EDM Guide Tube Assembly for Long-Reach Seized Fasteners
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Solution Overview
Problem
Conventional EDM devices are limited in their ability to access and machined fasteners located beyond 100 mm due to the need for direct line of sight and limited reach, making it difficult to disassemble complex mechanical assemblies like turbofan gas turbine engines where fasteners are subjected to thermal and mechanical stress, and are often inaccessible due to design constraints.
Innovation Solution
An electrode guide assembly with a guide tube featuring radially inwardly projecting supporting protrusions that provide mechanical support and reduce friction, allowing for axially slidable movement of the electrode, along with a fluid feed and return system for dielectric fluid, enabling operation up to 1000 mm from the fastener and in confined spaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional EDM devices are used, then direct line of sight and close proximity (within 100 mm) are required for operation, but this limits access to fasteners in confined spaces and complex assemblies
Solution Approach 1:
A flexible guide tube is introduced as an intermediary component between the EDM device and the fastener. The guide tube can extend up to 1000 mm in length and bend to navigate around obstacles, allowing the electrode to reach fasteners in confined spaces while the operator can position the device from a more accessible location. This mediator overcomes the limitation of direct line of sight and close proximity requirements.
Solution Approach 2:
The guide tube is designed with flexible segments that allow it to bend and change shape dynamically. This flexibility enables the guide tube to adapt to different geometries and reach fasteners in various positions within complex assemblies. The dynamic nature of the flexible guide tube allows it to conform to the workspace geometry, significantly expanding the operational range beyond what rigid structures could achieve.
2Length of moving object
If the electrode is extended to reach distant fasteners, then the reach is improved, but buckling forces and friction increase, making electrode movement difficult
Solution Approach 1:
The guide tube is divided into multiple flexible segments rather than being a single rigid structure. Each segment can independently flex and bend, which distributes the mechanical stresses and reduces buckling forces. The segmented structure allows the electrode to be supported at multiple points along its length, making it easier to move the electrode axially even when reaching distant fasteners.
Solution Approach 2:
The guide tube is constructed using flexible materials that can bend without breaking while maintaining structural integrity. This flexible shell structure allows the guide tube to conform to complex geometries and reach distant fasteners without requiring excessive force to move the electrode. The flexibility reduces the buckling forces that would otherwise occur in a rigid, extended structure.
3Length of moving object
If a long guide tube is used to reach distant fasteners, then the range is extended, but fluid delivery to the electrode becomes inefficient
Solution Approach 1:
The electrode is nested within the guide tube, and the fluid delivery system is nested within the electrode structure. The electrode contains internal fluid channels that receive dielectric fluid through the guide tube. This nested arrangement minimizes the volume of fluid needed and maintains efficient fluid delivery even through the extended 1000 mm guide tube length, as the fluid travels through contained pathways rather than open space.
4Ease of manufacture
If conventional machining techniques are used on seized fasteners, then material removal is achieved, but the work hardening nature of materials and limited access make conventional techniques inapplicable
Solution Approach 1:
The patent replaces conventional mechanical machining techniques with electrical discharge machining (EDM). Instead of using mechanical cutting tools that would be blocked by work hardening and limited access, the system uses electrical discharges to erode the fastener material. This substitution allows machining of seized fasteners in locations that are inaccessible to conventional mechanical tools, as the electrode can be guided through the flexible guide tube to reach distant and confined fasteners.
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 versatility and range of EDM operations, allowing for the machining of fasteners in hard-to-reach locations, reducing the labor intensity of disassembly and enabling faster and simpler assembly strip-down processes.
Implementation Method 1
the guide tube having a set of at least two supporting protrusions, the protrusions projecting radially inwardly from an inner diametral surface of the guide tube, the electrode being slidably accommodated within the guide tube, with an outer diametral surface of the electrode abutting against the set of supporting protrusions
Implementation Method 2
the first end of the guide tube being in fluid communication with the second end of the guide tube to thereby provide a fluid feed channel, the second end of the guide tube being in fluid communication with the first end of the guide tube to thereby provide a fluid return channel
Implementation Method 3
Electric Discharge Machining (EDM) is a well-known technique that is used for the machining of metal materials. EDM as the title suggests creates an electrical discharge by the removal of material from a workpiece. The electrical discharge phenomenon results from an electrical voltage being applied between an electrode and the workpiece
Data Source
AI summary
An electrode guide assembly for an EDM process includes a guide tube having a first end and a second end, a fluid feed portion, a fluid return portion, and an electrode. The guide tube has a set of at least two supporting protrusions, with the protrusions projecting radially inwardly from an inner diametral surface of the guide tube. The electrode is slidably accommodated within the guide tube, with an outer diametral surface of the electrode abutting against the set of supporting protrusions. The first end of the guide tube is in fluid communication with the second end of the guide tube to thereby provide a fluid feed channel, and the second end of the guide tube is in fluid communication with the first end of the guide tube to thereby provide a fluid return channel.