微细电火花加工技术及其应用

介绍了微细电火花加工技术的原理、特点及最新研究成果，简述了微细电火花加工技术的应用及发展趋势。     

微细电加工应用技术研究

微细电加工要达到工业应用的目的,需兼顾加工效率和加工精度两方面的要求.以微细孔、微细三维结构的加工为目标,进行了微细孔电火花加工、三维微细结构电火花伺服扫描加工及微细电化学加工技术的研究开发.设计出微细电极的损耗补偿进给和导向机构,开发出三维微细结构的电火花伺服扫描加工工艺,研究了采用阵列微细电极的微细电化学加工方法.微细孔电火花加工可连续加工直径小至100 μm的孔.伺服扫描电火花加工可便捷地在小于1 mm2区域内加工出三维微细结构.提出的微细电化学加工技术路线拟将微细电解加工应用于阵列微细孔和三维微细结构的加工.     

微细电火花加工实现条件的研究

介绍了微细电火花加工的原理和特点,从加工表面质量、脉冲电源、微细工具电极的制造和安装、放电面积效应的影响、伺服控制系统等方面对微细电火花加工的实现条件进行了研究,并给出了微细轴的电火花加工等具体加工实例.研究结果对微细电火花加工技术的具体应用具有重要的参考价值和指导意义.     

喷油器流量控制阀板精密复杂微结构微细电火花加工技术

阐述了共轨喷油器流量控制阀板复杂微结构微细电火花加工解决方案,介绍了研制的三头数控微细电火花加工装备,分析了微细电火花铣电极损耗补偿及锥度沟槽、十字槽等加工工艺,总结出保证微细电火花铣削加工质量和效率的工艺规律。     

微细电火花加工技术在组合加工中的应用

概述并分析了微细电火花加工技术的发展现状及遇到的问题.介绍了微细电火花加工技术与其他微细加工技术相互组合,完成微小零件制造的各种工艺方法.     

分层去除微细电火花铣削技术的实验研究

系统地研究了微细电火花铣削的工艺规律，提出了超声辅助微细电火花铣削加工技术。该技术能显著改善微细电火花铣削时的放电状态，提高加工效率。     

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.     

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.     

基于SOPC技术的微细电火花加工电源的研究

针对目前微细电火花加工放电状态复杂、难确定和集成性不足等问题,设计了基于可编程片上系统(SOPC)技术的微细电火花脉冲电源。电源可发送加工脉冲信号,采用并行数字采集信号模块采集电压及电流信号,能判断每个脉冲的放电状态,控制伺服电机的工作,并及时切断无效有害脉冲,提高加工效率和加工精度。同时开发了电源人机交互界面,实现了电源和微细电火花加工机床的实时通讯功能。利用该电源在自主开发的多功能微细加工机床上进行微细孔加工实验,证明了所设计的电源能进行稳定高效的加工。     

微细阵列型孔的冲压与电火花复合加工技术研究

提出一种微细冲压加工和微细电火花加工交叉结合的微细阵列型孔复合加工方法。尺寸较大的过渡型腔采用微细冲压加工，以提高加工效率和保证加工尺寸的一致性；型孔喷口的最小特征尺寸采用微细电火花逐层扫描加工得到。设计制作了专用的微小型腔冲压实验装置，从机构设计上保证加工工艺对微小型腔冲压深度的精确控制。进行了非圆截面阵列微细型孔的加工实验，验证了所提出的工艺方法的可行性和合理性。     

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.     

微细电火花加工用脉冲电源技术的基础研究

在微细电火花加工中，使用RC放电回路容易得到数十至数百纳秒的窄脉宽电流，但RC放电回路由于向电容器充电所需时间而不能得到很高的放电频度，严重影响其加工效率。为此，本研究开发了微细电火花加工用晶体管式脉冲电源，并对其加工特性进行了评价，找出了适合于微细电火花加工的晶体管式脉冲电源。实验结果表明，自振式晶体管脉冲电源因其加工速度慢并不适于微细放电加工。通过开发等脉宽晶体管脉冲电源，可实现脉宽80ns的放电电流，与传统的RC放电回路相比，加工速度可提高2至3倍。     

Application of micro-EDM combined with high-frequency dither grinding to micro-hole machining

This research presents a novel process using micro electro-discharge machining (micro-EDM) combined with high-frequency dither grinding (HFDG) to improve the surface roughness of micro-holes. Micro-EDM is a well-established machining option for manufacturing geometrically complex small parts (diameter under 100 μm) of hard or super-tough materials. However, micro-EDM causes the recast layer formed on the machined surface to become covered with discharge craters and micro-cracks, resulting in poor surface quality. This affects the diameter of the micro-hole machined and undermines seriously the precision of the geometric shape. The proposed method that combines micro-EDM process with HFDG is applied to machining high-nickel alloy. As observed in SEM photographs and surface roughness measurement, HFDG method can reduce surface roughness from 2.12 to 0.85 μm Rmax with micro-cracks eliminated. Our results demonstrated that micro-holes fabricated by micro-EDM at peak current 500 mA followed by HFDG at 40 V can achieve precise shape and good surface quality after 6–8 min of lapping.     

基于VC的压电自适应微细电火花加工软件研究

对压电自适应微细电火花加工平台及原理进行了介绍,并针对该平台研究了数控加工的实现方法,利用VC++2010编程工具结合Windows下的多线程和串口编程技术开发了专用的数控加工软件,并进行了加工实验,结果表明开发的加工软件满足压电自适应微细电火花加工要求,具有一定的实用性.     

单层多道微细电火花定长补偿加工方法

定长补偿是应用分层原理进行微细电火花加工的一种方法,它能较好地解决加工中电极损耗对精度的影响问题.通过实验证明了微细电火花铣削加工中由于底面和侧面放电间隙不同,在加工过程中要区别对待;根据实验结果建立了实际加工后单道的横截面模型,在此基础上引入了体积系数、面积系数、残切系数,对原来的定长补偿方法进行了修正.根据建立的实际加工后残切模型,给出2种典型去除残切的加工工艺路线,应用定长补偿方法解决了分层三维构件加工中的单层加工问题.     

Study of the Diffusion of Carbon, Its Sources, and Effect on Finishing Micro-EDM Performance of Cemented Carbide

Apart from the necessity of surface modification based on different applications, in most of the cases, diffusion of carbon or foreign particles on the workpiece surface during micro-electrodischarge machining (micro-EDM) is avoidable, especially in finishing micro-EDM. This study aims to investigate different sources of materials that migrate to the machined surface during fine-finishing of micro-EDM of cemented tungsten carbide (WC-Co). The machined surfaces have been examined under scanning electron microscope and energy dispersive x-ray to investigate the changes in chemical composition. It has been observed that during finishing of micro-EDM, the major source of materials' transfer to both the workpiece and electrode is the diffusion of carbon that comes from the decomposition of the hydrocarbon dielectric. In addition, materials from both workpiece and electrode transfer to each other based on machining conditions and discharge energy. The migration occurs more frequently at lower gap voltages during die-sinking with micro-EDM because of low spark gap and stationary tool electrode. Milling micro-EDM results in lower amount of carbon migration and fewer surface defects that improve the overall surface finish significantly.     

A study on the quality micro-hole machining of tungsten carbide by micro-EDM process using transistor and RC-type pulse generator

Tungsten carbide (WC) is an extremely hard and difficult-to-cut material used extensively in manufacturing because of its superior wear and corrosion resistance. Besides diamond-charged grinding wheels, micro-EDM is an effective method of machining this extremely hard and brittle material. Since micro-EDM is more generally an electro-thermal process, the supplied energy from a pulse generator is an important factor determining the performance of the micro-EDM process. This study investigates the influence of major operating parameters on the performance of micro-EDM of WC with focus in obtaining quality micro-holes in both transistor and RC-type generators. Experimental investigations were conducted with view of obtaining high-quality micro-holes in WC with small spark gap, better dimensional accuracy, good surface finish and circularity. In micro-EDM, the fabrication of micro-parts requires minimization of the pulse energy supplied into the gap which can be fulfilled using the RC-generator. It was observed that the RC-generator can produce better quality micro-holes in WC, with rim free of burr-like recast layer, good dimensional accuracy and fine circularity. Moreover, the smaller debris formed due to low discharge energy in RC-type micro-EDM can be easily flushed away from the machined area resulting in surface free of burr and resolidified molten metal. Therefore, RC-type micro-EDM could be more suitable for fabricating micro-structures in WC, where accuracy and surface finish are of prime importance.     

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.     

A multiprocess machine tool for compound micromachining

Compound micromachining is the most promising technology for the production of miniaturized parts and this technology is becoming increasingly more important and popular because of a growing demand for industrial products, with an increased number not only of functions but also of reduced dimensions, higher dimensional accuracy and better surface finish. Compound micromachining processes that combine multiple conventional and non-conventional micromachining processes have the capability to fabricate high aspect ratio microstructures with paramount dimensional accuracy. Such machining should be carried out on the same machine with minimum change of setups. At the same time, on-machine tool fabrication along with on-machine tool and workpiece measurement facilities should also be available for further enhancement of the functionality of the machine and higher productivity. In order to achieve effective implementation of compound micromachining techniques, this research seeks to address four important areas, namely (a) development of a machine tool capable of both conventional micromachining including microturning, micromilling, etc., and non-conventional micromachining including microelectrical discharge machining (micro-EDM), wire-cut electrical discharge machining (WEDM), etc.; (b) process control; (c) process development to achieve the necessary accuracy and quality and (d) on-machine measurement and inspection. An integrated effort into these areas has resulted in successful fabrication of microstructures that are able to meet the miniaturization demands of the industry. This paper presents a few tool-based approaches that integrate micro-EDM, micro-EDG, microturning and microgrinding to produce miniature components on the same machine tool platform in order to demonstrate the capabilities of compound micromachining.     

微细电火花加工及表面重铸层电解去除装置的设计

微细电火花加工工件表面的重铸层影响加工精度和使用性能,为此设计了具有微细电火花加工及电解去除表面重铸层功能的集成装置。该装置由运动平台、伺服控制、脉冲电源等关键部分组成,集成了微细电火花和微细电解加工功能。针对不同加工方法采用不同的控制策略,解决了微细电火花加工与电解加工在同一设备上的集成问题。通过实验验证,该装置可以很好地实现微细电火花加工表面重铸层的在线去除,且去除厚度可通过改变加工参数的形式来控制。