Investment casting utilizing flexible wax pattern tool for supporting a ceramic core along its length during wax injection

Abstract

An investment casting process wherein the wax pattern tool ( 42 ) is flexible to provide compliant support for an enclosed ceramic core ( 10 ) and to facilitate removal of the tool from the cast wax pattern ( 52 ) even when the cast shape would otherwise require multiple pull planes. Positioning pins ( 106 ) may extend from the flexible tool to make compliant contact against the core during the wax injection step. The pins may cooperate with a pedestal ( 128 ) formed on the core to support the core along multiple axes during wax injection, thereby allowing a higher wax injection pressure without damage to the core.

The invention claimed is: 
     
         1 . A method of producing a wax pattern for an investment casting process, the method comprising:
 positioning a ceramic core within a wax pattern mold;   supporting the ceramic core from a flexible surface of the mold;   injecting melted wax into the mold around the ceramic core; and   removing the mold after the wax has hardened to reveal the ceramic core encased inside a wax pattern.   
     
     
         2 . The method of  claim 1 , further comprising injecting the melted wax at a pressure of greater than 175 psig. 
     
     
         3 . The method of  claim 1 , further comprising supporting the ceramic core at a plurality of locations along its length during the step of injecting melted wax by locating a respective plurality of pins to extend from the flexible surface of the mold to make proximate contact with the core along a respective plurality of non-parallel axes. 
     
     
         4 . The method of  claim 1 , further comprising supporting the ceramic core at a location along its length during the step of injecting melted wax by locating a pin to extend from the flexible surface of the mold to make proximate contact with the core. 
     
     
         5 . The method of  claim 4 , further comprising aligning the pin to make proximate contact with a pedestal formed on the core to provide support for the core along a plurality of axes. 
     
     
         6 . The method of  claim 5 , further comprising forming the pedestal to have an opening defined by sloping walls for receiving the pin. 
     
     
         7 . The method of  claim 4 , further comprising:
 forming a recess in the flexible surface of the mold;   disposing a supporting element within the recess; and   installing the pin through an opening in the supporting element to extend toward the core.   
     
     
         8 . The method of  claim 7 , further comprising forming the recess and the supporting element to have cooperatively tapered sides. 
     
     
         9 . The method of  claim 4 , further comprising:
 forming a recess in the flexible surface of the mold;   supporting the pin from a fugitive material disposed within the recess; and   removing the fugitive material after the step of removing the mold.   
     
     
         10 . The method of  claim 1 , further comprising inserting a precision ceramic insert into a recess formed in the surface of the mold prior to the wax injection step, and removing the mold after the wax has hardened to reveal the wax pattern with the ceramic insert retained on a surface of the hardened wax. 
     
     
         11 . A tool for producing a wax pattern for an investment casting process, the tool comprising:
 a tool body comprising a flexible inner surface defining a desired outer surface geometry of the wax pattern;   a core disposed within the tool body, the core forming part of the wax pattern after a wax injection step and defining a wax injection volume between the core and the flexible inner surface; and   a metal pin supported by the flexible inner surface and extending through the wax injection volume to a position proximate the core effective for supporting the core during a wax injection step.   
     
     
         12 . The tool of  claim 11 , further comprising:
 a recess in the flexible inner surface of the tool body;   a supporting element disposed within the recess; and   an opening formed in the supporting element for receiving an end of the pin.   
     
     
         13 . The tool of  claim 11 , wherein the supporting element is formed to have tapered sides shaped to cooperate with tapered sides of the recess. 
     
     
         14 . The tool of  claim 11 , further comprising:
 a plurality of metal pins supported by the flexible inner surface and extending through the wax injection volume to a plurality of positions proximate the core effective for supporting the core along a respective plurality of axes during the wax injection step.   
     
     
         15 . The tool of  claim 14 , wherein at least two of the axes are not parallel. 
     
     
         16 . The tool of  claim 11 , further comprising a pedestal formed on the core proximate the pin to provide mechanical interference with the pin along a plurality of axes. 
     
     
         17 . The tool of  claim 16 , further comprising an opening formed by sloping walls of the pedestal for receiving the pin. 
     
     
         18 . The tool of  claim 16 , wherein the pedestal comprises a protruding undercut for creating mechanical interference with a head of the pin. 
     
     
         19 . The tool of  claim 12 , wherein the supporting element is formed of a fugitive material. 
     
     
         20 . The tool of  claim 11 , further comprising a precision ceramic insert disposed on the tool body inner surface.