| 摘要 |
PURPOSE:To maintain the resistivity of the working liquid constant, by detecting the resistivity of the working liquid while driving/stopping the pump of an ion exchanger such that the resistivity will be constant while providing an auxiliary ion exchanger. CONSTITUTION:The working liquid is returned from the working section of a wire cut discharge machining machine through a drain lead pipe 11 and stored in a contaminated liquid tank 5. The contaminated liquid is fed through a filter 17 to a filter liquid tank 7 by means of a pump 15. The filter liquid is fed through a piping 13 to the working section by means of a pump 19, but a portion of it is returned through a branch valve 21 and a resistivity detector 23 into the contaminated liquid tank 5. The control circuit 37 drives the pump 25 if the resistivity is lower than the limit value to pass the working liquid through an ion exchanger 27 thus to increase the resistivity, while, when it exceeds predetermined value the pump 25 is stopped. When the performance of the ion exchanger is deteriorated, an auxiliary ion exchanger 29 is added. |
