Double Eccentric Positioning for Drilling Accuracy

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Solution Overview

Problem

Traditional methods for drilling coordination holes in large parts, such as those in aircraft or ship construction, face challenges including the need for precise measurements, inflexibility, and difficulty in accessing smaller or internal recesses, leading to inaccuracies and high costs due to the use of large numerically controlled machines and fixed tooling.

Innovation Solution

A double eccentric positioning apparatus using two equal offset eccentric bushings with miniature servo motors and precise gearing for accurate two-dimensional positioning, allowing flexible tooling to adapt to part features and improve positioning accuracy within a small envelope.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If large numerically controlled machines on massive foundations are used to drill coordination holes, then manufacturing precision is improved, but device complexity and cost increase

Engineering Contradiction:

Improvedrilling accuracyVSAvoidmachine complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The positioning function is segmented into multiple eccentric bushings (at least two) that can be independently adjusted. Each eccentric bushing provides positioning in a specific direction, and their combined adjustment achieves two-dimensional positioning without requiring a large complex machine

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The eccentric bushings are made adjustable rather than fixed, allowing the tool to dynamically adapt to different hole locations and part geometries. This replaces the static, heavy fixed tooling with a flexible, adjustable system

Inventive Principle:

Principle #15Dynamics

2Manufacturing precision

If large numerically controlled machines are used, then manufacturing precision is improved, but adaptability deteriorates

Engineering Contradiction:

Improvedrilling accuracyVSAvoidtool flexibility

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The tool incorporates adjustable eccentric bushings that can be repositioned to accommodate different hole locations, part sizes, and geometries. This dynamic adjustment capability provides both precision and adaptability, unlike fixed tooling

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The tool with multiple adjustable eccentric bushings can perform drilling operations on various part types and sizes using the same basic tool structure, making it a universal solution rather than requiring specialized tools for each application

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Manufacturing precision

If fixed tooling is used, then manufacturing precision is improved, but ease of operation deteriorates

Engineering Contradiction:

Improvedrilling accuracyVSAvoidtool accessibility

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

The adjustable eccentric bushings allow operators to easily reposition the tool for different hole locations without requiring complex setup procedures. The mechanical adjustment mechanism provides intuitive control while maintaining positioning accuracy

Inventive Principle:

Principle #15Dynamics

4Manufacturing precision

If large machines with large work space are used, then manufacturing precision is improved, but weight increases

Engineering Contradiction:

Improvedrilling accuracyVSAvoidmachine weight

Core Design Contradiction:

Manufacturing precisionVSWeight of stationary object

Solution Approach 1:

The positioning function is distributed across multiple lightweight eccentric bushings rather than requiring a single heavy machine structure. This segmentation allows precision positioning with significantly reduced weight

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces the heavy mechanical support structure of traditional machines with a lighter system based on geometric principles (eccentric bushing mechanics), achieving precision through design rather than mass

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

The apparatus enables precise and flexible tooling, reducing errors and costs by allowing accurate planar positioning of tools within a small envelope, making it a viable alternative to large monuments and fixed tooling, and can be scaled for various applications.

Implementation Method 1

two equal offset eccentric bushings with miniature servo motors and precise gearing for accurate two-dimensional positioning

Methodology Applied

Scientific EffectEccentric mechanism: Eccentric

Data Source

PatentUS10473201B2Double eccentric positioning apparatus

Publication Date: 2019.11.12 THE BOEING CO

AI summary

A double eccentric positioning apparatus uses two equal offset eccentric bushings to accurately position a tool (such as a drill bushing) in two dimensions. Miniature servo motors and precise gearing control the rotation of each eccentric bushing, which controls the direction of the offset vectors. The offset vectors are used to determine the final position of the drill bushing. The desired rotation angles can be mathematically calculated based on desired position. The inner eccentric bushing is located concentric to the offset of the outer eccentric bushing. This allows any position, within a radius of two times the eccentric offset, to be achieved. The use of worm gearing on the eccentric bushings prevents back-driving of the servo motors, due to the lead angle of the worm gears, and the friction between the worm wheel and worm gear.