Discharge state identification and servo control method of high-speed reciprocating microwire-EDM
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ORIGINAL ARTICLE
Discharge state identification and servo control method of high-speed reciprocating microwire-EDM Ming Zhang 1 & Zhidong Liu 1 & Hongwei Pan 1 & Cong Deng 1 & Mingbo Qiu 1 Received: 10 March 2020 / Accepted: 9 November 2020 # Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract The electrical resistance of wire electrode increases with the decrease of the wire diameter. It is difficult to use the voltage threshold method to distinguish the spark and short-circuit states according to the discharge voltage, so it cannot meet the requirements of normal machining. In this study, a gap discharge state identification and servo control method based on discharge current are proposed in high-speed reciprocating microwire-EDM. The synchronous pulse can improve the stability of the system by reducing the disturbance of the discharge frequency and deionization. The experimental results show that a high wire speed is beneficial to the introduction of dielectric and the removal of erosion particles. When the target probability is set at 90%, the processing stability is higher. By using Φ 0.08 mm molybdenum wire electrode, the stable cutting of a 1250 height-diameter ratio (the ratio of cutting height to electrode wire diameter) workpiece is realized with an average cutting efficiency of 32.08 mm2/min. This study is a useful exploration of the machining of high height-diameter ratio workpieces by using a microwire electrode in high-speed wire-cut electrical discharge machining (HSWEDM). Keywords High-speed reciprocating traveling . Microwire electrode . Gap discharge state identification . Height-diameter ratio
1 Introduction To meet the machining requirements of the narrow slots of microparts, such as micromotor cores, microgear, and the lead frame die in the IC industry wire-cut electrical discharge machining (WEDM) requires the use of wire electrode with smaller wire diameter (less than Φ 0.08 mm) for precision machining. However, the process of WEDM discharge is complex, stochastic, and time-varying. Therefore, the identification and control of the discharge state between electrodes is very important for the machining stability and has become a research hotspot. To prevent wire breakage and improve machining efficiency, Rajurkar et al. [1] proposed an online monitoring system based on the analysis of the relationship between wire breakage and discharge frequency. Liao et al. [2] used power consumption and short-circuit rate as control parameters for the design of a fuzzy controller and maintained high stability and machining efficiency due to good transient and steady-state * Zhidong Liu [email protected] 1
College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
responses. Yan et al. [3] designed a pulse identification control system based on the characteristics of an interelectrode voltage waveform. Based on the analysis of the effects of discharge frequency, feed speed, and workpiece thickness on the proportion of each d
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