Adaptive Machining of Thin-Walled Castings for Wall Thickness Precision
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Solution Overview
Problem
Current lost-wax investment casting processes for aerospace components, such as turbine airfoils, are limited by tolerance stacks, core position, core thickness, and filling capabilities, resulting in thicker wax walls than desired, which can lead to suboptimal part design and structural issues.
Innovation Solution
A method involving adaptive machining, where tools engage without rigidly-programmed toolpaths to adjust actual casting dimensions to match desired dimensions, using cutting tools to reduce excess thickness and additive manufacturing to increase insufficient areas, based on three-dimensional scans and adaptive machining rules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional lost-wax investment casting processes are used, then manufacturing simplicity is maintained, but manufacturing precision deteriorates due to tolerance stacks, core position variations, and filling capability limitations resulting in thicker than desired wall thicknesses
Solution Approach 1:
The patent applies preliminary action by intentionally designing the wax tool and core assembly to produce castings with predetermined, controlled deviations from nominal dimensions. The wax tool incorporates built-in compensation features that anticipate and pre-correct for expected variations in core position and filling capability, so that the initial casting already contains the necessary material allowance for subsequent adaptive machining operations.
Solution Approach 2:
The patent implements feedback through a closed-loop adaptive machining system that uses three-dimensional scanning to measure actual casting dimensions, compares them against target dimensions, and dynamically adjusts machining parameters in real-time. This feedback mechanism enables the system to automatically compensate for variations in core position, wall thickness, and geometric deviations, achieving precise final dimensions despite initial casting variations.
2Strength
If thicker wax walls are produced to accommodate manufacturing limitations, then structural rigidity during casting is improved, but weight increases and heat transfer performance deteriorates
Solution Approach 1:
The patent applies local quality by enabling different wall thicknesses in different regions of the casting through adaptive machining. The system selectively removes material from areas that are too thick while preserving or adding material to areas that require thickness for structural integrity. This allows the final component to have non-uniform wall thickness optimized for both structural rigidity and weight reduction, with thicker walls where strength is required and thinner walls where weight reduction and heat transfer improvement are priorities.
3Reliability
If thicker wax walls are produced to ensure structural rigidity during casting, then casting process reliability is improved, but aerodynamic performance deteriorates due to increased part weight and altered flow characteristics
Solution Approach 1:
The patent applies preliminary action by intentionally designing the wax tool and core assembly to produce castings with predetermined, controlled deviations from nominal dimensions. The wax tool incorporates built-in compensation features that anticipate and pre-correct for expected variations in core position and filling capability, so that the initial casting already contains the necessary material allowance for subsequent adaptive machining operations.
Solution Approach 2:
The patent applies local quality by enabling different wall thicknesses in different regions of the casting through adaptive machining. The system selectively removes material from areas that are too thick while preserving or adding material to areas that require thickness for structural integrity. This allows the final component to have non-uniform wall thickness optimized for both structural rigidity and weight reduction, with thicker walls where strength is required and thinner walls where weight reduction and heat transfer improvement are priorities.
4Manufacturing precision
If adaptive machining with non-rigidly-programmed toolpaths is used, then manufacturing precision is improved, but productivity decreases due to additional scanning and processing steps
Solution Approach 1:
The patent applies partial or excessive action by implementing selective adaptive machining rather than machining all castings to the same level of precision. The system uses three-dimensional scanning to identify and prioritize critical features and areas requiring tight tolerance control, applying adaptive machining only to those specific regions. Non-critical areas are processed with standard machining operations, reducing overall processing time while maintaining dimensional accuracy where it matters most.
Data Source
AI summary
A method of manufacturing a casting is provided and includes establishing desired dimensions of a nominal casting, executing a casting process to produce multiple actual castings with each of the multiple actual castings having respective dimensions that differ from each other and from the desired dimensions of the nominal casting and engaging one or more tools to adaptively machine, without rigidly-programmed toolpaths, each of the multiple actual castings to reduce the respective differences between the actual dimensions of each of the multiple actual castings and the desired dimensions.