Metal Core Wax Pattern for Turbine Stator Casting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing manufacturing process for bladed annular stator assemblies in turbomachines, which involves a ceramic core for forming cavities, results in costly plugging of orifices and reduces mechanical strength due to brazed parts and core deformation during wax injection, leading to increased costs and reduced assembly life.
Innovation Solution
A method using a metal core with a tapered section, mounted only by its radially outer end, to minimize deformation and eliminate the need for plugging orifices, combined with a ceramic core for better thermal resistance and easier chemical removal, facilitating the production of bladed annular assemblies with improved structural integrity and reduced manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a ceramic core is used to form cavity imprints, then thermal resistance is sufficient to withstand high casting temperatures, but the core deforms under wax injection pressure causing precision degradation and requiring costly plugging operations
Solution Approach 1:
The core is divided into two distinct segments: a metal core portion for structural support and pressure resistance during wax injection, and a ceramic core portion for thermal resistance during metal casting. This segmentation allows each material to perform its optimal function without compromise.
Solution Approach 2:
The invention uses a composite core structure combining metal and ceramic materials. The metal portion (e.g., stainless steel) provides mechanical strength and dimensional stability under pressure, while the ceramic portion (e.g., alumina) provides thermal resistance during the casting process. This composite approach resolves the contradiction between thermal resistance and deformation resistance.
2Manufacturing precision
If the core is firmly mounted to minimize deformation, then manufacturing precision is maintained, but orifices are formed in the inner shroud requiring plugging operations that increase cost and reduce mechanical strength
Solution Approach 1:
The metal core is extracted or removed from the final assembly after the wax model is created. By removing only the necessary portion of the core, the invention avoids forming orifices in the inner shroud that would require plugging, thereby eliminating additional manufacturing steps and costs while maintaining shape precision during the molding process.
Solution Approach 2:
The core is designed with specific positioning features that allow it to be preliminarily positioned during wax injection to ensure precision, then subsequently removed before final assembly. This preliminary action maintains manufacturing precision during the critical molding phase while avoiding the need for costly plugging operations in the final product.
3Manufacturing precision
If the core is firmly mounted to minimize deformation, then manufacturing precision is maintained, but brazed parts are required to plug orifices reducing mechanical strength and assembly life
Solution Approach 1:
The metal core is extracted from the assembly after serving its purpose during wax injection. By removing the core, no orifices remain in the inner shroud that would require plugging with brazed parts. This extraction eliminates the need for weakening brazed joints while maintaining the precision achieved during the molding process.
Solution Approach 2:
The metal core is designed as a disposable tool used only during the wax injection phase. After completing its function of defining the cavity shape and supporting wax injection pressure, the core is removed and discarded. This disposable approach avoids the need for permanent brazed plugging operations that would weaken the final assembly.
4Manufacturing precision
If core deformation is minimized through proper mounting, then manufacturing precision is maintained, but the process becomes more complex requiring both metal and ceramic core portions
Solution Approach 1:
The core is segmented into functional portions (metal and ceramic) that can be manufactured separately using optimized processes for each material, then assembled into a complete core structure. This segmentation manages complexity by allowing each segment to be designed and manufactured independently for its specific function.
Solution Approach 2:
The composite core structure serves multiple functions: the metal portion provides structural support and pressure resistance, while the ceramic portion provides thermal resistance. This multi-functionality consolidates the requirements of both materials into a single integrated component, managing overall system complexity despite the increased material diversity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces manufacturing costs, enhances the mechanical strength and service life of bladed annular assemblies by eliminating the need for plugging orifices and minimizing core deformation, while maintaining thermal resistance through the use of ceramic cores.
Implementation Method 1
the aforementioned core being made of metal and being positioned in such a way that its radially inner end is housed in the portion of the mold defining the blade comprising the cavity, at a distance from the radially inner end of this portion of the mold
Implementation Method 2
This core 22 is made of ceramic so that it has sufficient heat resistance to withstand the high temperatures inherent in the casting of the aforementioned metal alloy
Implementation Method 3
the core is removed, generally by a chemical method
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The invention relates to a method for manufacturing a wax pattern (50) for a bladed turbine engine stator assembly (10), including consecutively: placing a core (40) inside a mold, said core intended for forming the impression of a cavity for a blade (18) of said assembly; injecting wax into said mold; and removing the wax pattern (50) provided with said core (40) from the mold, characterized in that said core (40) is made of metal and is positioned such that the radially inner end thereof (46) is housed in the portion (58) of the mold defining the blade (18) comprising said cavity, remote from the radially inner end (52) of said mold portion.