Wire-EDM Guide Path Compensation for Curved Aperture Accuracy

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Solution Overview

Problem

Current wire electrical discharge machining (wire-EDM) methods for machining rotor disk components, such as those in aircraft engines, face inefficiencies due to the 'bicycle effect' where the EDM wire path diverges from the guide path, especially during curved cuts, leading to inaccuracies and increased cycle times.

Innovation Solution

The method involves modeling the guide path to accommodate the displacement of the EDM wire from the reference line, maintaining a constant wire speed, and adjusting the guide path to ensure the wire path matches the predetermined cutting path, thereby mitigating the bicycle effect and improving accuracy and efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the guide path is used to control the EDM wire during cutting, then the wire path diverges from the guide path due to the bicycle effect, but maintaining a straight guide path results in machining inaccuracies for curved geometries

Engineering Contradiction:
Improveaperture geometry accuracyVSAvoidguide path complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The guide path is pre-modeled to anticipate and compensate for the bicycle effect displacement. By calculating the offset between the guide path and the actual wire path in advance, the system pre-adjusts the guide path geometry so that the wire naturally follows the desired aperture contour despite the displacement effect.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The guide path parameters are modified to account for the bicycle effect. The system changes the geometric parameters of the guide path (such as curvature radius and position) to compensate for the wire displacement, ensuring that the actual wire path matches the predetermined cutting path for accurate aperture geometry.

Inventive Principle:
Principle #35Parameter changes

2Manufacturing precision

If the wire speed is reduced to improve machining accuracy, then the manufacturing precision improves, but the productivity decreases

Engineering Contradiction:
Improvecutting path accuracyVSAvoidcycle time
Core Design Contradiction:
Manufacturing precisionVSProductivity

Solution Approach 1:

The system uses feedback from measured wire paths to continuously refine the guide path model. By comparing actual wire paths with predetermined cutting paths and adjusting the guide path accordingly, the system achieves high precision without requiring reduced wire speeds, thus maintaining productivity.

Inventive Principle:
Principle #23Feedback

3Manufacturing precision

If the guide path is adjusted to accommodate wire displacement, then the manufacturing precision improves, but the device complexity increases due to path modeling requirements

Engineering Contradiction:
Improvewire path alignmentVSAvoidguide path modeling
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The system performs self-adjustment by automatically modeling and refining the guide path based on measured wire paths. The control system autonomously calculates the necessary guide path modifications to compensate for the bicycle effect, eliminating the need for complex manual calibration procedures.

Inventive Principle:
Principle #25Self-service

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 approach allows for more precise and faster machining of complex geometries like firtree slots in rotor disks, reducing cycle times and ensuring the machined apertures match the design geometry within acceptable tolerances.

Implementation Method 1

An aperture is machined into the workpiece using an electrical discharge machining wire

Methodology Applied
Scientific EffectElectrical discharge machining: Electrical Discharge Machining

Data Source

PatentEP4400242A1Wire electrical discharge machining
Publication Date: 2024.07.17 PRATT & WHITNEY CANADA CORP
  • EP4400242A1 patent drawingFigure 1
  • EP4400242A1 patent drawingFigure 2~3
  • EP4400242A1 patent drawingFigure 4A

AI summary

A method is provided for manufacturing a component. During this method, a workpiece (54) is provided. An aperture is machined into the workpiece (54) using an electrical discharge machining wire (62) supported by a guide (60A, 60B). The machining of the aperture includes moving the guide (60A, 60B) along a guide path (90) where the electrical discharge machining wire (62) cuts the workpiece (54) along a wire path (94) that is different than the guide path (90). A speed of the electrical discharge machining wire (62) is maintained during the cutting of the workpiece (54) along the wire path (94).