Experimental Research on Surface Quality of Titanium Rod Turned by Wire Electrical Discharge Turning Process

This paper reports the surface quality of a miniature cylindrical titanium rod/bar (MCTB) turned by the wire electrical discharge turning (WEDT) process using a zinc-coated wire of 250 µm diameter. The surface quality was mainly evaluated by considering the very important surface roughness parameters, i.e., the mean roughness depth. A Box–Behnken design (BBD) of the response surface methodology (RSM) based on 17 experimental runs was conducted, where the spark duration “T_on” was found as the most influential parameter affecting the mean roughness depth “R_Z” of the miniature titanium bar. Further, using the grey relational analysis (GRA) technique of optimization, we obtained the least value of “R_Z” 7.42 µm after machining a miniature cylindrical titanium bar with the optimum combination of WEDT’s variable parameters: T_on—0.9 µs, S_V—30 V, and DOC—0.35 mm. This optimization led to a 37% reduction in the surface roughness R_z of the MCTB. The tribological characteristics of this MCTB were also found favorable after conducting a wear test. After completing a comparative study, we can claim that our results are better than those of the past research conducted in this area. The findings of this study are beneficial for the micro-turning of cylindrical bars made from a variety of difficult-to-machine materials.