扩压器套料电解加工流场优化设计及实验研究

在电解加工中,合理的电解液流场能改善加工稳定性、提高加工效率。针对扩压器电解加工开展了流场优化研究,设计了流道出液转角式的正冲流动方式,建立了不同进液口转角间隙的流道模型,利用ANSYS进行了流场仿真优化分析。结果表明:在转角间隙值为0.3 mm时,加工区流速分布的均匀性最好,且电解液达到了较高的流速。同时,在转角间隙为0.3 mm时开展了扩压器电解加工提速实验,当阴极进给速度为0.7 mm/min时加工出了轮廓完整且表面光洁的叶片,验证了流场仿真优化的合理性。     

聚磁提高复杂型腔电解加工精度的研究

由于电解加工受电化学、电场、流场等多种因素的交互影响,阴极的形状并不是工件形状的简单拷贝,因此往往要对阴极进行反复修整。为提高七工位复杂型腔电解加工的精度和阴极设计周期,进行了不添加磁场、镶嵌聚磁磁路的电解加工装置及夹具的设计。采用按工件型面等间隙缩小设计的整体阴极进行电解加工试验。经切片测试分析显示,添加聚磁磁路较不加磁场的工件成形精度提高33.3%,表面粗糙度值达Ra0.16μm。结果表明:聚磁技术是减少阴极设计周期、降低成本、提高电解加工精度的一条有效途径。     

异形深孔电解加工过程的流场优化

针对异形深孔电解加工过程中进出口流场突变现象、加工间隙流场分布不均、工艺稳定性相对较差等问题,以深径比12∶1的异形孔零件为研究对象,对加工开始、加工稳定、加工穿透各个阶段流场分布进行仿真优化研究。通过导流结构、多孔通液阴极结构保证电解加工进出口流场平稳性;采用合理的电解液压力、复合进给加工模式等措施改善流场分布均匀性,避免空穴现象。基于流场仿真优化结果,开展了异形深孔连续电解加工试验,孔尺寸精度可控制在0.03 mm。     

航空铝合金高效精密电解铣磨加工试验

基于电化学溶解与机械磨削的复合作用对工件材料大余量去除的技术上,提出了针对航空铝合金的电解铣磨加工方法。试验研究表明:与电解铣削加工相比,电解铣磨加工可获得更高的加工速度,材料去除率从160.64 mm~3/min提升至192.58 mm~3/min,侧面平整度从434.1μm减至274.1μm,底面平整度从1154.1μm降至610.5μm。此外,在电解铣磨精密加工阶段后,侧面平整度的数值从274.1μm进一步降至77.4μm,表面粗糙度从Ra1.373μm减至Ra0.539μm。     

直齿面齿轮高精度电解加工阴极整体结构设计方法研究

针对传统展成法加工直齿面齿轮周期长、成本高及成形法批量生产存在的质量精度低等现象,提出一种高精度直齿面齿轮电解加工阴极整体结构设计方法。首先,根据直齿面齿轮的齿面方程,利用截面放样法对齿面建模点进行合理规划,并基于网格划分方式,利用平衡间隙设计理论建立相应的阴极刀具型面模型;其次,采用反流式设计阴极流道以提高工作效率及加工精度;最后,在设计阴极刀具型面和流道型腔结构的基础上,设计了一体化电解加工装夹系统。通过电解加工直齿面齿轮的加工实验,获得了表面粗糙度值小于Ra1.6μm、综合精度为IT9级的直齿面齿轮制件,从而验证了该设计方法的可行性。     

高效精密电解铣磨加工Al-SiC铝基复合材料的流场仿真与试验

提出Al-SiC铝基复合材料的电解铣磨加工方式,以直径10 mm、切深15 mm的工具阴极基体设计3种排数的出液孔,通过流场仿真建模及计算,优选出流速分布最均匀的工具阴极基体,并在基体表面进行电镀金刚石处理。在电解铣磨加工试验时,首先对工件进行高效粗加工,随后进行精密加工。结果表明:加工所得的工件沟槽侧壁平整度平均改善了0.56 mm,沟槽侧壁粗糙度值从Ra3.660μm降为Ra1.933μm,材料去除率达到255.9 mm3/min。     

提高航空发动机叶片反拷法电解加工精度的实验研究

反拷法电解加工涉及不可逆的二次电解加工过程,加工精度很难控制,无法满足航空发动机叶片的制造需求。在分析反拷法电解加工误差产生原因的基础上,以提升加工精度为目的,提出了小加工间隙反拷法电解加工方法。以加工典型的航空发动机叶片为例,开展不同加工间隙条件下的反拷法电解加工对比实验,结果表明:加工间隙由拷贝工具0.49 mm/反拷工件0.53 mm减小至拷贝工具0.23 mm/反拷工件0.23 mm,叶片型面轮廓精度由0.14 mm提升至0.05 mm,该结果验证了提出方法的有效性。     

超声振动复合研磨K9光学玻璃工艺研究

目的探究超声振动复合研磨对光学玻璃研磨可行性,通过响应面法寻求超声振动研磨最优的工艺参数组合。方法在传统研磨装置基础上,添加超声振动装置、蠕动泵、旋转工作台构成超声振动复合研磨装置。添加轴向超声高频振动提高研磨效率,添加旋转工作台提高研磨均匀性,添加蠕动泵便于循环和更新研磨液。利用响应面法优化超声振动复合研磨加工中的主轴转速、振动频率、加工间隙三个变量参数,并进行实验研究,可得出两两变量关联度,从而得出研磨中影响最大的因素。结果通过响应面优化后得到超声振动复合研磨最佳工艺参数为主轴转速1000 r/min、加工间隙0.4 mm、振动频率12 kHz,主轴转速和间隙参数对工件表面研磨加工的影响较大。经25 min研磨,无超声振动的传统研磨方法使表面粗糙度值Ra从0.3μm下降到0.1μm;增加超声振动复合研磨使表面粗糙度值Ra从0.3μm下降到0.04μm。结论经超声振动复合研磨后,光学玻璃表面存在的凹坑、凸起均得到了有效去除,表面粗糙度值下降快,表面形貌均匀、平整。     

复合轨迹电解磨料加工实验研究

本文论述了电解磨料镜面加工机理,分析了各主要参量对加工的影响规律,用正交实验法优化出较佳工艺参数。为消除加工表面不均匀性,利用计算机模拟复合轨迹加工,并根据模拟结果进行电解磨料加工实验。研究表明,复合轨迹电解磨料加工是高效率、高质量镜面加工手段,可将Ra2.0μm不锈钢冷轧板直接加工成Ra0.02μm均匀镜面。该工艺在机械、化工、能源、航空等领域有广阔的应用前景。     

钛基复合材料内孔电解铣磨精加工试验研究

钛基复合材料由于存在增强相，故为典型的难加工材料。针对（TiC+TiB）/TC4钛基复合材料内孔开展了电解铣磨精加工试验，结果表明：在电解铣磨精加工0.2 mm后，孔侧壁表面能观察到明显的金属光泽和磨削痕迹，侧壁面的表面粗糙度由Ra14.851 5μm降低至孔口区域Ra0.441 3μm、孔中间区域Ra0.617 6μm。     

Study of precision ECM in stationary electrolyte using stamp flushing method

In the interelectrode gap of ECM, the electrolyte flow results in ununiformly distributed temperature and volume fraction of bubbles, leading to uneven distribution of the gap width. This paper aimed to realize high precision ECM using stationary electrolyte. A single current pulse was supplied after every jump flushing motion of the tool electrode. The pulse duration used was set sufficiently short not to cause the boiling of the electrolyte. Furthermore, the stamp flushing method was newly developed to squeeze out the sludge and bubbles from the gap to achieve high precision machining.     

基于Taguchi方法的钼栅网微细光刻电解试验研究

影响钼栅网电解加工尺寸均一性的因素有电解液浓度、电流密度、阴极直径以及极间间隙等.利用Taguchi方法对这些因素进行综合分析及试验验证,阴极直径和极间间隙作用显著.通过ANSYS软件对电解过程中的电场进行分析,得出了阴极直径和极间间隙大小的改变对阳极表面电场的影响规律.在此基础上,采用酸性活化电解液对钼栅网进行微细光...     

型孔电解加工阴极优化试验研究

为解决电解加工型孔的加工稳定性和形状精度等问题,建立了异形孔电解加工稳定过程中加工间隙数学模型,分析了工具阴极结构对加工区域和非加工区域的电场及其均匀性以及其对电流密度与加工效果的影响,通过优化工件结构改善了加工间隙内的电场分布,使工件形状精度显著提高,并进行相关试验对仿真结果进行验证。得出结论:在相同的电解加工参数下,工具电极的结构对工件的形状精度有着显著的影响,通过优化工具电极结构,改善加工间隙内的电场分布与电流密度,让加工间隙内的流场更为稳定,使工件侧壁垂直度提高,提高了电解加工的形状精度与加工稳定性。     

Machining characteristics of magnetic force-assisted EDM

The gap conditions of electrical discharge machining (EDM) would significantly affect the stability of machining progress. Thus, the machining performance would be improved by expelling debris from the machining gap fast and easily. In this investigation, magnetic force was added to a conventional EDM machine to form a novel process of magnetic force-assisted EDM. The beneficial effects of this process were evaluated. The main machining parameters such as peak current and pulse duration were chosen to determine the effects on the machining characteristics in terms of material removal rate (MRR), electrode wear rate (EWR), and surface roughness. The surface integrity was also explored by a scanning electron microscope (SEM) to evaluate the effects of the magnetic force-assisted EDM. As the experimental results suggested that the magnetic force-assisted EDM facilitated the process stability. Moreover, a pertinent EDM process with high efficiency and high quality of machined surface could be accomplished to satisfy modern industrial applications.     

Modeling of nonstationary EHD flows in a wire-plane electrode system

The object of this work is nonstationary EHD flow modeling in a wire-plane electrode system for researching processes of space-charge formation and evolution, and the features of its movement in the interelectrode gap are investigated. The set of equations describing the modeling process is appreciably nonlinear. The final-element modeling package ANSYS was used for solving this problem. A special algorithm was developed. It was realized as a package of programs based on the approximation that the charge is “frozen” in the liquid. Results of calculations are represented as velocity vector plot evolution, pressure distributions, and EHD flow traces. A typical feature of EHD flow is the formation of a charged thin stream that crosses the interelectrode gap.     

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.     

Efficiency improvement in electrical discharge machining (EDM) of constant section cavity based on experimental study and numerical calculations

Electrode jump motion is applied to most of the electrical discharge machining (EDM) machine to remove debris from machining gap. The time consumption of one consecutive-pulse discharge process between two adjacent electrode jump motions is named electrode machining time. If the two parameters can be timely adjusted to the optimal values during machining, the efficiency will be obviously improved. However, the complicated flow field of the machining gap that contains kerosene, debris, and bubbles makes it difficult to determine the optimal values of electrode machining time and jump height. This research proposes a strategy to solve this problem. By detecting the voltage and current signals between electrode and workpiece, the normal discharge frequency and abnormal discharge ratio were calculated to determine the optimal electrode machining time. Then, the optimal electrode jump height was calculated through a model which simulates the gap flow field in EDM. Experimental results show that the proposing strategy evidently improves the EDM efficiency.     

Monitoring and control of the micro wire-EDM process

A new pulse discriminating and control system has been developed for process monitoring and control in micro wire-EDM. The pulse discriminating and control system identifies four major gap states classified as open circuit, normal spark, arc discharge and short circuit based on the characteristics of gap voltage waveform. The effect of pulse interval, machining feedrate and workpiece thickness on the variations of the proportion of normal spark, arc discharge and short circuit in the total sparks (defined as normal ratio, arc ratio and short ratio, respectively) were investigated. It is found that a long pulse interval results in an increase of the short ratio under a constant feedrate machining condition. A high machining feedrate or an increase of workpiece height results in an increase of the short ratio. To achieve the stability of the machining operation, a control strategy is proposed by regulating the pulse interval of each spark in real-time according to the identified gap states. Experimental results indicate that the developed pulse discriminating and control system can significantly reduce the arc discharge and short sparking frequency as well as achieve stable machining under the condition where the instability of machining operation is prone to occur.     

Parametric control for optimal quality of the workpiece surface in ECM

The authors have successfully designed and developed an Electrochemical Machining set-up with a microprocessor-controlled stepper motor drive control unit for providing variable and automatic tool feed rates and also with an electronic circuit for auto-sensing of changes of the ECM gap condition during the course of machining, so as to actuate the auto-feedback control of the tool feed-rate and thus secure constant current Electrochemical Machining.

The present paper also highlights various research results with the auto-feed ECM system for analysing the effect of some of the process variables, e.g. the electrolyte flow rate, the electrolyte concentration, the current density and the applied voltage, on the various surface-roughness parameters and bearing properties of the machined surface, as measured with the help of a computerised Talysurf unit. The test results indicate clearly the optimal parametric combinations that are needed for enhanced metal removal and better surface finish and other surface topographical characteristics, with the present design of auto-tool-feed control. It is evident from the test results that the present study on ECM will be quite useful and a step forward for proceeding with further applied research for achieving effective utilisation of ECM in practice, with better surface-quality characteristics so as to meet the needs of modern manufacturing industry.     

电火花成型加工蚀除位移控制方法的研究

通过对电火花成型加工放电蚀除规律的分析,提出了一种符合实际应用的控制策略,在粗加工情况下,以控制间隙电压稳定为主要目标,加工位移作为观测量;在精加工情况下,只要选取合适的分析周期,使在分析周期内的加工位移小于工件的加工精度,则仍以控制间隙电压稳定为主要目标,加工位移作为观测量,当加工位移与理想位移最接近时,停止加工。采用上述控制方式有效地避免了由于间隙电压与加工位移之间的耦合关系而导致的控制系统复杂性。该系统软件结构简单、实用,具有很强的工程应用价值,通过与传统控制方法的运行结果进行对比,结果表明机床的加工效率显著提高。