Patent Description:
Gas turbine engine components, such as turbine airfoils, are frequently manufactured using an investment casting process in which molten metal alloy is introduced into a mold cavity defined between a shell and a core and allowed to solidify, forming a completed casting. Depending on the application, the components, such as turbine blades and/or stator vanes, may be required to withstand thermal stresses due to high temperatures and large temperature fluctuations, as well as forces due to high rotational speeds experienced during normal operations of the gas turbine engine. Accordingly, the components may include complex internal cooling passages.

Conventional techniques for manufacturing engine parts and components may, for example, involve investment or lost-wax casting. Using such techniques, a mold and a core may be separately manufactured using known techniques. However, such techniques may be time-consuming and/or may limit the resolution of the mold and/or core. The limited resolution may result in a decreased ability to develop fine-detail cast features in the end product of the casting process.

Documents <CIT> and <CIT> disclose exemplary methods for casting components using additively manufactured unitary core-shell moulds.

Thus, the art is continuously seeking new and improved systems and methods that address the aforementioned issues. As such, the present disclosure is directed to methods for casting a component utilizing an additively manufactured mold.

In one aspect, the present disclosure is directed to a method for casting a component according to claim <NUM>.

In an additional aspect, the present disclosure is directed to a method for fabricating a unitary core-shell according to claim <NUM>.

<FIG>, <FIG>, <FIG> and <FIG> disclose embodiments of the invention within the scope of the claims.

In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope of the invention, as defined by the appended claims.

In general, the present subject matter is directed to a method for forming a cast component. In particular, the present subject matter is directed to the leveraging of multiple benefits that may be obtained via the utilization of an additively manufactured unitary core-shell mold. For example, the utilization of additive manufacturing techniques may facilitate the casting of fine details and/or structures that may not be obtainable via conventional casting methods. For example, additively manufacturing a core mold for a component (e.g., turbine blade) of a gas turbine engine may facilitate the forming of more intricate cooling passages than may be obtainable using conventional casting methods.

Although the utilization of additive manufacturing as described may be beneficial with regard to the structure of the cast component, the material cost and/or printing time associated with the process may be inconsistent with other production priorities. Accordingly, it may be desirable to minimize printing time and/or the amount of material required to form the mold. An approach to minimizing both the printing time and/or the material requirements of the mold formation, may include printing a unitary core-shell mold and/or minimizing the thicknesses of the walls of the mold. As such, rather than printing walls having a unitary thickness capable of resisting the maximal possible load (e.g., a stress concentration) experienced by the mold during the casting process, the walls may be formed with a thickness having a load limit that is less than a maximal load. For example, the walls may be formed with a load limit capable of resisting the average load projected to be experienced by the walls during the casting process, rather than the load of the stress concentration. Thus, it may be desirable to support the portions of the unitary core-shell mold that may be susceptible to stress concentrations rather than increasing the overall wall thicknesses of the unitary core-shell mold.

In order to realize the benefits of casting via an additively manufactured mold while also satisfying other production priorities, the component may be cast utilizing the methods disclosed herein. For example, the methods include receiving data indicative of at least one location of an unitary core-shell mold that may be susceptible to a stress concentration whenever the mold is employed to cast the component. Based on this data, the unitary core-shell mold is formed via an additive manufacturing process. The unitary core-shell mold defines a casting cavity that defines both an outer component shape and an inner component shape. Specifically, the unitary core-shell mold includes a shell wall that defines the outer component shape. The unitary core-shell mold also includes a core wall that is positioned inward of the shell wall and defines the inner component shape. Additionally, the shell wall and/or the core wall defines at least one reinforcement recess adjacent to the indicated location that is susceptible to the stress concentration. Once the unitary core-shell mold is formed, at least one support member is positioned within the reinforcement recess(es) and in contact with the indicated location. It should be appreciated that the support member(s) may facilitate the resisting of the stress concentration and thereby preclude a failure of the unitary core-shell mold during a casting process. Once the support member(s) is positioned within the unitary core-shell mold, the component material (e.g., molten metal) is introduced (e.g., poured) into the unitary core-shell mold to cast the cast component within the casting cavity.

Referring now to the drawings, <FIG> illustrates a cross-sectional view of one embodiment of a gas turbine engine <NUM> that may be utilized with an aircraft in accordance with aspects of the present subject matter. Various components of the gas turbine engine <NUM> may be formed via the methods for casting a component disclosed herein. The engine <NUM> is shown having a longitudinal or axial centerline axis <NUM> extending therethrough for reference purposes. The engine <NUM> will be discussed in detail below. Although shown as a turbofan jet engine, the methods described herein may be used on any turbomachine including, but not limited to, high-bypass turbofan engines, low-bypass turbofan engines, turbojet engines, turboprop engines, turboshaft engines, propfan engines, and so forth. The turbomachine may be configured in any suitable manner, such as for vehicle propulsion or ground-based power production.

Various embodiments of a method <NUM>, and aspects thereof, for forming a cast component are depicted in <FIG>. The reinforcement recesses <NUM> and support members <NUM> disclosed in <FIG> and <FIG> are outside the scope of the claims, as they do not comprise a curved section. The cast component may, for example, be a component of the gas turbine engine <NUM>, such as turbine blades and/or stator vanes. Additionally, in an embodiment, the cast component may be formed with a plurality of internal passageways (e.g., cooling passages) that may intersect with an outer surface of the cast component.

In an embodiment, and as particularly shown in <FIG>, the cast component may be formed, at least in part, via a casting process wherein a component material <NUM> in liquid form is introduced into a unitary core-shell mold <NUM>. For example, in an embodiment, a molten superalloy metal may be poured into the unitary core-shell mold <NUM>. The molten superalloy may include stainless steel, aluminum, titanium, Inconel <NUM>, Inconel <NUM>, Inconel <NUM>, a cobalt-chromium, nickel and/or any alloy thereof, such as nickel superalloys, and/or nickel superalloy single crystal alloys.

The method <NUM> may, in an embodiment, include receiving data indicative of at least one location <NUM> of the unitary core-shell mold <NUM> that is susceptible to a corresponding stress concentration <NUM> (<FIG>) when the unitary core-shell mold <NUM> is employed to cast the component. As depicted at <NUM> (<FIG>), the method <NUM> may form, via an additive manufacturing process, the unitary core-shell mold <NUM> defining a casting cavity <NUM>. With continued reference particularly to <FIG>, the unitary core-shell mold <NUM> may include a shell wall <NUM> that defines an outer component shape. The unitary core-shell mold <NUM> may also include a core wall <NUM> that may be positioned inward of a shell wall <NUM>. The core wall <NUM> may define an inner component shape. The shell wall <NUM> and/or the core wall <NUM> may define at least one reinforcement recess <NUM> adjacent to the location(s) <NUM> that is susceptible to the stress concentration <NUM>. Once the unitary core-shell mold <NUM> is formed at step <NUM>, the method <NUM> may include, as depicted at <NUM>, positioning at least one support member <NUM> within the reinforcement recess(es) <NUM> and in contact with the at least one location(s) <NUM>. Additionally, as depicted at <NUM>, the method <NUM> may include casting the cast component within the casting cavity <NUM>.

The unitary core-shell mold <NUM> may be constructed from a refractory material capable of maintaining structural integrity when exposed to molten metal alloys at high temperatures. For example, the unitary core-shell mold <NUM> may be formed from a solid ceramic material. Nonlimiting examples of ceramics include those based on silica, alumina, calcium, magnesium, zirconia, and other refractory oxides. Materials such as alumina- and zirconia-based ceramics are considered nonreactive with certain metal alloys.

It should be appreciated that the method <NUM> may facilitate the utilization of high temperature, engineered support mechanisms (e.g., the support member(s) <NUM> positioned within the reinforcement recess(es) <NUM>) during a pouring phase of a casting process wherein a molten metal may be poured into the unitary core-shell mold <NUM>. As such, the amount of additive material required to produce the unitary core-shell mold <NUM> may be reduced relative to a conventionally-produced casting core and/or shell mold. Additionally, the printing time required to produce the unitary core-shell mold <NUM> via additive manufacturing may be reduced.

By way of illustration, an embodiment of the method <NUM> is graphically depicted by <FIG> in sequence. <FIG> illustrates the receiving of data indicative of the location(s) <NUM> of the unitary core-shell mold <NUM> (depicted as a potential (e.g., a design) unitary core-shell mold <NUM>) that is susceptible to the stress concentration <NUM> (e.g., the projected stress concentration(s) <NUM> anticipated when the unitary core-shell mold <NUM> is employed to cast the component). <FIG> illustrates the unitary core-shell mold <NUM> formed via an additive manufacturing process. The unitary core-shell mold <NUM> may define the reinforcement recess(es) <NUM> adjacent to the location(s) <NUM>. <FIG> also illustrates that the support member(s) <NUM> is positioned within (e.g., inserted into) the reinforcement recess(es) <NUM> following the formation of the unitary core-shell mold <NUM>. <FIG> depicts the unitary core-shell mold <NUM> with the support member(s) <NUM> positioned within the reinforcement recess(es) <NUM> prior to and/or during the casting of the cast component.

As particularly depicted in <FIG> and <FIG>, in an embodiment, the unitary core-shell mold <NUM> may include a shell portion <NUM>. The shell portion <NUM> may include the shell wall <NUM>. The shell wall <NUM> may, in an embodiment, extend between a first mold end <NUM> and a second mold end <NUM> to define a mold length (ML). The shell wall <NUM> may have a wall thickness (T) defined by an inner wall face <NUM> and an outer wall face <NUM>. The inner wall face <NUM> of the shell wall <NUM> may, in an embodiment, define an outer component shape of the cast component.

In an embodiment, the shell wall <NUM> may be configured as an outermost wall of the unitary core-shell mold <NUM>. As such, the outer wall face <NUM> may be exposed when the unitary core-shell mold <NUM> is employed to cast the cast component and the unitary core-shell mold <NUM> may have an absence of an overshell. In other words, the shell wall <NUM> may have sufficient strength when formed in accordance with the method <NUM> to resist loads developed upon the introduction of the component material <NUM> without necessitating support from an overshell.

The shell wall <NUM> may, in an embodiment, have a wall thickness (T) of <NUM> to <NUM>. The wall thickness (T) may be developed via the addition of wall layers until a plurality of wall layers establish the desired thickness. However, in an additional embodiment, the shell wall <NUM> may include a single wall layer of the desired thickness. By way of further example, the wall thickness (T) may be <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>. It should be appreciated that, in at least one embodiment, the wall thickness (T) may be a removal facilitation feature. As such, the wall thickness (T) may be selected to ensure the shell wall <NUM> is of sufficient strength to resist at least one load developed by the introduction of the component material <NUM> into the casting cavity <NUM> as the cast component is cast, while maximizing the removability of the unitary core-shell mold <NUM>.

In an embodiment, the unitary core-shell mold <NUM> may include a core portion <NUM> that may be positioned inward of the shell wall <NUM> and be unitary therewith. For example, the core portion <NUM> may be circumscribed by the shell wall <NUM>. In an embodiment, the core portion <NUM> may be integrated with the shell portion <NUM> via a plurality of tie structures <NUM> (which may also be referred to as "filaments") extending between the core and shell portions <NUM>, <NUM>. It should be appreciated that the tie structures <NUM> may be oriented to coincide with at least one feature of the cast component, such as a cooling hole of a turbine blade. It should further be appreciated that as a unitary structure, the plurality of tie structures <NUM> may be formed contemporaneously with the core and shell portions <NUM>, <NUM> via the additive manufacturing process.

In an embodiment, the core portion <NUM> may include the core wall <NUM>. The core wall <NUM> may extend between a first core end <NUM> and a second core end <NUM>. The first core end <NUM> may, for example, be generally coplanar with the first mold end <NUM>, while the second core end <NUM> may be disposed completely within the casting cavity <NUM>. A core face <NUM> of the core wall <NUM> may, in an embodiment, define an inner component shape of the cast component. Accordingly, the wall thickness (T), in the context of the core wall <NUM>, may be defined between opposing core faces <NUM> of the core wall <NUM>, such as depicted in <FIG>. As further depicted in <FIG>, in an additional embodiment, the wall thickness (T) of the core wall <NUM> may be defined between a core face <NUM> and an opposing recess/cavity of the core wall <NUM>.

As particularly illustrated in <FIG>, <FIG>, <FIG>, and <FIG>, the shell wall <NUM> and/or the core wall <NUM> may be formed to define the reinforcement recess(es) <NUM> adjacent to the location(s) <NUM> that is susceptible to a stress concentration(s) <NUM>. The reinforcement recess(es) <NUM> may be configured to receive the support member(s) <NUM> thereby locating the support member(s) <NUM> in position to facilitate the resisting of the stress concentration developed by the component material <NUM> by the shell and/or core wall <NUM>, <NUM>.

In an embodiment, the reinforcement recess(es) <NUM> may be located entirely within the corresponding wall of the unitary core-shell mold <NUM>. In other words, the reinforcement recess(es) <NUM> may be positioned entirely within the wall thickness (T) of the shell and/or core wall <NUM>, <NUM>. For example, in an embodiment, the reinforcement recess(es) <NUM> may be positioned between the inner and outer wall faces <NUM>, <NUM> of the core wall <NUM> and may not breach either of the inner and outer wall faces <NUM>, <NUM>. As such, the reinforcement recess(es) <NUM> may have a recess thickness (RT) that is less than the wall thickness (T).

In an embodiment, the reinforcement recess(es) <NUM> may define a recess opening <NUM> in the shell wall <NUM> at the first mold end <NUM>. In an additional embodiment, the reinforcement recess(es) <NUM> may define a recess opening <NUM> in the core wall <NUM> at the first core end <NUM>. As such, the recess opening <NUM> may facilitate the positioning of the support member(s) <NUM> within the reinforcement recess(es) <NUM> following the formation of the unitary core-shell mold <NUM>. It should be appreciated that reinforcement recess(es) <NUM> may extend from the first ends <NUM>, <NUM> towards the corresponding second ends <NUM>, <NUM>.

As particularly depicted in <FIG> and <FIG>, in an embodiment, the unitary core-shell mold <NUM> may include a plurality of reinforcement recesses <NUM>. For example, in an embodiment, a first reinforcement recess <NUM> may be defined by the shell wall <NUM> while a second reinforcement recess <NUM> may be defined by the core wall <NUM>. It should be appreciated that in various embodiments, a plurality of reinforcement recesses <NUM> may be defined in the shell wall <NUM>, the core wall <NUM>, or both.

Referring now to <FIG>, <FIG>, <FIG>, and <FIG>, in an embodiment, the support member(s) <NUM> may be formed from a refractory material having a melting temperature that is higher than the melting temperature of the component material <NUM>. For example, the support member(s) <NUM> may be formed from alumina or a derivation thereof. Additionally, the support member(s) <NUM> may be formed to have a selective stiffness and/or thermal characteristic.

In an embodiment, the support member(s) <NUM> may have a length, extending generally between the first mold end <NUM> and the second mold end <NUM>, that is greater than a width. For example, the support member(s) <NUM> may be configured as a sheet, panel, rod, ribbon, flat stock, or similar structure having the degree of stiffness and/or thermal characteristic required to support the shell and/or core wall <NUM>, <NUM>. In an exemplary embodiment, the support member(s) <NUM> may be formed as a metal sheet having a high melting temperature such that the melting temperature is higher than the component material <NUM>. It should be appreciated that inserting the metal sheet (or similar structure) into the reinforcement recess(es) <NUM> within the defining shell and/or core wall <NUM>, <NUM> may increase a load limit of the location(s) <NUM>. Further, the utilization of the support member(s) <NUM>, in the form of a metal sheet, may facilitate the formation of the location(s) <NUM> with a reduced thickness relative to other portions <NUM> of the unitary core-shell mold <NUM>.

As depicted in <FIG>, the support member(s) <NUM> may, in an embodiment, be configured as a plurality of spheres. In such an embodiment, the plurality of spheres may be inserted into the reinforcement recess(es) <NUM> following the formation of the unitary core-shell mold <NUM>. It should be appreciated that inserting the spheres in the reinforcement recess(es) <NUM> may facilitate the formation of certain portions <NUM> (e.g., the location(s) <NUM>) of the unitary core-shell mold <NUM> with a reduced thickness relative to other portions <NUM> of the unitary core-shell mold <NUM>. The reduced thickness may improve the thermal characteristics of the unitary core-shell mold <NUM>. For example, the utilization of the support member(s) <NUM> (e.g., as a plurality of spheres) may facilitate an improved cooling rate during the casting process and/or an increased thermal capacity of a portion <NUM> of the unitary core-shell mold <NUM>. As such, the amount of additive material and print time required to form the unitary core-shell mold <NUM> may be minimized. It should further be appreciated that non-spherical, and/or irregular shaped support members may also be used in conjunction with, or in place of, the spheres.

As depicted at <NUM>, in an embodiment, positioning the support member(s) <NUM> (as illustrated in <FIG>) within the reinforcement recess(es) <NUM> may also include securing the support member(s) <NUM> within the reinforcement recess(es) <NUM>. Accordingly, in an embodiment, the reinforcement recess(es) <NUM> may include a first retention feature <NUM>.

In an embodiment, the first retention feature <NUM> may include a shape of the reinforcement recess(es) <NUM>. For example, as depicted in <FIG> and <FIG>, the reinforcement recess(es) <NUM> may be formed with a curve that facilitates the retention of the support member(s) <NUM>. In a further example wherein the first retention feature <NUM> corresponds to the shape of the reinforcement recess(es) <NUM>, a dimension of the reinforcement recess(es) <NUM> may narrow in order to establish a friction fit with the support member(s) <NUM>. In an embodiment, and with reference to <FIG>, the first retention feature <NUM> may include at least one protrusion <NUM> positioned within the reinforcement recess(es) <NUM>. In a further embodiment, the first retention feature <NUM> may include at least one recess <NUM>.

In order to secure the support member(s) <NUM> within the reinforcement recess(es) <NUM>, the support member(s) <NUM> may be formed with a second retention feature <NUM> configured to engage the first retention feature <NUM>. In an embodiment, the second retention feature <NUM> may include a shape of the support member(s) <NUM>. For example, as depicted in <FIG> and <FIG>, the support member(s) <NUM> may be formed with a curve that corresponds to a curve of the reinforcement recess(es) <NUM>. In a further example, a dimension of the support member(s) <NUM> may broaden in order to establish a friction fit with the reinforcement recess(es) <NUM>. In an additional embodiment, as depicted in <FIG>, the second retention feature <NUM> may include at least one protrusion configured to engage the corresponding protrusion(s) <NUM> and/or recess(es) <NUM> of the reinforcement recess(es) <NUM>.

In a further embodiment, securing the support member(s) <NUM> within the reinforcement recess(es) <NUM> may be accomplished via chemical means. Accordingly, as depicted in <FIG>, an adhering agent <NUM> may be introduced into the reinforcement recess(es) <NUM> following insertion of the support member(s) <NUM>. For example, following the positioning of the support member(s) <NUM> within the reinforcement recess(es) <NUM>, an adhesive, epoxy, concrete and/or other liquid may be permitted to cure within the reinforcement recess(es) <NUM> and secure the support member(s) <NUM> therein.

As depicted at <NUM>, the method <NUM> may include firing the unitary core-shell mold <NUM> prior to the positioning of the support member(s) <NUM> within the reinforcement recess(es) <NUM> at step <NUM>. It should be appreciated that firing the unitary core-shell mold <NUM> prior to the insertion of the support member(s) <NUM> may permit the forming of the support member(s) <NUM> from a material having a lower melting point than the firing temperature.

As depicted at <NUM>, the method <NUM> may include firing the unitary core-shell mold <NUM> following the positioning of the support member(s) <NUM> within the reinforcement recess(es) <NUM> at step <NUM>. It should be appreciated that firing the unitary core-shell mold <NUM> following the insertion of the support member(s) <NUM> may facilitate the securing of the support member(s) <NUM> within the reinforcement recess(es) <NUM>.

In an embodiment, such as depicted in <FIG>, the stress concentration(s) <NUM> may be a projected stress concentration(s) <NUM> resulting from the anticipated introduction of the component material <NUM> into the casting cavity <NUM>. The stress concentration(s) <NUM> may be a point concentration and/or an area concentration, such as depicted in <FIG>.

In an embodiment, the stress concentration(s) <NUM> may correspond to a potential mechanical stress concentration. Accordingly, the stress concentration(s) <NUM> may correspond to a projected creep of the location(s) <NUM>. For example, at a given wall thickness (T) the shell and/or core wall <NUM>, <NUM> may be projected to deform in response to load generated by the introduction of the component material <NUM>. As such, the employment of the support member(s) <NUM> in accordance with the method <NUM> may preclude a necessity to increase the wall thickness (T) in order to resist creep (e.g., deformation).

In an additional embodiment, the stress concentration(s) <NUM> may correspond to a projected head pressure approaching a load limit <NUM> of the location(s) <NUM>. In other words, it may be projected that the load exerted on the shell and/or core wall <NUM>, <NUM> by the introduction of the component material <NUM> may exceed the load limit <NUM> of the location(s) <NUM>. In such an embodiment, without reinforcement, or other support, the location(s) <NUM> may be breached resulting in a failure of the casting of the cast component. Therefore, the employment of the support member(s) <NUM> in accordance with the method <NUM> may preclude a necessity to increase the wall thickness (T) in order to increase the load limit <NUM> to a level capable of withstanding the projected head pressure.

In an embodiment the stress concentration(s) <NUM> may correspond to a potential thermal stress. For example, the stress concentration(s) <NUM> may be anticipated when the projected temperature of the component material <NUM> exceeds the thermal load limit of the location(s) <NUM>. As a further example, the stress concentration(s) <NUM> may correspond to a coefficient of thermal expansion mismatch at the location(s) <NUM>. Accordingly, it may be desirable to alter the thermal characteristics of the location(s) <NUM>, and thus the shell and/or core wall <NUM>, <NUM>, via the positioning of the support member <NUM> adjacent to the location(s) <NUM>.

As depicted at <NUM>, the method <NUM> may include forecasting a stress magnitude (e.g., the magnitude of the stress concentration(s) <NUM>) approaching the load limit <NUM> of the shell and/or core wall <NUM>, <NUM> during a projected casting of the cast component. Based on the forecast stress magnitude approaching the load limit <NUM>, the location(s) <NUM> susceptible to the stress concentration(s) <NUM> may be identified. It should be appreciated that the load limit <NUM> may be a mechanical load limit and/or a thermal load limit.

In an embodiment, identifying the location(s) <NUM> may be accomplished via computer modeling. For example, as depicted in <FIG>, a controller <NUM> may be employed to model the casting process at <NUM>. Modeling the casting process at <NUM> may include modeling, via the controller <NUM>, the introduction of the component material <NUM>, in liquid form, into the casting cavity <NUM> during the casting of the cast component. Based on the modeled introduction of the component material <NUM>, a predicted plurality of stresses <NUM> may be determined. The predicted plurality of stresses <NUM> may be such stresses as may be exerted by the component material <NUM> onto a corresponding plurality of portions <NUM> of the unitary core-shell mold <NUM>.

In an embodiment, the plurality of stresses <NUM> may be utilized to determine a minimal wall thickness <NUM> for the unitary core-shell mold <NUM> (e.g., a minimal shell-wall thickness and a minimal core-wall thickness). The minimal wall thickness <NUM> may have a load limit <NUM> that is greater than at least one stress of the plurality of stresses <NUM> exerted by the component material <NUM>. In an embodiment, the minimal wall thickness <NUM> for the shell and/or core wall <NUM>, <NUM> may be determined as a percentage of a maximal projected stress. For example, the minimal wall thickness <NUM> may be established at a thickness wherein the resulting load limit <NUM> is sufficient to withstand <NUM>% of the maximal projected stress of the plurality of stresses <NUM>. In an alternative example, the minimal wall thickness <NUM> may be established at a thickness wherein the resulting load limit <NUM> is sufficient to withstand <NUM>% of the maximal projected stress of the plurality of stresses <NUM>. In yet a further example, the minimal wall thickness <NUM> may be determined based on the average projected stress of the plurality of stresses <NUM>.

It should be appreciated that increasing the minimal wall thickness <NUM> may reduce the number of support members <NUM> that may be required but may increase the amount of added material and/or printing time required to produce the unitary core-shell mold <NUM>. Similarly, it should be appreciated that reducing the minimal wall thickness <NUM> may result in material and/or production time savings, but may increase the number of support members <NUM> required to preclude failure of the unitary core-shell mold <NUM> during the casting process.

In an embodiment, the minimal wall thickness <NUM> determined via the modeling may determine the load limit <NUM> for the plurality of portions <NUM> of the unitary core-shell mold <NUM>. As depicted at <NUM>, the controller <NUM> may determine the stress concentration(s) <NUM> at which one of the plurality of stresses <NUM> approaches the load limit <NUM>. Therefore, the location(s) <NUM> corresponding to the stress concentration(s) <NUM> may be a location(s) <NUM> susceptible to the stress concentration(s) <NUM>.

In an embodiment, identifying the location(s) <NUM> susceptible to a stress concentration(s) <NUM> may be accomplished via an engineering diagnostic expert system <NUM>. The engineering diagnostic expert system <NUM> may include manifestations of engineering domain knowledge, such as troubleshooting guides, anomaly validation reports, after-action reports, design specifications, testing reports, and/or other captures of the experience and decision-making knowledge of a human expert. For example, the engineering diagnostic expert system <NUM> may indicate that certain portions <NUM> of the unitary core-shell mold <NUM> may be more susceptible to creep than other portions <NUM>. This indication may be based on previous experience with other, similar, casting processes.

In an embodiment, identifying the location(s) <NUM> may be accomplished via iterative testing. Accordingly, the method <NUM> may include iteratively testing a plurality of unitary core-shell mold prototypes <NUM> via a plurality of test castings. During the iterative testing cycle, the wall thickness (T) of the shell wall <NUM> and/or the core wall <NUM> may be reduced with each iterative test. By iteratively reducing the wall thickness (T), the iterative test cycle may identify the location(s) <NUM> of the unitary core-shell mold <NUM> that is susceptible to the stress concentration(s) <NUM> at a given wall thickness (T). For example, failure points of the unitary core-shell mold <NUM> may be noted during each iteration of the testing cycle. These locations <NUM> may be supported in a subsequent test iteration via the method <NUM> disclosed herein. This process may be repeated until a desirable balance between material and production time costs and the number of support members <NUM> is achieved.

As used herein, the terms "additively manufactured" or "additive manufacturing techniques or processes" refer generally to manufacturing processes wherein successive layers of material(s) are provided on each other to "build-up," layer-by-layer, a three-dimensional component (eg. The successive layers generally fuse together to form a monolithic component that may have a variety of unitary sub-components. Although additive manufacturing technology is described herein for the fabrication of complex objects by building objects point-by-point, layer-by-layer, typically in a vertical direction, other methods of fabrication are possible and within the scope of the present subject matter. For example, although the discussion herein refers to the addition of material to form successive layers, one skilled in the art will appreciate that the methods and structures disclosed herein may be practiced with any additive manufacturing technique or manufacturing technology. For example, embodiments of the present disclosure may use layer-additive processes, layer-subtractive processes, or hybrid processes.

Suitable additive manufacturing techniques in accordance with the present disclosure include, for example, Fused Deposition Modeling (FDM), Selective Laser Sintering (SLS), 3D printing such as by inkjets, laser jets, and binder jets, Sterolithography (SLA), Direct Selective Laser Sintering (DSLS), Electron Beam Sintering (EBS), Electron Beam Melting (EBM), Laser Engineered Net Shaping (LENS), Laser Net Shape Manufacturing (LNSM), Direct Metal Deposition (DMD), Digital Light Processing (DLP), Direct Selective Laser Melting (DSLM), Selective Laser Melting (SLM), Direct Metal Laser Melting (DMLM), and other known processes.

The additive manufacturing processes described herein may be used for forming unitary core-shell mold <NUM> using any suitable material. For example, the material may be plastic, metal, concrete, ceramic, polymer, epoxy, photopolymer resin, wax, or any other suitable material. These materials are examples of materials suitable for use in the additive manufacturing processes described herein and may be generally referred to as "additive materials.

In addition, one skilled in the art will appreciate that a variety of materials and methods for bonding those materials may be used and are contemplated as within the scope of the present disclosure. As used herein, references to "fusing" may refer to any suitable process for creating a bonded layer of any of the above materials. For example, if an object is made from polymer, fusing may refer to creating a thermoset bond between polymer materials. If the object is epoxy, the bond may be formed by a crosslinking process. If the material is ceramic, the bond may be formed by a sintering process. If the material is powdered metal, the bond may be formed by a melting or sintering process. One skilled in the art will appreciate that other methods of fusing materials to make a component by additive manufacturing are possible, and the presently disclosed subject matter may be practiced with those methods.

In addition, the additive manufacturing process disclosed herein allows unitary core-shell mold <NUM> to be formed from multiple materials. Thus, the unitary core-shell mold <NUM> described herein may be formed from any suitable mixtures of the above materials. For example, the unitary core-shell mold <NUM> may include multiple layers, segments, or parts that are formed using different materials, processes, and/or on different additive manufacturing machines.

An exemplary additive manufacturing process will now be described. Additive manufacturing processes fabricate components using three-dimensional (3D) information, for example a three-dimensional computer model, of the unitary core-shell mold <NUM>. Accordingly, a three-dimensional design model of the unitary core-shell mold <NUM> and/or the cast component may be defined prior to manufacturing. In this regard, a model or prototype of the unitary core-shell mold <NUM> and/or component may be scanned to determine the corresponding three-dimensional information. As another example, a model of the unitary core-shell mold <NUM> and/or the cast component may be constructed using a suitable computer aided design (CAD) program to define the three-dimensional design model of the unitary core-shell mold <NUM> and/or the cast component as described herein.

The design model may include 3D numeric coordinates of the entire configuration of the unitary core-shell mold <NUM> and/or the cast component including both external and internal surfaces of the component. For example, the design model may define the body, the surface, and/or internal passageways such as openings, support structures, etc. In one exemplary embodiment, the three-dimensional design model is converted into a plurality of slices or segments, e.g., along a central (e.g., vertical) axis of the component or any other suitable axis. Each slice may define a thin cross section of the unitary core-shell mold <NUM> and/or the cast component for a predetermined height of the slice. The plurality of successive cross-sectional slices together form the unitary core-shell mold <NUM>. The unitary core-shell mold <NUM> is then "built-up" slice-by-slice, or layer-by-layer, until finished.

In this manner, the unitary core-shell mold <NUM> may be fabricated using the additive process, or more specifically each layer is successively formed, e.g., by fusing or polymerizing a plastic using laser energy or heat or by sintering or melting metal powder. For example, a particular type of additive manufacturing process may use an energy beam, for example, an electron beam or electromagnetic radiation such as a laser beam, to sinter or melt a powder material or polymerize a liquid. Any suitable laser and laser parameters may be used, including considerations with respect to power, laser beam spot size, and scanning velocity. The build material may be formed by any suitable powder or material selected for enhanced strength, durability, and useful life, particularly at high temperatures.

Each successive layer may be, for example, between about <NUM> and <NUM>, although the thickness may be selected based on any number of parameters and may be any suitable size according to alternative embodiments. Therefore, utilizing the additive formation methods described above, the unitary core-shell mold <NUM> described herein may have cross sections as thin as one thickness of an associated powder layer, e.g., <NUM>, utilized during the additive formation process.

In an embodiment, the additive manufacturing process employed to form the unitary core-shell mold <NUM> may, as depicted at <NUM>, include contacting a pure portion of the unitary core-shell mold <NUM> with a liquid ceramic photopolymer. As shown at <NUM>, the process may include irradiating a portion of the liquid ceramic photopolymer adjacent to the cured portion through a window contacting the liquid ceramic photopolymer. Additionally, as shown at <NUM>, the unitary core-shell mold <NUM> may be removed from the uncured liquid ceramic photopolymer.

In addition, utilizing an additive process, the surface finish and features of the unitary core-shell mold <NUM> may vary as needed depending on the cast component. For example, the surface finish may be adjusted (e.g., made smoother or rougher) by selecting appropriate laser scan parameters (e.g., laser power, scan speed, laser focal spot size, etc.) during the additive process, especially in the periphery of a cross-sectional layer that corresponds to the part surface. For example, a rougher finish may be achieved by increasing laser scan speed or decreasing the size of the melt pool formed, and a smoother finish may be achieved by decreasing laser scan speed or increasing the size of the melt pool formed. The scanning pattern and/or laser power can also be changed to change the surface finish in a selected area.

Notably, in exemplary embodiments, several features of the unitary core-shell mold <NUM> described herein were previously not possible due to manufacturing restraints. However, the present inventors have advantageously utilized current advances in, and limitations of, additive manufacturing techniques to develop exemplary embodiments of the unitary core-shell mold <NUM> in accordance with the present disclosure.

It should be appreciated that utilizing additive manufacturing methods, even multi-part components , such as a shell mold, a core, and/or a core mold may be formed as a single piece of additive ceramic or additive plastic, and may, thus, include fewer sub-components and/or joints compared to prior designs. The unitary formation of these multi-part components through additive manufacturing may advantageously improve the overall assembly process. For example, the unitary formation reduces the number of separate parts that must be assembled, thus reducing associated time and overall assembly costs. Additionally, existing issues with, for example, leakage, joint quality between separate parts, and overall performance may advantageously be reduced.

Also, the additive manufacturing methods described above enable much more complex and intricate shapes and contours of the cast component described herein. In addition, the additive manufacturing process enables the manufacture of a single component having different materials such that different portions of the component may exhibit different performance characteristics. The successive, additive nature of the manufacturing process enables the construction of these novel features. As a result, the components described herein may enable more intricate internal cast component shapes.

It should, however, be appreciated that employing additive manufacturing processes to manufacture a casting core and/or shell mold may result in difficulties associated with integrating the core/shell into an efficient manufacturing process. For example, the time required to form a casting core and/or a shell mold having sufficient dimensional stability (e.g., wall thickness) using an additive manufacturing process, such as a DLP process, may delay the manufacturing process and may require the use of excess material. Further, in the molding process, it may be desirable to efficiently produce portions of a core/mold that do not require the same dimensional accuracy as may be required other portions. For example, it may be desirable to produce passages for directing the flow of component material <NUM> into a single or plurality of molds. Further, when forming a core/mold via a DLP process, it may be desirable to improve the ease of removing the cast component from the mold once the casting is completed. For example, the knockout process may be improved by producing a thinner unitary core-shell mold <NUM> to reduce the likelihood that the cast product may be damaged upon removal of the unitary core-shell mold <NUM>. It may also be desirable to control the thermal conductivity of the unitary core-shell mold <NUM> to control crystal growth and/or tailor the material properties of the cast component and/or manage thermal strains in the unitary core-shell mold <NUM>. Accordingly, forming the unitary core-shell mold <NUM> via the methods disclosed herein may be particularly beneficial.

Referring again to <FIG>, in general, the engine <NUM> may include a core gas turbine engine (indicated generally by reference character <NUM>) and a fan section <NUM> positioned upstream thereof. The core engine <NUM> may generally include a substantially tubular outer casing <NUM> that defines an annular inlet <NUM>. In addition, the outer casing <NUM> may further enclose and support a booster compressor <NUM> for increasing the pressure of the air that enters the core engine <NUM> to a first pressure level. A high pressure, multi-stage, axial-flow compressor <NUM> may then receive the pressurized air from the booster compressor <NUM> and further increase the pressure of such air. The pressurized air exiting the high-pressure compressor <NUM> may then flow to a combustor <NUM> within which fuel is injected by a fuel system <NUM> into the flow of pressurized air, with the resulting mixture being combusted within the combustor <NUM>. The high energy combustion products are directed from the combustor <NUM> along the hot gas path of the engine <NUM> to a first (high pressure, HP) turbine <NUM> for driving the high pressure compressor <NUM> via a first (high pressure, HP) drive shaft <NUM>, and then to a second (low pressure, LP) turbine <NUM> for driving the booster compressor <NUM> and fan section <NUM> via a second (low pressure, LP) drive shaft <NUM> that is generally coaxial with first drive shaft <NUM>. After driving each of turbines <NUM> and <NUM>, the combustion products may be expelled from the core engine <NUM> via an exhaust nozzle <NUM> to provide propulsive jet thrust.

It should be appreciated that each turbine <NUM>, <NUM> may generally include one or more turbine stages, with each stage including a turbine nozzle and a downstream turbine rotor. As will be described below, the turbine nozzle may include a plurality of vanes disposed in an annular array about the centerline axis <NUM> of the engine <NUM> for turning or otherwise directing the flow of combustion products through the turbine stage towards a corresponding annular array of rotor blades forming part of the turbine rotor. As is generally understood, the rotor blades may be coupled to a rotor disk of the turbine rotor, which is, in turn, rotationally coupled to the turbine's drive shaft (e.g., drive shaft <NUM> or <NUM>).

Additionally, as shown in <FIG>, the fan section <NUM> of the engine <NUM> may generally include a rotatable, axial-flow fan rotor <NUM> surrounded by an annular fan casing <NUM>. In particular embodiments, the (LP) drive shaft <NUM> may be connected directly to the fan rotor <NUM> such as in a direct-drive configuration. In alternative configurations, the (LP) drive shaft <NUM> may be connected to the fan rotor <NUM> via a speed reduction device <NUM> such as a reduction gear gearbox in an indirect-drive or geared-drive configuration. Such speed reduction devices may be included between any suitable shafts/spools within engine <NUM> as desired or required.

It should be appreciated by those of ordinary skill in the art that the fan casing <NUM> may be supported relative to the core engine <NUM> by a plurality of substantially radially-extending, circumferentially-spaced outlet guide vanes <NUM>. As such, the fan casing <NUM> may enclose the fan rotor <NUM> and its corresponding fan rotor blades <NUM>. Moreover, a downstream section <NUM> of the fan casing <NUM> may extend over an outer portion of the core engine <NUM> to define a secondary, or by-pass, airflow conduit <NUM> that provides additional propulsive jet thrust.

During operation of the engine <NUM>, it should be appreciated that an initial air flow <NUM> (indicated by arrow) may enter the engine <NUM> through an associated inlet <NUM> of the fan casing <NUM>. The initial air flow <NUM> then passes through the fan blades <NUM> and splits into a first compressed air flow <NUM> (indicated by arrow) that moves through conduit <NUM> and a second compressed air flow <NUM> (indicated by arrow) that enters the booster compressor <NUM>. The pressure of the second compressed air flow <NUM> is then increased and enters the high-pressure compressor <NUM> (as indicated by arrow <NUM>). After mixing with fuel and being combusted within the combustor <NUM>, the combustion products <NUM> exit the combustor <NUM> and flow through the first turbine <NUM>. Thereafter, the combustion products <NUM> flow through the second turbine <NUM> and exit the exhaust nozzle <NUM> to provide thrust for the engine <NUM>.

Referring now to <FIG>, wherein a block diagram of one embodiment of a controller <NUM> for use in accordance with the present disclosure is illustrated. As shown, the controller <NUM> may include one or more processor(s) <NUM> and associated memory device(s) <NUM> configured to perform a variety of computer-implemented functions (e.g., performing the methods, steps, calculations and the like and storing relevant data as disclosed herein). Additionally, the controller <NUM>, may also include a communications module <NUM> to facilitate communications between the controller <NUM>, and the various systems and/or operators. Further, the controller <NUM> may include a modeling module <NUM> configured to model a casting process utilizing the unitary core-shell mold <NUM> as described herein.

As used herein, the term "processor" refers not only to integrated circuits referred to in the art as being included in a computer, but also refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits. Additionally, the memory device(s) <NUM> may generally comprise memory element(s) including, but not limited to, computer readable medium (e.g., random access memory (RAM)), computer readable non-volatile medium (e.g., a flash memory), a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disc (DVD) and/or other suitable memory elements. Such memory device(s) <NUM> may generally be configured to store suitable computer-readable instructions that, when implemented by the processor(s) <NUM>, configure the controller <NUM> to perform various functions.

Claim 1:
A method for casting a component (<NUM>), the method comprising:
identifying a location of the unitary core-shell mold (<NUM>) that is susceptible to a stress concentration by forecasting a stress magnitude approaching a load limit of a shell wall (<NUM>) or a core wall (<NUM>) during casting;
receiving data indicative of the location of the unitary core-shell mold (<NUM>) that is susceptible to the stress concentration when the unitary core-shell mold (<NUM>) is employed to cast the component (<NUM>);
forming, via an additive manufacturing process, the unitary core-shell mold (<NUM>) defining a casting cavity (<NUM>), the unitary core-shell mold (<NUM>) comprising the shell wall (<NUM>) defining an outer component (<NUM>) shape and the core wall (<NUM>) positioned inward of the shell wall (<NUM>) and defining an inner component shape, wherein the shell wall (<NUM>) or the core wall (<NUM>) defines a reinforcement recess (<NUM>) adjacent to the location that is susceptible to the stress concentration;
following the forming of the unitary core-shell mold (<NUM>), positioning a support member (<NUM>) within the reinforcement recess (<NUM>) and adjacent with the location, wherein positioning the support member (<NUM>) within the reinforcement recess (<NUM>) further comprises securing the support member (<NUM>) within the reinforcement recess (<NUM>), wherein securing the support member (<NUM>) within the reinforcement recess (<NUM>) further comprises:
engaging a first retention feature (<NUM>) in the reinforcement recess (<NUM>) with a second retention feature (<NUM>) in the support member (<NUM>), wherein the first retention feature (<NUM>) includes a shape of the reinforcement recess (<NUM>), wherein the reinforcement recess (<NUM>) is formed with a curve that facilitates the retention of the support member (<NUM>) and wherein the second retention feature (<NUM>) includes a shape of the support member (<NUM>), wherein the support member (<NUM>) is formed with a curve that corresponds to the curve of the reinforcement recess (<NUM>); and
casting the component (<NUM>) within the casting cavity (<NUM>).