Electrical Discharge Machining (EDM) Characteristics Associated with Electrical Discharge Energy on Machining of Cemented Tungsten Carbide

In this investigation, cemented tungsten carbides graded K10 and P10 were machined by electrical discharge machining (EDM) using an electrolytic copper electrode. The machining parameters of EDM were varied to explore the effects of electrical discharge energy on the machining characteristics, such as material removal rate (MRR), electrode wear rate (EWR), and surface roughness. Moreover, the effects of the electrical discharge energy on heat-affected layers, surface cracks and machining debris were also determined. The experimental results show that the MRR increased with the density of the electrical discharge energy; the EWR and diameter of the machining debris were also related to the density of the electrical discharge energy. When the amount of electrical discharge energy was set to a high level, serious surface cracks on the machined surface of the cemented tungsten carbides caused by EDM were evident.     

绝缘陶瓷材料电火花加工技术的研究进展

陶瓷材料特性鲜明，有着广阔的应用前景。辅助电极法电火花加工绝缘陶瓷是一种新兴的加工工艺，介绍了陶瓷材料电火花加工技术的基本原理及研究进展。     

电火花加工放电状态的检测及神经模糊控制

设计了电火花加工放电状态的检测方案,确定了模糊控制的输入输出参数,给出了一种实用的神经模糊控制算法,实验结果表明,加工效率有明显提高。     

空气介质微细电火花沉积加工微结构机理

对微细电火花沉积加工中沉积所得不同微细结构的成形机理进行了研究．在电火花成形机床上，通过合理选择工艺参数，用黄铜电极在高速钢工件表面稳定沉积出外径约0．20mm、线径约0．09mm的微螺旋结构和直径约0．20mm微圆柱体．通过有限元法对工具电极放电点的瞬态温度场进行了模拟，分析结果表明，不同的放电能量密度影响材料的蚀除形式，继而影响蚀除电极材料在放电通道中的运动，最终影响微细结构的成形过程．对沉积材料微观组织结构分析表明，沉积材料与基体结合层为冶金结合方式，结合紧密，并由于凝固过程极大的冷却速率，使沉积材料在凝固过程中发生了晶粒细化现象．     

Electrical Discharge Machining of MMCs Reinforced with Very Small Particles

This paper investigates material removal rate (MRR), kerf width, surface finish, and electrode wire wear for different pule-on-times as well as wire tensions during EDM of 6061 aluminum alloy reinforced with 10 vol % 700 nm SiCp MMC. Effects of pulse-on-time on output variables at lower and higher wire tensions were investigated. Similarly, effects of the wire tensions on output variables at shorter and longer pulse-on-times were also investigated. Longer pule-on-time increases the MRR though the higher wire tension reduces the MMR. The effect of wire tension on MRR is much more significant at longer pule-on-time compare to that at shorter pule-on-time. There is an optimum pule-on-time for which best surface finish is achieved. The surface finish deteriorates when the pulse-on-time is higher or lower than the optimum pule-on-time. With the rise of tension in wire, the surface roughness increases and decreases at shorter and longer pule-on-times, respectively. The machined surface contains solidified molten material, splash of materials, and blisters. Generation of the tapered slot with higher kerf width at the top indicates the wear of wire electrode. Significant variation of the electrode wire diameter was due to coating of the matrix, wear, and clogging of small reinforced particles in the electrode gap.     

基于凝胶注模技术制备TiN-Cu电火花电极可行性研究

本文主要探索凝胶注模技术制备TiN-Cu电火花加工用 (EDM) 电极的可行性。本文以TiN粉末和Cu粉末作为原料、海藻酸钠作为分散剂、明胶作为粘结剂, 经过浆料制备、干燥、烧结成EDM电极。研究了pH值、分散剂、粘结剂对浆料流动性的影响和TiN-Cu EDM电极电加工性能。试验结果表明:当pH值为7、海藻酸钠质量分数为1%、明胶质量分数为1%时, 30%TiN-Cu EDM电极相对损耗率为11.625%, 比商用紫铜电极相对损耗率低, 从而得出凝胶注模技术制备TiN-Cu EDM电极是可行的。     

Hole Quality and Damage in Drilling Carbon/Epoxy Composites by Electrical Discharge Machining

This study investigates the material removal mechanisms and machining damage in drilling of carbon fiber epoxy composite by electrical discharge machining (EDM). Detailed investigation of the morphology of the machined surfaces and elemental analysis were conducted inside a scanning electron microscope. Machining damage was characterized by the extent of delamination, hole taper, and the average width of the heat-affected zone (HAZ). The effect of pulse-on time and gap current on machining damage was also investigated. It was found that material removal occurred mainly in the form of decomposition of the polymer matrix and thermally induced fracture of the carbon fibers. Vaporization of the carbon fibers due to spark and Joule heating is also a possible mechanism. The width of HAZ was found to be influenced the most by pulse-on time where the minimum HAZ occurred for intermediate pulse-on time. Furthermore, the width of HAZ and hole taper in EDM were found to be comparable to or less than those obtained by laser cutting.     

基于真空冷冻干燥和高真空微波烧结方法制备TiN-Cu电火花电极

探索真空冷冻干燥和高真空微波烧结方法对TiN-Cu电火花加工用 (EDM) 电极性能的影响。经过高能球磨混合TiN粉末和Cu粉末、浆料制备、干燥、烧结等工艺制备出电火花加工用电极。对比了真空干燥与真空冷冻干燥、真空管式烧结与高真空微波烧结等工艺性能, 采用正交实验方法探索高真空微波烧结最佳工艺参数组合, 并且通过电子扫描电镜观察EDM电极形貌。试验表明:真空冷冻干燥制备坯体收缩率较小;在微波烧结在烧结温度1200℃、保温时间20 min、升温速率15℃/min工艺参数下, 制备出TiN-Cu EDM电极相对损耗率为3.55%, 比商业上应用的紫铜EDM电极相对损耗率低。     

Investigating Feasibility Through Performance Analysis of Green Dielectrics for Sustainable Electric Discharge Machining

This work represents a feasibility study for the newly proposed vegetable oil-based green dielectric fluids, biodielectric1 (BD1) and biodielectric2 (BD2) for electric discharge machining (EDM). Comparative analyses for BD1, BD2, and kerosene have been studied to assess the performance in terms of material removal rate (MRR), electrode wear rate (EWR), and relative wear ratio (RWR) for P20 + cold-worked plastic injection mold steel using electrolytic grade copper electrode. Current, gap voltage, pulse on time (T_on), and pulse off time (T_off) have been chosen as input parameters, and one variable at a time approach has been used for designing experimental plan for investigating the feasibility of the newly suggested fluids. The results obtained show that the performance of the newly suggested biodielectrics BD1 and BD2 is better than commercially used hydrocarbon-based dielectric, i.e., kerosene, for MRR and RWR. Analysis of variance results indicated that current is the most influencing parameter for MRR and EWR, while T_on is the most significant parameter for RWR. Under the influence of current, BD1 and BD2 produced 38% and 165% improvement in MRR, respectively. Moreover, BD1 and BD2 resulted 30% higher and 7% lower RWR, respectively, under the influence of T_on.     

Experimental Investigations of Hot Forging Die Surface Layer of Skd61 Steel in Die Sinking Electrical Discharge Machining

Electrical discharge machining is an important manufacturing process for tool mould and die industries. The results of the research about EDM show that the performance of die sink reduced due to a change in the material quality of the surface layer than the base material. The article presents the result of the study on the hot forging die surface layer of the SKD61 hot die steel （surface roughness, surface microscopic hardness, microscopic structure of the surface layer, EDS analysis of the surface layer） after die sinking electrical discharge machining using a tool of titanium and copper in oil dielectric.     

Study of the Effect of Machining Parameters on the Machining Characteristics in Electrical Discharge Machining of Fe-Mn-Al Alloy

In this work we investigated the electrical discharge machining (EDM) of a Fe-Mn-Al alloy. The surface phenomena caused by EDM were studied in terms of machining parameters. An empirical model of the Fe-Mn-Al alloy was also proposed based on the experimental data. Experimental results indicate that the higher the discharge energy, the faster the machining time. This treatment introduces machining damage in the resolidified surface layer and worsens the surface roughness. The optimum pulse-on duration on the basis of the electrode wear ratio for the copper electrode was about 200 μs. The increase of crater depth with the applied pulsed current and pulse-on duration appears minimal under a small input energy.     

An Experimental Study on Electrical Discharge Machining of Manganese-Zinc Ferrite Magnetic Material

The objective of this research is to investigate the machining characteristics of manganese-zinc (Mn-Zn) ferrite magnetic material using electrical-discharge machining (EDM). The material removal rate, the surface topography, the surface roughness, the recast layer, and the chemical composition of the machined surface were studied in terms of EDM processing variables. Experimental results indicate that the morphology of debris revealed the mechanism of material removal. The surface microgeometry characteristics are not always uniform and homogenous and the EDM process produces much damage on the machined surface. The material removal rate, the surface roughness, and the recast layer are proportional to the applied discharge energy.     

Artificial Neural Network Prediction of Material Removal Rate in Electro Discharge Machining

Thermal erosion theory is widely accepted as an explanation of the erosion process in electro-discharge machining (EDM). Theoretical models are based on the solution of the transient heat conduction equation, which is modeled considering suitable assumptions with appropriate initial and boundary conditions. The closed form solutions result only after considering too many assumptions, which are far from actual machining conditions. The growth of the plasma channel, energy sharing between electrodes, process of vaporization, formation of recast layer, plasma-flushing efficiency, and temperature sensitivity of thermal properties of the work material are a few physical phenomena that render the machining process highly complex and stochastic. The mathematical consideration of all these complex phenomena is very difficult. Therefore, mathematical prediction of material removal rate when compared with the experimental results shows wide variation. In such circumstances, an attempt has been made to develop an artificial feed forward neural network based on the Levenberg-Marquardt back propagation technique of appropriate architecture of the logistic sigmoid activation function to predict the material removal rate. Such a neural network model is expected to perform well under the stochastic environment of actual machining conditions without understanding the complex physical phenomena exhibited in electro-discharge machining. The validity of the neural network model is checked with the experimental data, and we conclude that the artificial neural network model for EDM provides faster and more accurate results.     

数控电火花线切割在板线内导体加工中的应用

分析了板线内导体在利用数控电火花线切割加工中所遇到的工艺技术难题．针对这些问题,作者根据数控快走丝线切割机床的特点,提出了有针对性的解决方案,包括加工参数的选择、加工路径的优化、起割点的合理选择、控制自重变形等方面,最终解决了板线内导体的加工难题．     

Investigation of the Tool Wear Rate in Tungsten Powder-Mixed Electric Discharge Machining of AA6061/10%SiCp Composite

This paper presents the experimental investigation on tool wear rate (TWR) in powder-mixed electrical discharge machining (PMEDM) of aluminum 6061 alloy reinforced with 10% silicon carbide particles (AA6061/10%SiC_p composite). Composite material is fabricated by mechanical stir casting process and further characterized by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). Tungsten powder with concentration of 4 g/L is mixed in the dielectric fluid. To know the influence of powder suspension in dielectric fluid on TWR, comparative study is done on the basis of experiments performed using basic EDM and PMEDM process. Experiments have been designed as per central composite rotatable design (CCRD) using response surface methodology (RSM) approach. Four process parameters, namely, peak current, pulse-on time, pulse-off time, and gap voltage have been considered for TWR investigation. Individual and interactive influence of various parameters on TWR is explained with the help of analysis of variance and three-dimensional graphs. Using RSM approach, results have been further optimized. PMEDM approach provides 51.12% reduction in TWR for machining of AA6061/10%SiC_p composite.     

Electrical Discharge Machining of Ti6Al4V in Hydroxyapatite Powder Mixed Dielectric Liquid

Hydroxyapatite (HA) powder suspension in deionized water was used as a dielectric liquid during electrical discharge machining (EDM) of Ti6Al4V work material. The machined surfaces were evaluated by scanning electron microscopy (SEM), energy dispersive spectroscopy, and optical microscopy. The powder particles in the dielectric liquid extensively migrated and formed an HA-rich layer on the work material surface under specific machining conditions. The result was attributed to the generation of secondary discharges due to altered discharge conditions. The particles divided the primary discharge channel into several secondary ones. When the main discharge channel subdivided into several sub-discharges with comparable energy densities, the particles in the discharge region got stuck among them. Then, they moved toward the melted cavities and penetrated the surface at the end of the discharge duration. The results suggest the process as a practical alternative for producing biocompatible interfaces or coatings for medical applications.     

空气源热泵热水器冬季性能实验研究

空气源热泵热水器是一种新型的热水器，具有安全、节能、环保等特点，但是它也存在着许多缺点：受环境温度影响较大，尤其是在冬季环境温度很低的北方，系统效率不是很高，表现不够稳定，针对这些情况，本文对其冬季性能作了研究，分别在环境温度为0℃、-5℃、-20℃，三种工况下做了开机时间与水温的变化、开机时间与系统COP的变化，和融霜等实验，通过实验找到了影响空气源热泵热水器冬季性能的因素，为其系统优化和空气侧换热器的除霜提供了依据。     

基于混合智能的电火花加工电参数学习模型的研究

提出了一个基于混合智能的电火花加工电参数学习模型,它模仿熟练操作者的决策过程,由于工艺数据库、加工规则库、学习模块和推理模块组成。在学习模块中利用遗传算法从工艺数据库中抽取出反映电参数和加工结果之间关系的模糊产生式规则,存储在规则库中。推理模块基于这些规则利用模糊拄是对新加的要求提供合适的电参数。     

Multi-Gate Systems in Casting Process: Comparative Study of Liquid Metal and Water Flow

Most industrial castings are manufactured by allowing liquid metal to fill the mold cavity through multiple gates. The goal is to ensure smooth, complete, and uniform filling, thereby minimizing related defects such as cold shuts and inclusions. Very few researchers have, however, investigated flow parameters in such systems. In this work, novel experimental setups were developed to study the flow of liquid metal (Al-Si12 as well as Zn) and water through a gating system comprising a vertical sprue at one end connected to four gates through a horizontal runner. The flow sequence, velocity, and discharge through the four gates were observed by video recording and various measurements. It was found that while the first gate (closest to sprue) filled first, the last gate exhibited the maximum volume of discharge. The proportion of flow through the four gates was found to be nearly the same for all three fluids. The results establish the usefulness of water models to investigate mold filling in metal casting. The study provides valuable insight that can help in balancing the flow through multiple gates in industrial castings, as well as benchmarks to verify simulation codes.