Drilling of Titanium Alloy (Ti6Al4V) using Response Surface Methodology: An Experimental Approach

Titanium alloy is often regarded as a difficult to machine material due to its high strength to density ratio and low thermal conductivity. This challenge often results in tool wear, surface and dimensional irregularities amongst others. This study investigates the dimensional accuracy of drilled holes for Ti-6Al-4V. The study employs the Response Surface Methodology (RSM) as the Design of Experiment (DoE) and the feasible combination of the process parameters namely drilling speed (within the range of 300-500 m/min) and drilling feed (within the range of 25-45 mm/min) obtained from the RSM was validated through physical experimentation (deep drilling of Ti6Al4V). The deep drilling operations were carried out on a solid cylindrical shaft of titanium alloy Ti-6Al4V using a 5-axis, DMU 80 monoblock DECKEL MAHO CNC milling machine and 13 pieces of 10 mm diameter drill bits made from HSS Co. The Cyclone Scanning Machine (SCM) was used to measure the deviations of the drilled hole from the pre-determined locations Furthermore, a predictive model was generated for the prediction of the deviations during the deep drilling of Ti6Al4V under similar process parameters. The results obtained indicated the combination of the process parameters that produced the least deviation (0.073 mm) are drilling speed of 436 m/min and drilling feed of 25 m/min. Although, there was evidence of high rate of tool wear when drilling at high speeds and feeds. Thus, the need for the optimization of the process parameters. The empirical findings presented in this study can assist drilling operators in obtaining accurate holes during deep drilling of Ti6Al4V.