Planetary EDM Electrode Assembly for Faster Underwater Hole Machining

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Solution Overview

Problem

Existing EDM technologies face challenges in maintaining electrode resilience and efficiency, particularly in nuclear reactor environments where quick and deep material removal is required, leading to increased wear and frequent electrode replacements.

Innovation Solution

The use of rotatable planetary electrodes with multiple cylindrical sub-electrodes that can rotate and revolve about a shared axis, combined with independent rotational and vertical movement control, increases the electrode-surface interface and reduces wear by distributing material removal more evenly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a single rotating electrode is used in traditional EDM, then the electrode structure is simple and easy to operate, but the material removal rate is slow and electrode wear is concentrated

Engineering Contradiction:

Improvematerial removal rateVSAvoidelectrode structure complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The single electrode is divided into multiple sub-electrodes (at least two) arranged in a circular pattern around a central axis. Each sub-electrode can be independently positioned and controlled, allowing distributed material removal across the workpiece surface, thereby increasing the overall material removal rate while distributing wear across multiple electrodes.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The electrode configuration transitions from a single-point contact to a multi-point circular arrangement around a central axis. This spatial dimensionality change allows simultaneous engagement of multiple sub-electrodes with the workpiece surface, dramatically increasing material removal efficiency while maintaining rotational symmetry for even wear distribution.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Productivity

If electrode segments are rotated individually across the surface, then the electrode-surface contact is maintained, but the material removal is uneven and electrode replacement is frequent

Engineering Contradiction:

Improvematerial removal efficiencyVSAvoidelectrode wear distribution

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

Multiple sub-electrodes are combined into a single integrated electrode assembly that rotates as one unit about a central axis. This merging ensures synchronized rotation and positioning of all sub-electrodes, creating uniform electrode-surface contact patterns across the workpiece. The combined action of multiple sub-electrodes produces more even material removal and distributes wear uniformly across all sub-electrodes, reducing the need for frequent replacements.

Inventive Principle:

Principle #5Merging (Combining)

3Adaptability or versatility

If the electrode is moved transversely underwater to machine the surface, then the machining can be performed in nuclear reactor environments, but the positioning precision and machining accuracy are reduced

Engineering Contradiction:

Improveunderwater machining capabilityVSAvoidspotface machining accuracy

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The electrode assembly incorporates rotational movement about a central axis and adjustable positioning along the axis. This dynamic configuration allows the sub-electrodes to be precisely positioned relative to the workpiece surface while maintaining underwater operation. The rotational symmetry and controlled movement patterns compensate for the challenges of underwater machining, maintaining adequate positioning precision and machining accuracy in nuclear reactor environments.

Inventive Principle:

Principle #15Dynamics

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 enhances material removal efficiency by up to 2.3 times faster than traditional methods, potentially reducing electrode changes by half and minimizing downtime during maintenance operations.

Implementation Method 1

Electrical discharge machining assemblies and methods for using the same

Methodology Applied

Scientific EffectElectrical discharge machining: Electrical Discharge Machining

Data Source

PatentUS11273508B2Electrical discharge machining assemblies and methods for using the same

Publication Date: 2022.03.15 GE HITACHI NUCLEAR ENERGY AMERICAS LLC

AI summary

EDM assemblies mount on a machining surface and discharge rotating sub-electrodes against the surface. The sub-electrodes can also revolve about another shared axis while discharging. Rotation and revolution may be achieved with planetary gears fixed with the sub-electrodes and meshing with a stationary sun gear. Several sub-electrodes can be used in a single assembly. Downward movement of the sub-electrodes from a central shaft on the mount allows several inches of the surface to be machined. Assemblies are usable in a nuclear reactor during a maintenance period to machine a hole for a replacement manway cover underwater in the flooded reactor. The differing rotational movements and vertical movement can be independently controlled with separate motors in the assembly. Power and controls may be provided remotely through an underwater connection.