Study of specific discharge energy in WEDM and its application

The relationship between machining parameters and machining characteristics of different materials in WEDM is difficult to obtain because a large number of experiments must be conducted repeatedly. A new concept attempting to solve this problem is presented in this paper. The specific discharge energy (SDE) defining as the real energy required to remove a unit volume of material is proposed. The SDE is constant for a specific material. Experimental results reveal that the relative relationship of SDE between different materials is invariant as long as all materials are machined under the same machining conditions. It is also found that the materials having close value of SDE demonstrate very similar machining characteristics such as machining speed, discharge frequency, groove width and surface finish of the machined surface under the same machining conditions. This result can be applied for the determination of the settings of machining parameters of different materials. Furthermore, by dimensional analysis of SDE, a quantitative relationship between machining characteristics such as the material removal rate and the efficiency of material removal and machining parameters is derived.     

Advancing EDM through Fundamental Insight into the Process

This paper aims to show the prospects of electrical discharge machining (EDM) technology by interrelating recent achievements in fundamental studies on EDM with newly developed advanced application technologies. Although gap phenomena in EDM are very complicated and hence not yet very well understood, recent improvements in computers and electronic measuring instruments are contributing to new discoveries and inventions in EDM technology. Such newly acquired insight sometimes raises questions on the validity of the established theories of EDM phenomena, and EDM processes once believed to be impossible or unrealistic are now becoming practical.     

液包丝供给方式的电火花线切割实验研究

在大气介质中对Cr12MoV模具钢进行电火花线切割精加工,较工作液介质中加工可获得更高的加工表面质量,但也存在表面碳化、电极丝热疲劳损伤等问题.为解决上述问题,采用液包丝(双介质)供给代替传统供给方式进行电火花线切割精加工.结果表明:在液包丝(双介质)中加工的表面质量比大气介质中的略高,且电极丝损耗明显降低.研究结果可...     

PCD刀具电火花线切割磨削机床的研制

研制了用于加工聚晶金刚石(PCD)刀具的电火花线切割磨削机床,完成了机床总体方案、各运动进给轴及单向走丝系统的机械结构设计。机床具有较高的位置精度和表面粗糙度,可广泛应用于各种复杂形状的PCD刀具制作,具有以割代磨的技术特点。     

放电参数对线切割加工A8工具钢表面粗糙度与材料去除率的影响

A8工具钢是一种高硬度高韧性的难加工材料,常用电火花线切割来加工处理。电火花线切割加工A8工具钢实际生产过程中,表面粗糙度和材料去除率分别是加工表面质量和加工效率的重要指标,放电参数直接影响到表面粗糙度和材料去除率。在几组生产中常用的放电参数(加工电流、脉冲宽度、脉冲间隙)条件下,加工A8工具钢,分别得到每种放电参数对表面粗糙度和材料去除率的具体影响规律,结果表明:随着加工电流的增大,加工后材料表面粗糙度和材料除去率同时增大且趋势相似;随着脉冲宽度的增大,加工后材料表面粗糙度和材料除去率同时增大;随着脉冲间隙的增大,材料除去率呈递减趋势,加工后材料表面粗糙度前期递减,在脉冲间隔8μs后减小趋势放缓,在脉冲间隔10μs时达到最小值,在脉冲间隔大于10μs后略有升高,变化幅度不大。研究结果为实际生产中电火花线切割加工A8工具钢提供技术参考,可以根据不同的生产要求选择合适的放电参数组合。     

电火花线切割轮廓逼近法加工回转件方法研究

基于轮廓逼近法提出电火花线切割加工大余量回转件工艺方法,包括粗加工多边形成型阶段、半精加工棱边去除阶段及精加工中的放电磨削加工阶段。确定多边形边数,定义残差值并得到残差值与边数的对应关系。理论计算及实验结果表明：边数大于32后,残差值变化率开始变小;残差值小于0.5 mm有利于回转件的加工。边数确定后,为减少加工时间,针对轮廓逼近提出了恒定角度法和倍数法2种加工方法,并通过加工面积的计算和比较得出相对高效的成型方法。结果表明：相同工件直径条件下,采用倍数法的加工面积小于恒定角度法,加工时间减少约34%。在中走丝机床上通过加工钛合金工件对改进的工艺方法进行了验证,加工完成后通过激光位移传感器测得回转件径向圆跳动在±10 μm内。     

形状记忆合金非常规加工综述(英文)

形状记忆合金(SMAs)由于具有多种特殊性能,如伪弹性、形状记忆效应、生物相容性、高的比强度、高耐蚀性、高耐磨性、良好的抗疲劳性能,成为不断发展的先进材料。因此,形状记忆合金被广泛应用于航空航天、医疗和汽车等方面。然而,由于严重的加工硬化和伪弹性,形状记忆合金的传统加工会造成严重的刀具磨损、费时以及低维畸变。这些材料可以使用非传统的方法,如激光加工、水射流加工(WJM)和电化学加工(ECM)进行机械加工,但这些方法受限于该材料的复杂性和力学性能。而电火花加工(EDM)和线切割(WEDM)能够很好的加工具有复杂形状和精密尺寸的形状记忆合金。介绍大量关于使用电火花和线切割加工形状记忆合金的研究,分析不同研究的差异,并展望未来的研究趋势。     

电火花线切割加工薄壁零件热弯曲的形成机制及实验研究

电火花线切割被广泛认为是一种热物理蚀除工件材料的加工方式,具有不受材料硬度限制、表面质量高和无切削应力等优点。然而,热物理蚀除方式会在工件内部形成热应力,在加工薄壁类零件(厚度小于2 mm)时会体现为热弯曲变形,限制了电火花线切割加工在精密薄壁类零件领域的应用。通过电火花线切割加工薄壁类零件的热平衡分析,揭示薄壁类零件热弯曲的形成机制。设计正交实验,采用方差分析方法,分析加工工艺参数对薄壁类零件热弯曲变形的影响规律,并阐明这些影响规律形成的根本原因。根据方差分析结果,得到的热弯曲变形最小的加工工艺参数组合。实验结果表明:最优加工工艺参数组合可使得热弯曲变形减小到37.0μm。     

混粉电火花放电蚀坑及温度场仿真研究

混粉电火花加工是一种新型加工工艺,通过在工作液中添加微细粉末,显著改善加工表面粗糙度。电火花加工表面粗糙度的形成与放电蚀坑大小有直接关系,而放电蚀坑大小与单次脉冲放电温度场有密切联系。为了进一步提高混粉加工表面质量,利用ANSYS软件对放电点温度场进行了模拟与分析,得到了工件表层温度场的分布规律,揭示了材料去除机制,阐明了加工表面粗糙度与温度场的关系,对预测和改善混粉加工表面质量及日后生产实际应用提供了一定的理论依据。     

百叶窗模具结构与加工工艺分析

介绍百叶窗模具结构及加工工艺特点,针对三坐标数控铣在百叶窗模具加工中不能满足技术要求的问题,提出将三维数字模型转换成二维图形,采取二维线切割与三坐标数控铣混合加工百叶窗模具的工艺方法,解决了三坐标数控铣加工百叶窗模具的不足。     

Fixed abrasive diamond wire machining—part I: process monitoring and wire tension force

The process monitoring and mechanics of fixed abrasive diamond wire saw machining are investigated in this study. New techniques to affix diamond particles to a steel wire core have advanced to make this process feasible for the machining of ceramics, wood, and foam materials. Developments in fixed abrasive diamond wire machining are first reviewed. Advantages of using fixed abrasive diamond wire machining are then introduced. The process monitoring and signal processing techniques for measuring the cutting forces, wire speed, down feed rate, and wire bow angle in diamond wire saw machining are developed. The application of a capacitance sensor to measure the wire bow and a procedure to convert the wire bow to vertical cutting force in a rocking motion wire saw machine are developed. The tension force of the wire during cutting is also derived and discussed.     

Sinking EDM simulation by determining discharge locations based on discharge delay time

This paper describes the development of a sinking EDM simulation method by determining discharge locations. The simulation repeats the routine modelling of the process of each discharge consisting of determination of discharge location, removal of electrodes, generation and displacement of debris particles, and tool electrode feeding. The spot with the shortest discharge delay time calculated probabilistically assuming that an exponential distribution applies is searched for and this is determined to be the discharge location. The tool electrode feed is also determined based on discharge delay time like actual feed control. Electrode shapes and gap width distributions simulated for different working surface areas agreed with experimental results.     

PtIr高温合金电火花线切割工艺参数优化研究

为了提高PtIr高温合金电火花线切割加工的表面质量及减少切割边缘毛刺,研究电流、脉宽、脉间距对PtIr合金电火花线切割加工效果的影响。结果表明：加工过程的参数对材料的表面粗糙度及边缘毛刺有重要影响。对电火花线切割加工工艺参数进行了优化,电流为5 A、脉宽5μs、脉距5μs时、加工速度150步/S、钼丝直径0.1 mm时加工效果最佳,表面粗糙度Ra值为0.14μm,切割精度公差可控制在±0.006 mm内。     

304 不锈钢电火花线切割加工表面性能研究

目的研究电火花线切割工艺对金属材料加工表面质量的影响规律,分析加工表面的机械性能。方法利用电火花线切割加工技术,对304不锈钢工件进行表面切割试验,应用马尔轮廓测量仪、扫描电镜、超景深电子显微镜及纳米压痕仪观察电火花加工表面的粗糙度变化规律和表面微形貌特征,获取横截面纳米硬度变化曲线。设计正交试验,获得最优加工参数。结果脉冲宽度和峰值电流对奥氏体不锈钢加工表面形貌的形成机制有显著影响,加工表面粗糙度受电参数的影响较大,加工表面的表层及次表层组织主要由塑性变形层与回火多相组织层共同构成,厚度与纳米硬度的变化受电参数的影响较大。结论电参数对表面质量的影响程度顺序为脉冲宽度、峰值电流、放电间隔,为得到较优加工表面层,应优先选择脉冲宽度为16μs,放电间隔为96μs,峰值电流为1.5 A的工艺参数组合。单个脉冲能量对加工层的厚度以及表层的纳米硬度呈现出近似线性规律。     

State of the art in wire electrical discharge machining (WEDM)

Wire electrical discharge machining (WEDM) is a specialised thermal machining process capable of accurately machining parts with varying hardness or complex shapes, which have sharp edges that are very difficult to be machined by the main stream machining processes. This practical technology of the WEDM process is based on the conventional EDM sparking phenomenon utilising the widely accepted non-contact technique of material removal. Since the introduction of the process, WEDM has evolved from a simple means of making tools and dies to the best alternative of producing micro-scale parts with the highest degree of dimensional accuracy and surface finish quality.Over the years, the WEDM process has remained as a competitive and economical machining option fulfilling the demanding machining requirements imposed by the short product development cycles and the growing cost pressures. However, the risk of wire breakage and bending has undermined the full potential of the process drastically reducing the efficiency and accuracy of the WEDM operation. A significant amount of research has explored the different methodologies of achieving the ultimate WEDM goals of optimising the numerous process parameters analytically with the total elimination of the wire breakages thereby also improving the overall machining reliability.This paper reviews the vast array of research work carried out from the spin-off from the EDM process to the development of the WEDM. It reports on the WEDM research involving the optimisation of the process parameters surveying the influence of the various factors affecting the machining performance and productivity. The paper also highlights the adaptive monitoring and control of the process investigating the feasibility of the different control strategies of obtaining the optimal machining conditions. A wide range of WEDM industrial applications are reported together with the development of the hybrid machining processes. The final part of the paper discusses these developments and outlines the possible trends for future WEDM research.     

微细电火花线切割加工表面耐蚀性的试验分析

为了了解不同材料在微细电火花线切割(MWEDM)加工下的表面耐蚀性,分别对W18Cr4V,60Si2Mn和M42三种材料进行加工,借助微电解池装置和电化学工作站对各试件做表面耐蚀性试验,进行电化学阻抗谱和动电位极化曲线测量分析,采用倒置金相显微镜对腐蚀后的表面进行拍照观察并与平磨加工表面进行对比.结果表明,微细电火花线切割加工表面耐蚀性整体优于平磨加工表面;对于不同材料,MWEDM表面耐蚀性存在显著差异;对于同种材料,选取适当的加工参数能够得到耐蚀性较好的表面.     

电火花线切割NC代码编译与运动轨迹仿真研究

针对目前电火花线切割数控系统NC代码编译复杂并且几乎不具备扩展性和通用性的问题,提出一种简单、清晰的线切割NC代码编译方案。基于.NET开发平台,采用C#开发语言,通过正则表达式进行词法分析,使用自定义函数进行语法分析。采用该方案能对简单平面图形、锥度切割和上下异形切割进行编译。通过.NET绘图功能显示图形,利用逐点比较插补法,对直线和圆弧进行插补,实现运动轨迹仿真。     

HS-WEDM加工工艺指标的主要影响因素及其控制

高速走丝电火化线切割机床是目前我国生产和使用的主要线切割机种。本文就笔者在教学实习、生产实践中总结的影响HS—WEDM加工工艺指标的一些主要因素及其相关控制进行了分析、说明。     

基于混粉加工的电火花成型铣削

在研究分析电火花成型铣削的工艺方法,工艺特点及适用范围基础上,提出将其与混粉工艺相结合,应用于模具成型零件的制造,可提高加工效率,获得镜面效果的高精度型腔,使电火花加工成为模具型腔的最终精加工.