Surface burn prevention based on the probability control of pulses with ignition delay in WEDM

Abstract

This study aims to address surface burn and increased probability of wire breakage under high-energy cutting conditions in wire electrical discharge machining (WEDM). Firstly, the causes of surface burns are investigated, revealing that the deterioration of cooling, debris removal, and deionization status in the machining gap are the dominating factors. Maintaining a certain ratio of pulse to ignition delay is essential for proper discharge machining. Secondly, a servo control strategy based on the pulse probability of ignition delay is proposed. When the target probability is preset to 25%, the machining stability is significantly improved, preventing surface burns and decreasing the probability of wire breakage. With this servo control, the maximum average machining current free of surface burn is raised from 6 to 8 A. As a result, the max cutting speed is improved by 24%, and the tensile strength of the wire electrode is enhanced by 23.5%. In addition, the machined surface area increases by 22% when the diameter wear of the wire electrode reaches 0.01 mm. The new servo control has been demonstrated to be effective in facilitating machining efficiency and extending wire electrode durability in WEDM.