Investigations on Distribution of Spark Locations in EDM Process.

This paper describes the observation of spark locations in EDM processes. A new method for the in-process detection of spark locations is proposed in order to obtain the relationship between the process stability and the distribution of spark locations. Each spark location can be obtained from the current ratio of branched electric wires which are connected to the tool electrode by a sufficient distance maintained. From the results of experiments using this method, the following conclusions are obtained : (1) Spark localizations are apt to occur when the eroded depth becomes deeper. (2) The spark localization is caused by the vicious circle which is an iteration of the contamination of dielectric fluid and the reduction of dielectric strength of the fluid. (3) When the eroded depth gets much deeper, the spark localization becomes more serious, and finally an abnormal arc appears.