Optimization of Cutting Forces in Hard Turning of AISI 420 Steel Using Grey Relational Analysis

This paper presents a multi-response optimization of cutting forces in the hard turning of AISI 420 stainless steel using Grey Relational Analysis (GRA). Machining experiments were performed on a CNC lathe by varying cutting speed and feed rate, while keeping the depth of cut constant. The three components of cutting forces—feed, tangential, and radial were measured. GRA approach was employed to convert the multi-response problem into a single optimization index. Experimental data were normalized and Grey Relational Coefficients (GRC) and Grades (GRG) were computed to evaluate overall performance. The optimal parameter setting was determined based on the maximum GRG. The results indicate that feed rate is the most influential parameter affecting cutting forces, followed by cutting speed. The optimal machining conditions significantly reduce cutting forces, improving machining performance. The proposed methodology proves to be an effective tool for multi-objective optimization in hard turning processes.