materials Article Optimization of Process Parameters in CNC Turning of Aluminum 7075 Alloy Using L27 Array-Based Taguchi Method Mohammad Nishat Akhtar 1 , T. Sathish 2 , V. Mohanavel 3 , Asif Afzal 4 , K. Arul 5 , M. Ravichandran 6 , Inzarulfaisham Abd Rahim 7 , S. S. N. Alhady 8, *, Elmi Abu Bakar 1, * and B. Saleh 9   Citation: Akhtar, M.N.; Sathish, T.; Mohanavel, V.; Afzal, A.; Arul, K.; Ravichandran, M.; Rahim, I.A.; Alhady, S.S.N.; Bakar, E.A.; Saleh, B. Optimization of Process Parameters in CNC Turning of Aluminum 7075 Alloy Using L27 Array-Based Taguchi Method. Materials 2021, 14, 4470. https://doi.org/10.3390/ma14164470 Academic Editor: Tomasz Trzepieci´ nski Received: 22 June 2021 Accepted: 28 July 2021 Published: 10 August 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 School of Aerospace Engineering, Universiti Sains Malaysia, Nibong Tebal 14300, Penang, Malaysia; nishat@usm.my 2 Department of Mechanical Engineering, Saveetha School of Engineering, SIMATS, Chennai 602105, Tamil Nadu, India; sathish.sailer@gmail.com 3 Centre for Materials Engineering and Regenerative Medicine, Bharath Institute of Higher Education and Research, Chennai 600073, Tamil Nadu, India; mohanavel2k16@gmail.com 4 Department of Mechanical Engineering, P. A. College of Engineering, Visvesvaraya Technological University, Belagavi 574153, Mangaluru, India; asif.afzal86@gmail.com 5 Department of Mechanical Engineering, Jeppiaar SRR Engineering College, Chennai 603103, Tamil Nadu, India; arul.phd2014@gmail.com 6 Department of Mechanical Engineering, K Ramakrishnan College of Engineering, Trichy 621 112, Tamil Nadu, India; smravichandran@hotmail.com 7 School of Mechanical Engineering, Universiti Sains Malaysia, Nibong Tebal 14300, Penang, Malaysia; inzarul@usm.my 8 School of Electrical and Electronic Engineering, Universiti Sains Malaysia, Nibong Tebal 14300, Penang, Malaysia 9 Mechanical Engineering Department, College of Engineering, Taif University, P.O. Box 11099, Taif 21944, Saudi Arabia; b.saleh@tu.edu.sa * Correspondence: sahal@usm.my (S.S.N.A.); meelmi@usm.my (E.A.B.) Abstract: With the advent of the industrial revolution 4.0, the goal of the manufacturing industry is to produce a large number of products in relatively less time. This study applies the Taguchi L27 orthogonal array methodological paradigm along with response surface design. This work optimizes the process parameters in the turning of Aluminum Alloy 7075 using a Computer Numerical Control (CNC) machine. The optimal parameters influenced the rate of metal removal, the roughness of the machined surface, and the force of cutting. This experimental investigation deals with the optimization of speed (800 rpm, 1200 rpm, and 1600 rpm) and feed (0.15, 0.20, and 0.25 mm/rev) in addition to cutting depth (1.0, 1.5, and 2.0 mm) on the turning of Aluminum 7075 alloy in a CNC machine. The outcome in terms of results such as the removal rate of material (maximum), roughness on the machined surface (minimum), along with cutting force (least amount) were improved by the L27 array Taguchi method. There were 27 specimens of Al7075 alloy produced as per the array, and the corresponding responses were measured with the help of various direct contact and indirect contact sensors. Results were concluded all the way through diagrams of main effects in favor of signal-to-noise ratios and diagrams of surfaces with contour diagrams for various combinations of responses. Keywords: Al7075; turning parameters; Taguchi method; L27 array; signal to noise ratio 1. Introduction and Background In the current market competition, industrial sectors are focusing on high production with minimum cost. Especially, manufacturing industries are concentrating on a variety of products in batch production. Nowadays, composites have found a wider use of materials in most of the top leading manufacturing sectors. Machining is the essential choice to produce the components with closer tolerances. The second generation of hybrid com- posites is found in many engineering fields and acts as a better alternative for numerous Materials 2021, 14, 4470. https://doi.org/10.3390/ma14164470 https://www.mdpi.com/journal/materials