Electrode Wire Grain Formation for EDM

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Solution Overview

Problem

Existing electrode wires for electro-discharge machining suffer from low tensile strength and machining speed, leading to inferior machining accuracy and increased machining particles, particularly when using brass core wires with high zinc content, which can fragment and produce excessive particles during elongation processes.

Innovation Solution

The development of an electrode wire with a core wire made of softer brass, plated with a zinc-copper alloy, where the core wire is subjected to a heat treatment process to increase elongation percentage and reduce tensile strength, forming cracks perpendicular to the wire's longitudinal direction, allowing the core wire material to erupt and form grains on the surface, thereby reducing machining particles and improving machining speed and surface roughness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a pure copper wire is used for electro-discharge machining, then electrical conductivity is improved, but tensile strength deteriorates

Engineering Contradiction:
Improveelectrical conductivityVSAvoidtensile strength
Core Design Contradiction:
Use of energy by moving objectVSStrength

Solution Approach 1:

The patent uses a composite wire structure with a copper core (for electrical conductivity) and a zinc plating layer (for improved tensile strength and machining performance). This composite structure combines the advantages of both materials to resolve the contradiction between electrical conductivity and tensile strength.

Inventive Principle:
Principle #40Composite materials

2Strength

If a brass electrode wire with high zinc content is used, then tensile strength is improved, but machining particles increase

Engineering Contradiction:
Improvetensile strengthVSAvoidmachining particles
Core Design Contradiction:
StrengthVSObject-generated harmful factors

Solution Approach 1:

The patent optimizes the zinc content parameter to 20-40% in the brass electrode wire, which is lower than conventional high-zinc brass wires. This parameter change reduces the formation of brittle beta phases that cause fragmentation, thereby reducing machining particles while maintaining adequate tensile strength.

Inventive Principle:
Principle #35Parameter changes

3Strength

If a high strength wire such as molybdenum or tungsten is used, then tensile strength is improved, but machining speed deteriorates

Engineering Contradiction:
Improvetensile strengthVSAvoidmachining speed
Core Design Contradiction:
StrengthVSProductivity

Solution Approach 1:

The patent employs a copper-based composite wire (copper core with zinc plating or low-zinc brass) that maintains high electrical conductivity and adequate tensile strength, avoiding the use of high-strength but low-conductivity materials like molybdenum or tungsten. This composite approach ensures both mechanical integrity and high machining speed through efficient electrical discharge.

Inventive Principle:
Principle #40Composite materials

4Productivity

If zinc content is increased in brass alloy, then machining speed is improved, but drawing process difficulty increases

Engineering Contradiction:
Improvemachining speedVSAvoiddrawing process
Core Design Contradiction:
ProductivityVSEase of manufacture

Solution Approach 1:

The patent limits zinc content to 20-40%, avoiding excessive zinc content that would form too much brittle beta phase. This parameter optimization balances machining speed improvement with manufacturability, ensuring the wire can be drawn without excessive difficulty while still achieving enhanced machining performance.

Inventive Principle:
Principle #35Parameter changes

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

The approach significantly reduces machining particles, enhances machining speed, and improves surface roughness by forming grains that are longer than they are wide, perpendicular to the wire's direction, which helps in preventing particle fragmentation and increasing thermal energy explosion power during electro-discharge machining.

Implementation Method 1

formed at a boundary region between the core wire and a second metal plated on an outer surface of the core wire due to mutual diffusion between the core wire and the second metal

Methodology Applied
Scientific EffectMutual diffusion: Diffusion

Implementation Method 2

the core wire is subjected to a heat treatment process to increase elongation percentage and reduce tensile strength, forming cracks perpendicular to the wire's longitudinal direction

Methodology Applied
Scientific EffectHeat treatment: Heat Treatment

Implementation Method 3

A high-frequency voltage is applied between the electrode wire 2 and an inner wall surface of the start hole 7 while the electrode wire 2 is being continuously inserted into the workpiece 1 in the perforation direction of the start hole 7, thereby generating arc between the electrode wire 2 and the inner wall surface of the start hole 7, so that the workpiece 1 is melted.

Methodology Applied
Scientific EffectArc discharge: Electric Arc

Implementation Method 4

melts are removed by using a machining liquid and the instantaneous vaporization power between the electrode wire 2 and the workpiece 1

Methodology Applied
Scientific EffectInstantaneous vaporization: Evaporation

Data Source

PatentEP2517817B1Electrode wire for electro-discharge machining and method for manufacturing the same
Publication Date: 2015.09.02 SEONG HYUN SOO
  • EP2517817B1 patent drawingFigure 1
  • EP2517817B1 patent drawingFigure 2
  • EP2517817B1 patent drawingFigure 3

AI summary

Disclosed are an electrode wire for electro-discharge machining and a method for manufacturing the same. The electrode wire includes a core wire including a first metal including copper, a first alloy layer formed at a boundary region between the core wire and a second metal plated on an outer surface of the core wire due to mutual diffusion between the core wire and the second metal, and a second alloy layer formed due to diffusion of the first metal to the second metal. A core wire material is erupted onto a surface of the electrode wire for electro-discharge machining, which includes the core wire, the first alloy layer, and the second alloy layer, along cracks appearing on the second alloy layer, so that a plurality of grains are formed on the surface of the electrode wire.