Characterizing Mist Flow in Minimum Quantity Lubrication Drills

Minimum Quantity Lubrication (MQL) uses a mixture of oil and air in small quantities to effectively lubricate and cool the cutting zone. Because of this small quantities of lubricants being used in the order of 5-100 ml/hr., the control of the flow is a critical parameter. Presently, this control is done by multiple experimentation to find out the optimal conditions. This method though works does not provide enough insight on how each parameter affects the effectiveness of the MQL. Moreover, the flow in MQL is a multiphase flow and thus the distribution of the lubricant might not be homogeneous as expected. A new method is proposed in this article to capture and analyze the flow distribution in through channel drills employing MQL using visible light. The amount of light reflected by the mist particles works as a signal to quantify the amount of mist particles at particular location. Image acquisition at multiple viewing angles was carried out to map flow across channel cross-section. The measurement and analysis process provides data about flow concentration zones in the channel, which help in the design of better cutting tools. The effect of channel shape and the helix angle of the cutting tool; (which controls the helix angle of the channel) on the flow distribution obtained were analyzed. The flow distribution results at the channel exit were compared to the velocity contours at the same location, obtained using CFD simulation, to find out analogy in the flow velocity and flow distribution