Contact Matrix Grounding for EDM of CMC Ceramic Components

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Solution Overview

Problem

Ceramic Matrix Composite (CMC) components in gas turbine engines face inefficient electrical grounding during Electrical Discharge Machining (EDM) due to limited contact points and high electrical resistance, leading to issues like pitting and arcing.

Innovation Solution

A contact matrix with an electrically conductive backbone and compliant, pressurized contacts is used to engage the CMC component, providing multiple pathways for efficient electrical conduction to a grounding structure, reducing resistance and preventing overheating.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a rigid metallic grounding structure is used to electrically ground the CMC component, then the grounding structure provides structural support, but the limited contact points and high electrical resistance cause point overheating and arcing

Engineering Contradiction:

Improveelectrical grounding effectivenessVSAvoidpoint overheating and arcing

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The grounding structure is segmented into multiple independent contact elements (grounding pins) distributed across the fixture surface. Each pin provides a separate electrical conduction pathway to the CMC component, transforming a single-point contact problem into a multi-point contact system. This segmentation increases the total contact area and distributes the electrical current across multiple pathways, reducing current density and preventing point overheating and arcing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The grounding contacts are designed with locally optimized properties - the contact tips are made of electrically conductive material with high electrical conductivity to reduce contact resistance. Each contact point is locally engineered to provide optimal electrical conduction to the CMC component surface, ensuring uniform current distribution across the workpiece surface and eliminating the harmful effects of high resistance at individual contact points.

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If a rigid metallic grounding structure is used, then the structure is simple to manufacture, but the surface irregularity between the rigid CMC component and rigid metallic structure limits the number of contact points

Engineering Contradiction:

Improvegrounding structure fabricationVSAvoidelectrical conduction quality

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The grounding structure transitions from a rigid, fixed-geometry fixture to a dynamic system where multiple independent contact pins can adapt their positions and orientations. The pins are arranged to accommodate surface irregularities of the CMC component, allowing the grounding structure to dynamically conform to the workpiece surface geometry. This dynamic adaptability ensures reliable electrical contact even when the CMC component has surface variations, while maintaining manufacturing simplicity through modular pin design.

Inventive Principle:

Principle #15Dynamics

3Ease of operation

If limited contact points are made between the CMC component and metallic grounding structure, then the rigid structures are easy to position, but the electrical resistance at contact points creates bottlenecks that obstruct electrical grounding

Engineering Contradiction:

Improvepositioning of grounding structureVSAvoidelectrical current flow

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The electrical conduction path is segmented into multiple parallel pathways through the use of multiple grounding pins. Instead of relying on a single contact point that creates a current bottleneck, the current is divided and flows through numerous parallel conduction channels. This segmentation of the electrical pathway reduces the effective resistance and eliminates current bottlenecks, ensuring reliable electrical grounding while maintaining ease of positioning through the modular pin array design.

Inventive Principle:

Principle #1Segmentation

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 solution enhances the electrical grounding of CMC components during EDM, reducing cycle times, minimizing scrap, and preventing tool electrode breakage by ensuring smooth current flow and reducing the risk of arcing.

Implementation Method 1

compliant and pressurized electrically conductive contacts extending outward from the electrically conductive backbone... in electrical conduction to the ceramic component... in electrical conduction to a grounding structure

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

compliant and pressurized electrically conductive contacts... biased into engagement with the ceramic component

Methodology Applied

Scientific EffectPressure: Pressure Increase

Data Source

PatentUS12186820B2Contact matrix for grounding a ceramic component during electrical discharge machining

Publication Date: 2025.01.07 GENERAL ELECTRIC CO

AI summary

Methods of Electrical Discharge Machining (EDM) ceramic components are provided. In one aspect, a method includes electrical discharge machining a ceramic component, such as a Ceramic Matrix Composite (CMC) component. The ceramic component is electrical discharge machined while a contact matrix is positioned so that electrically conductive compliant and pressurized contacts of the contact matrix engage the ceramic component and so that an electrically conductive member of the contact matrix is in electrical conduction to a grounding structure.