Optimization of drilling parameters in vertical machining centre drilling on magnesium AZ91D alloy under dry condition with Taguchi design

Abstract

Drilling using a Vertical Machining Centre (VMC) remains a prevalent machining technique, even if current metal cutting processes have improved. Drilling settings on a VMC are optimized using the Taguchi technique to minimize surface roughness, hole diameter, and circularity error roundness test in this experimental investigation. In order to obtain the optimum process parameters in the VMC drilling on Magnesium AZ91D Alloys, L16 orthogonal arrays was formed by changing the four different speed, feed and end point angle. In the trials, an AZ91D alloy was employed and a variety of process factors, like drilling speed (250, 350, 450 and 550 rpm), feed rate 0.025, 0.05, 0.075 and 0.1 mm/rev), and end point angle (55, 75, 95 and 118°) were examined. Experimental results shows that a combination of slow speed (250 rpm), higher feed (0.1 mm/rev), and a medium end point angle (75°) resulted in the lowest roughness average value. It was possible to achieve the hole diameter accuracy by using the parameter at higher speed (450 rpm), higher feed (0.1 rev/min) and an end point angle of 118°. The lowest possible cylindricity error was perceived at 250 rpm speed, 0.01 mm/rev feed and 118° end point angle respectively. The lowest possible roundness error was perceived at 250 rpm speed, 0.05 mm/rev feed and 118° end point angle respectively. It was noticed from this experimental study and Taguchi technique, the surface roughness of the drilled hole is greatly affected by speed, feed and end point angle of the drill bit tool. Lower magnitude of drill tool speed and lower end point angles cause the good surface roughness values rather than the higher magnitude. The drilled hole’s diameter accuracy is significantly influenced by lower tool speed, higher feed rate and higher end point angle of the drill bit tool. The lower tool speed and higher end point angle of the drill bit tool are the two major factors, which are influenced the minimum cylindricity and roundness errors. It was observed from this experimental study, the lower drill bit tool speeds, higher tool feeds and higher end point angles are the important factors, which are significantly affected the quality of the drill holes during the machining of Magnesium AZ91D alloy in Vertical Machining Centre ((VMC) under dry conditions.