微细电火花加工关键技术及工艺研究

文中基于新研发的一套微细电火花精密加工系统μEDM-50,介绍了研发过程中探索出的最小脉宽可以达纳秒级的微能脉冲电源以及一些针对微细电火花加工的特点形成的特殊工艺.微能脉冲电源具有主动消电离环节,可以减少脉间的残余电荷放电,提高加工表面质量;特殊工艺有利于提高系统的加工精度和效率,提高微细电极的安全性.最后,介绍了一些金属零件上典型的微小特征精密加工实验以及放电沉积实验.该系统加工特征的尺寸范围主要介于数十微米到数毫米内.     

多轴精密数控电火花成形机的研制

从机床结构、脉冲电源系统、数控系统、精密分度轴等几方面介绍了采用引进消化吸收、再创新后的研究成果--多轴精密数控电火花成形机,并用典型的加工实验验证了该机床达到的技术水平和丰富的功能,为精密复杂模具和零件的电火花加工提供了良好的制作母机.     

第八届国际电加工学术讨论会论文目录

电火花加工 1.电火花加工工艺准备工作自动化系统苏联 2.精密电火花加工过程的数学模型苏联 3.高能量密度的热流脉冲对金属结构的影响     

基于总线的线切割控制系统

目前高频电火花线切割加工机床大量应用于精密加工中.本文开发了电火花线切割加工机床上位机与下位机CAN总线实时通讯系统,满足加工过程中数据传输的实时性与可靠性.     

三菱EDM的最新发展趋势

在电火花成形机方面 ,三菱的ＥＡ系列机床采用了最新的“动态技术”概念 ,使加工性能获得了一个飞跃。ＶＨ10超精密孔成形机则应用于精细和超精密加工。三菱的ＦＡ系列电火花线切割机 ,通过融合 6 4位ＣＮＣ技术和电源控制技术提供新的加工控制系统。在高精加工领域 ,商业化的第一台ＰＡ0 5超高精密电火花线切割机 ,可确保加工精度± 0 .0 0 2ｍｍ ,被广泛用于精密模具加工。1　电火花成形机的发展趋势1.1　集成控制的“ＤｙｎａＴｅｃｈ”(动态技术 )系统电火花加工是通过电极和工件间保持一个微小间隙而实现非接触加工的 ,它与接触加工截…     

数控精密微孔电火花加工机床燃油电喷片自动加工系统研究

针对数控精密微孔电火花加工机床研发设计了一种片式工件的自动上下料机构,是构成数控精密微孔电火花加工机床燃油电喷片自动加工系统的重要部分,实现了汽车发动机燃油电喷片的高效、低成本及自动化加工。     

基于遗传算法的工程陶瓷电火花加工技术

工程陶瓷材料硬脆、导电率低,难以获得高效精密的电加工效果.本文针对工程陶瓷电火花加工特点,在分析国内外工程陶瓷电火花加工技术的基础上,提出了基于遗传算法的工程陶瓷电火花加工方法.该方法结合遗传算法、神经网络及模糊控制理论构造了多环式自适应控制系统,在线对加工过程进行断丝预防、加工工艺自适应和加工参数自适应监测与控制,从而为难加工材料实现高效精密的电火花加工提供理论与技术指导.     

油泵油嘴复杂微结构微细电火花铣削加工试验

为解决油泵油嘴复杂微结构加工难题,开展了微细电火花铣削加工试验研究。在改进微细电火花加工机床系统的基础上,介绍了微细电火花铣削加工试验过程,并着重分析电极损耗补偿问题、加工效率问题的解决方法,进而完成油泵油嘴复杂微结构的精密微细电火花加工,总结出保证微细电火花铣削加工质量和加工效率的工艺规律。     

精密模具的大面积镜面加工技术

介绍了精密模具电火花镜面加工的意义及国内外电火花镜面加工的研究概况。在讨论电火花镜面加工机理的基础上 ,对镜面加工的工艺参数、加工设备、影响因素等问题进行了分析 ,并对精密模具电火花镜面加工的主要关键技术进行了讨论 ,包括镜面加工脉冲电源的设计、镜面加工电火花控制系统、电极和工件材料的影响因素、混粉工作液加工工艺等     

复杂型面的复合光整加工实验研究

利用电火花-超声和脉冲电化学复合加工工艺对三维复杂型面的光整加工进行了研究,论述了电火花超声复合加工的原理及超声装置的设计,进行了工艺参数实验研究,通过Master CAM软件实现型面的造型、编程,进行了三维型面的精密成形加工,经过脉冲电化学抛光后使型面达到镜面效果.     

Achieving high accuracy and high removal rate in micro-EDM by electrostatic induction feeding method

With conventional relaxation pulse generators used in micro-electrical discharge machining, due to the difficulty in keeping the minimum necessary discharge interval between pulse discharges, localized discharge and abnormal arc occur frequently. In contrast, with the newly developed electrostatic induction feeding method, only a single discharge occurs for each cycle of the periodic pulse voltage. As this realizes sufficient cooling of the discharge gap between pulses, thermal stress on the machined surface is less and duty factors can be increased, resulting in higher accuracy and machining speed compared to the relaxation pulse generator.     

微细电火花放电参数的高速采集

放电参数的实时快速采集是实现微细电火花放电状态准确辨识与控制的必要前提,由于微细电火花放电频率高,波形畸变严重,需对放电信号进行极速采集以获得完整的放电信息,还要进行数据同步分析以实现对放电状态的实时辨识.以高速数据采集卡和工控机为硬件基础,构建了微细电火花放电参数的高速数据采集与处理系统.采用VC 6.0编写实时采集程序,研究了分区式数据循环处理技术,解决了放电信号同步采集和处理的技术难题.试验表明该系统具有良好的实时性和准确性,能为信号辨识提供数据,为实现可靠的微细电火花加工控制提供了保证.     

A study on micro-hole machining of polycrystalline diamond by micro-electrical discharge machining

Polycrystalline diamond (PCD), with its superior wear and corrosion resistance, is an ideal material for micro-hole parts in the field of microfabrication. This study investigated the micro-hole machining performance for PCDs by micro-electrical discharge machining (micro-EDM). A series of experiments were carried out to investigate the proper machining polarity and the impacts of micro-EDM parameters on machining performance. Experimental results indicate that negative polarity machining is suitable for micro-EDM of PCDs because of the protection brought over by the adhesion sticking to the electrode. An appropriate volume of adhesion on the tool electrode can help to increase the material removal rate (MRR) and reduce the relative tool wear ratio (TWR). By contrast, an excessive volume of adhesion can lead the machining into a vicious circle in which micro-holes are drilled with overlarge diameters. An optimal set of machining conditions was chosen among the investigated ranges of nominal capacitance and electrode rotation speed. An exemplary PCD through-hole, machined under the chosen optimal machining conditions, shows satisfactory machining results.     

Characteristic evaluation of Al_2O_3/CNTs hybrid materials for micro-electrical discharge machining

The characteristic evaluation of aluminum oxide (Al2O3)/carbon nanotubes (CNTs) hybrid composites for micro-electrical discharge machining (EDM) was described. Alumina matrix composites reinforced with CNTs were fabricated by a catalytic chemical vapor deposition method. Al2O3 composites with different CNT concentrations were synthesized. The electrical characteristic of Al2O3/CNTs composites was examined. These composites were machined by the EDM process according to the various EDM parameters, and the cha...     

Material properties and machining performance of hybrid Ti2AlN bulk material for micro electrical discharge machining

Mn+1AXn(MAX) phases are a family of nanolaminated compounds that possess unique combination of typical ceramic properties and typical metallic properties.As a member of MAX phase,Ti2 AlN bulk materials are attractive for some high-temperature applications.The synthesis,characteristics and machining performance of hybrid Ti2 AlN bulk materials were focused on in this work.The bulk samples mainly consisting of Ti2 AlN MAX phase with density close to theoretic one were synthesized by a spark plasma sintering method.Scanning electron microscopy results indicate homogenous distribution of Ti2 AlN grains in the samples.Micro-hardness values are almost constant under different loads (6-6.5 GPa).A machining test was carried out to compare the effect of material properties on micro-electrical discharge machining (micro-EDM) performance for Ti2 AlN bulk samples and Ti6242 alloy.The machining performance of the Ti2 AlN sample is better than that of the Ti6242 alloy.The inherent mechanism was discussed by considering their electrical and thermal conductivity.`     

A new tool wear compensation method based on real-time estimation of material removal volume in micro-EDM

Owing to the reduced tool area and poor flushing conditions in deep holes, tool wear in micro-electrical discharge machining (EDM) is more significant than in macro-EDM. In micro-EDM drilling, the z-axis of the tool position is monitored as machining progresses. However, due to significant electrode wear, the machined hole depth is not identical to the programmed depth of the hole, and thus this will result in geometrical inaccuracy. This paper presents a new micro-EDM drilling method, in which the material removal volume is estimated as machining progresses. Compensation length is calculated and adjustment is made repeatedly along the tool path until the targeted material removal volume is reached. A real-time material removal volume estimator is developed based on the theoretical electro-thermal model, number of discharge pulse and pulse discrimination system. Under various energy input and machining depth settings, the experimental and estimated results are found to be in satisfactory agreement with average error lower than 14.3% for stainless steel, titanium, and nickel alloy work materials. The proposed drilling method can compensate the tool wear and produce more accurate micro-holes as compared to other methods. Experimental work also shows that the proposed method is more reliable as compared to the uniform wear method. In drilling micro-holes of 900 μm depth, the depth error can be reduced to 4% using the proposed method.     

Effect of micro-powder suspension and ultrasonic vibration of dielectric fluid in micro-EDM processes—Taguchi approach

Solutions are needed for increasing the material removal rate without degrading surface quality in micro-electrical discharge machining (μ-EDM). This paper presents a new method that consists of suspending micro-MoS₂ powder in dielectric fluid and using ultrasonic vibration during μ-EDM processes. The Taguchi method is adopted to ascertain the optimal process parameters to increase the material removal rate of dielectric fluid containing micro-powder in μ-EDM using a L₁₈ orthogonal array. Pareto analysis of variance is employed to analyze the four machining process parameters: ultrasonic vibration of the dielectric fluid, concentration of micro-powder, tool electrode materials, and workpiece materials. The results show that the introduction of MoS₂ micro-powder in dielectric fluid and using ultrasonic vibration significantly increase the material removal rate and improves surface quality by providing a flat surface free of black carbon spots.     

Servo scanning 3D micro-EDM based on macro/micro-dual-feed spindle

Using the end discharge of micro-rod-shaped electrode to scan layer by layer, micro-electrical discharge machining (EDM) can fabricate complex 3D micro-structures. During the machining process, the discharge state is broken frequently due to the wear of the tool electrode and the relative scanning motion. To keep a favorable discharge gap, the feed spindle of the tool electrode needs the characteristics of high-frequency response and high resolution. In this study, an experimental system with a macro/micro-dual-feed spindle was designed to improve the machining performance of servo scanning 3D micro-EDM (3D SSMEDM), which integrates an ultrasonic linear motor as the macro-drive and a piezoelectric (PZT) actuator as micro-feeding mechanism. Based on LabVIEW and Visual C++ software platform, a real-time control system was developed to control coordinately the dual-feed spindle to drive the tool electrode. The micro-feed motor controls the tool electrode to keep the favorable discharge gap, and the macro-drive motor realizes long working range by a macro/micro-feed conversion. The emphasis is paid on the process control of the 3D SSMEDM based on macro/micro-dual-feed spindle for higher machining accuracy and efficiency. A number of experiments were carried out to study the machining performance. According to the numerical control (NC) code, several typical 3D micro-structures have been machined on the P-doped silicon chips. Our study results show that the machining process is stable and the regular discharge ratio is higher. Based on our fundamental machining experiments, some better-machined effects have been gained as follows. By machining a micro-rectangle cavity (960 μm×660 μm), the machined depth error can be controlled within 2%, the XY dimensional error is within 1%, the surface roughness R_a reaches 0.37 μm, and the material removal rate is about 1.58×10⁴ μm³/s by using a tool electrode of Φ=100 μm in diameter. By machining multi-micro-triangle cavities (side length 700 μm), it is known that the machining repeatability error is <0.7%.     

Characteristic evaluation of Al2O3/CNTs hybrid materials for micro-electrical discharge machining

The characteristic evaluation of aluminum oxide (Al₂O₃)/carbon nanotubes (CNTs) hybrid composites for micro-electrical discharge machining (EDM) was described. Alumina matrix composites reinforced with CNTs were fabricated by a catalytic chemical vapor deposition method. Al₂O₃ composites with different CNT concentrations were synthesized. The electrical characteristic of Al₂O₃/CNTs composites was examined. These composites were machined by the EDM process according to the various EDM parameters, and the characteristics of machining were analyzed using field emission scanning electron microscope (FESEM). The electrical conductivity has a increasing tendency as the CNTs content is increased and has a critical point at 5% Al₂O₃ (volume fraction). In the machining accuracy, many tangles of CNT in Al₂O₃/CNTs composites cause violent spark. Thus, it causes the poor dimensional accuracy and circularity. The results show that conductivity of the materials and homogeneous distribution of CNTs in the matrix are important factors for micro-EDM of Al₂O₃/CNTs hybrid composites.     

Fabrication of deep micro-holes in reaction-bonded SiC by ultrasonic cavitation assisted micro-EDM

Ultrasonic vibration was applied to dielectric fluid by a probe-type vibrator to assist micro electrical discharge machining of deep micro-holes in ceramic materials. Changes of machined hole depth, hole geometry, surface topography, machining stability and tool material deposition under various machining conditions were investigated. Results show that ultrasonic vibration not only induces stirring effect, but also causes cloud cavitation effect which is helpful for removing debris and preventing tool material deposition on machined surface. The machining characteristics are strongly affected by the vibration amplitude, and the best machining performance is obtained when carbon nanofibers are added into the vibrated dielectric fluid. As test pieces, micro-holes having 10 μm level diameters and high aspect ratios (>20) were successfully fabricated on reaction-bonded silicon carbide in a few minutes. The hybrid EDM process combining ultrasonic cavitation and carbon nanofiber addition is demonstrated to be useful for fabricating microstructures on hard brittle ceramic materials.