A new method to efficiently control energy use in Electrical Discharge Machining (EDM)

Abstract

Rationalizing energy consumption in the Electrical Discharge Machining (EDM) efficiently saves energy and improves machining quality. Since the conventional methods for estimating useful EDM energy are based on theoretical heat transfer studies or empirical assessments of processing conditions, the development of an industrially applicable method for assessing useful energy is an important problem. Here we show that the performance of the EDM process is directly related to acoustic emission (AE). The effectiveness of the proposed method has been evaluated in experiments. As part of the execution of the experiment, AlCuMg1 workpiece was machined using a copper electrode with different duty cycles with pulse widths varying from 10% to 80%. For comparative analysis, the root-mean-square vibroacoustic signal in the range of 1-10 kHz and the root-mean-square of the discharge current were used. It was found that the amplitude of the vibroacoustic (VA) signal monotonically increases with the increasing EDM performance. The properties of the VA signal allows using the VA monitoring to assess the performance of EDM, i.e., to determine the fraction of energy spent on removing the workpiece material. The advantage of the proposed method of monitoring is that the control of useful energy is carried out using accelerometers installed on the parts of the technological system on the workpiece side. The distance from accelerometers to the workpiece being processed can be quite large that is convenient for performing experiments. In particular, in the high frequencies range, the obtained results are protected from mechanical interference coming from drives, hydraulic units and wire rewinding mechanisms. Such VA signals are shown to be important indicators of EDM efficiency because they are observed only if the energy fluxes reach the workpiece surface. This provides a more reliable indication of raising concentrations of electroerosion products that prevents short circuits and breakage of wire electrodes.