Measurement of Droplet Size and Distribution for Minimum Quantity Lubrication (MQL)

Cutting fluid in machining is important due to their role in reducing tool wear and improving surface finish. However, controlling the usage is imperative due to the ecological and/or economical and reasons. Minimum quantity lubrication (MQL) has recently emerged as a viable option to minimize the amount of fluid used in machining without sacrificing its lubrication and cooling in machining. This paper presents our effort to understand the parameters in the MQL process in order to expand its effectiveness in cutting operations. Although some literature regarding the influence of flow rates and nozzle directions is available, this information is insufficient. This paper studies three new parameters in the MQL process, namely the droplet size, the droplet size distribution, and the wetting angle. Confocal laser scanning microscopy (CSLM), wavelet filtering, and image processing algorithms were used to calculate the droplet geometry and distribution for various commercially available MQL oils. The wetting angles of the oils were measured by depositing oil droplets onto TiSiN and TiAIN coated inserts. The parameters studied are important to estimate the comparative performance of lubricant-coating pairs.