Development of continuous flow magnetorheological fluid finishing process for finishing of small holes

Abstract

The objective of the present experimental study is to find competency of magnetorheological fluid finishing process in improving the finishing and dimensional accuracy of miniature holes drilled by the electro-discharge drilling process. For this, holes of 2.0 mm diameter, drilled in aluminium 6063 alloy-based metal matrix composite, is finished using indigenously developed magnetorheological fluid finishing set-up. The input parameters of the process, viz. supply current, MR fluid flow rate, finishing time and pole geometry, are optimized for machining characteristics, viz. average surface roughness height (Ra, µm) and Taper (TAP, degree). Experiments are carried out which are based on the Taguchi experimental design L16 orthogonal array. Grey relational analysis (GRA) is further carried out to obtain the combination of the input machining parameters for optimizing both the response characteristics simultaneously. From GRA, it is found that higher values of supply current, fluid flow rate and finishing time with flat pole geometry have generated optimal machining performance characteristics and the most influential controllable factor is the finishing time. Microscopic analysis is performed using field emission scanning electron microscope and atomic force microscope on the surfaces of holes before and after MR fluid finishing operation. The results have shown that the developed MR fluid-based finishing process significantly enhances the characteristics of holes. The surface roughness from a region of unfinished hole is found to be 5.4 µm, whereas it is in nm range for the finished surface.