Wire EDM Current Control for Gap-State Machining Stability

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Solution Overview

Problem

Existing wire electrical discharge machines face challenges in enhancing machining speed while preventing frequent breakage of the wire electrode, which occurs when the machining current is too large.

Innovation Solution

A control method for a wire electrical discharge machine that determines the discharge gap state and adjusts the machining current accordingly. The method includes determining the discharge gap state among normal, short-circuited, and open states, recording these states, setting the machining current based on previous states, and controlling the main discharge circuit to supply appropriate currents depending on the current state.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the machining current is increased to enhance machining speed, then the machining speed is improved, but the wire electrode frequently breaks

Engineering Contradiction:
Improvemachining speedVSAvoidwire electrode breakage
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

The patent implements dynamic adjustment of machining current based on real-time discharge gap state detection. The control system continuously monitors the discharge gap state and dynamically changes the machining current magnitude accordingly, transitioning from static to dynamic current control to prevent wire breakage while maintaining high machining speed

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent employs feedback control by detecting the discharge gap state and using this information to adjust the machining current. The control system receives feedback about the discharge gap condition and automatically modifies the current level, creating a closed-loop control system that balances machining speed and wire electrode reliability

Inventive Principle:
Principle #23Feedback

2Reliability

If the machining current is decreased to prevent wire breakage, then the wire electrode reliability is improved, but the machining speed reduces

Engineering Contradiction:
Improvewire electrode breakageVSAvoidmachining speed
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

The system dynamically adjusts current levels based on actual discharge conditions rather than using a fixed low current. By detecting the discharge gap state, the system can temporarily increase current when conditions are favorable and reduce it when risk of breakage exists, optimizing both reliability and productivity

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent changes the machining current parameter dynamically based on detected discharge gap states. Instead of maintaining a constant conservative current level, the system varies the current parameter according to real-time conditions, allowing higher currents when safe and lower currents when necessary to prevent breakage

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 method allows for setting a machining current that enhances machining speed while effectively reducing the risk of wire electrode breakage, thereby improving machining efficiency and accuracy.

Implementation Method 1

a discharge induction circuit configured to apply a discharge induction voltage across the discharge gap

Methodology Applied
Scientific EffectElectric discharge: Electric Spark

Implementation Method 2

main discharge circuit configured to supply machining current to the discharge gap

Methodology Applied
Scientific EffectElectrical discharge machining: Electrical Discharge Machining

Data Source

PatentEP3674026B1Control method of wire electrical discharge machine
Publication Date: 2025.01.29 FANUC LTD
  • EP3674026B1 patent drawingFigure 1
  • EP3674026B1 patent drawingFigure 2
  • EP3674026B1 patent drawingFigure 3A~3C

AI summary

A wire electrical discharge machine (10) for machining a workpiece (12) by generating electric discharge at a discharge gap between the workpiece and a wire electrode (14) includes: a machining current setting unit (26) for setting the magnitude of a normal machining current depending on the discharge gap state at application of a discharge induction voltage at the previous time or previous times; and a machining current control unit (30) configured to control a main discharge circuit (18) so as to supply the normal machining current to the discharge gap when the present discharge gap state is the normal state, control the main discharge circuit (18) so as to supply a short-circuit machining current smaller than a predetermined current to the gap when the discharge gap state is the short-circuited state, and control the main discharge circuit (18) so as not to supply any machining current to the gap when the discharge gap state is the open state.