Patent Description:
Investment casting is a commonly used technique for forming metallic components having complex geometries. The manufacture of gas turbine components or parts, such as turbine blades and nozzles, requires that the parts be manufactured with accurate dimensions having tight tolerances, making investment casting suitable for manufacturing these parts. In general, investment casting involves preparing a ceramic mold for creating a part or product design. Preparing the ceramic mold involves the use of one or more wax patterns of the part. The wax patterns are formed by molding wax into a shape generally corresponding to a positive of the part. If the part is intended to have interior passages, the wax patterns are formed around an internal ceramic core with a shape generally corresponding to the interior passages. Using a shelling process, a ceramic shell is formed around one or more of such wax patterns. After formation of the ceramic shell, the wax may be removed by melting, leaving a ceramic mold of the part. The part is cast by filling the ceramic mold with molten metal. Upon cooling and solidifying of the metal, the ceramic shell may be mechanically and/or chemically removed from the molded part. The part can then be machined and/or processed in one or more steps to obtain the part specified in the product design. If the part is not properly supported during this process the parts fabricated will not meet the specified product design requirements.

During the shelling process the part is dipped into a ceramic slurry that can be agitated or stagnant, and coated with refractory sand to form a hard exterior shell around the patterns. Stress induced on the part during this process can break the wax component or cause a crack to form in the shell that may lead to a defect in the casting. Typically, the wax patterns are assembled with supports into structures or wax "trees," which are turned upside down, dipped in the ceramic slurry, and coated with the refractory sand in multiple iterations or cycles to form layers that create the ceramic shell.

If the wax patterns are not sufficiently supported, the patterns can break due to the loads created during the shelling process. In particular, after each layer is gathered around the wax patterns, more weight is applied to the wax patterns, increasing the load on the patterns. However, after several layers are formed around the wax patterns, the ceramic shell that is shaping also becomes stronger and eventually becomes self-sustaining in terms of rigidity to form a structural component that can withstand the weight of the additional layers that are formed thereon.

Up until the point that the wax patterns have enough layers to withstand the weight of the additional layers that arise from the slurry and sand, the wax patterns are subject to breaking. A broken wax pattern can result in the loss of the pattern, an improperly shaped ceramic shell, and or a discontinuity in the shell that could affect the casting process and therefore, cast part. In addition, and particularly for the case of directionally solidified or single crystal castings where a specific grain structure and metallurgy are required, the support structures attached to the wax pattern can themselves affect the casting and solidification process, and therefore, the shape and quality of the cast part. Consequently, a significant challenge in the art of investment casting is the design of support structures which are sufficiently strong to maintain the shape and integrity of the wax pattern and tree during the shelling process, but which minimize the impact on the solidification and casting process.

<CIT> discloses an apparatus to support a wax pattern of a part that is to be cast to a base plate during an investment casting process of the part. The apparatus comprises a solid support block extending from the base plate and presenting a concave depression at its top with an outline that is complementary to the outline of the bottom end of the wax pattern, wherein the support block with the concave depression secure the wax pattern to the base plate in a fixed position and distribute the load of the wax pattern while secured to the base plate.

<CIT> discloses an apparatus to support a wax pattern of a turbomachine part to a base plate during an investment casting process of the turbomachine part, comprising a support structure in the form of a socket that matches a shape of a surface of the wax pattern and having a peripheral edge that connects the socket to the base plate to secure the wax pattern to the base plate and distribute the load of the wax pattern.

<CIT> discloses an apparatus to support a wax pattern of a part to a base during an investment casting process of the part, the part comprising several blade wax models arranged and fixed end to end, and a metal alloy distribution element having an alloy inlet airlock and a baffle for directing the metal alloy particles to obtain blades having a desired crystallization. The apparatus comprises support and locking means that is substantially parallelepiped and comprises a first part extending from the base and a second part articulated relative to each other by a hinge, the two parts defining a cavity therebetween, which receives the alloy inlet airlock when the two parts are in contact with each other.

<CIT> discloses an apparatus and method for forming a ceramic shell mould with a plurality of angled support columns that connect the shell mould to the base plate. The support columns are created by arranging solid ceramic rods or support sticks from rod wax between the chassis (basis) wax pattern and the blade wax pattern in an angled orientation relative thereto and spaced to each other before the ceramic shell mould is formed about the blade wax pattern.

<CIT> discloses support columns which are arranged between the base and the ceramic shell mould after the ceramic shell mould has been finished in a shelling process. The support columns are formed from support wax patterns, which are placed between the blade wax patterns and the base wax pattern in a spaced arrangement from the blade wax pattern.

<CIT> discloses a support structure in the form of rod-shaped support wax elements connected to a mold model and a sprue.

The following presents a simplified summary of the disclosed subject matter in order to provide a basic understanding of some aspects of the various embodiments described herein. This summary is not an extensive overview of the various embodiments. It is not intended to exclusively identify key features or essential features of the claimed subject matter set forth in the Claims, nor is it intended as an aid in determining the scope of the claimed subject matter. Its sole purpose is to present some concepts of the disclosure in a streamlined form as a prelude to the more detailed description that is presented later.

The various embodiments of the present invention are directed to providing a solution that addresses the breakage issues that can arise during the shelling process of wax patterns while assembled to a tree due to the loads applied to the wax patterns during the ceramic slurry dipping and refractory sand coating steps of the shelling process, and to do so in a manner that has minimum impact on the casting process. The solution provided by the various embodiments includes a support structure to support the wax patterns during investment casting. The support structure of the various embodiment provides a more robust connection of the wax patterns while assembled to the tree that can better withstand the dipping in the ceramic slurry and coating with the refractory sand while undergoing the shelling process. This minimizes disruption of the investment casting due to breakage of the wax patterns that can occur during the shelling process or due to the impact of support structures on the solidification process.

The support structure of the various embodiments includes a support structure that can be applied to any location about the wax pattern. The support structure of the various embodiments can uniformly distribute forces applied to the wax pattern from shelling to minimize risk of deformation or breakage, and also to minimize attachments and intrusion to the pattern which could affect the casting process.

The support structure includes a support capping structure placed on a surface of a lower region of the wax pattern. The support capping structure has a geometry that matches a profile of the lower region of the wax pattern. To this extent, the support capping structure forms a defined envelope around the surface of the wax pattern after placement thereon, which uniformly distributes forces applied to the wax pattern from shelling to minimize risk of deformation or breakage, and also to minimize attachments and intrusion to the pattern which could affect the casting process. The defined envelope is formed around the bottom surface of the wax pattern and extends upward to enclose a lower region of the wax pattern. The support structure further includes a plurality of support braces to support the support capping structure with respect to the lower region of the wax pattern. The support structure includes a plurality of support braces extending outward from the support capping structure.

The support structure of the various embodiments can be formed with an additive manufacturing process. In one embodiment, the additive manufacturing process can include three-dimensional (3D) printing. To this extent, the components of the support structure such as the support capping structure and the support brace(s) can be additive printed. For example, the 3D printing additive manufacturing process can ensure that the support capping structure is formed to match the shape of the bottom surface of the wax pattern and/or the lower region of the wax pattern so that it can fit over these parts of the wax pattern. A 3D printing additive manufacturing process to generate the support structure is preferable because of its customizable ability to form a support structure with a desired profile. In addition, 3D printing additive manufacturing makes it easy to duplicate the printed design and use it across multiple part configurations. Nevertheless, other embodiments can use hard or temporary tooling to form the support structure described herein.

In one embodiment in which the support structure is the aforementioned support capping structure, 3D printing additive manufacturing can be used to precisely match the surface of the lower region of the wax pattern providing a conformal cap that distributes the load and provides attachment points that are not intrusive to the wax pattern.

After formation of the support capping structure, it is placed on the surface of the lower region of the wax pattern to enclose this part of the wax pattern per the envelope. The support capping structure is connected to a base plate used in the investment casting process to support the wax pattern and any other similar wax patterns assembled to a tree that connects to the base plate. In particular, the support braces of the support structure of each wax pattern assembled with the tree are connected to the base plate. Of the plurality of support braces utilized, each of the braces is angled to the support capping structure and the base plate. In addition, each of the plurality of support braces can be spaced apart from one another at the support capping structure and the base plate. For example, the spacing between each of the support braces at the base plate can be greater than the spacing of each of the support braces at the support capping structure. This allows the support braces to provide support in multiple directions.

While secured to the base plate, the support capping structure and the plurality of support braces can uniformly distribute the load of the wax pattern. With this configuration of the support structure and its coupling of the wax pattern and the base plate, the support capping structure will support a greater portion of the load of the wax pattern as compared to a portion of the load supported by the plurality of support braces. Furthermore, the force of the load of the wax pattern received by the support capping structure is distributed evenly against the bottom surface and/or the lower region of the wax pattern. Also, the angling of the support braces to the support capping structure and the base plate allows the support capping structure to provide more mechanical leverage in this supported configuration.

With the capability to uniformly distribute the load of the wax pattern such that the support capping structure supports a greater portion of the load and evenly distributes it against the bottom surface and/or lower region of the wax pattern, the solution offered by the various embodiments reduces the risk of breakage of the wax pattern during the shelling process of the pattern. Further, because the support structure, and in particular, the support capping structure, matches the geometry of the bottom surface and/or lower region of the wax pattern, the risk that the support structure will break during the shelling process is minimal. In particular, during the shelling process, the entire wax pattern, including the wax pattern and the support structure, will be covered in multiple layers of ceramic slurry before the wax is subsequently removed through melting in a dewaxing process. The consequential effect is that the inner surface of the casting transitions smoothly from the inside of the support capping structure to the inside of the shell with no discernible thermal or geometric impact on the casting that can lead to breakage, and thus, interruption of the investment casting of the part.

Furthermore, the configuration of this embodiment as well as the other various embodiments of the present invention can achieve uniform loading and improved support of the wax pattern without the direct attachment of wax supports to the wax pattern or invasive ceramic supports that extend into or through the wax pattern, which are common features associated with conventional approaches used to support a wax pattern during investment casting. Having wax supports that directly attach to the wax pattern or ceramic supports that extend into or through the wax pattern create nonuniformities with the support of the wax pattern. Each such nonuniformity is a risk that could degrade the grain structure of the wax pattern. The various embodiments obviate this risk by providing a support structure that not only supports the pattern, but does so without any components sticking into or out of the wax pattern.

In accordance with a first aspect of the invention, as claimed in independent claim <NUM>, an apparatus to support a wax pattern of a part that is to be cast to a base plate during an investment casting process of the part is provided. The apparatus comprises: a support structure placed about the wax pattern, wherein the support structure matches a shape of a surface of the wax pattern, and wherein the support structure forms a defined envelope around the surface of the wax pattern after placement thereon, wherein the defined envelope is formed around a bottom surface of the wax pattern and extends upward to enclose a lower region of the wax pattern, wherein the support structure comprises: a support capping structure that is placed on the bottom surface about the lower region of the wax pattern and has a shape that matches the bottom surface of the wax pattern; and a plurality of support braces extending outward from the support capping structure to connect to the base plate, wherein the plurality of support braces is in the form of ceramic posts that are arranged between and connected to the support capping structure and the base plate, wherein each of the support braces is angled to the support capping structure and the base plate, wherein the support capping structure and the plurality of support braces secure the wax pattern to the base plate in a fixed position and distribute the load of the wax pattern while secured to the base plate.

In accordance with another aspect of the invention, as claimed in independent claim <NUM>, a method for supporting a wax pattern of a part during an investment casting process of the part is provided. The method comprises: forming a support structure to support the wax pattern during the investment casting of the part, wherein the support structure comprises a support capping structure with a geometry that matches a profile of a lower region of the wax pattern, and a plurality of support braces extending outward from the support capping structure; placing the support structure about the wax pattern by placing the support capping structure on a bottom surface about the lower region of the wax pattern, wherein the support capping structure forms a defined envelope around the lower region of the wax pattern after placement thereon; and connecting the support capping structure to a base plate by the plurality of support braces, wherein the plurality of support braces is in the form of ceramic posts that are arranged between and connected to the support capping structure and the base plate, wherein each of the support braces is angled to the support capping structure and the base plate, and wherein the support capping structure and the plurality of support braces secure the wax pattern to the base plate in a fixed position and uniformly distribute the load of the wax pattern while secured to the base plate.

In accordance with third aspect of the invention, as claimed in independent claim <NUM>, a method is provided. The method comprises: obtaining a wax pattern of a part; printing a support structure to support the wax pattern with an additive manufacturing process, wherein the support structure comprises a support capping structure with a geometry that matches a profile of a lower region of the wax pattern, and a plurality of support braces extending outward from the support capping structure; placing the support structure about the wax pattern by placing the support capping structure on a bottom surface about the lower region of the wax pattern, wherein the support capping structure forms a defined envelope to enclose the lower region of the wax pattern after placement thereon; connecting the support capping structure to a base plate by the plurality of support braces, wherein the plurality of support braces is in the form of ceramic posts that are arranged between and connected to the support capping structure and the base plate, wherein each of the support braces is angled to the support capping structure and the base plate, and wherein the support capping structure and the plurality of support braces secure the wax pattern to the base plate and uniformly distribute the load of the wax pattern while secured to the base plate; and creating a mold shell that surrounds the wax pattern and the support structure while the wax pattern is secured to the base plate.

Example embodiments of the present invention will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments are shown. Indeed, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. For like numbers may refer to like elements throughout.

As indicated above, this disclosure relates generally to investment casting, and more specifically, to providing a support structure for supporting a wax pattern during investment casting of a part. The description of the various embodiments that follows is directed to the casting of a turbine part such as a gas turbine part. Examples of gas turbine parts that can be investment casted with the use of a support structure described herein can include, but are not limited to, turbine blades and nozzles. It is understood that other parts or components in the hot gas path of a gas turbine system that are typically produced by investment casting are applicable for use with the support structure of the various embodiments. Furthermore, although the description of the various embodiments is described with respect to turbine parts, it is not meant to be limiting. The support structure and methods associated therewith are suitable for use with the investment casting of any part or component that can be prone to breakage during the shelling process of investment casting in which a wax pattern(s) of a part undergoes dipping in an agitated or stagnant ceramic slurry and coating with refractory sand to form a ceramic shell that encloses the wax pattern(s).

Turning now to the figures, <FIG> shows a schematic of a support structure <NUM> for supporting a wax pattern of a part that is to be cast in an investment casting process according to the prior art. As mentioned above, during the shelling process of the investment casting of a part, the wax patterns are subject to breakage during the dipping in the ceramic slurry and coating with the refractory sand due to the loads applied to the wax patterns. The support structure <NUM> depicted in <FIG> shows one approach that has been used to support a wax pattern <NUM> of a gas turbine part (e.g., a blade wax pattern). The support structure <NUM> of <FIG> includes wax connector joints <NUM> secured to the wax pattern <NUM> at one or two locations about the lower region <NUM> of the wax pattern <NUM>. <FIG> also includes for completeness a feed runner <NUM> through which molten alloy is supplied to the mold and a seed selector <NUM> which initiates crystal growth and the solidification process. As shown in <FIG>, the wax connectors <NUM> are secured directly to the "the wax pattern <NUM>.

The support structure <NUM> of <FIG> further includes connecting legs <NUM> extending vertically downward from each of the wax connector joints <NUM> to a base plate <NUM> that is used to secure a tree <NUM> having the feed runner <NUM> to deliver the metal or alloy to each of the wax patterns <NUM> assembled to the tree <NUM> in the metal casting of the investment casting process. As shown in <FIG>, the feed runner <NUM> is operatively coupled to the tree <NUM> via a vertical member <NUM> of the tree that can allow for horizontal bracing to be applied such as with the feed runner. The connecting legs <NUM> can include standardized rods that hold up the wax pattern <NUM> with respect to the base plate <NUM>. Although the tree <NUM> depicted in <FIG> only shows one wax pattern <NUM>, the tree can include more wax patterns spaced apart from each other. For example, the tree <NUM> can have three or more wax patterns <NUM> of the gas turbine part, with each of these patterns separated by predetermined spacing. In addition, it is understood that each of these wax patterns <NUM> would have a support structure <NUM> that secures and supports the wax patterns on the tree <NUM> to the base plate <NUM>.

In the shelling process, the tree <NUM> is turned upside down and dipped into a ceramic slurry and coated with refractory sand in a multiple of iterations to form a hard exterior shell around the wax patterns <NUM> that includes a multiple of layers. The assembly of the tree <NUM> with one or more wax patterns <NUM> secured to the base plate <NUM> can be heavy enough that the patterns can break during the dipping in the ceramic slurry and coating with the refractory sand due to the loads applied to the wax patterns. In particular, in this configuration, the wax connector joints <NUM> are one area where the breakage can occur. This breakage at the "hips" of the wax pattern <NUM> can be frequent. As a result, the failure of the support structure <NUM> to support the wax pattern can be disruptive to the investment casting process of the part formed from the wax patterns. Not only are the wax connector joints <NUM> a fragile part of the design of the support structure <NUM>, but the connecting legs <NUM> of the support structure provide only a limited amount support for loads that are normal to the surface of the wax pattern <NUM> during the shelling process. Consequently, stresses arise on the wax connector and frequently cause cracking and failure that ultimately leads to the breakage of the pattern during the shelling process. In addition, due to the location and design of the wax connector joints <NUM>, a discontinuous wax surface can take form at the joints which can lead to poor casting grain structure.

The support structure and method of generating the support structure of the various embodiments overcome the weakness of the support structure <NUM> depicted in <FIG> by providing a more robust connection, which equates to minimal disruption to the investment casting process. In one embodiment, the support structure includes a support capping structure which has a thin walled shell of ceramic formed to match the shape of the lower region of the wax pattern representative of the part to be cast. In the various embodiments of the present invention, having the support structure match the shape of a region of the wax pattern means that the support structure has a shape that is approximately the same geometric surface profile as the region of the wax pattern that is most adjacent to the support structure. In the case of a turbine blade, the support capping structure, in one embodiment, can be fitted over the tip of the blade. Fitting over the tip in this manner, enables the support capping structure to provide uniform and distributed support to the wax pattern without creating a discontinuity in the wax surface. The support capping structure is braced to the underlying base plate with support braces that include ceramic posts. To this extent, the support structure of the various embodiments can hold the fragile wax pattern with a more uniformly distributed load and stronger materials due to the ceramic capping structure enclosing the tip, while the support braces, secured to the base plate, can provide support in multiple directions. Further, an additive manufacturing process such as three-dimensional (3D) printing ensures that the support capping structure is printed to match the shape of the blade (i.e., the part embodied by the wax pattern). As a result, there is a reduced risk of the capping structure or the supports braces breaking.

<FIG> show various views of a support structure <NUM> for supporting the wax pattern <NUM> of the turbine part according to an embodiment of the invention. As shown in these figures, the support structure <NUM> includes a support capping structure <NUM> placed on a bottom surface <NUM> about the lower region <NUM> of the wax pattern <NUM>. The support capping structure <NUM> has a shape that matches the bottom surface <NUM> of the wax pattern <NUM>. In particular, the support capping structure <NUM> can have a geometry that matches a profile of the lower region <NUM> of the wax pattern <NUM>. For example, the geometry of the support capping structure <NUM> matches the profile of the tip of the turbine blade. In this manner, the support capping structure <NUM> is placed over the bottom surface <NUM> of the wax pattern <NUM> at the lower region <NUM> of the wax pattern. To this extent, the support capping structure <NUM> forms a defined envelope (i.e., an enclosing structure) <NUM> around the bottom surface <NUM> of the wax pattern <NUM>. As shown in <FIG>, the defined envelope <NUM> formed around the bottom surface <NUM> of the wax pattern <NUM> extends upward to enclose the lower region <NUM> of the wax pattern.

To this extent, the support capping structure <NUM>, when placed over the bottom surface <NUM> of the wax pattern <NUM> around the lower region <NUM> of the tip, provides uniform and distributed support of this tip region of the turbine part. That is, the support capping structure <NUM> can receive the force of the load of the wax pattern <NUM> and distribute it evenly against the bottom surface <NUM> of the wax pattern <NUM> at the lower region <NUM>. This is advantageous for loads that are normal to the wax pattern <NUM> because the support structure of these embodiments can fully support normal loads and not provide only limited support like the structure of <FIG>. As a result, the support capping structure <NUM> can support a much greater load because the force is evenly distributed against the tip surface of the wax pattern <NUM> with a continuous ceramic interface.

In one embodiment, the support capping structure <NUM> can be formed from an additive manufacturing process. For example, 3D printing can be used to print the support capping structure <NUM> with ceramic material that has a geometry that matches that profile of the lower region <NUM> of the wax pattern <NUM> (e.g., the tip). In one scenario, a ceramic tip cap can be printed in a, layer wise fashion, using a lithographic method, described in <CIT>, by using ceramic slurry composed of a material suitable for investment casting temperatures and environmental conditions including, but not limited to Alumina, Silica, Zirconia, and Yittria matching the thermal expansion of the shelling material. This can also be extended to other 3D printing modalities including, but not limited to, Binder Jet and Fused Deposition Modeling.

It is preferable to print the support capping structure <NUM> with a ceramic because of its strength and suitability to operate in a high temperature settings. Examples of ceramic material suitable for printing the support capping structure <NUM> can include, but are not limited to, Alumina, Silica, Zirconia, Yittria and or combinations of these constituents matching the thermal expansion of the shelling material. Although it is preferable to use ceramic material to print the support capping structure <NUM>, the use of other materials may be possible.

The use of 3D printing to generate the support structure <NUM> including the support capping structure <NUM> is not meant to be limiting. Other additive manufacturing processes can be used to generate the support structure <NUM> including the support capping structure <NUM>. These other additive manufacturing processes can include, but are not limited to, powder bed fusion, direct metal laser melting, electron beam melting, and binder jetting.

It is understood that the support structure <NUM> including the support capping structure <NUM> can be generated using other approaches. In one embodiment, hard or temporary tooling can be used to form the support structure <NUM>. For example, the capping structure <NUM> can itself be cast or formed from an injection molded ceramic. This can be advantageous in scenarios where there is a need to generate a large volume of prototypes.

It is understood that the support capping structure <NUM> depicted in <FIG>, is not meant to be limiting to the embodiments described herein. The support capping structure <NUM> of these figures illustrates only one possibility of supporting the tip region of the turbine part in a way that can uniformly distribute the load of the wax pattern <NUM> against the lower region <NUM>. Those skilled in the art will appreciate that a support structure can be extended up further along the lower region <NUM> of the wax pattern <NUM> to provide an additional amount of support. In other embodiments, the support structure can be shaped differently than the cup-like geometry depicted in <FIG>. For example, the support structure can take the form of a ring that encircles the lower region <NUM> of the wax pattern <NUM>. In this manner, the ring can encircle the lower region <NUM> with the bottom surface <NUM> not covered by the ring. In another embodiment, the support structure can have forked-shaped structures to support the lower region <NUM> of the wax pattern <NUM>. In essence, the support structure of the various embodiments can be applied to any location about the wax pattern. In one example in which the turbine part is a turbine blade, the support structure can be placed at a region around the platform of the blade. In another example, a support structure can be created that connects the wax pattern <NUM> to the down pole (i.e., the vertical member <NUM>) of the tree <NUM> giving the pattern cross bracing.

Moreover, for embodiments in which the wax pattern takes on the shape of a different part, including other gas turbine parts, as well as any other part or component outside of the gas turbine realm, it is understood that the shape and placement of a support structure used to provide uniform and distributed support will depend on the profile and shape that is associated with the pertinent part or component.

Referring back to <FIG>, the support structure <NUM> includes a plurality of support braces to support the support capping structure <NUM> with respect to the lower region of the wax pattern <NUM>. In one embodiment, as shown in <FIG>, the support structure <NUM> includes the plurality of support braces <NUM> extending outward from the support capping structure <NUM>, about a grain starter hole <NUM> (<FIG>) where the grain starter is connected to the wax pattern <NUM>, to connect to the base plate <NUM>. In this manner, the support capping structure <NUM> and the plurality of support braces <NUM> secure the wax pattern <NUM> to the base plate <NUM> in a fixed position. This allows the load of the wax pattern <NUM> to be uniformly distributed while secured to the base plate.

In one embodiment, the support braces <NUM> can include struts, rods, legs and the like. The support braces <NUM> can include off-the-shelf components or they can be printed with a ceramic material using any of the aforementioned additive manufacturing processes. Also, the support braces <NUM> can be cast themselves. Regardless of whether the support braces <NUM> are printed using an additive manufacturing process, cast, or obtained as off-the-shelf components, the braces are used to hold the wax pattern <NUM> and the support capping structure <NUM> placed thereon in a fixed position with respect to the base plate <NUM> and the tree that contains the wax pattern and any other patterns.

In one embodiment, the support capping structure <NUM> can include brackets <NUM> to receive each of the support braces <NUM>. The brackets <NUM> can be formed on the support capping structure <NUM> as part of the additive manufacturing process used to print the support capping structure. In this manner, one end of the support braces <NUM> can be received and secured within the brackets <NUM>, while the other end of the braces can be received and secured to the base plate <NUM>. It is understood that the brackets <NUM> represent one mechanism for receiving and securing the braces <NUM> and are not meant to be limiting.

<FIG>, <FIG> and <FIG> shows that the support braces <NUM> are positioned about the support capping structure <NUM> and the base plate <NUM> in a manner that enhances the capability of the support structure <NUM> to uniformly distribute the load of the wax pattern <NUM> while secured to the base plate <NUM>. Each of the support braces <NUM> is angled to the support capping structure <NUM> and the base plate <NUM>. For example, each of the support braces <NUM> can be spaced apart from one another at the support capping structure <NUM> and the base plate <NUM> in a tripod configuration (e.g., <NUM> support braces) to provide support from a multiple of different directions. This allows the support braces <NUM> to be angled to the base plate <NUM> from a single location while still staying within the defined allowed envelope <NUM> of the wax pattern <NUM> at the other end.

In one embodiment, the spacing between each of the support braces <NUM> at the base plate <NUM> can be greater than the spacing of each of the support braces at the support capping structure <NUM>. With this configuration, the support capping structure <NUM> can support a greater portion of the load of the wax pattern <NUM> than a portion of the load supported by the support braces <NUM>.

<FIG> shows a flow chart <NUM> illustrating the operations associated with the investment casting of a part from a wax pattern that can be supported by the support structure <NUM> depicted in <FIG>. In the flow chart of <FIG>, the first step is to obtain a wax pattern of a part at <NUM>. The wax pattern will have the same details as the finished part. For example, the wax pattern of a turbine part can have the same shape except that there is an allowance for thermal contraction. In one embodiment, the wax pattern can be made with the use of a metal injection die.

The support structure used to support the wax pattern is generated at <NUM>. The support structure is printed with an additive manufacturing process. As described herein, the printed support structure has a support capping structure with a geometry that matches a profile of a lower region of the wax pattern, and support braces that extend outward from the support capping structure.

The support structure is placed about a surface of the wax pattern at <NUM>. The support structure is placed on a bottom surface of the wax pattern. In particular, the support structure is placed on the lower region of the wax pattern. As mentioned above, the support structure is shaped in a manner that matches the lower region of the wax pattern, and positioned such that the load of the pattern can be evenly distributed against the lower region of the pattern. The support capping structure forms a defined envelope around the bottom surface of the wax pattern that extends upward to enclose the lower region of the wax pattern after placement thereon. In another embodiment, the support capping structure forms a defined envelope to enclose the lower region of the wax pattern upon placement thereon.

Next, the support structure is connected to the base plate at <NUM>. In one embodiment, the support braces connect to the base plate at one end and to the support capping structure at another end. In this manner, the support capping structure and the support braces secure the wax pattern to the base plate and uniformly distribute the load of the wax pattern while secured to the base plate.

With this assembly, the tree with the wax patterns and respective support structures affixed thereto can undergo a shelling process at <NUM>. In particular, a mold shell is created that surrounds the wax patterns and the support structure while the wax patterns are secured to the base plate. As noted previously, this can include turning the tree of wax patterns upside down and dipping them in a ceramic slurry and then coating with refractory sand. The dipping and coating is repeated until a shell with multiple layers is formed to have the desired thickness. The thickness can be dictated by the part size and configuration. Once the ceramic shell has dried, it is able to retain the molten metal during casting.

Each wax pattern and the support structure can be removed from the mold shell at <NUM>. In one embodiment, the entire assembly of wax patterns and respective support structures can be placed in a steam autoclave to melt away most of the wax. Any remaining wax soaked into the ceramic shell can be burned out in a furnace. At this point, the ceramic mold remains with a cavity in the shape of the desired cast part.

The ceramic mold shell can then be filled with a molten metal to cast the part at <NUM>. In one embodiment, the ceramic mold shell can be heated to a specific temperature and filled with molten metal, creating the metal casting.

Once the casting has cooled sufficiently, the ceramic mold shell can be broken away from the casting in a knockout operation at <NUM>. In one embodiment, the runner can be cut from the casting. If necessary, final post-processing operations that can include, but are not limited to, sandblasting, grinding, and machining can be performed to finish the casting dimensionally.

While, for purposes of simplicity of explanation, the operations shown in <FIG> are described as a series of acts. It is to be understood and appreciated that the subject innovation associated with <FIG> is not limited by the order of acts, as some acts may, in accordance therewith, occur in a different order and/or concurrently with other acts from that shown and described herein. For example, those skilled in the art will understand and appreciate that a methodology or operations depicted in <FIG> could alternatively be represented as a series of interrelated states or events, such as in a state diagram. Moreover, not all illustrated acts may be required to implement a methodology in accordance with the innovation. Furthermore, interaction diagram(s) may represent methodologies, or methods, in accordance with the subject disclosure when disparate entities enact disparate portions of the methodologies. Further yet, two or more of the disclosed example methods can be implemented in combination with each other, to accomplish one or more features or advantages described herein.

Accordingly, it should be apparent that the support structure described herein, as well as the method steps used to create the support structure, and implement such structure in an investment casting process, are amenable for industrial application in that it relates to the technical field of casting parts and components of a variety of shapes, and present a solution to a technical problem of breakage of a wax pattern during the shelling process of the pattern. The use of the support structure described herein can provide a more robust connection with the wax pattern and base plate that minimizes the likelihood that breakage will occur during the shelling process of investment casting in which the wax pattern undergoes dipping in a ceramic slurry and coating with refractory sand to form a ceramic shell that encloses the wax pattern.

The above description of illustrated embodiments of the subject disclosure, including what is described in the Abstract, is not intended to be exhaustive or to limit the disclosed embodiments to the precise forms disclosed. While specific embodiments and examples are described herein for illustrative purposes, various modifications are possible that are considered within the scope of such embodiments and examples, as those skilled in the relevant art can recognize. For example, parts, components, steps and aspects from different embodiments may be combined or suitable for use in other embodiments even though not described in the disclosure or depicted in the figures. Therefore, since certain changes may be made in the above-described invention, without departing from the scope of the invention as defined by the appended claims, it is intended that all of the subject matter of the above description shown in the accompanying drawings shall be interpreted merely as examples illustrating the inventive concept herein and shall not be construed as limiting the invention.

In this regard, while the disclosed subject matter has been described in connection with various embodiments and corresponding figures, where applicable, it is to be understood that other similar embodiments can be used or modifications and additions can be made to the described embodiments for performing the same, similar, alternative, or substitute function of the disclosed subject matter without deviating therefrom. For example, references to "one embodiment" of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

In the appended claims, the terms "including" and "in which" may be used as the plain-English equivalents of the respective terms "comprising" and "wherein. " Moreover, in the following claims, terms such as "first," "second," "third," "upper," "lower," "bottom," "top," etc. are merely labels, and are not intended to impose numerical or positional requirements on their objects. The terms "substantially," "generally," and "about" indicate conditions within reasonably achievable manufacturing and assembly tolerances, relative to ideal desired conditions suitable for achieving the functional purpose of a component or assembly. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted as such, unless and until such claim limitations expressly use the phrase "means for" followed by a statement of function void of further structure.

What has been described above includes examples of systems and methods illustrative of the disclosed subject matter. It is, of course, not possible to describe every combination of components or methodologies here. One of ordinary skill in the art may recognize that many further combinations and permutations of the claimed subject matter are possible. Furthermore, to the extent that the terms "includes," "has," "possesses," and the like are used in the detailed description, claims, appendices and drawings, such terms are intended to be inclusive in a manner similar to the term "comprising" as "comprising" is interpreted when employed as a transitional word in a claim. That is, unless explicitly stated to the contrary, embodiments "comprising," "including," or "having" an element or a plurality of elements having a particular property may include additional such elements not having that property.

Claim 1:
An apparatus (<NUM>) to support a wax pattern (<NUM>) of a part that is to be cast to a base plate (<NUM>) during an investment casting process of the part, the apparatus (<NUM>) comprising:
a support structure (<NUM>) placed about the wax pattern (<NUM>), wherein the support structure (<NUM>) matches a shape of a surface of the wax pattern (<NUM>), and wherein the support structure (<NUM>) forms a defined envelope (<NUM>) around the surface of the wax pattern (<NUM>) after placement thereon, wherein the defined envelope (<NUM>) is formed around a bottom surface (<NUM>) of the wax pattern (<NUM>) and extends upward to enclose a lower region (<NUM>) of the wax pattern (<NUM>), wherein the support structure (<NUM>) comprises:
a support capping structure (<NUM>) that is placed on the bottom surface (<NUM>) about the lower region (<NUM>) of the wax pattern (<NUM>) and has a shape that matches the bottom surface (<NUM>) of the wax pattern (<NUM>), and
a plurality of support braces (<NUM>) extending outward from the support capping structure (<NUM>) to connect to the base plate (<NUM>), wherein the plurality of support braces (<NUM>) is in the form of ceramic posts that are arranged between and connected to the support capping structure (<NUM>) and the base plate (<NUM>), wherein each of the support braces (<NUM>) is angled to the support capping structure (<NUM>) and the base plate (<NUM>),
wherein the support capping structure (<NUM>) and the plurality of support braces (<NUM>) secure the wax pattern (<NUM>) to the base plate (<NUM>) in a fixed position and distribute the load of the wax pattern (<NUM>) while secured to the base plate (<NUM>).