Freight Door Bore Alignment via Stress-Free Pre-Drilling
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Solution Overview
Problem
Existing methods for manufacturing cargo doors in aircraft result in misaligned bores due to elastic deformation and stress-induced misalignment during the riveting process, leading to difficulties in inserting drive and safety shafts.
Innovation Solution
A method involving pre-drilling of hole patterns in separate body sections, followed by straightening and stress-free positioning of the component, allowing precise alignment and final drilling without deformation, which simplifies the drilling process and extends tool life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the stiffening structure is riveted to the skin panel, then the cargo door gains structural strength and rigidity, but elastic deformation occurs causing misalignment of bores
Solution Approach 1:
The patent applies preliminary action by pre-drilling the bores in the stiffeners before the riveting process. This ensures that the hole patterns are already aligned with high precision before any deformation occurs during subsequent assembly operations. The pre-drilled holes are then used as reference features for positioning the skin panel and stiffening structure, maintaining bore alignment even after structural assembly.
2Ease of manufacture
If the cargo door is assembled and then drilled, then the structural assembly is complete, but stress-induced deformation causes bore misalignment
Solution Approach 1:
The patent performs the drilling operation before final structural assembly is completed. Specifically, the bores are drilled in the stiffeners while they are still in a stress-free, pre-assembly state. This preliminary drilling avoids the problem of drilling after assembly when stress-induced deformations would cause misalignment. The drilled components are then assembled using the pre-drilled holes as alignment references.
Solution Approach 2:
The manufacturing process is segmented into distinct phases: first drilling the bores in separate stiffener components, then assembling the stiffening structure to the skin panel, and finally assembling the complete cargo door. This segmentation allows each component to be prepared in a stress-free state before assembly, preventing cumulative deformation effects that would occur if drilling were performed on the fully assembled structure.
3Loss of substance
If pilot holes are made with small final diameters, then material removal is minimized, but additional drilling operations are required
Solution Approach 1:
The patent uses pilot holes with small diameters as a preliminary action to establish precise hole locations and alignment before final drilling. These pilot holes serve as reference features that guide the subsequent final drilling operation, ensuring that the larger diameter holes remain aligned with the pre-established pattern. This two-stage approach minimizes material removal in the preliminary stage while maintaining high precision for the final bore dimensions.
Data Source
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AI summary
The invention relates to a method for introducing bores (58) that are aligned in relation to each other into a body section (28) of a component (20) consisting of a plurality of individual bodies (28, 30), wherein the component (20) is joined, straightened, and mounted stress-free and the bores (58) are finish-drilled. The invention relates to a method for producing a freight door (20), which is straightened before the finish-drilling and transferred stress-free into the installation position thereof, and to such a freight door (20).