石墨电极电火花加工性能的影响因素分析

影响石墨电极电火花加工性能的因素很多，各因素的合理配合对电火花加工特性有重要的影响。分析了主轴性能、脉冲电源及智能控制、工作液、电参数和加工极性选择等对石墨电极加工性能的影响，为生产实践提供了理论依据。     

Real-time Tool Wear Compensation in Milling EDM

Accurate machining by milling EDM (i.e. CNC contouring EDM with a rotating cylindrical or tubular electrode) necessitates compensation of the tool electrode wear. Existing anticipated wear compensation is based on off-line tool wear simulation prior to machining. This can be combined with corrections based on periodical measurements of tool length during machining. Anticipated wear compensation involves an important restriction: an exact model of the blank geometry must be available in order to perform the tool wear simulation. This paper presents a new method of wear compensation. On-line estimation of tool wear is used for combining anticipated compensation with real-time compensation. This extends the scope of milling EDM to the machining of blanks of which the exact shape is not known in advance.     

基于旋转电极的方孔电火花加工新方法

提出一种方孔电火花加工新方法,利用具有勒洛三角形截面形状的工具电极在等宽方形约束孔中转动,使电极沿横截面扫过一个正方形区域,从而通过电极底面放电加工出方孔。分析了勒洛三角形电极在与其等宽的方孔中的运动方式和轨迹,设计了基于旋转电极的方孔电火花加工装置,通过实验验证了该方法的可行性。在不同的开路电压下,分别利用旋转的勒洛三角形电极和不旋转的方形电极进行方孔加工,发现旋转的勒洛三角形电极加工效率更高、电极损耗更低。     

复杂型面多轴电火花加工的电极损耗补偿

在复杂型面的多轴电火花加工中,电极损耗对加工精度具有影响显著,因此,对电极损耗进行准确补偿非常重要。通过研究得出电极表面损耗与电场强度有关,并建立了电极损耗系数与电场强度之间的关系。在此基础上,提出了考虑电极运动路径的电极损耗补偿方法,并通过加工实验证明了该方法的准确性与有效性。     

电火花加工中多材质电极损耗规律的实验研究

针对电火花加工中多材质电极的损耗和形状变化,在模具钢工件上开展了电火花多材质电极加工实验研究,分析了电极材料、加工极性对多材质电极损耗的影响规律,并以黄铜-模具钢电极、紫铜-铜钨合金电极为研究对象,分析了多材质电极的形状变化规律。结果表明:长度损耗小的电极材料能辅助减小同组其他材料的电极损耗,但通常其角损耗较大;加工中多材质电极结合处形成过渡曲面,当加工进入均匀损耗阶段后,过渡曲面的圆弧半径和圆心角基本恒定不变。     

Tool path generation for 4-axis contour EDM rough machining

Contour or CNC EDM machining of free-form surfaces requires tool paths that are different from those used in mechanical milling although in geometry both processes are described by the similar model of intersection between the rotating tool and the workpiece. In this paper, special requirements on tool paths demanded by contour EDM machining are studied and a two-phase tool path generation method for 4-axis contour EDM rough milling with a cylindrical electrode is developed. In the first phase of the method, initial tool paths for virtual 3-axis milling are generated in a commercial CAD/CAM system—Unigraphics, which provides users with plenty of options in choosing suitable tool path patterns. From these tool paths, cutter contact (CC) points between electrode and workpiece are reversely calculated. In the second phase, considering the special requirements of EDM machining, which include discharging gap compensation, electrode wear compensation, DC arcing prevention, etc., the electrode is adjusted to an optimized interference-free orientation by rotating it around the CC points obtained in the previous phase. This new orientation together with the reference point of electrode is output as new tool path. The whole algorithm has been integrated into Unigraphics, machining simulations and tests have been conducted for 4-axis contour EDM rough machining.     

混粉电火花加工机理的分析

论述了混粉电火花加工的发展概况 ,并以实验为基础对其机理进行了分析 ,认为加工表面粗糙度的迅速降低主要是放电通道对熔融金属平整作用的结果。对于这一工艺的加工效率进行了剖析 ,认为从改善表面质量的角度来看 ,混粉电火花加工具有很高的加工效率。通过对电极损耗情况的观察 ,发现电极损耗特性也有一临界点 ,这一点与普通电火花加工相似     

微细电火花铣削电极运动轨迹加工工艺实验

在微三维结构微细电火花铣削过程中,电极运动轨迹的规划直接影响产品的加工效率和工具电极的损耗。针对钛合金微三维结构进行了不同铣削方式的加工工艺实验,选取了最佳电极运动轨迹,其加工时间和电极损耗均明显低于其他铣削方式。     

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。     

电火花加工数控代码疏化方法

虽然电火花加工能很好地解决高硬度材料难切削的问题,但其加工效率偏低。通过研究数控代码的密集程度对电火花加工效率的影响,并从抬刀运动的角度分析密集数控节点会使加工时间大大延长的原因,从而提出了在电极进给轨迹上以最大不干涉间距选取数控节点的方式来生成数控代码的方法。一方面可大大减少数控代码量,另一方面也可避免抬刀过程频繁加减速的现象,最终有效地提升电火花加工的效率。     

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。     

High-speed EDM milling with moving electric arcs

A novel high-speed electrical discharge machining (EDM) milling method using moving electric arcs has been proposed in this study. We connected a copper electrode rotating rapidly around its axis and a work piece to a DC power supply to generate a moving electric arc. To ensure high relative speed of any point on the electrode with respect to the work piece, the electrode was shaped like a pipe. It was observed that the electric arcs move rapidly within the discharge gap due to the revolution of the tool electrode, removing the materials on the electrode along the track of the arc roots. To explore the characteristics of machining with moving electric arcs, an EDM milling apparatus was devised. Two planes with approximately the same roughness were machined separately by this equipment and a traditional EDM machine for comparison. It was found that a much higher material removal rate can be easily achieved by EDM milling with moving electric arcs. In the meanwhile, wear of the tool electrode in this new method is negligible, which is greatly favorable for machining accuracy. The microstructures of these surfaces were also investigated for further information.     

High Aspect Ratio and Complex Shaped Blind Micro Holes by Micro EDM

It is difficult to drill high aspect ratio through holes and complex shaped blind holes using micro EDM. The debris concentration in the narrow discharge gap causes abnormal discharges leading to excessive electrode wear and lower machining precision. In micro EDM, the electrode size is too small for internal flushing. This paper presents a new approach for effective self-flushing using planetary movement. Through micro holes with an aspect ratio of 18 have been drilled. This approach is also demonstrated by drilling blind noncircular micro holes with sharp corners and edges. The process performance characteristics are analyzed under different machining conditions.     

Electrical discharge machining of Ti6Al4V with a bundled electrode

The aim of this study is to investigate an efficient Ti6Al4V electrical discharge machining (EDM) process with a bundled die-sinking electrode. The feasibility of machining Ti6Al4V with a bundled electrode was studied and its effect on EDM performance was compared experimentally using a solid die-sinking electrode. The simulation results explain the high performance of the EDM process with a bundled electrode by through the use of multi-hole inner flushing to efficiently remove molten material from the inter-electrode gap and through the improved ability to apply a higher peak current. A 3-factor, 3-level experimental design was used to study the relationships between 2 machining performance parameters (material removal rate: MRR, tool wear ratio: TWR) and 3 machining parameters (fluid flow rate, peak current and pulse duration). The main effects and influences of the 2-factor interactions of these parameters on the performances of the EDM process with the bundled electrode are discussed.     

Improvement of Dry EDM Characteristics Using Piezoelectric Actuator

This paper describes improvement of the machining characteristics of dry electrical discharge machining (dry EDM) by controlling the discharge gap distance using a piezoelectric actuator. Dry EDM is a new process characterized by small tool electrode wear, negligible damage generated on the machined surface, and significantly high material removal rate especially when oxygen gas is used. However, the narrow discharge gap length compared with conventional EDM using oil as the dielectric working fluid results in frequent occurrence of short circuiting which lowers material removal rate. A piezoelectric actuator with high frequency response was thus introduced to help control gap length of the EDM machine. To elucidate the effects of the piezoelectric actuator, an EDM performance simulator was newly developed to evaluate the machining stability and material removal rate of dry EDM.     

High Speed 3D Milling by Dry EDM

This paper describes the high speed EDM milling of 3D cavities using gas as the working fluid. In this new process, the molten workpiece material is removed and flushed out of the working gap with the help of high-pressure gas flow. The advantages or this technique are the remarkably small tool electrode wear and the significantly high material removal rate especially when oxygen gas is used due to the extremely strong oxidation of steel workpieces. Experiments showed that the material removal rate increases dramatically when the discharge power density on the wonting surface exceeds a certain threshold due to thermally activated chemical reaction between the gas and workpiece material. The maximum removal rate obtained was almost equal to that of high speed milling of quenched steel by a milling machine. The machining accuracy was considerably better when the gas was sucked through the pipe electrode than Jetted.     

转向直拉杆锻模型腔的电火花加工

以微型车转向直拉杆零件锻模型腔的电火花加工为例 ,对锻模型腔的电火花加工方法 ,电极的设计方案与制造工艺进行了分析和探讨 ,提出了一种可以保证模具型腔有足够重复精度的电火花加工电极的设计与制造方法     

镍基高温合金Inconel718的超高效电火花电弧复合加工

提出了一种超高效电火花电孤复合铣削镍基高温合金Ineonel718的加工方法．构建了一种新型大功率电源,主要由高压脉冲电源和低压大功率直流电源组成。在冲液和电极旋转的作用下得到了非连续电弧,材料去除率可达13421mm3／min,相对电极损耗率可达1．71％。进行了复合加工和电火花加工的对比实验研究,分析了电极转速对材料去除率和相对电极损耗率的影响,并对加工表面特性进行了研究。     

基于非接触给电的高主轴转速微细电火花加工特性研究

在实现非接触给电的微细电火花加工的基础上,分别研究了圆柱电极和削边电极的主轴转速对材料去除率及电极损耗的影响。结果表明:无论是圆柱电极还是削边电极,随着主轴转速的提高,材料去除率增加,电极损耗率降低;且在削边电极的情况下,主轴转速的提高对于材料去除率和电极损耗率的改善更明显。