Performance profiling of minimum quantity lubrication in machining

This study develops the analytical understanding of mechanical and environmental effects of minimum quantity lubrication (MQL) in machining and profiles the MQL performance as functions of machining and fluid application parameters. Physics-based predictive models are formulated to quantitatively describe the resulting contact stress and temperature distributions under completely dry, MQL (under boundary lubrication), and flood cooling conditions in cylindrical turning. On that basis, the air quality effects in terms of cutting fluid aerosol emission rate and droplet size distribution have been derived through the modeling of evaporation, runaway aerosol atomization, and dissipation processes. Additionally, the abrasion, adhesion, and diffusion wear mechanisms under time-evolving cutter geometry have been quantitatively evaluated for the development of a tool wear and tool life relationship with the fluid application condition. Experimental measurements of force, temperature, aerosol concentration, and tool flank wear rate in dry, MQL, and fluid cooling cases has also been pursued to calibrate and validate the predictive models. The MQL performance profile is assessed through the sensitive analysis of tool utilization, power consumption, and air quality with respect to MQL application parameters; and it serves as a basis to support the overall optimization of machining process by incorporating both mechanical and environmental considerations.     

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.     

Study on minimum quantity lubrication in micro-grinding

This paper discusses the performance of the minimum quantity lubrication (MQL) in micro-grinding based on ground surface roughness and tool life. The effects of grinding and lubricating parameters on machining performance are studied. Experiments for dry grinding and grinding with pure air are also conducted for comparison. It is observed that surface roughness and tool life are improved with the application of MQL in micro-grinding. Experimental results show that efficient chip removal from the cutting zone in micro-grinding is important for achieving good surface finish and adequate tool life. The application of a small amount of cutting oil in MQL can significantly extend the tool life. In this study, the tool life in MQL is seven times longer than that in dry grinding and five times longer than that in grinding with air cooling. If the oil flow is surplus to requirements or the air flow is inadequate, excess oil will stay on the grinding tool after the grinding test. As a result, poor surface roughness is observed. The optimal lubrication conditions in this experimental exploration are the combination of an oil flow of 1.88?ml/h and an air flow of 25?L/min.     

On machining of Ti-6Al-4V using multi-walled carbon nanotubes-based nano-fluid under minimum quantity lubrication

Titanium alloys are the primary candidates in several applications due to its promising characteristics, such as high strength to weight ratio, high yield strength, and high wear resistance. Despite its superior performance, some inherent properties, such as low thermal conductivity and high chemical reactivity lead to poor machinability and result in premature tool failure. In order to overcome the heat dissipation challenge during machining of titanium alloys, nano-cutting fluids are utilized as they offer higher observed thermal conductivity values compared to the base oil. The objective of this work is to investigate the effects of multi-walled-carbon nanotubes (MWCNTs) cutting fluid during cutting of Ti-6Al-4V. The investigations are carried out to study the induced surface quality under different cutting design variables including cutting speed, feed rate, and added nano-additive percentage (wt%). The novelty here lies on enhancing the MQL heat capacity using nanotubes-based fluid in order to improve Ti-6Al-4V machinability. Analysis of variance (ANOVA) has been implemented to study the effects of the studied design variables on the machining performance. It was found that 4 wt% MWCNTs nano-fluid decreases the surface roughness by 38% compared to the tests performed without nano-additives, while 2 wt% MWCNTs nano-fluids improve the surface quality by 50%.     

纳米粒子射流微量润滑磨削的冷却性能分析

结合国内外研究现状,主要分析了纳米粒子射流微量润滑的冷却性能,实验对比了浇注式磨削、干磨削、MQL磨削和纳米粒子射流MQL磨削的工件表面温度,结果显示纳米粒子射流MQL具有较好的冷却效果,其应用前景广阔.     

The tribological properties of nanofluid used in minimum quantity lubrication grinding

Minimum quantity lubrication (MQL) grinding using nanofluid showed superior grinding performance by reducing the grinding force and surface roughness in comparison with that of pure base fluid MQL grinding. In this study, the conditions of the grinding interaction between the grinding wheel and the workpiece were simulated by a pin-on-flat tribotester. The role of nanofluid in MQL grinding process was investigated through friction and wear experiments. The results show that nanoparticles, especially Al₂O₃, added to base fluid exhibit noticeable friction reduction and anti-wear properties. The addition of Al₂O₃ nanoparticles in deionized water decreased the friction coefficient and the worn weight by 34.2 and 43.4 %, respectively, as compared to the pure deionized water. Furthermore, investigation was performed using scanning electron microscopy and surface profilometer to interpret the possible mechanisms of friction reduction and anti-wear with nanoparticles.     

Temperatures in fine grinding with minimum quantity lubrication (MQL)

Minimum quantity lubrication (MQL) is a promising new fluid delivery technique in grinding. However, the thermal behaviour of the process under such cooling conditions remains unclear. This work reports on the results of a recent investigation of MQL in fine-cut plane surface grinding. The experimental study considered three conditions: conventional low pressure fluid delivery, dry grinding and MQL delivery. Common steels EN8, M2 and EN31 were ground with a general purpose alumina wheel. Conventional fluid used was a general purpose 5% by volume emulsion; MQL fluid was a general purpose machining oil. Grinding temperatures were measured using the single-pole thermocouple method. Grinding temperatures obtained from experiment are compared with those predicted from theory. Results obtained demonstrate that MQL can deliver a comparable thermal performance to conventional flood delivery under the conditions investigated. Grinding kinematics are discussed to explain the outcomes and to improve understanding of MQL grinding performance.     

Effects and mechanisms in minimal quantity lubrication machining of an aluminum alloy

Effects and mechanisms in minimal quantity lubrication are investigated by use of an intermittent turning process. Especially a difference between minimal quantity lubrication (MQL) and MQL with water is inspected in detail to elucidate boundary film behaviour on the rake face. In order to obtain a good cutting performance by MQL it is considered that two things are needed: (1) an appropriate lubricant, such as a synthetic ester, to form a strong boundary film and (2) a chilling effect to sustain strength of the boundary film.     

Dry and minimum quantity lubrication high-throughput drilling of compacted graphite iron

This research studies the sustainable and high-throughput drilling of compacted graphite iron (CGI), a high strength, lightweight material for automotive powertrain applications. CGI drilling experiments were conducted using a 4 mm diameter coated carbide drill at 26.5 mm/s feed rate. In two repeated tests under three lubrication conditions: dry, dry with through-the-drill compressed air, and through-the-drill minimum quantity lubrication (MQL), the drills were able to produce a maximum of 1,740, 3,150 and 2,948 holes, respectively, before the breakage of the drill. The Joule–Thomson effect due to the expansion of high pressure air from through-the-drill holes at the drill tip, chip shape, chip size and chip speed are investigated. Flank wear of the drill cutting edge is measured and results are correlated to drill life. Results indicate that dry machining of CGI is technically feasible. Chip evacuation and advanced tool cooling are important factors that affect drill life for high-throughput sustainable dry drilling of CGI.     

The influence of spraying parameters on grinding performance for nanofluid minimum quantity lubrication

To reduce the usage of grinding fluid, nanofluid has recently been applied to grinding process with minimum quantity lubrication (MQL) technique. In this study, surface grinding of hardened AISI 52100 steel under different spraying parameters was carried out. Grinding performance was investigated and compared in terms of grinding forces, surface roughness, and grinding temperature. Experimental results show that the MQL nozzle spraying direction has important effects on the application of the nanofluid mist, and then on the lubrication and cooling of the grinding zone. It is found that an optimal grinding performance can be obtained when the nozzle is positioned angularly toward the grinding wheel. Furthermore, it is shown that air pressure and spraying distance are also critical in order to enhance the nanofluid mist to be penetrated into the grinding zone. Grinding forces, surface roughness, and grinding temperature are decreased with the increase of air pressure, and grinding performance in shorter spraying distance is better than that in longer spraying distance. The influence mechanism of the spraying parameters on the grinding performance was discussed.     

静电喷雾润滑液滴的粒径分布特性研究

为掌握静电喷雾润滑液滴的粒径分布特性,将图像识别检测技术应用到荷电润滑液滴的粒径测量中.开展了采集图像中液滴区域的特征抽取和识别分析,建立了液滴的平面二维直径和空间三维直径的转换关系,提出了一种实用的气雾液滴粒径分布特性的检测方法.在建立液滴采集装置的基础上,进行了气雾不同截面液滴的采集和识别试验.实验结果表明,随着静电电压升高,喷雾索特平均直径减小,雾滴颗粒趋于均匀,雾化质量明显改善;在距喷嘴60 mm～140 mm的3个截面上,随着距离的增加,雾滴索特平均直径增大,雾滴趋于发散.     

Experimental observation of oil mist penetration ability in minimum quantity lubrication (MQL) spray

Journal of Mechanical Science and Technology - Minimum quantity lubrication (MQL) is an eco-friendly cooling and lubricating method that has its importance in machining sustainability. However, the...     

纳米粒子射流微量润滑磨削表面粗糙度预测与实验验证

随着人们环保意识的增强,微量润滑技术已经开始应用于磨削加工中,但是它的冷却效果有限,不能满足高磨削区温度强化换热的要求。而纳米粒子射流微量润滑新工艺的提出,可以有效地解决磨削区换热问题,同时又增强了砂轮与工件界面的润滑特性。针对在纳米粒子射流微量润滑磨削条件下磨削工件表面粗糙度预测,提出一种用于测量砂轮表面形貌的装置以及对磨削工件表面形貌进行模拟仿真的方法。并以两种工件材料为研究对象进行表面形貌数值模拟和实验验证,结果表明该种预测方法能够较准确地对磨削加工工件表面粗糙度进行预测,对于磨削参数的选择具有一定的指导意义。     

Temperature field model and experimental verification on cryogenic air nanofluid minimum quantity lubrication grinding

Considering the poor lubricating effect of cryogenic air (CA) and inadequate cooling ability of nanofluid minimum quantity lubrication (NMQL), this work proposes a new manufacturing technique cryogenic air nanofluid minimum quantity lubrication (CNMQL). A heat transfer coefficient and a finite difference model under different grinding conditions were established based on the theory of boiling heat transfer and conduction. The temperature field in the grinding zone under different cooling conditions was simulated. Results showed that CNMQL exerts the optimal cooling effect, followed by CA and NMQL. On the basis of model simulation, experimental verification of the surface grinding temperature field under cooling conditions of CA, MQL, and CNMQL was conducted with Ti–6Al–4V as the workpiece material. Simultaneously, CNMQL exhibits the smallest specific tangential and normal grinding forces (2.17 and 2.66 N/mm, respectively). Further, the lowest grinding temperature (155.9 °C) was also obtained, which verified the excellent cooling and heat transfer capabilities of CNMQL grinding. Furthermore, the experimental results were in agreement with theoretical analysis, thereby validating the accuracy of the theoretical model.     

The effect of minimum quantity lubrication in the intermittent turning of magnesium based on vibration signals

The present work shows an experimental investigation on intermittent turning based on vibration signals. The dependence of vibrations on the feed rate, minimum quantity lubrication (MQL) flow rate and the type of the interruption of the workpiece is evaluated. The results indicate that a part of the vibrations depends on the flow rate of the MQL system and its interaction with the feed rate, finding no dependency on the type of interruption. The influence of the MQL system is greater when machining at the lower feed rate. In addition, a strong relation between surface roughness and vibrations is identified. However, this relation is quite different depending on the environment used. In general, under dry conditions, the higher the vibrations the higher the surface roughness, while the opposite occurs when the MQL system is used.     

干式切削和微量润滑条件下的螺纹车削机理分析及试验研究

通过试验研究的方法,针对干式切削和微量润滑两种绿色切削方式下的外螺纹车削机理进行分析研究.首先对试验设计进行了详细介绍;然后通过试验对比研究,发现微量润滑相比干式切削能够有效减小切削力、减少切屑非自由面类鳞刺现象、减缓切屑内部裂纹产生.     

Influence of minimum quantity lubrication parameters on tool wear and surface roughness in milling of forged steel

The minimum quantity of lubrication (MQL) technique is becoming increasingly more popular due to the safety of environment.Moreover,MQL technique not only leads to economical benefits by way of saving ...