浅析电火花展成加工技术相关问题

本文主要探讨了电火花展成加工,这种特殊的电火花成形加工技术。在介绍电火花展成加工的基本原理和技术特点基础上,对于电火花展成加工的关键技术和加工中影响工艺指标的因素进行分析,说明了电火花展成加工发展前景。     

气体静压球轴承的静特性分析及其实验研究

针对空气静压球轴承雷诺方程求解困难的问题,应用Matlab PDE工具箱提出了一种比较方便的数值求解方法,该方法通过坐标变换将气体润滑三维球面展成二维矩形平面,再将球面轴承的Rey-nolds方程变换成标准的椭圆型偏微分方程形式,进而以Matlab PDE工具箱为求解器,编制迭代计算程序,对其静特性进行计算。并研制了一套基于空气静压球面轴承的主轴样机对数值仿真结果进行验证,结果表明该方法比较理想,该方法在流体润滑领域有一定的应用前景。     

回转式电火花展成加工技术的现状与发展趋势

基于回转式电火花展成加工技术原理及其特点,分析其发展现状,并评述了回转式电火花展成加工在加工理论、设备开发及控制技术等方面的发展趋势。     

球面螺旋齿轮构形原理的研究—内齿轮展成滚刀的造型

本文提出一种球面螺旋齿轮,其特征为:投影是一个齿轮。当球面螺旋齿轮作回转运动时,其投影齿轮也作相应回转运动,并保持投影齿形不变。本文用这种球面螺旋齿轮构形原理为理论基础对内齿轮展成滚刀进行了造型。内齿轮滚刀对提高大模数内齿轮的加工精度与效率有很大意义。但是这类滚刀通常都设计成按成形原理加工的定装滚刀,使用不很方便。为了能设计出按展成原理工作的内齿轮滚刀,本文提出了一种球面螺旋齿轮,并研究了其构形原理,以它为理论基础对内齿轮展成滚刀进行了造型。     

球面剪叉可展机构的运动特性分析

为揭示任意个球面剪叉单元构成的球面可展机构的运动特性,研究这类机构的自由度特性和运动分析方法。基于螺旋理论分析球面剪叉单元及其串联运动链、多支链构成的球面可展机构的自由度特性,得出由球面剪叉单元构成的球面剪叉可展机构的自由度特性,据此构造出任意个球面剪叉单元和任意个支链构成的自由度为1的球面可展机构。基于球面几何理论,对两个球面剪叉单元串联的球面可展机构进行运动分析,并对任意m个球面剪叉单元串联的球面可展机构进行运动分析,在此基础上分析n个支链的球面剪叉可展机构的运动特性。建立球面剪叉可展机构这类机构通用的运动分析方法,并给出运动分析的数字实例,证明了该方法的有效性。编制能满足任意个球面剪叉单元构成的球面可展机构的运动分析软件,实现了对这类机构运动的自动分析计算,具有工程应用的实际意义。     

精密电火花加工机床四轴三联动数控系统的研制

论述了精密电火花加工机床数控系统软、硬件的设计。该系统以一台 ４８６ 系统机为主机和４ 片 ８０３１ 单片机为从机组成主从式控制系统实现四轴三联动功能, 并采用步进电机细分驱动技术,在电火花机床上实现了小于 ０．１μｍ 的脉冲进给。该机床还具有多种摇动功能, 可修光或加工锥面和球面。因而可用于各种难加工零件的精密电火花加工。     

电极摇动对模具型腔加工的影响与补偿研究

研究了电火花加工中电极的各种摇动方式对加工结果的影响，对常用的摇动方式进行了分类，并针对性地分析了对电极的补偿原理，提出了不同的解决方法；对于球面摇动问题，完全可以采用现有ＣＡＤ／ＣＡＭ软件的功能解决，而对于矢量或平面圆摇动问题，则必须通过对产品造型或加工刀轨进行修正解决。给出了两个修正实例。     

超声混粉电火花加工热力学仿真及表面形貌研究

为了研究超声振动和混粉对电火花加工的影响,基于传热理论,结合超声和混粉特性建立了超声混粉电火花传热模型。基于建立的传热模型对超声混粉电火花加工去除材料过程进行瞬态热力学仿真,并通过实验验证了仿真结果的准确性。通过仿真和实验分析了普通电火花、超声电火花、混粉电火花和超声混粉电火花四种加工方式,结果表明超声混粉电火花加工效率比普通电火花加工效率提高了23%。加入混粉和施加超声可以减少加工表面积碳,提高表面质量;可以使放电凹坑变得更加规则,使表面粗糙度降低。混粉电火花加工相对于普通电火花加工其表面粗糙度平均降低了8.9%,超声混粉电火花表面粗糙度相对于普通电火花平均降低了4.3%。     

齿轮模具电火花展成加工电极的研究

齿轮模具电火花展成加工方法具有不受被加工齿轮模具硬度及内齿结构的限制,无加工锥度,能均化各齿的加工误差等优点.在齿轮模具电火花展成加工中,电极是影响加工精度的重要因素,目的是对电极的参数计算及结构设计进行研究.在考虑放电间隙、电极损耗等因素的基础上,对电极齿轮的主要参数进行了修正.设计了对其他电火花加工方式也有参考意义的针对火花放电处局部、均匀、压力供液的内喷工作液装置,及无需更换电极一次完成半精、精加工的长电极结构.     

放电位置随机分布的电火花线切割加工仿真模型

在电火花线切割单脉冲放电过程仿真的基础上,基于有限元软件ANSYS提出了一种放电位置随机分布的电火花线切割加工温度场仿真模型。在仿真过程中,放电位置随机分布,并引入"生死单元技术"去除高温蚀除的单元,得到了线切割连续脉冲放电加工过程的表面效果。然后利用温度场仿真结果计算不同放电参数下的材料去除率,并基于脉冲利用率和电极丝换向时间进行修正,发现修正后材料去除率仿真结果与实际加工结果之间误差小于10%,验证了电火花线切割加工连续脉冲随机放电的仿真模型的准确性。其中,电火花线切割加工过程的脉冲利用率、电极丝换向时间是导致仿真结果出现偏差的主要因素。为了分析实际加工过程的脉冲利用率,搭建了脉冲利用率检测装置,对不同伺服条件下的脉冲利用率进行了统计。     

对线切割断丝现象的分析及对策

电火花线切割技术在模具制造业发展中的应用越来越普及,但常常会由于各种原因引起电极丝在加工中产生断丝现象。本文针对此现象分析了断丝产生的原因及解决方法,使加工得以顺利进行,提高了加工效率及加工质量。     

Non-linear mechanism in electrical discharge machining process

Electrical discharge machining (EDM) is an advanced non-traditional manufacturing technology that has many advantages over other machining methods. Many papers have discussed the machining mechanism and modeling of the EDM process. However, previous mechanism models have mainly been linear, which contradicts their precondition that EDM is a stochastic process. In this paper, a non-linear mechanism model is proposed for the EDM process. A threshold condition that leads to chaos is calculated using the Melnikov theory. The theoretical results indicate that the EDM system can generate varied chaos in the evolution of electrical discharge. To verify this conclusion, validation experiments are implemented. Several sets of complete EDM processes’ real-time series are analyzed by multiple chaotic numerical criteria, including power spectrum analysis, principle component analysis (PCA), correlation dimension analysis, and Lyapunov exponent analysis. The experimental results provide further qualitative and quantitative evidence that a complete EDM process has dynamical chaotic characteristics.     

电火花加工机床(EDM)的新进展及市场分析--美国芝加哥国际制造技术展(IMTS2002)EDM评述

通过IMT2002展出的低速走丝电火花线切割机床（LSWEDM），数控电火花成形机床（NCSEDM），高速小孔电火花加工机床（HSEDM）的新产品，新技术、新工艺介绍，结合我国情况对EDM市场进行了分析。     

混粉大面积电火花加工机理的分析

根据电火花加工原理和特点,分析了传统大面积电火花加工很难获得良好粗糙度的原因,同时探讨了混粉电火花加工改善大面积加工表面粗糙度的原因,并用实践验证了混粉电火花加工能改善加工表面粗糙度     

Assessing the effects of different dielectrics on environmentally conscious powder-mixed EDM of difficult-to-machine material (WC-Co)

Electrical discharge machining (EDM) is a well-known nontraditional manufacturing process to machine the difficult-to-machine (DTM) materials which have unique hardness properties. Researchers have successfully performed hybridization to improve this process by incorporating powders into the EDM process known as powder-mixed EDM process. This process drastically improves process efficiency by increasing material removal rate, micro-hardness, as well as reducing the tool wear rate and surface roughness. EDM also has some input parameters, including pulse-on time, dielectric levels and its type, current setting, flushing pressure, and so on, which have a significant effect on EDM performance. However, despite their positive influence, investigating the effects of these parameters on environmental conditions is necessary. Most studies demonstrate the use of kerosene oil as dielectric fluid. Nevertheless, in this work, the authors highlight the findings with respect to three different dielectric fluids, including kerosene oil, EDM oil, and distilled water using one-variable-at-a-time approach for machining as well as environmental aspects. The hazard and operability analysis is employed to identify the inherent safety factors associated with powder-mixed EDM of WC-Co.     

电火花机床主轴头的模态分析与减振设计

针对某机床厂生产的SH50电火花机床在实际工作中主轴头振动较大的问题,通过实验测试和有限元仿真相结合的方法,分析了主轴头的模态特性,并通过测试主轴头的工作振型(operating deflection shapes,简称ODS),找出了主轴头实际工作中的薄弱环节。理论模态、实验模态和ODS三种结果相互印证,增加了有限元模型的可信度,并以此模型为基础对主轴头进行了减振设计。模态实验中改进了传统模态实验依靠经验选取测点或均匀布点时,对经验高度依赖且实验效率较低的弊端,采用有效独立法和模态置信度(modal assurance criterion,简称MAC)矩阵相结合的方法,实验前先进行测点优化,然后根据优化结果布置传感器和力锤位置,提高了模态实验的精度和效率。结果显示,在主轴头结构上增加一个背板,能够提高主轴头频率,远离工作频率的共振范围,起到减振的目的。     

Performance of sinking EDM electrodes made by selective laser sintering technique

Electrical discharge machining (EDM) is a nonconventional machining process widely applied for the manufacture of intricate shapes in hard materials which are not easily machined by conventional machining processes. The production of geometrically complex EDM electrodes is difficult, time consuming, and it can account for about 50 % of the total process costs. Selective laser sintering (SLS) can be an alternative technique to produce EDM electrodes in a faster way. This work conducted an experimental study on the performance of EDM electrodes made by SLS using pure copper, bronze–nickel alloy, copper/bronze–nickel alloy, and steel alloy powders. Important EDM performance measures such as material removal rate and volumetric relative wear were investigated and discussed for finishing, semifinish, and roughing regimes. This work contributes with an insight into the production of EDM electrodes via selective laser sintering, as an alternative technique to conventional machining processes, as well as to evaluate the performance of the electrodes, and also provide directions for future research on this field.     

数控电火花成型机的自适应控制技术研究

针对数控电火花成型机中电火花加工间隙放电过程难以控制的问题,提出基于电火花加工间隙状态的识别和合理的伺服进给系统的电火花自适应控制技术。通过正确的间隙检测方法,配以专家系统和决策控制软件,保证数控电火花成型机的工作可靠和安全,并使长期无人控制操作成为可能,从而为数控电火花成型机的自适应控制技术研究提供了理论依据。     

Rapid tooling aided by reverse engineering to manufacture EDM electrodes

The present work deals with the application of indirect rapid tooling (RT) technology to manufacture electrical discharge machining (EDM) copper electrodes from investment casting, with wax prototypes made by ThermoJet 3D printing, a rapid prototyping (RP) technique. The reverse engineering (RE) method is utilised to transform the point cloud data of an object surface, obtained from 3D digitising, in a 3D CAD surface model dataset. The methodology presented is fundamental to verify the prototype’s geometry for tooling so as to assure its metrological accuracy and to optimise foundry process parameters using finite element analysis (FEA). Based on a case study, some functional conclusions are presented for the application of RT in manufacturing EDM electrodes aided by 3D digitising and RE, validating the accomplishment by the integration of these technologies and methodologies in EDM manufacturing processes.     

Artificial neural network model in surface modification by EDM using tungsten–copper powder metallurgy sintered electrodes

Electro-discharge machining (EDM) is a widely accepted nontraditional machining process used mostly for machining materials difficult to machine by conventional shearing process. Surface modification by powder metallurgy sintered tools is an uncommon aspect of EDM. Of late, it is being explored by many researchers. In the present paper, attempts have been made to model the surface modification phenomenon by EDM with artificial neural networks. Two output measures, material transfer rate and average layer thickness, have been correlated with different process parameters and presented in the form of plots. The predicted results are matching well with the experimental results.