Trimming Composite Stiffener Ends With Guide Frame
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Solution Overview
Problem
Current methods for trimming the ends of hat-shaped stiffeners on composite skin panels are inefficient, lacking control over shape and size, and risk damaging the underlying skin plies, requiring substantial time and labor.
Innovation Solution
An expandable guide frame with a rotating abrasive drum is used to straddle and clamp the stiffener, allowing precise trimming of the ends without damaging the underlying skin, featuring a mechanism for adjusting the angle and limiting the drum's movement to prevent skin damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hand grinding or cutting is used to trim stiffener ends, then trimming can be performed, but control of shape and size is poor and underlying skin may be damaged
Solution Approach 1:
A guide frame acts as an intermediary between the trimming operation and the stiffener, providing precise positioning and depth control. The guide frame includes a base plate that rests on the skin surface and vertical guides that constrain the trimming tool, preventing direct contact between the tool and skin while maintaining accurate trimming geometry.
Solution Approach 2:
The patent replaces the uncontrolled hand grinding/cutting mechanism with a guided mechanical system. The guide frame transforms the freehand operation into a constrained mechanical process where the trimming tool follows predetermined paths and depths, ensuring consistent shape and size control while preventing skin damage through mechanical depth limitation.
2Productivity
If hand grinding or cutting is used to trim stiffener ends, then trimming can be performed, but substantial time and labor are consumed
Solution Approach 1:
The guide frame is designed to be self-positioning on the stiffener, with features that automatically align and secure the frame without requiring precise manual adjustment. Once positioned, the frame guides the trimming tool through the entire operation, reducing the operator's time and effort while increasing productivity.
3Strength
If stiffeners terminate within part boundary rather than at skin edge, then structural requirements are met, but trimming becomes more difficult and risky
Solution Approach 1:
The guide frame serves as an intermediary that bridges the gap between the stiffener termination point within the skin boundary and the trimming operation. It provides a stable reference system that accommodates internal terminations while maintaining trimming precision, making the operation easier and safer compared to direct trimming without guidance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables rapid, uniform trimming of stiffener ends with precise control, reducing labor and minimizing risk to the underlying skin, while maintaining structural integrity.
Implementation Method 1
The rotatably supported opposite ends of a central shaft of a rotating abrasive drum are slid along respective ones of the guide faces of the frame such that the drum grinds, or abrades away, the stiffener
Data Source
AI summary
A tool for trimming the ends of stiffeners on aircraft composite skin panels accurately, rapidly and without damaging the underlying skins includes an expandable guide frame adapted to straddle and clamp to the stiffener at a selected longitudinal position thereon. The frame includes a pair of planar guide faces disposed on opposite sides of the stiffener and lying in a common plane transverse thereto. The rotatably supported opposite ends of a rotating abrasive drum are slid along respective ones of the guide faces such that the drum grinds away the stiffener in a plane parallel to the plane of the guide faces and thereby forms a trimmed end on the stiffener. The frame includes mechanisms for adjusting the angular inclination of the plane of the guide faces relative to the plane of the composite skin, and for preventing the grinding mechanism from cutting into the composite skin.