Aircraft Skin Panel Free-State Machining for Nominal Thickness
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Solution Overview
Problem
Current manufacturing methods for aircraft skin panels are inefficient, leading to increased costs, time-consuming machining setups, and non-nominal aerodynamic profiles due to variations and tolerances introduced by holding fixtures and machining processes.
Innovation Solution
A method involving a holding fixture that supports the panel assembly in a free state, allowing for scanning of the outer surface contour, development of a numerically controlled machining program, and machining of sacrificial material at interface locations to achieve nominal thicknesses, thereby reducing the need for shimming and ensuring accurate aerodynamic profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional holding fixtures are used to support skin panels during machining, then the panels can be held stable for machining operations, but tolerances and variations are introduced resulting in gaps that require shimming
Solution Approach 1:
The patent removes the holding fixture entirely from the machining process. Instead of using a fixture to hold the panel during machining, the panel is supported in its natural free-state position, eliminating the source of tolerance introduction while maintaining machining capability through direct support on the mandrel
Solution Approach 2:
The patent introduces a compensating mechanism that measures the actual panel geometry and calculates precise cutter paths to compensate for any variations. This intermediary measurement and calculation system replaces the need for rigid fixture-based tolerance control
2Manufacturing precision
If skin panels are machined after ladder assembly completion, then accurate interface fit can be achieved, but significant holding costs are incurred due to waiting time
Solution Approach 1:
The patent performs machining operations on skin panels before they are assembled to the ladder structure. By preparing the panels in advance while they are still accessible and supported independently, the process eliminates waiting time while maintaining interface accuracy through the free-state machining approach
3Manufacturing precision
If multiple machining operations are performed on skin panels, then accurate interface locations are achieved, but time-consuming and costly machining setups are required each time
Solution Approach 1:
The patent combines multiple machining operations into a single continuous process. By supporting the panel in its free state and using compensating cutter paths, all necessary machining can be performed in one setup without repeated fixture changes or repositioning, dramatically improving productivity while maintaining accuracy
4Stability of the object's composition
If holding fixtures are used to support panel assembly, then the assembly can be stabilized during machining, but the geometric shape deviates from the as-designed nominal state
Solution Approach 1:
The patent removes the holding fixture that causes geometric distortion and instead supports the panel assembly directly on the mandrel in its natural free state. This eliminates the shape deviation while maintaining stability through the inherent support structure
Solution Approach 2:
The patent implements a feedback mechanism where the actual free-state geometry of the panel is measured and used to generate compensating cutter paths. This feedback loop allows the system to adapt to the natural geometric variations and achieve accurate machining without rigid fixture constraints
Data Source
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AI summary
A method of manufacturing a panel assembly (266) includes supporting the panel assembly (266) in a free state (280) using a holding fixture (350). The panel assembly (266) has a skin panel (300), and sacrificial material (322) coupled to a skin panel inner surface (302). The method includes acquiring a free state outer surface contour (372) of the panel assembly (266) by scanning a skin panel outer surface (304) while the panel assembly (266) is supported by the holding fixture (350). The method also includes developing a numerically controlled (NC) machining program (388) having cutter paths (402) configured for machining the interface locations (320) to an inner surface contour (382) that reflects nominal thicknesses (306) of the panel assembly (266) based off of the free state outer surface contour (372). In addition, the method includes machining the sacrificial material (322) at the interface locations (320) by moving a cutter (400) along the cutter paths (402) while the panel assembly (266) is supported by the holding fixture (350).