Apparatus for detecting discharge gap in electric discharge machining

An apparatus for measuring the size of a discharge gap between a machining electrode and a workpiece in electric discharge machining in which a plurality of pulse voltages are sequentially applied between said machining electrode and said workpiece to thereby machine said workpiece, comprising:

• peak detecting means responsive to a discharge voltage which develops between said machining electrode and said workpiece in response to each one of said voltage pulses for detecting a peak voltage of said discharge voltage for each of said voltage pulses;
• first converting means for converting said peak value into first digital data;
• waiting time detecting means responsive to the discharge voltage between said machining electrode and said workpiece for detecting a waiting time between the leading edge of said pulse voltage and the start of a discharge occurrence for each of said voltage pulses;
• and
• second converting means for converting said waiting time into second digital data;
• first compensating means for compensating said first digital data in accordance with a machining condition;
• second compensating means for compensating said second digital data in accordance with a machining condition;
• and
• means for computing said gap size by adding the digital data from said first and second compensating means.

An apparatus for measuring the size of a discharge gap between a machining electrode and a workpiece in electric discharge machining in which a pulse voltage is applied between said machining electrode and said workpiece to thereby machine said workpiece, comprising:

• peak detecting means responsive to a discharge voltage which develops between said machining electrode and said workpiece for detecting a peak value of said discharge voltage;
• waiting time detecting means responsive to said discharge voltage between said machining electrode and said workpiece for detecting a waiting time which is measured as the interval between the start of said pulse voltage and the start of a discharge current;
• first modifying means for modifying said peak value in accordance with a machine condition and the magnitude of said pulse voltage to produce therefrom a first modified gap signal;
• second modifying means for modifying said waiting time in accordance with a machine condition to produce therefrom a second modified gap signal;
• and
• means for determining said gap size by combining said first modified gap signal and said second modified gap signal.