Grinding with minimum quantity lubrication: a comparative assessment

Conventional lubrication systems are used in grinding operations to reduce friction and defects produced during machining. Mineral-based oils, commonly used as conventional lubricants, were observed to produce greenhouse wastes that are hazardous to the environment. The minimum quantity lubrication (MQL) system, an eco-friendly, economical, and less hazardous lubrication technique, is affirmed to be an efficient substitute for these conventional lubricants. Nevertheless, the pure vegetable and synthetic oils used in MQL systems have lower tribological and thermal evacuation properties compared to conventional lubricants. Many adjustments and improvements have been introduced into the MQL system such as the introduction of nanofluids, cryogenic air, ionic fluids, and electrostatic atomization. This study aims to come up with an extensive review and analytical assessment of the trends and developments of the MQL system in grinding operations. Firstly, the different advances ranging from fluid types, additives, and redesigns of the MQL systems are discussed. Likewise, the results obtained from using different types of lubricants and nanofluids in the MQL system were discussed. Moreover, a detailed comparative assessment of the grinding performances between the MQL systems, dry grinding, and conventional lubrication was provided. It was found that the nanofluid MQL system produced 60% lower surface roughness and reduced the grinding forces by 30% compared to flood cooling systems. Lastly, the area of focus for research on grinding with MQL system for future advancements was proposed. The various advancements include the introduction of nanofluid varieties and the overall modification of the grinding system.