Systems and Methods for Undercut Features on Injected Patterns

Abstract

A method for creating undercut features in a wax pattern in an investment casting process is disclosed. The method comprises designing a tooling that includes a mold for an object with an aperture and a core corresponding in size and shape of the aperture. Then, the mold is used to injection mold a pattern for the object, wherein the pattern includes an opening corresponding to the aperture. Next, a plug from the core of the tooling is injection molded using the mold. The plug is press-fitted into the opening of the pattern and the opening of the pattern is sealed with the plug.

What is claimed is: 
     
         1 . A method for creating undercut features in a wax pattern in an investment casting process, the method comprising:
 designing a tooling, wherein the tooling includes a mold for an object having an aperture and wherein the tooling includes a core corresponding in size and shape of the aperture;   using the mold to injection mold a pattern for the object, wherein the pattern includes an opening corresponding to the aperture;   using the mold to injection mold a plug from the core of the tooling;   press-fitting the plug into the opening of the pattern; and   sealing the opening of the pattern with the plug.   
     
     
         2 . The method of  claim 1 , wherein the wax pattern is created using one of wax, plastic, and frozen mercury. 
     
     
         3 . The method of  claim 1 , wherein the undercut feature includes at least one of a thread, a snap feature, a blind opening, a negative tapered feature, a locking tab, a pocket, and a hole in side walls. 
     
     
         4 . The method of  claim 1 , wherein the plug is larger than the opening. 
     
     
         5 . The method of  claim 4 , wherein the edges of the plug are 0.001″ larger than corresponding edges of the opening. 
     
     
         6 . The method of  claim 1 , further comprising casting the pattern obtained after sealing the opening of the pattern to obtain a cast shaped like the object. 
     
     
         7 . The method of  claim 1 , wherein the object is a tibial baseplate implant. 
     
     
         8 . A system for creating undercut features in a wax pattern, the system comprising:
 a designing means to design a tooling, wherein the tooling includes a mold for an object with an aperture, and wherein the tooling includes a core corresponding in size and shape of the aperture;   a molding means to injection mold a pattern for the object and a plug from the core of the tooling, wherein the pattern includes an opening corresponding to the aperture;   a means to press-fit the plug into the opening of the pattern; and   a sealing means to seal the opening of the pattern with the plug.   
     
     
         9 . The system of  claim 8 , wherein the wax pattern is created using one of wax, plastic, and frozen mercury. 
     
     
         10 . The system of  claim 8 , wherein the undercut feature includes at least one of a thread, a snap feature, a blind opening, a negative tapered feature, a locking tab, a pocket, and a hole in side walls. 
     
     
         11 . The system of  claim 8 , wherein the plug is larger than the opening. 
     
     
         12 . The system of  claim 11 , wherein the edges of the plug are 0.001″ larger than corresponding edges of the opening. 
     
     
         13 . The system of  claim 8 , further comprising casting the pattern obtained after sealing the opening of the pattern to obtain a cast shaped like the object. 
     
     
         14 . The system of  claim 8 , wherein the object is a tibial baseplate implant. 
     
     
         15 . A tool for creating undercut features in a wax pattern in investment casting process, the tool comprising:
 a mold for an object with an aperture for forming a pattern for the object, wherein the pattern includes an opening corresponding of the aperture; and   a core corresponding in size and shape to the aperture for forming a plug, wherein the plug is press-fit into the opening of the pattern to seal the opening of the pattern.   
     
     
         16 . The tool of  claim 15 , wherein the wax pattern is created using one of wax, plastic, and frozen mercury. 
     
     
         17 . The tool of  claim 15 , wherein the undercut feature includes at least one of a thread, a snap feature, a blind opening, a negative tapered feature, a locking tab, a pocket, and a hole in side walls. 
     
     
         18 . The tool of  claim 15 , wherein the plug is larger than the opening, wherein the edges of the plug are 0.001″ larger than corresponding edges of the opening. 
     
     
         19 . The tool of  claim 15 , further comprising casting the pattern obtained after sealing the opening of the pattern to obtain a cast shaped like the object. 
     
     
         20 . The tool of  claim 15 , wherein the object is a tibial baseplate implant.