Response surface methodology based multiresponse optimization of drilling parameters for surface roughness and material removal rate in AA7075T6 aluminium alloy

Abstract

High strength and lightweight alloys like AA7075-T6 Aluminium alloy pose great challenge in drilling, particularly in achieving high surface quality and productivity. The existing work is a systematic investigation of the effect of the cutting speed, feed rate and drill depth on surface roughness and material removal rate (MRR) in conventional drilling. The experimental design was developed based on Response Surface Methodology (RSM) coupled with CCD and 2nd order polynomial regression models were proposed for prediction of the responses. Model reliability was evaluated statistically and was found to be high with high value of coefficient of determination (R² = 0.9731 for SR and 0.9359 for MRR). The ANOVA revealed that the cutting speed and feed rate were the most significant factors for MRR. The results of the confirmation experiments were found to be well correlated with the model-observation results. Two optimal sets of operating parameters were found, one corresponding to minimizing surface roughness with a depth of 15 mm, a feed of 0.20 mm/rev and a speed of 45 m/min, which gave surface roughness of 3.66 μm, and the other, maximizing MRR at 18.04 mm depth, 0.23 mm/rev feed, and speed of 53.92 m/min, with MRR of 417.28 mm³/s. The results provide valuable insight into how to improve drilling practices in the aerospace and structural engineering industries, where precision and performance are critical.