Wire EDM Current Control for Short-Circuit Chip Removal
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Solution Overview
Problem
Wire electric discharge machining faces challenges in maintaining straightness accuracy and preventing short-circuiting due to machining chips, especially with thick workpieces, leading to reduced machining efficiency and accuracy.
Innovation Solution
A wire electric discharge machining method that classifies the inter-electrode state based on discharge delay time, adjusting the machining current accordingly to prevent short-circuiting and improve straightness accuracy, by supplying a short-circuit machining current when the inter-electrode gap is short-circuited and reducing or eliminating machining current when the discharge delay time is less than a reference value to avoid excessive machining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the plate thickness of a workpiece increases, then the machining capability for thick workpieces is improved, but the amount of deflection of the central portion of the wire increases leading to reduced straightness accuracy
Solution Approach 1:
The patent employs feedback control by measuring the discharge delay time and using it to adjust the machining current. The discharge delay time measurement provides real-time information about the inter-electrode gap state, and this feedback is used to dynamically control the machining current to prevent excessive machining at the central portion of thick workpieces, thereby maintaining straightness accuracy.
Solution Approach 2:
The patent changes the machining parameter (machining current) based on the measured discharge delay time. When the discharge delay time is less than a predetermined value, the machining current is reduced or stopped, preventing excessive machining. This dynamic parameter adjustment resolves the contradiction by adapting the machining process to the actual inter-electrode gap conditions during thick workpiece machining.
2Productivity
If the machining voltage is increased to maintain satisfactory inter-electrode gap state, then the machining efficiency is improved, but excessive machining occurs at the central portion leading to reduced straightness accuracy
Solution Approach 1:
The patent makes the machining current dynamic rather than fixed. The machining current is adjusted in real-time based on the measured discharge delay time, allowing the system to adapt to changing inter-electrode gap conditions. This dynamic control enables efficient machining when conditions are favorable while preventing excessive machining when the gap is too narrow, thus resolving the contradiction between productivity and precision.
Solution Approach 2:
The system uses feedback from discharge delay time measurement to control the machining current. This feedback mechanism ensures that machining voltage and current are applied only when the inter-electrode gap is appropriate, preventing excessive machining at the central portion of thick workpieces while maintaining high machining efficiency when conditions permit.
3Reliability
If the discharge delay time is less than a predetermined value, then the inter-electrode gap is narrow, but applying normal machining current causes excessive machining and wire breakage
Solution Approach 1:
The patent uses feedback control where the discharge delay time is measured and used to determine the appropriate machining current. When the discharge delay time indicates a narrow inter-electrode gap (less than predetermined value), the system feedback-reduces or stops the machining current to prevent wire breakage, while still allowing controlled machining to proceed, thus resolving the contradiction between reliability and precision.
Solution Approach 2:
The machining current parameter is changed based on the discharge delay time measurement. When the discharge delay time is less than a predetermined value, the machining current is reduced or stopped, preventing both wire breakage and excessive machining. This parameter change strategy simultaneously addresses both reliability and manufacturing precision concerns.
4Manufacturing precision
If discharge position is calculated based on current ratio from inductor, then shape accuracy is improved, but the configuration becomes complicated and expensive
Solution Approach 1:
The patent extracts only the essential information needed for control - the discharge delay time - and discards the complex current ratio measurement system. By focusing on a single key parameter (discharge delay time) rather than measuring and processing multiple current signals, the system achieves effective discharge position detection and control with much simpler and less expensive circuitry.
Solution Approach 2:
Instead of using complex analog current ratio measurement circuits, the patent uses a digital timing measurement approach that copies the essential control function in a simpler form. The discharge delay time measurement provides sufficient information for discharge position detection and control without requiring the complex inductor and analog signal processing circuits of prior art.
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 method enhances the straightness accuracy of thick workpieces and improves machining efficiency by preventing short-circuiting, allowing for increased machining speed and reduced wire breakage.
Implementation Method 1
an auxiliary discharge circuit applies voltage to an inter-electrode gap
Implementation Method 2
a main discharge circuit supplies a machining current to the workpiece
Data Source
Figure 1
Figure 2A~2C
Figure 3A~3B
AI summary
In a wire electric discharge machine which comprises an auxiliary discharge circuit and a main discharge circuit a threshold voltage is used to clasify an inter-electrode state into three categories: open, discharge, or short-circuit. Based on this classification, the magnitude of a machining current supplied from a main discharge circuit is determined. If a short circuit is detected, a short-circuit machining current is supplied from the main discharge circuit to the inter-electrode gap to remove the machining chips. In this way, establishment of a complete short-circuit state is prevented so that the machining efficiency is improved to increase the machining speed.