Pulse Parameter Control Design: Precision Adjustment for Multi-Scenario Machining

In wire EDM, pulse parameters (frequency, pulse width, duty cycle) directly determine machining efficiency (wide pulse width + high frequency → high efficiency) and machining accuracy (narrow pulse width + low frequency → high precision). Digital control enables independent adjustment and real-time adaptation. The design approach is as follows:

3. Digital Control Core Selection
High-performance MCU (e.g., STM32H743) or FPGA/CPLD (e.g., ALTERA) is selected as the control core. MCU/CPLD clock ≥400MHz, supports 16-bit ADC sampling (accuracy ±0.1%), capable of real-time acquisition of output current and voltage signals, calculating discharge status, and adjusting pulse parameters. FPGA is suitable for high-frequency pulse (>50kHz) scenarios, with pulse generation delay ≤10ns, and finer adjustment steps (frequency 0.1kHz, pulse width 0.1μs).

4. Pulse Parameter Adjustment Logic
(1) Frequency Adjustment: By changing the PWM output period of MCU/FPGA, continuous adjustment from 1kHz to 80kHz can be achieved. A frequency lock function is set—if grid interference causes frequency fluctuation >5% during machining, a phase-locked loop (PLL) is automatically triggered to calibrate, ensuring frequency stability ±1%.
   (2) Pulse Width Adjustment: Employ dead-time control on top of the PWM signal to prevent IGBT bridge shoot-through. Adjust the PWM high-level duration to achieve 1μs–80μs pulse width. For narrow pulses (1μs–10μs), a high-frequency narrow pulse generation algorithm is used to prevent insufficient discharge energy due to slow rising edges.
   (3) Duty Cycle Linkage: Set linkage constraints between duty cycle and frequency (e.g., frequency >50kHz → duty cycle ≤50%; frequency <10kHz → duty cycle ≤90%) to avoid IGBT overheating at high frequency and wide pulse width while ensuring sufficient ionization time between pulses, reducing wire electrode wear.

5. Adaptive Parameter Adjustment Function
   Real-time monitoring of gap voltage (between wire and workpiece) and discharge current waveform.
   – If gap voltage fluctuates >10% (indicating unstable discharge), the system automatically reduces pulse width (e.g., 20μs → 15μs) and lowers peak current (e.g., 25A → 20A).
   – If no discharge current is detected (gap too large), the system automatically increases pulse width until stable discharge is restored, requiring no manual intervention.

6. Loss Control Design: Low Loss and Long Lifespan
   (1) Power transistor loss control: High-power, high-frequency drive circuits are used to effectively control current while keeping switching loss and temperature rise low.
   (2) The power supply provides controllable current slope, controlling the current rise rate during discharge, which effectively reduces molybdenum wire wear.

7. Sampling & Feed
   (1) The design features adaptive tracking and adjustment, capable of analyzing voltage and current signals under real working conditions.
   (2) Sampling circuits for single-pass machining and re-machining are separated, making it more suitable for multi-pass sampling decisions, achieving the fastest and optimal machining results.