基于双节点插值的刀具干涉检查算法

介绍了基于双节点插值的刀具干涉检查的算法。首先构建数字化模型,利用离散三角片代替原始曲面,通过数字化网格节点的竖直线与三角片的刀位面和保护面求交,并取Z值最大的交点为无干涉刀位点;然后再用双节点插值检查因走刀步长不合适而产生的干涉问题,保证生成的刀位轨迹是无干涉刀位轨迹。该算法完全采用几何求交运算,过程简单且精确度高。     

5轴叶轮粗加工过切与碰撞综合检测修正研究

针对复杂多曲面叶轮的5轴粗加工刀轨自动生成问题,提出一种基于使用平头立铣刀的无过切,干涉的刀具轨迹生成算法。通过对整体叶轮5轴加工中可能出现刀具与叶片干涉的问题,提出了一种干涉检测方法。依据检测结果对干涉进行处理,从而避免实际加工时干涉的发生。方法考虑了刀具运动路径上全部刀位点与叶轮的位置关系,计算量小,对于叶轮数控加工编程中大量刀位数据的干涉检查,可以显著地节省计算机运算时间。     

基于Z-buffer的组合曲面圆环面刀具加工方法

为解决组合曲面五轴加工问题提出一种基于计算机图形学Z-buffer技术的圆环面刀具刀位生成算法。首先借助Z-buffer技术确定刀位计算的检测区域,然后在保证圆环面刀具和检测区域不干涉的前提下调整刀位,使刀具端面和模型曲面充分贴合,从而得到更宽的加工行宽。算法充分利用计算机硬件的快速高效性,直接对加工检测区域内的点进行读取和存贮,避免复杂的搜索和迭代过程。算法过程中集成对刀位干涉的检测和避让,可直接生成无干涉的刀位数据。刀位算法计算过程使用曲面的多面体信息,适用于以裁剪曲面为元素的组合曲面模型的无干涉刀位的计算。针对某组合曲面模型进行刀位计算和仿真,仿真结果相比传统的球头刀加工算法效率提高了10倍。最后对生成的刀轨进行了实际加工试验验证。     

基于MMR的三角网格曲面五轴加工刀轨生成算法

为了提高三角网格曲面五轴加工的加工效率,提出了基于最大材料去除率(maximal materialremoval rate,MMR)的平底刀五轴加工刀轨生成算法。首先计算无曲率干涉且具有最大材料去除率的网格曲面五轴加工的刀具方位角;然后在确定网格曲面可能干涉区域的基础上,提出刀触点处干涉性假设,并以最大材料去除率、刀具无曲率干涉和全局干涉为约束条件,采用二分法确定具有最大材料去除率的无干涉刀具方位角;最后采用截面线法生成三角网格曲面MMR平底刀五轴加工刀轨。通过实验验证了采用文中算法生成的刀轨进行加工能够获得较高的加工效率和表面质量。     

一种快速的自由曲面三轴数控加工干涉检查方法

通过深入研究提出了一种直线段相对于圆形窗口位置关系的快速判别方法 ,以此方法可以大大提高分析逼近曲面的三角片与刀具在刀轴方向的投影之间关系的效率 ,从而加快了自由曲面三轴数控加工的干涉检验速度     

复杂腔槽五轴数控加工的干涉检查及修正算法研究

针对复杂腔槽多轴数控加工的干涉问题进行了分析研究,进而给出腔槽侧面及底面无干涉刀位的计算方法。对于开口槽侧面边缘处的加工,通过检验侧面边缘与刀轴的干涉而确定粗加工走刀终止条件;对于腔槽底面加工,提出了刀具与底面及相临侧面间干涉的定量计算,并在此基础上根据干涉量一次性修正刀位,生成无干涉的合理刀位。     

一种快速的自由曲面三轴数控加工干涉检查方法

通过深入研究提出了一种直线段相对于圆形窗口位置关系的快速判别方法，以此方法可以大大提高分析逼近曲在的三角片与刀具在刀轴方向的投影之间关系的效率，从而加快了自由曲面三轴数控加工的干涉检验速度。     

曲面平头刀加工无干涉刀位轨迹自动生成的算法研究

提出了一种新的曲面平头立铣刀加工无干涉刀位轨迹自动生成的算法。该方法将曲面分成凸区域及非凸区域,将对凸区域采用快速算法,而非凸区域则进行干涉检查和处理。论述了三轴及五轴加工时局部刀具过切干涉和全局刀具干涉的检查和处理。     

带倒角平底刀曲面加工干涉刀具轨迹生成

对自由曲面ＮＣ加工中刀具轨迹生成技术和干涉处理方法进行了分析,以同面模型→刀具接触点数据→无干涉刀位数据为基本求解策略,研究开发出适用于带倒角平底刀无干涉刀具轨迹生成的新算法。该算法具有干涉检测彻底、处理效率高、稳定性好等优点。     

裁剪NURBS曲面数控加工刀轨干涉处理

提出一种基于裁剪NURBS组合曲面的适合于球头刀、平底刀、圆角刀的刀具轨迹干涉检查和消除的算法,该算法将裁剪风景区面用三角片逼近表示,将刀具轨迹干涉检查和消除问题转化为刀具曲面与三角片的几何相关性测试,通过建立裁剪NURBS曲面的包围盒等方法进行干涉预处理,提高了干涉处理速度;推导出不需离散刀具曲面的干涉量计算方法,提高了干涉量计算精度,实践表明,该算法快速、精确、稳定,通用性好。     

大型船用螺旋桨桨毂粗加工刀具路径规划研究

针对大型船用螺旋桨毛坯余量较大,相邻桨叶间存在重叠区,现有加工方法吊装复杂、需要二次装夹且叶根桨毂加工周期长等问题,提出了一种多轴对称加工叶根桨毂方案,并依据加工方案,应用定轴加工方法研究桨毂粗加工刀具路径规划。根据桨毂曲面特征,计算走刀行距与步长;基于定向包围盒(Oriented Bounding Box,OBB)干涉检查算法划分加工区域;在此基础上分析切削参数恒定时,横向行切、纵向行切和环切3种刀具路径规划方法对桨毂加工效率的影响。研究结果可为正确选择桨毂粗加工刀具路径规划方法和后期大型船用螺旋桨叶根桨毂加工装置研发提供理论基础。     

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.     

Optimal CNC plunge cutter selection and tool path generation for multi-axis roughing free-form surface impeller channel

Plunge milling is the most effective way for rough machining of impeller parts, but previous research had not considered the optimization of plunge cutter selection and tool path. In this paper, a new method for optimizing the plunge cutter selection and tool path generation in multi-axis plunge milling of free-form surface impeller channel is proposed in order to improve the efficiency in rough machining. Firstly, in the case of fixing a rotation axis at a certain angle in five-axis machine, a mathematical representation is formulated for the geometric model of the cutter interfering the impeller, and an optimization model of the cutter size is established at a cutter contact point on the impeller channel surface, so the largest tool could be determined. Secondly, by analyzing the machine tool movement characteristics, the geometric constraint model of the plunge tool path which relative to the largest tool, step distance, and row space is established, and a tool orientation calculation method of impeller channel machining is given, and then, the plunge tool path and tool orientation could be obtained. Finally, the generated tool path and tool orientation are simulated and verified in practical processing. Simulation and experimental result shows that the rough machining efficiency of the impeller part is improved up to 40 % with this method.     

Influence of the phase composition and microstructure of plasma cladding Fe-Cr-Ni-C alloy coating on residual stress and crack formation

Tool path generation is one of the key challenges in multi-axis sculptured surface machining. Besides geometry accuracy, machining processes have been considered in tool path generation in order to improve machining quality and efficiency as far as possible. However, so far, the machine tool accuracies have not been yet fully taken into account during tool path generation. Contour accuracy is one of the most important precision indexes to guarantee the machining quality of sculptured surfaces. One of the major reasons causing contour error is the dynamic mismatch between feed axes of machine tools. In this study, the mathematic relationship between the cutting direction, dynamic mismatch of feed axes and contour error is theoretically established. The mathematic relationship can be used to calculate the optimal cutting directions which minimize the contour error caused by dynamic mismatch between feed axes during machining a sculptured surface by a three-axis machine tool. A machining experiment is carried out to verify the mathematic relationship. In the experiment, the tool paths are generated along the optimal cutting direction and other cutting directions for comparison. The results show that the contour error under the case of the optimal cutting direction is much smaller than that under the other cases.     

基于机床运动学约束球头刀多轴加工刀轴矢量优化方法

针对目前航空发动机叶片进排气边加工精度和表面质量较差的问题,提出了一种基于机床运动学约束球头刀多轴加工刀轴矢量优化方法。建立刀位优化变量与刀位数据之间的关系方程,同时建立刀位数据与机床回转轴角度之间的运动变换方程,从而推导出刀位优化变量与机床回转轴角度之间的关系方程。通过求解上述方程得到球头刀多轴加工复杂曲面的刀轴矢量计算公式。在此基础上,给出球头刀多轴加工刀轴矢量优化方法和刀轨生成方法。同时,以某航空发动机叶片为例,分析了本文算法和Sturz算法对机床回转轴角度的影响。分别利用本文算法和Sturz算法生成该叶片进气边加工的刀轨,并在五轴数控机床上进行加工试验。试验结果表明,该算法能够避免加工过程中机床回转轴的大幅波动,使机床轴运动更加平稳和光滑,从而提高曲面的加工质量和加工效率,具有一定的实际应用价值。     

基于误差模型的三轴联动加工轨迹预补偿方法

为了减小由于进给系统动态特性造成的多轴联动加工轮廓误差,提出了一种基于轮廓误差模型的三轴联动加工轨迹预补偿方法。首先建立了关于轨迹曲率、加工速率及进给系统动态特性参数的轮廓误差模型;然后根据读取的插补数据,利用轮廓误差模型实时预测三轴联动加工过程中的轮廓误差补偿向量并对加工轨迹指令进行补偿;最后通过对圆、变曲率和螺旋线轨迹的MATLAB仿真和机床加工实验,证明该补偿方法将轮廓误差减小了85%以上,可显著提高数控机床加工精度。     

Mesh-based tool path generation for constant scallop-height machining

This paper presents a new approach to mesh-based tool path generation for obtaining constant scallop heights. The mesh surface has recently become the focus of considerable interest, because its geometric computation is simpler and more robust than that of the parametric surface. These advantages make it easy to check and remove interference in the process of tool path generation. The previous tool path generation method based on the mesh surface, however, can generate only one topology of iso-planar type where tool paths have evenly spaced tool path intervals. As constant scallop heights cannot be obtained from evenly spaced tool path intervals, unevenly spaced tool paths based on offset meshes are necessary for reducing the machining time and for easy interference removal. This paper proposes and compares four methods to estimate curvatures from the mesh surface; the curvature is essential for calculating unevenly spaced tool path intervals. This paper also proposes an improved drive surface method to propagate CL-paths unevenly and to generate tool paths with various topologies.     

雕塑曲面体混流式叶片的多轴联动数控加工编程技术

转轮叶片是水轮机能量转换的关键部件,也是最难加工的零件,目前多轴联动数控加工是解决该类大型雕塑曲面零件最有效的加工方法。多轴联动数控加工编程则是实现其高精度和高效率加工的最重要环节。本文介绍混流式水轮机叶片五轴联动数控加工大型雕塑曲面编程中涉及到转轮叶片三维造型、刀位轨迹计算、切削仿真、机床运动碰撞仿真、后置变换等关键技术。通过对这些技术的链接和研究,开发实现了大型叶片的多轴联动加工。     

大型水轮机叶片的多轴联动数控加工编程技术

转轮叶片是水轮机能量转换的关键部件，也是最难加工的零件，目前多轴联动数控加工是解决该类大型雕塑曲面零件最有效的加工方法。多轴联动数控加工编程则是实现其高精度和高效率加工的最重要环节。介绍了大型水轮机叶片五轴联动数控加工大型雕塑曲面编程中涉及到的转轮叶片三维造型、刀位轨迹计算、切削仿真、机床运动碰撞仿真、后置变换等关键技术。通过对这些技术的链接和研究，开发实现了大型叶片的多轴联动加工。