An experimental investigation on machining parameters of AISI D2 steel using WEDM

The performance of the wire electrodischarge machining (WEDM) machining process largely depends upon the selection of the appropriate machining variables. Optimization is one of the techniques used in manufacturing sectors to arrive for the best manufacturing conditions, which are essential for industries toward manufacturing of quality products at lowest cost. As there are many process variables involved in the WEDM machining process, it is difficult to choose a proper combination of these process variables in order to maximize material removal rate and to minimize tool wear and surface roughness. The objective of the this work is to investigate the effects of process variables like pulse on time, pulse off time, peak current, servo voltage, and wire feed on material removal rate (MRR), surface roughness (SR), gap voltage, gap current, and cutting rate in the WEDM machining process. The experiment has been done using Taguchi’s orthogonal array L27 (3⁵). Each experiment was conducted under different conditions of input parameters and statistically evaluated the experimental data by analysis of variance (ANOVA) using MINITAB and Design Expert tools. The present work also aims to develop mathematical models for correlating the inter-relationships of various WEDM machining parameters and performance parameters of machining on AISI D2 steel material using response surface methodology (RSM).The significant machining parameters and the optimal combination levels of machining parameters associated with performance parameters were also drawn. The observed optimal process parameter settings based on composite desirability (61.4 %) are pulse on time 112.66 μs, pulse off time 45 μs, spark gap voltage 46.95 V, wire feed 2 mm/min, peak current of 99.99 A for achieving maximum MRR, gap current, gap voltage, cutting rate, and minimum SR; finally, the results were experimentally verified.     

Optimization of wire electrical discharge machining (WEDM) process parameters using Taguchi method

Wire electrical discharge machining (WEDM) is extensively used in machining of conductive materials when precision is of prime importance. Rough cutting operation in WEDM is treated as a challenging one because improvement of more than one machining performance measures viz. metal removal rate (MRR), surface finish (SF) and cutting width (kerf) are sought to obtain a precision work. Using Taguchi’s parameter design, significant machining parameters affecting the performance measures are identified as discharge current, pulse duration, pulse frequency, wire speed, wire tension, and dielectric flow. It has been observed that a combination of factors for optimization of each performance measure is different. In this study, the relationship between control factors and responses like MRR, SF and kerf are established by means of nonlinear regression analysis, resulting in a valid mathematical model. Finally, genetic algorithm, a popular evolutionary approach, is employed to optimize the wire electrical discharge machining process with multiple objectives. The study demonstrates that the WEDM process parameters can be adjusted to achieve better metal removal rate, surface finish and cutting width simultaneously.     

The effect of the cutting parameters on performance of WEDM

In this study, variations of cutting performance with pulse time, open circuit voltage, wire speed and dielectric fluid pressure were experimentally investigated in Wire Electrical Discharge Machining (WEDM) process. Brass wire with 0.25 mm diameter and AISI 4140 steel with 10 mm thickness were used as tool and work materials in the experiments. The cutting performance outputs considered in this study were surface roughness and cutting speed. It is found experimentally that increasing pulse time, open circuit voltage, wire speed and dielectric fluid pressure increase the surface roughness and cutting speed. The variation of cutting speed and surface roughness with cutting parameters is modeled by using a regression analysis method. Then, for WEDM with multi-cutting performance outputs, an optimization work is performed using this mathematical models. In addition, the importance of the cutting parameters on the cutting performance outputs is determined by using the variance analysis (ANOVA).     

复合运丝型电火花线切割加工参数分析与研究

提出了一种新型电火花线切割机床,即电极丝作往复直线运动的同时还绕自身轴线高速旋转的复合运丝型线切割机床。介绍了该类机床与其他线切割机床加工的基本工艺指标。通过与高速走丝电火花线切割机床比较实验,分析了脉冲宽度、脉冲间隔、脉冲峰值电流等电参数对加工工艺指标的影响,实验表明这种独特的复合运丝方式在降低表面粗糙度、提高加工精度等方面较传统运丝方式具有较大的优越性,且机床结构较为简单,对于各种工艺参数和电参数具有更加广泛的适用性,具有进一步研究和推广价值。     

On wire breakage and microstructure in WEDC of SiCp/6061 aluminum metal matrix composites

Unconventional machining like wire electric discharge machining/cutting (WEDM/WEDC) seems to be a better choice for machining/cutting the metal matrix composites (MMCs) because it offers easy control and has the capability of machining intricate complex shapes. But wire breakage in the WEDM/WEDC process decreases the machining accuracy and the quality of the machined surface. This paper describes the effect of four input process parameters (i.e., servo voltage, pulse-on time, pulse-off time, and wire feed rate) on wire breakage frequency and the microstructure of the cut surface during WEDC of SiC_p/6061 Al MMC. An optimum range of input parameters has been bracketed as the outcome of this work for determining the effects of input process parameters on the average cutting speed, material removal rate, and surface roughness during WEDC of SiC_p/6061 Al MMC. This range of input parameters can also be used for carrying out further research to develop the models for WEDC of SiC_p/6061 Al MMC and to optimize the WEDC parameters for smooth cutting.     

Application of Taguchi,ANFIS and grey relational analysis for studying,modeling and optimization of wire EDM process while using gaseous media

In the dry wire electrical discharge machining (WEDM) process, the liquid dielectric is replaced with gaseous medium to enhance the machining environment safety. Also, this modification improves the surface quality of machined specimen but decreases the material removal rate of the process. In the present work, experimental study of dry WEDM process has been performed while machining of Al/SiC metal matrix composite. At first, a series of exploratory experiments has been conducted to identify appropriate gas and wire material based on their cutting velocity. After selection of the best gas and best wire, they were used for later stage of experiments. At the next stage, experiment were designed and conducted based on L₂₇ Taguchi's orthogonal array to study the effect of pulse on time, pulse off time, gap voltage, discharge current, wire tension and wire feed on cutting velocity (CV) and surface roughness (SR). Analysis of variances (ANOVA) has been performed to identify significant factors. In order to correlate relationship between process inputs and responses, adaptive neuro-fuzzy inference system has been utilized. At the end, a grey relational analysis has been used to maximize CV and minimize SR simultaneously. Results indicated that oxygen gas and brass wire guarantee superior cutting velocity. Also according to ANOVA, pulse on time and current were found to have significant effect on CV and SR.     

Multi response optimization of wire EDM operations using robust design of experiments

In this present study a multi response optimization method using Taguchi’s robust design approach is proposed for wire electrical discharge machining (WEDM) operations. Experimentation was planned as per Taguchi’s L16 orthogonal array. Each experiment has been performed under different cutting conditions of pulse on time, wire tension, delay time, wire feed speed, and ignition current intensity. Three responses namely material removal rate, surface roughness, and wire wear ratio have been considered for each experiment. The machining parameters are optimized with the multi response characteristics of the material removal rate, surface roughness, and wire wear ratio. Multi response S/N (MRSN) ratio was applied to measure the performance characteristics deviating from the actual value. Analysis of variance (ANOVA) is employed to identify the level of importance of the machining parameters on the multiple performance characteristics considered. Finally experimental confirmation was carried out to identify the effectiveness of this proposed method. A good improvement was obtained.     

Optimization of WEDM process of pure titanium with multiple performance characteristics using Taguchi’s DOE approach and utility concept

This paper describes the development of multi response optimization technique using utility method to predict and select the optimal setting of machining parameters in wire electro-discharge machining (WEDM) process. The experimental studies in WEDM process were conducted under varying experimental conditions of process parameters, such as pulse on time(T_on), pulse off time(T_off), peak current (IP), wire feed (WF), wire tension (WT) and servo voltage (SV) using pure titanium as work material. Experiments were planned using Taguchi’s L27 orthogonal array. Multi response optimization was performed for both cutting speed (CS) and surface roughness (SR) using utility concept to find out the optimal process parameter setting. The level of significance of the machining parameters for their effect on the CS and SR was determined by using analysis of variance (ANOVA). Finally, confirmation experiment was performed to validate the effectiveness of the proposed optimal condition.     

Comparative study of conventional and micro WEDM based on machining of meso/micro Sized Spur Gear

This paper discusses the comparison of micro machining process using conventional and micro wire electrical discharge machining (WEDM) for fabrication of miniaturized components. Seventeen toothed miniaturized spur gear of 3.5 and 1.2 mm outside diameter were fabricated by conventional and micro WEDM respectively. The process parameters for both conventional and micro WEDM were optimized by preliminary experiments and analysis. The gears were investigated for the quality of surface finish and dimensional accuracy which were used as the criteria for the process evaluation. An average surface roughness (R_a) of 50 nm and dimensional accuracy of 0.1–1 μm were achieved in micro WEDM. Whenever applied conventional WEDM for meso/micro fabrication, a R_a surface roughness of 1.8 μm and dimensional accuracy of 2–3 μm were achieved. However, this level of surface roughness and dimensional accuracy are acceptable in many applications of micro engineering. A window of conventional WEDM consisting of low energy discharge parameters is identified for micromachining.     

电火花线切割加工中线电极的动态特性仿真与实验研究

研究慢走丝电火花线切割加工中电极振动对加工状态的过程的影响。应用计算机仿真技术,分析连续放电力作用下线的振动模态以及对放电点转移和分布的作用。结果表明,加工工艺参数明显影响放电点的转移与分布,适当地选择工艺参数可获得最佳的放电分布率。该研究对提高慢走丝加工稳定性,防止断丝的发生提供了相应理论依据。     

快走丝电火花线切割加工仿真系统

通过神经网络技术建立了快走丝电火花线切割加工工艺模型 ,利用穷举法建立了具有一定人工智能的工艺参数全局优化系统 ,开发了模具电火花加工过程仿真系统。该系统不仅可以精确预测加工效果 ,而且克服了工艺参数表的局限性 ,弥补了建立在工艺参数表基础上的参数自动选取系统的缺陷 ,实现了工艺参数全局最优化。测试结果及实际使用结果表明本文所建立的仿真系统反映了机床的加工工艺特性 ,预测误差基本控制在 8%内 ,系统的参数优化选取功能使机床的加工性能得以充分发挥。仿真系统具有广泛的通用性 ,可适用于不同类型的线切割加工机床。     

Determining cutting parameters in wire EDM based on workpiece surface temperature distribution

The material removal process in wire electrical discharge machining (WEDM) may result in work-piece surface damage due to the material thermal properties and the cutting parameters such as varying on-time pulses, open circuit voltage, machine cutting speed, and dielectric fluid pressure. A finite element method (FEM) program was developed to model temperature distribution in the workpiece under the conditions of different cutting parameters. The thermal parameters of low carbon steel (AISI4340) were selected to conduct this simulation. The thickness of the temperature affected layers for different cutting parameters was computed based on a critical temperature value. Through minimizing the thickness of the temperature affected layers and satisfying a certain cutting speed, a set of the cutting process parameters were determined for workpiece manufacture. On the other hand, the experimental investigation of the effects of cutting parameters on the thickness of the AISI4340 workpiece surface layers in WEDM was used to validate the simulation results. This study is helpful for developing advanced control strategies to enhance the complex contouring capabilities and machining rate while avoiding harmful surface damage.     

探讨高速走丝电火花线切割加工断丝故障分析及预防

高速走丝电火花线切割加工能够满足我国模具制造以及机械加工的需要,但是在高速走丝电火花线切割加工的过程中容易出现断丝的情况,这对于快速的机械加工以及模具制造而言有着非常大的影响。详述高速走丝电火花线切割加工的原理、高速走丝电火花线切割加工断丝的故障原因以及高速走丝电火花切割加工中断丝故障的解决方法及预防。对于高速走丝电火花线切割加工中断丝的情况要进行分析并预防。     

An investigation on machinability of nodular cast iron by WEDM

In this study, the machinability of standard GGG40 nodular cast iron by WEDM using different parameters (machining voltage, current, wire speed, and pulse duration) was investigated. From the results, the increase in surface roughness and cutting rate clearly follows the trend indicated with increasing discharge energy as a result of an increase of current and pulse-on time, because the increased discharge energy will produce larger and deeper discharge craters. Three zones were identified in rough regimes of machining for all samples: decarburized layer, heat affected layer, and bulk metal. High machining efficiency can be obtained when the proper electrical parameters are selected, but whether high energy or the low energy is used, a coarse surface is always obtained. The variation of surface roughness and cutting rate with machining parameters is mathematically modeled by using the regression analysis method.     

Modeling and analysis of white layer depth in a wire-cut EDM process through response surface methodology

A white layer is considered a major flaw on a workpiece surface machined with wire-cut electrical discharge machining (WEDM). In this paper, an attempt has been made to model the white layer depth through response surface methodology (RSM) in a WEDM process comprising a rough cut followed by a trim cut. An experimental plan for rotatable central composite design of second order involving four variables with five levels has been employed to carry out the experimental investigation and subsequently to establish the mathematical model correlating the input process parameters with the response. Pulse on time during rough cutting, pulse on time, wire tool offset, and constant cutting speed during trim cutting are considered the dominant input process parameters whilst the white layer depth is the response. An insignificant lack of fit term indicated a curve with a good fit. Also, an extensive analysis of the influences of all the individual input parameters on the response has been carried out and presented in this research study.     

Investigating the effect of WEDM process parameters on 3D micron-scale surface topography related to fractal dimension

The wire electric discharge machining (WEDM) process is a violent thermal process in which a certain volume of metal is eroded by thousands of electrical discharges in a fraction of 1 s. The process is widely used in tooling, especially in the cutlery and mold industry. However, the poor properties of surfaces such as high tensile residual stresses, high surface roughness, white layers, and microcracks are generated in the process. These properties vary with different levels of process parameters. In this paper, a new graphical evaluation of micron-scale surface topography on WEDM process is proposed by the fractal method. The objective is to quantify 3D micron-scale surface topography effect of process parameters such as pulse-on time, pulse-off time, cutting feed rate, wire tension, wire speed, and water pressure on working surface in dressing. Firstly, adaptive measuring was conducted on the basis of 3D micron-scale surface topography by the ?₁₈(2¹×3⁵) Taguchi standard orthogonal experiments; secondly, the fractal dimension was conducted to identify 3D micron-scale surface topography; and finally, the effect of WEDM process parameters was investigated with reference to the fractal dimension (FD) of 3D micron-scale surface. The results have shown that the pulse-on time is the most dominant factor in affecting the surface texture. Moreover, the interaction effect between process parameters is analyzed. It has also been observed that the optimized combination of pulse-on time of 3 μs, pulse-off time of 20 μs, cutting feed rate of 4 mm/min, wire tension of 6 kgf, wire speed of 6 m/min, and water pressure of 5 kgf is suitable for 3D micron-scale surface, and the FD of 3D micron-scale surface is increased by 11 %.     

An investigation on machinability of nodular cast iron by WEDM

In this study, the machinability of standard GGG40 nodular cast iron by WEDM using different parameters (machining voltage, current, wire speed, and pulse duration) was investigated. From the results, the increase in surface roughness and cutting rate clearly follows the trend indicated with increasing discharge energy as a result of an increase of current and pulseon time, because the increased discharge energy will produce larger and deeper discharge craters. Three zones were identified in rough regimes of machining for all samples: decarburized layer, heat affected layer, and bulk metal. High machining efficiency can be obtained when the proper electrical parameters are selected, but whether high energy or the low energy is used, a coarse surface is always obtained. The variation of surface roughness and cutting rate with machining parameters is mathe-matically modeled by using the regression analysis method.     

数控快走丝电火花线切割加工工艺方法研究

通过对数控快走丝电火花线切割加工中如何加工穿丝孔、装夹工件、编制程序、选择电参数、使用工作液、应用多次切割工艺方法以及诊断加工故障等工艺方法进行研究。形成了一套完整的工艺方法，效果良好。     

Multi-response optimization of process parameters based on response surface methodology for pure titanium using WEDM process

This paper presents an investigation on WEDM of pure titanium (grade-2). An attempt has been made to model the four response variables, i.e., machining rate, surface roughness, dimensional deviation and wire wear ratio in WEDM process using response surface methodology. The experimental plan is based on Box–Behnken design. The six parameters, i.e., pulse on time, pulse off time, peak current, spark gap voltage, wire feed and wire tension have been varied to investigate their effect on output responses. These responses have been optimized using multiresponse optimization through desirability. The ANOVA has been applied to identify the significance of developed model. The test results confirm the validity and adequacy of the developed RSM model. Finally, the optimum parametric setting has been designed for the optimization of process.     

Surface crack density and recast layer thickness analysis in WEDM process through response surface methodology

In this work, quantitative assessment of surface damage in terms of parameters like surface crack density and recast layer thickness in wire electrical discharge machining (WEDM) process has been undertaken. The effect of processing conditions on crack formation is studied using scanning electron microscope. Surface crack density and recast layer thickness analysis in terms of machining parameters such as pulse on time, pulse off time, peak current, spark gap voltage significantly deteriorate the microstructure of machined samples, which produces the deeper, wider overlapping craters, pock marks, globules of debris and micro cracks. The microstructure analysis of WEDM surface was based upon the theory of electrical discharge phase and metallurgical physics. It is found that the pulse on time, pulse off time and peak current are the most dominating parameters for both surface crack density and recast layer thickness.