In Part 1 of this paper a model was developed to describe the formation mechanisms and dynamic behavior of cutting fluid mist. This part of the paper focuses on an experimental investigation of the mist generated by the interaction of the fluid with the rotating cylindrical workpiece during a turning operation and the simulation of the dynamic behavior of the mist droplets, resulting in the prediction of the droplet size distribution and the mass concentration within the machining environment. These simulation results are compared to experimental measurements in order to validate the theoretical model presented in Part 1 of the paper. It is observed that the model predictions accurately characterize the observed experimental behavior.
The copious use of metal working fluids in machining applications carries with it worker health, environmental, and cost concerns. Driven by these concerns, minimum quantity lubrication (MQL) technology has been proposed as an intermediate alternative between flood and dry machining applications. However, widespread use of MQL is inhibited by worries related to unknown costs, thermal distortions, chip flushing problems, flammability of airborne metal dust, and system reliability/repeatability. More information is needed on the effects of lubricant flow rate and droplet characteristics on the cutting performance. One challenge associated with implementing MQL technology has been the difficulty in reconfiguring dedicated transfer line systems. To address some of the above issues, tests have been conducted to investigate the effects of lubricant flow rate and droplet characteristics on cutting performance in terms of cutting force, workpiece temperature, surface finish, and air quality. Comparisons are made among dry, MQL, and fluid flood applications to show that MQL and flood application provide similar benefit in terms of work temperature. Machining cost analysis for both multistage and single-stage operations provides insight into the relative difference between transfer line and FMS machining systems in terms of costs for different fluid applications.
Airborne inhalable particulates in the workplace can represent a significant health hazard, and one of the primary sources of particles is mist produced through the application of cutting fluids in machining operations. One of the principal mechanisms associated with cutting fluid mist formation is atomization. Atomization is studied by applying cutting fluid to a rotating workpiece such as found in a turning process. In order to properly study the atomization mechanism, an imaging system was developed. This system extends the size measurement range typically achievable with aerosol sampling devices to include larger particles. Experimental observations reveal that workpiece rotation speed and cutting fluid flow rate have significant effects on the size of the droplets produced by the atomization mechanism. With respect to atomization, the technical literature describes models for fluid interaction with the rotating workpiece and droplet formation via drop, ligament, and film formation modes. Experimental measurements are compared with model predictions. For a range of rotation speeds and fluid application flow rates, the experimental data are seen to compare favorably with the model predictions.
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