During minimum quantity lubrication (MQL) cutting processes, the coverage rate of the oil droplet, as well as the droplet size and its distribution at the tool-chip and tool-workpiece interfaces are the important factors influencing the oil film uniformity and oil coverage area at the cutting zone, which then directly determine the lubricating performance of the lubrication oil. The coverage rate of the oil droplet is investigated, as well as the droplet size and its distribution under different spray distance and air flow rate. First, by means of image processing technology, the bitmap images of the oil droplets under different spray distance and air flow rate are obtained, and the effects of droplet shape and spray distance on the coverage rate of the oil droplet is analyzed. Then, the relationship between the oil droplet size distribution and the air flow rate are explored by aid of the mathematic model of the oil droplet volume. The results indicate that the combination of properly shortening the spray distance and increasing the air flow rate is benefit to increasing the coverage rate of the oil droplet, and reducing the droplet size, and then improving the lubrication performance of MQL technology.
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