典型几何特征零件在线测量系统的研究与开发

基于华中8型数控系统,通过G代码宏程序及二次开发手段实现典型几何特征零件的在线测量。规划在线测量系统的架构,搭建数控机床在线测量系统的软件和硬件结构;实现测量系统与数控系统的连接;采用基于STM32的开关量高速数据采集I/O模块,得到精确的测头触发时刻坐标轴的位置;针对在线测量系统的误差,对重复精度进行实验分析,找出在x、y和z方向上进行测量时保证测量精度和效率的最优的测量速度;对测量路径进行规划并开发相关宏程序;实现基本的位置测量功能、刀具偏置的补偿和工件坐标系的自动修正。研究结论为复杂零件的测量以及在此基础上能够更高精度更高效率地在线测量奠定了基础。     

面向自由曲面零件的在线检测技术研究现状

数控机床在线检测系统是集数控机床、测头及计算机等为一体的高度集成化系统.高精度在线检测是实现柔性制造系统连续可靠工作的重要手段,是保证数控机床加工精度和效率的重要措施.在航空、汽车、模具等现代工业生产中出现了越来越多的自由曲面零件,这对测量系统提出了更高的要求,因而对具有自由曲面的零件进行高精度高效率的检测将是当前的一个重要研究方向.本文主要介绍自由曲面零件的在线检测技术在国内外的研究现状与进展,包括检测系统开发、自由曲面零件的接触式测量及路径规划和误差补偿等3部分,指出了目前在该领域存在的有待于进一步解决的关键问题.     

基于加工中心的在机测量与反求系统设计

利用加工中心、UG和自行开发的测量与反求软件构建了一套典型零件的快速测量与反求系统.在UG中建立待反求实体粗略模型,对构成零件的几何要素进行测点路径规划形成路径文件,通过测量与反求软件调用路径文件生成测量程序,传给加工中心进行要素的精确测量,测点数据经处理后重新在UG中生成精确零件模型替代粗略模型,从而实现了典型零件的快速测量与反求.     

基于复合测头的工件加工在机测量技术研究

研究一种用于数控加工机床的工件在机检测技术,用于对加工过程质量进行监测和控制,以缩短大型工件的加工制造周期,改变现有制造加工领域手工检测模式或离线抽检模式的现状。设计一种新的复合式在机测头并提出其测量系统实现方案。在机检测系统主要由数控机床、复合测头、无线信号收发器、控制计算机及其测量软件组成。数控机床作为测量运动驱动机构,其主轴带动复合测头对工件进行测量,并把测量结果通过无线信号收发器传输到控制计算机,通过模型反求和数据融合后处理,在机实时给出工件加工质量报告。通过在机修正工件加工路径,提高工件制造合格率和加工效率。     

基于机器视觉的轴类零件几何尺寸测量

基于轴类零件的几何特征与CCD获取的零件图像,利用数字图像处理技术对轴类零件进行边缘检测,提出了一种自适应开关中值滤波算法,该方法滤除噪声效果明显,开发了轴类零件尺寸测量系统,实现了轴的尺寸及其参数的测量.实验结果表明,改进的滤波器可以较好的保存图像的二维边缘信息,且在允许误差范围内采用机器视觉的非接触测量方法可以实现对轴的基本参数的快速准确测量.     

基于激光测头和数控机床集成的非接触测量系统开发

提出了一种在数控机床上集成激光测头以实现对自由曲面零件非接触式测量的方法。介绍了系统的测量原理，分析了系统的硬、软件组成并进行了系统实现。最后通过测量实例验证了该方法的有效性。     

套筒滚子链链板中心距的图像测量

介绍了一种基于CCD图像的套筒滚子链链板中心距测量系统,给出了利用数字图像处理技术进行几何尺寸非接触测量的方法.主要包括图像的采集、预处理、二值化、边缘检测及轮廓提取等,从而得到被测物体参数的精确结果,通过实例证明了该方法的可行性和正确性,该系统还可以推广到对其它微小零件进行非接触测量.     

CNC在线检测路径规划模型及应用研究

现有CNC在线检测路径规划模型以路径为基础,难以满足自动编程系统对于确定点位信息的要求。针对这一问题,在基于特征的传统路径规划的基础上,基于多体理论实现过渡路径自动规划,并建立以参数化的检测信息为输入,以测量节点的位置和遍历顺序为输出的规划模型,可以直接为检测程序自动编写系统所用。根据这一模型生成检测程序,经FANUC 0i系统CNC加工中心验证,这种模型能够用于具有典型特征的规则型面和组合型面工件的路径规划,符合点位控制机床的运动特点,为自动编程的实现奠定了基础。且相对于人工路径规划,应用路径规划模型可以提高规划效率和准确性。     

结合路径规划和光学扫描的自动测量方法研究

传统的复杂零件形貌测量中,为解决人工测量造成的测量效率偏低,误差较大和易出错等问题,文章结合工业机器人和光学扫描仪,提出复杂零件的自动测量方法。通过Motosim软件对机器人进行离线编程,生成用于扫描复杂零件的自动测量程序;基于规划的路径和机器人移动时间,编写驱动程序控制机器人和光学扫描仪,完成复杂零件的自动测量工作。结果表明:通过驱动程序控制机器人和光学扫描仪实现复杂零件的自动测量,能够有效提高测量效率,且测量精度达到20μm。     

高速高精密数控机床多路恒温控制系统的研究

在分析温度控制对实现精密和超精密加工技术的重要性基础上,提出了一种恒温油液喷淋机床运动部件方法来减少机床热变形和保障零件加工精度的多路恒温控制方法。构建了由PC机、PLC控制器、压缩机、旁通阀、冷凝器、电磁阀、蒸发器、热力膨胀阀、泵和油槽等组成的高速、高精密数控机床多路恒温控制系统,应用PLC的模拟量检测方法实现对油槽温度、压力(液位)进行实时测量,从而实现对数控机床的恒温控制,以保障高速、高精密数控机床系统的工作稳定性。     

Development of a multi-step measuring method for motion accuracy of NC machine tools based on cross grid encoder

Machining accuracy is directly influenced by the quasi-static errors of a machine tool. Since machine errors have a direct effect on both the surface finish and geometric shape of the finished work piece, it is imperative to measure the machine errors and to compensate for them. A revised geometric synthetic error modeling, measurement and identification method of 3-axis machine tool by using a cross grid encoder is proposed in this paper. Firstly a revised synthetic error model of 21 geometric error components of the 3-axis NC machine tools is developed. Also the mapping relationship between the error component and radial motion error of round work piece manufactured on the NC machine tools are deduced. Aiming to overcome the solution singularity shortcoming of traditional error component identification method, a new multi-step identification method of error component by using the cross grid encoder measurement technology is proposed based on the kinematic error model of NC machine tool. Finally the experimental validation of the above modeling and identification method is carried out in the 3-axis CNC vertical machining center Cincinnati 750 Arrow. The entire 21 error components have been successfully measured by the above method. The whole measuring time of 21 error components is cut down to 1–2 h because of easy installation, adjustment, operation and the characteristics of non-contact measurement. It usually takes days of machine down time and needs an experienced operator when using other measuring methods. Result shows that the modeling and the multi-step identification methods are very suitable for ‘on machine’ measurement.     

基于岭回归的数控机床温度布点优化及其热误差建模

提出一种基于岭回归分析的数控机床温度布点优化方法.数控机床热误差建模一般采用多元线性回归方法,在多元线性回归模型中,隐含着要求解释变量之间无强相关性的假定.然而在实际的建模中,各自变量与因变量之间的相互关系并不与简单相关系数所反映的情况完全吻合.通过岭迹对温度变量进行优化选择,实现了温度测点优化布置,并选用适当的岭参数k建立了数控机床热误差的多元线性回归优化模型,提高了热误差模型的精确性和鲁棒性.     

基于内置传感器的数控机床动态加工误差测量方法

以HJ044双转台型五轴联动数控机床为例,以机床内置传感器信息和多体系统理论为基础,建立了刀具相对工件的运动学模型,提出了一种基于内置传感器信息的动态加工误差测量方法。该方法利用机床编码器或光栅尺等机床内置传感器信息获取机床各轴运动位移,并结合机床运动学模型,测量由机床的动态特性引起的加工误差。并通过实验表明该方法是一种简单有效的数控机床动态加工误差测量方法。     

Modeling and measurement of active parameters and workpiece home position of a multi-axis machine tool

The complex structures of a multi-axis machine tool may produce inaccuracies at the tool tip caused by dimensional errors in the machine's link parameters. This paper addresses two important issues for precision machining: (1) which link parameters (denoted as active parameters) of a machine tool can affect the machining accuracy of a workpiece and (2) how to measure the active parameters by using a grinding wheel as a measuring probe. To achieve this, a modified Denavit–Hartenberg (D–H) notation is introduced to model a multi-axis machine tool. The NC data equations are then derived in terms of the machine's link parameters. It is found that the link parameters of a machine tool can be divided into two types: active and nonactive parameters. The prerequisite for obtaining an accurately machined workpiece is to have correct values of the active parameters and the workpiece home position. Based on the developed NC data equations of a multi-axis machine tool, this paper also addresses the technique of using a grinding wheel as a measuring probe to determine the active parameters and the workpiece home position. Experimental results are also given with illustrative examples.     

基于SINUMERIK 828D数控系统的数控机床螺距误差与反向间隙的测量与补偿

探讨了数控机床螺距误差和反向间隙的形成原理。针对采用西门子SINUMERIK 828D数控系统的数控机床,给出了测量数控机床位置偏差的运动程序,介绍了螺距误差和反向间隙测量和补偿的方法和步骤。     

Application of homogenous transformation matrix to measurement of cam profiles on coordinate measuring machines

A kinematic model is presented to aid the cam profile design task and to determine the NC data required to move an inspection probe to the necessary locations to inspect the surface profile of a spatial cam on a coordinate measuring machine (CMM). The cam profile is designed in accordance with the principles of conjugate surface theory. Homogenous transformation matrices are then employed to derive the CMM ability function matrix and the measuring probe location matrix. The required NC data are obtained by equating the elements in the ability function matrix with the corresponding elements in the probe location matrix in order to solve the CMM link variables. The validity of the proposed approach is verified by carrying out the automatic inspection of a machined cam on a CMM using the NC data computed by the developed algorithm. The methodology presented in this study combines the cam design, machining and inspection activities, and makes possible a flexible and automatic spatial cam design and manufacturing process.     

CNC中基于Bezier拟合的Look-Ahead轨迹规划的研究

轨迹规划是CNC系统的重要功能之一。传统CNC在处理连续微小NC程序时,存在诸如机床震颤、工件毛刺、加工效率低等问题。作者提出的Look-Ahead轨迹规划算法能解决上述问题,此算法将NC程序分成3种大路径段,将连续微小路径(CSBs)拟合成Bezier曲线,再进行速度规划和轨迹插补,在此基础上提出Look-Ahead离线插补器的结构。仿真结果表明,该算法能够实现大量微小路径的连续加工。     

A new method and instrument for measuring circular motion error of NC machine tools

A new method and instrument for measuring circular motion error of numerical control (NC) machine tools are described in this paper. The instrument consists of a linear displacement transducer bar with two balls at each end and a high accuracy rotary encoder. The radius variations are detected by the transducer and the rotation angle of the bar is measured by the rotary encoder while the machine is moving in a circular path. The measuring area is circular except for a small area around the center of the disc. The bar can be expanded and contracted along its axis for different application. The instrument has a compact structure and can be installed on a machine tool simply and quickly. It is shown by the experimental results that the instrument has good repeatability and high precision of measuring circular motion trajectories. The instrument can be widely used especially in the error-compensation and error-source project in the industrial application.