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Environmental protection is the major concern of any form of manufacturing industry today. As focus has shifted towards sustainable cooling strategies, minimum quantity lubrication (MQL) has proven its usefulness. The current survey intends to make the MQL strategy more effective while improving its performance. A Ranque–Hilsch vortex tube (RHVT) was implemented into the MQL process in order to enhance the performance of the manufacturing process. The RHVT is a device that allows for separating the hot and cold air within the compressed air flows that come tangentially into the vortex chamber through the inlet nozzles. Turning tests with a unique combination of cooling technique were performed on titanium (Grade 2), where the effectiveness of the RHVT was evaluated. The surface quality measurements, forces values, and tool wear were carefully investigated. A combination of analysis of variance (ANOVA) and evolutionary techniques (particle swarm optimization (PSO), bacteria foraging optimization (BFO), and teaching learning-based optimization (TLBO)) was brought into use in order to analyze the influence of the process parameters. In the end, an appropriate correlation between PSO, BFO, and TLBO was investigated. It was shown that RHVT improved the results by nearly 15% for all of the responses, while the TLBO technique was found to be the best optimization technique, with an average time of 1.09 s and a success rate of 90%.

Grinding is one of the important machining processes that are widely applied in precision manufacturing. In the beginning, studies mostly focused on dry machining. In time, emerging technologies have led to change in the development of the machining process. New techniques and tools have been developed over the last decade that has brought the process to an advanced place. At first, flood cooling has removed the burning problems in the grinding process. After that, a new technique was developed which is known as minimum quantity lubrication (MQL). This technique is a recognized opportunity to eliminate environmental concerns. This paper reviews some of the common as well as advanced MQL systems specifically used in grinding operations. The effect of MQL and other cutting parameters on cutting forces, surface roughness of the machined workpiece, tool wear, temperature, specific cutting energy, and residual stress is outlined. This paper also addressees the recent trend of cooling systems in the grinding process. After reading this research paper, one can easily get an overview of the previously conducted research to find the output parameter trends in MQL condition. The reader can infer from this paper in which direction the development trend in grinding is in the machining process.

This experimental study article analyses the machinability of Duplex Stainless Steel when turned using various wet coolants, including as (Coconut, Mustard, Soyabean oil). Cutting speed, feed, depth of cut, nozzle inclination angle, pressure, and standoff distance are all input process factors. The output response parameters were considered such as thrust force, machining zone temperature, tool wear and surface roughness. In this experimental study, Taguchi technique was used to design the experimental runs under three different level combination of process parameters. The experimental result indicates that the turning performance has been improved at coconut oil condition over the other coolant conditions and it produces the uniform surface finish throughout the length of the workpiece.

Nowadays, environmental concern and the search for environmentally friendly techniques have contributed to industrial development towards sustainability. Production without social and environmental impact is one of the main goals of engineering research. Although analysis is carried out, some manufacturing processes still require studies, such as grinding, for example. In this process, the interaction between the grinding wheel and workpiece generates a significant amount of heat, due to shearing, friction, and scratching caused by the contact of the numerous abrasive grains with the workpiece surface. The heat generated at the interface has a more intense flow to the workpiece, which can cause several microstructural damages, as well as providing shape errors and increased grinding wheel wear. Thus, the application of cutting fluid is indispensable to minimize the harmful effects caused by heat to the grinding wheel and the workpiece during the process. However, the industry commonly uses soluble cutting fluid, having oil in its composition, in addition to chemical components that prevent its degradation, due to recirculation in the system and the need to avoid the accumulation of bacteria, whereas its application has a flow rate of tens of liters per minute. These cutting fluids will be discarded at some point, which will require complex waste treatment processes for proper disposal. An alternative to this type of application is the minimum quantity lubrication (MQL), which consists of a few milliliters per hour, but which has low refrigerant power. Some techniques have been developed to enhance its application and make it more refrigerant, such as the application of a jet of compressed air directed to the grinding wheel cutting surface to perform the cleaning, minimizing the heat generation by the reduced agglomeration of chips in the grinding wheel pores. Therefore, this work analyzed the cylindrical plunge grinding of hardened steel workpiece with cubic boron nitride grinding wheel on different cooling conditions, comparing the conventional cutting fluid application method (flood) with the MQL technique, MQL simultaneously with the wheel cleaning jet (MQL + WCJ) and MQL with cutting fluid applied at 0 °C (MQL + CA). The performance of each method was analyzed by using the measurements of surface roughness (Ra), roundness error, diametral wheel wear, power consumed during the process, specific energy grinding, microhardness, and microstructural analysis to investigate possible modifications of the microstructure of the workpiece. It was found that in none of the cases, there were microstructural alterations, but the MQL application method presented the worst values of the variables among the techniques studied, whereas the application on low temperature showed potential to be used in a large scale. Nevertheless, the MQL application method applied simultaneously with the wheel cleaning jet (WCJ) has presented the closest values of the conventional method; it becomes the most feasible method for application in the industry towards the protection of the environment and health of the workers.

The application of micro-mechanical cutting operations, such as micro-drilling, is crucial for producing microsystem components. In the production of jet engine parts, Inconel 718 superalloy has been used to produce these components due to its high performance at high temperatures. Due to the low thermal conductivity and the high work hardening tendencies of Inconel 718, a high amount of the cutting temperature dissipates toward the cutting tool instead of the chip. When using micro-scale drilling (micro-drilling), heat dissipation becomes more challenging. This affects the tool life and the machined surface quality; therefore, when machining these alloys, a cutting fluid is required to decrease the high amounts of generated heat. Flood coolant is commonly used to reduce the cutting temperature; however, government regulations have been published for alternative cooling processes to decrease the influences of flood coolant on the environment and the operator’s health. Minimum quantity lubrication (MQL) has been used as an alternative to conventional cutting fluids because it minimizes the consumption of cooling lubricants and reduces the environmental and health impacts; however, pure MQL cooling has an ineffective cooling ability. In order to enhance thermal conductivity, viscosity, and wettability of the MQL base fluid, an MQL-nanofluid was used. This study investigated the performance of a micro-drilling process using an MQL-nanofluid with regard to thrust forces, tool wear, and burr formation, and compared it to flood cooling and a pure MQL. Micro-drilling experiments involving Inconel 718 were conducted using the same cutting parameters, drilling tool, and machining environment for both the MQL and the flood coolant. The results revealed that the MQL-nanofluid approach was promising in terms of machining outputs as well as sustainability.

Nickel-based superalloys, as typically difficult-to-machine materials, are mainly used in aero-engine, ship, chemical industry, and other fields. To further enhance the surface quality of nickel-based superalloys, prolong the life of wheels, save the related costs, and achieve sustainable development, many exploratory works on eco-friendly sustainable grinding technology have been carried out by relevant researchers. Based on the action and material properties of nickel-based superalloys, the lubrication mechanism and research results of MQL are first summarized. Then, the latest research progress of micro-lubrication technology and its synergism technology is introduced briefly. In addition, the relationship between MQL penetration characteristics, grinding process characteristics, and eco-friendly sustainability is established. Finally, the technical mechanism and latest achievements of Cryo-MQL, NMQL, and EMQL are summarized. The aim of those works is to reveal the MQL synergistic mechanism and provide a theoretical basis and technical guidance for its grinding engineering application of nickel-based superalloys.

The study investigates the sustainability evaluation and optimization of machining parameters in the turning process of AISI 304 steel under different lubrication and cooling conditions. The research employs a Taguchi experimental design to assess the impact of various cutting parameters, comparing dry cutting with a hybrid semi-dry method using CO2 and Minimum Quantity Lubrication (MQL) with nano TiO2. The optimization of the process resulted in Vc of 195 m/min and f of 0.2 mm/rev cutting conditions. The findings demonstrate that hybrid lubrication and cooling significantly reduce tool wear and extend tool life compared to dry cutting (80% better). The type of cutting fluid is identified as the most critical factor in prolonging tool life resulting the Cryo + MQL + nano TiO2 better than dry conditions. In the sustainability analysis, the Grey Relational Analysis (GRA) method was used. Encompassing economic, environmental, and social indicators, the study reveals that hybrid machining processes (GRG: 0.61) could be one of the alternatives to be used in terms of energy consumption tool life, and environmental impact for its behaviour to replace dry machining (GRG: 0.83). This study provides a comprehensive framework for optimizing machining processes with a focus on sustainability, highlighting the benefits of hybrid lubrication and cooling systems in improving tool performance and reducing environmental impact.

In modern days, the conception of sustainability has progressively advanced and has begun receiving global interest. Thus, sustainability is an imperative idea in modern research. Considering the recent trend, this review paper presents a summary of the previously published research articles on minimum quantity lubrication (MQL) assisted machining. The requirement to stir towards sustainability motivated the researchers to revise the effects of substitute lubrication methods on the machining. Conventional lubri-cooling agents are still extensively employed when machining of engineering alloys, but the majority of the recent papers have depicted that the utilization of vegetable oil, nanofluids, and nanoplatelets in MQL system confers superior machining performances as compared to conventional lubrication technology. In actual, the definite principle of this manuscript is to re-examine modern advancements in the MQL technique and also explore the benefits of the vegetable oil and nanofluid as a lubricant. In brief, this paper is a testimony to the advancing capabilities of eco-friendly MQL technique which is a viable alternative to the flood lubrication technology, and the outcomes of this review work can be contemplated as a movement towards sustainable machining.

Mineral oil-based cutting fluid is the most commonly used type due to its superior performance, but it has a large environmental impact. Therefore, this study explores the performance of canola oil with TiO2 nanoparticle additives in the Minimum Quantity Lubrication (MQL) system in the CNC milling process with AISI 1045 steel workpieces cut using a 4-flute endmill. The variations in the concentration of TiO2 mass fraction used were 0.1%, 0.15%, and 0.2%. The results showed that using a nano-cutting fluid with 0.15% TiO2 reduced the cutting temperature by up to 56.52% compared to the dry-cutting method. In addition, this cutting fluid also produced the lowest surface roughness (0.722 µm) and negligible tool wear (0.246 mm). The results indicate that the combination of canola oil and TiO2 can be an effective, environmentally friendly alternative in improving machining performance compared to conventional cutting fluids.

To eliminate the negative effect of traditional metal-working fluids and achieve sustainable manufacturing, the usage of nano-enhanced biolubricant (NEBL) is widely researched in minimum quantify lubrication (MQL) machining. It’s improved tool wear and surface integrity have been preliminarily verified by experimental studies. The previous review papers also concluded the major influencing factors of processability including nano-enhancer and lubricant types, NEBL concentration, micro droplet size, and so on. Nevertheless, the complex action of NEBL, from preparation, atomization, infiltration to heat transfer and anti-friction, is indistinct which limits preparation of process specifications and popularity in factories. Especially in the complex machining process, in-depth understanding is difficult and meaningful. To fill this gap, this paper concentrates on the comprehensive quantitative assessment of processability based on tribological, thermal, and machined surface quality aspects for NEBL application in turning, milling, and grinding. Then it attempts to answer mechanisms systematically considering multi-factor influence of molecular structure, physicochemical properties, concentration, and dispersion. Firstly, this paper reveals advanced lubrication and heat transfer mechanisms of NEBL by quantitative comparison with biolubricant-based MQL machining. Secondly, the distinctive filmformation, atomization, and infiltration mechanisms of NEBL, as distinguished from metal-working fluid, are clarified combining with its unique molecular structure and physical properties. Furtherly, the process optimization strategy is concluded based on the synergistic relationship analysis among process variables, physicochemical properties, machining mechanisms, and performance of NEBL. Finally, the future development directions are put forward aiming at current performance limitations of NEBL, which requires improvement on preparation and jet methods respects. This paper will help scientists deeply understand effective mechanism, formulate process specifications, and find future development trend of this technology.