Optimization of surface roughness in an end-milling operation using nested experimental design

This paper presents an experimental study to optimize the surface quality of an end-milled surface on a Vertical Machining Centre using Taguchi’s nested experimental design. The effect of various machining parameters on surface roughness was investigated on two different work piece materials, Aluminium alloy and Plain Carbon Steel. Other control factors, namely, feed rate and spindle speed, depth of cut and radial engagement of tool were varied in the experiment to measure surface roughness at four different positions on the work piece. Position was taken as an uncontrollable noise factor. Depth of cut was observed to be the most significant factor that affecting the surface roughness. Also, better surface finish was obtained while machining aluminum alloy as compared to plain carbon steel. Spindle speed and feed rate were the other two significant factors while machining aluminum alloy parts, although these factors did not significantly affect the finish for steel. Radial engagement of tool had no impact on the surface finish for aluminium alloy, while it had a significant impact for plain carbon steel. Further, the analysis of results shows that position P2 (middle of the milled surface) had the best surface finish while position P1 (at beginning of the cut) had relatively poorer finish.