Effect of different machining processes on the tool surface integrity and fatigue life

Ultra-precision grinding, wire-cut electro discharge machining and lapping are often used to machine the tools in fine blanking industry. And the surface integrity from these machining processes causes great concerns in the research field. To study the effect of processing surface integrity on the fine blanking tool life, the surface integrity of different tool materials under different processing conditions and its influence on fatigue life were thoroughly analyzed in the present study. The result shows that the surface integrity of different materials was quite different on the same processing condition. For the same tool material, the surface integrity on varying processing conditions was quite different too and deeply influenced the fatigue life.

     

光纤连接器端面研磨装置运动分析

分析了一种具有两个自由度的双驱动行星式光纤连接器端面研磨装置的运动原理,并求解出光纤连接器在研磨时相对于研磨盘(研磨砂纸)的运动轨迹。通过引入定义"速比",建立了研磨装置两个独立主动件之间的转速关系。针对光纤连接器研磨中存在的问题,从速比入手,以运动轨迹曲线、研磨运动路程偏差、切削速度、速度周期变换系数为纽带,将研磨运动、研磨工艺以及研磨质量联系起来,得出了一组优化的光纤连接器研磨装置的运动参数。当系杆的转速设定为132 r/min时,根据粗、精研磨不同的工艺要求,其内齿轮的转速应在31~54 r/min调整。此时,速度周期变换系数小于2.2;运动路程偏差小于0.5%;研磨运动轨迹密集而不重复。实验证明了分析结果的正确。     

机械制造业数控机床几何误差自动控制

为了降低数控机床几何误差,提升加工精度,提出机械制造业数控机床几何误差自动控制方法。通过激光跟踪仪辨识机械制造业数控机床的几何误差,采用快速定位补偿算法与圆弧插补补偿算法相结合的方法补偿数控机床几何误差。利用计算机辅助制造软件生成刀位文件,依据刀位文件生成数控机床加工程序,通过补偿控制器生成数控机床各轴运动的控制指令,数控机床伺服系统接收控制指令后,自动控制数控机床各轴运动,以达到数控机床几何误差自动控制的目的。实验结果表明,采用该方法自动控制数控机床几何误差后,方向与角度的几何误差分别低于0.03 mm与0.1°,实际应用效果较好。     

Lapping machine with a cycloid tool trajectory

A lapping machine with a cycloid tool trajectory is proposed for precision plane finishing. The configuration of the machine is described, as well as the kinematics of the primary motion and the forces pressing the parts against the tool. Methods of controlling the density of the network of tool tracks are presented. To boost the productivity and final surface quality, a trajectory with high cutting speed—for example, a cycloid tool trajectory with a low density of tool tracks—is specified at the beginning of machining parts and then, as the margin is removed and the flatness of the machined surface is improved, the density of the network of machining tracks is increased to form the required microrelief.     

A manufacturing model of helical groove on rotary burr and a universal post processing method

A systematic machining theory and precision method to determine cutter location in a grinding system is presented for rotary burr. First, the helical cutting edge on various kinds of revolving surfaces is built. Then, based on the geometry model of the helical cutting edge, the smooth spiral rake surface with constant normal rake angle and flank surface can been formed during the one-pass grinding process by this method. No interference between the grinding wheel and workpiece happens by the wheel special rotation. The method has the characteristic of detaching the grinding wheel path solution from specified machining conditions. The grinding wheel path is suitable for different NC machine tools through post processing. Meanwhile, a mechanism kinematic model of the NC machine tool is built, and a generalized algorithm for post-processing of multi-axis NC machine tools is presented. This model is applied to arbitrary configuration of NC machine tool, and the motion value for each axis will be generated by the inputting structure and motion parameters of the machine tool. The model, together with the machining method mentioned in this paper, make the calculation and generation of the grinding wheel path simpler and universal. At last, the validity of the method given in the paper is identified by an example of grinding.     

数控机床运动误差检测与仿真

本文介绍了一种测量数控机床和加工中心运动误差的新装置－双球规的结构特点，测试原理及测试方法，给出数控机床常见的各种运动误差矢量表达式特征模型，并进行了计算机仿真研究。     

端面正弦直纹曲面零件的线切割加工技术

为解决端面正弦直纹曲面的加工难题,提出了利用国产高速走丝电火花线切割机床进行加工的一种方法。依据正弦直纹曲面的形成原理,分析线切割加工的运动方式。通过数控回转台与线切割机床相结合,形成实现加工所需的运动,进行了样件的实验加工,实验结果表明,设计的加工方法合理有效。     

盘刀加工等基圆锥齿轮的刀具位姿及运动轨迹计算

为了实现使用盘形铣刀数控加工等基圆曲线齿锥齿轮,基于等基圆曲线齿锥齿轮理论,通过建立盘形铣刀加工数学模型,求解了决定刀具空间姿态的主要参数。通过盘形铣刀刀轴矢量、刀心坐标的求解,得到了轮坯坐标系下的刀位。结合通用五坐标数控机床,求得了五坐标数控加工等基圆锥齿轮运动轨迹的表达式。通过三维造型,对刀位求解进行了分析验证;通过仿真切削加工,验证了运动轨迹的正确性。结果表明,利用盘形铣刀数控加工等基圆锥齿轮的刀具位姿、运动轨迹的求解正确,在通用数控机床上利用盘形铣刀能够加工等基圆曲线齿锥齿轮。     

并联机床数控加工过程仿真方法的开发

针对六自由度数控铣床－并联机床的数控加工,本文提出一种新的加工过程仿真算法。该算法基于观察坐标系,利用扫描线算法在精度范围内表示工件和刀具,从而将复杂的三维布尔运算简化的一维布尔运算。笔者在微机上利用ＶＣ＋＋,根据这种新算法,开发出并联机床数控加工过程仿真系统,实现了并联机床数控加工过程仿真。     

基于杠杆模式施载的圆弧刃光栅刻画刀具刃磨机床研制

采用圆弧刃光栅刻画刀具,实现在线换刃技术是解决光栅刻画刀具使用寿命问题的一种有效的途径。在线换刃圆弧光栅刻画刀具对刃口质量及精度要求高,刃磨制作工艺难度大,且国内外市场几无此类刃磨设备,需要自行设计制作圆弧刃光栅刻画刀具刃磨机床。在圆弧刃光栅刻画刀具刃磨试验设备设计制作及圆弧刃光栅刻画刀具刃磨制作工艺研究基础上,针对圆弧刃光栅刻画刀具的刃磨特点,设计新型的基于杠杆模式施载的圆弧刃光栅刻画刀具刃磨机床;根据传统机床的设计程序,对刃磨机床的功能、总体设计及详细结构设计展开研究,并对施载与微进给机构进行了振动分析,排除了出现共振的可能性。最后完成了该机床的机械装调,并刃磨制作一把圆弧刃光栅刻画刀具,其定向角∠D=63°,刀尖角∠J=90°,刃圆半径R=8.56mm,在460倍体视显微镜下观察无崩口等缺陷,刃口弧线清晰可见。刀具检测及观测结果表明,所设计的圆弧刃刀具刃磨机床适用于圆弧刃光栅刻画刀具的刃磨制作,所采用的分析及设计方法对圆弧刃刀具刃磨机床及其他机床的设计和研制具有实际指导意义。     

Influence of position-dependent geometric errors of rotary axes on a machining test of cone frustum by five-axis machine tools

A machining test of cone frustum, described in NAS (National Aerospace Standard) 979, is widely accepted by machine tool builders to evaluate the machining performance of five-axis machine tools. This paper discusses the influence of various error motions of rotary axes on a five-axis machine tool on the machining geometric accuracy of cone frustum machined by this test. Position-independent geometric errors, or location errors, associated with rotary axes, such as the squareness error of a rotary axis and a linear axis, can be seen as the most fundamental errors in five-axis kinematics. More complex errors, such as the deformation caused by the gravity, the pure radial error motion of a rotary axis, the angular positioning error of a rotary axis, can be modeled as position-dependent geometric errors of a rotary axis. This paper first describes a kinematic model of a five-axis machine tool under position-independent and position-dependent geometric errors associated with rotary axes. The influence of each error on machining geometric accuracy of a cone frustum is simulated by using this model. From these simulations, we show that some critical errors associated with a rotary axis impose no or negligibly small effect on the machining error. An experimental case study is presented to demonstrate the application of R-test to measure the enlargement of a periodic radial error motion of C-axis with B-axis rotation, which is shown by present numerical simulations to be among potentially critical error factors for cone frustum machining test.     

基于刀轨广义偏置的电火花摇动加工补偿方法

针对电火花加工中电极摇动产生加工误差的问题,结合电极自由曲面数控加工的基本原理,提出基于数控刀轨广义偏置的补偿方法。通过对电极自由曲面原始加工刀轨的广义偏置计算,可有效、统一地解决自由曲面电极典型摇动方式所引起的加工误差问题,同时对偏置计算后产生的刀轨自交问题进行讨论。针对实际生产加工对象和不同的电极摇动方式,进行补偿计算和生产加工验证。检测结果表明,该方法能够较大地提高加工精度,缩短生产周期。     

基于UG的虚拟机床运动学建模与仿真

数控机床的运动学建模是实现数控机床虚拟加工的一个底层关键技术.基于UG强大功能模块,通过对数控机床及系统的运动学建模从而实现数控加工过程的虚拟仿真,为检验数控加工程序的正确性提供了新的方法.     

混联数控机床虚拟加工系统的研究与开发

针对混联机床加工过程中干涉检查、空间刀具半径补偿及编程难等问题,分析了混联机床运动学逆解,提出了一种空间任意面内的刀具半径补偿方法,给出了干涉检查的判断条件。以V is-ual C++为开发环境,应用AutoCAD二次开发工具ObjectARX,建立了由NC代码驱动的混联数控机床加工仿真系统,实现了以真实加工条件为依据的加工过程实时动态模拟,预估加工的过程和结果,为检查NC代码的正确性提供了可靠的依据。     

机器人复合加工模具曲面的干涉回避与质量控制

提出一种由机器人和超声电火花复合研磨机等组成的自动研磨加工系统，对在模具曲面加工过程中出现的工具与工件之间可能产生的局部干涉现象进行了研究，通过干涉回避技术建立复合精加工表面质量的控制模型，并在试验中证实了理论的正确性。     

基于机床运动模型的走刀步长计算方法

为提高五坐标数控加工刀具轨迹生成的精度和切削效率,通过特定机床结构运动建模,对自由曲面刀具轨迹规划中的走刀步长计算方法进行研究。针对刀具摆动与工作台转动类型的非正交结构五坐标机床,在建立机床运动传递关系的基础上,实现任意刀轴方位的机床各轴运动坐标分解,构建机床运动模型。基于此,分析切削误差产生机理,推导出非正交结构的机床实际运动误差估计公式。利用切削误差对比关系,迭代计算满足精度要求的最大走刀步长。算例表明,在相同的允许误差条件下,本文算法较之传统变步长方法,最大误差降低了37.01%,而平均步长相对于等步长方法,增加了8.91%,说明基于机床运动模型的走刀步长计算方法能够有效控制切削误差,并提高自由曲面五坐标加工的刀具轨迹质量。     

大型工件球面的加工方法

大型工件因质量重、体积大,进行球面加工时费时、费力。如果在普通机床上进行数控改造,则投入较大。笔者介绍了对普通机床进行小的改造,便可实现大型工件球面加工的改造方法,改造后安装方便,使用简单,操作容易,费用低。在没有数控设备的情况下,是加工大型工件球面的一种好方法。     

Algorithm for detecting volumetric geometric accuracy of NC machine tool by laser tracker

Quick and accurate detecting the error of NC machine tool and performing the error compensation are important to improve the machining accuracy of NC machine tool.Currently,there are many methods for detecting the geometric accuracy of NC machine tool.However,these methods have deficiencies in detection efficiency and accuracy as well as in versatility.In the paper,a method with laser tracker based on the multi-station and time-sharing measurement principle is proposed,and this method can rapidly and accurately detect the geometric accuracy of NC machine tool.The machine tool is controlled to move in the preset path in a 3D space or 2D plane,and a laser tracker is used to measure the same motion trajectory of the machine tool successively at different base stations.The original algorithm for multi-station and time-sharing measurement is improved.The space coordinates of the measuring point obtained by the laser tracker are taken as parameter values,and the initial position of each base point can be determined.The redundant equation concerning the base point calibration can be established by the distance information of the laser tracker,and the position of each base point is further determined by solving the equation with least squares method,then the space coordinates of each measuring point can be calibrated.The singular matrix does not occur in calculation with the improved algorithm,which overcomes the limitations of the original algorithm,that the motion trajectory of machine tool is in a 3D space and there exits height difference between the base stations.Adopting the improved algorithm can expand the application of multi-station and time-sharing measurement,and can meet the quick and accurate detecting requirements for different types of NC machine tool.     

数控机床教学培训平台构建

为了提高数控机床操作人员的培训质量、降低培训成本,以数控加工仿真技术和数控机床联网技术为基础,构建了一个集课堂讲授、仿真实验、操作实验一体化的数控机床教学培训平台,并研究了数控加工仿真和数控机床联网的关键技术和实施方案。