Numerical analysis of the effect of air pressure and oil flow rate on droplet size and tool temperature in MQL machining

Abstract

Dry machining is undesirable for machining of good surface quality products, because the thermal properties of a material may contribute to a reduction of tool life when machining difficult to cut materials. Likewise, the conventional lubrication through a jet or flood cooling is not economical or eco-friendly and increases the environmental burden. Owing to the above facts it becomes necessary to implement Minimum Quantity Lubrication (MQL) in end milling process. In this study, a numerical analysis has been carried out to investigate the impact of compressed air pressure and the oil flow rate on Sauter mean diameter of MQL spray and on tool temperature. Sauter Mean Diameter (SMD) of MQL spray and temperature distribution in the end milling tool are calculated for three different air pressure (2, 3, and 4 bar) and oil flow rate (100, 150, and 200 ml/hr). ANSYS Fluent software is used for the analysis with discrete phase model (DPM) for predicting the spray particle size. From the analysis, SMD and tool temperature are found to decrease with increase in air pressure for constant oil flow rate whereas there is no considerable change in SMD as the flow rate of oil is changed beyond 150 ml/h. This study has been used for selecting the optimum air pressure and flow rate of the oil for efficient lubrication and cooling in MQL aided machining.