Direct Observation of Spark Locations in Fine Wire EDM Using High-speed Camera

In fine wire EDM using a thin wire electrode for relatively thin workpiece, it is important to evaluate spark distribution state accurately, since the distribution state greatly influences the machining performance. However, it is difficult to measure the spark locations on the order of sub-millimeter by conventional methods, such as branched electric current method. In this study, a new method to measure spark locations by direct observation from the side with a high-speed camera was proposed for accurate evaluation of the spark locations distribution. In order to confirm the advantage of the new side observation model, the number of spark observed with this model was compared with that by the conventional back observation model. Then, the influences of machining conditions on the spark locations distribution were investigated and discussed.