with only one of the two powder material cuts301,302to give a substantially uniform layer thickness. The first layer thickness and the second layer thickness are preferably in the range of about 10 μm to about 100 μm (0.4 mil to 4 mil). The first layer thickness may be at least about 40 μm (0.4 mil), alternatively in the range of about 40 μm to about 100 μm (2 mil to 4 mil), alternatively in the range of about 50 μm to about 80 μm (2 mil to 3.1 mil), alternatively in the range of about 50 μm to about 70 μm (0.4 mil to 2.8 mil), alternatively in the range of about 40 μm to about 60 μm (0.4 mil to 2.4 mil), or any range or sub-range therebetween. The second layer thickness may be less than or equal to about 25 (0.4 mil), alternatively in the range of about 10 μm to about 45 μm (0.4 mil to 1.8 mil), alternatively in the range of about 10 μm to about 35 μm (0.4 mil to 1.4 mil), alternatively in the range of about 10 μm to about 25 μm (0.4 mil to 1 mil), alternatively in the range of about 15 μm to about 25 μm (0.4 mil to 0.6 mil), or any range or sub-range therebetween.

A smaller build layer thickness and a smaller corresponding powder size and distribution are provided to achieve greater feature230fidelity. In some embodiments, the 3D printing system includes two powder hoppers501,502with two different powder sizes and distributions. The hopper502with powder metal having a finer size and distribution is preferably only used for very specific layers where high feature230fidelity is desired. These specific layers are preferably built at 20 μm (0.8 mil) or sub-20 μm (sub-0.8 mil) build layer thickness. All of the other build layers may have a thickness of 50 μm (2 mil) or higher as necessary or desirable.

In some embodiments, a single focused energy source310is used both for layers of the first powder material cut301and for layers of the second powder material cut302. The parameters of the focused energy source310and the deposition rate, however, may be adjusted and/or set depending on whether the first powder material cut301or the second powder material cut302is being supplied and/or on the layer thickness. The first powder material cut301is preferably used to quickly build first portions210of the article200, whereas the second powder material cut302is used to build second portions220of the article200where higher resolution is desired.

In some embodiments, the 3D printing system400is arranged and operates in a manner similar to the SLM 280 HL model selective laser melting system (SLM Solutions GmbH, Lubeck, Germany), except that the 3D printing system400includes two hoppers501,502holding two different powder cuts301,302and one, at least one, or two powder material feeders405to selectively supply powder material from the two hoppers501,502. In some embodiments, the 3D printing system400includes up to a 280 mm by 280 mm by365build envelope, up to two fiber lasers with 3D scanning optics, a build rate of up to 55 cm3/hr, or combinations thereof.

The 3D printing system400with two hoppers501,502holding two different powder cuts301,302and distributions permits variable build layer thickness and enables features230with finer fidelity. Larger powder size results in larger variations, making features230requiring 25 μm (+/−1 mil) tolerances impossible, since the powder diameter itself is close to 50 μm (2 mil). Lower tolerance is achieved by using a smaller build layer thickness and corresponding smaller powder particle size. Better fidelity of features230without compromising build rate is achieved by having two hoppers501,502supplying different powder material cuts301,302. The different powder material cuts301,302may be of the same powder composition or different powder compositions.

The article200may be any component requiring at least one feature230with high fidelity for at least a portion of the article200. In some embodiments, the article200is a hot gas path component of a turbine. In some embodiments, the article200is a gas turbine seal, a gas turbine combustion component, such as, for example, a fuel nozzle, or a gas turbine hot gas path component, such as, for example, a gas turbine shroud, a gas turbine nozzle, or a gas turbine blade.

In some embodiments, high fidelity is achieved with features230that would otherwise be difficult or impossible to machine. For example, fuel holes have very tight tolerances, and machining holes at difficult to reach locations is expensive. A high fidelity fuel hole in an as-built condition eliminates the machining problem and reduces manufacturing cost.

While the invention has been described with reference to one or more embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. In addition, all numerical values identified in the detailed description shall be interpreted as though the precise and approximate values are both expressly identified.