Characterization of fluid film produced by an atomization-based cutting fluid spray system during machining

The atomization-based cutting fluid (ACF) spray system has recently been proposed as a cooling and lubrication solution for machining hard to machine materials (e.g., titanium alloys). On the tool rake face, the ACF spray system forms a thin film from cutting fluid that penetrates into the tool-chip interface to improve tool life. The objective of this work is to characterize this thin fluid film in terms of thickness and velocity for a set of ACF spray parameters. ACF spray experiments are performed by varying impingement angle to observe the nature of the spreading film and to determine the film thickness at different locations after impingement of the droplets. It is observed that the film spreads radially outward producing three fluid film development zones (i.e., impingement, steady, and unsteady). The steady zone is found to be between 3 and 7 mm from the focus (impingement point) of the ACF spray for the set of parameters investigated. An analytical 3D thin fluid film model for the ACF spray system has also been developed based on the Navier-Stokes equations for mass and momentum. The model requires a unique treatment of the cross-film velocity profile, droplet impingement, and pressure distributions, as well as a strong gas-liquid shear interaction. The thickness profiles predicted by the analytical film model have been validated. Moreover, the model predictions of film velocity and chip flow characteristics during a titanium turning experiment reveal that the fluid film can easily penetrate into the entire tool-chip interface with the use of the ACF spray system.