Patent Publication Number: US-11642719-B1

Title: Hybrid casting process for structural castings

Description:
BACKGROUND 
     The present invention relates to casting metallic components and, more particularly, to a hybrid casting process for structural castings that uses a reusable metallic mold to produce the structural castings. 
     Many metallic components are produced using casting processes, a common casting process used is sand casting. Sand casting is a metal casting process characterized by using sand as the mold material. Sand casting uses mold boxes, known as flasks, filled with compacted sand to produce the mold cavities and gate system that is filled with molten metal to create the cast component. Sand casting is a relatively cheap method of casting components, but it also can result in lower quality and less predictable results of the final cast component. Components that require high accuracy, tight tolerances, and internal passages can be difficult to produce using sand casting processes. Other casting processes, such as investment casting, give a higher degree of precision for highly complex parts but are usually applied to smaller components than sand casting processes. Further, permanent mold and die casting processes are used for high-volume industries but typically make less complex parts than sand or investment casting processes. As such, there is a need for a casting process with less variation, better quality, and more predictable results for the final cast component. 
     SUMMARY 
     According to one aspect of the disclosure, a method for producing structural components is disclosed. The method includes aligning a core within a metallic mold by coupling the core to metallic locators attached to the metallic mold; filling the metallic mold with a molten metallic material; solidifying the metallic material within the metallic mold to produce a cast component; removing the cast component from the metallic mold; identifying a datum location, wherein the datum location is a central axis of an aperture extending through the cast component to the core; and removing material from one or more of an internal surface and external surface of the cast component based off the datum location. 
     According to another aspect of the disclosure, a casting assembly for producing a structural component is disclosed. The casting assembly includes a metallic mold and a core. The metallic mold includes walls, a heating device, and a cooling device. The walls define surfaces of the structural component. The heating device is coupled to the metallic mold and the heating device is configured to increase the temperature of surfaces of the metallic mold. The cooling device is coupled to the metallic mold and the cooling device is configured to decrease the temperature of surfaces of the metallic mold. The core is positioned within the walls of the metallic mold. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a flow chart illustrating steps of a method for producing structural components using a hybrid casting process. 
         FIG.  2 A  is a schematic cross-sectional diagram illustrating a first step of the hybrid casting process. 
         FIG.  2 B  is a schematic cross-sectional diagram illustrating a second step of the hybrid casting process. 
         FIG.  2 C  is a schematic cross-sectional diagram illustrating a third step of the hybrid casting process. 
         FIG.  2 D  is a schematic cross-sectional diagram illustrating a fourth step of the hybrid casting process. 
         FIG.  2 E  is a schematic cross-sectional diagram illustrating a structural component produced using the hybrid casting process. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure presents a hybrid casting process which uses the advantages of several casting processes to optimize the final cast component. The hybrid casting process uses conventionally manufactured or additively manufactured internal cores to produce complex internal passages as used in the sand-casting process. The hybrid casting process enables complex internal and external geometries as achieved in investment casting. Further, the hybrid casting process utilizes actively heated and/or cooled permanent molds, as used in die casting, to provide thermal control for optimum solidification of specific areas of the casting without relying on excessive gating systems/channels to feed metal into the part. The permanent molds can be filled with loose or chemically set sand to create a mold around the additive cores or a fluid ceramic media can be introduced to create a mold as in solid mold or investment casting. As such, the hybrid casting process results in less variation, better quality, and more predictable results for the final cast component. 
       FIG.  1    is a flow chart illustrating steps of method  100  for producing structural components using a hybrid casting process.  FIG.  2 A  is a schematic diagram showing a first step of method  100 .  FIG.  2 B  is a schematic diagram showing a second step of method  100 .  FIG.  2 C  is a schematic diagram showing a third step of method  100 .  FIG.  2 D  is a schematic diagram showing a fourth step of method  100 .  FIG.  2 E  is a schematic cross-sectional diagram illustrating a structural component produced using the hybrid casting process.  FIGS.  1 - 2 E  will be discussed together. 
     Method  100  includes steps  102 ,  104 ,  106 ,  108 ,  110 , and  112 . As shown best in  FIG.  2 A , step  102  includes aligning core  16  within metallic mold  12  by coupling core  16  to metallic locators  14  attached to metallic mold  12 . Step  104  includes filling metallic mold  12  with a molten metallic material. Step  106  includes solidifying the metallic material within metallic mold  12  to produce cast component  20 . As shown best in  FIG.  2 B , step  108  includes removing cast component  20  from metallic mold  12 . Step  110  includes identifying datum location  36 , wherein datum location  36  is a central axis of aperture  38  extending through cast component  20  to core  16 . As shown best in  FIGS.  2 C- 2 D , step  112  includes removing material from one or more of internal surface  40  and external surface  42  of cast component  20  based off datum location  36 . Each of steps  102 - 112  will be discussed in further detail below. 
     Referring again to  FIG.  2 A , casting assembly  10  for producing structural components is shown. Casting assembly  10  includes metallic mold  12 , metallic locators  14 , core  16 , and fluid channels  18 . Metallic mold  12  is a hollow container used to give shape to a molten or hot liquid material when it cools and hardens. Metallic mold  12  includes walls  22  defining surfaces of the to be cast component  20 . More specifically, walls  22  of metallic mold  12  are used to produce external and/or internal surfaces of cast component  20 . Each individual wall  22  of metallic mold  12  can be coupled together to form the overall shape of metallic mold  12  and the to be cast component  20 . In some examples, walls  22  of metallic mold  12  can be coupled together using fasteners that can be removed to separate and decouple walls  22  of metallic mold  12 . In other examples, walls  22  of metallic mold  12  can be coupled together through welds and/or formed from a single piece of material through machining operations. Metallic mold  12  is constructed from a metallic material, and in some examples, metallic mold  12  can be constructed from one or more of a cast iron, alloy steel, nickel alloy, copper alloy, and tungsten alloy. Further, metallic mold  12  is constructed from a material that has a higher temperature melting point than the metallic material poured into metallic mold  12 . 
     In the example shown, metallic mold  12  is a generally cube or box shaped mold, such that the resulting cast component  20  has a generally cube or box shaped external shape. In this example, the generally cube or box shaped cast component  20  has greater external tolerancing and flexibility but requires more machining operations to achieve the desired final external shape of the cast structural component. In another example, metallic mold  12  can be shaped to generally conform to the desired final external geometry of the cast structural component. In such an example, walls  22  of metallic mold  12  can have a complex shape that generally outlines the external geometry of the desired cast structural component. In this example, cast component  20  with a near net external geometry requires less machining operations to achieve the desired final external shape but also has less flexibility, as compared to a generally cube or box shaped mold, discussed further below. 
     Metallic locators  14  are positioned adjacent a top of metallic mold  12  and locators  14  extend inward toward a center of metallic mold  12 . Locators  14  are removably coupled to metallic mold  12  such that locators  14  can be coupled and decoupled from metallic mold  12  as required during the casting process. Locators  14  are configured to aid in properly positioning and aligning core  16  within metallic mold  12 , discussed further below. In some examples, locators  14  can be one or more of a pin, an aperture, a hook, an indent, a clevis, or a surface, among other options. In the example shown there are two locators  14 , each positioned on opposite sides of metallic mold  12  and extending inward toward a center of metallic mold  12 . In another embodiment, there can be more or less than two locators  14  coupled to metallic mold  12  and locators  14  can be positioned at any desired location on metallic mold  12 . In any embodiment, locators  14  are configured to accurately position core  16  within metallic mold  12  to meet internal and external tolerancing and other requirements for internal features of the final cast structural component. 
     Core  16  is a component of casting assembly  10  that is utilized to produce one or more internal passages and internal features within cast component  20 , producing internal features of the cast structural component. In some examples, core  16  can be utilized to produce fluid flow channels within a structural component that cannot be produced using traditional drilling, milling, or turning operations. Core  16  can be a ceramic core that is constructed from a ceramic material. Core  16  can be produced using a casting process or through an additive manufacturing process. As previously introduced, step  102  of method  100  includes aligning core  16  within metallic mold  12  by coupling core  16  to metallic locators  14  attached to metallic mold  12 . More specifically, a machine tool (not shown) is utilized to lower core  16  within walls  22  of metallic mold  12 . Core  16  is lowered into metallic mold  12  until core  16  interfaces with locators  14  coupled to metallic mold  12 . Core  16  is then coupled to locators  14 , securing core  16  to locators  14  and metallic mold  12 . Core  16  is now precisely positioned within metallic mold  12  to produce internal passages and internal features within cast component  20  and the final cast structural component. 
     Step  104  includes filling metallic mold  12  with a molten metallic material. More specifically, a metallic material is heated to a temperature above the metallic materials melting point to produce liquefied metal. The molten metallic material is poured into metallic mold  12  with the coupled core  16 , such that the molten metallic material fills metallic mold  12  and surrounds core  16  positioned within metallic mold  12 . In some examples, the molten metallic material can be one or more of an aluminum alloy and a magnesium alloy, among other options. Step  106  includes solidifying the metallic material within metallic mold  12  to produce cast component  20 . Solidifying the metallic material includes strategically allowing the metallic material to cool in temperature to solidify into a solid metallic cast component  20  with specific material properties. The specific material properties for cast component  20  will vary depending on the structural component being produced and the requirements for the mechanical and thermal properties of the structural component. The material properties of cast component  20  can be controlled through thermal management techniques that alter the solidification dynamics of cast component  20 . 
     As shown in  FIG.  2 A , casting assembly  10  can include fluid channels  18  that are utilized to control the solidification dynamics of cast component  20 . Fluid channels  18  can be positioned adjacent walls  22  of metallic mold  12  and fluid channels  18  are configured to provide a flow path for heating or cooling fluid to flow through. Fluid channels  18  can be one or more of a tube, hose, channel, conduit, or the like that includes a hollow central portion in which heating or cooling fluid can flow through. In some examples, fluid channels are positioned within walls  22  of metallic mold  12  such that fluid channels  18  are integral with walls  22  of metallic mold  12 . In other examples, fluid channels  18  can be affixed to exterior surfaces  24  and interior surfaces  26  of walls  22  of metallic mold  12 . Fluid channels  18  are fluidly coupled to a fluid source (not shown) positioned remote from casting assembly  10  and fluid channels  18  are configured to receive fluid from the fluid source. Fluid channels  18  can be separated into groups of channels such that some fluid channels  18  have a hot fluid flowing through them and other fluid channels  18  have a cold fluid flowing through them. Fluid channels  18  with hot fluid flowing through the fluid channels are configured to heat metallic mold  12 . Fluid channels  18  with cold fluid flowing through the fluid channels are configured to cool metallic mold  12 . In some examples, thinner portions of metallic mold  12  may require heating and thicker portions of metallic mold  12  may require cooling to achieve the desired solidification dynamics of cast component  20 . In other examples, heating or cooling specific sections of the mold may also be accomplished by use of electric resistance heaters, inductions coils, or the use of a variety of conductive metals or ceramic media with heat transfer attributes. 
     In the example shown in  FIG.  2 A , casting assembly  10  includes a plurality of sections/portions that have either heating or cooling fluid channels  18  positioned adjacent walls  22  of metallic mold  12 . More specifically, metallic mold  12  can include at least a first portion  28 , a second portion  30 , a third portion  32 , and a fourth portion  34 . In some examples, first portion  28  of metallic mold  12  can be positioned adjacent exterior surface  24  of metallic mold  12 ; second portion  30  of metallic mold  12  can be positioned adjacent interior surface  26  of metallic mold  12 ; third portion  32  of metallic mold  12  can be positioned adjacent exterior surface  24  of metallic mold  12 ; and fourth portion  34  of metallic mold  12  can be positioned adjacent interior surface  26  of metallic mold  12 . Further, in some examples, first portion  28  and second portion  30  of metallic mold  12  include hot fluid channels  18  and the hot fluid flowing through fluid channels  18  heats first portion  28  and second portion  30  of metallic mold  12 . In addition, in some examples, third portion  32  and fourth portion  34  of metallic mold  12  include cold fluid channels  18  and the cold fluid flowing through fluid channels  18  cools third portion  32  and fourth portion  34  of metallic mold  12 . In other examples, metallic mold  12  can include at least one heating device and at least one cooling device that are coupled to metallic mold  12  and configured to increase and decrease the temperature of surfaces of metallic mold  12 , respectively. In one example, the heating device can be a resistance heating element configured to increase in temperature when an electric current is supplied to the resistance heating element. 
     As such, metallic mold  12  can include hot/cold fluid channels  18  and/or heating/cooling devices that are configured to heat and cool different portions of metallic mold  12  to achieve the desired solidification dynamics of cast component  20 . In some examples, thinner portions of cast component  20  may require heating and thicker portions of cast component  20  may require cooling during the solidification process to achieve the desired cooling characteristics and mechanical and thermal properties for cast component  20 . Further, metallic mold  12  being constructed from a metallic material aids in the solidification process because metal is conductive and more effective at heating and cooling, as compared to traditional sand molds which are insulators. In addition, metallic mold  12  including heating and cooling devices is advantageous over traditional sand molding because it eliminates the need for at least some venting, gating, and waste flow channels that were previously required to achieve proper cooling characteristics for large structural cast components. 
     More specifically, metallic mold  12  including heating and cooling devices is advantageous over traditional sand molding because the casting process requires less metal to cast the part due to relying on active heating and cooling rather than gating systems to achieve a sound casting with desirable material properties. Removing the traditional gating systems results in less overall metallic material used during the casting process, less waste, and in turn lower costs for producing the structural component. In turn, this compensates for a larger external envelope for the part that will require machining to final dimensions. As such, controlling the solidification process of cast component  20  is key to achieving a final structural component with the desired mechanical and thermal properties, while also reducing waste and increasing profits. 
     As shown in  FIG.  2 B , step  108  includes removing cast component  20  from metallic mold  12 . After cast component  20  has completed the solidification process, cast component  20  is removed from metallic mold  12 . Cast component  20  can be removed from metallic mold  12  using various techniques. In one example, the fasteners coupling walls  22  of metallic mold  12  are removed and walls  22  are separated from cast component  20 . In another example, an aperture within metallic mold  12  allows access to a bottom side of cast component  20  and cast component  20  can be pushed from a bottom surface upward to separate cast component  20  from metallic mold  12 . Then a crane, hoist, or other similar device can be used to raise cast component  20  from metallic mold  12 . Once cast component  20  is removed from metallic mold  12 , core  16  is removed from cast component  20  and the hollow channels and/or features remain within the interior of cast component  20 . In one example, core  16  can be removed from cast component  20  by breaking core  16  into small pieces and then the small pieces are shaken out from the interior of cast component  20 . In another example, a release agent/liquid can be applied to core  16  and a heating process can be used to melt/dissolve core  16  into smaller particles that can then be poured or shaken out from the interior of cast component  20 . 
     Step  110  includes identifying datum location  36 , wherein datum location  36  can be a central axis of aperture  38  extending through cast component  20  to core  16 . Datum location  36  is a reference point on or within cast component  20  in which all final edges and surfaces of the structural component are measured from. More specifically, datum location  36  is a fixed starting point in which all machining operations are measured from to produce the final external dimensions and geometry of the structural component. In one examples, datum location  36  can be a central axis of aperture  38  extending through cast component  20 . In other examples, datum location can be a surface, edge, or other feature of cast component  20  in which all final edges and surfaces of the structural component are measured from. 
     As shown best in  FIGS.  2 C- 2 D , step  112  includes removing material from one or more of internal surface  40  and external surface  42  of cast component  20  based off datum location  36 . More specifically, a CNC machine is used to machine and remove material from internal surfaces  40  and external surfaces  42  of cast component  20  to produce the final dimensions and geometry of the structural component. Removing material from internal surfaces  40  and external surfaces  42  of cast component  20  can be one or more of a turning operation, drilling operation, and milling operation, among other options. The CNC machine uses datum location  36  as the origin (0,0 location) in which all geometric dimensions and tolerances are measured from to ensure the final machined cast component  20  meets the dimensional requirements for the desired structural component.  FIG.  2 E  is a schematic cross-sectional diagram illustrating an example structural component produced using the hybrid casting process. 
     The hybrid casting process described in method  100  produces cast components that have less variation, better quality, and more predictable results, resulting in high customer satisfaction and lower overall costs. The hybrid casting process provides a method to control internal and external casting mold movement to produce a higher percentage of conforming structural components. The hybrid casting process provides a method to consistently align core  16  within metallic mold  12 , reducing variation from part to part. Further, providing metallic mold  12  with excess material on external surfaces  42  of cast component  20  allows for a simpler external envelope which can be more readily cast and machined to final desired dimensions during the final machining processes to achieve the desired dimensions and tolerances for all internal and external features of the cast structural component. Metallic mold  12  is a reusable mold that can be used to produce many structural components with the same mold, thus metallic mold  12  reduces variation from part to part as compared to traditional sand molds. Method  100  and the hybrid casting process produce internal features with less variation by allowing more internal tolerance which is balanced by external machining to achieve to final external geometry. Further, method  100  and casting assembly  10  allow for more effective thermal management during the cooling of cast component  20  which produces better castings, as compared to traditional sand castings. The reusable metallic mold  12  gives a more consistent product than expendable sand molds with less process variation, leading to better quality, less material waste, lower cost, more predictable results, and high customer satisfaction. 
     Discussion of Possible Embodiments 
     The following are non-exclusive descriptions of possible embodiments of the present invention. 
     A method for producing structural components, the method comprising: aligning a core within a metallic mold by coupling the core to metallic locators attached to the metallic mold; filling the metallic mold with a molten metallic material; solidifying the metallic material within the metallic mold to produce a cast component; removing the cast component from the metallic mold; identifying a datum location, wherein the datum location is a central axis of an aperture extending through the cast component to the core; and removing material from one or more of an internal surface and external surface of the cast component based off the datum location. 
     The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components: 
     Heating a first portion of the metallic mold during the solidifying of the metallic material within the metallic mold; heating a second portion of the metallic mold during the solidifying of the metallic material within the metallic mold; cooling a third portion of the metallic mold during the solidifying of the metallic material within the metallic mold; and cooling a fourth portion of the metallic mold during the solidifying of the metallic material within the metallic mold. 
     The first portion of the metallic mold is on an exterior surface of the metallic mold; the second portion of the metallic mold is on an interior surface of the metallic mold; the third portion of the metallic mold is on an exterior surface of the metallic mold; and the fourth portion of the metallic mold is on an interior surface of the metallic mold. 
     The metallic mold comprises fluid channels positioned within walls of the metallic mold; hot fluid flows through the fluid channels to heat the metallic mold; and cold fluid flows through the fluid channels to cool the metallic mold. 
     Fluid channels are affixed to walls of the metallic mold; hot fluid flows through the fluid channels to heat the metallic mold; and cold fluid flows through the fluid channels to cool the metallic mold. 
     A resistance heating element is coupled to walls of the metallic mold, and wherein an electric current is supplied to the resistance heating element to heat the metallic mold. 
     The metallic mold is shaped to conform to external surfaces of the structural component. 
     The metallic mold is a generally cube or box shaped mold. 
     The core is a ceramic core constructed from a ceramic material. 
     The metallic mold is constructed from one or more of a cast iron, alloy steel, nickel alloy, copper alloy, and tungsten alloy. 
     The metallic material is one or more of an aluminum alloy and a magnesium alloy. 
     The metallic mold has a higher temperature melting point than the metallic material poured into the metallic mold. 
     The core is utilized to produce one or more of internal passages and internal features within the cast component. 
     The core is removed from the cast component by breaking the core into pieces and shaking the core from an interior of the cast component. 
     The datum location is a reference point in which all edges and surfaces of the structural component are measured from. 
     Removing material from the internal and external surfaces of the cast component can be one or more of a turning operation, drilling operation, and milling operation. 
     The following are further non-exclusive descriptions of possible embodiments of the present invention. 
     A casting assembly for producing a structural component, the casting assembly comprising: a metallic mold comprising: walls defining surfaces of the structural component; a heating device coupled to the metallic mold, wherein the heating device is configured to increase the temperature of surfaces of the metallic mold; and a cooling device coupled to the metallic mold, wherein the cooling device is configured to decrease the temperature of surfaces of the metallic mold; and a core positioned within the walls of the metallic mold. 
     The casting assembly of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components: 
     The heating device and cooling device are fluid channels positioned within the walls the metallic mold, and wherein hot fluid flows through the fluid channels to heat the metallic mold and cold fluid flows through the fluid channels to cool the metallic mold. 
     The metallic mold is constructed from one or more of a steel, titanium, copper, and tungsten. 
     The core is a ceramic core constructed from a ceramic material; the core is utilized to produce one or more internal passages and internal features within the structural component; and the core is removed from the structural component by breaking the core into pieces and shaking the core from an interior of the structural component. 
     While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.