Nacelle Lip Skin Sector Redraw Forming for Edge Stability
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Solution Overview
Problem
The existing methods for forming lip skin sectors of aircraft nacelles are complex, costly, and prone to material deformation due to the need for multi-stage processes and intermediate heat treatments, which are unsuitable for extended trailing edges and can result in turbulence and drag issues.
Innovation Solution
A two-stage forming process using an apparatus with a retaining means and cooperating forming means that create a continuous clamping boundary to uniformly draw the blank, preventing warping and deformation, and an adjustable punch system with a die plate and re-draw ring sector to form the sector from the leading edge to the inlet edge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If multi-stage deep drawing or spin forming processes are used to form lip skin sectors, then complex three dimensional compound curvature shapes can be achieved, but the process becomes complex and costly requiring intermediate heat treatments and complex tooling
Solution Approach 1:
The forming process is divided into two distinct stages: a first draw forming stage that creates a preliminary shape, and a second redraw forming stage that achieves the final complex geometry. This segmentation allows each stage to be optimized independently, simplifying the overall process while achieving the required complex curvature shapes
Solution Approach 2:
The first draw forming stage performs preliminary shaping of the blank before the final redraw forming stage. This preliminary action prepares the material in an optimal state for the subsequent forming operation, enabling the achievement of complex three-dimensional shapes with reduced process complexity
2Ease of manufacture
If only leading edges and trailing edges of the blank sector are gripped in prior art forming processes, then the forming process is simpler, but warping along the edges occurs requiring manual finishing work
Solution Approach 1:
The retaining means applies localized clamping forces at specific regions of the blank, particularly at the leading and trailing edges, to prevent warping in these critical areas during forming. This localized quality control ensures edge stability without requiring complex overall process modifications
Solution Approach 2:
The retaining means is positioned and configured to counteract potential warping forces before they can occur during the forming process. By applying preliminary restraining forces at the edges, the system prevents deformation that would otherwise require manual finishing corrections
3Reliability
If extended trailing edges are used to increase laminar flow over the outer surface, then aerodynamic performance is improved, but known deep drawing processes become unsuitable for manufacture
Solution Approach 1:
The forming process uses dynamic adjusting mechanisms that allow the forming parameters to adapt during the drawing operation. This enables the process to accommodate the extended trailing edge geometry that would be impossible with static deep drawing processes, while maintaining manufacturing feasibility
Solution Approach 2:
The process changes key forming parameters including the configuration of the retaining means and the geometry of the punch to accommodate extended trailing edges. These parameter changes enable the formation of aerodynamically optimized shapes with extended laminar flow regions that cannot be achieved by conventional deep drawing
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
This method reduces material deformation, minimizes manual finishing work, and enhances the aerodynamic performance by extending the outer trailing edge, promoting laminar flow and reducing drag and noise interference.
Implementation Method 1
radially moving the retaining means and/or the punch so that a redraw ring sector aligns with an arcuate channel of a punch and actuating the redraw ring sector so that it moves axially into the arcuate channel for engaging the blank and drawing the blank over the punch forming the sector
Data Source
Figure 1
Figure 2~5
Figure 5A~5E
AI summary
A method of forming a sector of an annular component such as an inlet cowl/lip skin of a nacelle for an aircraft engine. The method comprising the steps of clamping at least part of a blank along a clamping boundary in a retaining arrangement so as to leave a portion of the blank exposed within the clamping boundary. Moving a punch and/or retaining arrangement radially so that the punch comes in to contact with the exposed portion of the blank and through the main body of the exposed blank thereby drawing the blank onto an external surface of the punch forming the sector from the leading edge to the trailing edge. Activating cooperating forming arrangement for engaging the blank and drawing the blank over the punch forming the sector of the inlet cowl from the leading edge to the inlet edge, the method comprising using a second draw forming tooling arrangement for the cooperating forming arrangement.