Experimental investigation into the effects of nozzle position,workpiece hardness,and tool type in MQL turning of AISI 1045 steel

Minimum quantity lubrication (MQL) is a replacement for dry machining in which a minimum quantity of lubricant fluid is mixed up with compressed air and sprayed periodically on the machining area. In this research the effects of different parameters on the MQL turning of AISI 1045 steel have been investigated to evaluate the cutting force, surface roughness, and tool wear in comparison with the wet and dry machining. The research is aimed to study the effect of the MQL nozzle position, workpiece hardness and tool type on the output parameters. During MQL machining experiments, the nozzles were placed in three different arrangements relative to the tool to investigate the effect of the nozzle position. The effect of workpiece hardness and tool type were also studied experimentally for different lubrication conditions. The results indicated that the MQL system significantly increases the cutting efficiency in AISI 1045 steel machining. The experiments results have also confirmed a significant influence of the nozzle position, workpiece hardness, and tool type on the outputs. Machining with MQL is also beneficial to the environment and machine tool operator health as lubricant consumption during operation with MQL is 7-fold lower than in the conventional system.     

An investigation on surface grinding of AISI 4140 hardened steel using minimum quantity lubrication-MQL technique

In dry grinding, as there is no coolant lubricant to transfer the heat from the contact zone, generation of surface damages are not preventable. Promising alternatives to conventional flood coolant applications are also Minimum Quantity Lubricant (MQL) or Near Dry Machining (NDM) or Semi Dry Machining (SDM). As the name implies, MQL machining uses a very small quantity of lubricant delivered precisely to the cutting zone. Often the quantity used is so small that no lubricant is recovered from the parts. Any remaining lubricant may form a film that protects the parts from oxidation or the lubricant may vaporize completely due to high temperatures of the cutting zone. A number of studies have shown that MQL grinding can show satisfactory performance in practical grinding processes. However, there has been little investigation of cutting fluids to be used in MQL grinding. In this study, several grinding fluids, including mineral, vegetable and synthetic esters oil, are compared on the basis of the grinding forces and surface quality properties that would be suitable for MQL grinding applications, to develop a multifunctional fluid having the MQL results such as cooling, lubrication and high ecological and environmental safety performances. The grinding performance of fluids is also evaluated in dry and conventional fluid grinding techniques.     

Machining of 6061 aluminium alloy with MQL, dry and flooded lubricant conditions

This paper reports on the effect of different lubricant environments when 6061 aluminium alloy is machined with diamond-coated carbide tools. The effect of dry machining, minimum quantity of lubricant (MQL), and flooded coolant conditions was analyzed with respect to the cutting forces, surface roughness of the machined work-piece and tool wear. The three types of coolant environments are compared. It is found that MQL condition will be a very good alternative to flooded coolant/lubricant conditions. Therefore, it appears that if MQL properly employed can replace the flooded coolant/lubricant environment which is presently employed in most of the cutting/machining applications, thereby not only the machining will be environmental friendly but also will improve the machinability characteristics.     

Influence of minimum quantity lubrication parameters on grind-hardening process

Currently, dry grind-hardening has been studied to achieve a deep grinding harden layer. For dry grind-hardening process, the ground surface may have a poor surface quality. In our previous research, minimum quantity lubrication (MQL) has been proved as an effective way to improve the surface quality in grind-hardening process. Unfortunately, the relationship between the surface quality and parameters of MQL is still not clear. In this paper, different spraying parameters (fluid flow, air pressure, nozzle location, spraying distance) are investigated in surface grinding experiments of annealed steel AISI 5140. Grind-hardening performances are analyzed for grinding force and surface quality, such as surface roughness, micro-hardness, and grinding harden layer depth. Consequently, the results show that MQL can improve the grinding surface roughness and the micro-hardness of the grinding harden layer. The surface roughness can be improved with a better lubrication, which can be achieved with the appropriate spray direction. The surface roughness and the harden layer depth are reduced with the increasing fluid flow rate and air pressure, while they increase with the spraying distance.     

Effect of cryogenic minimum quantity lubrication on machinability of diamond tool in ultraprecision turning of 3Cr2NiMo steel

This work presents a series of experimental investigations and corresponding theoretical analyses to research on the effect of cryogenic minimum quantity lubrication (MQL) on machinability of diamond tool in ultraprecision turning of typical die steel. The tool wear and machined surface quality were determined as experimental indexes, which were measured using the scanning electron microscope and surface profiler, respectively. Besides, the maximum temperatures of diamond tool surfaces acquired by infrared thermal imager were used to indirectly evaluate the cutting process. The experimental results revealed that cryogenic MQL had obvious advantages in improving diamond tool durability and machined surface quality by comparison with flood cooling, cryogenic gas cooling, and MQL, and its essential function mechanisms were thoroughly understood. On the basis of this, carbon nanofluid was found to achieve optimal tool life in diamond turning compared with polyethylene glycol, castor oil, synthetic ester, and emulsified liquid. Ultimately, the combined machining method of ultrasonic vibration-assisted turning and cryogenic minimal quantity lubrication was proposed in this work. The results showed that this technique could observably improve the machinability of diamond tool and also provide a new direction for exploring a suitable processing method for ultraprecision machining of ferrous materials.     

Simplified MQL system for drilling AISI 304 SS using cryogenically treated drills

In machining operations, cutting fluids have been comprehensively used to improve the cutting tool life, but the issues related to manufacturing cost, environment and health call for reducing their use by possible methods. Minimum quantity lubrication (MQL) is a technique that overcomes these problems by spraying a small amount of cutting fluid (<100?ml/hr) as mist using compressed air. In this work, the basic MQL technique is used to achieve flow rates slightly higher (～880?ml/hr) than MQL using simple techniques like paint sprayer and compressor, which is more generally called reduced quantity lubrication (RQL). Another method to increase the tool life is by cryogenic treatment, which increases the hardness of the tool. Tungsten carbide drill bits were subjected to cryogenic treatment (?185 °C). Drilling studies were carried out on AISI 304 stainless steel (SS) using untreated and cryo-treated WC drill bits under RQL and conventional wet lubrication conditions. The tool wear on the treated WC drill bits with RQL was comparatively less than on the untreated ones with RQL and wet lubrication. These improvements were established through microhardness, SEM images, XRD, wear studies and surface roughness measurements comparisons.     

不同冷却润滑方式对切削SiCP/Al复合材料刀具磨损的影响

为探究不同冷却润滑方式对切削SiC_P/Al复合材料刀具磨损的影响,进行了干切削（Dry）、微量润滑（MQL）、液氮（LN₂）、切削油（Oil）和乳化液（Emulsion）共五种冷却润滑条件下的车削实验,分析了冷却润滑方式对刀具边界磨损、刀具破损和后刀面磨损的影响。结果表明:MQL和LN₂有更佳的流体冲刷效果,可以将脱落的SiC颗粒及时带离切削区,减少边界磨损; Oil和Emulsion冲刷效果较差,会加剧边界磨损。LN₂的使用会增加刀具受到的热应力和机械冲击,积屑瘤发生完全脱落,造成切削过程不平稳,当切削距离达到1 100 m时,刀具发生破损; Oil切削时,严重的边界磨损导致刀尖部位尺寸减小,强度降低,当切削距离达到825 m时发生了刀具破损。MQL良好的润滑渗透性和LN₂有效的冷却效果可以减少后刀面磨损。因此,MQL兼具冷却、润滑和流体冲刷效果,更加适合作为切削SiC_P/Al复合材料的冷却润滑方式。      

Experimental investigations on cryogenic cooling by liquid nitrogen in the end milling of hardened steel

Milling of hardened steel generates excessive heat during the chip formation process, which increases the temperature of cutting tool and accelerates tool wear. Application of conventional cutting fluid in milling process may not effectively control the heat generation also it has inherent health and environmental problems. To minimize health hazard and environmental problems caused by using conventional cutting fluid, a cryogenic cooling set up is developed to cool tool–chip interface using liquid nitrogen (LN₂). This paper presents results on the effect of LN₂ as a coolant on machinability of hardened AISI H13 tool steel for varying cutting speed in the range of 75–125 m/min during end milling with PVD TiAlN coated carbide inserts at a constant feed rate. The results show that machining with LN₂ lowers cutting temperature, tool flank wear, surface roughness and cutting forces as compared with dry and wet machining. With LN₂ cooling, it has been found that the cutting temperature was reduced by 57–60% and 37–42%; the tool flank wear was reduced by 29–34% and 10–12%; the surface roughness was decreased by 33–40% and 25–29% compared to dry and wet machining. The cutting forces also decreased moderately compared to dry and wet machining. This can be attributed to the fact that LN₂ machining provides better cooling and lubrication through substantial reduction in the cutting zone temperature.     

Machinability studies on Al 7075/BN/Al2O3 squeeze cast hybrid nanocomposite under different machining environments

Enforcement of stricter environmental policies demands alternative methods that could reduce the usage of cutting fluid during machining. Thus, dry machining and minimum quantity lubrication (MQL) machining are gaining practical importance. Due to enhanced mechanical and thermal properties, aluminium based nanocomposites have wide application in aerospace and automobile industries. In this work, asqueeze cast hybrid nanocomposite is developed with the reinforcement of 0.5?wt% hexagonal boron nitride and 1?wt% alumina particles in the base matrix of Al 7075 that is subjected to a squeezing pressure of 150?MPa. During the turning of this hybrid nanocomposite, thefeed rate is varied (0.1, 0.2, and 0.3?mm/rev)and its influence on the generated forces, tool wear and surface roughness under dry and MQL environments is performed. The results are compared with squeeze cast unreinforced aluminium alloy and presented.     

Application of ultrasonic vibration assisted MQL in grinding of Ti–6Al–4V

This work presents experimental investigations performed to evaluate the improvement in grinding performance of Ti–6Al–4V alloy using ultrasonic vibration assisted minimum quantity lubrication (UMQL) technique. The grinding experiments have been performed using an indigenously designed and fabricated UMQL setup. In UMQL, the ultrasonic vibration of the horn has been used to atomise the cutting fluid into ultra-fine droplets of uniform size. Sunflower oil in 1, 5 and 10% of the volume have been added in water to prepare the biodegradable emulsions and used as grinding medium. The grinding performance during UMQL has been evaluated by comparing the grinding forces, surface roughness and the ground surface topography obtained during dry and conventional MQL (CMQL) techniques. Surface quality and chip morphology have been studied using microscopic imaging techniques. The UMQL grinding results in smaller grinding forces, and improved surface quality as compared to CMQL grinding. The experimental findings demonstrate that the UMQL has a strong potential to enhance the grindability of Ti–6Al–4V. The present work is also a step forward in finding a sustainable grinding technique for high strength materials using vegetable oil as a coolant.     

Machinability studies on 17-4 PH stainless steel under cryogenic cooling environment

Under higher cutting conditions, machining of 17-4 precipitation hardenable stainless steel (PH SS) is a difficult task due to the high cutting temperatures as well as accumulation of chips at the machining zone, which causes tool damage and impairment of machined surface finish. Cryogenic machining is an efficient, eco-friendly manufacturing process. In the current work, cutting temperature, tool wear (flank wear (V_b) and rake wear), chip morphology, and surface integrity (surface topography, surface finish (R_a), white layer thickness (WLT)) were considered as investigative machinability characteristics under the cryogenic (liquid nitrogen), minimum quantity lubrication (MQL), wet and dry environments at varying cutting velocities while machining 17-4 PH SS. The results show that the maximum cutting temperature drop found in cryogenic machining was 72%, 62%, and 61%, respectively, in contrast to dry, wet, and MQL machining conditions. Similarly, the maximum tool wear reduction was found to be 60%, 55%, and 50% in cryogenic machining over the dry, wet, and MQL machining conditions, respectively. Among all the machining environments, better surface integrity was obtained by cryogenic machining, which could produce the functionally superior products.     

Ti6Al4V Titanium Alloy End Milling with Minimum Quantity of Fluid Technique Use

To reduce the use of cutting fluids in machining operations is a goal that has been searched in the industry due to environmental and human health problems that the cutting fluids cause. However, cutting fluids still promote the longer life of the cutting tool for many machining operations. This is the case of Ti6Al4V titanium milling operation using coated cemented carbide inserts. Therefore, the aim of this work is to study the feasible cutting conditions for use of minimal quantity of fluid (MQF) technique, i.e., conditions that make the tool life in MQF technique closer or higher than those obtained with the cutting without lubrication/cooling and cutting fluid jet without giving up productivity and the average roughness of the parts in the process. To achieve these objectives, several trials at Ti6Al4V end milling were performed by varying the cutting speed and feed rate with MQF application technique using vegetable cutting fluid compared with no lubrication/cooling and cutting with jet fluid to 8% aqueous emulsion. The main conclusion from this study was that the application of the MQF technique in Ti6Al4V end milling process increases the tool life and productivity and reduces the average surface roughness, while maintaining the same cutting conditions originally proposed in machining. Finally, microstructural analysis by scanning electron microscope (SEM) and energy dispersive spectrometry (EDS) was performed from cutting tools, and the main wear mechanisms when varying the lubrication/cooling systems employed were observed.     

Environment Friendly Machining of Ni–Cr–Co Based Super Alloy using Different Sustainable Techniques

In order to eradicate the use of mineral based cutting fluid, the machining of Ni–Cr–Co based Nimonic 90 alloy was conducted using environment friendly sustainable techniques. In this work, uncoated tungsten carbide inserts were employed for the machining under dry (untreated and cryogenically treated), MQL, and cryogenic cutting modes. The influence of all these techniques was examined by considering tool wear, surface finish, chip contact length, chip thickness, and chip morphology. It was found that the cryogenically treated tools outperformed the untreated tools at 40 m/min. At cutting speed of 80 m/min, MQL and direct cooling with liquid nitrogen brought down the flank wear by 50% in comparison to dry machining. Similarly at higher cutting speed, MQL and cryogenic cooling techniques provided the significant improvement in terms of nose wear, crater wear area, and chip thickness value. However, both dry and MQL modes outperformed the cryogenic cooling machining in terms of surface roughness value at all the cutting speeds. Overall cryotreated tools was able to provide satisfactory results at lower speed (40 m/min). Whereas both MQL and cryogenic cooling methods provided the significantly improved results at higher cutting speeds (60 and 80 m/min) over dry machining.     

Built-up edge reduction in drilling of AISI 1045 steel

In this study, a combined drilling method consists of ultrasonic-assisted drilling (UAD) under the presence of minimum quantity lubrication (MQL), is evaluated. Effect of this method on machinability factors is investigated by implementation of a dynamometer and a vision-measuring microscope. Then the results are compared with the values obtained in conventional drilling, and separately UAD and MQL-drilling. As a result, it was revealed that the output parameters were significantly improved when combined MQL–UAD method was exerted. In particular, built-up edge and drill skidding have almost been eliminated. Moreover, it was shown that increase of tool rake angle and producing broken chips caused thrust force and surface roughness to be reduced in UAD and UAD–MQL. In the combined strategy, burr-less hole has been achieved due to the formation of solid burr at the exit surface of drilled hole.     

Experimental investigation of tool wear and chip formation in cryogenic machining of titanium alloys

Titanium alloys are one of the most important design materials for the aircraft industry.The high strength-to-density-ratio and the compatibility with carbon fibre reinforced plastic are the reasons for a raising application in this field.The outstanding properties lead to challenging machining processes.High strength and low heat conductivity affect high mechanical and thermal loads for the cutting edge.Thus,the machining process is characterized by a rapid development of tool wear even at low cutting parameter.To reach a sufficient productivity it is necessary to dissipate the resulting heat from the cutting edge by a coolant.Therefore the cryogenic machining of two different titanium alloys is investigated in this work.The results point out the different behavior of the machining processes under cryogenic conditions because of the reduced thermal load for the cutting tool.According to this investigation,the cryogenic cooling with CO_2enables an increase of the tool life in comparison to emulsion based cooling principles when machining theα+β-titanium alloy Ti-6Al-4V.The machining process of the high strength titanium alloy Ti-6Al-2Sn-4Zr-6Mo requires an additional lubrication realized by a minimum quantity lubrication(MQL) with oil.This combined cooling leads to a smoother chip underside and to slender shear bands between the different chip segments.     

A Review on Minimum Quantity Lubrication for Machining Processes

In the pursuit toward achieving dry cutting, air machining, minimum quantity lubrication (MQL), and cryogenically cooled machining are the stepping stones. Nevertheless, machining is always accompanied by certain difficulties, and hence none of these methods has provided a complete solution. Hence, this article reviews various MQL methods used by various machining processes for different materials. It also highlights the future work directions for research in this area.     

Turning of Brasses Using Minimum Quantity of Lubricant (MQL) and Flooded Lubricant Conditions

A lot of effort is being carried out to reduce the use of lubricants in metal machining operations from the viewpoint of cost, ecology and human health issues. Minimal quantity lubrication (MQL) is now an established alternative to conventional flood lubricant system. This paper reports on the experimental work carried out during turning of brasses with different amounts of MQL. Turning with flood lubrication was also performed and a comparison is made. The various parameters studied include the feed, cutting power, specific cutting power, and surface roughness. The results of the study suggest that with proper selection of the MQL system, results similar to flood lubricant condition can be achieved.     

Surface Defects in Groove Milling of Hastelloy-C276 Under Fluid Coolant

This study aims to investigate surface integrity in groove milling of Hastelloy-C276 using coated carbide end mills under the application of water-based fluid coolant using different cutting parameters. Surface integrity was assessed by measuring surface roughness, using focus variation microscope, and investigating surface defects, using scanning electron microscope. Micro-chips re-deposition and long grooves dominated the machined surface at low cutting speed (24–50 m/min). While cracked and fractured re-deposited materials, grooves, large debris, and plastic flow dominated the machined surface at high cutting speed (70–120 m/min), consequently surface roughness increased with cutting speed. Nucleated cavities appeared at all cutting speeds but with different densities. Shallow depth of cut at low cutting speed gave negative effect on surface roughness due to the effect of the hardened layer. Overall, the best surface finish, with average roughness below 50 nm and minimum surface abuse, was obtained in the speed range of 24–50 m/min at feed rate of 1 µm/tooth and depth of cut deeper than 0.1 mm.     

Progress of Nanofluid Application in Machining: A Review

A colloidal mixture of nanometer-sized (<100 nm) metallic and non-metallic particles in conventional cutting fluid is called nanofluid. Nanofluids are considered to be potential heat transfer fluids because of their superior thermal and tribological properties. Therefore, nano-enhanced cutting fluids have recently attracted the attention of researchers. This paper presents a summary of some important published research works on the application of nanofluid in different machining processes: milling, drilling, grinding, and turning. Further, this review article not only discusses the influence of different types of nanofluids on machining performance in various machining processes but also unfolds other factors affecting machining performance. These other factors include nanoparticle size, its concentration in base fluid, lubrication mode (minimum quantity lubrication and flood), fluid spraying nozzle orientation, spray distance, and air pressure. From literature review, it has been found that in nanofluid machining, higher nanoparticle concentration yields better surface finish and more lubrication due to direct effect (rolling/sliding/filming) and surface enhancement effect (mending and polishing) of nanoparticles compared to dry machining and conventional cutting fluid machining. Furthermore, nanofluid also reduces the cutting force, power consumption, tool wear, nodal temperature, and friction coefficient. Authors have also identified the research gaps for further research.     

Multi-attribute optimization of end milling epoxy granite composites using TOPSIS

Epoxy granite composites are identified and recognized as better materials for machine tool applications due to inherent damping properties. However, end milling of these composites has not been explored much. Milling of epoxy granite composites presents a number of problems, namely, cutting forces and surface roughness appear during machining. This research work focuses on end milling of epoxy granite composite specimens using high-speed steel end mill cutter by varying the cutting conditions such as spindle speed and feed with a uniform depth of cut and selection of optimal machining parameters. The experimental runs of 27 different trials were carried out and three different attributes such as thrust force, tangential force, and surface roughness were analyzed. This research work presents a sequential procedure for machining parameters selection. Selection of optimal machining parameters is done on the basis of Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method.