Sustainable production of high-uniformity workpiece surface quality in wire electrical discharge machining by fabricating surface microstructure on wire electrode

Abstract

When the traditional wire electrode is used in wire electrical discharge machining (WEDM), the workpiece surface quality along thickness direction is always nonuniform which has a significant impact to the usability and reliability of workpiece. To address this issue, this paper aims to propose a new method of fabricating surface microstructure on wire electrode (SMWE) for sustainable production of high-uniformity workpiece surface quality. Firstly, an experimental research of workpiece surface quality uniformity is implemented when zinc coated wire electrode (ZCWE) is used. It can be found that the surface roughness (Ra) and surface quality on the middle area are the worst followed by the top area and bottom area. The uniformity of Ra can be up to 0.44. Additionally, the production process of SMWE is described which includes casting, coating, annealing and plastic processing. The forming mechanism of surface microstructure on wire electrode is based on the thermal expansion coefficient of coating layer is lower than that of wire core. And then, compared with ZCWE, the improvements of SMWE on the discharge characteristic and workpiece surface quality uniformity are analyzed. It can be obtained that SWEM can increase the probability of point discharge and the ratio of normal discharge status. Besides, SMWE can reduce the mean value of surface roughness by 17.3%–22.2% and increase the uniformity of surface roughness by 9.5%–52.1%. Namely, the proposed SMWE for sustainable production of high-uniformity workpiece surface quality is feasible. Eventually, the effects of process parameters on the uniformity of surface roughness are also analyzed. It can be found that small discharge peak current, short pulse on time, long pulse off time, high gap reference voltage and appropriate wire speed are recommended for high-uniformity surface quality.