Implications of the reduction of cutting fluid in drilling AISI P20 steel with carbide tools

The machining of hardened steel is becoming increasingly important in manufacturing processes. Machined parts made with hardened steel are often subjected to high service demands, which require great resistance and quality. The machining of this material submits the tools to high mechanical and thermal loads, which increases the tool wear and affects the surface integrity of the part. In that context, this work presents a study of drilling of AISI P20 steel with carbide tools, analyzing the effects on the process caused by the reduction of cutting fluid supply and its relation with the tool wear and the surface integrity of the piece. The major problem observed in the tests was a difficulty for chips to flow through the drill flute, compromising their expulsion from the hole. After a careful analysis, a different machining strategy was adopted to solve the problem.     

基于刀具沿进给方向蠕动式进给的数控加工技术研究

通过对数控加工中存在的问题分析,提出了一种在数控加工中,刀具在被加工工件曲面上沿进给方向蠕动式切削加工的方珐,通过刀具与工件时续分离和切削,改善了工艺系统的刚性,从而使工件的加工精度得到改善,并具体从被加工工件的几何形状、切削过程中刀具受力情况及切削区的切削热释放情况方面,分析了采用该方珐对加工精度的改善情况。     

Deformation behaviour of sintered silicon–copper steel preforms of various aspect ratios during cold upsetting

This paper presents the optimization of the face milling process of 7075 aluminum alloy by using the gray relational analysis for both cooling techniques of conventional cooling and minimum quantity lubrication (MQL), considering the performance characteristics such as surface roughness and material removal rate. Experiments were performed under different cutting conditions, such as spindle speed, feed rate, cooling technique, and cutting tool material. The cutting fluid in MQL machining was supplied to the interface of work piece and cutting tool as pulverize. An orthogonal array was used for the experimental design. Optimum machining parameters were determined by the gray relational grade obtained from the gray relational analysis.     

基于刀具进让式进给数控加工技术的研究

通过分析常规数控加工中存在的问题,提出了一种刀具在进给方向上可进让式进给切削工件曲面轮廓的新工艺方法,建立了进让式进给切削数学模型,并从被加工工件的几何形状、切削过程中刀具受力情况及切削区的切削热释放情况等方面,具体分析了采用该方法对加工精度的改善情况,并给出了算法步骤。试验结果表明,新方法有利于减小工艺系统的变形,显著提高了工件的加工精度。     

高合金不锈钢的干车削和近干车削研究

高合金不锈钢具有强度高、韧性好、耐腐蚀等优良性能而得到日益广泛的应用,但是其难加工性同时也对切削技术提出了更高的要求.干切削因具有对环境和人体无害、经济性好等优点成为金属加工技术的主要发展方向之一.文中对高合金不锈钢Y12Cr17和16Cr17Ni3的干车削和近干车削中,切削参数和切削材料对刀具磨损和工件表面质量的影响进行了深入研究.结果表明,通过选择适当的切削参数、刀具材料以及刀具涂层,可以很好地实现高合金不锈钢的干车削加工,并能获得比传统乳化剂加工更小的磨损值和更好的工件表面质量.     

A new method for heat measurement during high speed machining

The cutting temperature and temperature distribution along the rake face of cutting tool and work piece is an essential factor in study of machining processes due to its effect on surface quality, tool life, tolerances, metallurgical behavior and chip-removing rate. Several methods have been introduced to measure temperature during machining, such as the thermocouple technique, infrared camera and metallurgical methods. Each of these methods has some advantages and limitations. In this article, an infrared high-speed sensor with specially designed software has been used to measure the transferred heat to the work piece during high speed machining (HSM) of bronze alloys. The results revealed that this system enhances accuracy and reduces the number of tests required.     

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.     

Selection of an optimal parametric combination for achieving a better surface finish in dry milling using genetic algorithms

In machining, coolants improve machinability, increase productivity by reducing tool wear and extend tool life. However, due to ecological and human health problems, manufacturing industries are now being forced to implement strategies to reduce the amount of cutting fluids used in their production lines. A trend that has emerged to solve these problems is machining without fluid – a method called dry machining – which has been made possible due to technological innovations. This paper presents an experimental investigation of the influence of tool geometry (radial rake angle and nose radius) and cutting conditions (cutting speed and feed rate) on machining performance in dry milling with four fluted solid TiAlN-coated carbide end mill cutters based on Taguchi’s experimental design method. The mathematical model, in terms of machining parameters, was developed for surface roughness prediction using response surface methodology. The optimization is then carried out with genetic algorithms using the surface roughness model developed and validated in this work. This methodology helps to determine the best possible tool geometry and cutting conditions for dry milling.     

Optimization of machining parameters using genetic algorithm and experimental validation for end-milling operations

Optimization of cutting parameters is valuable in terms of providing high precision and efficient machining. Optimization of machining parameters for milling is an important step to minimize the machining time and cutting force, increase productivity and tool life and obtain better surface finish. In this work a mathematical model has been developed based on both the material behavior and the machine dynamics to determine cutting force for milling operations. The system used for optimization is based on powerful artificial intelligence called genetic algorithms (GA). The machining time is considered as the objective function and constraints are tool life, limits of feed rate, depth of cut, cutting speed, surface roughness, cutting force and amplitude of vibrations while maintaining a constant material removal rate. The result of the work shows how a complex optimization problem is handled by a genetic algorithm and converges very quickly. Experimental end milling tests have been performed on mild steel to measure surface roughness, cutting force using milling tool dynamometer and vibration using a FFT (fast Fourier transform) analyzer for the optimized cutting parameters in a Universal milling machine using an HSS cutter. From the estimated surface roughness value of 0.71 μm, the optimal cutting parameters that have given a maximum material removal rate of 6.0×10³ mm³/min with less amplitude of vibration at the work piece support 1.66 μm maximum displacement. The good agreement between the GA cutting forces and measured cutting forces clearly demonstrates the accuracy and effectiveness of the model presented and program developed. The obtained results indicate that the optimized parameters are capable of machining the work piece more efficiently with better surface finish.     

Some studies on hard turning of AISI 4340 steel using multilayer coated carbide tool

Hard turning with multilayer coated carbide tool has several benefits over grinding process such as, reduction of processing costs, increased productivities and improved material properties. The objective was to establish a correlation between cutting parameters such as cutting speed, feed rate and depth of cut with machining force, power, specific cutting force, tool wear and surface roughness on work piece. In the present study, performance of multilayer hard coatings (TiC/TiCN/Al₂O₃) on cemented carbide substrate using chemical vapor deposition (CVD) for machining of hardened AISI 4340 steel was evaluated. An attempt has been made to analyze the effects of process parameters on machinability aspects using Taguchi technique. Response surface plots are generated for the study of interaction effects of cutting conditions on machinability factors. The correlations were established by multiple linear regression models. The linear regression models were validated using confirmation tests. The analysis of the result revealed that, the optimal combination of low feed rate and low depth of cut with high cutting speed is beneficial for reducing machining force. Higher values of feed rates are necessary to minimize the specific cutting force. The machining power and cutting tool wear increases almost linearly with increase in cutting speed and feed rate. The combination of low feed rate and high cutting speed is necessary for minimizing the surface roughness. Abrasion was the principle wear mechanism observed at all the cutting conditions.     

Evaluation of performance of nanofluid using multiwalled carbon nanotubes for machining of Ti–6AL–4V

Machining of titanium alloys generate very high temperature in the cutting zone. This results in rapid tool wear and poor surface properties. Therefore, improvement in cutting performance in machining of titanium alloys is very much dependent on effectiveness of the cooling strategies applied. In the present work, performance of nanofluid using multiwalled carbon nanotubes (MWCNTs) dispersed in distilled water and sodium dodecyl sulfate (SDS) as surfactant is evaluated for turning operation on Ti–6Al–4V workpieces. Turning operations were carried out under three different conditions – dry, with conventional cutting fluid and with nanofluid. Nanofluid application was limited to 1 L/h and it was applied at the tool tip through gravity feed. Various machining responses like cutting force, surface finish and tool wear were analyzed while turning at optimum cutting parameters as 150 m/min, 0.1 mm/rev and 1 mm depth of cut. Later on, machining performance of nanofluid is confirmed at low cutting speed of 90 m/min. Nanofluid outperformed conventional cutting fluid with 34% reduction in tool wear, average 28% drop in cutting forces and 7% decrease in surface roughness at cutting speed of 150 m/min.     

五轴联动数控加工的刀具路径优化方法研究

为解决五轴联动加工复杂曲面过程中的刀具路径不连续问题,提出了五轴数控的刀具路径优化方法。通过五轴NC代码的坐标变换还原有效切削路径,对切削路径进行误差约束下的非均匀有理B样条(NURBS)曲线拟合。对旋转轴路径采用五次样条曲线进行插值,建立切削路径和旋转轴路径的参数映射关系,通过机床逆运动变换求解C2连续的平动轴路径。实验表明,经过该方法优化后,切削路径和各驱动轴运动路径具有良好的平滑性,显著提高了五轴加工曲面精度和表面质量。     

42CrMo合金结构钢的干切削和近干切削研究

合金结构钢以其生产规模大、易于加工、性能多样、价格低廉、使用方便和便于回收等特征成为重要的钢铁材料。干切削和微量润滑加工技术是目前金属加工技术的主要发展方向之一,也是实现绿色制造的关键技术。文中对合金结构钢42CrMo在干切削和近干切削加工条件下,切削参数和切削材料对刀具磨损和工件表面质量的影响进行了比较深入的研究。结果表明,通过选择适当的切削参数,刀具材料和刀具涂层,可以很好地实现这种材料的干切削加工,甚至可以获得比传统乳化剂加工更低的刀具磨损和更好的表面质量。     

The influence of solid lubricant for improving tribological properties in turning process

Control of machining zone temperature is achieved by providing effective cooling and lubrication. Though cutting fluids are widely used to carry away the heat in metal cutting, they cannot be recommended in the light of ecological and economic manufacture. Hence, there arises a need to identify eco‐friendly and user‐friendly alternatives to conventional cutting fluids. The present work features a specific study of the application of molybdenum disulphide as solid lubricant for improving tribological properties in turning and to overcome the limitations that arise with the use of cutting fluids or while dry machining. An experimental setup developed has been used to maintain constant flow rate of solid lubricant powder continuously on to the workpiece and tool interface zone. Results are encouraging with overall improvement in machining properties in terms considered parameters as compared to wet and dry techniques, due to the reduction in friction at tool/work and tool/chip interface. Copyright © 2010 John Wiley & Sons, Ltd.     

静电冷却干式切削钛合金TC4的刀具磨损试验研究

钛合金TC4的切削加工性差,采用极压切削液会污染环境,不符合可持续发展要求,故提出了静电冷却的绿色切削技术,研制了空气电离装置及供气系统,分别在干切、乳化液和静电冷却条件下,对硬质合金刀具YG8切削钛合金TC4时的后刀面磨损进行了试验研究,给出了后刀面磨损曲线,建立了切削速度与刀具使用寿命的关系式。结果表明,静电冷却可减少刀具磨损,提高刀具寿命,是一种清洁的绿色冷却切削工艺。     

Experimental study on minimal nanolubrication with surfactant in the turning of titanium alloys

The superiority of minimal nanolubrication for effective, efficient and cleaner machining environment has been widely discussed in the literature. However, due to their high surface energy, nanoparticles coagulate or agglomerate easily, which makes it difficult to disperse them in the base fluid. Hence, the addition of a small amount of surfactant should be able to overcome this issue. This research elucidates and extends fundamental knowledge regarding the effect of a sodium dodecyl benzene sulfonate surfactant mixed with different nanoparticle concentrations towards the sustainable machining of titanium alloy using design of experiment methodology. The experimental results indicate that the inclusion of a sodium dodecyl benzene sulfonate surfactant in aluminium oxide nanolubricant provides the best lubricating properties for the machining of the titanium alloy. At 0.4 wt% of nanoparticles and a feed rate of 0.1 mm/rev, minimum values of surface roughness and power consumption can be achieved. Meanwhile, minimal tool wear can be attained by application of a 0.6 wt% nanoparticle concentration and 0.1 mm/rev feed rate. Further statistical analyses emphasized that the feed rate was the most significant factor that influenced the surface roughness and power consumption, while the mixture of nanoparticles with surfactant and feed rate has the greatest effect on the tool wear resistance of the cutting insert.     

Investigation and optimization of lubrication parameters in high speed turning of superalloy Inconel 718

Dry machining is sometimes less effective when higher machining efficiency, better surface finish quality, and severe cutting conditions are required. For these situations, semi-dry operations utilizing very small amount of cutting fluids called minimum quantity lubrication is expected to become a powerful tool and played a significant role in a number of practical applications. It has been observed from the literature survey that a systematic research work has to be carried out to determine the optimum quantity of lubricant with appropriate cutting conditions for achieving better machinability characteristics of a material. Hence, an attempt has been made in this paper to enhance the machinability characteristics in high speed turning of superalloy Inconel 718 using quantity of lubricant, delivery pressure at the nozzle, frequency of pulses, direction of application of cutting fluid, cutting speed, and feed rate as the process parameters. Results indicated that the use of optimized minimum quantity lubrication parameters under pulsed jet mode leads to lower cutting force, cutting temperature, and flank wear.     

Phenomenological investigation of cutting oils: Antifriction and antiwear behaviour at low contact temperatures

The basic reason for the use of cutting fluids in machining processes is to increase cutting tool life and to decrease machining costs. An experimental simulation of tribological processes representing rear cutting tool contact was carried out in a ‘block‐on‐disc’ (BOD) tribotester. The coefficient of friction and block wear were measured under boundary (discontinuous fluid film) and elastohydrodynamic (quasi‐continuous fluid film) lubrication conditions for neat and semi‐synthetic cutting oils. Interesting data were obtained concerning a further cutting fluid classification, which is helpful for optimal cutting fluid selection via their antiwear and antifriction characteristics.     

A review on the use of dielectric fluids and their effects in electrical discharge machining characteristics

Electrical discharge machining (EDM) is one of the earliest non-traditional machining processes. EDM process is based on thermoelectric energy between the work piece and an electrode. In electrical discharge machining (EDM), a process utilizing the removal phenomenon of electrical discharge in dielectric, the working fluid plays an important role affecting the material removal rate and the properties of the machined surface. Choosing the right dielectric fluid is critical for successful operations. This paper presents a literature survey on the use of dielectric fluids and also their effects in electrical discharge machining characteristics.     

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%.