Core and pattern manufacture for investment casting

Abstract

Method and apparatus for making a ceramic core or fugitive pattern for use in investment casting wherein a fluid ceramic core or pattern material is introduced into a molding cavity defined by cooperating dies, and at least a region of one or both of the dies is heated during filling of the molding cavity with the material and then cooled to a lower ejection temperature before removal of a ceramic core or pattern from the molding cavity.

We claim:  
     
         1 . A method of making a molded body for use in investment casting, comprising filling a molding cavity disposed between cooperating dies with a fluid material selected to form a ceramic core or a fugitive pattern, heating at least a region of at least one of said dies to a superambient temperature during filling of said molding cavity, and cooling said local region to a lower temperature before removal of a molded body from said molding cavity.  
     
     
         2 . The method of  claim 1  wherein said region of said at least one of said dies is heated and cooled by at least one thermoelectric element disposed thereon.  
     
     
         3 . The method of  claim 2  including sensing temperature of said region and controlling said at least one thermoelectric element in response to sensed temperature.  
     
     
         4 . The method of  claim 2  wherein said region comprises a trailing edge-shaped region of an airfoil, said trailing edge-shaped region being heated prior to and during filling of said molding cavity and cooled before removal of said molded body from said molding cavity.  
     
     
         5 . The method of  claim 4  wherein said trailing edge-shaped region includes relatively narrow channels that are heated by said at least one thermoelectric element to permit filling thereof with said fluid material.  
     
     
         6 . The method of  claim 1  wherein said region of said at least one of said dies is heated and cooled by at least one fluid passage disposed therein.  
     
     
         7 . The method of  claim 2  including removing heat from said at least one thermoelectric element using a heat exchange fluid.  
     
     
         8 . The method of  claim 7  wherein said heat exchange fluid is selected from the group consisting of a liquid and gas.  
     
     
         9 . The method of  claim 1  wherein said fluid material comprises a ceramic core material comprising ceramic flour and a fluid binder.  
     
     
         10 . The method of  claim 1  wherein said fluid material comprises a pattern material selected from the group consisting of a wax and a polymer.  
     
     
         11 . Apparatus for molding an airfoil-shaped body for use in casting a metallic airfoil, comprising first and second dies defining a molding cavity having an airfoil-shaped cavity, and at least one thermoelectric element disposed on at least one of said dies to heat at least a hard-to-fill region of said cavity to a superambient temperature during filling of said molding cavity with a fluid material, and to cool said region to a lower temperature before an airfoil-shaped body is removed from said molding cavity.  
     
     
         12 . The apparatus of  claim 11  including a temperature sensor proximate said region and an electrical power controller connected to said at least one thermoelectric element to control electrical power thereto in response to sensed temperature.  
     
     
         13 . The apparatus of  claim 11  including a heat exchanger in thermal contact with said thermoelectric element.  
     
     
         14 . The apparatus of  claim 13  including an inlet conduit conducting a heat exchange fluid to said heat exchanger to remove heat therefrom and an outlet conduit for exhausting said heat exchange fluid.  
     
     
         15 . The apparatus of  claim 11  including a thermally conductive material disposed between said at least one thermoelectric element and said at least one of said dies for conducting heat from said at least one thermoelectric element.  
     
     
         16 . The apparatus of  claim 11  wherein said molding cavity has a configuration of a ceramic core.  
     
     
         17 . The apparatus of  claim 11  wherein said molding cavity has a configuration corresponding to a pattern that replicates said airfoil-shaped body.  
     
     
         18 . Apparatus for molding an airfoil-shaped body for use in casting a metallic airfoil, comprising first and second dies defining a molding cavity having an airfoil-shaped cavity, and at least one fluid passage on at least one of said dies to provide a fluid to heat at least a hard-to-fill region of said cavity to a superambient temperature during filling of said molding cavity with a fluid material, and to cool said region to a lower temperature before an airfoil-shaped body is removed from said molding cavity.  
     
     
         19 . The apparatus of  claim 18  wherein said molding cavity has a configuration of a ceramic core.  
     
     
         20 . The apparatus of  claim 18  wherein said molding cavity has a configuration corresponding to a pattern that replicates said airfoil-shaped body.