| 摘要 |
PURPOSE:To obtain an optimum and stable electric discharge machining state all the time so as to increase the accuracy of the shape of a machined hole, by detecting the time when the tip of an electrode has pierced a material to be machined, based on the deepest machining and a rate of movement of the electrode. CONSTITUTION:To detect electrically whether it is the deepest machining or not, an electrode position detecting apparatus 30 and a deepest machining discriminating circuit 33 are provided. The apparatus 30 detects the position of the electrode, and the position signal is fed to the deepest machining discriminating circuit 33 which outputs a signal ''H'' when it is the deepest machining. To detect electrically the rate of movement of the electrode, the electrode position detecting apparatus 30 and an eletrode moving rate discriminating circuit 35 are provided. When piercing has been done, since the output from the deepest machining discriminating circuit 33 is ''H'', and the output signal from the electrode moving rate discriminating circuit 35 is ''H'', an AND circuit 40 feeds a stopping signal to an electric source unit 16 to cut off the power source to complete the machining. |
