Cryogenic minimum quantity lubrication machining: from mechanism to application

Cutting fluid plays a cooling-lubrication role in the cutting of metal materials.However,the substantial usage of cutting fluid in traditional flood machining seriously pollutes the environment and threatens the health of workers.Environmental machining technologies,such as dry cutting,minimum quantity lubrication(MQL),and cryogenic cooling technology,have been used as substitute for flood machining.However,the insufficient cooling capacity of MQL with normal-temperature compressed gas and the lack of lubricating performance of cryogenic cooling technology limit their industrial application.The technical bottleneck of mechanical-thermal damage of difficult-to-cut materials in aerospace and other fields can be solved by combining cryogenic medium and MQL.The latest progress of cryogenic minimum quantity lubrication(CMQL)technology is reviewed in this paper,and the key scientific issues in the research achievements of CMQL are clarified.First,the application forms and process characteristics of CMQL devices in turning,milling,and grinding are systematically summarized from traditional settings to innovative design.Second,the cooling-lubrication mechanism of CMQL and its influence mechanism on material hardness,cutting force,tool wear,and workpiece surface quality in cutting are extensively revealed.The effects of CMQL are systematically analyzed based on its mechanism and application form.Results show that the application effect of CMQL is better than that of cryogenic technology or MQL alone.Finally,the prospect,which provides basis and support for engineering application and development of CMQL technology,is introduced considering the limitations of CMQL.

Energy field-assisted high-speed dry milling green machining technology for difficult-to-machine metal materials

Energy field-assisted machining technology has the potential to overcome the limitations of machining difficult-to-machine metal materials,such as poor machinability,low cutting efficiency,and high energy consumption.High-speed dry milling has emerged as a typical green processing technology due to its high processing efficiency and avoidance of cutting fluids.However,the lack of necessary cooling and lubrication in high-speed dry milling makes it difficult to meet the continuous milling requirements for difficult-to-machine metal materials.The introduction of advanced energy-field-assisted green processing technology can improve the machinability of such metallic materials and achieve efficient precision manufacturing,making it a focus of academic and industrial research.In this review,the characteristics and limitations of high-speed dry milling of difficult-to-machine metal materials,including titanium alloys,nickel-based alloys,and high-strength steel,are systematically explored.The laser energy field,ultrasonic energy field,and cryogenic minimum quantity lubrication energy fields are introduced.By analyzing the effects of changing the energy field and cutting parameters on tool wear,chip morphology,cutting force,temperature,and surface quality of the workpiece during milling,the superiority of energy-field-assisted milling of difficult-to-machine metal materials is demonstrated.Finally,the shortcomings and technical challenges of energy-field-assisted milling are summarized in detail,providing feasible ideas for realizing multi-energy field collaborative green machining of difficult-to-machine metal materials in the future.