基于毛细管理论的MQL理论模型及应用

MQL切削加工技术是一项新型的绿色环保加工技术,使用极微量的切削液可以取得良好的加工效果,从而达到保护环境、降低成本的目的.分析了MQL切削加工中切削液的作用原理,基于毛细管理论建立了MQL的理论模型,并进行了MQL精密车削试验,为进一步丰富和发展MQL切削技术奠定了坚实基础.     

基于MQL的切削加工技术应用

在金属切削加工过程中,切削液发挥着冷却、润滑、排屑和防锈等作用,但其排放会对环境造成严重污染。微量润滑技术(MQL)是将压缩气体与微量润滑油混合汽化后喷射到加工区域,可代替传统切削液,在刀具与工件间的加工部位形成有效润滑,减缓刀具磨损。作为新兴的绿色清洁切削加工技术,微量润滑技术具有广阔应用前景。本文介绍了切削加工机理和切削液在切削加工中的作用,通过对比微量润滑、水溶性切削液和切削油性冷却等常见润滑技术的优缺点,分析了MQL替代传统切削液在切削加工中的利弊,并通过分析MQL在高速加工、铝合金加工及断续加工等方面的应用,探讨了MQL技术的发展趋势及发展过程中凾待解决的问题。     

水基GO/Al2O3混合纳米流体微量润滑的摩擦性能及加工特性

以植物型润滑油为切削液的微量润滑(Minimum quantity lubrication,MQL)技术因表现出优良的加工性和环境友好性而备受关注.然而,由于油基切削液的冷却能力低,传统油基MQL往往会产生高的切削温度.水基切削液的冷却性能好,但润滑能力不如油基切削液.为了提高水基切削液应用于MQL时的润滑性能,提出了一种以氧化石墨烯/氧化铝(GO/Al2 O3)混合水基纳米流体为切削液的MQL技术,并对其摩擦磨损和加工特性进行了对比研究.为了获得较佳的减摩抗磨性能,优选了GO/Al2 O3的质量比.结果 表明,水基GO/Al2O3混合纳米流体MQL与单一GO或Al2O3纳米流体MQL相比,摩擦系数和磨斑直径显著降低,加工特性提升明显,且表现出与传统植物油MQL相当的加工特性.水基混合纳米流体MQL的优异性能归因于GO/Al2O3混合纳米颗粒渗透进入摩擦界面,形成由GO自润滑层和Al2O3润滑薄膜组成的复合保护膜,阻止了摩擦界面的直接接触,从而提高了润滑能力.     

水基GO/Al2O3混合纳米流体微量润滑的摩擦性能及加工特性

以植物型润滑油为切削液的微量润滑(Minimum quantity lubrication,MQL)技术因表现出优良的加工性和环境友好性而备受关注.然而,由于油基切削液的冷却能力低,传统油基MQL往往会产生高的切削温度.水基切削液的冷却性能好,但润滑能力不如油基切削液.为了提高水基切削液应用于MQL时的润滑性能,提出了一种以氧化石墨烯/氧化铝(GO/Al2 O3)混合水基纳米流体为切削液的MQL技术,并对其摩擦磨损和加工特性进行了对比研究.为了获得较佳的减摩抗磨性能,优选了GO/Al2 O3的质量比.结果 表明,水基GO/Al2O3混合纳米流体MQL与单一GO或Al2O3纳米流体MQL相比,摩擦系数和磨斑直径显著降低,加工特性提升明显,且表现出与传统植物油MQL相当的加工特性.水基混合纳米流体MQL的优异性能归因于GO/Al2O3混合纳米颗粒渗透进入摩擦界面,形成由GO自润滑层和Al2O3润滑薄膜组成的复合保护膜,阻止了摩擦界面的直接接触,从而提高了润滑能力.     

不同MQL安置方式对高速精密车削的影响研究

为比较不同的MQL安置方式对高速精密车削加工的影响,使用德国某公司的超精密机床SB-CNC对轴承钢GCr15分别进行干式、切削液外置供给式MQL以及切削液内置供给式MQL切削试验。通过Kistler加速度传感器和压电式力传感器分别对车刀在加工过程中的径向振动信号和刀尖的三向切削力信号进行采集,并对采集到的信号做时域和频域分析。结果显示,两种MQL润滑方式都对减小切削力和加工中的低频颤振有所抑制,其中,内置式MQL在抑制颤振方面比外置式MQL更有优势,二者在减小切削力能力方面则未见明显区别。     

基于环保的"绿色"冷却技术的新进展

金属切削液 (ＣｕｔｔｉｎｇＦｌｕｉｄ)是指用于金属切削 (磨削 )加工的冷却液。金属切削液作为机械加工重要的配套材料 ,它在机械加工中主要起冷却 ,润滑 ,清洗和防锈四个作用。在过去以及今后相当长的一段时期内 ,金属切削液在金属切削加工中的使用仍是金属切削加工中主要的冷却方法。然而 ,随着切削液的大量使用 ,切削废液排放对环境和生态造成了巨大的副作用。如何降低切削液对环境的不良影响 ,已成为实现机械制造工业可持续发展过程中亟待解决的难题之一。1　目前切削液使用存在的负面问题切削液由于其重要作用 ,在机械加工中得到了广…     

少切削液切削机理的研究

针对传统的大量浇注式切削加工存在切削液浪费大、成本高、污染环境、危害工人健康等问题,采用切削试验与ANSYS软件仿真相结合的方法,研究了传统浇注式和MQL切削加工中切削液的作用效果,系统地揭示出切削液浇注方位、作用靶距、流量、流速等对加工效果的影响及其变化规律,探索了少切削液加工的新途径。     

MQL技术在内排屑深孔钻削加工中的应用

针对传统浇注式内排屑深孔钻削加工方法(BTA或DF)存在着切削液消耗量大、生产成本高、污染环境及危害操作者身体健康等问题,本文提出了将MQL技术(最小润滑技术)应用于内排屑深孔加工的方法(即亚干式深孔加工),并对MQL切削加工中切削液的作用与效果进行了分析。通过亚干式深孔钻削试验,确定出水溶性切削液具有良好的雾化效果,并且加工系统具有良好的冷却及排屑效果。针对刀具磨损较大等问题,提出了采用油液混合雾化以及低温冷风的方法,以提高刀具的润滑性和冷却效果。     

MQL外圆车削数值模拟及流场分析

基于流体力学理论及流体分析软件FLUENT建立了最小量润滑(MQL)外圆车削模型,模拟了MQL喷雾射流过程,分析了车削后刀面楔形区的流体压强及静压力的分布特性,分析了MQL喷雾形态,结果表明:MQL压缩空气较强的气压和较高的流速对楔形区的流场有很大的影响;楔形区的流场特性对MQL切削液雾滴的运动和渗透有着较大的影响,楔形区的负压差能够促进切削液喷雾的运动,切削液雾滴粒径在集中在(1~20)μm之间,并按一定的规律分布。这对MQL切削参数及雾滴回收装置的研究有一定的参考意义。     

切削中运用MQL技术大势所趋

基于生态及环保的需求,切削加工中的微量润滑(MQL)技术成为当今研究的焦点。该技术是一种有效的绿色制造技术,切削液以高速雾粒供给,增加了润滑剂的渗透性,提高了冷却润滑效果,改善了工件的表面加工质量,因此这种绿色制造技术的推广和运用必然大势所趋。     

Experimental Investigation on the Compatibility of Nanoparticles with Vegetable Oils for Nanofluid Minimum Quantity Lubrication Machining

Several health and environmental related issues caused by the application of traditional cutting fluids in machining can be solved by implementing eco-friendly technologies such as minimum quantity lubrication (MQL). Moreover, nanofluid MQL has been proposed to enhance the cooling/lubricating properties of pure MQL and displays significantly good results for machinability. However, the mechanism on compatibility of nanoparticles with cutting fluids has not been explored. In this study, nanoparticles with different hardness and vegetable oils with different viscosity were selected for nanofluids preparation. The end milling experiments were carried out on 7050 material by applying MQL with particularly prepared nanofluids. The cutting force and surface roughness were measured corresponding to the machining performance. The compatibility of hardness of nanoparticles with viscosity of base fluids has been evaluated, and the mechanism has been analyzed by new-designed tribology tests. Results show that canola oil-based diamond nanofluids MQL exhibit the lowest cutting force and natural77 oil-based diamond nanofluids perform the lowest surface roughness with reduction of 10.71 and 14.92%, respectively, compared to dry machining condition. The research is novel and contributes to the machining of such materials at the industry level.     

Minimal quantity lubrication-MQL in grinding of Ti–6Al–4V titanium alloy

Titanium and its alloys are attractive materials due to their unique high strength–weight ratio that is maintained at elevated temperatures and their exceptional corrosion resistance. The major application of titanium has been in the aerospace industry. On the other hand, titanium and its alloys are notorious for their poor thermal properties and are classified as difficult-to-machine materials. The problems that arise during grinding of titanium alloys are attributed to the high specific energy and high grinding zone temperature. Significant progress has been made in dry and semidry machining recently, and minimal quantity lubrication (MQL) machining in particular has been accepted as a successful semidry application because of its environmentally friendly characteristics. A number of studies have shown that MQL machining can show satisfactory performance in practical machining operations. However, there has been few investigation of MQL grinding of special alloys like titanium alloys and the cutting fluids to be used in MQL grinding of these alloys. In this study, vegetable and synthetic esters oil are compared on the basis of the surface quality properties that would be suitable for MQL applications. The cutting performance of fluids is also evaluated using conventional wet (fluid) grinding of Ti–6Al–4V. As a result, synthetic ester oil is found to be optimal cutting fluids for MQL grinding of Ti–6Al–4V.     

Experimental evaluation on the effect of electrostatic minimum quantity lubrication (EMQL) in end milling of stainless steels

The machining of stainless steels is very challenging owing to their high toughness and low thermal conductivity, causing high cutting temperatures and rapid tool wear. Conventionally, metalworking fluids in flood form are used during the process to improve surface quality and tool life; however, their use raises issues including environmental pollution and economic concerns. Therefore, an electrostatic minimal quantity lubrication (EMQL) technology was developed to reduce the consumption of metalworking fluids. EMQL is a near-dry machining technology utilizing the synergetic effects between electrostatic spraying and minimum quantity lubrication (MQL), wherein the lubricant is to apply in a form of fine, uniform and highly penetrable and wettable mist droplets directly to the cutting zone. This study investigates the effect of EMQL in end milling of AISI 304 stainless steel in comparison with dry, wet and MQL machining. The results suggest that EMQL reduces tool wear and cutting force, prolongs tool life considerably and enhances surface finish compared with conventional wet and MQL machining. scanning electron microscopy and Energy-dispersive X-ray spectroscopy analyses show that EMQL considerably reduces adhesive and abrasive wear on the flank face because of the lower friction and heat generation resulting from more efficient entry of the lubricant into the cutting interfaces.     

EVALUATION AND COMPARISON OF LUBRICANT PROPERTIES IN MINIMUM QUANTITY LUBRICATION MACHINING

Minimum Quantity Lubrication (MQL) machining involves the application of a minute amount of an oil-based lubricant to the machining process in an attempt to replace the conventional flood coolant system. Understanding the correlations between fluid properties and MQL performance can help in selecting lubricants from a variety of choices without going through extensive machining tests. This study compared nine different MQL fluids in terms of their physical properties, wettability, tribological properties (lubricity and extreme pressure (EP) properties), mist characteristics and machinability to determine the correlation of measured properties and MQL drilling and reaming performance. Results show that low fluid viscosity, high mist concentration, large mist droplet diameter and high wettability were best correlated with good machinability. Although it is difficult to draw strong relationships, the optimal machining in a mild cutting condition was found with the low viscosity fluids, which may also have the highest mist concentration, largest drops and best wettability.     

OPTIMAL MQL AND CUTTING CONDITIONS DETERMINATION FOR DESIRED SURFACE ROUGHNESS IN TURNING OF BRASS USING GENETIC ALGORITHMS

The evolving concept of minimum quantity of lubrication (MQL) in machining is considered as one of the solutions to reduce the amount of lubricant to address the environmental, economical and ecological issues. This paper investigates the influence of cutting speed, feed rate and different amount of MQL on machining performance during turning of brass using K10 cemented carbide tool. The experiments have been planned as per Taguchi's orthogonal array and the second order surface roughness model in terms of machining parameters was developed using response surface methodology (RSM). The parametric analysis has been carried out to analyze the interaction effects of process parameters on surface roughness. The optimization is then carried out with genetic algorithms (GA) using surface roughness model for the selection of optimal MQL and cutting conditions. The GA program gives the minimum values of surface roughness and the corresponding optimal machining parameters.     

Theoretical and experimental study of the chatter vibration in wet and MQL machining conditions in turning process

Turning is one of the most commonly used cutting processes for manufacturing components in production engineering. The turning process, in some cases, is accompanied by intense relative movements between tool and workpiece, which is called chatter vibrations. Chatter has been identified as a detrimental problem that adversely impacts surface finish, tool life, process productivity, and dimensional accuracy of the machined part. Cooling/Lubrication in the turning process is normally done for some reasons, including friction and force reduction, temperature decrement, and surface finish improvement. Wet cooling is a traditional cooling/lubrication process that has been used in machining since the past. Besides, a variety of new cooling and lubricating approaches have been developed in recent years, such as the minimum quantity lubrication (MQL), cryogenic cooling, nanolubrication, etc., due to ecological issues. Despite the importance of cooling/lubrication in machining, there is a lack of research on chatter stability in the presence of cutting fluid in cutting processes. In this study, the chatter vibration in turning process for two cooling/lubrication conditions of conventional wet and MQL is investigated. An integrated theoretical model is used to predict both the metal cutting force and the chatter stability lobe diagram (SLD) in turning process. This model involves deriving a math equation for predicting metal cutting force for both wet and MQL conditions using experimental training force data and a Genetic Expression Programming (GEP)-based regression model. Also, the traditional single degree of freedom chatter model is used here for predicting the SLDs. The chatter model is discussed and verified with experimental tests. Then, the experimental results of the tool's acceleration signal, work surface texture, surface roughness, chip shape, and tool wear are presented and compared for wet and MQL conditions. The results of this study show that the cooling/lubrication systems such as wet or MQL have a considerable effect on the SLDs. Also, the predicted results of metal cutting force and SLD for both wet and MQL techniques are in good agreement with the experimental data. Therefore, it is recommended that for each lubrication condition including wet, or MQL, the SLD be determined to achieve higher machinability.     

最少量润滑切削技术(MQL)--经济有效的绿色制造方法

综述了由切削液引起的人体病理现象；综合分析了替代或减少切削液用量的干切削、低温冷却、冷风冷却等绿色加工技术的加工效率、经济性及环境友好性；提出最少量润滑切削技术（MQL）是实现清洁、高效制造的最佳工艺方法。     

EFFECTS OF COOLANT SUPPLY METHODS AND CUTTING CONDITIONS ON TOOL LIFE IN END MILLING TITANIUM ALLOY

Titanium machining poses a great challenge to cutting tools due to its severe negative influence on tool life primarily due to high temperature generated and strong adhesion in the cutting area. Thus, various coolant supply methods are widely used to improve the machining process. On account of this, tool life and cutting force are investigated based on dry cutting, flood cooling, and minimum quantity lubrication (MQL) techniques. The experimental results show that MQL machining can remarkably and reliably improve tool life, and reduce cutting force due to the better lubrication and cooling effect.     

EFFECTS OF COOLANT SUPPLY METHODS AND CUTTING CONDITIONS ON TOOL LIFE IN END MILLING TITANIUM ALLOY

Titanium machining poses a great challenge to cutting tools due to its severe negative influence on tool life primarily due to high temperature generated and strong adhesion in the cutting area. Thus, various coolant supply methods are widely used to improve the machining process. On account of this, tool life and cutting force are investigated based on dry cutting, flood cooling, and minimum quantity lubrication (MQL) techniques. The experimental results show that MQL machining can remarkably and reliably improve tool life, and reduce cutting force due to the better lubrication and cooling effect.