加工轨迹对薄壁件微结构电解铣削的影响北大核心

为改善难加工材料弹性合金3J21薄壁件微结构的成形加工质量和效率,进行了加工轨迹对薄壁件微结构的电解铣削加工的影响研究。首先利用拷贝式电解加工方法在线制备了阶梯轴式微细工具阴极,然后利用5种不同加工轨迹进行了150μm"150μm微型方孔的微细电解铣削加工对比实验,并优选出了最佳的加工轨迹。研究结果表明,利用"行铣+环铣"的加工轨迹进行微细电解铣削加工时微型方孔的加工质量更好,加工效率较高。     

金属微结构的电解铣削加工技术研究

随着微机电系统的发展,微细加工技术成为了当今世界的研究热点。对微细电解铣削加工技术进行了深入研究,在难加工材料镍基高温合金上进行了一系列微细电解铣削加工工艺试验。首先,基于微细电解铣削加工原理,自行研制了一套高精度微细电解铣削加工系统。其次,分组试验并分析了各主要参数,如铣削层厚度、加工电压、脉冲宽度、电极直径,以及电解液浓度等对形状精度和加工精度的影响规律。最后,通过优化加工参数,成功加工出了数个典型三维平面及曲面微结构,形状精度高,加工稳定性好,充分展现了微细电解铣削工艺在加工复杂金属微结构方面的巨大潜力。     

加工轨迹对薄壁件微结构电解铣削的影响

为改善难加工材料弹性合金3J21薄壁件微结构的成形加工质量和效率,进行了加工轨迹对薄壁件微结构的电解铣削加工的影响研究。首先利用拷贝式电解加工方法在线制备了阶梯轴式微细工具阴极,然后利用5种不同加工轨迹进行了150μm"150μm微型方孔的微细电解铣削加工对比实验,并优选出了最佳的加工轨迹。研究结果表明,利用"行铣+环铣"的加工轨迹进行微细电解铣削加工时微型方孔的加工质量更好,加工效率较高。     

小型数控微细铣床的研制及铣削试验研究

总结了现有微小零件加工技术的局限性,阐述了微细铣削加工的优势,并自主构建了一台适于微小零件制造的小型三轴数控微细铣床,铣床本体尺寸为400mm×400mm×260mm,工作空间为50mm×50mm×50mm。介绍了组成微细铣床的六大子系统的性能,对微细铣床系统进行精度测试,该铣床的定位精度达到1μm,满足微细铣削加工的精度要求。使用硬铝LY12进行微直槽及薄壁、微同心圆槽的铣削加工试验。加工试验结果显示:该微细铣床已经具备加工介观尺度的高深宽比微小零件的能力。     

基于MATLAB的微细铣削加工测试系统开发

由于微细铣削加工技术可以弥补微机电系统在微小零件加工中的不足,微细铣削加工机床的研制日益被重视.以正在研制的微细铣削机床为实验环境,开发了基于MATLAB软件平台的微细铣削加工测试系统(异于传统的测试系统),可以监测铣削加工中的切削力、切削温度和切削颤振等.介绍了美国仪器(National Instrument,NI)公司的数据采集设备(N19233)在MATLAB中的使用,以及应用MATLAB进行数据的分析和处理,最后通过监测机床振动的实验分析了微细铣削机床x轴的性能,为深入研究微细铣削加工机理奠定了基础.     

304不锈钢微型环槽的微细电解铣削加工技术研究

针对304不锈钢薄壁件微小结构采用传统加工方法会产生变形的加工难题,基于分层铣削思想利用微细电解铣削加工技术对304不锈钢材料进行了微型环槽的加工实验,加工出了297×105×30μm的微型环槽结构,为金属材料薄壁件微小结构的加工制造提供了一种思路。     

微细电火花铣削CAD/CAM方法研究

利用简单电极的微细电火花铣削加工具有适应性强、可操作性好等特点,在微三维结构的制作方面显示出了良好的应用前景。但是在电火花分层铣削加工中,加工表面始终存在着台阶问题,并且对方程难以给定的复杂曲面而言尤为如此。系统研究了微细电火花铣削的分层策略、电极轨迹生成方法、插补算法以及加工轨迹的平滑算法,结合等参数插补方法对分层加工后的型腔表面进行修正,较好地解决了加工台阶问题。利用所研究的CAD/CAM技术进行了加工试验,给出了亚毫米级复杂三维曲面的加工实例,验证了方法的正确性。     

激光诱导氧化辅助微细铣削TiB_2基陶瓷复合材料试验研究

陶瓷复合材料具有高硬度、高弹性模量、耐磨、抗化学腐蚀等诸多优异性能,在航空航天、微电子、汽车、切削刀具和生物医学等领域具有广泛应用前景,但其微细铣削加工中存在铣削力高、刀具磨损严重等问题。本文提出了一种激光诱导氧化辅助微细铣削的复合加工方法,并用该方法制备了TiB_2基陶瓷复合材料微结构。在激光辐照下,TiB_2基陶瓷复合材料氧化生成具有一定厚度的、疏松易去除的氧化层;在此基础上,利用微细铣削工艺依次去除氧化层、热影响层和少量基体材料,以获得高加工效率和加工质量。主要研究了铣削深度和每齿进给量对铣削力和表面粗糙度的影响规律,结果表明,随着铣削深度和每齿进给量的增大,铣削力逐渐增大;在铣削深度为2μm、每齿进给量为0.3μm/z时,已加工表面粗糙度最小,S_a为0.06μm;随着铣削深度和每齿进给量的增大,材料去除方式先后经历弹性滑动摩擦、延性模式和脆性模式三个阶段。     

TC4钛合金微细铣削仿真与试验研究

钛合金由于其高的强度和耐热性、低的导热系数,在微细加工时若切削参数选择不合理容易导致切削力大、加工质量不稳定。在微细铣削加工中,由于刃口半径和尺寸效应的存在,选择合适的切削参数对于切削状态的改善有重要意义。通过仿真和试验对比分析,研究TC4钛合金在微细铣削过程中每齿进给量对切屑变形、铣削力和加工表面粗糙度的影响,以期为改善微细切削状态、提高加工表面质量提供合适的切削参数选择指导。结果表明,在使用刃口半径为2.05μm、刀具直径为1 mm的硬质合金铣刀对TC4钛合金进行微细铣削加工时,微细铣削TC4钛合金切削状态发生转变时所对应的临界每齿进给量为0.8μm/z;微细铣削时每齿进给量应大于此临界值。     

电泳辅助微细超声加工机床设计与实验

微细超声加工时,加工区域内的磨粒会被高频振动的工具或工件振出加工区,使加工区域出现无磨粒,导致工具与工件直接作用,影响加工质量与加工效率。为解决上述问题,提出了一种电泳辅助微细超声加工新技术。利用超微磨粒的电泳特性,通过在工具电极与辅助电极之间施加电场,溶液中的超微磨粒泳动到加工区域,甚至是附着或半附着在微细工具上,保证了加工区域磨粒的存在,从而提高微细超声加工质量、加工效率。针对新技术,设计了电泳辅助微细超声加工机床并进行了实验,机床硬件部分包括主轴设计、运动系统硬件设计、电泳辅助微细超声加工工作液槽设计及数据采集系统硬件设计;基于LabVIEW软件开发恒力控制加工控制系统,包括初始化模块、运动控制选择模块、粗对刀模块、恒力对刀模块、恒力控制加工模块以及实时显示模块。开展了微细超声加工与电泳辅助微细超声加工对比实验研究,实验结果表明,在保持其他加工参数相同的条件下,电泳辅助微细超声加工的孔边缘质量更好,微细超声加工后的孔底表面粗糙度Sa=3.008μm,而电泳辅助微细超声加工后的孔底表面粗糙度Sa=1.494μm。     

Error prediction and compensation based on interference-free tool paths in blade milling

We propose a method which uses interference-free tool paths to predict and compensate for deformation error during the spiral milling of blades. Firstly, a finite element simulation of the blisk blade milling process was conducted using an interference-free spiral milling NC machining tool path based on the curvature attribute of the blade twisted surface, observing the variation in blade milling error under different processing parameters and yielding a surface quality variation law. Next, the model was corrected by combining this error prediction data with precision design requirements, and a blade deformation error compensation scheme was suggested. Finally, an interference-free processing program containing the error compensation information was applied to carry out another blade milling simulation and a blisk milling experiment. The results showed that both the blade deformation error and the surface quality satisfied design requirements, while the accuracy of the simulation was verified.     

用于异形孔精密加工的超磁致伸缩构件的线性化迟滞建模

根据超磁致伸缩构件精密加工异形孔刀具轨迹的特点,采用纯延时环节串联线性化模型,建立其在高频驱动下驱动电流与输出微位移的迟滞非线性动态模型.通过一定频率下驱动电流与输出位移的相关辨识,获得系统纯延时环节的补偿参数,并建立了驱动电流与无相位差输出位移的线性化模型.当实时控制时,通过迟滞非线性模型的直接逆模型补偿,使位移输出与异形孔的理想刀具轨迹一致.实验验证表明,直接逆模型的最大开环控制误差为2.7 μm,最大相对误差为10％.进一步对构件进行微位移反馈闭环控制,实验误差最大值为1.2 μm,最大相对误差为7％,提高了系统的控制精度.     

基于数控系统底层通信的实时误差补偿及应用

为提高数控机床加工精度,设计开发基于CNC底层通信的实时误差补偿功能模块,该模块通过GSK-Link网络通信协议与CNC底层进行数据交互。实时补偿过程为：通过温度采集模块和数据通信模块实时采集机床温度及各坐标轴坐标,误差补偿器计算误差补偿值并将计算结果直接送往CNC实时误差补偿功能模块,以实现机床误差实时补偿。该补偿过程的最大优点是实时补偿器与CNC底层直接通信,而不是目前国际上惯用的先通过PLC再与CNC底层通信的方式,因此实时补偿的速度和效率更高,补偿效果更好。GSK 25i数控系统的实时补偿结果表明,实时误差补偿可有效提高机床精度,最大可提高91.7%。     

虚拟制造中基于刀具磨损的复杂曲面加工误差补偿

基于数控铣削加工仿真系统,研究了在虚拟制造环境下对球头铣刀磨损引起的曲面加工误差的预测与补偿。建立了与加工参数相关的球头铣刀磨损模型,用于预测球头铣刀切削刃的磨损量,提出了球头铣刀铣削加工误差的补偿方法,并通过实验验证了该方法的有效性。     

Micro electrochemical milling of complex structures by using in situ fabricated cylindrical electrode

A micro electrochemical milling by layer process is presented in this paper. Because of no tool wear in electrochemical micromachining, a very thin tungsten electrode is used as the tool cathode. By applying ultrashort pulses, dissolution of a workpiece can be restricted to the region very close to the electrode. First, the mathematical model of micro electrochemical milling by layer is established to ensure a good shape precision. Second, the micrometer scale cylindrical electrode is fabricated in situ by electrochemical etching for the production of micro structures. And then, effects of machining parameters on the side gap variation in electrochemical milling process have been studied experimentally. Finally, some 2D micro shapes and 3D complex micro structures with physical dimension of several 10?μm have been obtained.     

Geometric error compensation software system for CNC machine tools based on NC program reconstructing

It has been proved that error compensation is an effective approach to improve machining accuracy of a machine tool cost efficiently. In this paper, the framework of an error compensation software system, which can realize software error compensation via numerical control (NC) programs reconstructing, is investigated. And the algorithms relating to error prediction are discussed in detail, such as positioning movement error compensation, linear interpolation movement, and circular interpolation movement error compensation. To realize the error compensation, NC program is reconstructed according to the predicted errors during virtual machining before it is fed to the actual machining. Two controlled machining experiments were carried out. The results show that error compensation methods via reconstructing NC programs can improve the movement accuracy of a computer numerical control CNC machine tool obviously.     

In-situ process monitoring and adaptive control for precision micro-EDM cavity milling

The linear tool wear compensation method (LCM) is commonly applied in micro-EDM 3-D milling to compensate the tool length wear in order to achieve high machining accuracy. Traditional LCMs mainly rely on empirical models and off-line wear measurements, whereas the process dynamics are not taken into account. When machining complex 3D cavities, an increasing number of tool wear compensation cycles have usually to be performed in order to maintain the targeted machining accuracy. This negatively affects the duration of the overall machining cycle. To realize efficient precision micro-EDM cavity milling, without the necessity to predefine Z-axis tool feed in the NC trajectory before machining, an in-situ process control system is developed to adaptively control the tool wear compensation factor based on the discharge pulse behavior. Experiments have shown that the change of the compensation factor can be detected and also a continuous increase of the factor (over compensation) leads to the saturation of the mean effective pulse frequency. Pulse monitoring therefore provides valuable information for understanding the process dynamics and for selecting the machining parameters towards better machining efficiency. Furthermore, the information gathered in-situ can be utilized to predict the tool wear and perform in-situ tool wear prediction. To implement this on machine-level, a combined off-line and in-line adaptive control of the tool wear compensation factor is proposed and experimentally validated by milling different 3D cavities. The off-line adaptive control is only necessary when the predicted machining depth error exceeds a certain limit. In this way, more than 80% of the off-line adaptive control cycles can be eliminated, whereby a total save of cycle time up to 18% has been reached, while still maintaining the desired dimensional and form accuracy.     

球头铣刀刀具磨损建模与误差补偿

针对刀具磨损度量方式和模型建立的问题,以球头刀具为研究对象,提出球头铣刀刀具磨损的度量方式,建立球头刀具磨损模型.以复映磨损在硬度较软加工材料上的方式测量球头刀具磨损,确定刀具磨损模型系数,给出刀具磨损模型系数确定的具体实现方法.加工试验验证球头刀具磨损度量方式的合理性和所建立刀具磨损模型的正确性,同时针对数控铣削加工中球头铣刀刀具磨损引起的误差提出离线仿真误差补偿算法,给出离线仿真误差补偿算法的具体实现步骤,通过建立的刀具磨损引起的加工误差模型仿真获得加工走刀步的误差.对于误差超差的走刀步,预先修改数控加工(Numerical control,NC)程序,保证实际加工零件满足精度要求.误差补偿验证试验表明所提出的离线仿真误差补偿算法的正确性和有效性.     

龙门式多轴联动机床的几何误差建模

设计一台集加工、检测于一体的小型龙门式多轴联动加工系统,以实现小型或微小型零件的铣、钻、磨削加工。机床除了从结构上提高精度外,也采取了误差补偿的措施,通过对机床进行几何误差建模,得到几何误差模型,以便进行补偿,提高精度。