Patent Description:
The pace of change and improvement in the realms of power generation, aviation, and other fields has accompanied extensive research for manufacturing components used in these fields. Conventional manufacture of metallic components generally includes milling or cutting away regions from a slab of metal before treating and modifying the cut metal to yield a part, which may have been simulated using computer models and computer aided design. Manufactured components which may be formed from metal include airfoil components for installation in a turbomachine such as an aircraft engine or power generation system, as well as mechanical components for other manufacturing, transportation, and structural systems.

The development of additive manufacturing, also known in the art as "3D printing," can reduce manufacturing costs by allowing such components to be formed more quickly, with unit-to-unit variations as appropriate. Among other advantages, additive manufacture can directly apply computer-generated models to a manufacturing process while relying on less expensive equipment and/or raw materials.

Some additive manufacturing allows a component to be formed from a reserve of fine metal powder positioned on a build plate, which is processed by an electron beam or laser (using fusing heat treatments such as sintering or melting) to form a component or sub-component. Additive manufacturing equipment can also form components by using three-dimensional models generated with software included within and/or external to the manufacturing equipment. Some devices fabricated via additive manufacture can be formed initially as several distinct components at respective processing stages before being assembled in a subsequent process.

Additive manufacturing opens opportunities for repair of existing components and/or creation of hybrid components where an additive component (or structure) is built on one or more surfaces of a pre-existing component without requiring separate attachment. For example, cast components may be used as a base component and additive features may be built on a cast and prepared build surface of the base component positioned in an additive manufacturing tool or modality.

<CIT> describes additive manufacturing of 3D components. It discloses a method of forming structure on a component including: providing a component having a first surface; adhering powder to the first surface; and directing a beam from a directed energy source to fuse the powder in a pattern corresponding to a layer of the structure.

According to the present invention there is provided a rotor blade, according to claim <NUM>, comprising: a root connector configured to engage a turbine shaft of a turbomachine; an airfoil extending from the root connector, the airfoil including an airfoil body, the airfoil body comprising a pre-existing portion and a component build surface, the airfoil body defining at least one air channel enclosed within the airfoil body and extending to the component build surface; and an additive portion from the component build surface of the airfoil body, the additive portion including an additive structure further defining the at least one air channel extending from the component build surface to an external surface of the additive portion, the airfoil including a pressure side wall and a suction side wall that define an outer surface and an outboard tip, the airfoil body terminating in the component build surface prior to the outboard tip and the additive portion including the outboard tip; wherein the additive portion further includes at least one internal air chamber having a lateral cross-section greater than a largest width of the at least one air channel and a total component density of the additive structure is less than a total component density of the airfoil body.

The illustrative aspects of the present disclosure are arranged to solve the problems herein described and/or other problems not discussed.

These and other features of this disclosure will be more readily understood from the following detailed description of the various aspects of the disclosure taken in conjunction with the accompanying drawings that depict various examples and embodiments of the disclosure, in which:.

In the following description, reference is made to the accompanying drawings that form a part thereof, and in which is shown by way of illustration specific exemplary embodiments and examples in which the present teachings may be practiced. These embodiments and examples are described in sufficient detail to enable those skilled in the art to practice the present teachings and it is to be understood that other embodiments and examples may be used and that changes may be made without departing from the scope of the present teachings. The following description is, therefore, merely illustrative.

Where an element or layer is referred to as being "on," "engaged to," "disengaged from," "connected to" or "coupled to" another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly engaged to," "directly connected to" or "directly coupled to" another element or layer, there may be no intervening elements or layers present.

Referring to <FIG>, an example system <NUM> for additive manufacturing of a hybrid component <NUM>, such as a rotor blade, including a pre-existing component <NUM> and an additive component <NUM>, is depicted. Pre-existing component <NUM> and additive component <NUM> may have one or more internal features, such as air channels, that may be aligned during additive manufacture to extend the internal features from pre-existing component <NUM> into additive component <NUM>. Component <NUM> may form part of, or may be adaptable to form part of, a larger component and/or machine, such as a power generation assembly. It will be understood, however, that component <NUM> may have applications other than those described by example herein. Component <NUM> may have a build direction <NUM> coincident with the Z axis describing the direction in which materials are added to form the desired structure. In additive manufacture, a "build direction" of one or more components may be defined by a fabricator before raw materials are processed from raw materials into a desired structure. A build direction for a given component and/or sub-component therefore defines the order in which structural features are formed over time as raw materials (e.g., metallic powders) are fused (sintered or melted) to form a structure. Such materials can include, e.g., one or more pure metals and/or alloys including without limitation: Copper (Cu), Chromium (Cr), Titanium (Ti), Nickel (Ni), aluminum (Al), etc. In an example embodiment, the build direction <NUM> of component <NUM> can be oriented along one axis, and perpendicular to the plane of X and Y axis, and generally can be defined to assist in describing the three dimensional structure of the component, as well as the way in which it is formed. Component <NUM> may include one or more additive supports <NUM> manufactured with component <NUM> to be removed prior to use, assembly, or further manufacturing of component <NUM>.

Component <NUM> may by created by additively manufacturing additive component <NUM> on a component build surface <NUM> of pre-existing component <NUM>. For example, pre-existing component <NUM> may be positioned in and through build plate <NUM>. Build plate <NUM> may have a plate build surface <NUM> and a build portion <NUM> may protrude from plate build surface <NUM> into build chamber <NUM> to expose one or more build surfaces, such as component build surface <NUM>. In some embodiments and examples, pre-existing component <NUM> may have a component body <NUM> of sufficient size to extend through build plate <NUM>. For example, component body <NUM> may extend through and away from build plate <NUM> in a direction opposite build direction <NUM>. In some embodiments and examples, pre-existing component <NUM> may benefit from additional positioning support in addition to build plate <NUM>. For example, component body <NUM> may be engaged and be supported by a support plate <NUM>. Support plate <NUM> and build plate <NUM> may be maintained with a fixed distance between them to assist in maintaining the position of component <NUM> during additive manufacturing processes. In some embodiments and examples, support plate <NUM> and build plate <NUM> are mounted to a common positioning elevator <NUM> for moving component <NUM> in a working direction <NUM> opposite build direction <NUM>. For example, support plate <NUM> and build plate <NUM> may incorporate mounting features for removably engaging positioning elevator <NUM>. Mounting features may include rails and complementary slots, tongue and groove, flanges, support members, and other mating features, with or
without removable fasteners for attaching each of support plate <NUM> and build plate <NUM> to positioning elevator <NUM>. Support plate <NUM> may include a base receptacle <NUM>, such as a custom recess for receiving a distal portion of component body <NUM>, with or without mechanical fasteners for securing component body <NUM> in base receptacle <NUM>. In some embodiments and examples, a base clamp is incorporated into base receptacle <NUM>. In some embodiments and examples, build plate <NUM> may include a removable fixture <NUM> for positioning and securing pre-existing component <NUM> in build plate <NUM>. Removable fixture <NUM> may include a fixture body inserted into complementary fixture mounting opening in build plate <NUM>. Pre-existing component <NUM> may be inserted through a component mounting opening in removable fixture <NUM>.

Additive component <NUM> may be built from successive layers of powdered materials that are fused to one another and the preceding fused layers of additive component <NUM>. The initial layer of additive component <NUM> may be built on component build surface <NUM>, plate build surface <NUM>, or a combination thereof. Additive component <NUM> may initially exist solely as a 3D model or other computer-based instructions for building additive component <NUM> and stored in a computing system <NUM>. These instructions may be provided to additive manufacturing system <NUM> including a laser positioning system <NUM>, laser <NUM>, and build stage <NUM>. Build stage <NUM> may include powder delivery system <NUM> and build positioning system <NUM>. In some embodiments and examples, laser positioning system <NUM>, powder delivery system <NUM>, and build positioning system <NUM> may be controlled by computing system <NUM>. Successive layers of unfused powdered materials may be positioned by powder delivery system <NUM> and laser positioning system <NUM> may control laser <NUM> to selectively and controllably fuse the powdered material at desired positions, leaving the remaining powdered material in that layer unfused. In some embodiments and examples, laser positioning system <NUM> may move laser <NUM> in a generally X-Y coordinate system and control the timing and duration of laser <NUM> for selectively sintering powdered materials corresponding to that slice of the desired component shape, as well as any necessary supports, such as additive supports <NUM>. Build stage <NUM> may include a powder bed <NUM> with a top surface of powdered materials that provide the working layer for laser <NUM>. In some embodiments and examples, build stage <NUM> may include a powder hopper <NUM> for holding powdered materials prior to positioning or distribution across powder bed <NUM> and distributor <NUM> for positioning the powdered materials in an even layer in powder bed <NUM>. In the example shown, powder hopper <NUM> may be a powder well with a delivery piston <NUM> for pushing a desired volume of powdered materials into powder bed <NUM> for building each layer of additive component <NUM>. Distributor <NUM> may be a mechanical distributor, such as a roller, rake, brush, or sweep arm, that drags and levels powdered materials from powder hopper <NUM> across powder bed <NUM>. In embodiments and examples with a fixed powder bed, build positioning system <NUM> may include a recessed build chamber <NUM> with a moving build plate <NUM> that retracts from powder bed <NUM> as successive layers are added to component <NUM>. Build plate <NUM> may be supported by positioning elevator <NUM> and move in a working direction <NUM> that is opposite build direction <NUM>. Build plate <NUM> may provide a plate build surface <NUM> that supports a portion of additive component <NUM>, where at least a portion of the first layer of additive component <NUM> or additive supports <NUM> may be fused in contact with plate build surface <NUM> and any portion of additive component <NUM> in contact with build plate <NUM> may be removed from build surface <NUM> when the build is complete. Build chamber <NUM> thereby gets deeper to accommodate the completed portion of component <NUM> as the build progresses. Build chamber <NUM> may be defined as the space between sidewalls <NUM>, <NUM> from powder bed <NUM> to the maximum depth of build plate <NUM> in its deepest working position. Build chamber <NUM> may include additional sidewalls perpendicular to sidewalls <NUM>, <NUM> and laterally enclosing build chamber <NUM>. System <NUM> is described herein with regard to direct metal laser melting (DMLM) in a powder bed additive manufacturing system modality. It is understood that the general teachings of the disclosure are equally applicable to other modalities of additive manufacturing now existing or developed in the future.

In some embodiments and examples, computing system <NUM> may provide a plurality of programmatic controls and user interface for operating and coordinating laser positioning system <NUM>, powder delivery system <NUM>, and build positioning system <NUM> before, during, and after the build process for additive component <NUM>. In some embodiments and examples, computing system <NUM> is a general purpose computing devices, such as a personal computer, work station, mobile device, or an embedded system in an industrial control system (using general purpose computing components and operating systems). In some embodiments and examples, computing system <NUM> may be a specialized data processing system for the task of controlling operation of system <NUM>. Computing system <NUM> may include at least one memory <NUM>, processor <NUM>, and input/output (I/O) interface <NUM> interconnected by a bus <NUM>. Further, computing system <NUM> may include communication with external I/O device/resources and/or storage systems, including connected system, such as laser positioning system <NUM>, powder delivery system <NUM>, and build positioning system <NUM>, and network resources. In general, processor <NUM> executes computer program code, such as an additive manufacturing build control program, that is stored in memory <NUM> and/or a storage system. While executing computer program code, processor <NUM> can read and/or write data to/from memory <NUM>, storage systems, and I/O devices (through I/O interface <NUM>). Bus <NUM> provides a communication link between each of the components within computing system <NUM>. I/O devices may comprise any device that enables a user to interact with computing system <NUM> (e.g., keyboard, pointing device, display, etc.). Computing system <NUM> is only representative of various possible combinations of hardware and software. For example, the processor may comprise a single processing unit, or be distributed across one or more processing units in one or more locations, e.g., on a client and server. Similarly, memory and/or storage systems may reside at one or more physical locations. Memory and/or storage systems can comprise any combination of various types of non-transitory computer readable storage medium including magnetic media, optical media, random access memory (RAM), read only memory (ROM), etc. In some embodiments and examples, computing system <NUM> is a laptop computer in communication with laser positioning system <NUM>, powder delivery system <NUM>, and build positioning system <NUM> via a wired (serial, USB, Ethernet, etc.) or wireless (<NUM>, Bluetooth, etc.) connection and running application software for system <NUM>.

In some embodiments and examples, memory <NUM> of computing system <NUM> may include one or more application programs, data sources, and/or functional modules for building an additive component structure on an existing component body. In some embodiments and examples, a pre-existing surface module <NUM> may include a 3D model of component build surface <NUM> that provides surface location information, including edges, surface features, and/or connecting internal features. For example, pre-existing surface module <NUM> may include a CAD file describing component build surface <NUM> and one or more reference locations for laser positioning system <NUM> to direct an additive build on component build surface <NUM>. In some embodiments and examples, an additive design <NUM> may include a 3D model of additive component <NUM> that provides build information for constructing additive component <NUM> on component build surface <NUM>. For example, additive design <NUM> may include a CAD file describing additive component <NUM> (with or without additive supports <NUM>) and material, build layers, and other design information for the additive manufacturing process. In some embodiments and examples, a build control <NUM> may use information from additive design <NUM> and/or pre-existing surface <NUM> to control the additive manufacturing process for additive component <NUM>. For example, build control <NUM> may direct laser positioning system <NUM> to fuse each successive layer of powdered materials in accordance with additive design <NUM> and may also use reference information from pre-existing surface <NUM> to direct powder delivery system <NUM> and build positioning system <NUM>.

Referring to <FIG> and <FIG>, a non-claimed example rotor blade <NUM> made of a pre-existing component and an additive component from an additive manufacturing system, such as system <NUM> in <FIG>, is shown. Rotor blade <NUM> may be comprised of a root or base section <NUM>, an airfoil section <NUM>, and a tip shroud <NUM>. Base section <NUM> may include a base platform <NUM> and a root connector <NUM>, such as a dovetail. Root connector <NUM> may engage a turbine shaft and base platform <NUM> may engage adjacent rotor blades in the same stage to form a ring around the turbine shaft. Base platform <NUM> may define one or more chambers or cooling channels for receiving cooling air into one or more internal features of rotor blade <NUM>. Airfoil section <NUM> may include an airfoil body <NUM> with an external surface <NUM> extending around the lateral perimeter of airfoil body <NUM>. External surface <NUM> may define a pressure side <NUM>, a suction side <NUM>, a leading edge <NUM>, and a trailing edge <NUM> extending from a base interface <NUM> to an outboard tip <NUM>. In the example shown, airfoil body <NUM> may include several areas along a tip portion <NUM> related to the additive manufacture of the outboard tip <NUM> and tip shroud
<NUM>. A build portion <NUM> is part of the pre-existing portion of airfoil body <NUM> that may be exposed above the build plate of an additive manufacturing system and terminate in a component build surface <NUM>. Component build surface <NUM> may define the transition point between the pre-existing portion of airfoil body <NUM> manufactured through conventional casting, machining, and/or other manufacturing processes and an additive structure <NUM> built from component build surface <NUM>. In the example shown, component build surface <NUM> is a substantially planar surface extending to external surface <NUM> in the lateral directions. In some examples, additive structure <NUM> may include an additive airfoil body portion <NUM> extending from component build surface <NUM> to outboard tip <NUM>. The amount of the additive airfoil body portion <NUM> relative to the pre-existing portion of airfoil body <NUM> may depend on individual component design and relative manufacturing considerations between the pre-existing and additive processes. In some examples, additive structure <NUM> may include tip shroud <NUM>, where tip shroud <NUM> is an extension of additive airfoil body portion <NUM> from outboard tip <NUM>. For example, tip shroud <NUM> and additive airfoil body portion <NUM> may form a single additive structure created from successive layers of the same material, with or without overlapping features, during a single additive build session. In some examples, tip shroud <NUM> may be a conventional tip shroud design or a more complex tip shroud with detailed features for airflow, cooling, engaging adjacent tip shrouds or other turbine components, etc. In some examples, tip shroud <NUM> may include lateral extensions <NUM>, <NUM> that extend beyond the adjacent pressure side <NUM> and suction side <NUM> surfaces and may engage adjacent tip shrouds. Tip shroud <NUM> may define external tip shroud surfaces <NUM> on the exterior of the portion of additive structure <NUM> defining tip shroud <NUM>.

In some examples, rotor blade <NUM> may include a plurality of internal air channels <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> extending from base section <NUM>, through airfoil body <NUM>, including additive airfoil body portion <NUM>, and to external tip shroud surfaces <NUM>. Air channels <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may be pre-existing internal features of airfoil body <NUM> that are extended through additive structure <NUM>. Air channels <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may include a pre-existing portion within the pre-existing portion of airfoil body <NUM> and define a plurality of openings in component build surface <NUM>. Air channels <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may be extended to include a portion through additive airfoil body portion <NUM> and tip shroud <NUM>. Air channels <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may define openings in external tip shroud surfaces <NUM> and/or other external surfaces of additive structure <NUM> as discharge ports from the respective air channels <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>.

Referring to <FIG>, another non-claimed example rotor blade <NUM> made of a pre-existing component and an additive component from an additive manufacturing system, such as system <NUM> in <FIG>, is shown in a cross-sectional view. Rotor blade <NUM> may be comprised of a root or base section <NUM>, an airfoil section <NUM>, and a tip shroud <NUM>. Base section <NUM> may include a base platform <NUM> and a root connector <NUM>, such as a dovetail. Base platform <NUM> may define one or more chambers or base air channels <NUM>, <NUM> for receiving cooling air into one or more internal features of rotor blade <NUM>. Airfoil section <NUM> may include an airfoil body <NUM> with an external surface <NUM> extending around the lateral perimeter of airfoil body <NUM>. Airfoil body <NUM> may include a pre-existing portion <NUM> and an additive portion <NUM> with a component build surface <NUM> as the transition between pre-existing portion <NUM> and additive portion <NUM>. In some examples, component build surface <NUM> may be generally parallel to base platform <NUM> and provide a generally uniform height relative to the build direction for additive portion <NUM>. In some examples, component build surface <NUM> may be angled relative to base platform <NUM> and the build direction may be adjusted so that it is perpendicular component build surface <NUM>. Additive portion <NUM> may be an airfoil portion of additive structure <NUM>. Tip shroud <NUM> may be a tip shroud portion <NUM> of additive structure <NUM>. In some examples, additive structure <NUM> may extend only to outbound tip <NUM> and define a tip surface <NUM>. Tip shroud <NUM> may be a separate component fastened to outbound tip <NUM>, rather than a continuous portion of additive structure <NUM>. Airfoil section <NUM> includes a plurality of internal features running through pre-existing portion <NUM> and extended through additive portion <NUM>. Air channels <NUM>, <NUM> may connect to base air channels <NUM>, <NUM> and terminate at various external surfaces, including external surface <NUM> and tip surface <NUM>. In some examples, air channels <NUM>, <NUM> may include trunk channels <NUM>, <NUM> and branch channels <NUM>, <NUM>, <NUM>, <NUM>, <NUM>,
<NUM>, <NUM>, <NUM>, <NUM>. Trunk channels <NUM>, <NUM> may extend through pre-existing portion <NUM> to component build surface <NUM>. Trunk channels <NUM>, <NUM> may continue through additive portion <NUM> as an internal feature of additive structure <NUM>. Trunk channel <NUM> splits into branch channels <NUM>, <NUM>, <NUM> within additive structure <NUM>. Trunk channel <NUM> splits into branch channels <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. In some examples, trunk channels <NUM>, <NUM> each have a lateral width or diameter and branch channels <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may each have a lateral width or diameter and the minimum and maximum widths of these channels may vary. For example, the minimum widths of trunk channels <NUM>, <NUM> may be defined by the process capabilities used to create the pre-existing components and/or prepare component build surface <NUM>. The minimum widths of branch channels <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may be smaller as enabled by the additive manufacturing process used for additive structure <NUM>. For example, trunk channels may have a minimum width of at least <NUM>" or <NUM> millimeters and branch channels may have a minimum width of less than <NUM>" or <NUM>, for example <NUM>" or. In some examples, the network of air channels in additive structure <NUM> may create substantial air space and reduce the metal material in selected cross-section of additive structure <NUM> relative to pre-existing portion <NUM>, giving additive structure <NUM> a lower component density than pre-existing portion <NUM>. In some examples, pre-existing portion <NUM> is comprised of a first metal and additive structure <NUM> is comprised of a second, different metal with different characteristics. Selection of the first metal and second metal may relate to the process capabilities of the respective manufacturing processes and/or different functional characteristics, including strength, ductility, hardness, heat/stress tolerance, density, and compatibility with mechanical features and/or surface treatments. In some examples, additive structure <NUM> may be made of a weight reduced mechanical structure created through additive manufacturing, such as porous matrix or lattice of metal materials. In some examples, pre-existing portion <NUM> may be a portion of a damaged component, such as a rotor blade, and component build surface <NUM> is a prepared surface where a damaged feature has been removed. For example, a worn, corroded, or broken outboard tip may be ground down to remove the compromised portion and the resulting surface prepared for an additive build to replace or augment the removed portion.

Referring to <FIG>, an embodiment of a rotor blade <NUM>, according to the invention, made of a pre-existing component and an additive component from an additive manufacturing system, such as system <NUM> in <FIG>, is shown in a cross-sectional view. Rotor blade <NUM> may be comprised of a root or base section <NUM>, an airfoil section <NUM>, and a tip shroud <NUM>. Base section <NUM> may include a base platform <NUM>. The rotor blade <NUM> includes a root connector <NUM>, such as a dovetail. Base platform <NUM> may define one or more chambers or base air channels <NUM>, <NUM> for receiving cooling air into one or more internal features of rotor blade <NUM>. Airfoil section <NUM> includes an airfoil body <NUM> defining at least one air channel <NUM> with an external airfoil surface <NUM> extending around the lateral perimeter of airfoil body <NUM>. Airfoil body <NUM> includes a pre-existing portion <NUM> and an additive portion <NUM> with a component build surface <NUM> as the transition between pre-existing portion <NUM> and additive portion <NUM>. Component build surface <NUM> may include one or more surface features for assisting with the additive build of additive portion <NUM> by providing additional build surfaces for fusing the two components. For example, component build surface <NUM> may include surface extensions <NUM>, <NUM>, <NUM>, <NUM> providing both distal and lateral contact surfaces for building additive portion <NUM>. Additive portion <NUM> is an airfoil portion of additive structure <NUM> defining at least one air channel <NUM> extending from the component build surface <NUM> to an external surface <NUM> of the additive portion. Tip shroud <NUM> may be a tip shroud portion <NUM> of additive structure <NUM> and define an external shroud surface <NUM>. Airfoil section <NUM> shows a plurality of example internal features in additive portion <NUM>, some of which are continuous with internal features in pre-existing portion <NUM>. Air channels <NUM>, <NUM> may connect to base air channels <NUM>, <NUM> and terminate at various external surfaces, including external airfoil surface <NUM> and external shroud surface <NUM>. The additive portion includes an additive structure <NUM> further defining the at least one air channel <NUM> extending from the component build surface to an external surface of the additive portion. According to an embodiment, air channel <NUM> provides a flow path through pre-existing portion <NUM> and connects to an air chamber <NUM> in additive portion <NUM>. A plurality of smaller air channels <NUM>, <NUM>, <NUM> may provide discharge paths from air chamber <NUM> through external shroud surface <NUM>. Air channel <NUM> may provide a flow path into a matching air channel <NUM> through additive portion <NUM> to a discharge opening <NUM> in external airfoil surface <NUM>. Note that it does not connect to chamber <NUM>. In some embodiments, chamber <NUM> may be an isolated internal feature of additive structure <NUM> for mass (density) reduction toward the outboard end of rotor blade <NUM>. According to an embodiment, chambers <NUM>, <NUM> in additive structure <NUM> create substantial air space and reduce the metal material in a selected cross-section of additive structure <NUM>
relative to pre-existing portion <NUM>, giving additive structure <NUM> a lower component density than pre-existing portion <NUM>.

Referring to <FIG>, another non-claimed example rotor blade <NUM> made of a pre-existing component and an additive component from an additive manufacturing system, such as system <NUM> in <FIG>, is shown in a cross-sectional view. Rotor blade <NUM> may be comprised of a root or base section <NUM>, an airfoil section <NUM>, and a tip shroud <NUM>. Base section <NUM> may include a base platform <NUM> and a root connector <NUM>, such as a dovetail. Base platform <NUM> may define one or more chambers or base air channels <NUM>, <NUM> for receiving cooling air or other fluids into one or more internal features of rotor blade <NUM>. Airfoil section <NUM> may include an airfoil body <NUM> with an external airfoil surface <NUM> extending around the lateral perimeter of airfoil body <NUM>. Airfoil body <NUM> may include a pre-existing portion <NUM> and an additive portion <NUM> with a component build surface <NUM> as the transition between pre-existing portion <NUM> and additive portion <NUM>. In some examples, component build surface <NUM> may be oriented along a radius of rotor blade <NUM> or parallel to an edge, such as a leading or trailing edge, for additive features clustered along an edge. Additive portion <NUM> may be an edge additive structure <NUM>. Tip shroud <NUM> may be a separate component attached to a distal tip surface <NUM>. In some examples, distal tip surface <NUM> is defined by distal portions of pre-existing portion <NUM> and additive portion <NUM>. Airfoil section <NUM> shows a plurality of example internal features in additive portion <NUM>, which may be continuous with internal features in pre-existing portion <NUM>. Air channels <NUM>, <NUM> may connect to base air channels <NUM>, <NUM> and terminate at various external surfaces, including external airfoil surface <NUM> and distal tip surface <NUM>. Air channel <NUM> may provide a flow path entirely through pre-existing portion <NUM> to a discharge opening in distal tip surface <NUM>. Air channel <NUM> may flow through both pre-existing portion <NUM> and additive portion <NUM>. In some examples, air channel <NUM> may be a trunk channel connected to a plurality of smaller branch air channels <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. Branch air channels <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may provide discharge paths from air channel <NUM> through external airfoil surface <NUM> on additive potion <NUM> and distal tip surface <NUM>.

The terminology used herein is for the purpose of describing particular embodiments and examples only and is not intended to be limiting of the disclosure.

Claim 1:
A rotor blade (<NUM>) comprising:
a root connector (<NUM>) configured to engage a turbine shaft of a turbomachine;
an airfoil extending from the root connector (<NUM>), the airfoil including an airfoil body (<NUM>), the airfoil body (<NUM>) comprising a pre-existing portion (<NUM>) and a component build surface (<NUM>), the airfoil body (<NUM>) defining at least one air channel (<NUM>) enclosed within the airfoil body (<NUM>) and extending to the component build surface (<NUM>); and
an additive portion from the component build surface (<NUM>) of the airfoil body (<NUM>), the additive portion including an additive structure (<NUM>) further defining the at least one air channel (<NUM>) extending from the component build surface (<NUM>) to an external surface (<NUM>) of the additive portion, the airfoil including a pressure side (<NUM>) wall and a suction side (<NUM>) wall that define an outer surface and an outboard tip, the airfoil body (<NUM>) terminating in the component build surface (<NUM>) prior to the outboard tip and the additive portion including the outboard tip; wherein the additive portion further includes at least one internal air chamber (<NUM>) (<NUM>) having a lateral cross-section greater than a largest width of the at least one air channel (<NUM>) and a total component density of the additive structure (<NUM>) is less than a total component density of the airfoil body (<NUM>).