An experimental study on end milling of titanium alloy (Ti-6Al-4V) under dry and minimum quantity lubrication conditions

Abstract

This paper presents the results of an optimisation study of low speed machining of Ti-6Al-4V alloy by technique of order preference by similarity to ideal solution (TOPSIS). End milling was conducted under dry and minimum quantity lubrication (MQL) conditions and at different levels of cutting speed (20 to 40 m/min), feed (0.05 to 0.15 mm/rev) and axial depth of cut (0.4 to 1.2 mm) using a full factorial design. Machinability was evaluated by measuring surface roughness and cutting forces. The micro-hardness below the machined surface for some selected combinations of cutting conditions was also measured. It was found that the feed per rev and depth of cut have the greatest influence on cutting forces and surface roughness under dry and MQL conditions. The minimum cutting forces and minimum surface roughness are obtainable at cutting speed of 30 mm/min, feed of 0.05 to 0.1 mm/rev and depth of cut of 0.4 mm under MQL condition. It was also found that these conditions result in the minimum alteration of micro-hardness beneath the machined surface.