Flexible Electrode Electropolishing for Complex Internal Passageways

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Solution Overview

Problem

Additive manufacturing produces components with rough internal surfaces in complex geometries that obstruct fluid flow and are difficult to finish using conventional methods like grinding or polishing, leading to performance issues.

Innovation Solution

A method of electropolishing internal passageways using a flexible electrode assembly with a shuttle and guide cable, where the electrode is moved within the passageway while electropolishing, and a controller selectively energizes electrode segments for localized polishing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional grinding or polishing with abrasive particles is used to finish internal passageways, then surface roughness is reduced, but abrasive particles accumulate at bends and narrow passages causing contamination

Engineering Contradiction:
Improvesurface finish qualityVSAvoidabrasive particle accumulation and contamination
Core Design Contradiction:
Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The patent replaces mechanical abrasion with an electrochemical process. The electropolishing method uses controlled oxidation and material dissolution through electrical current in an electrolyte solution, eliminating the need for abrasive particles that cause accumulation and contamination in complex passageways.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the fundamental mechanism from mechanical removal to electrochemical dissolution. By controlling electrical parameters (current density, voltage) and electrolyte composition, the process achieves uniform surface finishing without the harmful side effects of mechanical abrasion in complex geometries.

Inventive Principle:
Principle #35Parameter changes

2Ease of manufacture

If a rigid electrode is used for electropolishing, then the electrode structure is simple, but it cannot access complex and convoluted internal passageways

Engineering Contradiction:
Improveelectrode structural simplicityVSAvoidaccess to complex internal passageways
Core Design Contradiction:
Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent employs a flexible electrode that can bend and conform to complex internal geometries. The flexibility allows the electrode to navigate convoluted passageways while maintaining electrical contact, solving the limitation of rigid electrodes in accessing complex internal structures.

Inventive Principle:
Principle #30Flexible shells and thin films

Solution Approach 2:

The electrode transitions from a static rigid structure to a dynamic flexible element that can adapt its shape and position. This dynamic capability enables the electrode to follow the contours of complex passageways while performing electropolishing, combining structural simplicity with geometric adaptability.

Inventive Principle:
Principle #15Dynamics

3Ease of operation

If the electrode remains stationary during electropolishing, then the process is simple to control, but electrolyte flow stagnation occurs preventing uniform surface finish

Engineering Contradiction:
Improveprocess control simplicityVSAvoidsurface finish uniformity
Core Design Contradiction:
Ease of operationVSManufacturing precision

Solution Approach 1:

The patent introduces motion to the electrode during the electropolishing process. By moving the flexible electrode through the passageway, the system prevents electrolyte stagnation, ensures uniform material removal, and achieves consistent surface finish while maintaining manageable process control.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The continuous movement of the electrode ensures uninterrupted electrolyte flow and consistent electrochemical action throughout the passageway. This continuous action prevents stagnation zones and maintains uniform polishing conditions along the entire surface being treated.

Inventive Principle:
Principle #20Continuity of useful action

4Manufacturing precision

If the entire passageway is electropolished, then complete surface finishing is achieved, but processing time and resource consumption increase

Engineering Contradiction:
Improvecomplete surface finish coverageVSAvoidelectropolishing processing time
Core Design Contradiction:
Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent enables selective electropolishing of specific regions within the passageway. By controlling which electrode segments are active and positioning the electrode at specific locations, the process targets only the areas requiring surface finishing, reducing overall processing time while maintaining quality where needed.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The electrode is divided into multiple independently controllable segments. This segmentation allows selective activation of specific electrode portions to treat specific regions of the passageway, enabling efficient resource allocation and reduced processing time for comprehensive surface finishing.

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

Achieves a uniform surface finish in complex internal passageways, minimizing electrolyte flow stagnation and allowing efficient fluid flow, while enabling selective polishing of specific regions.

Implementation Method 1

electropolishing the passageway using the electrode while moving the electrode within the passageway

Methodology Applied
Scientific EffectElectropolishing: Electroplating

Implementation Method 2

causing fluid to flow through the passageway to transport the shuttle through the passageway from the inlet towards the outlet

Methodology Applied
Scientific EffectFluid flow transport: Advection

Data Source

PatentEP4112785B1A method of electropolishing
Publication Date: 2026.02.25 ROLLS ROYCE PLC
  • EP4112785B1 patent drawingFigure 1
  • EP4112785B1 patent drawingFigure 2
  • EP4112785B1 patent drawingFigure 3

AI summary

There is disclosed a method of electropolishing an internal passageway 60 of a component, wherein the passageway 60 has an inlet 62 and an outlet 64; comprising: providing an electrode assembly 42 comprising a flexible electrode 44, a shuttle 58 and a guide cable 56 extending between the flexible electrode 44 and the shuttle 58; inserting the shuttle 58 into the inlet 62; causing fluid 66 to flow through the passageway 60 to transport the shuttle 58 through the passageway 60 from the inlet 62 towards the outlet 64; pulling the guide cable 56 through the passageway 60 to position the electrode 44 in the passageway 60 adjacent to a region of the passageway 60 to be polished; and electropolishing the passageway 60 using the electrode 44 while moving the electrode 44 within the passageway 66. There is also disclosed an electrode assembly 42 for electropolishing an internal passageway 60 of a component, comprising: a flexible electrode 42, a shuttle 58, and a guide cable 56 extending between the flexible electrode 44 and the shuttle 58.