Wire EDM Control Device Dynamic Threshold Adjustment
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Solution Overview
Problem
In wire electrical discharge machining, the average voltage between the wire electrode and workpiece drops sharply during finishing mode, leading to a high risk of short-circuiting due to the narrow gap and lower discharge voltage, causing the wire electrode to potentially touch the workpiece.
Innovation Solution
A control device for wire electrical discharge machines that monitors the discharge status value, adjusts the relative movement speed of the wire electrode based on the gap voltage or discharge pulses, and changes the backward-movement threshold from a first to a second threshold when the voltage change exceeds a predetermined variation, ensuring the wire electrode moves backward to avoid contact with the workpiece.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the wire electrode is moved backward when the average voltage becomes lower than a short-circuit reference voltage, then short-circuiting is prevented, but the machining speed decreases and surface marks may occur
Solution Approach 1:
The patent applies dynamics by making the threshold voltage value changeable based on discharge status. The control device dynamically adjusts the threshold from a first threshold value (when discharge status is stable) to a second threshold value (when discharge status changes rapidly), allowing the system to adapt to different machining conditions and prevent short-circuiting while maintaining machining speed.
Solution Approach 2:
The patent changes the parameter of threshold voltage value based on the rate of change of discharge status. When the discharge status value changes rapidly (indicating potential short-circuit risk), the threshold is adjusted to a higher second threshold value, triggering earlier backward movement of the wire electrode to prevent short-circuiting while maintaining surface quality.
2Reliability
If the threshold for backward movement is set high to prevent short-circuiting, then reliability improves, but machining speed decreases due to frequent backward movements
Solution Approach 1:
The threshold value is made dynamic rather than fixed. The control device monitors the rate of change of discharge status and adjusts the threshold accordingly - using a first threshold when discharge is stable and a second (higher) threshold when discharge status changes rapidly. This dynamic adjustment prevents unnecessary backward movements while ensuring protection when needed.
Solution Approach 2:
The system uses feedback by continuously monitoring the discharge status value and its rate of change. Based on this feedback, the control device determines whether to switch between first and second threshold values, creating a closed-loop control system that optimizes both short-circuit prevention and machining efficiency.
3Reliability
If the wire electrode moves backward frequently to maintain gap distance, then short-circuit prevention improves, but machining precision decreases due to surface marks
Solution Approach 1:
The patent changes the threshold parameter based on the rate of change of discharge status. When discharge status changes rapidly (indicating imminent short-circuit risk), the second threshold value is used to trigger backward movement. When discharge is stable, the first (lower) threshold is used, allowing the wire electrode to maintain closer distance to the workpiece for better surface quality without risking short-circuiting.
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
Effectively suppresses short-circuiting between the wire electrode and workpiece, maintaining machining precision and preventing surface marks, while adjusting the threshold settings to maintain optimal machining speed.
Implementation Method 1
a discharge status acquisition unit configured to obtain a discharge status value, which is a gap voltage between the wire electrode and the workpiece
Implementation Method 2
the reciprocal of the number of electrical discharge pulses between the wire electrode and the workpiece
Data Source
AI summary
A control device includes a speed setting unit configured to set a relative movement speed of a wire electrode with respect to a workpiece depending on the average of gap voltage per unit time, i.e., average gap voltage, and set the relative movement speed so as to move the wire electrode backward when the average gap voltage is less than a threshold, and a map compensation unit configured to change the threshold from a first threshold that is set when the amount of change in the average gap voltage is lower than a predetermined variation, to a second threshold that is greater than the first threshold, when the average gap voltage has changed in a decreasing direction and the amount of change in the average gap voltage becomes equal to or greater than the predetermined variation.