Metalworking fluid mist characterization for the milling process

A project was completed to study the spray produced when wet horizontal facemilling with a soluble metalworking fluid. This was done in the effort to define parameters necessary for the design of efficient close capture systems. Characterization of the spray was performed using 4 optical methods. Different test conditions were studied that included variations on the (1) coolant flowrate, (2) cutter peripheral speed, (3) fluid viscosity, and (4) cutter surface topography. Significant spatial variations were found throughout the sprays, with the higher number fluxes found more to the rear face of the cutter. This was due to the location of the impingement point of the coolant onto the cutter and due to the cutter acting like a fan, pumping the air and the small drops to the rear of the cutter. It was concluded for low flowrates that the best place for an exhaust hood is in the rear of the process due to the concentration of small drops and the high number fluxes near the back face of the cutter. It was also concluded for low flowrates that the extent of the fine spray able to traverse into the environment was only a 3.81 cm x 5.08 cm (1.5&inches; x 2&inches;) area. The significant effects of the test parameters on drop size distributions, velocity distributions, number fluxes, and mist generation area were due to (1) the increase in cutter peripheral speed, which acted to produce smaller drops with a higher velocity, (2) the increase in coolant viscosity which acted to produce larger drops, and (3) the change in surface topography, which resulted in a larger mist generation area.; A Computational Fluid Dynamics model of the MWF spray in the vicinity of a slot hood was developed for the low flowrate high cutter peripheral speed condition. The initial exhaust rate of the slot hood in the model was that calculated from a widely accepted formula in industry for slot hood exhaust rates. It was found that the exhaust rate predicted by the formula was 60% higher than that required to pick up the very small MWF drops.