模具加工中的电加工技术新进展

模具制造的需要带动了电加工机床的发展 电加工机床主要用于模具制造业,在复杂、精密、薄壁、窄缝、高硬材料的模具型腔加工中,仍然具有其它加工方法所难以取代的地位。用于模具加工的电加工机床约占其产量的85％以上,其中加工冲裁模的约占65％,加工塑料模的约占15％,其它如压延模和锻模等也有相当的份额。模具制造业在经济发展的国家均形成     

最好的AGIE技术

新的要求 微型化、要求极高的工具和工作质量,轮廓好的重复生产性、小的凸台、筋和锥入度,还有新的粉末冶金钢和硬质合金,所有这些,都要求电加工线切割技术具有最严格要求电源。 采用AGIEPULS HSS电源,AGIE公司就可向市场提供一种能完全满足这些使用要求的‘工具’。下面是     

电加工机床在激烈的竞争中开拓发展

在我们策划这次“电加工设备应用调查”的过程中,得到了中国模具工业协会和苏州加工研究所的大力支持,特别是调查活动的后期,他们对报告提出了一定的完善意见,在此一并表示感谢。 本刊特约苏州电加工所所长叶军先生谈谈电加工机床的发展,他在看了调查报告初稿后对我们所做的工作给予了充分肯定,并在百忙中欣然命笔,结合本报告从行业专家的角度详尽地总结了2003年电加工行业的发展情况,许多都是最新的第一手统计资料,同时分析了电加工技术的发展,特别提出了我国电加工机床将“在激烈的竞争中发展”。关注电加工的读者,此文不可不读。     

Sodick的NF系列简化了EDM操作

传统的EDM缺乏熟练的操作工已成为严重问题。将初学者培养成EDM技术的合格操作工要花很多时间和金钱。而且传统的EDM切削时间长,常常需要不断监视切削条件。 一个值得想望的环境是一个操作工能同时操纵几台机床,而且一旦开始加工就能进入稳定状态而不需看管。这种能力将增加工作效率。用神经(Neuro)和模糊(fuzzy)理论建立新操作环境,在不用NC代码,只用加工条件数据库的情况下就能实验这种能力。因此NC操作就变得容易进行。 神经/模糊(NF) 使用普通的CNC控制,熟练工人主要依靠经验和直觉,常常造成过份的、不经济的安全余度,从而,不能优化加工过程。县有Neuro Study功能的CNC控制系统可以自我学习,并用推理的方法来选择一个理想的切削条件。     

国内外电加工技术与设备发展状况的回顾与展望

本文回硕国内外电加工技术的发展状况,分析电加工机床的市场动态,展望今后,特别是“九五”计划期间我国电加工的科学研究和技术发展方向。     

CIMT2007 电加工机床与测量设备展品预览

电加工机床重点介绍精密、高效展品，这也是世界电加工技术发展的主流。目前，高效线切割机最高切割速度可超过500mm^2／min，精密线切割机最佳表面粗糙度值可达Ra=0．05μm，形状误差可达0．003mm。     

“电加工设备应用调查”分析报告

调查背景和目的 《机械工人》杂志是具有53年历史、在机械制造业具有很高知名度的一本科技刊物，对电加工行业一直颇为关注。2003年下半年《机械工人》杂志社发起．与中国模具工业协会和苏州电加工机床研究所共同举办，而向我国制造业开展了“电加工发备应用调查”活动。     

混粉准干式电火花加工试验研究

提出一种混粉准干式电火花加工技术,其加工介质是气液固三相流混合物。试验结果表明,材料去除率与表面粗糙度随脉冲宽度、峰值电流及分层厚度的增大而增大,脉冲间隙作用则相反,提高空气压力既有助于提高材料去除率又可降低表面粗糙度,电极损耗随脉冲宽度增大而减小,当脉冲宽度较大时电极损耗接近于零,随峰值电流增大而增加。由于液滴、粉末的介入,气体介质的绝缘强度降低,放电间隙会增加,有利于电蚀产物的排除,可减少短路、电弧放电的发生率,加工稳定性得到提高,从而材料去除率得到提高;由于粉末会产生放电分散效果,电蚀凹坑深度减小,工件表面粗糙度降低。     

Accretion of titanium carbide by electrical discharge machining with powder suspended in working fluid

A surface modification method by electrical discharge machining (EDM) with a green compact electrode has been studied to make thick TiC or WC layer. Titanium alloy powder or tungsten powder is supplied from the green compact electrode and adheres on a workpiece by the heat caused by discharge. To avoid the production process of the green compact electrode, a surface modification method by EDM with powder suspended in working fluid is proposed in this paper. After considering flow of working fluid in EDM process, the use of a thin electrode and a rotating disk electrode are expected to keep powder concentration high in the gap between a workpiece and an electrode and to accrete powder material on the workpiece. The accretion machining is tried under various electrical conditions. Titanium powder is suspended in working oil like kerosene. TiC layer grows a thickness of 150 μm with a hardness of 1600 Hv on carbon steel with an electrode of 1 mm in diameter. When a disk placed near a plate rotates in viscous fluid, the disk drags the fluid into the gap between the disk and the plate. Therefore, the powder concentration in the gap between a workpiece and a rotational disk electrode can be kept high. A wider area of the accretion can be obtained by using the rotational electrode with a gear shape.     

Surface modification using semi-sintered electrodes on electrical discharge machining

This study investigates how machining characteristics and surface modifications affect low-carbon steel (S15C) during electrical discharge machining (EDM) processes with semi-sintered electrodes. Among the machining characteristics determined, the material removal rate (MRR), surface deposit rate (SDR), and electrode wear rate (EWR) are included. Additionally, exactly how semi-sintered electrodes affect the surface modifications is also evaluated by electron probe microanalyzer (EPMA), micro hardness, and corrosion resistance tests. The experimental results confirmed that the composition of the semi-sintered electrodes is transferred onto the machined surface efficiently and effectively during the EDM process, and that the process is feasible and can easily form a modified layer on the machined surface.     

A review on the use of dielectric fluids and their effects in electrical discharge machining characteristics

Electrical discharge machining (EDM) is one of the earliest non-traditional machining processes. EDM process is based on thermoelectric energy between the work piece and an electrode. In electrical discharge machining (EDM), a process utilizing the removal phenomenon of electrical discharge in dielectric, the working fluid plays an important role affecting the material removal rate and the properties of the machined surface. Choosing the right dielectric fluid is critical for successful operations. This paper presents a literature survey on the use of dielectric fluids and also their effects in electrical discharge machining characteristics.     

A comparative study on the wear resistance of electrical discharge machined surfaces

The properties of the surface were affected by many factors such as the pulse parameters, tool electrode material, and dielectric liquid in electrical discharge machining. Austenitic, dual-phase, and ferritic steel work materials were electrical discharge machined using graphite and copper tool electrodes in hydrocarbon- based oil and water dielectric liquids. Then the surfaces were analyzed regarding sliding friction wear responses on a comparative basis. The results revealed that the surface wear responses are sensitive to the type of the tool electrode material when machining in water dielectric liquid. However, the use of hydrocarbon-based dielectric liquid substantiality suppresses the influence of tool electrode on surface wear response due to excessive carbon release from the cracked dielectric. The machined surface topographical features were also affected due to the used electrical parameters regarding crater size, globular attachments, and microcracks that led significant alterations in sliding friction response. Primarily, weakly bounded globular attachments on the machined surface were dislodged at the initial stages of the friction tests and led higher sliding distances to the steady friction conditions. Finally, the results were compared with the subsurface microstructural properties to comprehend the wear responses.     

EDM effects on the thermal properties of 36NiCrMo16 steel

In this paper we have studied the effects of the electrical discharge machining (EDM) process on the evolution of thermal properties from the surface towards the core of the 36NiCrMo16 steel using the photothermal deflection (PTD) technique. We have shown that the PTD technique is able to detect the depth of the affected zone, which is characterized by a heterogeneous structure, and allows us to deduce that both the thermal conductivity and the diffusivity would increase from the surface to the core of the sample.     

高速硬切削加工表面白层形成机理研究

白层是高速硬切削的特有现象,对加工表面完整性和零件的服役性能有着重要影响。针对高速硬切削加工表面白层问题,进行了对GCrl5淬硬轴承钢高速硬切削试验和表面白层测试,研究了不同切削条件下的白层形成机理,分析了切削速度和刀具磨损状态对白层特征的影响规律。分析结果表明,白层厚度随切削速度和后刀面磨损的增大而增大,而其分布的均匀性和连续性也将变差;切削速度和后刀面磨损的增加引起切削温度升高,导致加工表面快速淬火效应,使得白层厚度增大,其中切削速度的影响较为显著;在切削速度较低(100 m/min左右)时白层的形成机理主要为塑性变形,切削速度超过300 m/min则主要是马氏体相变所致,而在中间切削速度(200 m/min左右)时为2种机理的混合作用结果。     

闭式整体构件组合电加工关键技术研究

针对包含众多复杂气流通道且由难切削材料制成的封闭式整体构件这一世界性制造难题,对数控电解/数控电火花组合电加工技术进行研究。以几种典型闭式整体构件试制加工为例,论述其总体工艺方案和主要关键技术,包括基于数字化技术的工装夹具、电极及其运动轨迹的设计、加工过程的计算机仿真、叶间流道加工区域划分、工序间加工余量及工艺参数的合理安排等。结合关键闭式整体构件制造技术攻关,通过工艺试验对加工方案进行验证、改进,并试制加工合格的闭式整体构件,解决能加工的问题,相对于单独采用数控电火花加工可提高加工效率40%以上,且能有效降低电极损耗,随着生产批量增大和数控电解加工工艺试验的深入开展,综合加工效率还有较大提升空间。目前已经在新型航空航天发动机、先进透平机械产品的研制中获得成功应用,促进封闭式整体构件制造技术的发展。     

Cost-tolerance relationships for non-traditional machining processes

In recent years, non-traditional machining processes have been growing in popularity and their applications have continued to increase. However, very limited research work has been carried out to investigate their economic implications on tolerance allocation. This paper reports on cost-tolerance relationships for non-traditional processes, namely, electrical discharge wire machining and laser beam machining. Medium carbon steel plates are machined using the two processes to obtain cost-tolerance data which are fitted to various mathematical models. A third-degree polynomial function has been found which gives the most representative fit to the data obtained. An example is presented to illustrate the application and to compare the cost implication of the two machining processes.     

INVESTIGATING THE EFFECTS OF EDM PARAMETERS ON SURFACE INTEGRITY,MRR AND TWR IN MACHINING OF Ti–6Al–4V

Ti–6Al–4V is a kind of difficult-to-cut material with poor machinability by traditional machining methods, while electrical discharge machining (EDM) is suitable for machining titanium alloys. In this paper, three input machining parameters including pulse current, pulse on time and open circuit voltage were changed during EDM tests. To investigate the output characteristics; material removal rate (MRR), tool wear ratio (TWR) and different aspects of surface integrity for Ti–6Al–4V samples such as topography of machined surface, crack formation, white layer (recast layer) thickness and microhardness were considered as performance criteria. The variations of MRR and TWR versus input machining parameters were investigated by means of main and interaction effect plots and also verified by ANOVA results. The effect of pulse energy based on pulse on time and pulse current variations against recast layer thickness and microhardness was studied. The possibility of forming different chemical elements and compounds on the work surface after EDM process was investigated by EDS and XRD analyses. The experimental results revealed that general aspects of surface integrity for machined samples are mostly affected by pulse current and pulse on time. The approximate density of cracks, micro holes and pits on the work surface is intensively dependent on pulse energy variations. Although increase of pulse energy improves the material removal efficiency but leads to increase of average thickness and microhardness of recast layer.