Relationship between applied voltage and current waveform in electrochemical discharge machining

Abstract

Electrochemical discharge machining (ECDM) is a machining method for inorganic insulators. When a tool electrode is fed at a constant rate, the removal rate is often decreased due to enlarging the gap length between the tool electrode and workpiece. In this paper, the effects of the applied voltage, which is a changeable condition during ECDM, and the initial gap length between the tool electrode and workpiece on the current waveforms and machining performance were experimentally investigated. Soda lime glass was machined with a tungsten electrode in NaCl solution. Plenty amount of bubbles were generated below an applied voltage of 45 V, and the removal amount was large. Though discharge strongly occurred over 50 V, the removal amount was small. With an increase of the applied voltage, lower frequency components of the current measured during ECDM were decreased. The initial gap did not affect the current waveforms. The mixture of long and short pulses accelerated removal at a low applied voltage. The phenomena around the tool electrode such as the bubble generation and discharge were distinguished by the principal component analysis (PCA). After a series of current pulses was divided into 12 periods, their statistical parameters were calculated, and the frequency components were calculated by the first Fourier transform. In both the cases, the applied voltage was distinguished by the PCA. The principal components obtained from the statistical parameter performed as essential parameters.