Multi-response optimization of hard turning parameters: a comparison between different hybrid Taguchi-based MCDM methods

The turning process is one of the fundamental machining techniques and process parameter optimization is very important in manufacturing as it leads to better machining performance without compromising the product quality. An orthogonal Array is employed to evaluate the effects of input parameters on the output parameters. In this study, experiments are carried out based on Taguchi's L-32 orthogonal array considering input process parameters - Cooling environment (Dry and MQL), Cutting speed (70, 100, 130, and 156 m/min), feed rate (0.12, 0.16, 0.2, and 0.24 mm/rev) during hard turning of medium carbon steel. The study aims to find the optimal process parameters for the improvement of machinability in terms of cutting temperature, main cutting force, feed force, surface roughness, and chip reduction coefficient using three different optimization techniques namely Complex Proportional Assessment (COPRAS), Technique for Order of Preference by Similarity to Ideal Solutions (TOPSIS), and Grey Relational Analysis (GRA). Criteria Importance Through Inter-criteria Correlation (CRITIC), an analytical method can be employed to determine the individual importance of each response which facilitates all the optimization techniques. It has been identified that the optimal process parameters obtained from all three methods are the same. The optimal process parameters are the cooling environment of MQL, cutting speed of 156 m/min, and feed rate of 0.12 mm/rev. But among these methods, COPRAS and TOPSIS methods are computationally easy and simple compared to the GRA.