Abstract: Minimum quantity lubrication (MQL) has been accepted as a successful semi-dry application because of its satisfactory performance in practical machining operations. However, the oil mist generated from MQL machining process has a direct impact on the ambient air quality, and then does harm to those who permanently work in this environment. Using the weighing method, the oil mist concentration in machining workshop is measured and analyzed, and the influence of MQL system parameters such as oil flow rate, air pressure, spray distance to target, jet temperature and lubricant property on the oil mist concentration PM10 and PM2.5 in the machining workshop are investigated. The results show that oil flow rate is the most important factor which affects the oil mist concentration in the machining workshop. With the increase of oil flow rate, the oil mist concentration increases significantly. The oil flow rate should be limited to less than 15 mL/h. The water vapor in the air is easy to condense and adhere to the fine particles at low jet temperatures, which results in that the measurement results of oil mist concentration are higher than those at room temperatures. But the oil mist concentration will decrease as the jet temperature decreases during the cryogenic MQL milling process.

Key words: minimum quantity lubrication;ambient air quality;oil mist concentration