数控电火花加工技术在航空航天领域的应用与展望

介绍了数控电火花加工技术在国内外航空发动机、航天运载火箭、空间飞行器等领域的应用情况.重点介绍了多轴联动数控电火花成形加工技术在航空航天发动机的核心部件-整体涡轮盘研制中所发挥的关键作用,分析了数控电火花微细加工技术在航天领域的应用前景.     

六轴四联动聚晶金刚石电火花镜面加工机床的关键技术研究

为聚晶金刚石的高精度加工研发了一种新装备,其关键技术的研究主要包括:六轴四联动电火花加工数控系统;专用脉冲电源系统;高精密和高响应性的放电伺服系统;专用数据库及专用机床。六轴四联动聚晶金刚石电火花镜面加工机床的研发能给企业带来更多的商机和效益,推动高效、高速、高精度刀刃具的发展。     

叶盘流道五轴高效复合放电加工机床及其数控系统设计

高速放电铣削加工在航空航天材料加工领域有广阔的应用前景。在叶盘加工中,高速电弧铣削粗加工与电火花成形精加工的结合应用已初步显现出高效率、高精度的潜力,但现有解决方案仍存在工艺衔接困难、集成度低的实际问题。对此,采用模块化思想,设计了使用水基工作介质、集成上述两种加工方法的五轴复合放电加工机床。以Windows电火花数控系统为基础,开发双模式放电加工多轴数控系统,实现了两种加工方式的数据共享和便捷切换。结果表明:该复合加工机床加工TC4钛合金时的平均材料去除率可达到2160 mm~3/min,经过水基介质成形加工后的表面粗糙度Ra2.7μm,能满足叶盘零件加工需求。     

闭式整体涡轮叶盘多轴联动电火花加工电极运动路径规划

多轴联动电火花加工作为闭式整体涡轮叶盘的主流加工方法,其电极运动路径规划至关重要。为此,提出了一种电极运动路径规划的方法,使电极尽可能沿涡轮叶盘流道中心曲线运动,获得电极的最佳位置姿态。基于该方法,对某闭式整体涡轮泵叶轮进行了电极设计与电极运动路径规划,加工试验结果证明了该方法在加工效率与成本上的整体优势。     

基于PMAC的商用五轴联动电火花加工数控系统

研制了一种基于可编程运动控制器PMAC的五轴联动电火花加工数控系统。其采用全闭环速度模式的控制体系,具备实现电火花成形加工控制中包括间隙电压检测、伺服进给回退运动、多轴联动、主轴高速抬刀运动及各类摇动等的多项关键技术。该数控系统已应用于商用五轴联动电火花成形加工机床,通过大量的样件加工实验,验证了其良好的控制与加工性能。同时按商业化标准完善了数控系统,推动了其产业化进程。     

五轴联动数控电加工技术研究

为了解决难加工材料复杂形状零件的精密加工问题,基于电解-机械复合加工原理,研究开发了五轴联动数控电解机械复合加工机床,组合引进了五轴联动数控电火花成形机床和五轴联动数控单向走丝电火花线切割机床。采用五轴联动数控电加工技术,可实现整体叶轮、窄槽、窄缝、深腔、异形盲孔、内腔侧向盲孔等特殊复杂形状加工的工艺要求,加工精度优于±0.003 mm。     

我国特种加工行业2014年十件大事

一、数控机床重大专项电加工新一轮课题实施
　　◆精密、高效、数控单向走丝电火花线切割机床：
　　（1）高效数控单向走丝电火花线切割机床;
　　（2）七轴联动数控电火花高速小孔加工机床;
　　（3）新一代飞机钛合金格栅网板数控电火花高效加工技术及专用机床。
　　◆航天复杂零部件超精密微细电火花加工装备与技术：
　　（1）大型精密六轴联动数控电火花成形机床;
　　（2）航天复杂零部件超精密微细电火花加工装备与技术。
　　◆电加工关键技术及工艺数据库与数控系统集成开发。     

涡轮静子电火花电弧复合加工工艺研究

航天发动机的涡轮静子是一种集合了闭式整体叶盘难加工结构和高温合金难加工材料于一体的复杂零件。针对该涡轮静子加工效率较低、制造成本昂贵等难题，提出一种电火花电弧复合制造这类零件的方法。首先，采用高速电弧加工方法对高温合金进行工艺试验，分析不同工艺参数下的工件加工效率、表面粗糙度、再铸层和热影响层等方面的变化规律；然后，以高温合金涡轮静子为加工对象，开展电火花电弧复合工艺研究，以实现产品的高效精密加工。结果表明：与单一的电火花成形加工相比，采用电火花电弧复合工艺加工涡轮静子的加工效率提高了52%。     

电火花成形加工数控系统研制与实验研究

针对目前国内电火花成形加工数控系统精度不高、稳定性较差的现状,在广泛调研的基础上,采用PC机与NC板相结合的方式,自主开发出了以PC机与Windows操作系统为顶层控制系统,PCI桥接芯片、DSP与FPGA为底层控制系统的高速高精度电火花数控系统。实现了具备平面摇动与三维摇动、中心抬刀与非中心抬刀的多轴联动摇动加工功能,有效提高了电火花数控系统的加工稳定性和加工精度。将数控系统应用于电火花成形机床,进行了不同摇动及抬刀方式的加工实验,验证了数控系统的加工性能,并探索了不同摇动参数、不同抬刀方式对加工效率、精度和稳定性的影响规律。     

电解与电火花复合加工火箭发动机涡轮泵叶珊环的研究

以火箭发动机涡轮泵喷嘴叶珊环为研究对象进行电解与电火花复合加工技术研究，通过对电解预加工的工艺参数分析和试验，并对电火花后处理过程的电极设计和适配性进行研究，实现对具有复杂型面和内部结构的高温合金零件的高效率和高精度加工。     

基于遗传算法的工程陶瓷电火花加工技术

工程陶瓷材料硬脆、导电率低,难以获得高效精密的电加工效果.本文针对工程陶瓷电火花加工特点,在分析国内外工程陶瓷电火花加工技术的基础上,提出了基于遗传算法的工程陶瓷电火花加工方法.该方法结合遗传算法、神经网络及模糊控制理论构造了多环式自适应控制系统,在线对加工过程进行断丝预防、加工工艺自适应和加工参数自适应监测与控制,从而为难加工材料实现高效精密的电火花加工提供理论与技术指导.     

Development of Technology and Strategies for the Machining of Ceramic Components by Sinking and Milling EDM

This paper investigates the manufacturability of B₄C, SiC, Si₃N₄-TiN by milling EDM and the performance of it has been compared to conventional sinking EDM. It is shown that due to the good flushing conditions, milling EDM performs well, even for the machining of ceramic materials with a rather low electrical conductivity (B₄C, SiC). Because the used milling EDM technique removes material in a layer by layer fashion (2D-machining), a new strategy for the machining of complex 3D-shapes in ceramic material has been developed. It consists of a milling EDM pre-machining step, followed by one or more finishing sinking EDM steps. The developed strategy has been validated on an industrial example and compared to a pure sinking EDM strategy. Time reductions of more than 50% were obtained.     

Probability of precision micro-machining of insulating Si3N4 ceramics by EDM

Electrical discharge machining (EDM) is used as a precision machining method for the electrically conductive hard materials with a soft electrode material. But recently we succeeded to machine on insulating material by EDM. The technology is named as an assisting electrode method. The EDMed surface is covered with the electrical conductive layer during discharge. The layer holds the electrical conductivity during discharge. For micro-EDM, the wear of tool electrode becomes lager ratio than the normal machining. So the micro-machining is extremely difficult to get the precision sample.

In this paper to obtain a fine and precise ceramics sample, some trials were carried out considering the EDM conditions, tool electrodes material and assisting electrode materials. Insulating Si₃N₄ ceramics were used for workpiece. The machining properties were estimated by the removal rate and tool wear ratio. To confirm the change of micro-machining process, the discharge waveforms were observed. The micro-machining of the Ø0.05 mm hole could be machined with the commercial sinking electrical discharge machine.     

电火花线切割加工铜钨合金切缝宽度及加工精度影响因素研究

铜钨合金是一种广泛应用于精密及难加工材料电火花成形加工的低损耗电极材料。在窄缝、清棱清角、高纵横比等结构的电极加工中,低速走丝电火花线切割加工较传统加工方法具有一定的优势。通过单因素实验研究了电火花线切割加工参数对铜钨合金粗加工切缝宽度、加工速度及表面粗糙度的影响规律,为实际加工提供理论指导。     

A plate capacitor model of the EDM process based on the field emission theory

The electrical discharge machining (EDM) process is, by far, the most popular amongst the non-conventional machining processes. The technology is optimum for accurate machining of complicated shapes in hard materials, required in the modern industry. However, although a lot of EDM machines are widely applied for many years, fundamental knowledge of the process is still limited. The complex nature of the process involves simultaneous interaction of thermal, plasma temperature and electromagnetism factors, which makes the machining process modeling very difficult. In this paper, based on the analysis of the electric discharge machining (EDM) process, a plate capacitor model is constructed to describe the discharging process in a pulse time. The whole EDM process is divided into four stages, successively as interelectrode electric-field establishment, electric discharge channel formation, stable EDM and deionization, the interaction of each stage and the distribution function of EDM energy are deduced using the field electron emission theory. For the purpose of analyzing the effect of the single factor, a set of machining through-hole experiments were carried out and investigated. The study shows that critical electric-field intensity and the effective discharging time rate play major roles on the improvement of machining efficiency; the model can explain the differences of machining efficiency using different materials of tool pole and different EDM parameters; and the theoretical results are concordant with the experimental data well.     

PZT激励同步压缩放电通道微细电火花加工工艺参数对加工结果的影响

提出了压电陶瓷(piezoelectric ceramic transducer,PZT)激励同步压缩放电通道微细电火花加工,目的在于改善微细电火花加工的放电环境。介绍了PZT激励同步压缩放电通道微细电火花加工原理,研究了开路电压、脉冲宽度、脉冲频率和峰值电流对其电极损耗和材料去除率的影响,并与不采用压缩通道方法的微细电火花加工进行了对比。结果表明:同等条件下,采用PZT激励同步压缩放电通道技术,提高了加工过程的稳定性和材料去除率,降低了电极损耗率,有效改善了放电环境。     

A numerical model of the EDM process considering the effect of multiple discharges

The electrical discharge machining (EDM) process is, by far, the most popular amongst the non-conventional machining processes. The technology is optimum for accurate machining of complex geometries in hard materials, as those required in the tooling industry. However, although a large number of EDM machines are sold every year, scientific knowledge of the process is still limited. The complex nature of the process involves simultaneous interaction of thermal, mechanical, chemical and electrical phenomena, which makes process modelling very difficult. In this paper a new contribution to the simulation and modelling of the EDM process is presented. Temperature fields within the workpiece generated by the superposition of multiple discharges, as it happens during an actual EDM operation, are numerically calculated using a finite difference schema. The characteristics of the discharge for a given operation, namely energy transferred onto the workpiece, diameter of the discharge channel and material removal efficiency can be estimated using inverse identification from the results of the numerical model. The model has been validated through industrial EDM tests, showing that it can efficiently predict material removal rate and surface roughness with errors below 6%.     

电火花线切割大电流条件下电参数对加工性能的影响

为了解决往复走丝电火花线切割加工效率低的问题,对大电流条件下的两种电加工参数进行了研究,在保证平均电流相同的条件下,对小脉宽、大峰值电流和大脉宽、小峰值电流两种加工方式进行对比实验。结果表明:在普通往复走丝电火花线切割机床上,采用大脉宽、小峰值电流加工方式,其加工效率比小脉宽、大峰值电流的高约20%;采用小脉宽、大峰值电流的加工方式能有效地减少工件表面的烧伤,获得表面粗糙度值较小的加工表面。此外还分析了两种加工方式的放电加工机理,从放电通道扩展半径、放电频率和电极间放电状态等角度解释了两种方式的加工效率和表面质量差异。     

CuW90微小孔电火花加工实验研究

利用单因素实验和正交试验法探究了电源电容、电流、伺服参考电压、伺服速度及占空比对CuW90微小孔电火花加工效率和电极损耗的影响。结果表明:伺服参考电压和占空比对加工效率和电极损耗的影响都较大,而电容、电流对其影响较小,最终得到了CuW90电火花微小孔加工的最优参数组合。     

电火花加工放电介质的研究

通过对电火花加工放电通道中等离子体柱的形状和放电通道的电流、电磁特性进行分析,并对电火花加工中不同介质的加工性能进行对比和总结,提出电火花加工介质的技术研究方向应符合绿色制造和资源的可持续发展的理念。