电极丝随动放电切槽技术试验研究

微细电火花线切割加工时电极丝存在难以避免的振动,且振动幅度随着切割工件厚度的增加而变大,这导致加工出现腰鼓形误差,工件加工效率与加工质量也受影响.针对电极丝的振动问题提出一种电极丝随动放电切槽技术,通过顶丝头的导丝孔和导丝槽抑制电极丝振动,利用电极丝放电蚀除工件完成了长度70 mm、直径0.1 mm的半圆截面长通道的加...     

倾斜式可调电极丝恒张力机构的研究

分析了高速走丝线切割机加工过程中电极丝张力对加工精度的影响，在此基础上开发了一种倾斜式可调恒张力机构，可直接恒定加工时的电极丝张力，减少电极丝的振动，提高加工质量，为实现多次切割创造了条件。     

往复走丝电火花线切割机床张丝系统的研究

分析了往复走丝电火花线切割机床的电极丝振动特性及现有张丝系统存在的问题．提出了电极丝振动主动控制的方法,并进行了实验。结果表明,该方法可提高往复走丝电火花线切割加工的精度。     

难加工材料的超声电火花线切割复合加工工艺研究

开发了一种超声电火花线切割复合加工装置,加工中电极丝可产生横向振动,且振动方向始终与切割方向一致。对难加工材料的切割实验表明;复合工艺能较大幅度地提高加工效率,改善表面质量,降低断丝概率。     

纵扭超声振动电火花加工微小孔仿真研究

超声振动电火花加工是一种高效加工微小孔的新型加工方法,能够提高加工效率与精度。对纵扭超声振动电火花加工微小孔进行研究,建立描述电极丝周围间隙工作液流动特性的数学模型,使用Fluent对数学模型进行验证,同时加入切屑,对间隙工作液运动情况以及排屑情况进行探究。结果表明：在电火花加工时,在电极丝引入纵扭超声振动,流体域有明显的扭转运动,电极丝底部切屑在离心力的作用下,更易从底隙中进入侧隙,随工作液的运动排出孔隙,有效防止底部产生切屑堆积,提高了电火花加工微小孔的精度。     

WEDM加工过程中的电极丝形位变化

电极丝在加工过程中受各种力的作用会发生形位变化。直接影响加工精神度和加工稳定性，本文通过实验分析，研究了电极丝的形位变化规律。并提出了稳定电极丝形位的有关措施。     

稳定电极丝空间形位的一种有效方法

高速走丝电火花线切割加工时电极丝的形位变化较大，严重影响线切割加工的稳定性和加工精度。如何稳定电极丝的空间形位，是高速走丝线切割加工亟待解决的课题。作者在大量试验研究的基础上，开发了一种高耐磨性的导向装置，能有效地稳定电极丝的空间形位，提高线切割加工稳定性和加工精度。     

浮动式电极丝限位器

电极丝振动对加工精度的影响 ,已有较深入的研讨。这里主要分析电极丝位置变化对加工精度的影响。在切割加工中 ,电极丝受到放电力、冲液力、张力等若干力的作用 ,当这些力不能平衡时 ,电极丝在加工区的位置会发生变化 ,在工件上导致几何误差。例如 ,加工一个八边形 ,图 1表示电极丝在加工区的位置变化 ,图 1中的小圆圈表明丝的振动区域 ,可以看出 :第一 ,在切割中电极丝的位置并不是不变的 ,而是随时在变 ,丝的实际路径与理论切割路径是不同的 ;第二 ,电极丝位置的变化与加工轨迹有关 ;第三 ,电极丝位置的变化与导轮Ｖ型槽半敞开式定位有关 ,电极丝位置变化值在走Ｌ3 时最大 ,走Ｌ2 、Ｌ4 时次之 ,走Ｌ1时最小。图 2是加上电极丝限位器后电极丝在加工区的位置变化 ,可以看出 :第一 ,图 2中的小圆圈即丝的振动区域明显减小 ;第二 ,由于有了限位器定位 ,电极丝位置变化与导轮Ｖ型槽无关 ,在Ｌ1、Ｌ2 、Ｌ3 、Ｌ4 各个方向上电极丝位置变化基本相同。很明显 ,电极丝限位器减小了电极丝的振动 ,减小了电极丝位置的变化 ,对提高加工精度、实现多次切割是很有必要的。图 1　电极丝在加工区的位置变化图 2　加上电极丝...     

往复走丝电火花线切割机床电极丝振动研究及抑制措施

对往复走丝电火花线切割机床电极丝振动的影响因素进行了理论分析和实验研究,揭示了由导轮、贮丝筒等引起的外部激励是产生电极丝低频振动的主要原因,提出了稳定电极丝空间形态及减小振幅的两项措施,即使用新型恒张力机构和浮动式限幅器。     

工件超声振动对TC4钛合金快走丝电火花线切割加工表面质量影响的研究

进行了4组对比试验,研究了工件超声振动对TC4钛合金快走丝电火花线切割加工的表面粗糙度及其表面形貌的影响。结果表明:与TC4钛合金快走丝电火花线切割加工相比,在工件上附加超声振动以后,TC4钛合金工件表面粗糙度得到降低,但改变幅度都不一样。在电参数为功率管数2个,脉冲宽度16μs,脉冲间隔比为6时,表面粗糙度改变幅度最大。对比无超声振动,发现在工件上附加超声振动以后,形成的小凹坑更加均匀规则,且小凹坑的边缘更加光滑。     

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.     

旋转超声辅助加工装置及其工艺研究

基于传统超声振动理论,提出了一种新型旋转超声辅助加工装置。该装置将超声振动与负载匹配二者相结合,具备旋转超声辅助加工硬脆材料的能力。利用该装置对微波铁氧体材料进行旋转超声辅助钻削加工试验研究,验证了旋转超声辅助磨削可有效降低加工过程中的切削力。同时,在保证刀具和材料安全的前提下,探索了旋转超声辅助加工装置对加工效率的影响。     

Perspectives offered by combining a laser beam with arc welding procedures

Summary

With regard to the fact that, during Cu wire stitch bonding of copper lead frames, the wire deformation strongly affects the bondability and strength of the bonds obtained, this paper describes an investigation of the wire deformation being varied through variation in the initial capillary tip load and capillary tip load during application of ultrasonic vibration as well as the bondability and bond strength then obtained. When stitch bonding with soft copper wire is performed by the two‐step load control method, which has a higher initial capillary tip load and a lower capillary tip load during the second stage, the range of action of the material being worked under ultrasonic vibration can be widened, the deformation during the working time of ultrasonic vibration can be suppressed, the ultrasonic energy can make a greater contribution to bonding, and a higher bond strength can be obtained. The results obtained in this study suggest that, during wire bonding by the two‐step load control method, the optimum capillary tip load is obtained. Within the presently adopted experimental range, the optimum values are a capillary tip load of 1.4 N before the application of ultrasonic vibration and a capillary tip load of 0.4 N during ultrasonic vibration.     

The effect of tool geometry on regenerative instability in ultrasonic vibration cutting

Ultrasonic vibration cutting as a cutting process has been widely used in the precision machining of difficult-to-cut materials due to an enhanced cutting stability and increased productivity. The authors' previous researches have shown that chatter vibration prediction is made possible by the suggested cutting model. This paper is an attempt to determine cutting parameters based on regenerative chatter prediction in order to facilitate the machining objectives of high accuracy, high efficiency and low cost in ultrasonic vibration cutting. The machinability of SCM440 steel, called typical hardened steel, is investigated theoretically and experimentally. The cutting model is developed by introducing an experimental cutting database of SCM440 steel. The simulation and experimental results show that the workpiece material parameter has a direct influence on the occurrence of regenerative chatter. In order to achieve the chatter-suppressing dynamics in hard ultrasonic vibration cutting, a stability diagram is predicted based on the simulated work displacement for tool geometry changing. The stability diagram indicates that the regions of the chatter-suppressing dynamics expand with increasing tool rake angle and decreasing tool clearance angle. It is also found from the predictive results that regenerative chatter can be suppressed by a change of tool geometry. The determined tool geometry with the aid of the computer simulation is demonstrated through actual data of ultrasonic vibration cutting. By the use of the designed tool geometry, a good experimental result is achieved.     

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.     

Ultrasonic elliptical vibration transducer driven by single actuator and its application in precision cutting

The ultrasonic elliptical vibration cutting has been successfully applied to precision cutting due to its superior performances, such as low cutting force, high quality surface finish and long tool life. This paper presented an asymmetrical structural model of the ultrasonic elliptical vibration transducer with only the longitudinal excitation. Based on the modal and static analysis with finite element method, various parameters of the model were modified to meet the needs of the vibration modality and the inherent frequency. A cutting system of the ultrasonic elliptical vibration driven by single longitudinal actuator was developed and the effect of the transducer amplitude and cutting depth on the cutting force was studied in detail. A part with surface roughness of R_a 0.08 μm was achieved. The results showed that the ultrasonic elliptical vibration transducer can be designed rationally with finite element method and single driven ultrasonic elliptical vibration machining can be used in precision cutting.     

超声振动磨削放电复合加工SiCp／Al试验研究

针对SiCp／Al的加工,提出一种超声振动磨削放电复合加工的方法．从加工效率、加工稳定性及表面质量等方面与电火花加工进行了对比试验研究。分析了两种加工方法的脉冲宽度和峰值电流对加工速度和表面粗糙度的影响,结果表明：电火花加工的表面粗糙度平均值为尺04．5μm,超声振动磨削放电复合加工的表面粗糙度平均值为Ra2μm：超声振动磨削放电复合加工的稳定性比电火花加工好,但加工速度较低。通过扫描电镜对两种加工方法下零件表面形貌和重熔层进行了观测,对试件表面进行了X射线衍射分析,表明采用超声振动磨削放电复合加工SiCp／Al复合材料可获得较好的表面质量。     

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.     

切削法制备超细晶材料研究进展与展望

综述了切削法制备超细晶材料时加工参数和工艺条件对晶粒细化的影响,分析了切削法制备超细晶材料的力学性能、耐腐蚀性能和热稳定性等,探讨了超声振动复合切削法制备超细晶材料的可能性。在超声振动加工中,材料受低应力高速、高频撞击的影响,会发生严重的塑性变形,表面大尺寸的晶粒得到细化,同时超声振动还可以在材料表面形成表面微结构,进一步改善材料性能。因而提出将切削法和超声振动相复合,高效制备具有功能微结构的超细晶材料,为微型零件超细晶材料制备提供新的工艺选择以及理论和技术支撑。