Patent Publication Number: US-7913743-B2

Title: Method of forming a pattern

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a new and improved method for forming a pattern which includes a core which is at least partially covered by wax. 
     Articles, such as an airfoil, have been formed by a lost wax investment casting process. The process may include forming a pattern having the configuration of a space or cavity to be formed in a mold in which an article is to be cast. A core portion of the pattern has a configuration corresponding to the configuration of a space to be formed in the article. 
     To form the pattern, the core is positioned in a die cavity. Wax is injected into the die cavity around the core. The resulting pattern may subsequently be covered with a ceramic mold material. 
     Once the pattern has been covered with a ceramic mold material, the wax portion of the pattern is melted. The wax is removed from the mold to leave a cavity into which metal is cast. The core is at least partially enclosed by this cast metal. The core is subsequently removed to form space in the cast metal article. The space formed by the core may be a complex arrangement of passages. 
     The concept of supporting a core in a die cavity using fixed and/or spring loaded pins to support the core is disclosed in U.S. Pat. No. 4,283,835. A system which allows for design changes, such as a shift in core location, is disclosed in U.S. Pat. No. 7,296,615. 
     SUMMARY OF THE INVENTION 
     The present invention provides a new and improved method of forming a pattern which includes a core which is at least partially covered by wax. The method includes providing an actual core having dimensions which differ from dimensions of an ideal core, that is, a core which exactly conforms to a specific design for the core. A best fit spatial relationship of the actual core to a spatial envelope for the ideal core may be determined. This results in space formed by the actual core in a cast metal article having a best fit relationship with the cast metal article. If desired, a best fit spatial relationship of the actual core to a pattern die cavity may be determined, rather than a best fit with an ideal core. 
     A die having a plurality of core locating surfaces is provided. The core locating surfaces in the die are movable between a plurality of positions including ideal core locating positions, in which the ideal core would be positioned in a desired spatial relationship relative to the die. The core locating surfaces in the die are movable to actual core locating positions which are offset from the ideal core locating positions. When the core locating surfaces are in the actual core locating positions, an actual core which is disposed in engagement with the core locating surfaces is positioned in a best fit spatial relationship with the spatial envelope for the ideal core. This results in the actual core being positioned in a best fit spatial relationship with a die cavity in which the pattern is formed. 
     The actual core is positioned in engagement with the core locating surfaces while the core locating surfaces are in the actual core locating positions. A flow of wax is conducted into the die while the actual core is in engagement with the core locating surfaces and while the core locating surfaces are in the actual core locating positions. 
     A plurality of motors may be utilized to move the core locating surfaces relative to the die. In one embodiment of the invention, the core locating surfaces which are moved by the motors are disposed in association with only one section, for example, the lower section, of the die. However, motors may be associated with locating surfaces associated with a second section, in the example, the upper section, of the die if desired. 
     The present invention has a plurality of different features. These features may be utilized together as disclosed herein or may be utilized separately and/or in combination with features from the prior art. For example, core locating surfaces may be moved by manually actuating one or more drive trains. As another example, motors may be utilized to move core locating surfaces to positions other than positions in which an actual core is positioned in a best fit spatial relationship with a spatial envelope for an ideal core. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features of the present invention will become more apparent upon a consideration of the following description taken in connection with the accompanying drawings wherein: 
         FIG. 1  is a simplified schematic sectional view illustrating a pattern disposed in a die, a core of the pattern is at least partially covered by wax; 
         FIG. 2  is a schematic illustration of a coordinate-measuring machine which may be utilized to measure an actual core; 
         FIG. 3  is a schematic illustration depicting an actual core and a spatial envelope of an ideal core; 
         FIG. 4  is a schematic illustration depicting an apparatus utilized to position an actual core in the die with the actual core in a best fit spatial relationship with a spatial envelope for an ideal core; 
         FIG. 5  is a schematic pictorial illustration of a lower section of a die, constructed in accordance with  FIG. 4 , which is utilized in the formation of a pattern; 
         FIG. 6  is a schematic pictorial illustration of a plurality of gauge assemblies which may be utilized to determine the positions of locating surfaces in the die section of  FIG. 5 ; 
         FIG. 7  is a schematic illustration depicting the manner in which one of the gauge assemblies of  FIG. 6  is utilized in association with the die section of  FIG. 5 ; and 
         FIG. 8  is a schematic illustration, depicting the manner in which motors may be utilized to position locating surfaces in lower and upper sections of a die and the manner in which the coordinate-measuring machine of  FIG. 2  may be connected with control apparatus for the motors. 
     
    
    
     DESCRIPTION OF SPECIFIC PREFERRED EMBODIMENTS OF THE INVENTION 
     Background and General Description 
     A die  20  ( FIG. 1 ) is utilized in the forming of a pattern  22 . The pattern  22  includes a known core  24  which is at least partially covered by known natural or artificial wax  26 . The pattern  22  is held, in a die cavity  28 , between a lower section  30  and an upper section  32  of the die  20 . 
     The pattern  22  is removed from the die  20 . Thereafter, the pattern  22  is at least partially enclosed with a suitable mold material. For example, the pattern  22  may be enclosed with a slurry of a ceramic material which solidifies over the outside of the pattern to form a mold. 
     The wax  26  is then removed from the mold to form a cavity in the mold. The core  24  is disposed in the cavity in the mold. The cavity in the mold is filled with molten metal which solidifies around the core to form a cast article. The core  24  is subsequently removed from the cast metal article to form passages or space in the cast article. 
     In order to form the mold which at least partially encloses the pattern  22 , the pattern may be covered with a known liquid ceramic mold material. The pattern  22  may be covered with a liquid ceramic mold material by repetitively dipping the pattern in a slurry of liquid ceramic mold material. Although many different types of slurries of ceramic mold material may be utilized, one illustrative slurry contains fused silica, zircon and other refractory materials in combination with binders. Chemical binders, such as ethyl silicate, sodium silicate and colloidal silica can be utilized. In addition, the slurry may contain suitable film formers such as alginates to control viscosity and wetting agents to control flow characteristics and pattern wettability. 
     The use of a pattern, similar to the pattern  22 , having a core, similar to the core of  24 , enclosed by wax, similar to the wax  26 , is well known. The pattern  22  may be enclosed by any one of many different known types of mold material and the foregoing discussion of a ceramic mold material should be considered as being illustrative of many different mold materials which may be utilized in association with the pattern  22 . 
     The pattern  22  is configured to form an airfoil, such as a blade or vane for a turbine engine. However, the pattern  22  may be configured to form many different articles other than a blade or vane of a turbine engine. For example, the pattern  22  may be configured to form a blade outer air seal for use in a turbine engine. Alternatively, the pattern  22  may be configured to form articles which are used in environments other than in a turbine engine. 
     The core  24  may be formed of any desired material. The illustrated core is formed of a known ceramic material and may have a configuration and composition similar to the configuration and composition of the core disclosed in U.S. Pat. No. 5,580,837. However, it should be understood that the core  24  may be formed of many different materials and may have many different compositions. However, when the core  24  is to be utilized is association with a ceramic mold during the casting of turbine engine components, it is believed that it may be advantageous to have the core  24  formed of a ceramic material which is compatible with a ceramic material forming the mold. 
     The wax  26  at least partially encloses the core may be either a natural or artificial wax. After the pattern  22  has been enclosed by a ceramic mold material, the wax  26  is removed from the resulting molds to leave a space within the mold. This space will have a configuration corresponding to the desired configuration of a metal article, such as a cast metal blade or vane used in a turbine engine. The core  24  is left in the mold. 
     After molten metal has been solidified in the space formed in the mold by removal of the wax  26 , the resulting the metal article is removed from the mold. The core  24  is then removed from the metal article. Removal of the core  24  results in the formation of space, such as airflow passages, in the resulting metal article. 
     Although the core  24  may be formed of many different materials and in many different ways, the illustrated core is formed by mixing a ceramic material with a binder. The resulting mixture is injection molded to form a compact or green core having a configuration corresponding to the desired configuration of the core. This green core or compact is then sintered to form the ceramic core  24 . 
     During formation of the illustrated core  24 , a ceramic material and binder or carrier are mixed. Although many different binders may be utilized, the binder may include a water soluble and a water insoluble component. The water soluble and water insoluble components of the binder may be completely miscible in each other when they are in a liquid state. This facilitates mixing of the components of the binder. 
     The water soluble component of the binder may include at least one hydrophilic functional group. The water insoluble component of the binder may be a polymer having hydroxyl groups copolymerized with non-polar diluents to such an extent as to be insoluble with a water-based media. The water soluble component and water insoluble component of the binder may initially be powders which are heated to change them from the solid state to their liquid states. 
     The liquid heterogeneous mixture of water soluble and water insoluble components of the binder are mixed with a ceramic powder. The powder may be coated with a dispersant, lubricant and/or surfactant, to form a substantially uniform feedstock. The mixing of the binder with the ceramic powder may occur at elevated temperatures in a sigma blade mixture. During mixing, the binding has a relatively low viscosity. The substantially uniform mixture of binder and powder forms a feedstock. 
     The feedstock is injection molded in a die to form a compact or green core. The feedstock is molded to a configuration which is a function of the configuration of an ideal core, that is, a core which conforms exactly to a design for the core. 
     It may be desired to at least partially remove the binder from the compact or green core before sintering the compact or green core. Thus, there is a partial debinding of the compact by removing at least a portion of the water soluble component of the binder. This may be accomplished by exposing the compact to a water-based solvent which removes at least a portion of the water soluble component of the binder. 
     When sufficient debinding of the compact or green core has been accomplished to remove a desired amount of the water soluble component of the binder, the compact or green core may be withdrawn from exposure of the water based solvent. The compact may then be slowly dried in a moisture rich atmosphere. 
     After the soluble component of the binder has been at least partially removed from the compact or green core and the compact has been slowly dried, the water insoluble component of the binder and any remaining portion of the water soluble component may be removed. This may be accomplished by heating the compact or green core to a temperature above 1,000° F. in a suitable furnace. 
     After removal of the water soluble and water insoluble components to the binder, the powder particles of the ceramic material are mechanically held together. The compact or green core is then sintered in a suitable furnace to bond the powdered particles of the ceramic material together. The compact may, typically, be sintered at a temperature of approximately 1,500° to 1,650° C. 
     The specific composition of the core  24  and the manner in which the core is formed is known and do not, in and of themselves, form a part of the present invention. The core  24  may be formed in any desired way utilizing any desired materials. The foregoing specific manner of forming the core and components utilized in the core have been set forth herein merely for background. This background has been set forth for purposes of clarity of description and not for purposes of limiting the invention. 
     Although the present invention may be utilized in association with the forming of many different types of articles, the illustrated pattern  22  is for use in forming an airfoil which is utilized in a turbine engine. The core  24  has a concave side surface  34  ( FIG. 1 ) and a convex side surface  36 . During the casting of an airfoil, the concave side surface  34  of the core  24  forms a concave side of a passage or space in the airfoil. The convex side  36  of the core  24  forms a convex side of the passage or space in the airfoil. 
     Use of an Imperfect Core 
     When the core  24  has been formed, the core will have a configuration which differs, to at least some small extent, from the configuration of an ideal or perfect core. The actual core  24  will have dimensions and a configuration which are not exactly the same as the dimensions and configuration of a design core, that is, the ideal core. Although the dimensions of the actual core  24  will differ from the dimensions of an ideal (perfect) core, an article cast with the actual core should have internal space or passages which match, as closely as possible, the internal space or passages formed by an ideal core. Any deviation in the space or passages which are formed in a cast article by an actual core  24  from the space or passages formed by an ideal core will effect the strength and/or operating characteristics of the article cast with the actual core  24 . 
     During production of a substantial number of actual cores  24 , each of the cores may have dimensions and/or a configuration which are within a manufacturing tolerance range from the dimensions and/or configuration of an ideal core. However, due to the many variables in forming an actual core  24 , including debinding and sintering, the dimensions and/or configuration of the actual core will deviate by a small amount from the dimensions and/or configuration of an ideal or perfect core. Of course, during manufacture of an actual core  24 , it is endeavored to form the core with a configuration and dimensions which are as close as possible to the configuration and dimensions of an ideal (perfect) core. 
     When an actual core  24  has been formed, it is measured to determine the actual configuration and dimensions of the core. To measure the actual core  24 , a known coordinate-measuring machine  40  ( FIG. 2 ) may be utilized. The coordinate-measuring machine  40  includes a probe  42  disposed on a probe head  44 . The probe head  44  touches the core  24  at different spots where the core  24  is to be measured. 
     The coordinate-measuring machine  40  uses the x,y and z coordinates of selected points on the core  24  to determine the dimensions and configuration of the core  24 . If desired, the probe  42  may drag along the surface of the core  24  and take measurements at points at specified intervals. It is contemplated that a laser may be utilized to scan the core  24  rather than a mechanical probe. 
     A carriage  46  is disposed on a support frame of the coordinate-measuring machine  40 . The probe head  44  is connected to the carriage  46 . Outputs from the probe head  44  and carriage  46  are transmitted to registers, that is, data storage units in a computer, to store data corresponding to the measurements of the actual core  24 . 
     In accordance with one of the features of the present invention, the computer determines the best fit of the measured data points on the actual core  24  to corresponding data points on an ideal core. The computer stores the dimensions and configuration of the ideal core. Measured dimensions and configuration of the actual core  24 , as measured with the coordinate measuring machine  40 , are compared to the desired dimensions and configuration of the ideal core by the computer. The computer determines a best fit relationship between the actual measured data for the actual core  24  and the stored data for the ideal or perfect core. 
     The computer contains software which determines when a best fit spatial relationship is obtained between an actual core  24  and an ideal (perfect) core. The software is commercially available from many different sources. In the illustrated embodiment of the invention, the software was Camio Studio 4.6 software which was obtained from Metris USA having a place of business at 12701 Grand River, Brighton, Mich. 48116 and at 1577 Star Batt Drive, Rochester Hills, Mich. 48309. Of course, it is contemplated that the software may and will be obtained from other sources. 
     The manner in which the computer determines the best fit relationship between the measured dimensions of the actual core  24  and the corresponding dimensions of the ideal core is illustrated schematically in  FIG. 3 . The actual core  24  has a spatial envelope with a configuration and dimensions which have been indicated schematically at  50  in  FIG. 3 . The dimensions and configuration of a spatial envelope of an ideal (perfect) core are indicated schematically at  52  in  FIG. 3 . 
     The actual core dimensions measured by the coordinate measuring machine  40  enable a spatial envelope  50  for the actual core  24  to be determined. The spatial envelope  52  of the ideal core is determined from the design dimensions of the ideal core. The spatial envelope  50  of the actual core  24  can differ from the ideal spatial envelope  52  within a manufacturing tolerance range. 
     The acceptance of the actual core  24  with dimensions and a configuration which differs, within a tolerance range, from the dimensions and configuration of the ideal core is necessary in order to accommodate the inevitable small deviations which occur during manufacturing of the actual cores. These small deviations may be the result of debinding and/or sintering of the actual core  24 . Of course, variations in the dimensions and/or configuration of the actual core  24  from the dimensions and configuration of the ideal core may be the result of factors other than debinding and/or sintering of the actual core. 
     When the actual core  24  is positioned in the die cavity  28  in a best fit spatial relationship with the spatial envelope  52  for an ideal core correctly located in the die, the spatial envelope  50  of the actual core is congruent, to the maximum extent possible, with the spatial envelope for the ideal core. By having the actual core  24  positioned in the die  20  in a best fit spatial relationship with the spatial envelope  52  for the ideal core, deviations in the dimensions and/or configuration of the wax  26  which is injection molded around the actual core from a design dimension and/or configuration for the wax are minimized. This results in minimal deviations in a wall of an article cast using the pattern  22 . 
     When the actual core  24  is positioned in the die cavity  28  in a best fit relationship with an ideal core, the actual core is also in a best fit spatial relationship with both an ideal core and the die cavity  28 . The wax  26  is subsequently molded in the die cavity  26  with dimensions and a configuration which are as close as possible to the ideal (design) dimensions and configuration for the wax. This results in a metal article, which is subsequently cast using the pattern  22 , having dimensions and a configuration which are as close as possible to the ideal (design) dimensions and configuration for the cast metal article. When the actual core  24  is removed from the cast metal article, space is formed in the cast metal article. This space will have dimensions and a configuration which are as close as possible to the ideal (design) dimensions and configuration for the space. 
     When the core  24  is to be positioned in the die  20  in a best fit spatial relationship with the spatial envelope  52  for the ideal core when the ideal core is in a desired spatial relationship to the die, the positions of at least some core positioning members  62  ( FIG. 4 ) of a plurality of core positioning members are adjusted. The core positioning members  62  are moved, relative to the die  20 , to positions in which the actual core  24  can be supported in a position in which the spatial envelope  50  of the actual core is in a best fit spatial relationship with the spatial envelope  52  for the ideal core when the ideal core is in a desired (design) position relative to the die. When the actual core  24  is in a best fit spatial relationship with the spatial envelope  52  for the ideal core, the actual core  24  will also be in a best fit spatial relationship with the die cavity  28 . 
     In accordance with one of the features of the present invention, a plurality of motors  74  ( FIG. 4 ) are operated to move the core positioning members  62  to locating positions in which the core positioning members will be disposed when the core  24  is in the best fit spatial relationship to a spatial envelope  52  of the ideal core. Thus, if it is assumed that the core positioning members  62  are initially moved to the positions in which they would locate an ideal core relative to the lower and upper die sections  30  and  32 , the motors  74  are operated to move at least some of the core positioning members  62  to core locating positions which are offset from the ideal core locating positions. 
     The motors  74  are operated to move core positioning members  62  to positions in which core locating surfaces  60  are offset from the positions in which they would be disposed if the core  24  had the dimensions and configurations of an ideal core. This results in the actual core  24  being located in a best fit relationship with a spatial envelope  52  of the ideal core when the ideal core is disposed in the die  20 . This also results in the actual core  24  being located in a best fit relationship with the die cavity  28 . 
     The amounts by which the core locating surfaces  60  on the core positioning members  62  are offset from positions they would be in if the core  24  was an ideal core, is entered into a controller (computer)  80 . The controller  80  is connected with the motors  74 . The controller  80  effects operation of the motors  74  to move the core locating surfaces  60  to positions which are offset from positions the core locating surfaces would be in if the core was an ideal core. The controller  80  effects operation of the motors  74  to move the core locating surfaces  60  to positions in which the core locating surfaces can position the actual core  24  in a best fit relationship with both the spatial envelope  52  for the ideal core and the die cavity  28 . 
     If desired, the coordinate-measuring machine  40  may be connected directly to the controller. Data, corresponding to the measurements made by the coordinate-measuring machine  40  may be stored in registers (data storage units)  82  in the controller  80 . This would enable the controller  80  to determine the amounts by which the core positioning surfaces  60  are to be offset from the positions they would be in if the core  24  was an ideal core. 
     The motors  74  are connected with the core positioning members  62  by suitable drive trains  84  ( FIG. 4 ). The drive trains  84  may have any desired construction. The illustrated drive trains  84  have internally threaded members which are disposed in engagement with externally threaded members. The internally threaded members may be connected with the motors  74  through suitable reduction gearing. The externally threaded members are connected with the core positioning members  62 . Rather than using internal and external thread convolutions to effect movement of the core positioning members  62 , the drive trains  84  may have cam surfaces to move core positioning members relative to the lower section  30  of the die  20 . 
     The motors  74  are reversible. Therefore, the controller (computer)  80  can operate the motors  74  in one direction to move the core positioning members  62  upwardly (as viewed in  FIG. 4 ). Alternatively, the controller  80  can operate the motors  74  in the opposite direction to move the core positioning members  62  downwardly. 
     The core positioning members  62  are moved relative to the lower section  30  of the die  20  with the die in an open condition and with the core  24  spaced from the die. When the die  20  is in an open condition, the upper section  32  of the die is spaced from the lower section  30  of the die so that a die cavity surface  66  ( FIG. 4 ) in the lower die section is exposed. In addition, the locating surfaces  60  on the core positioning members  62  are exposed. 
     Once the controller  80  has operated the motors  74  to move the core locating surfaces  60  to desired positions relative to the lower section  30  of the die  20 , the actual core  24  is positioned on the core locating surfaces  60  in the manner illustrated schematically in  FIG. 4 . At this time, the upper section  32  of the die  20  is spaced from the lower section  30  of the die. If desired, the core  24  may be positioned on the core locating surfaces  60  during operation of the motors  74  to move the core locating surfaces. 
     The die  20  is then operated to the closed condition ( FIG. 4 ) by moving the upper die section  32  into engagement with the lower die section  30 . The core  24  is positioned in a closed die cavity  28  in a best fit spatial relationship with the die cavity surfaces  66  and  68  by the core positioning members  62 . The results in the actual core  24  forming passages in a cast metal article with the passages in a best fit relationship relative to the cast metal article. 
     Hot wax is injected under pressure, into the die cavity  28  with the die  20  in the closed condition illustrated in  FIG. 4 . At this time, the core  24  is positioned relative to the lower and upper die sections  30  and  32  by the core positioning members  62 . The actual core  24  is positioned in a best fit spatial relationship with the spatial envelope for an ideal (perfect) core if the ideal core was positioned in a desired spatial relationship relative to the die. The actual core  24  is also positioned in a best fit spatial relationship relative to the die cavity  28 . 
     The heated wax  26  ( FIG. 1 ), which is injected into the closed die  20 , flows around the core  24  and fills the die cavity  82  ( FIG. 4 ) to form the pattern  22 . The wax  26  may be either a natural wax or a synthetic wax. The core  24  is supported in the die  20  in such a manner as to prevent movement of the core relative to the die as the wax  26  is injected into the die cavity  28 . 
     When the wax  26  is injected into the closed die  20  and flows around the core  24 , the wax is hot to decrease its viscosity and increase its flowability. Once the wax  26  has cooled, the die  20  is operated to its open condition. The pattern  22  is then removed from the die. 
     The spatial relationship of the actual core  24  to the wax  26  in the pattern  22  is optimized by having the core in a best fit spatial relationship with the spatial envelope  52  of the ideal core when the actual core  24  is disposed in the die  20 . This results in surfaces on the actual core  24  being in a best fit spatial relationship relative to the surfaces  66  and  68  of the die cavity  82 . 
     After the pattern  22  has been covered with a slurry of ceramic mold material and the ceramic mold material dried, the wax  26  is removed from the resulting mold. At this time, the actual core  24  is disposed in a best fit spatial relationship relative to internal surfaces of the mold. By optimizing the position of the actual core  24  relative to internal surfaces of the mold, a metal article which is cast in the mold will have passages, that is internal spaces, which are in positions which are as close as possible to design positions relative to the external surfaces of the cast metal article. If the cast metal article is a blade or vane for use in a turbine engine, the cast metal article may be formed of a nickel chrome super alloy. 
     In the embodiment of the invention illustrated in  FIGS. 1-4 , there are five core locating surfaces  60  disposed on five core positioning members  62 . It is contemplated that a greater or lesser number of core locating surfaces  60  and core locating members  62  may be utilized to position the actual core  24  relative to the die  20 . For example, three locating surfaces  60  may be used on three core positioning members  62  if desired. Alternatively, seven core locating surfaces  60  may be provided on seven core positioning members  62  if desired. The number of motors  74  provided would correspond to the number of core positioning members to be utilized to position a core  24  relative to the die  20 . If desired, two or more core locating surfaces  60  may be provided on a single core positioning member  62 . 
     It is contemplated that motors, similar to the motors  74 , may be utilized to adjust the positions of core locating surfaces  60  relative to a die  20  without determining a best fit spatial relationship of an actual core  24  to a spatial envelope  52  for an ideal core and/or to the die cavity  28 . If this is done, the motors  74  may be operated to locate the core locating surfaces  60  in positions which they would have if an ideal core was being positioned in the die cavity  28 . Of course, this would not optimize the position of the actual core  24  relative to the die cavity surfaces  66  and  68 . 
     The concept of determining a best fit spatial relationship of an actual core  24  to a spatial envelope  52  for an ideal core may be utilized without providing motors, corresponding to the motors  74 , to move the core locating surfaces  60  relative to a die  20 . If this is done, the drive trains  84  for the core positioning members  62  may be manually actuated to move the core positioning members to locations in which the core locating surfaces would position an actual core  24  in a best fit spatial relationship with the die cavity  82 . 
     In the foregoing description, the actual core  24  has been positioned in the die cavity  28  by determining a best fit spatial relationship of the actual core to a spatial envelope  52  for an ideal core. At least some of the core locating surfaces  60  are moved to actual core locating positions which are offset from ideal core locating positions. The actual core  24  is positioned in engagement with the core locating surfaces  60 . Wax is conducted into the closed die  20  while the actual core  24  is in engagement with the core locating surfaces  60  and while the core locating surfaces are in the actual core locating positions. 
     By determining a best fit spatial relationship of the actual core  24  to the spatial envelope  52  for the ideal core and adjusting the core locating surfaces  70 , a best fit spatial relationship of the actual core relative to the die cavity  28  is obtained. However, this may be done by determining a best fit spatial relationship of the actual core  24  to the die cavity  28 . The core locating surfaces  60  would be adjusted to support the actual core  24  in the best fit spatial relationship relative to the die cavity. 
     When this is to be done, the computer determines the best fit spatial relationship of the data points measured by the coordinate-measuring machine  40  to the spatial envelope of the die cavity  28 . Thus, the computer stores the dimensions and configuration of the die cavity  28 . The dimensions and configuration of the die cavity  28  will correspond to the (design) dimensions and configuration of the exterior of a metal article to be cast using the pattern  22 . 
     The actual core dimensions measured by the coordinate-measuring machine  40  enable a spatial envelope  50  for the actual core  24  to be determined. The spatial envelope  52  of the actual core is compared to the spatial envelope of the die cavity  28  by the computer. A best fit of the spatial envelope  50  of the actual core  24  to the spatial envelope of the die cavity  28  is determined by this comparison. The positions of the core locating surfaces  60 , when they support the actual core  24  in a best fit position relative to the die cavity  28 , are determined. The motors  74  are operated to move the core locating surfaces  60  to the positions in which the core locating surfaces can support the actual core  24  in a best fit position relative to the die cavity  28 . 
     Once the core locating surfaces  60  have been moved to positions in which the core locating surfaces can support the actual core  24  in a best fit spatial relationship with the die cavity  28 , the core is positioned in the die cavity on the core locating surfaces. The die  20  is then closed and hot wax is injected into the die cavity. The hot wax solidifies around the core  24  to form the pattern  22 . 
     Embodiments of FIGS.  5 - 7   
     The lower section  30  of the die  20  has been illustrated schematically in  FIGS. 1 and 4 . One specific embodiment of the lower section  30  of the die  20  is illustrated in  FIGS. 5-7 . Since the embodiment of the invention illustrated in  FIG. 5  is generally similar to the embodiments illustrated in  FIGS. 1-4 , numerals which are similar to the numerals utilized in association with the embodiment of the invention illustrated in  FIGS. 1-4  will be utilized to identify components of the embodiment of the invention illustrated in  FIGS. 5-7 . The suffix letter “a” will be associated with the numerals of  FIGS. 5-7  to avoid confusion. 
     A lower die section  30   a  includes a die cavity surface  66   a . Core positioning members  62   a  have core locating surfaces  60   a  which engage an actual core in the manner illustrated schematically in  FIG. 4 . In addition, the core support members or pins  90  are provided in the lower die section  30   a . The core support members  90  do not engage a core when it is initially positioned in the lower die section  30   a . The core support members  90  engage a core  24  ( FIGS. 1 ,  3 , and  4 ), in the event of slight deflection of the core. The core support members  90  limit the range of deflection of the core  24 . 
     The core positioning members  62   a  initially support the actual core in a die cavity in the manner illustrated schematically in  FIG. 4 . The core support members  90  engage and are effective to partially support the actual core only if there is deflection of one or more portions of the actual core during the injection of wax into the die  20   a . Manually actuated controls  94  are provided to effect movement of the core support members  90  to desired positions relative to a core which is supported on the core locating surfaces  60   a  of the core positioning members  62   a.    
     When an upper section of the die assembly  20   a  is moved to a closed position cooperating with the lower die section  30   a , a passage  100  is formed to conduct wax into the closed die cavity. The passage  100  has an inlet  102  through which wax is injected into the passage. 
     Although motors, corresponding to the motors  74  of  FIG. 4 , are provided to move the core positioning members  62   a  on the lower die section  30   a  of  FIG. 5 , it is contemplated that it may, under certain circumstances, be desirable to manually adjust the positions of the core positioning members  62   a  and locating surfaces  60   a  relative to the lower die section. If this is to be done, a plurality  110  ( FIG. 6 ) of gauge assemblies may be utilized. The plurality  110  of gauge assemblies includes a root end portion gauge assembly  114  and a tip end portion gauge assembly  116 . 
     The root end portion gauge assembly  114  includes a base or support member  120  on which registers  122 ,  124  and  126  ( FIG. 6 ) are mounted. The registers  122 - 126  are connected with actuators (not shown) which engage the core locating surfaces  60   a  ( FIG. 5 ) on the core positioning members  62   a . The tip end portion gauge assembly  116  ( FIG. 6 ) includes a base or support member  130  on which registers  134  and  136  are disposed. 
     Actuators (not shown) are connected with the registers,  122 ,  124 , and  126  of the root end portion gauge assembly  114  and engage core locating surfaces  60   a  on core positioning members  62   a  disposed adjacent to the root (right as viewed in  FIG. 5 ) end portion of the lower die section  30   a . Similarly, actuators (not shown) are utilized in association with the registers  134  and  136  in the tip end portion gauge assembly  116 . The actuators associated with the tip end portion gauge assembly  116  engage core locating surfaces  60   a  on core positioning members  62   a  disposed adjacent to the tip or left (as viewed in  FIG. 5 ) end portion of the lower die section  30   a . The registers  122 ,  124 ,  126 ,  134  and  136  hold data which indicates the position of the core locating surface  60   a  engaged by the actuator associated with the register. 
     The registers  122 ,  124 ,  126 ,  134 , and  136  are mechanical registers which are actuated by movement of actuators connected to the registers. However, the registers  122 ,  124 ,  126 ,  134  and  136  may be electrical registers or data storage units. If this is the case, a suitable power source, such as one or more batteries would be connected with the registers  122 ,  124 ,  126 ,  134  and  136 . 
     When the root end portion gauge assembly  114  ( FIG. 6 ) is to be utilized in positioning the core positioning members  62   a  adjacent to the root or right (as viewed in  FIG. 5 ) end portion of the lower die section  30   a , the root end portion gauge assembly is positioned on the lower die section  30   a  in the manner illustrated in  FIG. 7 . The base or support member  120  engages the lower die section  30   a  and spans a portion of the lower die section. The registers  122  and  124  are disposed above core positioning members  62   a  disposed in the lower right end portion of the lower die section  30   a . The register  126  is disposed above and is offset to one side of a third core positioning member  62   a  in the root end portion of the lower die section. 
     Actuators associated with the registers  122 - 126  engage the core locating surfaces  60   a  associated with the core positioning members  62   a  across which the base or support member  120  extends. One or more drive trains, corresponding to the drive trains  84  of  FIG. 4 , may be manually actuated to move the core positioning members  62   a  to the desired positions relative to the lower die section  30   a . The registers  122 - 126  have displays which indicate the positions of the associated core locating surfaces  60   a.    
     The tip end portion gauge assembly  116  is utilized in association with the core positioning members  62   a  adjacent to the tip or left (as viewed in  FIG. 5 ) end portion of the lower die section  30   a . When this is to be done, the base or support member  130  ( FIG. 6 ) of the tip end portion gauge assembly  116  is mounted on the tip or left (as viewed in  FIG. 5 ) end portion of the lower die section  30   a . The register  134  on the base or support member  130  ( FIG. 6 ) of the tip end portion gauge assembly  116  will be disposed above a core locating surface  60   a  at the tip end portion of the lower die section  30   a . The register  136  will be disposed above and offset to one side of a second core locating surface  60   a  associated with a second core positioning member  62   a  at the tip end portion of the lower die section  30   a.    
     The actuators for the registers  134  and  136  engage the core locating surfaces  60   a  at the tip end portion of the lower die section  30   a  and indicate the positions of the gauged core locating surfaces  60   a  relative to the lower die section  30   a . Drive trains, corresponding to the core drive trains  84  of  FIG. 4 , may be manually operated to effect movement of the associated core positioning members to the desired positions relative to the lower die section  30   a . The registers  134  and  136  have displays which indicate the positions of the associated core locating surfaces  60   a.    
     Embodiment of FIG.  8   
     In the embodiments of the invention illustrated in  FIGS. 1-7 , core positioning members  62  are illustrated in association with the lower section  30  of the die  20 . In the embodiment of the invention illustrated in  FIG. 8 , core positioning members are associated with both the lower die section and upper die section. Since the embodiment of the invention illustrated in  FIG. 8  is generally similar to the embodiments of the invention illustrated in  FIGS. 1-7 , similar numerals will be utilized to designate similar components, the suffix letter “b” being associated with the numerals of  FIG. 8  to avoid confusion. 
     A die  20   b  ( FIG. 8 ) includes a lower section  30   b  and an upper section  32   b . In accordance with one of the features of the embodiment of the invention illustrated in  FIG. 8 , core positioning members  62   b  are provided in association with both the lower die section  30   b  and upper die section  32   b . The core positioning members  62   b  connected with the lower die section  30   b  engage lower side of the core  24   b . Similarly, the core positioning members  62   b  associated with the upper die section  32   b  engage the upper side of the core  24   b.    
     Motors  74   b  are operable by a controller  80   b  to effect movement of the core positioning members  62   b  to desired positions relative to lower and upper die sections  30   b  and  32   b . The controller  80   b  includes a computer which is connected with and receives the output from the coordinate-measuring machine  40   b . This enables the computer in the controller  80   b  to determine a best fit spatial relationship of the actual core  24   b  to a spatial envelope for an ideal core, that is, to a spatial envelope corresponding to the spatial envelope  52  of  FIG. 3 . 
     In the embodiment of the invention illustrated in  FIG. 8 , the core positioning members  62   b  associated with the upper die section  32   b  are axially aligned with the core positioning members  62   b  associated with the lower die section  30   b . If desired, the core positioning members  62   b  associated with the upper die section  32   b  may be axially offset from the core positioning members  62   b  associated with a lower die section  30   b . It should be understood that either a greater or lesser number of core positioning members  62   b  may be associated with the upper die section  32   b  if desired. Similarly, either a greater or lesser number of core positioning members  62   b  may be associated with the lower die section  30   b . It should also be understood that gauge assemblies, corresponding to the gauge assemblies  114  and  116  of  FIG. 6 , may be utilized in association with the core positioning members  62   b  associated with the upper die section  32   b  as well as the lower die section  30   b.    
     Although core positioning members  62   b  have been illustrated in  FIG. 3  in association with both lower and upper die sections  30   b  and  32   b , the positioning members may be associated with only one of the die sections if desired. For example, core positioning members  62   b  may be associated with only the upper die section  32   b . Although motors  74   b  have been illustrated in  FIG. 8  in association with core positioning members  62   b  for both lower and upper die sections  30   b  and  32   b , the motors may be associated with core positioning members for only one of the die sections if desired. For example, motors  74   b  may be associated with core positioning members  62   b  for only the upper die section  32   b.    
     Conclusion 
     In the view of the foregoing description it is apparent that the present invention provides a new and improved method of forming a pattern  22  which includes a core  24  which is at least partially covered by wax  26 . The method includes providing an actual core  24  having dimensions which differ from dimensions of an ideal core, that is, a core which exactly conforms to a specific design for the core. A best fit spatial relationship of the actual core  24  to a spatial envelope  52  for the ideal core  24  may be determined. This results in space formed by the actual core  24  in a cast metal article having a best fit relationship with the cast metal article. If desired a best fit spatial relationship of the actual core  24  to a pattern die cavity  28  may be determined, rather than a best fit with an ideal core. 
     A die  20  having a plurality of core locating surfaces  60  is provided. The core locating surfaces  60  in the die  20  are movable between a plurality of positions, including ideal core locating positions in which the ideal core would be positioned in a desired spatial relationship relative to the die. The core locating surfaces  60  in the die  20  are movable to actual core locating positions which are offset from the ideal core locating positions. When the core locating surfaces  60  are in the actual core locating positions, an actual core  24  which is disposed in engagement with the core locating surfaces  60  is positioned in a best fit spatial relationship with the spatial envelope  52  for the ideal core. This results in the actual core  24  being positioned in a best fit relationship with a die cavity  28  in which the pattern  22  is formed. 
     The actual core  24  is positioned in engagement with the core locating surfaces  60  while the core locating surfaces are in the actual core locating positions. A flow of wax  26  is conducted into the die  20  while the actual core  24  is in engagement with the core locating surfaces  60  and while the core locating surfaces are in the actual core locating positions. 
     A plurality of motors  74  may be utilized to move the core locating surfaces  60  relative to the die  20 . In one embodiment of the invention, the core locating surfaces  60  which are moved by the motors  74  are disposed in association with only one section, for example, the lower section  30 , of the die  20 . However, motors  74  may be associated with locating surfaces  60  associated with a second section, in the example, the upper section  32 , of the die  20  if desired. 
     The present invention has a plurality of different features. These features may be utilized together as disclosed herein or may be utilized separately and/or in combination with features from the prior art. For example, core locating surfaces  60  may be moved by manually actuating one or more drive trains  84 . As another example, motors  74  may be utilized to move core locating surfaces  60  to positions other than positions in which an actual core  24  is positioned in a best fit relationship with a spatial envelope for an ideal core.