Experimental study on ECM with a grid cathode composed of circular cells

In order to resolve the problem of single machining object existing in traditional electrochemical machining (ECM) with unitary cathode, a grid cathode composed of circular cells is used to produce the workpieces with different shapes. Three types of circular cells, ??1.5 mm, ??2.0 mm, and ??2.5 mm, are utilized to construct the plane, slant, and blade cathode. The material of the cathode and the anode is CrNi₁₈Ti₉, and the ingredient of electrolyte is 15% NaCl and 15% NaNO₃. The machining balance current and the balance time are acquired and analyzed, the machining process and the workpiece quality are compared between using the grid cathode and the unitary cathode. Moreover, the machining errors and the error reasons of workpiece surface are analyzed. Research shows that the grid cathode can be used to manufacture workpieces with a complex shape, and the workpiece quality is better if the circular cell is smaller. If the circular cell is small enough the workpiece quality is almost equal to it machined by the unitary cathode.     

A NEW METHOD FOR MACHINING OF ELECTRICALLY NONCONDUCTIVE WORKPIECES USING ELECTRIC DISCHARGE MACHINING TECHNIQUE

In this study, a new method for machining of nonconductive ceramic workpieces in electric discharge machining (EDM) was developed. Machining surfaces of nonconductive workpieces were coated with a conductive layer (CL) and graphite powder was added to dielectric fluid for machining. Al₂O₃, ZrO₂, SiC, B₄C and glass workpiece samples were machined by using the method. Different machining conditions were tested for each sample and optimum machining parameters were determined. Effect of electrical conductivity, thermal conductivity and melting point of workpieces on material removal rate (MRR) was investigated. Optical microscope and SEM (Scanning Electron Microscope) surface photographs of workpieces taken after machining are presented and discussed.     

钛合金曲面磨粒流加工扰流流道仿真与试验研究

针对具有复杂曲面的钛合金工件磨粒流抛光后表面粗糙度Ra不均匀问题,提出一种具有扰流结构的仿型约束加工流道。借助计算流体动力学（CFD）分析软件,结合SST k-ω湍流模型、离散相模型（DPM）和Oka冲蚀模型,仿真分析原始流道和5种不同扰流角度的扰流流道内磨粒流动力学特性。数值模拟结果表明：扰流流场中的磨粒流相较于原始流场在工件表面具有更大的湍流动能、动压力和冲蚀速率,其中扰流角度为30°时冲蚀均匀性较好。基于仿真条件搭建了磨粒流加工试验平台,使用原始流道和30°扰流流道分别进行了加工试验。试验结果表明：使用原始流道加工5 h后,工件表面曲率不同区域的表面粗糙度Ra值分散,加工效果均匀性较差;使用扰流流道加工5 h后,工件表面各区域表面粗糙度Ra的均匀性明显优于无扰流流场的加工均匀性。     

两步法电化学加工薄壁钼长管的数学建模与实验研究

针对某反应堆用高温燃料包壳加工难题，研究了钼合金薄壁长管部件的电化学加工技术，提出了固定阴极及移动阴极的两步电化学加工方法，建立了移动窄阴极电化学加工的数学模型，针对实施方式、工艺参数等进行了实验。实验结果表明：固定宽电极的电化学加工可大量去除材料，移动窄电极的电化学加工可进行表面精修，采用这两种工艺对直径25.4 mm、长度800 mm的钼管进行加工，获得的直径偏差在0.05 mm以内。     

渐开线内花键电解加工流场设计及工艺稳定性研究

为进一步提高渐开线内花键电解加工的工艺稳定性,基于数值分析方法探讨了电解液流动方式、工具阴极结构、电解液参数对流场分布的影响规律。数值分析结果表明：电解液侧向流动可以改善加工区入口处电解液流速分布均匀性;带有导流段的变截面阴极能够降低工件表面流速波动。针对工艺稳定性及加工定域性,开展了渐开线内花键电解加工试验研究。试验结果表明：进给速度可达2.1 mm/min以上,齿形误差可控制在0.015 mm以内,当加工深度为30 mm时,齿向误差在0.02 mm以内。该加工方式的效率及精度能够满足很多实际需求,具有明显的技术经济优势。     

Vibration assisted wire electrochemical micro machining of array micro tools

Micro structures and components are widely used in modern industries, and micro machining has therefore become a popular research topic. As micro tools are essential in micro machining, wire electrochemical micro machining is introduced in the fabrication of micro tools in this paper, and micro square column tool arrays are fabricated using wire cathodes by two steps. In order to improve the machining efficiency and quality, an electrode vibration technique is used, and the effects of bubble behaviour on slit width homogeneity and edge radius are studied through simulations of the electric field. The influences of various machining parameters such as vibration conditions, electrical properties, electrolyte concentration and feedrate on the standard deviation of the slit width and on the value of the edge radius are investigated. In addition, the micro dimple array is fabricated using electrochemical micro machining by employing the micro square column tool array as the cathode.     

嵌入磁路的电解加工技术

为提高电解加工精度,基于磁场和电场相互作用原理,设计了两种镶嵌磁路的阴极。分析了磁场对双电层液相3种传质方式的影响,提出将多极内封闭渐变磁路和多极外封闭渐变磁路组合后嵌入电解加工装置的方法。试验表明,沿阴极体周边均匀镶贴永磁体的阴极,加工时磁力线与电解液流动方向正交,可消除分股束流、空穴, 改善电解加工流场,改善工件表面粗糙度;顺阴极轴向在阴极头内嵌入永磁体,加强了反应物质向加工区传质的速度,提高了集中蚀除的能力,可有效减轻杂散腐蚀。对电解套料沿阴极内壁采用多极内封闭渐变磁路镶贴永磁体;对非铁异形孔加工,为进一步加强间隙磁场,可采用在阴极外表面镶嵌多极外封闭渐变磁路,在工件外套一多极内封闭渐变磁路形成组合磁场。     

影响工件车削加工质量的因素分析

在机械加工过程中,影响工件的最终加工质量的因素有很多种.工件加工质量的高低是决定其使用性能好坏的重要因素.通过对工件车削加工质量影响因素的分析,找到如何使工件的加工达到质量技术要求的措施,既保证工件表面的加工质量,又避免增大零件的制造成本,造成不必要的损失.     

空气中微细电火花沉积与去除可逆加工技术研究

论述了一种新的电火花加工方法。它使用通用的电火花成形加工机床,利用常见的电极材料,在空气介质中,通过脉冲放电在工件表面上沉积生长电极材料,再通过反转极性和适当的轨迹控制对所生成的沉积材料进行有选择的去除加工,进而实现材料的生长与去除可逆加工。通过对电火花加工理论的研究,预测和论证了实现这一新加工方法的可能性和实现条件。通过试验成功地将钢、铜和钨三种电极材料沉积到工件上,形成直径为 100~240 mm、高度为1 000~2 500 mm的微小圆柱体。并对沉积物进行了选择去除,实现了在同一设备上的可逆电火花加工。对沉积材料的致密性、硬度及其与工件的结合强度等进行了系统的分析,表明沉积物组织致密、坚硬,可以满足功能材料的要求。     

面向加工变形控制的航空整体结构件拓扑优化设计方法

在毛坯制造过程中,材料力学性能的非均匀性导致铝合金厚板内产生残余应力,以致在后续的高速切削加工过程中,随着材料的大量去除,残余应力的释放使得整体结构件发生变形,严重影响着整体结构件的尺寸稳定性。当初始残余应力水平及状态一定时,随着从毛坯上去除材料切削成形为不同的零件结构,零件变形会表现出不同的形式。因此,研究零件变形与零件结构形式之间的关系对于实现加工过程的高效化和精密化至关重要。首先,通过铝厚板的材料去除等效为残余应力的释放,利用弯曲变形理论建立铝厚板厚度方向上加工变形的解析分析模型及有限元分析模型。通过航空企业现场加工、测试零件后可知：加工变形的解析值、仿真值与测量值相比,无论是幅值水平还是变形曲线,解析值与仿真值完全吻合,而两者与实验值之间仅存在不到10%的幅值误差。其次,为了使得加工变形达到最小,构建以结构体积为约束的拓扑优化设计模型,通过利用一系列凸显式子问题逼近目标和约束函数,构建拓扑优化模型的MMA求解技术。最后利用所提出的优化方法计算出C919直梁件的结构,优化前、后的加工变形分别为22.02 mm与0.7414 mm,在相同的材料去除量情况下,通过优化结构可以使得加工变形减小96.63%。     

切削加工残余应力的有限元分析

在切削加工中,为了提高已加工工件的表面质量,需要研究切削速度和进给量对已加工工件残余应力的影响规律。根据弹塑性有限元理论,利用有限元软件建立了切削模型,得到了不同切削速度和进给量下已加工工件的残余应力。结果表明,增大切削速度有利于增大深层压应力,同时也会增大表面拉应力;增大进给量有利于增大深层压应力,但对表面拉应力的影响无明显规律。     

MACHINING CHARACTERISTICS OF COMPLEX SURFACES USING FAST TOOL SERVO SYSTEM

Optical components with complex surfaces are more and more widely applied, but it is very difficult to manufacture these components by using traditional mechanical fabricating methods. Fast tool servo system can manufacture these complex surfaces or microstructures efficiently and accurately. The relative position between the tool and workpiece surface will vary continuously in the fast tool servo machining process, owing to the height change of workpiece profile in the same circle, and this will worsen the cutting conditions and debase the machining accuracy. In this paper, the cutting characteristics are studied in the fast tool servo machining process of complex workpiece, including the varying rule of cutting angle, and its influences on the rake angle and back angle, and the choice of machining parameters. Furthermore, the conditions for identifying tool interference are given. On the basis of the above work, two kinds of typical complex workpieces are manufactured by using fast tool servo system, including radial sinusoidal workpieces and lens array. The measuring results indicate that surface accuracy can reach 0.14 μm (peak-to-valley value) and the roughness is less than 10 nm (mean value).     

并联机床加工性能的实验研究

研究和验证了BJ-04-2(A)型并联机床的加工精度与加工表面粗糙度。研究手段是选择国家标准样件进行加工实验,样件加工采用一次装夹,运用端面铣削、侧刃铣削、钻削和镗削的方法加工而成。实验数据结果的分析表明,BJ-04-02(A)型并联机床加工精度中,直线度基本满足国家标准的要求,其它精度指标则未达到标准的要求,加工的表面粗糙度相当令人满意。     

薄壁零件加工变形分析及控制方案

介绍了有限元在分析薄壁件铣削加工变形中的应用，并提出一种数控补偿方法来减少让刀误差，从而控制薄壁件的加工精度。通过分析和实验建立切削力模型，运用ANSYS有限元分析软件对典型薄壁框体零件的加工变形进行了分析计算，结果与实际加工情况相符。根据有限元分析结果，提出在精加工时，在数控编程时让刀具在原有走刀轨迹中按变形程度附加一个偏摆，补偿因变形而产生的让刀量，可基本消除让刀误差。     

固定式三向铣削测力仪的研究

由于铣刀在铣削过程中切削位置不同,固定型铣削测力仪将产生输出误差。为降低铣削位置变化对传感器输出的影响,研制了一种四竖直敏感梁结构的应变型固定式三维铣削测力仪。研究表明,当铣削位置范围限定时,该测力仪可以将输出信号误差维持在可用范围,并分别进行了静态力测量和动态铣削实验。在静态力测量实验中,在70mm×70mm×15mm工件上,传感器解耦偏差不大于5.58%;在动态切削实验中,使用相同加工参数在不同位置处铣削,传感器测得的铣削力峰峰值最大相差3.73%。对该铣削测力仪的研究为解决竖直方向高刚度的应变型固定式铣削力传感器的解耦问题提供了新的思路和参考。     

超声电解复合微细加工装置与试验研究

分析微细电解复合超声频振动加工过程机理,提出一种微细加工新方法--超声电解复合微细加工;设计、构造并完善复合微细加工装置;研究微细阴极制作工艺,利用微细组合电加工技术制作各类截面形状的微细阴极;进行超声电解复合微细加工试验,验证微细电解复合超声频振动实现微细加工的可行性及其在加工速度、精度、表面质量等方面的技术优势,探讨超声电解复合微细加工制作微结构的工艺规律。     

An experimental investigation of tool wear in electric discharge machining

In this study, the variations of geometrical tool wear characteristics – namely, edge and front wear – and machining performance outputs – namely, workpiece removal rate, tool wear rate, relative wear and workpiece surface roughness – were investigated with varying machining parameters. Experiments were conducted using steel workpieces and round copper tools with a kerosene dielectric under different dielectric flushing conditions (injection, suction and static), discharge currents and pulse durations. The experiments have shown that machining parameters and dielectric flushing conditions had a large effect on geometric tool wear characteristics and machining performance outputs. Additionally, published research on tool wear is presented in detail in this study.     

基于气液两相流模型的电解加工多场耦合仿真

针对电解加工产生的气泡影响加工精度的问题,引入Euler Euler双流体模型对电解加工中气液两相流场进行描述,并耦合电场和温度场相关模型,分析了工具阴极、工件阳极表面气泡率、温度、电导率和电流密度的分布规律;通过调整加工电压、入口压力和出口压力,对工件阳极表面气泡率和电流密度分布进行仿真优化。仿真结果表明：在流速相同的条件下,减小加工电压、增加出口压力能够改善电导率分布,使阳极表面电流密度分布更加均匀。实验结果表明：仿真得到的阳极表面电流密度分布与工件轮廓高度误差分布吻合;采用优化后参数加工出的工件轮廓精度得到提高。     

面向加工特征的工件制造过程能耗预测方法

在工件的制造过程中,具有多个特征的工件在加工时,其加工特征的能耗属性不同,为了研究在工件不同的加工特征对能耗的影响,创建了面向加工特征的工件制造过程能耗预测模型。首先,将工件看成单个加工特征的集合体,其次对工件特征切削功率的分析,创建有关切削功率的能耗数学模型;然后采用GM(1,1)模型完成工件加工时其切削功率的灰色建模,实现整个工件能耗的预测过程,最后通过对冲床顶支座的加工过程为例,说明了该模型的准确性。     

Prioritization analysis and compensation of geometric errors for ultra-precision lathe based on the random forest methodology

Geometric errors remarkably affect the dimensional accuracy of parts manufactured by ultra-precision machining. It is vital to consider the workpiece shape for the identification of crucial error types. This research investigates the prioritization analysis of geometric errors for arbitrary curved surfaces by using random forest. By utilizing multi-body system (MBS) theory, a volumetric error model is initially established to calculate tool position errors. An error dataset, which contains information of 21 geometric errors, workpiece shape, and dimensional errors, is then constructed by discretizing the workpiece surface along the tool path. The problem of identifying crucial geometric errors is translated into another problem of feature selection by applying random forest on the error dataset. Moreover, the influence extent of each geometric error on the dimensional accuracy of four typical curved surfaces is analyzed through numerical simulation, and crucial geometric errors are identified based on the proposed method. Then, an iterative method of error compensation is proposed to verify the reasonability of the determined crucial geometric errors by specifically compensating them. Finally, under compensated and uncompensated conditions, two sinusoidal grid surfaces are machined on an ultra-precision lathe to validate the prioritization analysis method. Findings show that the machining accuracy of the sinusoidal grid surface with crucial geometric error compensation is better than that without compensation.