3R电极工装夹具的结构

通过介绍一个简单的3R电极工装夹具的设计、制造、装夹及使用的整个过程,对3R电极的夹具结构进行了详细分析,并详细介绍了3R电极夹具在加工中心及电火花机上的使用方法,同时对比分析了3R电极与普通电极不同的设计方法以及各自的弊端。     

电火花放电加工中工具电极损耗理论研究

在电火花放电加工过程中,采用负极性加工时,工具电极的损耗主要是由于火花放电前几百秒出现的电子流对工具电极表面的轰击造成的,本文对极间脉冲电流和电压的变化进行研究,推导出电子流传递给工具的能量,并考虑到放电过程中的出现的正极积碳现象,在此基础并具电极损耗量的模型,最后用实验验证。     

整体式香蕉水口电极的夹具设计及加工

借助电火花加工机床的C轴功能,利用香蕉水口电极实现整体式香蕉水口加工、香蕉水口电极的装夹定位和加工精度的优化.     

气中连续放电辅助加工中的控制系统设计

以压电陶瓷微位移驱动原理为基础，对精密驱动技术在气中连续放电辅助加工控制系统中的应用进行了研究。设计了一个包括单片机、压电陶瓷驱动电源、信号检测及处理电路组成的气中连续放电辅助加工控制系统。该系统能根据加工时两电极间电压的变化自动寻找最佳放电间隙，并维持辅助加工中的连续放电,可应用于一些高硬度、难切削材料的辅助加工领域。     

电火花放电加工中工具电极损耗理论研究

在电火花放电加工过程中 ,采用负极性加工时 ,工具电极的损耗主要是由于火花放电前几百纳秒出现的电子流对工具电极表面的轰击造成的。本文对极间脉冲电流和电压的变化进行研究 ,推导出电子流传递给工具的能量 ,并考虑到放电过程中出现的正极积碳现象 ,在此基础上建立工具电极损耗量的模型。最后用实验验证     

铜电极夹具设计

介绍了一种适用大批量加工铜电极的专用夹具,结构简单,在各机床间具有较好的互换性,能提高零件在电火花加工时的定位精度,并减少装夹时间,提高产品精度和生产效率。     

高速电弧放电加工的多孔电极制备

高速电弧放电加工是利用流体动力断弧机制实现对电弧的有效控制从而去除材料的。流体动力断弧机制的实现依赖于高速的极间流场动力,该动力需由多孔电极的强制内冲液提供。首先阐明了选择石墨作为多孔电极材料的原因;其次,完成了集成CAD、CAE(主要是CFD)和CAM的多孔电极设计、仿真及制造的软件模块,这些模块能依据加工工件的特征快速、高效地完成对应多孔电极的制备;最后,为了验证制备的一系列多孔电极的电弧加工能力,对典型工件包括具有复杂3D型腔的零件进行了加工实验。结果表明:基于多孔电极的高速电弧放电加工能实现很高的材料去除率(MRR14 000 mm3/min)和较低的工具损耗率(TWR1%),故特别适用于以难切削材料的大余量去除为主的粗加工。     

简易工装夹具在加工电极中的应用

通过一个简单的电极工装夹具的设计、制造、装夹及使用的整个过程,证明在使用加工中心加工电极时,合理地使用工装夹具,不仅能辅助操作工人快速地实现电极的装夹,省去分中、校表等繁琐的工序,从而减轻工人的劳动强度,节省工人的劳动时间,还能大大提高加工中心的工作效率。     

车轴攻螺纹组合机床夹具的研制

在同一台机床上加工符合设计要求的机车、车辆的车轴，必须解决机床具夹的定位夹紧精度及通用性问题。文章介绍了对车轴的工艺分析和组合机床夹具的结构以及夹具的的特点。     

An investigation of ultrasonic-assisted electrical discharge machining in gas

This study focuses on using ultrasonic to improve the efficiency in electrical discharge machining (EDM) in gas medium. The new method is referred to as ultrasonic-assisted electrical discharge machining (UEDM). In the process of UEDM in gas, the tool electrode is a thin-walled pipe, the high-pressure gas medium is applied from inside, and the ultrasonic actuation is applied onto the workpiece. In our experiment, the workpiece material is AISI 1045 steel and the electrode material is copper. The experiment results indicate that (a) the Material Removal Rate (MRR) is increased with respect to the increase of the open voltage, the pulse duration, the amplitude of ultrasonic actuation, the discharge current, and the decrease of the wall thickness of electrode pipe; and (b) the surface roughness is increased with respect to the increase of the open voltage, the pulse duration, and the discharge current. Based on experimental results, a theoretical model to estimate the MRR and the surface roughness is developed.     

Near dry electrical discharge machining

This study investigates the near dry electrical discharge machining (EDM) process. Near dry EDM uses liquid–gas mixture as the two phase dielectric fluid and has the benefit to tailor the concentration of liquid and properties of dielectric medium to meet desired performance targets. A dispenser for minimum quantity lubrication (MQL) is utilized to supply a minute amount of liquid droplets at a controlled rate to the gap between the workpiece and electrode. Wire EDM cutting and EDM drilling are investigated under the wet, dry, and near dry conditions. The mixture of water and air is the dielectric fluid used for near dry EDM in this study. Near dry EDM shows advantages over the dry EDM in higher material removal rate (MRR), sharper cutting edge, and less debris deposition. Compared to wet EDM, near dry EDM has higher material removal rate at low discharge energy and generates a smaller gap distance. However, near dry EDM places a higher thermal load on the electrode, which leads to wire breakage in wire EDM and increases electrode wear in EDM drilling. A mathematical model, assuming that the gap distance consists of the discharge distance and material removal depth, was developed to quantitatively correlate the water–air mixture's dielectric strength and viscosity to the gap distance.     

State of the art electrical discharge machining (EDM)

Electrical discharge machining (EDM) is a well-established machining option for manufacturing geometrically complex or hard material parts that are extremely difficult-to-machine by conventional machining processes. The non-contact machining technique has been continuously evolving from a mere tool and die making process to a micro-scale application machining alternative attracting a significant amount of research interests.In recent years, EDM researchers have explored a number of ways to improve the sparking efficiency including some unique experimental concepts that depart from the EDM traditional sparking phenomenon. Despite a range of different approaches, this new research shares the same objectives of achieving more efficient metal removal coupled with a reduction in tool wear and improved surface quality.This paper reviews the research work carried out from the inception to the development of die-sinking EDM within the past decade. It reports on the EDM research relating to improving performance measures, optimising the process variables, monitoring and control the sparking process, simplifying the electrode design and manufacture. A range of EDM applications are highlighted together with the development of hybrid machining processes. The final part of the paper discusses these developments and outlines the trends for future EDM research.     

Micro-electrical discharge machining of polycrystalline diamond using rotary cupronickel electrode

Cupronickel was used as the electrode material to fabricate microstructures on polycrystalline diamond by electrical discharge machining (EDM). The electrodes were shaped into tiny rotary wheels driven by the flow of EDM fluid. Results showed that material removal rate was improved by a factor of five compared to conventional electrode materials. Raman spectroscopy and energy dispersive X-ray spectroscopy indicated that graphitization of diamond and diffusion-based chemical reactions between nickel and diamond dominated the EDM process. Effects of electrode rotation rate and discharge energy on the EDM characteristics were clarified. High form accuracy (∼0.5 μm/1 mm) and low surface roughness (∼0.1 μm Ra) were obtained.     

Applications of acoustic mapping in electrical discharge machining

The spatial distribution of discharges in electrical discharge machining (EDM) comprises valuable process information, which is not accurately obtained from electrical signals that are utilized extensively for process monitoring and control. This research hence explored the application of acoustic emission (AE) to map the discharges, in consideration of the acoustic time lag. In particular, the work refers to realistic process conditions, wherein AE from successive discharges cause repeated signal interference, which is detrimental to reliable time lag estimation. The applications of this capability for the respective identification of electrode length and workpiece height in fast-hole EDM and wire EDM are presented.     

Thermal stresses due to electrical discharge machining

The high temperature gradients generated at the gap during electrical discharge machining (EDM) result in large localized thermal stresses in a small heat-affected zone. These thermal stresses can lead to micro-cracks, decrease in strength and fatigue life and possibly catastrophic failure. A finite element model has been developed to estimate the temperature field and thermal stresses due to Gaussian distributed heat flux of a spark during EDM. First, the developed code calculates the temperature in the workpiece and then the thermal stress field is estimated using this temperature field. The effects of various process variables (current and duty cycle) on temperature distribution and thermal stress distribution have been reported. The results of the analysis show high temperature gradient zones and the regions of large stresses where, sometimes, they exceed the material yield strength.     

Influence of silicon powder-mixed dielectric on conventional electrical discharge machining

Electrical discharge machining (EDM) is a technological process with a large industrial implementation. Its use is particularly intense when very complex shapes on hard materials with a high geometrical and dimensional accuracy are required. However, the technological capability of the process has limited its application when the specification of the part surface quality imposes polished and mirror-like characteristics. The addition of powder particles in suspension in the dielectric modifies some process variables and creates the conditions to achieve a high surface quality in large areas. This paper presents a new research work aiming to study the performance improvement of conventional EDM when used with a powder-mixed dielectric. A silicon powder was used and the improvement is assessed through quality surface indicators and process time measurements, over a set of different processing areas. The results show the positive influence of the silicon powder in the reduction of the operating time, required to achieve a specific surface quality, and in the decrease of the surface roughness, allowing the generation of mirror-like surfaces.     

Geometric modeling of the linear motor driven electrical discharge machining (EDM) die-sinking process

Based on Z-map method, in this paper the development of a geometric model for the linear motor equipped EDM die-sinking process is described. Firstly discussed are the advantages and benefits of the introduction of the linear motor into EDM die-sinker. The current model has been employed to calculate the minimum gap distance for sparks to occur and to analyze the possibility of spark generation between the workpiece and electrode surfaces. Also calculated is the crater formed by a single spark. The final machined surface topography is predicted. The influence of peak current and discharge duration on the average surface roughness is simulated. The experiment has been conducted to study the effects of machining conditions as well as to verify the effectiveness of the developed geometric model.     

Investigation of the spark cycle on material removal rate in wire electrical discharge machining of advanced materials

The development of new, advanced engineering materials and the need for precise and flexible prototypes and low-volume production have made the wire electrical discharge machining (EDM) an important manufacturing process to meet such demands. This research investigates the effect of spark on-time duration and spark on-time ratio, two important EDM process parameters, on the material removal rate (MRR) and surface integrity of four types of advanced material: porous metal foams, metal bond diamond grinding wheels, sintered Nd-Fe-B magnets, and carbon–carbon bipolar plates. An experimental procedure was developed. During the wire EDM, five types of constraints on the MRR due to short circuit, wire breakage, machine slide speed limit, and spark on-time upper and lower limits are identified. An envelope of feasible EDM process parameters is generated for each work-material. Applications of such a process envelope to select process parameters for maximum MRR and for machining of micro features are discussed. Results of Scanning Electron Microscopy (SEM) analysis of surface integrity are presented.     

Simulation model of debris and bubble movement in consecutive-pulse discharge of electrical discharge machining

Debris concentration and bubble volume fraction in the bottom gap between the electrode and workpiece affect the state of consecutive-pulse discharge and the efficiency of electrical discharge machining (EDM). Thus, the mechanisms of debris and bubble movement during consecutive-pulse discharge should be elucidated. However, these mechanisms have not been fully understood because of debris and bubble movement in the machining gap are difficult to simulate and observe. This study proposes a three-dimensional model of flow field with liquid, gas, and solid phases for machining gap in EDM. The mechanisms of debris and bubble movement in the machining gap during consecutive-pulse discharge were analyzed through the model. Debris and bubble movement in consecutive-pulse discharge was observed through experiments. The results showed that the proposed simulation model is feasible. The bubble expansion is the main way that the bubbles exclude from machining gap. Much debris moves outside the machining gap following the excluded bubbles, which is the main way that the debris excludes from machining gap. The bubble expansion becomes strong with the increase of the discharge current and pulse-on time.