自由曲面数控加工智能选刀方法的研究与开发

由于自由曲面的几何复杂性,其数控加工的刀具干涉判别和刀具选取往往依靠数控机床编程工程师的经脸,致使加工的安全性、精度、效率及可靠性得不到有效保证.采用改进的遗传算法获取自由曲面的点云数据,在自主开发的系统中重构自由曲面.研究自由曲面加工刀位面生成的几何机理,根据刀具类型和几何尺寸,自动生成自由曲面数控加工的刀位面,可视化判别是否发生刀具干涉.将改进的快速排序算法应用到智能选刀模块,通过对常用类型和尺寸的刀具进行干涉排查,在避免干涉的前提下,智能选取最优化的加工刀具.对三种加工方案进行了测试,验证了智能选刀方法的正确性.     

曲面数控加工刀位点计算的新方法

提出了一个新的面向数控加工的曲面离散模型。讨论了该模型的定义、精度控制准则以及它在数控编程刀位点计算中的应用。与现有的两种刀位点计算方法相比，利用该模型生成刀位点具有快速、灵活、方便、可靠的优点。     

基于CATIA平底铣刀五轴数控编程技术研究

在五轴联动数控加工中,通常采用球头铣刀进行曲面的加工,但是对于双曲面加工,球头铣刀的加工效果较平底铣刀有所不足,因此需要采用平底铣刀来替代球头刀具进行双曲面的加工。但是采用平底铣刀加工双曲面时,由于曲面各处曲率的变化导致刀路轨迹的规划复杂而且困难,而大大影响其在加工曲面中的应用。对此,研究利用平底铣刀的五轴数控联动机床加工双曲面时的刀路轨迹,通过计算得到刀路轨迹的刀位点,设计出利用平底铣刀的五轴数控联动机床加工曲面的刀位轨迹规划方法。结果表明:该方法改善了五轴数控加工中球头铣刀的不足之处,提高了曲面加工的加工质量、加工精度和加工效率。     

船用螺旋桨数控加工干涉仿真及刀轴方向控制技术研究

干涉检测是螺旋桨数控加工中的关键问题,如果在加工过程中发生干涉,会破坏机床甚至造成重大损失。基于UG软件,构建了螺旋桨加工仿真平台,利用该平台进行螺旋桨加工过程仿真和干涉分析;在虚拟环境中,检验数控程序是否干涉;针对虚拟仿真过程中发现的发生干涉的刀位点,反复自动调整刀轴矢量,计算出无干涉刀轴矢量数据,优化数控程序,以避免干涉碰撞,提高了数控程序编程效率。     

基于八叉树和方向包围盒的自由曲面加工干涉检查的简化算法

基于分层方向包围盒（OBB）和八叉树空问剖分法,采用分离轴理论,利用离散刀位点间的关联性。针对自由曲面五轴加工的全局干涉问题,给出了一种刀具干涉初步检测的简化算法。应用八叉树的分层结构,只有节点发生干涉,才需要对子节点进行进一步处理。由于刀具路径离散位置的连续性,采用设置缓冲区法来减少需要处理的节点数,从而有效降低了算法的复杂性。     

复杂曲面的五轴加工无干涉刀具路径生成技术研究

基于微分几何理论,对复杂曲面环形刀无干涉刀具路径生成算法进行研究,对复杂曲面进行曲面划分,在此基础上建立环形刀五轴加工模型,进行走刀步长、加工行距和相邻刀触点等的计算,并提出通过选择最佳刀具尺寸和改变刀具姿态进行干涉避免的方法.与其它环形刀刀具路径生成算法相比,本文提出的算法具有更高的准确性和可靠性.     

基于宏程序的线性变半径圆角曲面铣削加工应用研究

线性变半径圆角曲面在复杂类零件中应用较广,通过运用数学知识对刀位点进行数值计算,利用宏程序编写数控程序代码,能够使数控机床快速、准确的实现自动加工。采用通用的FANUC 0i mate-MC数控系统,完成了线性变半径圆角曲面宏程序编制,在宏程序起始段赋予正确的数据到相应的变量,能够准确地控制球刀刀位点的运行轨迹,确保线性变半径圆角曲面加工精度达到要求。     

基于工况匹配的进给速度动态优化研究

为了提高自由曲面类零件的加工效率和加工质量,提出了一种基于工况匹配理论的进给牢优化方法,以常用的典型工况为基础,进行工况分析、定义,得到基本工况进给优化模型.在刀位点邻域内对被加工的自由曲面类零件进行相应典型曲面结构类型的近似,并根据加工过程中刀位点处的曲率、走刀方向、刀轴矢量等进行工况匹配,得到匹配的工况序列,进行基于工况匹配的进给速度的优化,以达到对自由曲面类零件加工中进给速度优化的目的.     

多自由度铣削螺旋曲面的变安装角问题研究

针对国内复杂异形螺杆加工现状,基于盘铣刀无瞬心包络理论率先提出多自由度变安装角数控铣削复杂异形螺杆的螺旋曲面,建立了它的计算模型;它使空间编程问题归结到平面上,减少模型造成的计算误差,提高了刀位点计算准确性,大大改善螺杆数控加工的精度;减小了刀具与工件发生干涉的概率,扩大螺杆的加工范围.     

模具型腔电火花创成加工无干涉运动轨迹生成研究

针对电火花创成加工具有复杂自由曲面的模具型腔,提出利用简单圆柱形电极在五坐标联动电火花机床上加工自由曲面无干涉电极运动轨迹的生成算法,并对电火花加工过程中的电极损耗进行了补偿,提高了曲面的加工质量和加工精度。     

车铣加工UG-CAM制造技术研究与应用

应用TCL（Tool Command Language）开发了车铣加工中心BUNMOTECS192FT后处理模块,实现了该机床刀具中心点B轴随动的高级功能,利用UG～CAM数控编程技术,使用平头立铣刀,在车铣加工中心进行C、X、y轴联动,完成了零件曲面加工刀轨设计,解决了T型铣刀加工曲面环槽干涉问题,通过将平头立铣刀轴与曲面法线倾斜一定角度,避开平头立铣刀底齿中心切削,达到零件精度要求。     

自由曲面五坐标数控加工中几个关键问题的研究

自由曲面用平头立铣刀五坐标数控加工可以明显地提高切削效率和零件表面质量,但无干涉刀位产生一直是个难以解决的问题,本文对其中的几个关键问题进行了研究,导出了平头立铣刀的有效切削半径的一种计算方法,给出了自适应走刀步长度算法和切削行距的计算公式,最后给出了无干涉刀位生成方法,并用实例验证了方法的可行性,为提高加工效率和精度提供了有效途径。     

曲面数控加工精度的研究

分析了影响曲面数控加工精度的因素,研究并提出了从数控程序设计、工艺系统和控制系统等方面提高曲面加工精度的方法。结果表明：数控加工工艺系统特性和数控系统误差是影响加工精度的重要因素,应尽量购置高精度的机床和数控系统,或采用工艺手段,或设置相应补偿参数,由系统自动补偿功能消除;程序设计的优劣也是影响加工精度的主要因素,应从刀具、加工方法、进退刀与走刀方式的选择和刀具路径规划的验证等方面采取措施,以保证曲面加工精度。     

Tool deflection compensation in peripheral milling of curved geometries

This paper presents compensation of surface error due to cutting force-induced tool deflections in a peripheral milling process. Previous research attempts on this topic deal with error compensation in machining of straight geometries only. This paper is concerned with peripheral milling of variable curvature geometries where the workpiece curvature changes continuously along the path of cut. In the case of curved geometries, both process geometry and the cutting forces have shown to have strong dependence on workpiece curvature and hence variation of surface error along the path of cut. This calls for a different error compensation strategy than the one which is normally used for machining straight geometries. The present work is an attempt to improve accuracy in machining of curved geometries by use of CNC tool path compensation. Mechanistic model for cutting force estimation and cantilever beam model for cutter deflection estimation are used. The results based on machining experiments performed on a variety of geometries show that the dimensional accuracy can be improved significantly in peripheral milling of curved geometries.     

5-Axis adaptive flank milling of flexible thin-walled parts based on the on-machine measurement

Deformation of the part and cutter caused by cutting forces immediately affects the dimensional accuracy of manufactured parts. This paper presents an integrated machining deviation compensation strategy based on on-machine measurement (OMM) inspection system. Previous research attempts on this topic deal with deformation compensation in machining of geometries in 3-axis machine tools only. This paper is the first time that concerned with 5-axis flank milling of flexible thin-walled parts. To capture the machined surface precision dimensions, OMM with a touch-trigger probe installed on machine׳s spindle is utilized. Probe path is planned to obtain the coordinate of the sampling points on machined surface. The machined surface can then be reconstructed. Meanwhile, the cutter׳s envelope surface is calculated based on nominal cutter location source file (CLSF). Subsequently, the machining error caused by part and cutter deflection is calibrated by comparing the deviation between the machined surface and the envelope surface. An iteration toolpath compensation algorithm is designed to decrease machining errors and avoid unwanted interference by modifying the toolpath. Experiment of machining the impeller blade is carried out to validate the methodology developed in this paper. The results demonstrate the effectiveness of the proposed method in machining error compensation.     

自由曲面平头立铣刀五轴数控加工轨迹的计算方法

提出了一种在参数坐标系下自适应步长和行距的计算方法 ,该算法考虑了不同刀具接触点处的曲率差异 ,在满足加工精度和粗糙度的前提下 ,又能有效地提高加工效率。该算法适合加工汽车车身模具等曲率变化大的曲面。文中还给出了刀位计算公式。     

Effect of direction of parameterization on cutting forces and surface error in machining curved geometries

The present paper investigates the effect of two variables, namely direction of parameterization and cutter diameter on process geometry, cutting forces, and surface error in peripheral milling of curved geometries. In machining of curved geometries where the curvature varies continuously along tool path, the process geometry variables, namely feed per tooth, engagement angle, and maximum undeformed chip thickness too vary along tool path. These variations will be different when a given geometry is machined from different parametric directions and with different cutter diameters. This difference in process geometry variations result in changed cutting forces and surface error along machined path. This aspect has been studied for variable curvature geometries by machining from both parametric directions and using cutters of different diameter. The computer simulation studies carried out show considerable amount of shift in the location of peak cutting forces with the change in cutting direction and cutter diameter, particularly in concave regions of workpiece geometry. A new parameter γ that relates the instantaneous curvature of workpiece with cutter radius is defined. The larger value of γ is an indicator of greater shift in the location of peak forces from the point of maximum curvature on the workpiece. The simulation results are validated by carrying out machining experiments with curved workpiece geometry and are found to be in good agreement.     

螺旋曲面的四自由度加工方法

文章在研究螺旋曲面的加工原理的基础上,提出以工件旋转、刀具的坐标变化以及刀具的螺旋角度变化为基础,按空间包络法计算刀触点轨迹,由四轴插补形成了刀具沿螺旋线方向的进给运动,从而实现了前后两个加工截面之间的螺旋位置关系。该方法在国内首次提出四轴坐标系下应用无瞬心包络铣削理论实现螺旋曲面加工,为四轴联动数控机床加工复杂螺旋曲面提供了可靠的理论基础。     

圆环面刀五坐标铣削加工复杂曲面干涉避免研究

将圆环面铣刀等效为变直径平底铣刀,基于圆环面铣刀有效切削轮廓曲率与刀触点曲面法曲率匹配,初定刀具姿态,再利用通过圆环面刀圆角中心线的圆柱面与曲面等距面求交,推导了交线上各点坐标的计算公式。利用交线上干涉点数据,计算并调整刀具姿态,避免切削刃后缘和侧缘过切被加工表面,消除瓶颈干涉。此方法比起用刀触点曲率半径计算并消除瓶颈干涉,是一种更全面、合理、可行的实用方法。