电火花加工工具电极制备技术研究进展

工具电极是电火花加工中非常重要的一项因素,电极的制备是实现电火花加工的关键.本文介绍了电火花加工工具电极制备技术最新的研究进展,包括石墨电极、聚合物复合材料电极、电火花表面改性电极、电火花磨削用电极和微细电极的制备方法,以及电铸法和基于快速成形技术的电极制备方法等.     

微细阵列群电极电解加工关键技术研究

提出了基于阴极优化的微细阵列圆柱凸台群电极电化学腐蚀加工法。根据电化学腐蚀基本原理,通过有限元方法分析计算群电极电化学腐蚀加工过程中的电极表面电场分布,以电流密度分布均匀性为目标,优化设计阴极形状,并进行阵列群电极制备。在制备出直径均匀的阵列群电极的基础上,探索用局部涂胶保护法制备大长径比的盘状阵列群电极,用于微细孔电解加工,进一步提高电解加工的定域性。     

基于LIGA技术的微细电火花加工优化研究

比较了活动掩膜法与固定掩膜法得到的PMMA胶结构,实验表明固定掩膜法更适合于多次曝光.结合LIGA技术和微细电火花加工的优点,用LIGA技术制备出具有复杂形状的铜微细工具电极,再用该工具电极进行微细电火花加工,在不锈钢上加工出异形微细孔.并通过进一步调整电火花加工工艺参数,优化了加工尺寸精度和表面粗糙度.     

型孔电解加工阴极优化试验研究

为解决电解加工型孔的加工稳定性和形状精度等问题,建立了异形孔电解加工稳定过程中加工间隙数学模型,分析了工具阴极结构对加工区域和非加工区域的电场及其均匀性以及其对电流密度与加工效果的影响,通过优化工件结构改善了加工间隙内的电场分布,使工件形状精度显著提高,并进行相关试验对仿真结果进行验证。得出结论:在相同的电解加工参数下,工具电极的结构对工件的形状精度有着显著的影响,通过优化工具电极结构,改善加工间隙内的电场分布与电流密度,让加工间隙内的流场更为稳定,使工件侧壁垂直度提高,提高了电解加工的形状精度与加工稳定性。     

模板射流电沉积微制造工艺的仿真优化设计

模板射流电沉积是一种微尺度加工的微成形方法,体现了增材制造的加工思想。微沉积过程中出现的沉积不均匀是阻碍增材加工过程的主要因素。通过对不同制备工艺参数下的沉积均匀性进行分析,并以有限元分析软件对阴极表面的电场分布进行了模拟,结合工艺实践得到沉积表面的电场分布规律。结果表明,采用电流密度300 A/dm~2、阴极喷嘴与阴极尺寸比例1∶1、施加屏蔽,可取得较好的均匀度,完成了对微型器件的制备。     

“ISEM—9”论文简介

用掺入粉末的工作液进行电火花加工由于工具电极和工件表面间形成大的静电电容,大面积电火花加工难以获得光洁表面。本文作者们曾用硅电极有效地解决了这一问题,并使加工表面耐腐蚀、耐磨损。然而用很硬很脆的硅作为工具电极材料有难于成形的缺点。本文介绍在工作液中掺入硅、铝、石墨等粉末后对电火花精加工所产生的效果。实验结果表明,即使所用的工具电极是紫铜电极,在石油类工作液中掺入上述粉末对于获得光洁表面非常有效。在同样的加工条件下,用铝粉或石墨粉能使加工表面比用硅粉时更为光洁。当在每升工作液中掺入2克铝粉而用紫铜工具电极加工 SKH—51高     

低温冷却工具电极电火花加工研究

以高温镍基合金Inconel718为加工材料,利用液氮蒸发气与空气混合形成低温冷却气体对电火花工具电极进行冷却,以降低电火花工具损耗。以冷却温度为变量进行电火花加工研究。利用粗糙度测量仪TR200和扫描电镜Quanta250对工件表面粗糙度和表面形貌进行分析。结果表明:当脉冲作用时间较短时(脉冲宽度90μs),在相同电参数下,低温冷却电火花加工可降低加工工件的表面粗糙度,在0℃时的表面粗糙度最低,比普通电火花加工的低3.7%～9.5%;随着冷却温度的降低,表面粗糙度会有所增加。电极损耗随着冷却温度的降低而降低,冷却温度在-60℃时的电极损耗比0℃的降低了40%以上。当电参数较小时,低温冷却电火花加工后的工件表面形成微裂纹且裂纹密度随冷却温度的降低而增加。在一定参数下,低温冷却工具电极对降低工件表面粗糙度和工具电极损耗效果显著,某些情况下可能会增加表面的微裂纹。     

电化学腐蚀法制备倒锥状微细电极的试验研究

以电化学腐蚀加工法为基础,提出了一种加工复杂形状微细电极的工艺方法.利用端面绝缘的方法改变阳极的局部导电性,使阳极和阴极之间的电场分布发生变化,从而得到倒锥状微细电极.通过试验成功地制备出倒锥状微细电极,并结合对比圆柱状电极进行了微孔电解加工试验,结果证明倒锥状电极在微孔电解加工中能获得更好的加工定域性.     

固定阴极电化学射孔的成形规律研究

根据电场理论,提出了一种研究固定阴极电化学射孔成形规律的新的处理方法,分析了该加工方式下阴极表面电荷密度及加工区的电场强度、电流密度、加工速度等在加工过程中的变化规律,为这种简易加工方式的合理应用提供了严密的理论依据。     

新型电火花加工电极——CVD金刚石

在电火花加工中,工具电极是一项非常重要的因素,电极材料的性能将影响电极的电火花加工性能（材料去除率、工具损耗率、工件表面质量等）,因此,正确选择电极材料对于电火花加工至关重要。     

电铸沉积层性能的试验研究

进行了直流和脉冲电流铜沉积实验,分析了沉积层微结构和电铸层性能,并安排了放电工试验,结果表明有机用脉冲电流可以使电沉积层的某些性能得到改善,当电铸层作为电火花加工电极时,脉冲电流电铸可以降低电极损耗率。     

电铸制备TiB_2/Cu复合材料的性能

使用粒度约为3μm的导电陶瓷TiB_2颗粒作为铜基复合材料的增强相,在酸性硫酸铜溶液中用电铸方法制备TiB_2/Cu电火花加工用工具电极。用扫描电镜和金相显微镜观察其组织结构,用维氏硬度计测量硬度,用中性盐雾试验测量其耐腐蚀性,用电火花加工脆硬材料衡量其抗电蚀性。结果表明:电铸Cu与TiB_2/Cu晶粒平均直径分别为30,10μm,硬度分别为984,1235 MPa,腐蚀失重分别为47.8,40.3 mg;TiB_2颗粒的加入可显著细化晶粒,提高硬度、耐腐蚀性和抗电蚀性。     

基于LOM原型快速制造电火花加工电极的研究

利用LOM原型，把化学镀、电铸和电弧喷涂技术结合起来快速制造电火花加工电极，是实现模具快速制造的有效途径。本文分析了LOM原化学镀工艺的关键问题，通过反复试验，解决了LOM纸质原型的导电化问题，并经过脉冲电铸铜及以电弧喷涂紫铜作背衬，得到了适用于电火花成形加工的电铸铜电极。该工艺方法尤其适合于生产中、小型零件的模具的快速制造。     

A plate capacitor model of the EDM process based on the field emission theory

The electrical discharge machining (EDM) process is, by far, the most popular amongst the non-conventional machining processes. The technology is optimum for accurate machining of complicated shapes in hard materials, required in the modern industry. However, although a lot of EDM machines are widely applied for many years, fundamental knowledge of the process is still limited. The complex nature of the process involves simultaneous interaction of thermal, plasma temperature and electromagnetism factors, which makes the machining process modeling very difficult. In this paper, based on the analysis of the electric discharge machining (EDM) process, a plate capacitor model is constructed to describe the discharging process in a pulse time. The whole EDM process is divided into four stages, successively as interelectrode electric-field establishment, electric discharge channel formation, stable EDM and deionization, the interaction of each stage and the distribution function of EDM energy are deduced using the field electron emission theory. For the purpose of analyzing the effect of the single factor, a set of machining through-hole experiments were carried out and investigated. The study shows that critical electric-field intensity and the effective discharging time rate play major roles on the improvement of machining efficiency; the model can explain the differences of machining efficiency using different materials of tool pole and different EDM parameters; and the theoretical results are concordant with the experimental data well.     

High-speed EDM milling with moving electric arcs

A novel high-speed electrical discharge machining (EDM) milling method using moving electric arcs has been proposed in this study. We connected a copper electrode rotating rapidly around its axis and a work piece to a DC power supply to generate a moving electric arc. To ensure high relative speed of any point on the electrode with respect to the work piece, the electrode was shaped like a pipe. It was observed that the electric arcs move rapidly within the discharge gap due to the revolution of the tool electrode, removing the materials on the electrode along the track of the arc roots. To explore the characteristics of machining with moving electric arcs, an EDM milling apparatus was devised. Two planes with approximately the same roughness were machined separately by this equipment and a traditional EDM machine for comparison. It was found that a much higher material removal rate can be easily achieved by EDM milling with moving electric arcs. In the meanwhile, wear of the tool electrode in this new method is negligible, which is greatly favorable for machining accuracy. The microstructures of these surfaces were also investigated for further information.     

双层微齿轮型腔镶块电铸均匀性 Ansys 模拟与优化

目的提高双层微齿轮模具型腔镶块电铸过程中铸层的均匀性。方法利用Ansys对双层微齿轮型腔镶块电铸过程中电场强度的分布情况进行模拟,确定施加绝缘挡板的可行性。采用正交试验考察绝缘挡板几何及位置尺寸对电场强度的影响,应用灰关联理论得出最优工艺参数组合。结果绝缘挡板的施加,在一定条件下可以使光刻胶电铸层厚度更为均匀和平整。路径a的相对误差由62.48%降低到33.18%,路径b的相对误差由48.01%降低到8.91%。结论施加绝缘挡板可以提高双层微齿轮模具型腔镶块电铸过程中铸层的均匀性。     

Experimental characterization of dry EDM performed in a pulsating magnetic field

This paper presents an investigation of the hybrid dry EDM process performed in a pulsating magnetic field for improving process performance. In this study, the pulsating magnetic field is applied tangential to the electric field, for increasing the movement of electrons and degree of ionization in the plasma. Experiments with parametric variations showed that this hybrid approach leads to productivity-improvement by 130% and zero tool wear as compared to the dry EDM process without the magnetic field. The improvement in surface quality is illustrated by scanning electron microscopy (SEM).     

电火花加工工具电极耐电蚀性能的试验研究

电火花成形加工过程中，工具电极的损耗是影响工件几何形状精度的主要因素之一。从工具电极的制作工艺着手，分别利用直流和脉冲电流电铸工具电被，进行了电极放电损耗试验。通过试验和SEM形貌研究分析了工艺参数对电极耐电蚀性能的影响，并用正交试验法优化了工艺参数。结果表明，脉冲电铸铜电极可降低损耗，且在一定工艺条件下脉冲电铸电极具有优异的耐电蚀性能。     

数控电火花高速高精度加工

分析了数控电火花加工特点,介绍了LYNUC数控系统HiPT高速高精度核心控制模块的切削特点。通过实际切削加工案例的分析,证实了在辅助电火花放电加工的切削工序中,HiPT高速高精度模块可以获得高品质的切削电极和放电加工工件,且有效地提高数控电火花加工表面精度和加工效率,降低了生产成本。     

EDM performance of Cr/Cu-based composite electrodes

Electrode materials for electrical discharge machining (EDM) are usually graphite, copper and copper alloys because these materials have high melting temperature, and excellent electrical and thermal conductivity. The electrodes made by using powder metallurgy technology from special powders have been used to modify EDM surfaces in recent years, to improve wear and corrosion resistance. However, electrodes are normally fabricated at high temperatures and pressures, such that fabrication is expensive. This paper proposes a new method of blending the copper powders contained resin with chromium powders to form tool electrodes. Such electrodes are made at low pressure (20 MPa) and temperature (200 °C) in a hot mounting machine. The results showed that using such electrodes facilitated the formation of a modified surface layer on the work piece after EDM, with remarkable corrosion resistant properties. The optimal mixing ratio, appropriate pressure, and proper machining parameters (such as polarity, peak current, and pulse duration) were used to investigate the effect of the material removal rate (MRR), electrode wear rate (EWR), surface roughness, and thickness of the recast layer on the usability of these electrodes. According to the experimental results, a mixing ratio of Cu–0wt%Cr and a sinter pressure of 20 MPa obtained an excellent MRR. Moreover, this work also reveals that the composite electrodes obtained a higher MRR than Cu metal electrodes; the recast layer was thinner and fewer cracks were present on the machined surface. Furthermore, the Cr elements in the composite electrode migrated to the work piece, resulting in good corrosion resistance of the machined surface after EDM.