Investment Casting Core with Bridge for Cooling Passage Stability
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Solution Overview
Problem
Current investment casting methods face challenges in achieving precise positioning and stability of internal cooling passages in components, particularly in gas turbine engines, due to shrinkage, warping, and mechanical stresses, which result in unpredictable cooling properties and increased wall thickness.
Innovation Solution
A core structure for investment casting with a tortuous path and a core bridge comprising pillars and a bridge portion that extends between the pillars, allowing for more accurate placement of cooling passages and improved stability, reducing the need for additional cooling paths and enhancing predictability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If cooling passages are provided using traditional investment casting methods, then internal cooling passages can be formed in components, but the passages suffer from shrinkage, warping, and mechanical stresses that reduce positioning precision and stability
Solution Approach 1:
The core is divided into multiple sections that are separately formed and then assembled together using core ties. This segmentation allows each section to be manufactured with tighter tolerances and reduces the cumulative shrinkage and warping effects that would occur in a single large core. The core ties provide stable mechanical connection points that maintain precise positioning of the cooling passages throughout the casting process.
Solution Approach 2:
The invention changes the material parameters and structural parameters of the core by using a multi-section design with specific core tie configurations. The core ties are designed with specific dimensions and attachment methods that compensate for thermal expansion and contraction during the casting process, maintaining the positional stability of the cooling passages despite temperature and pressure changes.
2Weight of moving object
If wall thickness is reduced to improve component performance, then cooling efficiency may be improved, but the stability and positioning accuracy of internal passages becomes more difficult to maintain
Solution Approach 1:
By segmenting the core into multiple sections connected by core ties, the invention enables precise positioning of cooling passages even when the component wall thickness is reduced. The segmented design allows for better control of each core section's position and orientation, maintaining passage accuracy independent of the overall component thickness.
Solution Approach 2:
The invention replaces reliance on purely mechanical core strength with a system of core ties that provide mechanical interconnection and positioning stability. The core ties act as mechanical fixtures that hold the core sections in precise positions relative to each other, enabling thin-walled components to maintain passage accuracy without requiring excessively thick walls for structural support.
3Reliability
If core sections are assembled using core ties, then structural stability can be improved, but additional cooling paths are created that may short circuit the cooling circuit
Solution Approach 1:
The invention extracts or removes the harmful cooling paths created by core ties by positioning the core ties such that they do not create continuous cooling channels. The core ties are designed and positioned to provide structural stability while minimizing or eliminating their role as cooling conduits, thereby taking out the harmful effect of short-circuiting the intended cooling circuit paths.
Solution Approach 2:
The invention applies local quality by making the core ties have different properties in different regions - they provide mechanical connection and stability where needed, but are designed to minimize thermal conduction that would short-circuit the cooling circuit. The core ties may have varying cross-sections, materials, or positions that locally optimize both structural and thermal performance.
Data Source
AI summary
There is described a core for an investment casting process, comprising: a core passage which extends between a first point and a second point along a tortuous path having length L, wherein the first point and second point are separated by a direct line of sight distance, S, wherein L is greater than S; and, a core bridge which extends between the first and second points away from the core passage.