Adaptive Machining of Thin-Walled Castings for Tolerance Compensation
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Solution Overview
Problem
Existing lost-wax investment casting processes for manufacturing aerospace components like turbine airfoils are limited by tolerances such as tool stack, core, and core thickness, filling capabilities, and structural rigidity limitations, which result in thicker than optimal wax walls, leading to inefficiencies and limitations in achieving desired thin-walled designs.
Innovation Solution
Adaptive machining methods involving subtractive and additive operations, using cutting and additive manufacturing tools, to adjust actual casting dimensions to match desired dimensions by creating difference maps and employing adaptive machining rules based on three-dimensional scans and feature indices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If traditional lost-wax investment casting processes are used with rigid tolerance constraints, then manufacturing process stability is maintained, but wall thickness cannot be optimized to be thinner
Solution Approach 1:
The patent applies preliminary action by intentionally designing the wax pattern with thicker walls than the final desired thickness, and by pre-positioning cores with deliberate clearance. This allows the casting process to produce castings with excess material that can subsequently be removed through adaptive machining to achieve the target thin-walled geometry while maintaining process stability throughout manufacturing.
Solution Approach 2:
The patent implements parameter changes by transitioning from rigid fixed tolerances to adaptive tolerance management. The system uses 3D scanning and digital modeling to measure actual casting dimensions, then dynamically adjusts machining parameters and toolpaths to achieve target dimensions. This allows wall thickness to be optimized thinner while compensating for manufacturing variations through adaptive control rather than rigid constraints.
2Shape
If wax walls are made thinner to optimize part design, then aerodynamic performance is improved, but structural rigidity during shelling and filling deteriorates
Solution Approach 1:
The patent applies preliminary action by designing the wax pattern with thicker walls that provide structural rigidity during the casting process, then removing the excess material after casting through adaptive machining. This sequence allows the wax to maintain strength during shelling and filling operations while the final part achieves the optimized thin-walled aerodynamic profile.
Solution Approach 2:
The patent inverts the traditional approach by not attempting to cast the final thin-walled geometry directly. Instead, it casts a thicker-walled version and removes material afterward. This inversion allows the casting process to focus on creating a robust base structure while the finishing process achieves the thin-walled aerodynamic shape, resolving the conflict between structural rigidity and aerodynamic optimization.
3Reliability
If thicker wax walls are used to ensure structural rigidity, then deformation and breakage during shelling are reduced, but aerodynamic performance deteriorates
Solution Approach 1:
The patent uses preliminary action by creating a thicker-walled wax pattern that ensures process reliability during casting, then removing the excess material through adaptive machining to achieve the optimized aerodynamic shape. This two-stage approach allows each process to be optimized for its specific function: casting for reliability and machining for aerodynamic performance.
Solution Approach 2:
The patent segments the manufacturing process into distinct stages: casting with thicker walls for reliability, then adaptive machining for aerodynamic optimization. This segmentation allows the casting process to focus on creating a robust structure without concern for final aerodynamic shape, while the machining process separately optimizes the aerodynamic profile, resolving the trade-off between reliability and aerodynamic efficiency.
4Device complexity
If rigidly-programmed toolpaths are used for machining, then manufacturing process control is simplified, but adaptability to actual casting variations is reduced
Solution Approach 1:
The patent applies dynamics by transitioning from static rigidly-programmed toolpaths to dynamic adaptive toolpaths. The system uses 3D scanning to capture actual casting geometry, then dynamically generates and adjusts toolpaths based on measured deviations from nominal dimensions. This allows the machining process to adapt to each specific casting variation while maintaining systematic control through automated digital modeling and programming.
Solution Approach 2:
The patent implements feedback by using 3D scanning to measure actual casting dimensions, comparing them to nominal target dimensions, and using this information to generate adaptive machining toolpaths that compensate for variations. This closed-loop feedback system allows the process to maintain control while adapting to actual casting variations, resolving the contradiction between simplified control and adaptability.
Data Source
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AI summary
A method of manufacturing a casting is provided and includes establishing desired dimensions of a nominal casting (301), executing a casting process to produce multiple actual castings with each of the multiple actual castings having respective dimensions (302) 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.