Optimisation of process parameters for multi-performance characteristics in EDM of Al2O3 ceramic composite

The advantages of electrical discharge machining (EDM) in machining of complex ceramic components have promoted research in the area of EDM of ceramic composites. The recent developments in ceramic composites are focused not only on the improvements of strength and toughness, but also on possibilities for difficult-to-machine shapes using EDM. One such EDM-machinable ceramic composite material (Al₂O₃–SiC_w–TiC) has been developed recently and has been selected in the present study to investigate its EDM machinability. Experiments were conducted using discharge current, pulse-on time, duty cycle and gap voltage as typical process parameters. The grey relational analysis was adopted to obtain grey relational grade for EDM process with multiple characteristics namely material removal rate and surface roughness. Analysis of variance was used to study the significance of process variables on grey relational grade which showed discharge current and duty cycle to be most significant parameters. Other than discharge current and duty cycle, pulse-on time and gap voltage have also been found to be significant. To validate the study, confirmation experiment has been carried out at optimum set of parameters and predicted results have been found to be in good agreement with experimental findings.     

Review of research work in sinking EDM and WEDM on metal matrix composite materials

Metal matrix composites (MMCs) are newly advanced materials having the properties of light weight, high specific strength, good wear resistance and a low thermal expansion coefficient. These materials are extensively used in industry. Greater hardness and reinforcement makes it difficult to machine using traditional techniques, which has impeded the development of MMCs. The use of traditional machinery to machine hard composite materials causes serious tool wear due to the abrasive nature of reinforcement. These materials can be machined by many non-traditional methods like water jet and laser cutting but these processes are limited to linear cutting only. Electrical discharge machining (EDM) shows higher capability for cutting complex shapes with high precision for these materials. The paper presents a review of EDM process and year wise research work done in EDM on MMCs. The paper also discusses the future trend of research work in the same area.     

电火花成形加工技术的研究现状和发展趋势

从电火花加工基础理论、电火花加工工艺理论等方面分析总结了目前国内外电火花加工技术的研究现状,论述了电火花加工技术未来的发展趋势.     

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.     

提高电火花加工效率和表面质量的研究

针对电火花加工中存在的不足,基于多年加工实践经验,给出了提高电火花成形机加工效率和表面质量的措施。研究了电火花成形机加工参数与加工效率和表面质量之间的关系,最后对几种优化组合电加工参数下的加工情况进行了分析研究,所得结论为提高电火花加工质量提供指导。     

提高电火花加工效率和表面质量的研究

针对电火花加工中存在的不足,基于多年加工实践经验,给出了提高电火花成形机加工效率和表面质量的措施。研究了电火花成形机加工参数与加工效率和表面质量之间的关系,最后对几种优化组合电加工参数下的加工情况进行了分析研究,所得结论为提高电火花加工质量提供指导。     

MICRO ELECTRICAL DISCHARGE MACHINING DEPOSITION IN AIR

A new deposition method is described using micro electrical discharge machining (EDM) to deposit tool electrode material on workpiece in air. The basic principles of micro electrical discharge deposition (EDD) are analyzed and the realized conditions are predicted. With an ordinary EDM shaping machine, brass as the electrode, high-speed steel as the workpiece, a lot of experiments are carried out on micro EDD systematically and thoroughly. The effects of major processing parameters, such as the discharge current, discharge duration, pulse interval and working medium, are obtained. As a result, a micro cylinder with 0.19 mm in diameter and 7.35 mm in height is deposited. By exchanging the polarities of the electrode and workpiece the micro cylinder can be removed selectively. So the reversible machining of deposition and removal is achieved, which breaks through the constraint of traditional EDM. Measurements show that the deposited material is compact and close to workpiece base, whose components depend on the tool electrode material.     

Optimization of machining parameters for EDM operations based on central composite design and desirability approach

A novel aluminium metal matrix composite reinforced with SiC particles were prepared by liquid metallurgy route. Recent developments in composites are not only focused on the improvement of mechanical properties, but also on machinability for difficult-to-machine shapes. Electrical discharge machining (EDM) was employed to machine MMC with copper electrode. using EDM. Experiments were conducted using pulse current, gap voltage, pulse on time and pulse off time as typical process parameters. The experiment plan adopts face centered central composite design of response surface methodology. Analysis of variance was applied to investigate the influence of process parameters and their interactions viz., pulse current, gap voltage, pulse on time and pulse off time on material removal rate (MRR), electrode wear ratio (EWR) and surface roughness (SR). The objective was to identify the significant process parameters that affect the output characteristics. Further a mathematical model has been formulated by applying response surface method in order to estimate the machining characteristics such as MRR, EWR and SR.     

Influence of parameters and optimization of EDM performance measures on MDN 300 steel using Taguchi method

Maraging steel (MDN 300) exhibits high levels of strength and hardness. Optimization of performance measures is essential for effective machining. In this paper, Taguchi method, used to determine the influence of process parameters and optimization of electrical discharge machining (EDM) performance measures on MDN 300 steel, has been discussed. The process performance criteria such as material removal rate (MRR), tool wear rate (TWR), relative wear ratio (RWR), and surface roughness (SR) were evaluated. Discharge current, pulse on time, and pulse off time have been considered the main factors affecting EDM performance. The results of the present work reveal that the optimal level of the factors for SR and TWR are same but differs from the optimum levels of the factors for MRR and RWR. Further, discharge current, pulse on time, and pulse off time have been found to play a significant role in EDM operations. Detailed analysis of structural features of machined surface was done by using scanning electron microscope (SEM) to understand the influence of parameters. SEM of electrical discharge machining surface indicates that at higher discharge current and longer pulse on duration give rougher surface with more craters, globules of debris, pockmarks or chimneys, and microcracks than that of lower discharge current and lower pulse on duration.     

一种基于模糊神经网络确定电火花加工条件的新方法

在电火花加工中,影响因素较多,难以确定最优加工条件。应用模糊神经网络确定电火花加工条件是一种新的尝试,它可以充分发挥模糊逻辑和神经网络的长处。为方便操作者决定粗加工最优加工条件,并提高表面加工效果和粗加工速度,本文提出了一种基于模糊神经网络自动确定和优化电火花成形加工中加工参数的方法。经实践证明,用该方法所确定的最优加工条件,能保证较高的粗加工速度,方便了操作者对加工条件的确定。     

节能式电火花加工脉冲电源的系统设计

在对比传统电阻限流独立式电火花加工脉冲电源和节能式脉冲电源电路结构和控制策略的基础上，提出了节能式电火花加工脉冲电源的系统设计方案，并且通过工艺试验，在检验节能式电火花加工脉冲电源加工工艺性能的同时，也考察了其系统设计的方案可行性和加工稳定性。     

The effect of process parameters on machining of magnesium nano alumina composites through EDM

The effects of electrical discharge machining (EDM) parameters on drilled-hole quality such as taper and surface finish are evaluated. Microwave-sintered magnesium nano composites (reinforced with 0.8 and 1.2 wt.% of nano alumina) are used as work materials. Experiments were conducted using Taguchi methodology to ascertain the effects of EDM process parameter. The process parameters such as pulse-on time, pulse-off time, voltage gap, and servo speed were optimized to get better surface finish and reduced taper. ANOVA analyses were carried out to identify the significant factors that affect the hole accuracy and the surface roughness. Confirmation tests were performed on the predicted optimum process parameters. Pulse-on time and the servo speed are identified as major response variables. Micro structural changes and the effects of nano particle reinforcement in the drilled hole were studied through SEM micrographs.     

金属基复合材料加工的进展

介绍了金属基复合材料（ＭＭＣ）的加工发展状态,包括各种传统的切削加工方法和特种加工方法在金属基复合材料上的应用。用刀具切削仍然是ＭＭＣ的主要加工方法,复合材料增强体硬度越高、含量越大,其切削加工性能越差,对刀具硬度的要求也越高。增强体的存在使有色金属基复合材料比基体材料有更好的可磨削性。除电火花成型加工外,各种非传统加工法在ＭＭＣ上的应用多见于板料切割。非传统加工也会在复合材料中留下多种表层缺陷。     

碳纤维增强树脂基复合材料切削机理研究

碳纤维增强树脂基复合材料（Carbon fiber reinforced plastic,CFRP）在细观尺度上由纤维、树脂及界面不同相组成,在宏观尺度上呈层叠特征,具有非均质性和各向异性。CFRP切削过程的实质是在切削力、热共同作用下同时去除高强度纤维和低强度树脂的复杂过程,极易出现加工损伤。抑制加工损伤的前提是准确揭示CFRP切削机理,而揭示其切削机理的关键是分析材料去除过程。由于纤维是复合材料内部承受主要载荷的组成相,材料的去除过程主要由纤维的断裂过程决定。因此,通过分析切削过程中纤维的受力状态,以双参数弹性地基梁理论为基础,建立了虑及纤维所受法向及切向约束,且兼虑树脂及界面温变特性的单纤维切削模型,可准确表征纤维实际受力状态,实现纤维断裂过程的准确求解。研究发现：切削深度和纤维角度影响纤维变形深度,即切深越大,纤维变形深度越大,更易产生加工损伤;随着纤维角度增加,纤维变形深度减小。同时,为解决单纤维切削模型难以直接验证的难题,利用其求解得到宏观切削力理论值,通过与试验值对比,间接验证了单纤维切削模型的正确性。同时与未考虑被切削纤维所受切向约束和树脂及界面温变特性时相比,同时考虑这两个因素可使CFRP宏观切削力计算精度平均提升20%。所建立的单纤维切削模型不仅能够从细观尺度准确揭示CFRP去除机理,而且可为后续有关损伤抑制的研究提供理论依据。     

Monitoring of the electrical discharge machining process by abductive networks

The paper describes the use of abductive networks to monitor the electrical discharge machining (EDM) process. The voltage and current across the gap between the tool and workpiece are fed into the developed networks for the recognition of various pulse types in EDM in a winner-take-all fashion. Experimental results have shown that EDM pulses can be clearly classified even with different machining conditions. Hence, a reliable technique has been developed to monitor the EDM process.     

Optimization of cryogenic cooled EDM process parameters using grey relational analysis

This paper presents an experimental investigation on cryogenic cooling of liquid nitrogen (LN₂) copper electrode in the electrical discharge machining (EDM) process. The optimization of the EDM process parameters, such as the electrode environment (conventional electrode and cryogenically cooled electrode in EDM), discharge current, pulse on time, gap voltage on material removal rate, electrode wear, and surface roughness on machining of AlSiCp metal matrix composite using multiple performance characteristics on grey relational analysis was investigated. The L₁₈ orthogonal array was utilized to examine the process parameters, and the optimal levels of the process parameters were identified through grey relational analysis. Experimental data were analyzed through analysis of variance. Scanning electron microscopy analysis was conducted to study the characteristics of the machined surface.     

混粉准干式电火花加工介质击穿机理研究

混粉准干式电火花加工以气、液、固三相流作为工作介质,能够有效改善气中加工短路率高、加工效率低的问题。以纯净气体介质的击穿理论为基础,对三相流工作介质的击穿机理进行理论分析,阐明固、液分散相的作用机制。建立混粉准干式电火花加工的极间电场强度表达式,给出三相流中加工的放电间隙计算式,从理论上证明分散相的加入使得混粉准干式电火花加工的放电间隙较气中加工大,指出放电间隙增大是加工效率提高的一个重要原因。进行压缩空气中和三相流介质中的放电加工对比试验。测得两种加工介质中的放电间隙值,试验证实三相流工作介质具有放电间隙增大效果。测得放电电压波形,证实气体连续相中固、液分散相的加入能够降低短路率,提高加工稳定性。     

High efficiency fine boring of monocrystalline silicon ingot by electrical discharge machining

This article deals with high efficiency and high accuracy fine boring in a monocrystalline silicon ingot by electrical discharge machining (EDM). In manufacturing process of integrated circuits, a plasma-etching process is used for removing oxidation films. This process has recently been examined for use of monocrystalline silicon as the electrode to minimize the contamination. However, it is difficult to machine silicon accurately by the conventional diamond drilling method, because the material removal is due to brittle fracture. The machining force in the EDM process is very small compared with that in conventional machining, therefore, the possibility of high efficiency and high accuracy boring holes in silicon ingot by EDM is experimentally investigated. The removal rate of monocrystalline silicon by EDM is much higher than that of steel, while the electrode wear is extremely small. The improvement method leads to a better hole without chipping at the exit of hole or sticking of the insulator on the wall of hole. Furthermore, it is proved that even a high aspect ratio of about 200 boring is possible.     

Modeling and analysis of the effects of machining parameters on the performance characteristics in the EDM process of Al2O3+TiC mixed ceramic

Electric discharge machining (EDM) has achieved remarkable success in the manufacture of conductive ceramic materials for the modern metal industry. Mathematical models are proposed for the modeling and analysis of the effects of machining parameters on the performance characteristics in the EDM process of Al₂O₃+TiC mixed ceramic which are developed using the response surface methodology (RSM) to explain the influences of four machining parameters (the discharge current, pulse on time, duty factor and open discharge voltage) on the performance characteristics of the material removal rate (MRR), electrode wear ratio (EWR), and surface roughness (SR). The experiment plan adopts the centered central composite design (CCD). The separable influence of individual machining parameters and the interaction between these parameters are also investigated by using analysis of variance (ANOVA). This study highlights the development of mathematical models for investigating the influences of machining parameters on performance characteristics and the proposed mathematical models in this study have proven to fit and predict values of performance characteristics close to those readings recorded experimentally with a 95% confidence interval. Results show that the main two significant factors on the value of the material removal rate (MRR) are the discharge current and the duty factor. The discharge current and the pulse on time also have statistical significance on both the value of the electrode wear ratio (EWR) and the surface roughness (SR).     

Study of the Batch Production of Micro Parts Using the EDM Process

The micro machining of copper plates by the electrical discharge machining (EDM) process is described. Tungsten carbide was selected as the material for the electrode. Experiments were carried out on a conventional CNC-EDM machine to investigate machining of micro holes, and micro slots. The results show that micro holes, and micro slots can be successfully processed on a conventional CNC-EDM machine. To improve the productivity of micro parts using the EDM process, a batch production method of micro EDM using multi-electrodes has been studied. A new technique for preparing multi-electrodes has been developed. Results also show that the batch production of micro parts using EDM is feasible and that the batch production of micro parts using EDM process with multi-electrodes is very effective.