WEDM Discharge Position Detection Using Feeder Voltage Difference
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Solution Overview
Problem
Current methods for detecting discharge position in wire electrical discharge machining (WEDM) are inaccurate due to changes in electrode cable inductance, require complex calibrations, are expensive, and unsuitable for high-frequency, narrow pulses, especially in noisy environments.
Innovation Solution
Measuring the voltage difference between upper and lower current feeders at the end of the discharge pulse when current is zero, minimizing electromagnetic emissions, and using this voltage difference to determine the discharge position, which is independent of electrode cable impedance and resistant to noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current methods measure partial discharge currents through upper and lower feeding paths to detect discharge position, then discharge position can be detected, but the measurement accuracy deteriorates due to changes in electrode cable inductance and noise
Solution Approach 1:
The patent introduces voltage as an intermediary measurement parameter instead of directly measuring current. By measuring voltage at the current feeders and calculating current through differentiation (I = C*dV/dt), the system avoids direct current measurement interference from cable inductance changes. The voltage signal serves as a mediator that is less susceptible to electromagnetic noise and cable parameter variations.
Solution Approach 2:
The patent replaces direct electrical current measurement with voltage measurement and mathematical differentiation. This substitution transforms the measurement approach from directly sensing current (which is noisy and affected by cable inductance) to measuring voltage and deriving current information through signal processing, thereby improving measurement reliability.
2Speed
If voltage is measured during the discharge pulse to determine discharge position, then real-time detection is achieved, but electromagnetic noise increases making measurement unreliable
Solution Approach 1:
The patent performs voltage measurement at the current feeders during the discharge pulse, then differentiates the voltage signal to obtain current information. By preparing and measuring the voltage signal during the pulse and processing it immediately afterward, the system achieves real-time detection while avoiding the peak electromagnetic interference period.
Solution Approach 2:
The patent rushes through the voltage measurement and differentiation process during and immediately after the discharge pulse, obtaining current information before the electromagnetic noise subsides completely. This allows real-time discharge position detection while minimizing the impact of electromagnetic interference through rapid signal processing.
3Measurement precision
If complex calibration procedures are implemented to compensate for cable inductance changes, then measurement accuracy can be maintained, but device complexity increases
Solution Approach 1:
The patent extracts the measurement points to the current feeders where voltage can be measured without being affected by cable inductance variations. By taking the measurement reference point away from the discharge zone and placing it at the feeders, the system eliminates the need for complex calibration procedures to compensate for cable parameter changes.
4Measurement precision
If expensive toroidal current transformers are used to measure discharge currents, then accurate current measurement is achieved, but cost increases
Solution Approach 1:
The patent replaces expensive toroidal current transformers with simpler voltage measurement circuits and digital differentiation. By using readily available voltage sensors and computational methods instead of costly specialized current measurement devices, the system achieves comparable measurement accuracy at significantly lower cost.
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
Provides a reliable and cost-effective method for precise discharge position detection, applicable to both main cuts and trim cuts, with improved accuracy and reduced complexity, unaffected by electrode cable changes or noise.
Implementation Method 1
a first voltage UCH1 is measured between a first current feeder and the workpiece, and a second voltage UCH2 is measured between a second current feeder and the workpiece, wherein said first voltage UCH1 and said second voltage UCH2 are measured when current of the machining discharge pulse is zero
Data Source
Figure 1~2
Figure 3a~3b
Figure 4a~4b
AI summary
The invention relates to a method and device for wire electrical discharge machining (WEDM), in which a first voltage UCH1 is measured between a first current feeder and the workpiece, and a second voltage UCH2 is measured between a second current feeder the workpiece, whereas said first- and second voltage UCH1, UCH2 are measured when current of the machining discharge pulse is zero, for instance at the end of the of the machining discharge current pulse, and a voltage difference of said measured voltages ΔUCH = UCH1 - UCH2 is determined, and a discharge position of said machining discharge pulse is determined in real time, as a function of said voltage difference ΔUCH.