Multi-objective optimization of machining parameters of mild steel AISI 1018 under compressed air-assisted cooling by using genetic algorithm

Large amounts of heat are produced during the machining process, and to remove this heat, cutting fluids or suitable cooling agents must be used. However, both methods are wasteful and harmful to the environment. In response to these issues with cutting fluids, researchers have developed innovative techniques such as dry machining, MCL, compressed air-assisted machining, and cryogenic machining. In line with this, the present work aims to identify four optimal combinations of input parameters based on production requirements, rather than simply finding a single optimal solution during air-assisted turning. The key turning parameters include cutting speed, feed rate, and tool overhang. These parameters were examined using a Taguchi L9 experimental design to determine their effects on material removal rate (MRR) and surface roughness (Ra) when turning AISI 1018 steel. Increasing cutting speed from 56 to 76 m/min and from 76 to 96 m/min, the MRR increased by 22.83% and 15.43%, respectively. Increasing feed from 0.1 to 0.14 mm/rev and from 0.14 to 0.18 mm/rev, the MRR increased by 20.64% and 15.75%, respectively. However, increasing tool overhang from 40 to 50 mm and from 50 to 60 mm, the MRR decreased by 7.34% and 12.41%, respectively. The surface roughness investigation showed that increasing the cutting speed from 56 to 76 m/min and from 76 to 96 m/min, reduced the Ra value by 31.92% and 40.71%, respectively. However, increasing the feed from 0.1 to 0.14 mm/rev, and from 0.14 to 0.18 mm/rev, the Ra value increased by 16.95% and 9.92%, respectively. Similarly, an increment on tool overhang from 40 to 50 mm, and from 50 to 60 mm resulted in increments on Ra values of 11.11% and 6.4%, respectively. Additionally, a genetic algorithm was employed to conduct multi-objective optimization of output process parameters, aiming to simultaneously maximize MRR and minimize Ra. Accordingly, the following four optimal points have been obtained respect to cutting speed (m/min), feed (mm/rev), and tool overhang (mm): (i) 93.555, 0.1, 41.701; (ii) 91.302, 0.1, and 42.024; (iii) 90.184, 0.1, and 45.285; and (iv) 93.021, 0.1, and 53.829. This research is expected to help researchers and industrial practitioners improve the use of mild steel (AISI 1018) through compressed air-aided cooling and to better control and optimize the parameters before machining.