PARAMETRIC OPTIMIZATION OF CHEMICAL ASSISTED BALL END MAGNETORHEOLOGICAL FINISHING OF AL7075

Abstract

The pursuit of precision and efficiency in manufacturing processes has driven the development of novel techniques to improve surface quality and reduce surface roughness in various industrial applications. This research explores the minimization of surface roughness induced after the surface grinding process on aluminium 7075 alloy (Al7075) workpiece surface through finishing with Ball End Magnetorheological Finishing (BEMRF) and Chemical Assisted Ball End Magnetorheological Finishing (CA-BEMRF). The experiments were conducted on Al7075 workpiece surface using BEMRF and CA-BEMRF at same process parameters then percentage reduction in surface roughness (%ΔRa) was calculated. It has been observed that %ΔRa obtained by finishing with CA- BEMRF was found better as compared to BEMRF process at same process parameters emphasizing the significance of chemical assistance. To gain a comprehensive understanding of the processes and effect of their parameters, a statistical analysis using ANOVA was performed. The results indicated that the combined impact of magnetizing current and rotational speed of the tool, the combined effect of the rotational speed of the tool and the working gap, as well as the individual effects of magnetizing current, rotational speed of the tool, and working gap, were all found to be significant in the BEMRF process. The investigation revealed that the maximum predicted percentage reduction in surface roughness after BEMRF (%RSRB) process of 43.67% was achieved at 3.5A magnetizing current, 450rpm rotational speed of the tool, and a 0.5mm working gap. xix The statistical analysis was also performed for CA-BEMRF process. It was found that the maximum predicted percentage reduction in surface roughness after CA-BEMRF (%RSRC) process was obtained as 54.871% at a chemical composition of 8pH, 3.5A magnetizing current, 300rpm rotational speed of the tool, and a 0.5mm working gap. The analysis also highlighted the varying contributions of the input parameters, with the magnetizing current being the most significant contributing factor of 59.55%, followed by the working gap at 10.64%, rotational speed of the tool at 6.8%, and chemical composition at 3.77%. One of the key findings of this research was the successful implementation of the CA-BEMRF process by conducting the experiments at optimum process parameters at 3.5A magnetizing current, 300rpm rotational speed of the tool, and a 0.5mm working gap with chemical composition of 8pH, resulting in a remarkable 55.91% reduction in surface roughness which is closely matched to predicted maximum percentage reduction in surface roughness of 54.871%, with a percentage error of 1.8%. These results underline the practical applicability and reproducibility of CA-BEMRF process for achieving a high- level surface finish on Al7075 workpiece surface. To visualize and quantify the changes in the surface characteristics, scanning electron micrograph (SEM) of grinded surface and finished with CA-BEMRF process at optimum process parameters of 3.5A, 30m/min, 0.5mm and 700rpm using chemical composition of 8pH were captured. The micrograph of the initial grinding surface exhibited pronounced surface irregularities with a multitude of grinding marks. In stark contrast, the images post CA-BEMRF process revealed a vastly improved surface finish, characterized xx by reduced grinding marks and smaller surface irregularities, resulting in a more uniform and refined appearance. Further examination of the surface at a finer scale was conducted through atomic force micrograph (AFM) analysis. This revealed a reduction in the density of surface "lays" from 0.558 (/μm²) to 0.301 (/μm²) after the CA-BEMRF process at optimum parameters, indicating a significant improvement in surface texture. The mean height of peaks decreased from 5.4541 (º) to 4.745 (º), confirming the attainment of a smoother and more homogeneous surface. The surface texture after CA-BEMRF, performed at optimum process parameters, exhibited finer lays compared to the initial grinded surface, thereby validating the effectiveness of the CA-BEMRF process in enhancing surface quality.