State-of-the-art on minimum quantity lubrication in green machining

In the field of mechanical manufacturing, the concepts of clean production and sustainable development have gradually emerged and gained global attention. Therefore, clean production and sustainable development are essential concepts in modern research. Traditional liquid cooling and lubrication methods typically use a flow rate of 60 L/h, whereas Minimum Quantity Lubrication (MQL) reduces it to a range of 30-100 mL/h, which is only one-thousandth of the flow rate used in traditional liquid cooling methods. MQL significantly improves the working environment, reduces pollution to the natural environment, and represents an efficient and low-carbon machining technology that aligns with the principles of clean production. This study reviews the research progress in the MQL field from 2021 to 2023, summarizes and reviews the characteristics of MQL in various areas, analyzes the advantages and developments in each area, and provides an overview of the future trends in MQL across different domains. By reassessing the modern advancements of MQL technology and comparing different machining methods, machining parameters, efficiency-enhancing new technologies, and the performance differences caused by cutting fluids, this study provides an intuitive reflection on the challenges currently faced in the MQL field. From this perspective, the study aims to assist the future development of MQL by exploring better cooling and lubrication effects while minimizing adverse environmental impacts.