Wire EDM Endface Positioning Using Pulse Occurrence Ratio

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Solution Overview

Problem

Existing wire electrical discharge machines face challenges in accurately determining the position of a workpiece's endface due to vibrations of the wire electrode, leading to unstable electrical contact and reduced positioning accuracy.

Innovation Solution

A wire electrical discharge machine and method that involve a voltage application control unit to continuously apply voltage pulses between the wire electrode and workpiece, a voltage detection unit to detect voltage, and a pulse occurrence ratio calculation unit to determine the endface position based on the ratio of detected pulses to applied pulses, while using a stepwise feed mechanism to improve accuracy by accounting for wire electrode vibrations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the wire electrode is brought close to the workpiece to detect electrical contact for positioning, then the endface position can be determined, but the wire electrode vibration causes incorrect position determination

Engineering Contradiction:

Improveendface position determination accuracyVSAvoidpositioning accuracy

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces mechanical contact-based positioning with an electrical field-based detection system. Voltage pulses are applied between the wire electrode and workpiece, and the resulting current is detected to determine endface position. This substitution eliminates the need for direct mechanical contact, thereby avoiding errors caused by wire electrode vibrations during approach.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent employs periodic voltage pulse application between the wire electrode and workpiece. By applying voltage pulses at regular intervals and detecting the current response, the system can determine endface position dynamically. This periodic action allows the system to capture position information at multiple time points, enabling accurate positioning even when the wire electrode is vibrating during approach.

Inventive Principle:

Principle #19Periodic action

2Measurement precision

If voltage pulses are continuously applied between the wire electrode and workpiece, then the pulse occurrence ratio can be calculated to determine endface position, but wire electrode vibration causes unstable electrical contact

Engineering Contradiction:

Improveendface position determination accuracyVSAvoidelectrical contact stability

Core Design Contradiction:

Measurement precisionVSStability of the object's composition

Solution Approach 1:

The patent implements a feedback mechanism where the current flowing between the wire electrode and workpiece during voltage pulse application is continuously detected. This current information serves as feedback about the electrical contact state, which is then used to calculate the pulse occurrence ratio and determine endface position. The feedback loop enables real-time adjustment and accurate positioning despite vibrations causing unstable contact.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent utilizes changes in electrical parameters (voltage, current, pulse occurrence ratio) to determine endface position. By monitoring how these parameters change as the wire electrode approaches the workpiece, the system can identify the precise endface position. This parameter-based approach transforms the unstable physical contact into measurable electrical signals that can be processed accurately.

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

This approach enables precise determination of the workpiece's endface position with high accuracy, even when the wire electrode is vibrating, by stabilizing the electrical contact and enhancing the calculation precision of the pulse occurrence ratio.

Implementation Method 1

a voltage application control unit configured to continuously apply voltage pulses between the wire electrode and the workpiece

Methodology Applied

Scientific EffectElectrical pulse application: Electrical Impedance Tomography

Implementation Method 2

a voltage detection unit configured to detect a voltage between the wire electrode and the workpiece

Methodology Applied

Scientific EffectElectrical voltage detection: Electric Field

Data Source

PatentUS11458554B2Wire electrical discharge machine and endface position determining method

Publication Date: 2022.10.04 FANUC LTD

AI summary

A wire electrical discharge machine determines the position of an endface of a workpiece by relatively moving a wire electrode toward the workpiece. The wire electrical discharge machine includes: a voltage application control unit configured to continuously apply voltage pulses between the wire electrode and the workpiece; a voltage detection unit configured to detect a voltage between the wire electrode and the workpiece; a pulse occurrence ratio calculation unit configured to calculate a pulse occurrence ratio that is a ratio of the number of the voltage pulses detected by the voltage detection unit to the number of the voltage pulses applied per a predetermined time by the voltage application control unit; and an endface position determination unit configured to determine the position of the endface of the workpiece based on the pulse occurrence ratio.