EDM电极平动补偿系统的开发

研究了电火花成型加工中因电极平动所造成的加工误差 ,提出了基于NC技术的电极平动补偿方法 ,开发出EDM电极平动补偿软件系统 ,并进行了对比实验验证。实验表明 ,该系统可以有效提高EDM的加工精度     

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.     

电火花成型辅助设计与加工仿真系统的开发

研究了电火花成型（EDM）中因电极平动所造成的加工误差，提出了其于二维及三维的电极平动补偿方法，开发了以UG系统为平台的电极平动补偿及加工仿真系统，并进行了仿真对比实验。实验表明，该系统可以有效提高EDM电极设计的效率。     

Recast layer removal after electrical discharge machining via Taguchi analysis: A feasibility study

This study explores the feasibility of removing the recast layer (RCL) using etching and mechanical grinding for Ni-based superalloy materials by means of electrical discharge machining (EDM). The EDM process is widely used for machining hard metals and performing specific tasks that cannot be achieved using conventional techniques. The sparks produced during the EDM process melt the metal's surface, which then undergo ultra rapid quenching. A layer forms on the workpiece surface defined as a recast layer after solidification. Molds and dies desire to remove the RCL even though it is hard and has good matrix adherence.This experiment is divided into three stages. The first stage acquires a thick recast layer by using EDM with a larger discharging energy. A thick recast layer is essential for verification of the EDM technique for observing the recast process. Thus, this work applies the Taguchi L₁₈ analytical method to acquire the thick recast layer. The second stage optimizes the recast layer removal technique. Therefore, the thick recast layer is intentionally made in the first stage. This work determines the second stage setting using Taguchi's recommendation. Thus, the L₉ orthogonal array sets up the etching and mechanical grinding parameters and observes the recast layer removal quantity analysis. Finally, an experiment studies the surface characteristics of Ni-based superalloys, such as composition and micro-hardness after removing the recast layer.     

Fabrication of micro-electrodes by multi-EDM grinding process

In this study, a multi-EDM grinding process is adapted to fabricate micro-electrodes. Equipments such as a wire EDM machine and a traditional CNC-EDM machine are used for machining micro-electrodes. Rod electrodes of copper with diameter 3.0 mm were cut to be 0.15 mm on wire-EDM machine at first step. EDM grinding process was used to grind micro-electrodes to fine diameter bellow 20 μm on a CNC-EDM machine at second step. For EDM grinding, rotating mechanisms are mounted on both the WEDM machine and the CNC-EDM machine. A CCD camera is provided for viewing and for on-line dimensional controlling, when micro-electrodes were cutting. Fine electrodes could be processed to a smaller size using proposed two-steps EDM grinding process. Higher L/D ratio could be also achieved by this method. The processed fine electrodes can be used for drilling micro-holes, micro-deep holes, micro-milling, micro-punching, and manufacturing of micro-nozzles.     

Fabrication of YBCO films on Ag substrate by TFA-MOD method

Biaxial aligned YBCO films have been successfully deposited on Ag { 110 } (110) textured polycrystalline substrates by metal-organic decomposition (MOD) method using Trifluoroacetate Salt (TFA). The influence of firing temperature and Ag surface defects on phase purity and texture, surface morphology of YBCO films was studied. Holding temperature at 900℃ for 30 rain benefits to improve orientation and connectivity of YBCO films. The surface of YBCO films deposited on unpolished Ag substrate has many holes and stripes, which are parallel to the rolling stripe on Ag substrates. To eliminate the rolling stripe on the Ag surface, Ag substrates were polished prior to films deposition. The film grown on polished Ag substrates has a smooth surface and good connectivity of grains without parallel stripes. The YBCO films have an onset of transition around 90K and critical current densities of 15000 A/cm^2.     

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.     

新型电火花混粉镜面加工液处理工艺流程及装置的设计

提出将磁力液力旋流器用于电火花加工工作液中加工渣的分离处理，分析了国内外普通电火花加工和混有导电性粉末物质的电火花加工分离处理过程的现状和存在问题，介绍了新型电火花加工工作液工艺流程及处理装置的特点和结构设计。     

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     

Ultrasonic and electric discharge machining to deep and small hole on titanium alloy

Being a difficult-to-cut material, titanium alloy suffers poor machinability for most cutting process, let alone the drilling of small and deep holes using traditional machining methods. Although electric discharge machining (EDM) is suitable to handle titanium alloys, it is not ideal for small and deep holes due to titanium alloys’ low heating conductivity and high tenacity. This paper introduces ultrasonic vibration into micro-EDM and analyzes the effect of ultrasonic vibration on the EDM process. A four-axis EDM machine tool which combines ultrasonic and micro-EDM has been developed. A wire electric discharge grinding (WEDG) unit which can fabricate a micro-electrode on-line, as well as a measuring unit, is set up on this equipment. With a cylindrical tool electrode, made of hard carbide, which has high stiffness, a single-side notch was made along the electrode. Ultrasonic vibration is then introduced into the micro-EDM. Experiments have been carried out and results have shown that holes with a diameter of less than Ø0.2 mm and a depth/diameter ratio of more than 15 can be drilled steadily using this equipment and technology.     

基底对 TiNxOy太阳能选择性吸收薄膜性能的影响

采用磁控溅射法,分别在铜基、铝基上制备AlN/TiNxOy/Al多层膜,对比了该膜系与铜基和铝基的粘附性能,分析了与基底粘附性能的差异原因。采用二次阳极氧化方法使铝基底表面形成多孔微结构,再次镀多层膜,表征了膜系的表面形貌、光谱吸收性能和反射率,研究了微结构对薄膜性能的影响。结果表明:薄膜与铝基的粘附性较好,基底表面形成多孔微结构能有效提高其光谱吸收率。     

采用高频磁场去除太阳能级硅熔体中的SiC粒子(英文)

高质量硅材料在光伏太阳能和电子设备中具有重要应用,然而原料中的非金属颗粒和金属杂质严重影响其电学性能和力学性能。由于SiC粒子会降低光伏电池的力学性能并导致分流问题,因此在制备太阳能电池之前必须将这些杂质从硅材料中去除。利用磁场去除液态金属中的非金属杂质是制备高纯金属的一项尖端技术。利用该方法去除冶金级硅材料中的SiC粒子,并结合杂质去除经典模型和计算流体力学对熔体中粒子浓度和分离效率进行计算。为检验该方法的有效性,采用感应炉进行多次实验。结果表明:该方法能有效去除非金属杂质,提纯硅熔体,且实验结果与模型的预测结果相符。     

A review on the conventional and micro-electrodischarge machining of tungsten carbide

The capability of machining intricate features with high dimensional accuracy in hard and difficult-to-cut material has made electrodischarge machining (EDM) process as an inevitable and one of the most popular non-conventional machining processes. In recent years, both EDM and micro-EDM processes are being used extensively in the field of mould making, production of dies, cavities and complex 3D structures using difficult-to-cut tungsten carbide and its composites. The objective of this paper is to provide a state of the art in the field of EDM and micro-EDM of tungsten carbide and its composites. The review begins with a brief introduction on the EDM and micro-EDM processes. The research and developments in electrodischarge machining of tungsten carbide are grouped broadly into conventional EDM of tungsten carbide, micro-EDM of tungsten carbide and current research trends in EDM and micro-EDM of tungsten carbide. The problems and challenges in the area of conventional and micro-EDM of tungsten carbide and the importance of compound and hybrid machining processes are discussed. A summary of the future research directions based on the review is presented at the final section.     

超声振动磨削放电复合加工SiCp／Al试验研究

针对SiCp／Al的加工,提出一种超声振动磨削放电复合加工的方法．从加工效率、加工稳定性及表面质量等方面与电火花加工进行了对比试验研究。分析了两种加工方法的脉冲宽度和峰值电流对加工速度和表面粗糙度的影响,结果表明：电火花加工的表面粗糙度平均值为尺04．5μm,超声振动磨削放电复合加工的表面粗糙度平均值为Ra2μm：超声振动磨削放电复合加工的稳定性比电火花加工好,但加工速度较低。通过扫描电镜对两种加工方法下零件表面形貌和重熔层进行了观测,对试件表面进行了X射线衍射分析,表明采用超声振动磨削放电复合加工SiCp／Al复合材料可获得较好的表面质量。     

金属基底上IBAD-YSZ缓冲层的生长机理

用离子束辅助沉积(IBAD)方法,变换辅助离子束的能量和束流密度,在Hastelloy基底上制备了钇稳定氧化锆(YSZ)薄膜,作为涂层导体的缓冲层。XRD的结果显示:在一定的离子能量和束流密度的范围内,能够制备出高质量双轴织构的(001)取向的YSZ缓冲层,随着辅助离子束能量和束流密度的增大,IBAD-YSZ的面外取向和面内织构都出现先变好又变坏的现象。文中用辅助离子束对薄膜破坏程度的各向异性对结果做了解释。     

Anticorrosion properties of textured substrates made of copper–nickel-based ternary alloys

The tendency of some copper–nickel-based ternary alloys with additions of 3d transition metals, such as Cr, V, and Fe, to oxidation has been studied. The resistance to the oxidation was evaluated by the thermogravimetry method. It has been established that the strengthened textured tapes made of the Cu–40% Ni–1.2% Cr and Cu–40% Ni–1.4% Fe alloys have significantly better anticorrosive properties at 700°C than tapes made of pure copper and other investigated alloys, and can be used as substrates for epitaxial deposition of buffer and superconducting layers at elevated temperatures.     

Attempts to fabricate micro injection molding tools and assemble molded micro parts on same EDM machine

An EDM method for manufacturing plastic micro gear pumps is proposed. Micro gates and cavities for mating gears are machined by EDM in both sides of a stainless steel foil, respectively. The foil is then transferred to an injection molding machine, and fixed to a mold to form mating gears by injection molding. The mating gears formed on the foils are then re-positioned on the EDM machine, released from the foil, and placed in a second foil pre-machined by EDM for the pump housing, using an ejector pin fabricated by reshaping the tool electrode used to machine the two foils.     

Optimization of machining parameters in magnetic force assisted EDM based on Taguchi method

A versatile process of electrical discharge machining (EDM) using magnetic force assisted standard EDM machine has been developed. The effects of magnetic force on EDM machining characteristics were explored. Moreover, this work adopted an L18 orthogonal array based on Taguchi method to conduct a series of experiments, and statistically evaluated the experimental data by analysis of variance (ANOVA). The main machining parameters such as machining polarity (P), peak current (I_p), pulse duration (τ_p), high-voltage auxiliary current (I_H), no-load voltage (V) and servo reference voltage (S_v) were chosen to determine the EDM machining characteristics such as material removal rate (MRR) and surface roughness (SR). The benefits of magnetic force assisted EDM were confirmed from the analysis of discharge waveforms and from the micrograph observation of surface integrity. The experimental results show that the magnetic force assisted EDM has a higher MRR, a lower relative electrode wear ratio (REWR), and a smaller SR as compared with standard EDM. In addition, the significant machining parameters, and the optimal combination levels of machining parameters associated with MRR as well as SR were also drawn. Moreover, the contribution for expelling machining debris using the magnetic force assisted EDM would be proven to attain a high efficiency and high quality of surface integrity to meet the demand of modern industrial applications.     

A fuzzy pulse discriminating system for electrical discharge machining

In this paper, the use of fuzzy set theory to construct a new pulse discriminator in electrical discharge machining (EDM) is reported. The classification of various discharge pulses in EDM is based on the features of the measured gap voltage and gap current. To obtain optimal classification performance, a machine learning method based on a simulated annealing algorithm is adopted to automatically synthesize the membership functions of the fuzzy pulse discriminator. Experimental results have shown that EDM discharge pulses can be not only correctly but also quickly classified under varying cutting conditions using this approach.     

Textured tape substrates from binary copper alloys with vanadium and yttrium for the epitaxial deposition of buffer and superconducting layers

The structure of tapes of binary Cu–0.6 wt % V and Cu–1 wt % Y alloys and texturing process of them in the course of cold deformation by rolling to ~99% and subsequent recrystallizing annealing have been studied. The possibility of achieving the perfect cube texture in thin tapes made from binary copper-based alloys with vanadium and yttrium additions has in principle been shown. This opens the prospect of using them as substrates when manufacturing tapes of second-generation high-temperature superconductors. Optimum annealing conditions for the studied alloys have been determined, which have made it possible to produce the perfect biaxial texture with a content of cube {001}〈100〉 ± 10° grains on the surfaces of textured tapes of more than 95%.