Method and apparatus for supplying power for electric discharge machining

A power supply for an electroerosion machine for machining a workpiece using a tool electrode, said tool electrode being spaced from said workpiece across a machining gap, said power supply comprising:

• a discharge detector for detecting initiation of a discharge across said machine gap and for thereupon generating a detection signal;
• a main power circuit, responsive to said detection signal, for repeatedly applying a main machining pulse of a first polarity across said cross said machining gap;
• an auxiliary power circuit for applying an auxiliary voltage pulse of a second polarity opposite to said first polarity across said machining gap prior to initiation of said main machining pulse;
• means for controlling said auxiliary voltage pulse whereby, for a pre-determined percentage of said main machining pulses, an auxiliary voltage pulse is applied across said machining gap prior to said main machining pulses, said pre-determined percentage being less than 100%.

A power supply for an electroerosion machine for machining a workpiece, using a tool electrode, said tool electrode being spaced from said workpiece across a machining gap, said power supply comprising:

• a first power circuit for repeatedly applying a main machining pulse of a first polarity across said machining gap;
• a second power circuit for applying first auxiliary voltage pulses of a second polarity, opposite to said first polarity across said machining gap;
• a third power circuit for applying second auxiliary voltage pulses of said first polarity across said machining gap;
• and
• control means for selectively applying either said first or said second auxiliary voltage pulses across said gap at a time prior to initiation of said main machining pulse, said first and second auxiliary pulses being applied in a predetermined ratio whereby electrolyte effects in said machining gap are effectively inhibited while maintaining a high machining rate.

A method of inhibiting electrolytic activity during electroerosion machining of a workpiece by means of an electrode spaced from said workpiece across a machining gap filled with a liquid dielectric comprising:

• generating a main gating pulse signal having an on time and an off time;
• applying a train of successive machining pulses of a first polarity across said machining gap in response to said main gating pulse signal;
• and
• selectively applying either an auxiliary voltage pulse of a second polarity opposite to said first polarity or a modified machining pulse across said machining gap, saids auxiliary voltage pulse being applied across said machining gap, said modified machining pulse being applied across said machining gap during the on time of said main gating pulse signal, and prior to applying a machining pulse, said modified machining pulse being applied across said machining gap in the absence of said auxiliary voltage pulse and in synchronism with said main gating pulse on time, the ratio of said auxiliary voltage pulses to said modified machining pulses being selected to effectively inhibit electrolytic effects while maintaining a high machining rate.

A power supply for an electroerosion machine for machining a workpiece, using a tool electrode, said tool electrode being paced from said workpiece across a machining gap, said power supply comprising:

• means for generating a gating pulse having an ON time and an OFF time;
• a first power circuit for repeatedly applying a main machining pulse of a first polarity across said machining gap in response to said gating pulse;
• a second power circuit for applying an auxiliary voltage pulse of a second polarity, opposite to aid first polarity across said machining gap;
• control means for selectively applying either said auxiliary voltage pulse across said gap at a time prior to initiation of said main machining pulse, or a modified main machining pulse applied across gap during said gating pulse ON time in the absence of an auxiliary voltage pulse, said auxiliary voltage pulses and main machining pulses being applied in a predetermined ratio whereby electrolytic effects in said machining gap are effectively inhibited while maintaining a high machining rate.