Conventional EDM

Most commercial EDM in the market use current-limiting resistors to limit the amount of current. The servo mechanisms use feedback based on average current through or gap voltage to keep the necessary gap between the electrode and workpiece. As the electrode is approached toward the workpiece and when the gap is small enough, the piece is attacked with high energy sparks generated by a power supply.

With a circuit of this type, a Current-limiting is necessary to protect the switching transistors and other components during the process. The main drawback is the large amount of power, about 55% of the total energy consumption, dissipated in the current-limiting resistors (Rx in the chart). Some generators use Multi-Channel Constant Current Controller, but there are still feedback resistors in the power transistor control circuit. The Current can only be adjusted stepwise. The only effect is the distribution of energy consumption in many resistors and it is still a passive approach.

Currently existing pulse generators not only consume large amount of energy, but also perform low servo accuracy due to larger measuring errors on the gap voltage. This may affect the machining stability and may induce potential short circuit in certain circumstance. That is why there are excessive meter pointer swings with some type of the EDM pulse generators.

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