EDM Polarity Switching Eliminates Impedance Matching
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Solution Overview
Problem
Existing electric discharge machining apparatuses require an impedance matching circuit to maintain optimal power supply, which increases costs and is not necessary when using high-frequency AC voltage with short ON time pulses.
Innovation Solution
An electric discharge machining apparatus that alternates between straight and reverse polarity by using a power supply with switches and a pulse generating device to control current pulses, eliminating the need for an impedance matching circuit by maintaining high-frequency switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an impedance matching circuit is provided between the AC power supply and the machining gap, then the power supply stability is improved, but the apparatus cost increases
Solution Approach 1:
The patent extracts and eliminates the impedance matching circuit from the system by using high-frequency AC voltage with short ON time pulses. The pulse generation unit controls the power supply to operate in pulse mode, which inherently manages impedance issues without requiring a separate matching circuit, thereby reducing apparatus complexity while maintaining power supply stability.
Solution Approach 2:
The patent changes the operating parameters of the power supply by using high-frequency AC voltage with short ON time pulses instead of continuous or traditional pulsed operation. This parameter change allows the system to achieve stable power delivery to the machining gap without requiring an impedance matching circuit, as the high-frequency pulsed operation naturally adapts to the gap's impedance characteristics.
2Manufacturing precision
If the current pulse ON time is shortened to improve surface roughness, then the surface quality is improved, but the power supply impedance matching becomes more difficult
Solution Approach 1:
The patent employs periodic pulsed action with high-frequency AC voltage and short ON time to achieve both improved surface roughness and maintained impedance matching. The periodic pulse train allows the system to deliver sufficient average power while keeping individual pulse durations short enough to produce fine surface quality, and the high frequency ensures the power supply remains stable despite the short pulse width.
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
Enables efficient current pulse supply to the machining gap without an impedance matching circuit, improving surface roughness and maintaining high impedance stability across varying machining conditions.
Implementation Method 1
supplying a current pulse to a machining gap formed between a work piece and a tool electrode to machine the work piece
Data Source
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AI summary
The present invention relates to an electric discharge machining device which supplies a current pulse to a machining gap (9) while switching polarity. The electric discharge machining device includes: a first switch (41) provided between the positive pole of a power supply (30) and a work piece (4); a second switch (42) provided between the negative pole of the power supply and the work piece; a third switch (43) provided between the negative pole of the power supply and a tool electrode (2); a fourth switch (44) provided between the positive pole of the power supply and the tool electrode; and a pulse generating device (10). In order to supply a series of current pulses to the machining gap with a straight polarity, the pulse generating device repeatedly switches on and off either the first or third switch while the other switch is on. In order to supply a series of current pulses to the machining gap with a reverse polarity, the pulse generating device repeatedly switches on and off either the second or fourth switch while the other switch is on.