This article provides an improved lubrication system for minimum quantity lubrication machining wherein oil is locally supplied and individually controlled at different heating zones during machining operation. The proposed lubrication method, that is, a multi-point minimum quantity lubrication system, is aimed at improving energy efficiency and environmental friendliness of cutting process. An experimental system is devised in which process parameters, such as air pressure, stroke volume (i.e. amount of oil in one stroke of pump), stroke frequency, and oil distribution factor (i.e. proportion of oil at rake and flank face), are individually controlled for each supply system. The devised system is demonstrated through machining of Ti-6Al-4V. The results of the experimental study on effects of oil quantity and supply method on specific cutting energy, tool wear, and machined surface quality are presented and discussed and corroborated with scientific evidence. The study suggests that distributing oil at the rake face and the flank face in unequal proportions can be more beneficial than injecting it solely at a single location. The investigation also provides mechanism of multi-point minimum quantity lubrication machining through analysis of adiabatic shear zones, observed in scanning electron microscope images of chips.
