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decades, and some of the theories even show up much longer ago than that. But some notable disadvantages of food fuid systems have increased momentum for MQL in recent years. Besides the cost involved with food fuid systems (which is high in many instances), equipment variety, contamina- tion and waste are some of the other unfavorable charac- teristics of these systems. Flood fuid systems need equipment to recirculate, flter, test and treat the coolant to keep it viable. Contamination from bacteria, tramp oil and swarf are concerns related to the disposal of spent coolant, which is typically classi- fed as toxic waste. Its disposal is regulated, so related costs need to be considered. In fact, the cumulative cost of metalworking fuids can be as high as 15 percent of the total cost to produce a part. Another issue with flood coolant is the mess it can create. Invariably, coolant ends up covering more than only the cutting tool and workpiece. Machines, floors and finished parts get coated as well. The U.S. Occupational Safety and Health Administration (OSHA) and the U.S. National Institute for Occupational Safety and Health (NIOSH) reported in the late 1990s that the permissible exposure level (PEL) for metalworking fluid aerosol concentration is 5 mg/m 3 and 0.5 mg/m 3 , respectively. However, a study by Bennett and Bennet in 1985 showed that the oil-mist level in U.S. automotive parts manufacturing facilities was estimated in the 20 to 90 mg/m 3 range with the use of conventional lubrication by flood coolant. The efforts to reduce toxic waste and to create a sustainable working environment have vitalized the search for ways to reduce energy consumption for metal- working fluid supply. The increase in environmental awareness has made the minimization of these fluids an important goal. Other Advantages MQL technology was developed to address many of the inconveniences and concerns posed by food fuid systems. Te biggest and most obvious advantage of MQL is that it uses less fuid and involves less cost. But when properly applied, the use of an engineered fuid that is supplied at the right point and in the right quantity can signifcantly reduce tool wear. Increases in tool life of more than 50 percent (even approaching 100 percent in some cases) have been reported. It can also lead to an increase in consistency and integrity of machined surfaces—better, more consistent fnish and reduced residual stresses. With the right lubrication and with chips breaking instead of wrapping around the part, the cutting process is leaner, improving the surface fnish. MQL can also help to eliminate built-up edge in certain cutting operations. Reducing tool wear also contributes to more consistent fnishes. With MQL, the chips end up dryer and cleaner. Sensor switches last much longer because they're not being splashed with fuid. Te cost of buying and disposing of conventional cutting fuids is reduced, and less energy is consumed. In general, the overall cost is lower than conventional food coolant applications. Although not completely proven, MQL has also shown signs of allowing for higher feed rates and higher RPMs. Wise Implementation Despite the advantages demonstrated, MQL is not a universal solution for all machining processes. It has a number of limitations and can present its own set of challenges that need to be considered by anyone thinking of implementing the technology. Te purpose of cutting fuid :: MQL is not without its challenges. Parts and equipment require additional cleaning considerations, and emissions of gas and metal components can pose potential hazards. Minimum Quantity Lubrication productionmachining.com :: 41