空气中微细电火花沉积与去除可逆加工技术研究

论述了一种新的电火花加工方法。它使用通用的电火花成形加工机床,利用常见的电极材料,在空气介质中,通过脉冲放电在工件表面上沉积生长电极材料,再通过反转极性和适当的轨迹控制对所生成的沉积材料进行有选择的去除加工,进而实现材料的生长与去除可逆加工。通过对电火花加工理论的研究,预测和论证了实现这一新加工方法的可能性和实现条件。通过试验成功地将钢、铜和钨三种电极材料沉积到工件上,形成直径为 100~240 mm、高度为1 000~2 500 mm的微小圆柱体。并对沉积物进行了选择去除,实现了在同一设备上的可逆电火花加工。对沉积材料的致密性、硬度及其与工件的结合强度等进行了系统的分析,表明沉积物组织致密、坚硬,可以满足功能材料的要求。     

弱电解质溶液EDM/ECM复合加工机理研究

弱电解质溶液中利用电沉积补偿电极损耗的电火花/电化学复合加工技术可以大幅降低电极损耗,对提高微细电火花加工效率具有重要意义。由于该工艺方法是EDM/ECM复合加工领域一个新的研究方向,研究成果很少。为加深对利用电沉积补偿电极损耗的电火花/电化学复合加工技术的认识,基于实验结果,对弱电解质溶液中的电火花/电化学复合加工的材料去除机理、放电通道形成机理及电极损耗机理进行了初步探索,得到了以下结果:电火花放电蚀除和电化学溶解共同将工件材料去除;大量气泡存在于电极间隙使复合加工放电通道的形成异于电火花放电加工;电沉积作用和电火花放电蚀除共同对工具电极损耗产生影响。     

一种利用WC电极的电火花表面改性技术

研究了1种在普通电火花加工机床上实现金属工件表面改性的新方法。它是在传统电火花加工方法的基础上，采用WC烧结体电极和普通煤油工作液，在工件表面形成1层硬质陶瓷层，从而达到改善工件表面性能的目的。系统地对放电沉积原理进行了探讨，在大量试验的基础上，总结了放电沉积的工艺方法。通过扫描电镜、电子探针、X射线衍射分析、摩擦磨损等一系列试验手段，对形成的沉积层特性进行了定量和定性的分析。试验与分析表明，用电火花加工的方法进行表面处理是1种极具潜力的改性方法。     

电火花成型机床空气中放电沉积试验研究

通过在电火花成型机床上采用YK10硬质合金棒做工具电极、M2高速钢为工件进行空气中电火花放电沉积试验研究,对空气中电火花放电沉积的规律进行了探讨。对沉积层组织结构、能谱和硬度的检测结果表明选择合适的工艺参数可获得具有较高显微硬度的合金强化层。     

材料晶界和晶粒对电火花微细加工的影响研究

为了在电火花微细加工中确定合理的工具损耗补偿工艺与加工工艺,提高微小零件微细加工的质量,通过在合金材料上选择晶粒和晶界部位大量加工微孔以及其后的统计分析,研究了微细电火花加工过程中工件材料晶粒与晶界对放电间隙、材料去除速度以及电极体积相对损耗等加工特性的影响。研究结果表明,由于工件材料中晶粒和晶界在成分、熔点、热导率以及机械性能等方面的差异,当用微细电火花进行微细加工,特别是当加工尺度小于工件材料的晶粒尺寸时,晶粒和晶界的加工特性具有明显差别,制订工具损耗补偿工艺和加工工艺时应该考虑到材料微观结构对加工过程的影响。     

电火花沉积技术应用实例

金属表面电火花沉积工艺是将电源存储的高能量电能，在金属电极（阳极）与金属母材（阴极）间瞬间高频释放，通过电极材料与母材间的空气电离形成通道，使母材表面产生瞬间高温、高压微区；同时离子态的电极材料在微电场的作用下融渗到母材基体，形成冶金结合。电火花沉积工艺兼有焊接的一些     

电火花加工中电极材料对加工性能影响的试验研究

以电火花多电极加工3Cr13模具型腔为研究对象,以提高材料去除率和降低电极损耗为目标,对负极性标准切入加工时不同电极材料的电火花加工性能(加工效率、电极损耗)进行研究,设计并进行了不同工艺参数下紫铜电极和Cu50W铜钨合金电极加工试验,获得了不同条件下的材料去除率和电极相对损耗参数,并对多电极电火花加工工艺及经济性进行了分析,结果表明:相同工艺参数下,加工性能因电极材料热学性能不同而不同,Cu50W铜钨合金的材料去除率约为紫铜的85.7％,而电极相对损耗约为紫铜的42.9％,从而为电火花加工不锈钢模具材料的电极选择提供了理论依据.     

水气联合电火花加工实验研究

将自来水和压缩空气作为电介质,使用实心成形电极对钢件进行电火花加工实验,探讨其加工机理。实验证明,空气与水的配合状况对电火花效果起着决定性作用;加工中可以获得较大的加工速度(材料蚀除速率)和较低的电极相对损耗,加工后工件表面粗糙度值一般较大;水气联合电火花加工适宜于高电流大脉宽加工。     

微细电火花加工倒凹坑效应的研究

对微细电火花圆柱电极损耗出现倒凹坑效应的影响因素进行研究。通常微细电火花电极损耗稳定后,加工端面为半球形,然而在特定的加工条件下,电极端面呈倒凹形状,微孔底端为山状突起,这种异常损耗会破坏电极形状精度而影响加工零件的尺寸精度。通过改变放电能量与放电间隙流体状态等微细电火花加工工艺参数,对比不同实验条件下电极端面形状损耗的变化情况,经检测,出现倒凹坑效应的微孔底端突起为电极材料沉积。实验研究结果表明:电极熔融沉积是电极损耗倒凹坑效应出现的主要原因。     

电火花加工中减小电极损耗的方法和实验研究

制作一种电火花小孔加工用Cu-Ni复合电极,其原理是基于电镀层和基体材料性能的差异,改变电极材料电蚀性能,保证电极端面和侧面的均匀损耗。在D703F型高速电火花小孔加工机床上,用Cu-Ni电极加工1Cr18Ni9Ti不锈钢材料,与常用的普通铜管电极对比。结果表明:在相同的加工条件下,Cu-Ni复合电极的电极损耗明显降低,同时改善了因电极损耗引起的被加工工件的尺寸精度和形状精度。     

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.     

Micro Electrical Discharge Machining Deposition in Air for Fabrication of Micro Spiral Structures

Micro electrical discharge machining(EDM) deposition process is a new micro machining method for fabrication of metal micro structures. In this process, the high level of tool electrode wear is used to achieve the metal material deposition. Up to now, the studies of micro EDM deposition process focused mainly on the researches of deposition process, namely the effects of discharge parameters in deposition process on the deposition rate or deposition quality. The research of the formation of micro structures with different discharge energy density still lacks. With proper conditions and only by the z-axis feeding in vertical direction, a novel shape of micro spiral structure can be deposited, with 0.11 mm in wire diameter, 0.20 mm in outside diameter, and 3.78 mm in height. Then some new deposition strategies including angular deposition and against the gravity deposition were also successful. In order to find the forming mechanism of the spiral structures, the numerical simulation of the transient temperature distribution on the discharge point was conducted by using the finite-element method(FEM). The results show that there are two major factors lead to the forming of the spiral structures. One is the different material removal form of tool electrode according with the discharge energy density, the other is the influenced degree of the movement of the removed material particles in the discharge gap. The more the energy density in single discharge is, the smaller the mass of the removed material particles is, and the easier the movements of which will be changed to form an order tendency. The fine texture characteristics of the deposited micro spiral structures were analyzed by the energy spectrum analysis and the metaliographic analysis. It shows that the components of the deposited material are almost the same as those of the tool electrode. Moreover the deposited material has the brass metallic luster in the longitudinal profile and has compact bonding with the base material. This research is useful to understand the micro-process of micro EDM deposition better and helpful to increase the controllability of the new EDM method for fabrication of micro structures.     

基于电火花加工方法的表面改性技术研究

研究了一种在普通电火花加工机床上实现金属工件表面改性的新方法。它是在传统电火花加工方法的基础上，采用TiC-Co半烧结体电极和普通煤油工作液，在工件表面形成一层硬质陶瓷层，从而达到改善工件表面性能的目的，这种新方法被称之为放电沉积。对放电沉积原理进行了探讨，在大量试验的基础上，总结了放电沉积的工艺方法。通过扫描电镜、电子探针、X射线衍射分析、摩擦磨损等试验，对形成的沉积层特性进行了定量和定性分析。最后利用该方法在普通的高速钢车刀上进行了初步应用。试验与分析表明，该方法是一种极具潜力的金属表面改性方法。     

气中微细电火花线切割加工实验研究

气中微细电火花线切割加工用气体作加工介质,可加工难切削材料、复杂零件,具有低应力、无毛刺等特点。研究了气中微细电火花线切割加工中开路电压、极间电容、气压以及相对进给速度对试件切槽宽度和表面粗糙度的影响。实验结果显示：气压、相对进给速度和极间电容对切槽宽度和表面粗糙度有明显影响,开路电压的变化对加工结果产生有限影响。     

Experimental and numerical investigations of material removal process in electrochemical discharge machining of glass in discharge regime

Electrochemical discharge machining (ECDM) can be applied as a non-traditional processing technology for machining non-conductive materials such as glass and ceramics, based on the phenomena of evoked electrochemical discharges around the tool electrode. The material removal mechanism of ECDM is noticeably complex and difficult to experimentally characterize. In this paper, finite element models were proposed to predict the material removal in the ECDM discharge regime. First, the single-pulse discharge on a tapered electrode was modeled. It was found that about 30.5% of the discharge energy is transferred to the workpiece. The continuous discharge on a cylindrical electrode was thereafter modeled according to this phenomenon, in which the removal of a layer of the workpiece material starts from the projected contour of the edge of the electrode end and extends inward during the ECDM processing. The effective discharge ratio for material removal was calculated to be 10.1%. The drilling depths of holes at different applied voltages were predicted by the proposed finite element method. It was found that the predicted values were consistent with the experimental results.     

半导体硅电极多通道放电机理研究

为了实现电火花加工同一时刻形成多个放电通道蚀除工件,克服现有放电加工理论中同一时刻仅有一个放电通道蚀除工件的限制,提出了采用半导体材料作为电极进行放电加工的新方法。首先,通过试验证明以半导体硅为电极加工金属可以形成多通道放电;其次,建立了半导体电极单通道放电等效电路模型,发现半导体电极在放电加工时不是一个等势体,并进行了电势差分布试验,验证了多通道放电形成的原因是远离放电点处的电势较高,可以同时形成击穿产生放电;最后,进行了半导体硅电极单脉冲放电试验及成型加工试验。试验结果显示,半导体硅电极通过1次脉冲放电同时形成多个放电通道,有效地分散放电能量,相较于金属电极,每个放电坑的直径和深度都显著减小。在相同放电参数下,对比钢电极,用硅电极进行电火花加工的表面粗糙度值下降71.7%。     

Experimental research on effects of process parameters on servo scanning 3D micro electrical discharge machining

Servo scanning 3D micro electrical discharge machining (3D SSMEDM) is a novel and effective method in fabricating complex 3D micro structures with high aspect ratio on conducting materials.In 3D SSMEDM process,the axial wear of tool electrode can be compensated automatically by servo-keeping discharge gap,instead of the traditional methods that depend on experiential models or intermittent compensation.However,the effects of process parameters on 3D SSMEDM have not been reported up until now.In this study,the emphasis is laid on the effects of pulse duration,peak current,machining polarity,track style,track overlap,and scanning velocity on the 3D SSMEDM performances of machining efficiency,processing status,and surface accuracy.A series of experiments were carried out by machining a micro-rectangle cavity (900 μm×600 μm) on doped silicon.The experimental results were obtained as follows.Peak current plays a main role in machining efficiency and surface accuracy.Pulse duration affects obviously the stability of discharge state.The material removal rate of cathode processing is about 3/5 of that of anode processing.Compared with direction-parallel path,contour-parallel path is better in counteracting the lateral wear of tool electrode end.Scanning velocity should be selected moderately to avoid electric arc and short.Track overlap should be slightly less than the radius of tool electrode.In addition,a typical 3D micro structure of eye shape was machined based on the optimized process parameters.These results are beneficial to improve machining stability,accuracy,and efficiency in 3D SSMEDM.     

敞开式离子源和微型气泵集成的微型针-柱放电结构芯片设计与实验分析

采用LIGA(Lithographie,Galvanoformung,Abformung)工艺设计加工了一种微型针-柱放电结构芯片,可实现敞开式离子源和微型气泵的系统集成。此微型放电结构由采用电镀铜加工而成的针电极、上圆柱电极和下圆柱电极组成,针-柱间距有1mm、2mm两种规格。在室温、大气压环境、无外界通入气流的条件下,通过在针-柱电极上加载负直流高压,可产生稳定的气体放电。利用风速计testo 405-V1测量芯片气体放电产生的离子风风速,结果表明针-柱间距为2mm时产生的离子风流速最大,可达0.79m/s。对针-柱间距2mm规格的微型芯片进行乙酸进样电离实验,当针-柱之间产生稳定的电晕放电后,可发现位于芯片出口处已被去离子水润湿的PH试纸变红。此时利用微弱电流检测系统采集电离产生的离子,当放电电压为-3300V时,通过微弱电流采集系统检测到的电流信号可达120pA。采用LTQ XL离子阱质谱仪,对芯片电离丙酮、无水乙醇和乙酸乙酯的离子产物进行检测,所得到的主要物质为质子化单体离子和二聚物离子。放电产生离子风风速以及乙酸的进样和电离实验表明,基于LIGA的微型针-柱结构芯片可实现大气压环境下敞开式离子源和微型气泵的双重功能。     

Influence of electrical discharge machining parameters on cutting parameters of carbon fiber-reinforced plastic

Today the use of high-strength carbon fiber-reinforced plastics (CFRP) composite as a material for many engineering applications is showing an increasing demand in the industry. These composites are replacing the traditional use of steel because they offer many advantages such as very light weight, high strength, and high stiffness associated with good corrosion-resistant properties. Unfortunately, there is little technological knowledge on the electrical discharge machining (EDM) process of high-strength composite materials, especially about the CFRP. In this work, a study has made into the possibility of using EDM process as a means of machining CFRP composite. Various cutting conditions such as peak current, pulse-on time, pulse-off time and open-circuit voltage were selected to perform electrical discharge machining. The effect of electrode rotation was also studied. Optimum cutting conditions and machine settings for EDM were chosen for machining CFRP composites.     

混粉电火花加工中极性效应的研究

为研究极性效应对混粉电火花加工的影响规律．采用钢对钢加工、铜对钢加工两种电极组合在添加硅粉的煤油工作液及普通煤油工作液中进行实验，并更换不同的极性，考察了两极材料的去除率和表面粗糙度，结果表明负极总能得到更高的材料去除率，而正极总能得到更低的表面粗糙度值。此现象可从两极表面能量密度差异的角度予以解释。