Study on Characteristic of Multi-spark EDM Method by Using Capacity Coupling

In order to obtain higher removal rates, this paper developed a multi-spark EDM method by using a capacity coupling. In this method, the tool electrode was divided into multiple tool electrodes, which were electrically insulated from each other. Each tool electrode was coupled by capacity in series with an isolating capacitance and the workpiece (The workpiece here is common for each electrode), forming multiple parallel discharge gaps. A pulse generator was coupled to all the discharge gaps by the feeding capacitance. For shorting the balance restoring time of discharge circuits while discharge is generated in a discharge circuit, the compensating capacitance was connected in parallel with the pulse generator. Compared with conventional EDM in which only a singular discharge can be generated for each pulse, multiple discharges can dispersively be generated for each pulse in multi-spark EDM. In this study, to examine the characteristic of multi-spark EDM method, theoretical analysis and circuit simulation were conducted. The multiple discharges phenomenon was verified, and it can be known the removal rate can be improved by increasing the compensating capacitance, and the larger ratio of feeding capacity and isolating capacity is more conducive to the occurrence of multi-spark. Then the influence of the divided electrodes number on the characteristic of multi-spark EDM was investigated by experiment, it can be known the removal rate increased as the number of electrodes increased.