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。     

功能梯度材料微细电火花电极损耗机理研究

论述了功能梯度材料Ni-TiN/Cu微细电火花电极的制备方法,并用实验的方法研究功能梯度材料层在电火花微细加工对电极损耗的影响。Ni-TiN/Cu微细电火花电极通过在圆柱铜电极外侧电沉积功能梯度材料层来制备,纳米颗粒TiN做为增强相。通过使用SEM分析功能梯度材料层的显微组织,使用光学显微镜测量电极加工孔质量与电极损耗情况,对比功能梯度材料电极与均质电极的电火花加工性能。在微细电火花加工中,功能梯度材料层可以有效的抑制高频脉冲条件下电极的损耗效应,改善电流密度分布,从根本上解决因尖端放电引起的电极形状变化问题,实现端面等损耗,保证了微细电火花加工电极的形状精度。实验结果验证了功能梯度材料作为工具电极在微细电火花加工应用的前景。     

电铸工艺对工具电极材料抗电蚀性能的影响研究

提升基于准LIGA工艺制作的微细电火花加工工具电极材料的耐电蚀能力,是准LIGAMicroEDM组合加工高深宽比三维微结构可靠实现的重要研究内容。论述了该组合加工的技术优势及其工艺路线,理论分析了电铸电极材料电蚀性的影响因素,试验研究了电沉积工艺参数和操作条件如添加剂种类及其添加量、电流密度、温度等对电铸铜工具电极电蚀能力的影响。结果表明,组合添加适量明胶和Cl-,在适当的电流密度和温度等工作条件下,电铸出的铜工具电极在微细电火花加工中表现出超强的耐电蚀能力,重量相对损耗为0.3%。     

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。     

微细电极凹底损耗的影响因素分析

微细电火花铣削是实现金属微结构加工最具潜力的加工方法之一,而电极形状损耗一直制约着该技术的工程化应用,找出电极形状变化规律,实现电极形状损耗的控制是解决该问题的根本途径.在现有的研究成果基础上,针对微细电极凹底损耗现象进行深入研究:设计正交实验提炼凹底损耗的主要影响因素;在正交实验的基础上,运用响应曲面设计建立凹底损耗...     

利用小直径电极的电火花微细轮廓加工

近年来,随着微细加工技术的发展,开发出各种不同的加工方法。有的有希望用来制造微型机器和医疗器械用的零件。就亚微米尺寸加工而言,目前,虽然溅射和蚀剂等加工方法在半导体制造方面占主流,但不适于复杂3维形状的加工。在此之前,电火花微孔加工已显示出高精度加工的效果。以往还曾利用圆柱形电极在低损耗条件下进行过轮廓加工。然而,当采用微小直径电极加工时,由于电极损耗大幅度增加,使电极瑞部棱角产生圆弧R,因而不能实现高精度加工。与上述情况相比,日本三菱公司却积极地利用电极损耗来保持加工底面的棱角,以谋求实现高精度微细形状的加工。一、简单电极轮廓加工原理微细轮廓电火花加工,主要采用微小直径的管状电极,使其在旋转状态下进行加工,以实现所要求的加工轮廓(图1)。在以往,主要是借助于圆柱状电极的侧面来进行轮廓加工见,如图2(a)所示,而微细轮廓加工则利用电极的底面,边反     

电火花微细孔加工电极损耗实验研究

用实验的方法研究电火花微细加工中放电能量在极间的分配和对电极损耗的影响，并研究式具电极材料和工件材料对电极损耗的影响，实验表明，从减小电极损耗，增加有用功率出发，电火花微细加工应使用微能窄脉冲电源。     

微细电火花加工中电极损耗机理的研究

微细电火花加工中,因电极损耗引起的电极尺寸和形状的变化严重影响被加工工件的尺寸精度和形状精度。在实验基础上分析了电极损耗的变化过程,并借助有限元方法和电磁理论研究了产生电极损耗的机理。研究表明：电场集中是棱边损耗的根本原因,一定阶段后电极形状趋于稳定;击穿放电产生的超高频电流使电极横截面上的电流在边缘的集中是发生二次放电的主要根源。     

一种三轴联动微细电火花加工装置的研制

1.微细电火花的加工原理及特点 微细电火花加工的原理与普通电火花加工并无本质区别。其加工的表面质量主要取决于电蚀凹坑的大小和深度,即单个放电脉冲的能量;而其加工精度则与放电间隙、工艺系统稳定性、电极损耗等     

Al_2O_3/Cu复合电极电火花小孔加工机理及试验研究

在电火花小孔加工中,采用普通铜管电极加工后,孔的圆柱度差,出现锥孔、工具电极端部变钝等现象。主要原因是由于电蚀产物在加工侧隙的二次放电造成的。普通铜管电极表面喷涂Al2O3陶瓷材料,可以有效的降低二次放电的发生,提高加工质量。采用Al2O3/Cu复合电极和普通铜管电极,在D703F电火花小孔机床进行加工。在不同的脉冲宽度和脉冲电流下,使用两种电极对同一工件进行加工。实验结果表明,与普通铜管电极相比,复合电极相对损耗降低30%,孔和工具电极锥度减小,提高了孔的形状公差等级。     

Towards the effective tool wear control in micro-EDM milling

The electrode wear in micro-electrical discharge milling (micro-EDM milling) is one of the main problems to be solved in order to improve machining accuracy. This paper presents an investigation on wear and material removal in micro-EDM milling for selected process parameter combinations typical of rough and finish machining of micro-features in steel. The experiments were performed on state-of-the-art micro-EDM equipment. Based on discharge counting and volume measurements, electrode wear per discharge and material removal per discharge were measured for several energy levels. The influence of the accuracy of volume measurements on the electrode wear per discharge and on the material removal per discharge are discussed, and the issues limiting the applicability of real time wear sensing in micro-EDM milling are presented.     

Workpiece and electrode influence on micro-EDM drilling performance

In recent years, the need for products containing micro-features has shown a pronounced and steady growth in several fields of application. For the development of micro-holed devices, one of the most important technologies is micro-EDM (Electro Discharge Machining). Micro-EDM can be considered as an ideal process to obtain burr-free micron-size features with high aspect ratios. In particular, micro-EDM is a non-contact material removal process in which rapid electric spark discharges remove the material composing the workpiece by means of melting and vaporizing phenomena. The present work deals with the fabrication of micro holes using micro-EDM technology. The investigation focuses on the influence of different electrodes and workpiece materials on the process performance, expressed in terms of tool wear ratio. In particular, the influence of four different workpiece materials (stainless steel, titanium, magnesium and brass), three electrode materials (copper, brass and tungsten carbide) and two different electrode shapes (cylindrical and tubular) was investigated. Moreover, an analysis of the geometrical characteristics of the micro holes in terms of conicity and diametrical overcut was carried out. An influence of electrode geometries, electrode material and workpiece material on the final output was found.     

铝基碳化硅异形电极电火花加工技术研究

为了改善电火花深小孔加工过程中,因加工碎屑排出不畅而导致的加工速度慢、电极损耗严重等问题,制备螺旋、三沟槽和削边三种形貌的异形结构电极。在相同的加工条件下,以铝基碳化硅为实验材料,采用异形结构电极与圆柱电极分别进行不同深度下深小孔加工实验,对加工效率、电极损耗和深小孔内表面形貌三方面进行对比分析。实验结果表明:异形结构电极在深小孔的加工效率和电极损耗方面都优于圆柱电极;小孔内表面形貌方面:圆柱电极加工后的孔内表面附着碎屑较多。     

EXPERIMENTAL INVESTIGATIONS INTO THE INFLUENCE OF MAJOR OPERATING PARAMETERS DURING MICRO-ELECTRO DISCHARGE DRILLING OF CEMENTED CARBIDE

Present study investigates the influence of major operating parameters on the performance of micro-EDM drilling of cemented carbide (WC-10wt%Co) and identifies the ideal values for improved performance. The operating parameters studied were electrode polarity, gap voltage, resistance, peak current, pulse duration, pulse interval, duty ratio, electrode rotational speed and EDM speed. The performance of micro-EDM drilling process was evaluated by machining time, material removal rate (MRR), relative electrode wear ratio (RWR), spark gap, surface finish and dimensional accuracy of micro-holes. It has been found that there are two major conflicting issues in the micro-EDM of carbide. If the primary objective is to obtain better surface finish, it can be obtained by the sacrifice of high machining time, low MRR and high RWR. However, for faster micro-EDM, the surface roughness is higher and electrode wear is again much higher. It is concluded that negative electrode polarity, gap voltage of 120 V, resistance of 33 Ω, peak current of 8 A, pulse duration of 21 μs, pulse interval of 30 μs, duty cycle of 0.47, electrode rotational speed of 700 rpm and EDM speed of 10 μm/s can be considered as ideal parameters to provide improved performances during the micro-EDM of WC-Co.     

A study on electrode wear sensing and compensation in Micro-EDM using machine vision system

This paper presents an electrode wear compensation method based on a machine vision system for micro-electro-discharge machining (EDM). Front wear and corner wear of tool electrode can be measured and evaluated in a direct manner by the vision system’s image-processing software capabilities. Tool electrode images have depicted that the front wear and corner wear were increased rapidly during EDM drilling and EDM milling, respectively, and thus contributing to an arc and a tapering shape at the end of tool electrode, respectively. Both the depth of the hole and depth of the groove are linearly proportional to the length of the front wear. A new electrode wear compensation method is presented based on the direct measurement of the front wear. Experimental results not only verify the usefulness of the electrode wear compensation method in micro-EDM, they also demonstrate that the machining time can be significantly reduced by 40% when using the proposed method, compared to the uniform wear method.     

Process planning and electrode wear compensation for 3D micro-EDM

This paper presents a novel multi-cut process planning method and a new electrode wear compensation method based on a machine vision system for three-dimensional (3D) micro-electrical discharge machining (micro-EDM). Front wear and corner wear of tool electrode can be measured and compensated in a direct manner by the vision system??s image processing software capabilities. Experiments have shown that corner wear ratio (defined as a ratio between the length of corner wear and electrode diameter) is linearly proportional to machining length under a fixed machining depth condition. Track overlapping between the two adjoining paths is designed appropriately according to the corner wear ratio. Experimental results not only indicate that the proposed multi-cut process planning and electrode wear compensation methods can significantly improve machining accuracy and reduce machining time for the micro-EDM process, they also demonstrate that the X?CY dimensional errors of micro-structures can be controlled within 10???m.     

An experimental study on micro-EDM in low-resistivity deionized water using short voltage pulses

Deionized water has been used as dielectric fluid for micro-electrical discharge machining (micro-EDM) because it gives higher material removal rate and lower tool wear than hydrocarbon oil. Moreover, it is a relatively low-cost and eco-friendly substance. Therefore, deionized water tends to be more favorable for micro-EDM. However, it causes weak electrochemical reaction during micro-EDM due to its slight conductivity. This leads to the unanticipated additional material removal from the workpiece which affects the machining shape and quality. The study in this paper aims to suppress the electrochemical reaction in die-sinking micro-EDM using deionized water by employing short voltage pulse. Experiments were carried out to fabricate micro-holes using the developed nanosecond pulse circuit. Different pulse parameters were applied to identify the main factor affecting the electrochemical reaction rate. Machining gap was found to be thinner and workpiece surface adjacent to the rim of micro-holes were found to be free of defects caused by material dissolution when pulse duration reached a critical value. Moreover, the influence of pulse parameters on material removal rate and machined shape was also investigated. Besides, energy-dispersive X-ray spectroscopy analysis showed that the machined surface using deionized water was less affected from material migration during micro-EDM process in comparison to hydrocarbon oil.     

Experimental study on micro EDM-drilling of Ti6Al4V using helical electrode

There is a growing interest in the machining of micro-holes with high aspect-ratio in difficult-to-machine alloys for the aerospace industry. Processes based on electro discharge machining (EDM) and developed for the manufacture of both micro-electrode and micro-hole are actually used, but most of them involve micro-EDM machines. In this work, the influence of EDM parameters on material removal rate, electrode wear, machining time and micro-hole quality when machining Ti6Al4V is studied. Due to an inefficient removal of debris when increasing hole depth, a new strategy based on the use of helical-shaped electrodes has been proposed. The influence of helix angle and flute depth with respect to process performance has been addressed. Main results include 37% reduction in machining times (hole diameter 800 μm) when using electrode helix angle of 45° and flute-depth of 50 μm, and an additional 19% with flute-depth of 150 μm. Holes of 661 μm diameter and as much as 6.81 mm depth, which yields in aspect ratio of 10:1, have successfully been machined in Ti6Al4V.     

高回转精度多阶柱状微电极电化学高效制备试验研究

为实现高回转精度多阶柱状微电极的高效加工,对多阶柱状电极电化学刻蚀过程进行了深入的研究与改进。首先,根据电化学刻蚀理论推导了加工电流对电极直径变化的影响规律;通过试验证明了电极旋转可提高电流变化速率及有效起始电流进而提高加工效率,定性分析了电极旋转对电极回转精度的影响,提出了分阶变转速高效加工高回转精度多阶柱状微电极的方法;通过试验分析了各加工参数(电极转速、加工电压和切断电流)对电极形状及尺寸的影响;最后,在优化后的加工参数下,成功加工得到末端直径小于15μm且同轴度误差在1μm以内的多阶柱状微电极,与常规电化学刻蚀工艺相比,显著提高了加工效率。试验证明旋转电化学刻蚀是一种能够较好地提高微电极加工效率及回转精度的新工艺。     

Process performance of micro-EDM drilling of stainless steel

An experimental campaign based on the execution of through micro-holes on stainless steel plates was carried out using a micro-EDM machine Sarix SX-200. The experimental campaign was carried out by varying several process parameters, namely peak current, voltage and frequency. Tubular electrodes made of two different materials (tungsten carbide and brass) were used. A study of the in progress material removal rate (MRR) and tool wear ratio (TWR) during the drilling process was performed. Some mathematical laws governing the relation between process parameters and performance indexes were defined. Two technological windows representing TWR and MRR as a function of the hole depth, for different electrode materials, were obtained.