电极结构对短电弧-电化学复合加工深窄槽影响研究

深窄槽结构具有尺寸小、深宽比较大的特点,狭小的加工区域存在排屑不畅、散热效果差等问题。为解决深窄槽加工过程中排屑困难的问题,提出通过优化电极结构来提升深窄槽短电弧-电化学复合加工的稳定性。分别设计单孔、多孔及螺旋3种管状电极结构,对不同电极结构加工时的间隙流场状态进行仿真研究。对比不同电极结构极间介质流速与压力的分布状态,并对仿真结果进行实验验证,探究电极结构对短电弧-电化学复合加工性能包括加工效率、尺寸精度、表面质量等指标的影响。实验结果表明：螺旋电极结构相比于单孔电极和多孔电极更能改善极间的流场状态,在保证深窄槽尺寸精度的情况下提高了加工效率与表面质量。     

High performance hybrid machining of γ-TiAl with blasting erosion arc machining and grinding

The excellent high temperature performance of gamma titanium aluminium (γ-TiAl) intermetallic not only makes itself a promising aero-engine material to replace Ni-based supperalloys but also poses machining challenges. A novel hybrid machining process namely blasting erosion arc grinding (BEAG) is proposed to process γ-TiAl. In this process, a creatively designed tool is implemented to perform high efficiency blasting erosion arc machining (BEAM) with an electrode and further polish the arc machined surface with the grinding part simultaneously. The experimental results illustrate that compared to BEAM and grinding, BEAG obtains a considerable material removal rate with a good surface quality.     

短电弧加工不同直径电极间隙流场研究

在短电弧加工过程中,利用流体软件Fluent对不同的电极直径加工间隙流场进行仿真,通过极间流场中的压力场与速度场间接得出加工屑排除的变化规律,并通过实验进行验证。结果发现:电极直径的增大可以促进加工屑从加工间隙排出,减少因间隙颗粒的堆积而产生的短路现象,从而避免“二次放电”;当加工深度不变时,电极直径的大小与工件材料的去除率呈正相关,证明短电弧加工过程中存在“面积效应”;电极直径的相对变化对工件表面质量没有明显的改善,即对表面粗糙度的影响不大。     

GT35钢结硬质合金电火花加工工艺试验

研究了GT35电火花加工时,峰值电流、脉冲宽度、放电时间等参数对工件加工效率、加工面粗糙度和电极耗损速度等的影响规律,并分析了其作用机理,优化了GT35钢结硬质合金电火花加工工艺参数,为加工复杂型腔GT35钢结硬质合金模具提供了试验依据。     

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.     

Surface modifications of Al–Zn–Mg alloy using combined EDM with ultrasonic machining and addition of TiC particles into the dielectric

This study proposes a novel combined process that integrates electrical discharge machining (EDM) and ultrasonic machining (USM) to investigate the machining performance and surface modification on Al–Zn–Mg alloy. In the experiment, TiC particles were added into the dielectric to explore the influence of the combined process on the material removal rate (MRR), the relative electrode wear ratio (REWR), the surface roughness and the expansion of the machined hole. The elemental distributions of titanium and carbon on the cross-section were quantitatively determined using an electron probe micro-analyzer (EPMA). Microhardness and wear resistance tests were conducted to evaluate the modifications on the machined surface caused by the combined process. The experimental results show that the combined process was associated with improved machining performance. The combination of EDM with USM yielded an alloyed layer that improved the hardness and wear resistance of the machined surface.     

The effect in EDM of a dielectric of a urea solution in water on modifying the surface of titanium

This study investigates the influence of the machining characteristics on pure titanium metals using an electrical discharge machining (EDM) with the addition of urea into distilled water. Additionally, the effects of urea addition on surface modification are also discussed. In the experiments, machining parameters such as the dielectric type, peak current and pulse duration were changed to explore their effects on machining performance, including the material removal rate, electrode wear rate and surface roughness. Moreover, the elemental distribution of nitrogen on the machined surface was qualitatively determined by EPMA to assess the effects on surface modification. Micro hardness and wear resistance tests were performed to evaluate the effects of the reinforced surface.Experimental results indicate that the nitrogen element decomposed from the dielectric that contained urea, migrated to the work piece, forming a TiN hard layer, resulting in good wear resistance of the machined surface after EDM.     

工艺参数对电火花电弧高效复合加工性能的影响研究

电火花电弧复合加工解决了电火花加工效率低的问题,与电火花加工相比,其加工效率提高了数倍,针对某些材料,其加工效率甚至超过了传统机械加工,但也存在自动化程度低、电极损耗严重等缺陷。利用电火花电弧复合加工技术进行了大量实验,并以此为基础,分析了不同加工参数下的工件性能,得到在不同峰值电流、脉宽、电极主轴转速等参数下的工件加工效率、表面粗糙度及相对电极损耗率的变化规律,以期得出针对不同加工目的的最优工作参数。     

绝缘陶瓷氮化硅高速走丝线切割加工技术研究

通过辅助电极利用高速走丝电火花线切割加工的方法对绝缘陶瓷氮化硅作了加工实验研究.介绍了辅助电极法绝缘陶瓷电火花线切割加工原理.通过调整加工电参数,研究了线切割加工氮化硅的加工特点,得出了较理想的加工参数,并对氮化硅线切割加工的去除方式作了初步研究.     

Diffusion Bonded EDM Electrode with Micro Holes for Jetting Dielectric Liquid

This paper describes improvement of machining characteristics of electrical discharge machining of deep slots using a tool electrode which has micro holes for jetting dielectric liquid over the working surface. The tool electrode was made by the diffusion bonding of two copper plates, over an interface on which micro grooves for jetting the dielectric fluid were formed using electrolyte jet machining. In conventional machining, it is difficult to drill micro holes at the end of a slim electrode and circulate the dielectric fluid from the other end. Hence a solid tool electrode is used and periodically lifted up during machining to flush debris particles out of the discharge gap. Use of the newly developed tool electrode was found to shorten the processing time and improve machining accuracy significantly compared with the conventional solid tool electrode. Since the holes are micro, the outlet shapes are not replicated onto the bottom surface of the slot machined.     

A study of three-dimensional shape machining with an ECμM system

This paper presents an electrochemical micromachining (ECμM) system developed with a machining gap control system. As a preliminary, electrochemical machining (ECM) experiments are carried out. The optimum machining condition of ECM is determined in terms of machining voltage, machining pulse length, amplitude of the electrode for flushing out contamination, and electrolyte concentration. After the preliminary ECM experiments, three-dimensional shape micromachining is carried out under the optimum condition. First, a prismatic electrode with a 200-μm square as the base shape is machined by ECM. Next, three-dimensional shape micromachining is carried out by scanning the prismatic electrode. A three-dimensional shape with sub-millimeter range is successfully machined.     

磨料流加工中夹具设计的研究

磨料流加工(AFM)是光整加工领域的一项新技术。磨料流加工由磨料流加工机床,夹具和流体磨料三部分组成。当用磨料流加工形状较复杂的零件时,夹具设计的好坏对表面加工质量和加工效率有重要的影响。本文分析了磨料通过工件孔道的特性。介绍了用于研究材料去除量与加工距离和形状关系的实验。材料去除量在通道两端比中间小是磨料流加工的一基本特性。本文讨论了如何避免因此而产生的工件变形以及如何利用这一特性来获取某种特殊效果。最后,给出了一个用于加工某不锈钢三通体的夹具。     

电火花摇动加工微细阵列轴和孔的试验研究

针对微细阵列轴和孔的电火花加工,提出了利用数控电火花加工机床摇动功能的摇动加工微细阵列轴和孔的方法.此法是基于电火花反拷贝加工的原理,先用丝电极在薄平板(中间电极)上按要加工的阵列轴和孔间距或数倍间距加工阵列小孔(直径0.1 mm以上),然后用加工的薄平板(中间电极)作电极,电火花摇动加工微细阵列轴(电极),最后用此微细阵列电极加工阵列孔.进行了电火花摇动加工微细阵列电极试验,得到了单电极直径为50 μm、长径比为16的3×3阵列电极,并用此电极在70 μm厚的不锈钢板上加工出单孔直径为70 μm的3×3微细阵列孔.试验结果表明,电火花摇动加工方法可实现微细阵列轴和孔的加工.     

内外冲液组合式的短电弧铣削加工间隙流场仿真

为进一步改善短电弧铣削加工间隙排屑情况,采用内外冲液组合式,通过Fluent对其进行仿真分析,得到了流场压力、速度和蚀除颗粒分布规律。分析不同冲液方式、冲液压力和电极转速对极间间隙流场特性的影响规律,并进行单因素试验。以MRR、TWR为评价指标,找出短电弧铣削加工性能的最佳参数。     

Effect of surface roughness of tool electrode materials in ECDM performance

Electrochemical discharge machining (ECDM) is an emerging non-traditional machining process that involves high-temperature melting assisted by accelerated chemical etching. In this study, the tool electrode (200 μm in diameter) is fabricated by wire electrical discharge grinding (WEDG). After the tool electrode is machined, the surface roughness of tool electrode materials (stainless steel, tungsten carbide, and tungsten) is different because of the physical properties. However, the surface roughness affects the wettability on tool electrode, and also changed the coalesce status of gas film in ECDM. Hence, this study explores the wettability and machining characteristics of different tool electrode materials and their impact on gas film formation. Their machining performance and extent of wear under gravity-feed micro-hole drilling are also examined. Experimental results show that the optimal voltage of different tool electrode can shed light on the machining performance. Moreover, wettability of tool electrode is determined by surface roughness of tool material, which in turn affects the coalesce status of gas film, machining stability and micro-hole diameter achieved. In addition, differences in tool material also results in variations in machining speed. Significant tool wear is observed after repeated gravity-feed machining of 50 micro-holes.     

W-Cu电极材料的短电弧铣削加工性能试验研究

为掌握短电弧铣削加工工艺规律,应尽可能控制其加工效果,实现高效率、低损耗的目的,基于系统的工艺试验研究,选择W-Cu、石墨作为工具电极,开展不同电极材料对工作介质注入、蚀除物抛出、电能利用率影响规律的短电弧铣削工艺试验,获取各工艺参数对MRR、TWR、表面形貌和金相组织等评价指标的影响规律,并进一步解释其规律成因,发挥短电弧高效加工硬质合金的优势。     

Trepanning of Al2O3 by electro-chemical discharge machining (ECDM) process using abrasive electrode with pulsed DC supply

Electro-chemical discharge machining (ECDM) of electrically non-conductive high-strength–high-temperature-resistant ceramics such as aluminium oxide (Al₂O₃) by trepanning method (i.e. orbital motion of tool) has shown the possibility of drilling large size holes by comparatively smaller electrodes efficiently and economically. However, at greater machined depth, the conventional electrode configurations and machining parameters show that machining performance gradually deteriorates with increase in tool depth and finally cause micro cracks on the machined surface due to thermal shocks at high voltage. To reduce this problem and to enhance the machining performance during trepanning operation of Al₂O₃, a spring fed cylindrical abrasive electrode of 1.5 mm diameter has been used under the effect of the three most influential parameters, namely, pulsed DC supply voltage, duty factor and electrolyte conductivity, each at five different levels to assess the volume of material removed, machined depth and diameteral overcut. The results obtained from this study revealed that pulsed DC has reduced the tendency of cracking at high supply voltage compared to smooth DC and the machining ability of the abrasive electrode was better than copper electrode as it would enhance the cutting ability due to the presence of abrasive grains during machining. In addition to this, trepanning provides the scope for drilling bigger holes.     

A study of EDM and ECM/ECM-lapping complex machining technology

EDM (electrodischarge machining) and ECM (electrochemical machining)/ECM-lapping complex machining is investigated in this paper. First, EDM shaping and ECM finishing technology are investigated. These processes are carried out in sequence on the same machine tool with the same electrode (copper) and the same machining liquid (water). Two types of EDM and ECM complex machining are investigated. One is with a formed electrode, and the other is with simple-shape electrode scanning. The complex machining with electrode scanning is applied to produce small and various-shaped components without making a formed electrode. The EDM surface of 1 μm Ra is improved to 0.2 μm Ra by applying ECM. Second, in order to get a smoother surface, a new EDM and ECM-lapping complex machining technology is developed. The surface roughness of a machined hole is improved to 0.07 μm Ra by applying 2 min of ECM lapping. The surface finishing of a hole shape is demonstrated with the complex machining technology.     

燃气弯管弧面结构电解铣削加工特性研究

液氧煤油火箭发动机燃气弯管具有尺寸较大、形状特殊的三维空间弧面结构,利用传统拷贝式电解加工技术难以获得理想的加工形貌.针对弧面结构燃气弯管的加工难点,研究采用电解铣削技术进行加工,基于新一代液氧煤油火箭发动机燃气弯管的尺寸等比缩小样件,试验了具有弧面结构的316L不锈钢在NaCl溶液中不同工艺参数下的电解铣削加工特性....     

Optimization of the WEDM process of particle-reinforced material with multiple performance characteristics using grey relational analysis

This paper presents an effective approach for the optimization of the wire electric discharge machining (WEDM) process of Al₂O₃ particle-reinforced material (6061 alloy) with multiple performance characteristics based on the grey relational analysis. The machining information for the difficult-cutting particle-reinforced material is inadequate and complicated. The response table and response graph for each level of the machining parameters are obtained form the grey relational grade, and select the optimal levels of machining parameters. In this study, the machining parameters namely the cutting radius of working piece, the on time of discharging, the off time of discharging, the arc on time of discharging, the arc off time of discharging, the servo voltage, the wire feed and water flow are optimized with considerations of multiple performance characteristics, such as the surface removal rate and the maximum surface roughness. It is clearly shown that the above performance characteristics in the WEDM process are great improved together through this approach.