Curved profiles machining of Ti6Al4V alloy through WEDM: investigations on geometrical errors

Abstract

Great biocompatibility and superior mechanical properties of titanium alloys (Ti6Al4V) stimulate the use of this material frequently in biomedical, defence, and aeronautical industries. In these applications, the end parts generally have complex curved profiles. Through conventional means of machining, complex profiles with high dimensional accuracy are not easily achievable due to difficult-to-cut nature of Ti6Al4V. Wire Electric Discharge Machining (WEDM) is a promising alternative to cut the complex features like angular and curved features. In this research, convex and concave profiles are machined in Ti6Al4V through WEDM. The influence of four machining parameters, namely servo voltage, wire feed, pulse On- and Off-time, over the geometrical accuracies of convex and concave profiles along with corner radii have been comprehensively investigated. The L27 orthogonal array was taken as the design of the experiment, and the results are evaluated in terms of statistical (ANOVA and signal-to-noise ratio) and microscopic morphology by Scanning Electron Microscopy (SEM). Optimized combination of machining parameters are sought capable of resulting in minimum geometric deviations (0.250% overcut in convex and 0.236% undercut in concave profiles) and corner radii of 0.106 mm. Moreover, the SEM analysis has confirmed that the discharge energy and erosion phenomenon significantly affect the profile accuracy as well as the surface integrity. In addition to optimized parameters the provision of wire offset, ranging within 0.169–0.173 mm, can further mitigate the geometric deviations of the actual machined profiles from the designed geometries.

Keywords

• Wire electric discharge machining (WEDM)
• Geometrical accuracy
• Ti6Al4V
• Complex profiles
• SEM analysis
• Ti alloys