Modelling and multi-objective optimization of surface roughness and kerf taper angle in abrasive water jet machining of steel

Abrasive water jet machining (AWJM) is a popular method used for cutting purposes. It uses a thin jet of ultra-high pressure water and abrasive slurry to cut the material and the cutting is mainly by erosion. The purpose of this paper is to investigate the effect of AWJM parameters on the cutting of mild steel and to optimize the process parameters. The process parameters considered for investigation are traverse speed, abrasive flow rate and standoff distance. The subsequent response parameters that have been determined are surface roughness and kerf taper angle. Taguchi L 9 orthogonal array has been used to design the experiments. ANOVA is used to decide the influencing process parameters. 3D surface plots are presented for interaction effects of input process parameters. The study revealed that traverse speed is the prime factor influencing surface roughness and kerf taper angle followed by stand-off distance and abrasive flow rate. Response models are verified on the basis of estimation capability. Later on, multi-objective optimization using response surface methodology has been used for minimizing surface roughness and kerf taper angle which further resulted in composite desirability of 0.9497. The optimum values of abrasive flow rate, standoff distance and traverse speed are found to be 420 g/min, 3 mm and 85 mm/min, respectively. To validate the results, confirmation test is performed using optimum cutting parameters. It showed 9.17 and 8.57% error for surface roughness and kerf taper angle.