Skin Panel Assembly Machining for Nominal Thickness Fit
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for manufacturing aircraft skin panels are inefficient, leading to costly machining setups, tolerances issues, and non-nominal aerodynamic profiles due to the use of holding fixtures and machining processes that introduce variations and require shimming, resulting in increased production time and costs.
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 and development of numerically controlled machining programs to machine sacrificial material at interface locations, ensuring nominal thicknesses and reducing the need for shimming by reversing springback effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a holding fixture is used to support the skin panel during machining, then the panel can be supported during processing, but the fixture introduces tolerances and variations that result in gaps between the skin panel and ladder assembly
Solution Approach 1:
The panel is pre-flattened using a flattening fixture with adjustable rollers that apply controlled pressure to the panel surface before machining. This preliminary action corrects springback and distortion, establishing a flat reference surface that eliminates the need for shimming during assembly and reduces gaps at interface locations
Solution Approach 2:
A reference surface is introduced as an intermediary element between the holding fixture and the panel. The reference surface provides a stable, precise datum that the holding fixture can reference, ensuring the panel is held in the correct position and orientation during machining without introducing tolerances or variations
2Manufacturing precision
If the skin panel is machined after the ladder assembly is completed, then the panel can be processed to fit, but significant holding costs are incurred while the panel waits to be machined
Solution Approach 1:
The skin panel is machined to final dimensions before assembly to the ladder structure. By preparing the panel in advance with precise machining operations, the need for post-assembly adjustments and shimming is eliminated, reducing both holding costs and overall production time
Solution Approach 2:
The manufacturing process is divided into independent stages where the skin panel can be manufactured and machined separately from the ladder assembly. This segmentation allows parallel production of panel and ladder components, reducing total production cycle time while maintaining interface fit accuracy through precise pre-machining
3Manufacturing precision
If multiple machining operations are performed on the skin panel, then the interface locations can be prepared for coupling, but each operation requires a time-consuming and costly machining setup
Solution Approach 1:
A single multi-functional holding fixture is designed to perform multiple machining operations in one setup. The fixture incorporates various tooling provisions and positioning features that enable drilling, countersinking, and other interface preparations without requiring the panel to be removed and re-setup, significantly reducing total machining time while maintaining accuracy
Solution Approach 2:
Multiple machining operations are combined into one continuous process by keeping the panel in a single holding fixture position. The fixture is designed to accommodate different cutting tools and operations sequentially, merging what would otherwise be separate setup-intensive operations into one efficient workflow
4Adaptability or versatility
If the skin panel is re-indexed to the supporting structure each time it is moved, then the panel can be repositioned for different operations, but additional tolerances are introduced
Solution Approach 1:
The holding fixture is pre-configured with permanent reference surfaces and positioning features that establish a stable coordinate system before any operations begin. This preliminary setup eliminates the need for repeated re-indexing, as all subsequent operations reference the same fixed datum, preventing cumulative tolerance buildup while maintaining full repositioning capability for different operations
Data Source
AI summary
A method of manufacturing a panel assembly includes supporting the panel assembly in a free state using a holding fixture. The panel assembly has a skin panel, and sacrificial material coupled to a skin panel inner surface. The method includes acquiring a free state outer surface contour of the panel assembly by scanning a skin panel outer surface while the panel assembly is supported by the holding fixture. The method also includes developing a numerically controlled (NC) machining program having cutter paths configured for machining the interface locations to an inner surface contour that reflects nominal thicknesses of the panel assembly based off of the free state outer surface contour. In addition, the method includes machining the sacrificial material at the interface locations by moving a cutter along the cutter paths while the panel assembly is supported by the holding fixture.