侧壁绝缘电极的微槽电化学放电加工特性研究

在电化学放电加工中,电极浸没在溶液中的部分均会发生放电,其中侧壁区域的放电会对微槽加工产生不利影响,破坏加工表面质量。针对该问题,提出了一种金刚石涂层侧壁绝缘电极,分析了其电流-电压曲线特性,并进行了微槽加工实验。通过与传统电极比较,发现电极侧壁绝缘后,其临界电压增大、临界电流减小。在微槽加工中,侧壁绝缘电极能有效提高加工精度和加工表面质量,故在高质量微槽加工中具有良好的应用前景。     

热障涂层冲蚀后的电火花制孔试验研究

电火花加工方法不能直接加工涂覆了热障涂层的高温合金构件。先利用磨料水射流冲蚀去除高温合金表面的热障涂层,形成涂层孔型,再利用电火花加工方法进行金属基体的微小孔加工。涂层孔型底部的金属基体裸露率对后续电火花加工可行性有重要影响。结果表明:电火花加工可行性与金属基体裸露率、残余涂层材料厚度均有很大的关联;在残余涂层材料与金属表面高度差小于理想放电间隙的情况下,金属裸露面积的增加使电火花放电面积和单位时间内的放电能量均增加,可蚀除或剥落更多的残余涂层材料,有助于电火花加工顺利进行;在特定电火花加工条件下,保证金属裸露率达到一定的阈值是实现磨料水射流与电火花组合制孔的必要条件。     

两种基体材料的脉冲放电强化层对比研究

从强化层的厚度、硬度、结构及强化层与基体之间的扩散程度方面对Ｍ２和５０ＣｒＭｏＶ两种基体脉冲放电强化层进行了对比研究。结果表明,两种基体材料强化层的特点、性能等方面明显不同;电极材料主要相在放电形成涂层中发生变化。     

镁合金构件的微弧修复和组织研究

针对镁合金构件缺陷进行电火花微弧修复,研究了不同电压和放电频率下的修复质量。结果表明:放电频率对镁合金构件表面粗糙度的影响较小。当电火花堆焊的脉冲频率与电压分别为200 Hz和35 V时,修复层结合质量好、涂层均匀性好、致密程度高。     

基于润湿供液的电化学放电线切割实验研究

针对非导电硬脆材料的微细线切割加工,设计并搭建了基于润湿供液的电化学放电线切割装置,实现了对石英材料的有效切割,确定了实现电化学放电线切割加工的临界电压。通过提取加工过程中能反映极间状态的电流信号作为控制加工的依据,实现了对石英材料的可控加工,实验表明加工速率及槽宽随着电压的增加而增大。通过对工件步进进给和匀速进给两种加工方式的比较表明,利用电流信号作为进给控制依据进行步进进给能更好地保证加工的连续性。     

电化学放电加工电压-电流特性的研究

电化学放电加工机理主要是火花放电的热蚀与高温下化学腐蚀的共同作用.加工过程中状态信息的及时获取对电化学放电加工的精确控制具有重要意义.通过对电化学放电加工过程中电压-电流特性的研究,用实验结果分析了电压-电流与工具电极反应面积之间的关系,得出与工具电极反应面积匹配的最佳电压,为电流信号成为电化学放电加工监视信号提供了理论基础.     

电化学放电线切割电压-电流特性研究

设计并搭建了基于水平走丝方式的电化学放电线切割加工装置,可用于非导电硬脆材料的微细线切割加工,研究了加工过程中的电压电流特性。当电压超过临界值后,电极丝表面会形成不稳定的气层并产生放电现象;随着电压升高,放电状态由火花放电向电弧放电过渡。对石英玻璃的加工实验结果显示,通过增加电压并使放电电压维持在火花区内,能在保证表面质量较好的同时提高加工效率,在电弧区加工可得到更高的材料去除率,但工件表面质量会下降。     

超声振动辅助机械铣削复合电化学放电加工

传统机械加工易造成石英玻璃等绝缘硬脆材料表面微裂纹损伤和侧壁崩碎过切的现象.电化学放电加工可实现石英玻璃的无损伤加工且加工精度可达到微米级,但难以解决无损伤加工精度和加工效率之间的矛盾.以表面无损伤高效率加工石英玻璃为目标,提出了超声振动辅助机械铣削复合电化学放电加工的新方法,分析了该方法的作用机制;采用高速气动主轴实...     

喷雾电化学放电加工难导电硬脆材料试验研究

针对传统电解电火花加工难导电硬脆材料存在的问题,提出了一种使用开槽金属轮作为一极,另一极为紧贴工件表面的进电金属片的喷雾电化学放电加工方法,对单晶硅和氧化铝陶瓷进行了试验研究,并加工出了窄槽实物。通过分析加工表面微观形貌可知,单晶硅等半导体材料主要依靠电化学腐蚀、电化学放电和化学溶解进行综合蚀除,氧化铝陶瓷等绝缘材料经电化学放电通常只能产生软化层,再由机械方法实现延性方式去除。最后研究了峰值电压、脉冲宽度、脉冲间隔、电解液浓度、开槽金属轮转速等因素对单晶硅和氧化铝陶瓷材料去除率和表面粗糙度值的影响规律。     

绝缘陶瓷往复走丝线切割加工放电状态检测方法

绝缘陶瓷材料在工程中应用广泛,但由于其脆硬性,用普通方法很难加工.通过辅助电极利用往复走丝电火花线切割的方法对绝缘陶瓷氮化硅作了加工实验研究,并用普通金属与电阻串联的方法进行了仿绝缘陶瓷氮化硅加工实验研究.对实验数据进行了分析,根据导电层对维持电压的影响情况,将导电层分为良、中、差3个等级, 并设计出一种专门用于绝缘陶瓷碳化硅往复走丝线切割加工放电状态检测的方法,能区分出3种处于不同导电层等级状况下的正常放电、空载以及短路等5种放电状态.     

Enhancement of ECDM efficiency and accuracy by spherical tool electrode

Electrochemical discharge machining (ECDM) is an emerging non-traditional processing technique that involves high-temperature melting and accelerated chemical etching under the high electrical energy discharged. However, there are still several obstacles to overcome. First, both machining time and hole entrance diameter were found to increase with increasing machining depth. In particular, the increase becomes drastic when machining depth exceeds 250 μm. In addition, achieving both high efficiency and accuracy in drilling a through hole in hard and brittle materials by ECDM poses even greater difficulty. To solve the above problems, this study proposed using a tool electrode with a spherical end whose diameter (150 μm) is larger than that of its cylindrical body (100 μm). Experimental results show that the curve surface of the spherical tool electrode reduces the contact area between the electrode and the workpiece, thus facilitating the flow of electrolyte to the electrode end, and enables rapid formation of gas film, resulting in efficient micro-hole drilling. Moreover, the curve surface does not cause excessive concentration of current density; and hence, bubbles grow at a more uniform speed; thus, increasing the discharge frequency. Comparison between machining depth of 500 μm achieved by conventional cylindrical tool electrode and the proposed spherical tool electrode shows that machining time was reduced by 83% while hole diameter was also decreased by 65%.     

Voltage pulse frequency and duty ratio effects in an electrochemical discharge microdrilling process of Pyrex glass

Electrochemical discharge machining (ECDM) is used to microdrill glass wafers. One of the drawbacks of ECDM is the heat-affected zone (HAZ) left on the microdrilled hole surface. To reduce the HAZ, a series of rectangular voltage pulses, were applied in this study instead of the rectified or full-wave DC voltages. The effect of the frequency and duty ratio of the voltage pulse on the ECDM of Pyrex glass was experimentally investigated. The experimental results show that the thermal damage of the microdrilled hole decreases as the frequency increases and as the duty ratio decreases. It was also found that the clearance increases as the tool diameter decreases. This experimental investigation provides a new method that exhibits several advantages over conventional ECDM.     

特种加工技术最新研究进展——第16届国际电加工会议论文综述

通过对第16届国际电加工会议论文进行综述,介绍了近几年来国际特种加工领域的最新研究进展.主要概括了电火花加工、电化学加工、电化学放电加工及激光加工等研究成果.     

Modeling and experimental investigation of gas film in micro-electrochemical discharge machining process

Electrochemical discharge machining (ECDM) is a promising machining technology that effectively machines non-conducting and brittle materials, featuring good material removal rate, flexibility, and accuracy of machining. ECDM makes use of the electrochemical discharge phenomenon to trigger the discharging by the gas film surrounding the tool electrode. As the fundamental of electrochemical discharging, gas film is essential to the machining quality and efficiency. However, modeling of gas film in electrochemical reaction is not well established. This paper presents analytical modeling of the gas film, involving bubble growth and departure on electrode, gas film evolution, and electrolysis characteristics. Experiments were carried out to compare models to the actual discharging phenomenon. High speed camera imaging demonstrated the formation of a gas film on the tool electrode. The range of thickness of gas film found in experiments indicated good consistency with the range of film thickness estimated from analytical models. Experiments on critical voltages and currents further revealed the characteristics of the gas film in electrochemical reaction.     

Non-conventional machining of particle reinforced metal matrix composite

Particle Reinforced Metal Matrix Composites (PRMMC's) have proved to be extremely difficult to machine using conventional manufacturing processes due to heavy tool wear caused by the presence of the hard reinforcement. This paper presents details and results of an investigation into the machinability of SiC particle reinforced aluminium matrix composites using non-conventional machining processes such as Electro Discharge Machining (EDM), laser cutting and Abrasive Water Jet (AWJ). The surface integrity of the composite material for these different machining processes are examined and compared. The influence of the ceramic particle reinforcement on the machining process was analysed by tests performed on samples of the non-reinforced matrix material.     

Fixed abrasive machining of non-metallic materials

This paper summaries advancements in fixed abrasive machining of non-metallic materials, which include reinforced concretes, stones, rocks, carbon fiber reinforced plastic, metal and ceramic matrix composites, wood, wood-fiber plastic composite, biomaterials (bone, plaque, and enamel), and structural and electronic ceramics. The broad impacts, diverse applications, and innovations of fixed abrasive machining processes are presented. Benefits of the engineered deterministic distribution of abrasive grain grinding tools are demonstrated. Industrial perspectives and future research on innovative fixed abrasive machining technologies that enable new processes and improve the productivity are highlighted.     

Precision machining of small holes by the hybrid process of electrochemical removal and grinding

This paper presents a hybrid process of grinding and electrochemical removal for machining of precision small holes with hard-to-machine materials. In the process, a metal rod with coated abrasives as cathode tool rotates at high speed and removes material electrochemically and mechanically for a pre-machined pilot hole. The effects of process parameters on the hole surface quality and dimensional accuracy were demonstrated experimentally. Material removals on grinding and electrochemical machining are well balanced by rationally determining machining voltage, tool rotation speed and feed rate. Precision holes of diameters down to 0.6 mm with sharp edges and without burrs have been produced.     

Micro electrochemical machining for complex internal micro features

In this paper, the application of micro electrochemical machining (ECM) for the micromachining of internal features is investigated. By controlling pulse conditions and machining time, micro features are machined on the side wall of a micro hole. These methods can easily machine a micro hole with larger internal diameters than the entrance diameter, which is very difficult to do by the conventional processes. A micro disk-shaped electrode with an insulating layer on its surface is also introduced to machine microgrooves inside the hole. This method is similar to the turning lathe process. The purpose of this study was to confirm the various possibilities of making complex internal structures in a micro hole by micro ECM.     

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.     

混粉电解电火花复合加工工艺研究

在电解电火花加工技术的基础上,提出了在电解液中加入导电粉末加工非导电材料的新方法。通过对高硼硅玻璃非导电材料进行混粉电解电火花加工实验,对加工过程中各影响参数(电压、电解液浓度、粉末浓度)进行分析,结果表明:采用混粉电解电火花加工技术可高效地加工脆硬非导电材料的表面,并能获得较好的表面质量。