基于改进BP网络的电火花加工工艺选择模型

提出了基于对数变换的数据预处理改进算法,测试表明效果较好。以加工面积、电极损耗比、表面粗糙度为输入参数,脉冲电流、脉冲宽度、脉冲间隙、放电间隙、伺服基准、伺服速度、加工速度为输出参数,提出了基于改进BP神经网络的电火花加工工艺选择模型。经过与实验数据的比较,该模型能真实反映机床的加工工艺规律,能实现在给定加工条件下进行电加工参数的自动选择。     

深冷处理D2工具钢线切割加工数值分析

以深冷处理D2工具钢为研究对象,建立其在线切割加工过程中的能量比、单位时间去除材料体积、工件加工表面粗糙度数值计算模型,运用MATLAB软件进行分析,并用试验验证。仿真分析及试验验证的结果表明:随着加工电流和脉冲宽度的增加,能量比不断增加;随着加工电流的增加,单位时间去除材料体积逐渐增加,而随着脉冲宽度的增加,单位时间去除材料体积呈现逐渐减小的趋势;随着加工电流和脉冲宽度的增加,工件加工表面粗糙度呈现先减小后增加趋势;单位时间去除材料体积、工件加工表面粗糙度的仿真计算值与试验测量值最大相对误差分别为4.76%、4.75%,相对误差较小,验证数值分析的正确性,为工具钢线切割加工最佳工艺参数选择及工艺优化提供理论依据。     

基于Pareto前沿的单晶Si放电加工工艺参数优化

针对电火花加工复杂、时变、多参数的特点,在单晶硅Si放电成型加工可行性的基础上,对材料去除率和表面粗糙度等工艺目标进行综合评价。采用中心组合设计实验综合考察峰值电流、脉冲宽度、脉冲间隔对P型单晶Si放电成型加工过程中材料去除率以及表面粗糙度的影响程度,通过响应曲面法分别获得材料去除率和表面粗糙度的二次响应模型,方差分析结果表明模型具有很好的拟合程度和适应性。以提高材料去除率和降低表面粗糙度为目标建立工艺参数优化模型,设计遗传算法对优化问题进行求解并得到Pareto最优解集。实验结果表明,料去除率的实验结果与优化预测结果平均相对误差为5.8%,表面粗糙度的实验结果与优化预测结果平均相对误差为5.3%。表明该算法能有效快速的实现P型单晶Si放电成型加工过程的工艺参数优化。     

TA7电火花加工实验研究与工艺参数优化

针对TA7钛合金难切削以及加工表面质量差的问题,在通用电火花机床上探究了空载电压、峰值电流、脉冲宽度以及脉冲间隔对TA7钛合金电火花加工中材料去除率与表面粗糙度的影响。设计中心复合实验,在实验数据的基础上采用多线回归技术建立材料去除率和表面粗糙度的二阶预测模型。方差分析结果表明预测模型可以正确映射出TA7钛合金电火花加工的工艺规律。以提高材料去除率降低表面粗糙度为目的建立工艺目标优化模型,根据实际加工条件对工艺参数的约束,设计粒子群算法求取优化模型的解集,通过实际加工对优化结果进行验证,结果表明该算法可以正确可靠的获得多约束条件下的最优加工参数。     

高频群脉冲电化学加工中碳含量和组织对加工效果的影响

通过实验研究了在高频群脉冲电化学加工中，4种不同碳含量的碳钢在不同热处理状态下，其电化学加工的表面粗糙度、蚀除率、电流效率与加工工艺参数（如极间电压、脉冲频率、进给速度等）间的关系。实验表明：随碳含量、脉冲频率（尤其是主频率）升高，粗糙度明显降低；而随加工电压、进给速度的增加，粗糙度则增加。碳含量对加工电流效率和蚀除率有明显影响，它们之间呈正比例的关系；而极间电压、脉冲频率和进给速度对电流效率和蚀除率没有明显影响。实验还表明：显微组织明显影响加工质量，淬火和调质的加工质量高于退火态。另外还通过电化学加工多参数正交试验，考查了40Cr调质钢件不同工艺参数组合下的加工效果，进而找出优化的电化学工艺参数为：电压5V，进给速度3000μm／min，电源主脉冲频率20kHz，调制频率100Hz，加工粗糙度可达Ra=0．29μm。     

电火花线切割Cr12MoV模具钢工艺规律的试验研究

电火花线切割技术在冲压模具的加工中具有重要作用。在中走丝电火花线切割机床上,以脉宽时间、脉间时间、加工电流以及运丝速度等工艺参数为变量进行切割Cr12MoV模具钢的单因素试验研究。结果表明,各工艺参数中,运丝速度对切割速度的影响程度最大,而相比于对切割速度的影响,各工艺参数对表面粗糙度的影响稍小。此外,当脉宽时间为20μs、脉间时间为40μs、加工电流为7档以及运丝速度为3档时,可以达到最大的切割速度99.01mm~2/min和较小的表面粗糙度值2.904μm。     

基于正交试验的电火花加工工艺效果试验分析

通过正交试验分析,探讨电火花成形加工中影响加工效果的主要因素,阐述了脉冲峰值电流、脉冲宽度及脉冲间 隔等对加工速度、加工表面粗糙度及工具电极损耗的影响关系,对解决电火花加工实践中工艺参数优化问题具有一定的 理论和实践意义。     

电火花加工中测量加工参数对表面粗糙度影响的实验研究

电火花加工是一种非传统加工方法,近些年在世界各地被广泛用于模具生产。电火花加工中最重要的参数是表面粗糙度,其他参数还有材料去除率和刀具的磨损率等。研究通过实验完整地测定影响表面粗糙度的参数,以及使用实验方法的设计分析获得的有关参数,建立了一个以功率、脉冲时间和放电时间为参数的表面粗糙度方程,并对其作了讨论。     

灰色理论在慢走丝线切割加工中的应用

慢走丝电火花线切割中工艺指标与工艺参数之间具有高度非线性关系,难以实现电火花多工艺参数优化,针对此问题,以电火花线切割SKD11模具钢为试验对象,选用水压、脉冲宽度、脉冲间隔、峰值电流和进给速度为可变因素,表面粗糙度(Ra)和材料去除率(MRR)为工艺指标,设计田口试验,采用灰色关联分析方法研究加工参数对工艺指标的影响关系;建立改进的灰色神经网络模型对Ra和MRR预测,其平均相对误差分别为7.92%和8.13%。结果表明,该模型能反映出电火花线切割SKD11模具钢的工艺规律并能成功预测出Ra和MRR,为电火花线切割SKD11模具钢工艺参数的选择提供了依据。寻找的一组优化参数对SKD11模具钢的线切割加工具有一定的参考意义。     

电极超声复合混粉电火花加工TC4试验研究

为了提高电火花加工TC4合金的加工效率、表面质量,在混粉电火花加工的基础上设计了一套工具电极超声振动装置。以工件去除率MRR和表面粗糙度Ra为工艺指标设计了Box-Behnken试验,应用响应面法建立了加工参数与工艺指标之间的二次回归模型,分析了加工参数对工艺指标的影响;通过对比试验,得出电极超声振动使混粉电火花加工去除率平均值提高了29%;粗糙度Ra值降低22%。对去除率及表面粗糙度进行了多指标优化,参数最优组合为:电极直径为4mm,峰值为20A,脉冲间隔为39μs,铝粉浓度为15.3(g·L~(-1))。试验表明:在大脉冲环境下,电极超声混粉电火加工花仍能获得较好的表面质量。     

Fabricating micromilling tool using wire electrodischarge grinding and focused ion beam sputtering

In the present research, wire electrical discharge machining (WEDM) of γ titanium aluminide is studied. Selection of optimum machining parameter combinations for obtaining higher cutting efficiency and accuracy is a challenging task in WEDM due to the presence of a large number of process variables and complicated stochastic process mechanisms. In general, no perfect combination exists that can simultaneously result in both the best cutting speed and the best surface finish quality. This paper presents an attempt to develop an appropriate machining strategy for a maximum process criteria yield. A feed-forward back-propagation neural network is developed to model the machining process. The three most important parameters – cutting speed, surface roughness and wire offset – have been considered as measures of the process performance. The model is capable of predicting the response parameters as a function of six different control parameters, i.e. pulse on time, pulse off time, peak current, wire tension, dielectric flow rate and servo reference voltage. Experimental results demonstrate that the machining model is suitable and the optimisation strategy satisfies practical requirements.     

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.     

Investigation into electrochemical micromachining (EMM) through response surface methodology based approach

Electrochemical micromachining (EMM) could be used as one the best micromachining technique for machining electrically conducting, tough and difficult to machine material with appropriate machining parameters combination. This paper attempts to establish a comprehensive mathematical model for correlating the interactive and higher-order influences of various machining parameters, i.e. machining voltage pulse on/off ratio, machining voltage, electrolyte concentration, voltage frequency and tool vibration frequency on the predominant micromachining criteria, i.e. the material removal rate and the radial overcut through response surface methodology (RSM), utilizing relevant experimental data as obtained through experimentation. Validity and correctiveness of the developed mathematical models have also been tested through analysis of variance. Optimal combination of these predominant micromachining process parameters is obtained from these mathematical models for higher machining rate with acuuracy. Considering MRR and ROC simultaneously optimum values of predominant process parameters have been obtained as; pulse on/off ratio, 1.0, machining voltage, 3 V, electrolyte concentration, 15 g/l, voltage frequency of 42.118 Hz and tool vibration frequency as 300 Hz. The effects of various process parameters on the machining rate and radial overcut are also highlighted through different response surface graphs. Condition of machined micro-holes are also exhibited through the SEM micrographs in this paper. Pulse voltage pattern during electrochemical micromachining process has been analyzed with the help of voltage graphs. Irregularities in the nature of pulse voltage pattern during electrochemical micromachining have been observed and the causes of these irregularities are further investigated.     

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.     

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.     

Optimization of machining parameters in rotary EDM process by using the Taguchi method

Electrical discharge machining (EDM) is one of the advanced methods of machining. Most publications on the EDM process are directed towards non-rotational tools. But rotation of the tool provides a good flushing in the machining zone. In this study, the optimal setting of the process parameters on rotary EDM was determined. A total of three variables of peak current, pulse on time, and rotational speed of the tool with three types of electrode were considered as machining parameters. Then some experiments have been performed by using Taguchi's method to evaluate the effects of input parameters on material removal rate, electrode wear rate, surface roughness, and overcut. Moreover, the optimal setting of the parameters was determined through experiments planned, conducted, and analyzed using the Taguchi method. Results indicate that the model has an acceptable performance to optimize the rotary EDM process.     

INVESTIGATING THE EFFECTS OF EDM PARAMETERS ON SURFACE INTEGRITY,MRR AND TWR IN MACHINING OF Ti–6Al–4V

Ti–6Al–4V is a kind of difficult-to-cut material with poor machinability by traditional machining methods, while electrical discharge machining (EDM) is suitable for machining titanium alloys. In this paper, three input machining parameters including pulse current, pulse on time and open circuit voltage were changed during EDM tests. To investigate the output characteristics; material removal rate (MRR), tool wear ratio (TWR) and different aspects of surface integrity for Ti–6Al–4V samples such as topography of machined surface, crack formation, white layer (recast layer) thickness and microhardness were considered as performance criteria. The variations of MRR and TWR versus input machining parameters were investigated by means of main and interaction effect plots and also verified by ANOVA results. The effect of pulse energy based on pulse on time and pulse current variations against recast layer thickness and microhardness was studied. The possibility of forming different chemical elements and compounds on the work surface after EDM process was investigated by EDS and XRD analyses. The experimental results revealed that general aspects of surface integrity for machined samples are mostly affected by pulse current and pulse on time. The approximate density of cracks, micro holes and pits on the work surface is intensively dependent on pulse energy variations. Although increase of pulse energy improves the material removal efficiency but leads to increase of average thickness and microhardness of recast layer.     

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.     

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。