Electrical discharge machining method and electrical discharge machining apparatus

An electrical discharge machining method for machining a workpiece by applying voltage between a machining electrode and the workpiece to cause electrical discharge therebetween, said method comprising the steps of:

• (a) determining initial machining conditions for controlling a discharge state between the machining electrode and the workpiece;
• (b) detecting the discharge state during a test machining operation performed under the initial machining conditions determined in said step (a) and outputting the detected data indicative of the discharge state;
• (c) setting the detected data outputted in said step (b) as a target value of the detected data indicative of the discharge state;
• (d) detecting the discharge state between the machining electrode and the workpiece during an actual machining operation and outputting detected data indicative of the discharge state;
• (e) obtaining the deviation between the detected data outputted in said step (d) and the target value set in said step (c);
• (f) successively updating at least one of said initial machining conditions based on the deviation obtained in said step (e) so that the detected data outputted in said step (d) is controlled to coincide with said target value;
• and
• (g) controlling the discharge state in accordance with the new machining conditions obtained in said step (f).

An electrical discharge machining apparatus for machining a workpiece by applying voltage between a machining electrode and the workpiece to cause electrical discharge therebetween, said apparatus comprising:

• storage means for storing initial machining conditions for controlling a discharge state between the machining electrode and the workpiece, a target value of detected data indicative of the discharge state, and a constant for deriving new machining conditions;
• detecting means for detecting the discharge state between the machining electrode and the workpiece and outputting the detected data indicative of the discharge state;
• arithmetic processing means for deriving the deviation between the detected data outputted from said detecting means and the target value stored in said storage means, executing a predetermined arithmetic operation based on the constant stored in said storage means and said deviation and obtaining the new machining conditions by successively updating said initial machining conditions;
• and
• control means for controlling the discharge state in accordance with the new machining conditions obtained by said arithmetic processing means.