Concurrent parametric optimisation of single pass end milling through GRA coupled with PSO for Calmax-635 die steel

The present investigation includes optimisation for enhanced surface quality during finishing of Calmax-635 die steel through GRA coupled with PSO. GRA converts multiple objectives into single objective domain. However, it yields discrete parametric combination within the problem space and fetches quasi-optimal solution. Whereas, PSO obtains optimal solution if the fitness function is available. To obtain the fitness function for Calmax-635 die steel, a full factorial DOE was conducted for parameters like, spindle speed, feed rate and depth of cut all at three levels. With the help of ANOVA, a fitness function was obtained within the problem space. Thus, when PSO was coupled with GRA, the optimised process parameters became 5,660.6 rpm, 579.4 mm/min, 0.105 mm, respectively and the roughness values obtained were 0.862 µm, 6.591 µm and 4.638 µm for Ra, Rmax and Rz, respectively. Therefore, the proposed methodology reveals an avenue for optimisation in absentia of fitness function.