Flexible Cathode Tube for ECM of Additive Manufactured Parts

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Solution Overview

Problem

Existing methods for improving surface roughness of internal surfaces of additively manufactured metal parts, particularly those with bends or restricted geometries, are inefficient due to the limitations of traditional electrochemical machining (ECM) which requires a cathode insertion throughout the article, restricting its use to open, straight geometries.

Innovation Solution

A flexible metallic cathode tube is inserted into the article to conform to its geometry, allowing for electrochemical machining by applying a voltage across the cathode tube and the article, with an electrolyte fluid circulating to efficiently reduce surface roughness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If traditional ECM is used with a rigid cathode, then surface roughness can be improved on simple geometries, but the method cannot be applied to articles with bends or restricted geometries

Engineering Contradiction:

Improvesurface roughnessVSAvoidapplicability to complex geometries

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The patent employs a flexible cathode constructed from thin-walled tubing that can bend and conform to the internal geometry of the workpiece. This flexible cathode allows ECM to be applied to articles with bends, curves, and restricted geometries that were previously inaccessible to traditional rigid cathode ECM processes

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The cathode is designed with dynamic flexibility rather than rigidity, allowing it to adapt its shape during the ECM process. The flexible cathode can be inserted through complex geometries and maintained in position to achieve uniform surface finishing on internal surfaces of bent or curved articles

Inventive Principle:

Principle #15Dynamics

2Manufacturing precision

If post-processing methods like sand blasting or machining are used, then surface roughness can be improved, but the process becomes time consuming and ineffective for internal surfaces

Engineering Contradiction:

Improvesurface roughnessVSAvoidpost-processing time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent replaces mechanical post-processing methods (sand blasting, machining) with an electrochemical process. The ECM method uses electrical current and electrolyte to remove material chemically, achieving superior surface roughness on internal surfaces without the time-consuming mechanical operations required by traditional methods

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If a rigid cathode is used in ECM, then the process works for straight geometries, but it cannot ensure sufficient ECM action on bent or curved surfaces

Engineering Contradiction:

ImproveECM process effectivenessVSAvoidgeometric flexibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The flexible cathode construction allows the ECM process to maintain reliability on bent and curved surfaces by conforming to the workpiece geometry. The thin-walled flexible tubing can be inserted through complex pathways and positioned against internal surfaces to ensure adequate ECM action where rigid cathodes would fail

Inventive Principle:

Principle #30Flexible shells and thin films

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 enables effective polishing of internal surfaces with bends and curves, achieving the desired surface roughness of less than 125 micro-inches, overcoming the limitations of traditional ECM on complex geometries.

Implementation Method 1

introducing an electrolyte fluid into the metallic cathode tube and the interior surface of the article and electrochemical machining the metallic article by applying a voltage across the cathode tube and the metallic article

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Implementation Method 2

electrochemical machining the metallic article by applying a voltage across the cathode tube and the metallic article, the metallic article functioning as an anode

Methodology Applied

Scientific EffectElectrochemical machining: Electrolysis

Data Source

PatentUS11193216B2Methods and systems for electrochemical machining of articles formed by additive manufacturing

Publication Date: 2021.12.07 HONEYWELL INTERNATIONAL INC

AI summary

A method for electrochemical machining of a metallic article formed by additive manufacturing includes obtaining or producing the metallic article. The metallic article includes an interior surface and a geometry. The method further includes inserting a flexible, metallic cathode tube into the article. The metallic cathode is spaced apart from the interior surface of the article, and the metallic cathode tube is inserted so as to conform to the geometry of the article. Still further, the method includes introducing an electrolyte fluid into the metallic cathode tube and the interior surface of the article and electrochemical machining the metallic article by applying a voltage across the cathode tube and the metallic article, the metallic article functioning as an anode.