Classification and comparative study of EDM pulse generators

Abstract

Electrical discharge machining (EDM) is a non-conventional machining technique that requires pulse generators to create sparks between the tool and the workpiece. Classical texts describe only two types of EDM pulse generators (EPGs), although there are several different types. This work presents a classification and detailed comparative study of 13 important EPG topologies from the power electronics perspective. The operation of each topology is explained using simulation studies for EDM load with spark current of 10 A and pulse repetition frequency of 1 kHz. Control schemes of each topology are explained from the viewpoint of mechanical performance parameters, viz. material removal rate, surface finish, and tool electrode wear ratio. A general analytical methodology to compute efficiency based on machining duty is illustrated considering the existence of two distinct switching frequencies. Overall comparison between EPG topologies is presented considering control aspects, size, efficiency, voltage stresses and suitability for any required application. As an example, a case of investigation of cutting silicon ingots with wire EDM is considered and experimental results are provided for the same. This work can be used as a guideline to understand and develop EPG based on particular target specifications.