| 摘要 |
PURPOSE:To detect abnormality of a tool electrode when the tool electrode is automatically replaced, by comparing a detected position of electric discharge machining start with its predetermined value and generating an output signal when a difference not less than a fixed value is detected. CONSTITUTION:When tool electrodes 2-5 are replaced, a numerical control device 14 inputs expected position information of a main shaft 8 at the time of electric discharge machining start to a memory 22 in an electrode abnormality detecting device I. The tool electrode is replaced, then a main shaft is moved and lowered by a command from the numerical control device, if electric discharge is initially caused between the electrode and a machined body 6, output of a main shaft position indicating transmitter 9 is both input to a memory 21 and compared in a comparator 23 with the expected value of the memory 22, when its difference is not less than a permissible value the numerical control device is allowed to cease machining operation. The electrode abnormality detecting device I can also balance the length with each other in combination use of backup electrode abnormality detecting devices II, III having different characteristics. |
