大厚度工件电火花线切割加工多次切割腰鼓度成因研究

为研究往复走丝电火花线切割加工在大厚度工件多次切割时形成腰鼓度的成因,对厚度为185 mm的工件进行了多次切割实验,通过改变工作液电导率、电极丝走丝速度、修刀补偿量和电极丝直径等条件,对加工形成的腰鼓度进行了测试及分析。结果表明:大厚度切割过程中,两极之间的脉冲放电爆炸力是产生腰鼓度的主要原因,通过增加电极丝直径以提高电极丝截面惯矩,可减小因放电爆炸力对电极丝形成的挠度,从而减小腰鼓度误差值。     

电极丝超声振动的低速走丝电火花线切割加工研究

研究了低速走丝电火花线切割加工中附加超声振动后电极丝的高频振动对加工性能的影响。建立了描述超声振动下的电极丝振动的数学模型，并进行了计算机模拟分析。实验表明，电极丝附加超声振动可以改善极间放电状态，提高加工效率，减少断丝率，降低加工表面粗糙度值。     

大深径比微细孔超声辅助电火花加工技术研究

微细电火花加工中电极损耗较大,在加工大深径比微细孔时,工具电极和工件之间的狭窄间隙内流体阻力较大,气泡及加工屑不易排出,易产生频繁的非正常放电,导致电极损耗进一步增大.针对大深径比微细孔加工的这一难题,提出采用电极摇动同时在工件上加载超声波振动的新方法,成功地在3.5 mm厚的不锈钢板上加工出平均直径为120 μm的通...     

电火花线切割拐角加工精度的实时预测

提出了一种电火花线切割加工拐角加工精度的实时预测方法,并为此建立了实时预测系统.系统根据实时采集的放电能量等加工参数,通过电极丝振动解析及数控轨迹与电极丝位置关系的分析,可得出电极丝形变量与加工误差,从而可将拐角加工形状实时地再现于计算机上,实现了拐角加工精度的实时预测.     

电火花线切割加工技术最新研究进展

介绍了近年来国内外电火花线切割加工技术的最新研究进展,包括加工变厚度工件过程中工件厚度的在线辨识及参数优化与控制,提高加工拐角精度电极丝偏差的在线检测,基于浮动阀值的放电间隙状态检测技术,在机床加工中表面质量修正技术以及混粉对提高加工质量以及加工效率的研究等.     

连杆裂解槽线切割机床工作液过滤系统的设计

在连杆裂解槽线切割机床加工过程中,工作液中会混入微米级的固体颗粒和亚微米级的悬浮物,前者来自工件与电极丝放电气化蚀除的金属产物,后者来自工件材料受高温气化分解及工作液分解的微细产物,这些金属微粒会影响工件与电极丝之间放电间隙的形成,进而影响连杆裂解槽的加工质量与效率。针对工作液在加工过程中颗粒成分及温度的变化,设计了新型连杆裂解槽线切割机床工作液过滤系统,并通过实验证明了设计的可行性。     

微细倒锥孔电火花加工机构设计及其实验研究

研制了一种微细倒锥孔电火花加工机构模块,该模块在维持电极丝本身不旋转的状态下,控制电极丝端部偏转,以此加工出微细倒锥孔.分析了影响机构加工精度的主要因素,并实验研究了加工过程中脉冲电压、放电电容对加工孔形状的影响.结果表明,用直径120 μm的电极丝可在1 mm的钢片上加工出入口孔径190 μm、出口孔径220 μm的倒锥孔.     

工作液超声振动辅助电火花小孔加工装置设计与试验

电火花加工小孔存在电蚀产物排出效率低导致加工效率低、电蚀产物排除导致二次放电现象影响加工精度等问题,而超声振动在工作液中产生空化效应和泵吸作用,能大幅提高电火花的排屑和消电离能力,进而在很大程度上减少上述问题的发生。设计一套工作液超声振动辅助电火花小孔加工装置,主要包括主轴系统、微三维运动平台、超声振动工作液槽和数据采集系统,其中主轴系统包括NSK电主轴、引电结构、工具电极装夹结构,可以实现工具电极的高速旋转;基于LabVIEW开发了电火花小孔加工控制系统,主要包括初始化模块、粗定位模块、恒电压对刀模块、实时电压分段控制加工模块和实时显示模块。开展了工作液超声振动辅助电火花小孔加工试验研究,试验结果表明：随电火花加工电压的增加,工件材料去除率和电极损耗率都趋于增大。     

振动辅助液中喷气电火花加工性能研究

提出了振动辅助液中喷气电火花加工方法。该方法通过工件机械振动改善了极间的放电状态,降低了短路率。通过实验研究了机械振动的频率和振幅对液中喷气电火花加工性能的影响,研究了振动辅助作用下电加工参数、气体压力、工具电极转速对加工性能的影响。结果表明,工件的机械振动可有效提高液中喷气电火花加工的材料去除率,改善加工表面质量,而电极损耗几乎为零。     

电火花线切割加工中电极丝的安装

电极丝的安装正确与否,直接关系到加工后工件质量的好坏.只有注意到安装前的检查、上丝、穿丝和电极丝的校正这4个重要环节,才能为后续的工件加工提前做好准备.     

移动热源作用下电火花线切割加工电极丝三维温度场模拟

往复走丝和“中走丝”电火花线切割机床是中国独创的电加工设备,在模具制造等行业发挥着重要作用.由于其电极丝是重复使用的,因此电极丝损耗是普遍存在的问题.在电极丝与工件之间相对运动的情况下,建立了移动热源条件下的电极丝传热模型,通过有限元分析对单脉冲放电条件下电极丝表面温度场进行了三维仿真,发现当走丝速度增加时电极丝熔融区...     

A macroscopic mechanical model of wire electrode deflection considering temperature increment in MS-WEDM process

In medium-speed wire electrical discharge machining (MS-WEDM), wire in the area near the guide wheel and between the two guide wheels obviously form the wire bending deformation due to wire tension, electrostatic force, electrodynamics force, hydrodynamic force, temperature increment, etc. Besides, the wire deflection would have a direct influence on the machining accuracy, productivity and stability. In this paper, first of all, main causes of wire electrode deformation are proposed to better understand its fundamental mechanism. Second, two macroscopic mechanical models of wire deflection are developed in the area near the guide wheel and between the two guide wheels considering temperature increment and wire vibration in machining 20 mm-thickness workpiece process, respectively. Moreover, the numerical solution of deflection in the area near the guide wheel and the theoretical solution of deflection between the two guide wheels has been worked out. Then, the analysis of the variation trend of wire deflection and the influences of wire deflection on the machining process have been conducted. Eventually, from the confirmation experiment and comparison with other researchers’ models, it has been proved that the macroscopic mechanical models of wire deflection in MS-WEDM process are reasonable and reliable. In addition, according to macroscopic mechanical models, some of the practical approaches of reducing wire deflection have been proposed to improve machining accuracy, and these high-precision models can be applied into NC system to set a compensation for wire deflection in the future.     

A study on the effect of different vibration-assisted methods in micro-WEDM

In micro electrical discharge machining (μEDM), since the discharge energy is very low and is usually performed by a resistor-capacitor (RC) generator the discharge process is highly complex and unpredictable. In addition, due to low discharge energy the discharge is unstable and the machining efficiency is reduced as a result of poor flushing condition in a very small gap. This greatly affects the productivity and limits micro EDM applications. This paper presents development methods to improve the machining efficiency of a widely accepted non-traditional machining process, micro wire electrical discharge machining (WEDM), using non-ultrasonic vibration. It is found that when vibration is applied to the micro-WEDM process, discharge is much more effective with fewer short circuits. From experiment results, it is observed that greater improvement can be achieved when the vibration is applied to the workpiece rather than to the wire. With vibration applied to the workpiece, machining efficiency can be increased by 2.5 times greater than without vibration and 1.5 times compared to the case vibration is applied to the wire. In addition, there exists an optimum relation between vibration parameters, energy and feedrate such that EDM at a constant feedrate can further improve the machining efficiency.     

Improving machining performance of wire electrochemical discharge machining by adding SiC abrasive to electrolyte

The use of wire electrochemical discharge machining (WECDM) to slice hard brittle materials has recently been studied because its effectiveness is independent of the mechanical characteristics of the machined materials. Therefore, materials with high hardness, brittleness, strength and electrical insulation, which are difficult-to-cut, can be machined. In ECDM, the electrochemical reaction produces hydrogen bubbles, which accumulate around the cathode. A thin gas layer forms on the surface of the electrode and isolates the electrode from the electrolyte. When a voltage that exceeds the critical voltage is applied, continuous discharge occurs. The material near the electrode is removed by the discharge erosion and chemical etching. The use of WECDM to cut electrically insulating materials has only recently been investigated. However, the breakdown of the gas in the bubbles and the vibration of the wire in WECDM strongly affect the shape accuracy. This work aims to improve the over cut quality by adding SiC abrasive to the electrolyte. A mechanism that combines discharge, chemical etching and abrasive cutting is studied. The effects on expansion, roughness and material removal rate (MRR) are discussed. The experimental results reveal that adding abrasive reduces the slit expansion because it increases the critical voltage. The particles disrupt the bubble accumulation to form an isolating layer around the wire, increasing the critical voltage and reducing the discharge energy. The surface roughness is improved because the abrasive helps to refine the micro-cracks and melted zone that is formed by discharge heat erosion. Meanwhile, smaller grit produces lower roughness. The quality of the slit can be controlled; its expansion and roughness of the slit are 0.024 mm and 0.84 um Ra, respectively.     

电火花成形加工工具电极损耗预测

电火花成形加工过程中,极间放电在蚀除工件材料的同时,也会对工具电极带来一定程度的损耗,进而影响工件的尺寸及形状精度,降低加工效率。目前普遍采用更换电极重复加工的方式来获得最终形面,需要消耗大量的工具电极和工时。针对电火花加工的工具电极损耗展开了研究,通过系统地分析所得电极形面特征及进给方向与损耗量之间的关系,建立了实用的电极损耗预测模型。通过实验证明了该模型能准确预测工具电极形面损耗,为电火花加工的电极损耗预测提供了有效方法。     

Evaluations of spark distribution and wire vibration in wire EDM by high-speed observation

In fine wire EDM using thin wire electrode, uniform distribution of spark location is necessary to achieve stable machining performance. However, it is difficult to precisely evaluate the distribution of spark location by the conventional branched electric current method when the workpiece is thin. A new evaluation method by using a high-speed video camera is proposed. The locations of spark are measured by analyzing the recorded images. Then the effects of machining parameters, such as servo voltage, pulse interval time, wire running speed and others on the distribution of spark location are investigated. The possibility of evaluating the wire vibration is also discussed.     

计算机控制纳米胶体射流抛光的实验研究

将所设计的纳米颗粒胶体射流加工系统与计算机控制技术结合,实现了计算机控制纳米颗粒胶体射流加工,可将其应用于小曲率半径非球面和自由曲面元件的超光滑表面加工。本试验对一非球曲面高纯石英玻璃元件进行纳米颗粒胶体射流超光滑表面加工,用表面轮廓仪测量了纳米颗粒胶体射流加工前后该高纯石英玻璃元件的表面轮廓曲线。实验结果表明:计算机控制纳米颗粒胶体射流加工,实现了可控的微/纳米材料去除,该非球曲面元件轴向最大去除量为900 nm。原子力显微镜检测结果表明:该元件轮廓截面曲线上的表面粗糙度由Ra2.860 nm降低到Ra0.460 nm。采用纳米颗粒胶体射流技术对小曲率曲面及自由曲面进行超光滑表面加工,是一种确定性超光滑表面的加工方法。     

电火花线切割加工表面微织构技术研究

表面微织构加工是一个相当复杂的过程,涉及微织构的尺寸、质量及形貌等问题。为解决制备微织构存在的问题,利用数控电火花线切割加工技术,在45钢表面加工微槽织构,研究线切割制备微织构的尺寸、形貌。试验分别采用钼丝、铜丝作为电极丝,设计脉宽、脉停、电流等线切割正交试验,切割宽度小于400μm的微槽织构,分析不同线切割参数、电极丝材料对微槽尺寸精度和微槽切口处光整度的影响。通过采集、测量试验所得工件表面微槽织构,发现线切割参数对微槽尺寸精度和切口处光整度有较大的影响;在较小线切割参数下,钼丝切割的微槽尺寸大于铜丝,在较大的线切割参数下,铜丝切割的微槽尺寸大于钼丝;对比微槽切口处光整度,发现钼丝切割的微槽整体质量优于铜丝。试验列出不同线切割参数切割的微槽尺寸,为电火花线切割加工微织构提供了试验数据。