EDM Pulse Control for Edge Discharge Prevention

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Solution Overview

Problem

Conventional electric discharge machining techniques face challenges in accurately controlling discharge generation, leading to machining failures and decreased accuracy at the edges of workpieces, particularly for thick materials and press dies, due to high electric field intensity and sludge accumulation.

Innovation Solution

A method involving a power supply system with a control unit that manages the application of pulse currents between the machining electrode and workpiece, ensuring contact detection and controlled voltage application to prevent edge discharges by supplying a pulse current only when the electrode and workpiece are in contact, and adjusting the pulse magnitude and timing to minimize edge machining errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If voltage is continuously applied to the machining gap to maintain discharge, then machining productivity is improved, but discharge occurs at edge portions causing machining failures

Engineering Contradiction:

Improvemachining speedVSAvoidedge machining quality

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies periodic voltage to the machining gap instead of continuous voltage. The control unit turns on the first power supply at specific intervals (every 100 to 1000 discharge cycles) to periodically reduce the machining gap distance at edge portions, preventing discharge at edges while maintaining overall machining productivity.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent applies voltage before main discharge occurs to proactively reduce the machining gap distance at edge portions. By turning on the first power supply in advance, the gap is reduced before discharge can occur at vulnerable edge areas, preventing machining failures.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If machining gap distance is reduced to improve precision, then discharge control is improved, but discharge occurs via sludge at edge portions

Engineering Contradiction:

Improvedischarge position controlVSAvoidsludge discharge

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The patent applies counter-action in advance by using the first power supply to reduce the machining gap distance at edge portions before sludge discharge can occur. This preliminary action prevents the harmful effect of sludge discharge by maintaining proper gap distance at critical areas.

Inventive Principle:

Principle #9Preliminary anti-action

3Measurement precision

If current detection accuracy is improved to detect discharge position, then edge discharge detection is possible, but detection precision remains insufficient for thick workpieces

Engineering Contradiction:

Improvedischarge position detection accuracyVSAvoidedge machining accuracy

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The patent introduces an intermediary approach by using the first power supply to physically reduce the machining gap distance at edge portions, rather than relying solely on detecting discharge positions. This intermediary action directly addresses the detection limitation by preventing the problem at its source.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 enhances machining accuracy and reduces edge failures by precisely controlling the discharge generation, maintaining machining quality while allowing for efficient machining without significantly reducing speed.

Implementation Method 1

a first power supply circuit (1) that applies voltage to a machining gap formed between a machining electrode (3) and a workpiece (4)

Methodology Applied

Scientific EffectElectrical contact detection: Conduction (electrical)

Implementation Method 2

a second power supply circuit (2) that supplies a pulse current for machining to the machining gap when the machining electrode and the workpiece contact each other

Methodology Applied

Scientific EffectArc discharge: Electric Arc

Implementation Method 3

supplying a pulse current for machining to the machining gap... a high heat due to the arc discharge is utilized to remove the workpiece

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 4

a current pulse is supplied to the machining gap from a second power supply having a low output impedance to generate high-temperature arc, thereby melting and removing the workpiece

Methodology Applied

Scientific EffectArc discharge heating: Electric Arc

Data Source

PatentEP2497593B1Electric discharge machining method

Publication Date: 2017.09.06 FANUC LTD

Figure 1~2
Figure 3~4(4)
Figure 5~6(2)

AI summary

An electric discharge machine includes a machining power supply (100) for applying a voltage to a machining gap between a machining electrode (3) and its opposite workpiece (4) and detecting a contact between the machining electrode (3) and the workpiece (4). The machining power supply (100) includes a first power supply circuit (1) whose output voltage is equal to or less than an arc voltage, a second power supply circuit (2) for supplying a pulse current to the machining gap, and a control unit (5). When the first power supply circuit detects a contact between the machining electrode and the workpiece, the control unit operates to supply a pulse current from the second power supply circuit to the machining gap while the machining electrode and the workpiece are in contact with each other.