Optimization of electrical discharge machining process parameters for Al6061/cenosphere composite using grey-based hybrid approach

Fly ash has congregated considerable attention as a potential reinforcement for aluminum matrix composites (AMCs) to enhance selective properties and reduce the cost of fabrication. However, poor machinability of such AMCs limits their application. The present study focuses on the preparation of cenosphere fly ash reinforced Al6061 alloys by compo casting method. X-ray diffraction analysis of the prepared AMCs exposes the presence of cenosphere particles without any formation of other intermetallic compounds. In this study, electrical discharge machining (EDM) was engaged to examine the machinability of the prepared metal matrix composite (MMCs). The measured performance characteristics for the various combinations of input process parameters were considered to be MRR, EWR and SR. Face centered central composite design (CCD) of response surface method (RSM) was employed to design the number of experimental trials required and a hybrid approach of grey-based response surface methodology (GRSM) was imposed for predicting the optimal combination of processing parameter in EDM process. Generous improvement was observed in the performance characteristics obtained by employing both the optimal setting of machining parameters. The optical 3D surface profile graphs of the ED machined surface also revealed the improvement in surface quality and texture employing the optimal processing conditions proposed by hybrid GRSM approach.     

电火花加工工艺参数的优化及其应用

论述了在电火花加工中工艺参数对工艺效果的影响关系和目前常用的工艺参数优化的方法。介绍了KBE技术及其在电火花加工工艺参数优化中的应用前景，提出应用KBE技术将为电火花加工的工艺参数优化提供比较完美的解决方案。     

混合铝基复合材料钻削工艺参数的优化(英文)

采用Taguchi方法和灰色关联分析对Al356/SiC-云母混合金属基复合材料的钻削工艺参数进行优化。实验采用L18正交阵列,在计算机的控制立式机床上进行。考察的钻削性能指标包括轴向力、表面粗糙度、刀具磨损和毛刺高度,对影响这些性能的钻削工艺参数进行了优化,包括轴转数、给进速度、钻头类型和云母质量分数。结果表明:给进速度和钻头类型是影响钻削过程的重要因素,通过这种方法可以有效地改进钻削工艺的性能。     

Optimization of process parameters of mechanical type advanced machining processes using genetic algorithms

Generally, unconventional or advanced machining processes (AMPs) are used only when no other traditional machining process can meet the necessary requirements efficiently and economically because use of most of AMPs incurs relatively higher initial investment, maintenance, operating, and tooling costs. Therefore, optimum choice of the process parameters is essential for the economic, efficient, and effective utilization of these processes. Process parameters of AMPs are generally selected either based on the experience, and expertise of the operator or from the propriety machining handbooks. In most of the cases, selected parameters are conservative and far from the optimum. This hinders optimum utilization of the process capabilities. Selecting optimum values of process parameters without optimization requires elaborate experimentation which is costly, time consuming, and tedious. Process parameters optimization of AMPs is essential for exploiting their potentials and capabilities to the fullest extent economically. This paper describes optimization of process parameters of four mechanical type AMPs namely ultrasonic machining (USM), abrasive jet machining (AJM), water jet machining (WJM), and abrasive-water jet machining (AWJM) processes using genetic algorithms giving the details of formulation of optimization models, solution methodology used, and optimization results.     

Optimization of machining parameters in magnetic force assisted EDM based on Taguchi method

A versatile process of electrical discharge machining (EDM) using magnetic force assisted standard EDM machine has been developed. The effects of magnetic force on EDM machining characteristics were explored. Moreover, this work adopted an L18 orthogonal array based on Taguchi method to conduct a series of experiments, and statistically evaluated the experimental data by analysis of variance (ANOVA). The main machining parameters such as machining polarity (P), peak current (I_p), pulse duration (τ_p), high-voltage auxiliary current (I_H), no-load voltage (V) and servo reference voltage (S_v) were chosen to determine the EDM machining characteristics such as material removal rate (MRR) and surface roughness (SR). The benefits of magnetic force assisted EDM were confirmed from the analysis of discharge waveforms and from the micrograph observation of surface integrity. The experimental results show that the magnetic force assisted EDM has a higher MRR, a lower relative electrode wear ratio (REWR), and a smaller SR as compared with standard EDM. In addition, the significant machining parameters, and the optimal combination levels of machining parameters associated with MRR as well as SR were also drawn. Moreover, the contribution for expelling machining debris using the magnetic force assisted EDM would be proven to attain a high efficiency and high quality of surface integrity to meet the demand of modern industrial applications.     

Surface characterization in ultra-precision machining of Al/SiC metal matrix composites using data dependent systems analysis

This paper presents a data dependent systems (DDSs) method for the analysis of surface generation in ultra-precision machining of Al/SiC metal matrix composites (MMCs). The DDS analysis provides a component by component wavelength decomposition of the surface roughness profile of the machined surface. A series of face cutting experiments was done on Al6061/15SiC_p MMCs under different cutting conditions. The cutting results indicate that the characteristics of the wavelength components analyzed by the DDS analysis method are correlated well with the surface generation mechanisms. Since the relative powers of the wavelength components are used to measure the contributions of the cutting mechanisms to the total roughness, this resolves the shortcomings of the conventional spectrum analysis method in characterizing the surface properties such as pits and cracks in ultra-precision machining of MMCs.     

Estimating the effect of cutting parameters on surface finish and power consumption during high speed machining of AISI 1045 steel using Taguchi design and ANOVA

The present paper outlines an experimental study to investigate the effects of cutting parameters on finish and power consumption by employing Taguchi techniques. The high speed machining of AISI 1045 using coated carbide tools was investigated. A combined technique using orthogonal array and analysis of variance was employed to investigate the contribution and effects of cutting speed, feed rate and depth of cut on three surface roughness parameters and power consumption. The results showed a significant effect of cutting speed on the surface roughness and power consumption, while the other parameters did not substantially affect the responses. Thereafter, optimal cutting parameters were obtained.     

Estimation of machine-tool dynamic parameters during machining operation through operational modal analysis

The stability of high-speed machining operations determines the reliability of machine tools and the quality of machined parts. Chatter-free cutting conditions are difficult to predict as they require accurately estimated dynamic modal parameters. A spectrogram analysis and impact tests for different configurations of the machine tools were conducted to compare the modal parameters at 0 rpm tests and during machining tests. Variations of between 2% and 8% were observed for the natural frequencies and between 2 and 10 times for the damping ratios.The operational modal analysis (OMA) is considered as a powerful tool for dynamic modal parameter estimations during machining operations. A complete methodology for applying this technique for machining operations was detailed. It was demonstrate how the OMA can be industrially exploited. The proposed approach was successfully applied during the high-speed machining of the 7075-T6 aluminum alloy to extract machine-tool parameters. Two different numerical approaches were used: the autoregressive moving average method (ARMA) and the least square complex exponential method (LSCE), both of which generated similar results. The dynamic parameters found using the operational modal analysis were used to predict machine dynamic stability lobes, and through experimental validation, it was shown that some depths of cut that are stable with standard stability lobes become unstable with dynamic stability lobes.     

灰度模糊算法优化Al-SiC-Gr混合金属基复合材料的加工参数

石墨颗粒增强金属基复合材料能够提供更好的切削加工性能和摩擦性能。用灰度模糊算法优化Al-SiC-Gr混合金属基复合材料的加工参数,以获得到具有优秀综合性能的材料。当混合金属基复合材料中SiC-Gr的质量分数分别为5%、7.5%和10%时,对应的拉伸强度分别为170、210和204 MPa。另外,与另外2种材料相比,Al-10%（SiC-Gr）复合材料具有更好的切削加工性能。与其他的灰度技术相比,灰度模糊逻辑算法在输出方面提高了推理的合理性,降低了不确定性。实验结果表明,在设置的相同加工参数下,与其他的灰度技术相比,灰度模糊逻辑算法的推理合理性从0.619提高到0.891,且同时保证材料具有更好的综合性能。     

Optimization of process parameters for in situ casting of Al/TiB2 composites through response surface methodology

The mathematical models were developed to predict the ultimate tensile strength (UTS) and hardness of Al/TiB₂ MMCs fabricated by in situ reaction process. The process parameters include temperature, reaction time and mass fraction of TiB₂. The in-situ casting was carried out based on three-factor five-level central composite rotatable design using response surface methodology (RSM). The validation of the model was carried out using ANOVA. The mathematical models developed for the mechanical properties were predicted at 95% confidence limit.     

Analysis of chip formation mechanism in machining of Al/SiCp metal matrix composites

Al/SiCp composites are known to cause a significant wear of cutting tools. But, with the use of PCD/CBN tools, machining can be continued over longer time duration. Nevertheless, the problem associated with the quality of machined surfaces such as pit marks and particle pull-out still persists. The quality of surface generated during machining can be easily related to the types of chips formed during machining of Al/SiCp composites as a function of processing conditions and composition of constituents in composites.     

Optimization of dry machining parameters for high-purity graphite in end milling process via design of experiments methods

This investigation applied the designs of experiments (DOE) approach to optimize parameters of a computer numerical control (CNC) in end milling for high-purity graphite under dry machining. The groove difference (i.e., dimensional accuracy of groove width) and the roughness average at the bottom plane of the inside groove (i.e., the plane of end milling) were studied. Planning of experiment was based on a Taguchi orthogonal array table. The analysis of variance (ANOVA) was adapted to identify the most influential factors on the CNC end milling process. Simultaneously, applying regression analysis a mathematical predictive model for predictions of the groove difference and the roughness average has been developed in terms of cutting speed, feed rate, and depth of cut. The feed rate is found to be the most significant factor affecting the groove difference and the roughness average in end milling process for high-purity graphite. Additionally, the tool worn surfaces after machining were examined by the optical zoom scope (OZS).     

2A14高强铝合金电子束焊接工艺优化及接头组织分析

通过正交试验和分析的方法研究了电子束焊接中主要工艺参数：电子束流、焊接速度、焦点位置、扫描图形、图形尺寸以及扫描频率对焊接接头熔深和熔宽的影响规律．结果表明,电子束流和焦点位置对接头熔深和熔宽的影响最为显著,其次为焊接速度,而束流扫描参数,如图形、尺寸和频率对熔深的影响相对较小．利用优化的电子束参数组合焊接得到成形和质...     

Electrical discharge machining of Ti6Al4V with a bundled electrode

The aim of this study is to investigate an efficient Ti6Al4V electrical discharge machining (EDM) process with a bundled die-sinking electrode. The feasibility of machining Ti6Al4V with a bundled electrode was studied and its effect on EDM performance was compared experimentally using a solid die-sinking electrode. The simulation results explain the high performance of the EDM process with a bundled electrode by through the use of multi-hole inner flushing to efficiently remove molten material from the inter-electrode gap and through the improved ability to apply a higher peak current. A 3-factor, 3-level experimental design was used to study the relationships between 2 machining performance parameters (material removal rate: MRR, tool wear ratio: TWR) and 3 machining parameters (fluid flow rate, peak current and pulse duration). The main effects and influences of the 2-factor interactions of these parameters on the performances of the EDM process with the bundled electrode are discussed.     

Characteristic evaluation of Al2O3/CNTs hybrid materials for micro-electrical discharge machining

The characteristic evaluation of aluminum oxide (Al₂O₃)/carbon nanotubes (CNTs) hybrid composites for micro-electrical discharge machining (EDM) was described. Alumina matrix composites reinforced with CNTs were fabricated by a catalytic chemical vapor deposition method. Al₂O₃ composites with different CNT concentrations were synthesized. The electrical characteristic of Al₂O₃/CNTs composites was examined. These composites were machined by the EDM process according to the various EDM parameters, and the characteristics of machining were analyzed using field emission scanning electron microscope (FESEM). The electrical conductivity has a increasing tendency as the CNTs content is increased and has a critical point at 5% Al₂O₃ (volume fraction). In the machining accuracy, many tangles of CNT in Al₂O₃/CNTs composites cause violent spark. Thus, it causes the poor dimensional accuracy and circularity. The results show that conductivity of the materials and homogeneous distribution of CNTs in the matrix are important factors for micro-EDM of Al₂O₃/CNTs hybrid composites.     

变参数激光三维加工方法及试验

介绍了在一次走刀中连续改变加工参数的激光加工新方法，研究变加工条件对切口几何尺寸的影响。在试验切割过程中，调整激光移动速度、输入功率和相对试件表面的焦点位置，来模拟激光三维切割实际状态，进一步分析得出变参数激光加工材料的去除规律。试验参数设计分为线性和二次方两种输入方式，证明了该方法的有效性。     

Effect of machining parameters in ultrasonic vibration cutting

The ultrasonic vibration cutting (UVC) method is an efficient cutting technique for difficult-to-machine materials. It is found that the UVC mechanism is influenced by three important parameters: tool vibration frequency, tool vibration amplitude and workpiece cutting speed that determine the cutting force. However, the relation between the cutting force and these three parameters in the UVC is not clearly established. This paper presents firstly the mechanism how these parameters effect the UVC. With theoretical studies, it is established that the tool–workpiece contact ratio (TWCR) plays a key role in the UVC process where the increase in both the tool vibration parameters and the decrease in the cutting speed reduce the TWCR, which in turn reduces both cutting force and tool wear, improves surface quality and prolongs tool life. This paper also experimentally investigates the effect of cutting parameters on cutting performances in the cutting of Inconel 718 by applying both the UVC and the conventional turning (CT) methods. It is observed that the UVC method promises better surface finish and improves tool life in hard cutting at low cutting speed as compared to the CT method. The experiments also show that the TWCR, when investigating the effect of cutting speed, has a significant effect on both the cutting force and the tool wear in the UVC method, which substantiates the theoretical findings.     

基于GASA混合优化策略的切削参数优化设计

优化切削参数是提高生产率，改进工件质量和降低成本的重要手段，本文利用GASA混合优化策略优化切削参数，即保留了传统遗传算法能很快达到最优值领域的优点，又通过结合模拟退火算法大大改善传统遗传算法在后期的收敛性。     

Feasibility study of rotary electrical discharge machining with ball burnishing for Al2O3/6061Al composite

This study investigates the feasibility and optimization of a rotary EDM with ball burnishing for inspecting the machinability of Al₂O₃/6061Al composite using the Taguchi method. Three ZrO₂ balls attached as additional components behind the electrode tool offer immediate burnishing following EDM. Three observed values (machining rate, surface roughness and improvement of surface roughness) are adopted to verify the optimization of the machining technique. In addition, six independent parameters are chosen as variables for evaluating the Taguchi method; these variables are categorized into two groups: (1) electrical parameters, i.e. peak current, pulse duration and non-load voltage; and (2) non-electrical parameters, i.e. flushing pressure of dielectric, rotational speed of electrode and residual height of hump. Experimental results indicated a feasible technique for applying rotary EDM with ball burnishing in machining the Al₂O₃/6061 composite. Optimization of this technique is also discussed.     

Examination of wire electrical discharge machining of Al2O3p/6061Al composites

Alumina particle reinforced 6061 aluminum matrix composites (Al₂O₃p/6061Al) have excellent physical and chemical properties than those of a traditional metal; however, their poor machinability lead to worse surface quality and serious cutting tool wear. In this study, wire electrical discharge machining (WEDM) is adopted in machining Al₂O₃p/6061Al composite. In the experiments, machining parameters of pulse-on time were changed to explore their effects on machining performance, including the cutting speed, the width of slit and surface roughness. Moreover, the wire electrode is easily broken during the machining Al₂O₃p/6061Al composite, so this work comprehensively investigates into the locations of the broken wire and the reason of wire breaking.The experimental results indicate that the cutting speed (material removal rate), the surface roughness and the width of the slit of cutting test material significantly depend on volume fraction of reinforcement (Al₂O₃ particles). Furthermore, bands on the machined surface for cutting 20 vol.% Al₂O₃p/6061Al composite are easily formed, basically due to some embedded reinforcing Al₂O₃ particles on the surface of 6061 aluminum matrix, interrupt the machining process. Test results reveal that in machining Al₂O₃p/6061Al composites a very low wire tension, a high flushing rate and a high wire speed are required to prevent wire breakage; an appropriate servo voltage, a short pulse-on time, and a short pulse-off time, which are normally associated with a high cutting speed, have little effect on the surface roughness.