Investigations on the effect of wire EDM process parameters on surface integrity of HSLA: a multi-performance characteristics optimization

Abstract

Surface roughness (Ra) and micro-hardness (μh) are two important constituents of the surface integrity (SI) of the machined component. In Wire Electric Discharge Machining (WEDM), the machining factors that affect SI are generally the pulse on-time, pulse off-time, current, etc. This paper presents a study that investigates the effect of the WEDM parameters on the surface roughness average and the micro-hardness of the High Strength Low Alloy steel (ASTM A572-grade 50). Nine experimental runs based on an orthogonal array of Taguchi method are performed and grey relational analysis (GRA) method is subsequently applied to determine an optimal WEDM parameter setting. The SI parameters i.e. surface roughness and micro-hardness are selected as the quality targets. An optimal parameter combination of the WEDM process is obtained using GRA. By analyzing the grey relational grade matrix, the degree of influence for each controllable process factor onto individual quality targets can be found. The pulse off-time is found to be the most influential factor for both the surface roughness and the micro-hardness. Further, the results of the analysis of variance reveals that the pulse off-time is the most significantly controlled factor for affecting the SI in the WEDM, according to the weighted sum grade of the surface roughness and the micro-hardness.