| 摘要 |
PURPOSE:To obtain an optimum and stable electric discharge machining state at all times, by detecting the time when the tip of an electrode has passed through a material to be machined, based on a servo voltage change pattern and an electrode moving speed, so that the machining is automatically completed. CONSTITUTION:To detect electrically the servo voltage change pattern, a servo voltage detecting apparatus 18, a converter 36 and a servo voltage change pattern judging circuit 38 are provided. The apparatus 18 detects an average voltage of the gap, and the detected servo voltage is desirably converted by the converter 36, and is fed to the circuit 38. The circuit 38 has previously stored a servo voltage change pattern, the stored pattern and the actual servo change pattern are compared, and a preset signal is outputted for a prescribed servo voltage change pattern. By the output signal the time when piercing has been done can be electrically detected. |
