A study on droplets and their distribution for minimum quantity lubrication (MQL)

A better understanding in the application of minimum quantity lubrication (MQL) or near dry machining (NDM) is needed for its effective use in practical industrial applications. This paper presents the combination of confocal laser scanning microscopy (CLSM) and image processing techniques including wavelet transform to characterize the droplet sizes and the droplet distribution after MQL oil has been sprayed onto a polished silicon wafer. The raw droplet topographies captured with CLSM have been wavelet-filtered to purge the noise and artifacts and then the droplets themselves were isolated using wavelets multi-resolution analysis in order to measure the volume of each droplet. In addition, the empirical droplet size estimation equation was introduced for extremely small droplets which are difficult to measure. The distribution of the droplets has been also studied to determine the MQL optimal nozzle-workpiece distance and the nozzle discharge pressure. The procedures developed in this paper can be used to determine optimal conditions for various applications of MQL processes. (C) 2010 Elsevier Ltd. All rights reserved.