Patent Publication Number: US-6986949-B2

Title: Fugitive patterns for investment casting

Description:
This is a division of Ser. No. 09/862,985 filed May 22, 2001, now U.S. Pat. No. 6,505,672. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to investment casting of metallic materials and to fugitive patterns for use in the investment casting process, pattern assemblies and apparatus for assembling patterns. 
     BACKGROUND OF THE INVENTION 
     In the well known “lost wax” process of investment casting, a fugitive or disposable wax pattern is made by injection molding melted wax in a die corresponding to the configuration of the article to be cast. Typically, each wax pattern includes integral wax gating. A plurality of such molded wax patterns then are joined to a common wax runner bar by wax welding the gating to the runner bar. A frusto-conical or other wax pour cup typically is wax welded to the runner bar to complete the pattern assembly. The pattern assembly is invested in a ceramic shell mold by repeatedly dipping the pattern in a ceramic slurry, draining excess slurry, stuccoing with coarse ceramic particles or stucco, and air drying until a desired thickness of a ceramic shell mold is built-up on the pattern assembly. The pattern assembly then is removed from the green shell mold typically by heating the shell mold to melt out the pattern assembly, leaving a ceramic shell mold which then is fired at elevated temperature to develop appropriate mold strength for casting a molten metal or alloy. 
     In the past, the wax patterns have been wax welded manually to the wax runner bar. Such manual wax welding is disadvantageous in that it is time consuming and costly as a result and also produces pattern assemblies that exhibit high variability from one pattern assembly to the next with respect to dimensional locations of the patterns on the runner bar and the strength of the wax weld between the pattern gating and the runner bar from one pattern to the next on the runner bar. Improper pattern positioning on the runner bar and breaking off of some patterns at the wax weld can occur. 
     An object of the invention is to provide a fugitive pattern and method of making a fugitive pattern assembly for use in the lost wax precision investment casting process that overcome the above disadvantages. 
     Another object of the invention is to provide apparatus for manipulating a fugitive pattern to position it relative to another component of a pattern assembly. 
     Another object of the invention is to provide an investment casting having features adapted to be engaged by a manipulator. 
     SUMMARY OF THE INVENTION 
     The present invention provides in one embodiment a fugitive pattern of an article to be investment cast wherein the pattern includes a plurality of locators disposed in an array to provide a datum reference system by which the pattern can be held and positioned by a manipulator, such as for example a gripper device pursuant to another embodiment of the invention coupled to a computer controlled robotic motion device, for assembly with another component of a pattern assembly. Preferably, the datum locators are located on a portion of the pattern that will be removed from the final metallic casting made to replicate the pattern. For example, the datum locators preferably are located on a gating region of the fugitive pattern such that the metallic gating is cut-off from the final casting in a one step cut-off operation. 
     In a particular embodiment of the invention, a plurality of locator embossments on the fugitive (e.g. wax) pattern define a reference plane that is positioned parallel to a plane of orientation determined for the surface of a fugitive (e.g. wax) support member, such as a runner bar. Prior to placing the attaching surface of the fugitive pattern in proximity to and facing the surface of the fugitive support member, a sensor on the gripper device is moved over the surface of the support member by the robotic motion device to determine planar orientation of a particular area of the support member surface where each successive pattern is to be attached, which planar orientation is stored in robot control unit memory. When the pattern attaching surface is then placed proximate and facing the area of the surface of the support member, the gripper device is manipulated by the robotic arm to orient the pattern attaching surface so as to have substantially the same orientation as the sensed and stored planar orientation. 
     The present invention provides in another embodiment a method of making a fugitive pattern assembly by placing an attaching surface of a fugitive pattern in proximity to and facing a surface of a fugitive support member, such as for example, a wax runner bar. A heating device is placed between the attaching surface of the pattern and the surface of the support member to melt a puddle of the fugitive material on the surface of the support member and soften but not melt the pattern attaching surface. The heating device is removed. The pattern and support member then are relatively moved to contact the pattern attaching surface and the melted puddle, which is solidified during such contact to form a joint therebetween. Preferably, the pattern is manipulated by a robotic device in a manner that the attaching surface of the pattern is first moved a preselected distance below the surface of the melted puddle and then moved in an opposite direction a lesser preselected distance to form a smooth filleted corner at the joint between the pattern and the support member. 
     The invention provides in another embodiment a gripper device for gripping a fugitive pattern to accurately position it relative to another component of a pattern assembly. The gripper device preferably includes a position sensing device and heating device that is movable in a manner to melt a puddle of pattern material on the component to be assembled to the pattern. 
     The fugitive pattern having the above locators thereon is used in the lost wax investment casting process to cast an article that includes a plurality of integral locators disposed in an array to provide a datum reference system by which the cast article can be held and positioned by a manipulator for further processing. 
     Objects and advantages of the invention will become more readily apparent from the following detailed description. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a robotic device for use in positioning a plurality of wax airfoil patterns relative to a wax runner bar for welding thereto to form a pattern assembly pursuant to an embodiment of the invention. 
         FIG. 1A  is a perspective view of a fixture for holding the runner bar. 
         FIG. 1B  is a sectional view taken along lines  1 B— 1 B of  FIG. 1A . 
         FIG. 1C  is a sectional view taken along lines  1 C— 1 C of  FIG. 1A . 
         FIG. 2  is a perspective view of a pattern having locator embossments thereon for gripping by a gripper device pursuant to the invention on the motion arm of the robotic device. 
         FIGS. 3A and 3B  are front and rear perspective views of the gripper devicehaving a radiant heating device and distance sensor. 
         FIG. 3C  is front perspective view of an alternative gripper device having a hot air heating device. 
         FIGS. 4A ,  4 B,  4 C are schematic views illustrating capture of the gating region of the pattern by the gripper device. 
         FIG. 5  is a perspective view of the gripper device showing the heating device pivoted away from the gripper arms. 
         FIG. 6  is perspective view of the runner bar, gating region of the pattern and heating iron pivoted therebetween. 
         FIGS. 7A ,  7 B, and  7 C are partial elevational views, partially in section, showing the sequence of motions of the pattern to space the gating region from the runner bar ( FIG. 7A ), to submerge the gating region a small distance in the melted puddle ( FIG. 7B ), and withdraw the gating region in the melted puddle to form a rounded filleted corner on the joint ( FIG. 7C ).  FIG. 7D  is a partial elevational view, partially in section, showing the pattern orientation parallel to a runner bar surface having a tilted planar orientation. 
         FIG. 8  is a perspective view of multiple patterns welded onto the runner bar with smooth filleted corners at the joints. 
         FIG. 9  is a perspective view of the gating region of a pattern having embossments thereon for gripping by a gripper device pursuant to another embodiment of the invention. 
         FIG. 10  is a perspective view of casting made using the pattern of  FIG. 2  wherein the casting includes locator embossments. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides a fugitive pattern and a fugitive pattern assembly for use in the lost wax investment casting process employed in the high volume commercial production of metal and alloy cast articles. The invention is described below for purposes of illustration, and not limitation, in relation to a fugitive pattern for making a pattern assembly for use in the lost wax investment casting of precision nickel and cobalt superalloy components, such as gas turbine engine blades and vanes having airfoil shapes, although the invention is not limited in this regard and can be practiced using other patterns to make pattern assemblies for use in the lost wax investment casting of any metal or alloy to make any article. The invention is especially useful to make a pattern assembly having a plurality of wax patterns joined to a wax runner bar or any other wax component of the pattern assembly. The patterns, runner bar, and other component of the pattern assembly can be made of any suitable fugitive pattern material, such as conventional pattern wax, solid or foam plastic (e.g. polymeric foam such as polyurethane foam). 
     Referring to  FIG. 1 , a plurality of individual fugitive (e.g. wax) patterns  10  having a shape of a gas turbine engine airfoil blade are shown. The patterns  10  each include an airfoil region  12 , root region  13 , platform region  14 , optional shrouded tip region  15 , and gating region  16 ,  FIG. 2 . The patterns  10  typically are injection molded of conventional pattern wax although other pattern materials and pattern making methods can be employed. 
     Pursuant to the invention, each pattern  10  is injected to include a plurality of datum locators illustrated as datum embossments  20   a ,  20   b ,  20   c  disposed in an array to provide a datum reference system on each pattern by which each pattern can be held and positioned by a manipulator, such as for example a gripper device  60  pursuant to the invention coupled to a computer controlled robotic device  30 ,  FIG. 1 , for assembly with another component of the pattern assembly. 
     For example, the gating region  16  of each pattern  10  includes a flat planar attaching surface  16   a  adapted for attachment to a surface  40   a  of a fugitive runner support bar  40  as described below. The flat planar attaching surface  16   a  can comprise a flat, narrow peripheral attaching lip  161  extending about an end recess  16   r  molded in the attaching surface  16   a ,  FIGS. 6 and 7A . The recess  16   r  is shaped and sized to receive a support member PP on table T,  FIG. 1 . 
     The pattern gating region  16  includes first and second locator embossments  20   a ,  20   b  on opposite side surfaces  16   s   1  and  16   s   2  that extend perpendicular to the attaching surface lip  16   l  on the gating region  16 . The first and second embossments  20   a ,  20   b  are coaxial and define a first axis A 1 . The embossments  20   a ,  20   b  are illustrated as being defined by partial spherical surfaces  20   s  such that the axis A 1  extends through the centers of the partial spherical surfaces. A third locator embossment  20   c  is disposed on a lateral surface  16   k  extending between the opposite side surfaces  16   s   1 ,  16   s   2  of the gating region  16 . The third embossment  20   c  defines a second axis A 2  that is coplanar and perpendicular to the first axis A 1 . The embossment  20   c  is illustrated as being defined by a partial spherical surface  20   s  such that the axis A 2  extends through the center of the partial spherical surfaces. 
     The three locator embossments  20   a ,  20   b ,  20   c  are disposed in a triangular array and define a reference plane P 1 ,  FIG. 7A , that is parallel to the plane defined by the attaching surface lip  16   l  and is positioned parallel to the plane P 2  determined for surface  40   a  of the fugitive runner bar  40  during attachment of the pattern attaching surface  16  to the flat planar runner bar surface  40   a  as described below. The invention is not limited to the particular array of locator embossments  20   a ,  20   b ,  20   c  illustrated as other arrays and numbers of embossments thereof can be employed as needed in a particular lost wax investment casting application for a particular article to be cast. 
     The locator embossments  20   a ,  20   b ,  20   c  each are configured to have a relatively short cylindrical section  201  that terminates in partially spherical end surface  20   s ,  FIG. 7B . The dimensions of the embossments are selected so as to be grippable by gripper device  60  pursuant to the invention coupled to the articulated arm  30   a  of the robotic device  30 . The end surfaces  20   s  can have a shape other than partially spherical such as for example only conical, polyhedral, and parabolic. The locator embossments are illustrated as projections from the pattern gating  16 , but alternatively the locators  20   a ,  20   b ,  20   c  could be shaped as recessed pockets or concavities extending inwardly into the pattern gating. 
     The datum locator embossments  20   a ,  20   b ,  20   c  pursuant to an illustrative embodiment of the invention are injection molded integrally on each pattern  10  in a conventional die cavity (not shown) machined to have the shape and features of the pattern  10  described above as well as to include cavities corresponding in size, shape and location to the datum embossments to be formed on the gating region  16 . Each pattern  10  is formed by injecting molten pattern wax (or other fugitive material) into the die cavity where the wax solidifies to produce pattern  10  as is well known in the lost wax investment casting art. The injection molded wax pattern  10  includes the datum embossments  20   a ,  20   b ,  20   c  molded integrally with and on the gating region  16  thereof as shown in  FIGS. 1 and 2 . 
     Preferably, the datum locator embossments  20   a ,  20   b ,  20   c  are located on the gating region  16 , or other portion, of each pattern  10  that will be removed from the final metallic casting made to replicate the pattern. For example, the datum embossments preferably are located on the gating region  16  such that the metallic gating is cut-off from the final casting (e.g. from the root region  13 ) in one step cut-off operation. 
     In addition to the datum locator embossments  20   a ,  20   b ,  20   c  on the gating region  16 , each pattern  10  may also include another similar set of datum locator embossments (not shown) at another gating region in the event that the pattern  10  will include dual gating regions; e.g. the gating region  16  associated with the root region  13  and another similar gating region (not shown) associated with the shrouded blade tip region  15 . 
     Referring to the Figures, a method of making a fugitive pattern assembly pursuant to the invention for use in the lost wax investment casting process is illustrated. For example, assembly of the fugitive patterns  10  on the generally flat surface  40   a  of the runner support bar or member  40  fixtured on a table T is illustrated. The runner support bar  40  includes flat bar region  40   b  with flat major surfaces  40   a ,  40   a ′ on opposite sides of the bar region. The bar region  40   b  is connected to an integral conical pour-cup attaching region  40   c . The pour cup-attaching region  40   c  includes a threaded insert  40   d  fixedly embedded therein during wax molding of bar  40 . Alternately, the pour cup-attaching region  40   c  can be separate and attached to bar region  40   b  by wax welding. Referring To  FIGS. 1 ,  1 A,  1 B, and  1 C, a fixture  31  is provided having a central truncated conical clamp  32  against which shoulder  40   e  of the pour cup-attaching region  40   c  is drawn and clamped by a bolt knob  33  having threaded member  33   a  threaded into the insert  40   d  as shown best in  FIG. 1B . The fixture  31  also include legs  34 ,  35  having V-notches  34   a ,  35   a  on the edges such that longitudinally spaced apart partial spherical embossments  40   s  molded on the facing minor side of the bar region  40   b  are received and held in the notches when the pour-cup-attaching region  40   b  is clamped in clamp  32 ,  FIG. 1C . The table T has affixed thereto an upstanding lower yoke section Y 1  which is configured to receive the exterior of clamp  32  of the fixture. An upper yoke section Y 2  is fastened on the lower yoke section Y 1  to secure and clamp the clamp  32  of fixture  31  on the table T. The bar region  40   b  is suspended above the table T by the yoke sections Y 1 , Y 2  and fixture  31  with surface  40   a  generally parallel with the plane of the table T. The invention is not limited to any particular fixturing for the runner support bar  40  as other fixturing devices can be used. 
     A plurality of fugitive patterns  10  are shown disposed at a pick-up location PL on the table T. Each pattern  10  is supported on the table T by an epoxy (or other material) plate PP that is shaped and sized to be received in the end recess  16   r  of the pattern attaching surface  16   a  to support the pattern with the plane P 1  parallel to the plane of the table T. 
     The robotic motion device  30  on the table T includes articulated arm  30   a  with gripper device  60  pursuant to an embodiment of the invention. Each pattern is individually picked up by the gripper device  60  and positioned in proximity to the runner bar surface  40   a  for attachment thereto. The robotic device  30  can be a conventional robot of the 6-axis type available as model K 3  from Motoman Inc. a part of Yaskawa Corporation,  805  Liberty Lane, W. Carrollton, Ohio 45449. 
     The gripper device  60  is adapted to pick up each pattern  10  at locator embossments  20   a ,  20   b ,  20   c  so that the arm  30   a  of robotic device  30  can orient each pattern attaching surface  161  (which is parallel to plane Pi defined by embossments  20   a ,  20   b ,  20   c ) parallel to the runner bar surface  40   a  during attachment thereto as described below. To this end, the gripper device  60  includes a mounting plate  62  that carries a conventional coupling  64  for connection to the articulated arm  30   a  of the robotic motion device  30 . A second, downwardly extending mounting plate  66  is fastened to mounting plate  62 . First and second gripper arms  72 ,  74  are mounted on plate  66 . The first gripper arm  72  is fixedly mounted by fasteners on plate  66 , while the second gripper arm  74  is fastened to rod  75   a  of a fluid (e.g. pneumatic) cylinder  75 . Cylinder  75  is mounted on fixed support plate  73  that is fastened on downwardly extending plate  66 . The gripper arm  74  is linearly moved by fluid cylinder  75 . The cylinder  75  is actuated via opening/closing of a fluid (e.g. air) valve  77  that is communicated to compressed air source C as controlled by robot control unit  100  and to an air conduit on arm  30   a  that extends to cylinder  75 . 
     The gripper arms  72 ,  74  each include an embossment-engaging conical recess  72   a ,  74   a  adapted to receive the side embossments  20   a ,  20   b  on the gating region  16  of each pattern  10 . The recesses  72   a ,  74   a  are coaxial when the arms  72 ,  74  receive and grip the embossments  20   a ,  20   b.    
     A third fixed gripper arm  78  is fastened by fasteners on fixed plate  66  and includes a notch  78   a  which can have a partial cylindrical shape or V shape to receive the embossment  20   c  of the gating region  16  of the pattern. The axis A 3  of the notch  78   a ,  FIG. 4B , is parallel to the axis A 1  and perpendicular to axis A 2  and resides in plane P 1 . 
     If the patterns  10  have locators  20   a ,  20   b ,  20   c  in the form of shaped recessed pockets or concavities, then gripper arms  72 ,  74 ,  78  will be appropriately modified to include pick-up projections, in lieu of recesses  72   a ,  74   a  and notch  78   a , to enter the locator pockets or concavities in a manner to enable the gripper device to pickup each pattern  10 . 
     The gripper device includes a heating device  65  comprising a radiant metal (e.g. aluminum) heating iron  65   a  having electrical resistance heating elements  65   b  received in passages on each side of the iron  65   a ,  FIG. 3A . The heating elements  65   b  are connected by electrical power wires  65   c  to a source S of electrical power, which is switched on and off by a stationary temperature controller (not shown), such as an Omron E5AX controller available from Omron Electronics, One E Commerce Drive, Schaumburg, Ill. 60173. The power wires  65   c  are loosely carried on the robotic arm  30   a  to source S, which can be locate external of the robotic motion device  30  (e.g. beneath table T). When the elements are electrically energized, they heat the heating iron  65   a  in a manner similar to a soldering iron. 
     The radiant heating iron  65   a  is disposed and carried on a depending arm  65   d  and is adjustable in a lateral direction E by sliding arm  65   d  along bracket  65   g . Arm  65   d  and bracket  65   g  are releasably fastened by one or more fasteners  65   t  to this end. Arm  65   d  is adjustable up and down by sliding mounting block  65   n  on slideway  63  attached to plate  62  and held in position by one or more fasteners  65   f . Thermal insulating member  65   i  is disposed between heating iron  65   a  and the arm  65   d  with thermally insulating gasket material (e.g. insulation wool)  65   s  applied between each side of insulating member  65   i . Multiple fasteners (not shown) extend upwardly through the heating iron  65   a , insulating member  65   i , and gasket material  65   s  into the bottom of the arm  65   d  to fasten them together. Heating elements  65   b  other than electrical resistance elements can be used in practice of the invention. 
     The bracket  65   g  is bifurcated and mounted by a pair of pivot pins  65   m  to mounting block  65   n . The heating device  65  thereby is pivotally mounted for movement between a stowed position shown in  FIGS. 1 and 5  and a working position shown in  FIG. 3A ,  6  and  7 A. The heating iron  65   a  is moved between these positions by an actuator such as a fluid (e.g. pneumatic) actuator  69  fastened on bracket  67  itself fastened to plate  66 . The cylinder rod  69   a  of cylinder  69  is connected to the bracket  65   g  as shown. The cylinder  69  is actuated via opening/closing of a fluid (e.g. air) valve  71  that is communicated to source C of compressed air (or other fluid) as controlled by robot control unit  100  and to an air conduit on arm  30   a  extending to cylinder  69 . 
     In lieu of radiant heating iron  65   a , the heating device  65  can comprise a forced hot air heating device,  FIG. 3C , where the heating iron  65   a  is hollowed out to include two plenums  65   p   1 ,  65   p   2  into which compressed air is supplied for discharge through a plurality of apertures  65   h  in end plates  65   u  disposed on opposite major sides of the iron  65   a  to close off and communicate to the respective plenums via apertures  65   h  in the plates. Electrical resistance heating elements  65   b  can be disposed in the plenums or outside in the body of iron  65   a . The compressed air is supplied to the plenums through a passage  65   v  in arm  65   d  or a conduit (not shown) on arm  65   d  connected to a source of compressed air, such as shop air. The supply of compressed air to the plenums can be controlled by robot control unit  100  programmed to open/close one or more air control valves (not shown) at appropriate times. The air flow through the apertures  65   h  on bottom plate  65   u  is used to heat the surface  40   a  of the runner bar  40  to form puddle MP, while the hot air flow through the apertures  65   h  on top plate  65   u  is used to heat the surface lip  161  of the pattern  10  prior to their being joining together. 
     The gripper device  60  includes a commercially available laser distance sensor  80  that directs a laser beam B downwardly in a direction that passes through the intersection of axis Al and axis A 2 ,  FIG. 3B . The sensor  80  is used to determined the orientation of the particular surface area  41  of runner bar surface  40   a  where each pattern is to be attached as described below. A suitable laser sensor is available from Omron Electronics, One E Commerce Drive, Schaumburg, Ill. 60173. 
     Pursuant to a method embodiment of the invention, the patterns  10  are positioned on flat, horizontal table T at pick-up location PL so that the plane P 1  defined by embossments  20   a ,  20   b ,  20   c  resides generally in a horizontal plane parallel with the plane of the table T. The supports PP are used to this end as described above. 
     Prior to picking up each pattern at location PL on the table, the sensor  80  on the gripper device is moved over the area  41  of surface  40   a  where the pattern  10  will be attached to the support member  40  by the robotic motion device,  FIG. 8 . The sensor  80  determines a planar orientation of the area  41  by measuring the distance between the sensor and multiple points (e.g. see 3 points PT for a Cartesian coordinate system in  FIG. 8 ) on the particular area  41 . From this data, the robot control unit  100  determines a planar orientation of the area  41  (e.g. angle of surface area  41  relative to horizontal) and stores the planar orientation in robot control memory  102 . Software systems for determining planar orientation in this manner are available commercially and provided on the above described commercially available robotic device  30 . 
     Determination of the planar orientation of the surface area  41  of the runner bar  40  in the manner described is practiced pursuant to an embodiment of the invention as a result of the uneven nature of surface  40   a  of the runner bar  40  as injection molded. For example, the surface  40   a  of the runner bar  40  typically exhibits unevenness along its length and across its width such that particular areas  41  are not level with one another.  FIG. 7D  illustrates a tipped surface area  41  on runner bar  40  for example, the tilted surface area  41  not being horizontal. If the runner bar  40  can be produced or modified (e.g. machined) to have a perfectly flat surface  40   a  and oriented parallel to the plane of the table by fixture  31  and yokes Y 1 , Y 2 , then the step of determining planar orientation of each respective surface area  41  and step of storing the orientation in robot control memory  102  may be omitted. 
     Otherwise, after the robotic device  30  determines the planar orientation of the area  41  on surface  40   a , it manipulates the gripper device  60  to pick up a pattern  10  for movement and attachment to the area  41  on runner bar  40 . For example, the gripper device  60  first is moved in direction of the arrow in  FIG. 4A  until the fixed gripper arms  72  and  78  are positioned to receive the embossments  20   a ,  20   c ,  FIG. 4B . The sensor  80  can be used to confirm that a pattern  10  is in position to be picked-up. Then, the movable gripper arm  74  is moved linearly by cylinder  75  toward the embossment  20   b  until the embossment  20   b  is received in the recess  74   a  thereof,  FIG. 4C . In this way, the arms  72 ,  74  and  78  securely capture the coplanar embossments  20   a ,  20   b ,  20   c  of the gating region  16  of each pattern  10 . The robot control unit  100  controls air valve  77  to actuate cylinder  75 . 
     The pattern  10  is lifted from the pick-up location PL by the robotic arm  30   a  while the gripper device  60  holds the gating region  16  at the locator embossments and is moved to the surface area  41  where its attaching surface lip  161  will be attached to the surface  40   a  of the runner support bar  40  held in fixtue  31  and yokes Y 1 , Y 2 . The pattern attaching surface lip  16   l  is placed by robotic arm  30   a  in proximity to and facing surface area  41  of runner bar  40  as illustrated in  FIG. 7A . For example, distance D 1  can be 1 inch. 
     Since the planar orientation of the surface area  41  is stored in robot control memory  102 , the robotic arm  30   a  is manipulated to orient the pattern attaching surface  16   a  of the pattern  10  on gripper device  60  so as to have substantially the same orientation as the sensed and stored planar orientation of surface area  41 . That is, the pattern attaching surface lip  16   l  is oriented to be substantially parallel to the sensed plane defined by surface area  41  on the runner bar  40 , see  FIG. 7A  for a horizontal surface area  41  and see  FIG. 7D  for a tipped out of horizontal surface area  41 . 
     Heating device  65  then is pivoted from its stowed to its working position between the pattern attaching surface lip  16   l  and runner bar surface area  41  in proximity to each surface (e.g. distances D 2 =0.3 inch and D 3 =0.025 inch),  FIG. 7A . The heating iron  65   a  is electrically energized for a time to maintain a constant iron temperature (e.g. 700 degrees F.) that radiantly heats the surfaces to melt a puddle MP of the fugitive (e.g. wax) material on the surface area  41  of the runner bar  40  and to soften but not melt the pattern attaching surface lip  16   l . The puddle MP has a general configuration corresponding to the shape of the heating iron  65   a  and pattern attaching surface lip  16   l  with the puddle larger in size. For purposes of illustration only, the melted puddle MP can have a depth of 0.050 inch. The heating iron then is quickly moved by cylinder  69  back to its stowed position on the gripper device  60 . The pattern is lowered by robotic arm  30   a  to lower attaching surface lip  16   l  into the puddle MP to a preselected depth D 4  (e.g. 0.030 inch depth) to wet the upstanding edges  16   w  of the gating region  16  extending about the attaching surface  16   a  (i.e. lip  16   l ) with the melted puddle material,  FIG. 7B . The pattern then is raised by arm  30   a  to move attaching surface lip  161  in the opposite direction in the puddle MP to a preselected lesser depth (e.g. 0.010 inch) to form a smooth filleted corner C at the junction between the pattern gating  16  and the runner bar surface  41   a ,  FIG. 7C . The pattern is held in this position by the robot arm  30   a  until the melted fugitive material solidifies to complete the final joint between the pattern gating  16  and the runner bar surface  40   a . Joints formed in this manner are characterized by improved strength and absence of stress-raising sharp corners with no dimensional distortion of the patterns  10 . 
     The gripper device  60  then is released from the pattern  10  now joined to the runner bar  40  by first moving gripper arm  74  away from and out of engagement with locator embossment  20   b  and manipulating the robotic arm  30   a  to move the gripper arms  72 ,  78  away from and out of engagement with locator embossments  20   a ,  20   c  such that the gripper device  60  can be moved by robotic arm  30   a  back to pick-up location PL to pick-up the next pattern  10  to be joined to the runner bar  40 . The above pattern moving and attaching steps are repeated to attach the next and each successive pattern  10  to a different surface area  41  on the runner bar  40  to form a pattern assembly  110  having a plurality of patterns  10  joined to the runner bar  40 ,  FIG. 8 . 
     The robotic motion device  30  is programmed to move the arm  30   a  and gripper device  60  to effect motions of the gripper device  60  described above and to effect actuation of the fluid cylinder  69  for the pivotal arm  65   d  of the heating device  65  and the fluid cylinder  75  for the linearly movable arm  74  of the gripper device  60 . 
     Although the illustrative embodiment of the invention described above involves moving each pattern  10  toward the melted puddle MP to form the joint J, the invention envisions any combination of relative movement between the pattern and the runner bar to contact the pattern attaching surface  16   a  and the melted puddle MP. For example, the runner bar  40  may be disposed on a secondary table (not shown) that is disposed on table T and that is movable up and down to this end. 
     After the patterns  10  are attached to the surface  40   a  of the runner support bar  40 , the fixture  31  can be removed from the yokes Y 1 , Y 2 , and the runner bar  40  with fixture  31  thereon reoriented to orient the opposite surface  40   a ′ of the bar region  40   b  to face upwardly. The fixture  31  then is reclamped between the yokes Y 1 , Y 2  so that patterns  10  can be attached to surface  40   a ′ in the same manner as described above for surface  40   a  to complete a pattern assembly  110 . After the pattern assembly  110  comprising patterns  10  attached to surfaces  40   a ,  40   a ′ of runner bar  40  is completed, a wax (or other fugitive material) pour cup (not shown) typically is attached to the pour cup-attaching region  40   c . The pattern assembly with pour cup then is invested in ceramic to form a ceramic shell mold about the pattern assembly pursuant to the well known lost wax process where the pattern assembly is repeatedly dipped in a ceramic slurry, drained of excess slurry, stuccoed with coarse ceramic particles or stucco, and air dried until a desired thickness of a ceramic shell mold is built-up on the pattern assembly. The pattern assembly then is removed from the green shell mold typically by heating the shell mold to melt out the pattern assembly, leaving a ceramic shell mold which then is fired at elevated temperature to develop appropriate mold strength for casting a molten metal or alloy. When removed from the shell mold, the patterns  10  form the mold cavities to receive molten metal or alloy, while the runner bar forms a molten metal or alloy supply runner to the mold cavities from a pour cup, all as is well known. 
     The cast metallic articles  200 ,  FIG. 10 , formed in the mold cavities will have a shape (e.g. airfoil blade) replicating that of each pattern  10 . Each individual cast article (airfoil blade)  200  includes an airfoil region  212 , root region  213 , platform region  214 , optional shrouded tip region  215 , and gating region  216 ,  FIG. 10 . The cast metallic articles  200  are each removed from solidified metal or alloy of the runner (that replicates runner bar  40 ) by a cut-off operation that cuts each gating region  16  off of the runner. Each cast article  200  also will include a plurality of datum locators illustrated as embossments  220   a ,  220   b ,  220   c  disposed in an array on gating region  216  to provide a datum reference system on each cast article by which each cast article can be held and positioned by a manipulator, such as for example a robotic gripper device similar to gripper device  60  employed to move the patterns  10 . The cast datum locator embossments provide a datum reference system by which the cast articles  200  can be held and positioned by the robotic gripper device for further processing such as for example grinding, polishing, and inspection of the cast article (blade)  200 . The gating region  216  of each cast article  200  is cut-off from the root region  213  at an appropriate time after further processing of the cast articles  200 . 
     The pattern gating region  216  includes first and second locator embossments  220   a ,  220   b  on opposite side surfaces  216   s   1  and  216   s   2  that extend perpendicular to the surface lip  2161  on the gating region  216 . The first and second embossments  220   a ,  220   b  are coaxial and define a first axis A 21 . The embossments  220   a ,  220   b  are illustrated as being defined by partial spherical surfaces  220   s  such that the axis A 21  extends through the centers of the partial spherical surfaces. Third embossment  220   c  is disposed on a lateral surface  216   k  extending between the opposite side surfaces  216   s   1 ,  216   s   2  of the gating region  216 . The third embossment  220   c  defines a second axis A 22  that is coplanar and perpendicular to the first axis A 21 . The embossment  220   c  is illustrated as being defined by a partial spherical surface  220   s  such that the axis A 22  extends through the center of the partial spherical surfaces. If the patterns  10  have locators  20   a ,  20   b ,  20   c  in the form of shaped recessed pockets or concavities, then each cast article  200  will have an array of datum locators in the shape of recessed pockets or concavities for gripping by a robotic gripper device having gripper arms modified to this end. 
     The three cast locator embossments  220   a ,  220   b ,  220   c  are disposed in a triangular array and define a reference plane that contains axes A 21  and A 22  and that is parallel to the plane defined by the surface lip  2161 . The invention is not limited to the particular array of embossments  220   a ,  220   b ,  220   c  illustrated as other arrays and numbers of embossments thereof can be employed for a particular cast article. 
     Referring to  FIG. 9 , an alternative gripper device  160  is shown and differs from gripper device  60  in having all three arms  172 ,  174 ,  178  disposed on robotic arm  30   a  and pivotable in the directions of the arrows to grip on embossments  20   a ,  20   b ,  20   c  of the gating region  16  of fugitive pattern  10  at aforementioned pick-up location PL. Each arm  172 ,  174  includes a conical recess  172   a ,  174   a  to receive embossment  20   a ,  20   b . Arm  178  includes a partial-cylindrical or V-groove  178   a  to receive embossment  20   c . Each arm can be actuated to pivot by a suitable fluid, electric or other actuator (not shown) mounted on the arm  30   a  and controlled by the computer control unit  100 . 
     Although certain detailed embodiments of the invention are disclosed herein, those skilled in the art will appreciate that the invention is not limited to these embodiments but only as set forth in the following claims.