叶轮数控加工中的干涉检查

针对自由曲面离心叶轮多坐标数控加工中可能出现刀具与叶片干涉的问题,提出了一种干涉检查方法。首先计算出叶片曲面的等距面,等距面的偏移距离为刀具半径,再根据所给定的刀位数据得出刀轴的表达式,然后计算该等距面与刀轴是否有交点,如果有交点则存在干涉,否则计算叶片边界线到刀轴的最小距离,若此距离大于刀具半径则无干涉,否则存在干涉。该方法计算量小,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。     

用投影方法进行数控加工干涉检查与修正

解决了数控加工的干涉检查问题。数控加工的干涉检查实际上就是检查刀具曲面和被加工曲面的有向距离。根据有向距离的符号进行干涉与否的判断并由其值（极值）的大小及极值的位一进行干涉修正，利用刀具曲面是一个绕刀轴的旋转面，易抉辅度离散处理的特点，不离散（分割）待检查曲面，而离散刀具曲面，在经度方向上可用刀具轮廓线（母线）绕刀轴旋转得到的一组均通过刀尖点的曲线来逼近，在纬度方向上可用圆心在刀轴上的一组经过同一条毋线的圆来逼近。利用相邻点间的相关性，采用跟踪技术求取离散的刀具曲面嵌入被检查曲面的干涉深度及其位置。     

基于最小距离法的鞋楦加工无干涉刀具轨迹生成

在刀具及鞋楦三维模型离散数据的基础上,通过曲面的空间变换,将干涉检查转化为基于投影方向的最小距离判断,实现了鞋楦加工的无干涉刀具轨迹生成.对于计算刀位点时计算量大的问题,提出了一种针对鞋楦曲面特征的最小距离点的快速搜索方法.实际加工表明,提出的算法能够较好地提高鞋楦的加工质量和效率.     

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。     

组合曲面的五坐标数控加工刀位干涉检查

五坐标数控加工干涉检查是编程技术面临的一个既困难又必须解决的技术问题.为此,提出了一种基于刀具局部坐标系的干涉判别方法,在此坐标系上,直观地描述了不同类型干涉的数学特征,从而将刀具与被加工零件组合曲面的干涉检查问题转化成函数极值问题.     

复杂曲面五轴加工全局干涉检测

针对环形铣刀五轴加工复杂曲面的全局干涉问题,提出了一种基于参数曲面网格划分与刀具包围盒的全局干涉检测算法。首先将加工参数曲面沿参数方向进行网格划分,得到若干离散网格点;然后将环形铣刀的圆柱面用六个平面包围形成刀具包围盒,并通过曲面离散点与形成刀具包围盒的六个平面的位置关系判断曲面离散点是否落入刀具包围盒内;最后判断落入刀具包围盒内的曲面离散点是否在环形铣刀的圆柱体内,若曲面离散点在环形铣刀的圆柱体内则存在全局干涉,否则不存在全局干涉。该方法与传统方法相比极大的提高了全局干涉的检测效率,通过实例验证该方法是可行的。     

复杂曲面五轴加工干涉检查的研究

针对复杂曲面五轴数控加工刀具干涉检测算法复杂且效率低的问题,提出了基于空间三维坐标系变换原理的刀具干涉检查方法,即通过计算曲面上的点在刀具局部坐标系中刀具投影区域内的坐标值与刀具的位置关系来判断是否发生干涉。该方法能够同时检查局部干涉和全局干涉,大大减少计算量,提高检测效率和数控加工效率。为避免干涉,针对不同的干涉形式给出了不同的刀具姿态调整旋转轴和旋转角。通过实例验证了所提方法的可行性和有效性。     

基于反向误差补偿的螺旋曲面成形加工干涉消减方法

为有效提高螺旋曲面成形加工的精度,根据螺旋曲面与成形刀具的相切接触原理,建立了螺旋曲面与成形刀具之间的正反算数学模型;提出一种基于误差反向补偿的干涉消减方法,通过在工件理论廓形上反向补偿干涉量,形成螺旋曲面新的虚拟计算廓形,再以该廓形反向计算成形刀具截形并进行迭代,最终得到可减小干涉误差的成形刀具截形;构建了螺旋曲面成形加工干涉量的计算模型,给出了螺旋曲面成形加工干涉消减流程,并讨论了所提方法的效率和适用范围。通过计算实例验证了所提方法的有效性。     

基于最小距离法的鞋楦加工无干涉刀具轨迹生成

在刀具及鞋楦三维模型离散数据的基础上,通过曲面的空间变换,将干涉检查转化为基于投影方向的最小距离判断,实现了鞋楦加工的无干涉刀具轨迹生成。对于计算刀位点时计算量大的问题,提出了一种针对鞋楦曲面特征的最小距离点的快速搜索方法。实际加工表明,提出的算法能够较好地提高鞋楦的加工质量和效率。
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多轴加工无干涉刀具路径生成算法研究

多轴数控加工中刀具路径的计算直接影响加工零件的精度和加工效率。本文介绍了一种平底刀多轴无干涉刀位轨迹生成算法,在刀轴方向上消除干涉量。首先对参数曲面进行三角离散化,根据曲面相应点的法矢布置初始刀具位姿。构造曲面和刀具的OBB模型,通过包围盒间的快速相交测试得到刀具与曲面的干涉三角片,在此基础上,采用解析方法计算刀具与干涉三角片在刀轴方向上的干涉量,修正刀位点,最后得到无干涉刀位轨迹。     

基于人工鱼群和粒子群优化混合算法的侧铣刀轴轨迹规划

针对圆锥刀侧铣加工非可展直纹面的刀轴轨迹规划问题,采用两点偏置法确定初始刀轴矢量,为评价单个刀位,提出了单刀位下的误差度量函数,即刀轴上各点到非可展直纹面的距离与对应各点到圆锥面的距离差值的平方和最小。为解决每个刀位下的位姿寻优问题,提出了基于人工鱼群（AFS）和粒子群优化（PSO）混合算法的优化方案。仿真结果表明,所提方法在单刀位下的优化过程简单,结果精度高,优化后位姿集合形成的刀具包络误差小。     

Automatic selection of cutter orientation for preventing the collision problem on a five-axis machining

The rotation joints of a five-axis machine tool can offer freedom and appropriate rotation to prevent interference problem between workpiece and the cutter. However, to a five-axis machine tool, it is quite difficult to determine the collision-free cutter orientation. Over this problem, a two-stage cutting tool collision check method is proposed to prevent the collision problem during the cutting process on a five-axis machine tool. The proposed method is capable of determining the collision free ball-end cutter orientation automatically. The first stage is to obtain the tilting and collision-free angle range in the plane that is normal to the tool path obtained. Next, a checking cone generated from this collision-free tool axis range is used for the second collision check. The collision region is formed by the intersection of the neighboring surfaces. This implies a collision-free yaw angle range. The final cutting tool orientation is determined automatically by referring the original spindle axis and the least angular variation from the spindle axis. Finally, the implementation issue is discussed with example.     

基于有向图的刀轴矢量优化研究

针对球头铣刀的五轴数控加工,提出了一种基于有向图的刀轴矢量优化方法。根据刀轴矢量数据量大的特点,提出了建立刀轴矢量有向图的最小优化模型和算法。该方法能获得全局刀轴矢量变化量最小的刀轴矢量序列,将可行域边界上的刀轴矢量加入到有向图的计算中,提高了算法的计算效率。仿真分析表明,该方法优化了刀轴矢量的连续性和光顺性,对于最佳刀具姿态在可行域边界上的加工具有一定的适用性。     

整体叶轮五轴侧铣数控加工方法的研究

为提高整体叶轮的五轴编程和加工的能力,生成合理的刀位文件,在制定出合理的加工工艺的基础上,提出了一种适合于直纹面叶片五轴侧铣加工的刀轴矢量计算方法.对两个相邻叶片的直母线进行插值后,得到的刀轴矢量能完全避免刀具与叶片之间的干涉问题.同时,提出了一种小四边形参数模型来解决直线与自由曲面求交问题,并成功应用于刀心计算中.实例计算表明,所提出的方法能很好地应用于整体叶轮的五轴加工.     

Collision and interference correction for impeller machining with non-orthogonal four-axis machine tool

Aiming at the four-axis machining with inclined rotary working table, an approach for collision and interference correction is proposed in this paper. Based on the principle that the tool axis vector is limited in the corresponding rotation plane of four-axis machine tools, collision and interference can be eliminated by using the rotation of the ellipse which is the intersection of the plane and the cutter surface. And the minimum necessary rotation angle for the cutter to eliminate interference is obtained by solving the quartic polynomial equations with numerical method. Finally, the process techniques involved in impeller machining with non-orthogonal four-axis machine tools are developed thoroughly, and the experiments of free-form centrifugal impeller machining are rendered with details. Experiment results show that the approach is an effective approach to detect collision and avoid interference for four-axis machining and it can be directly implemented into current CAD/CAM software to promote impeller machining in industry.     

Torus cutter positioning in five-axis milling using balance of the transversal cutting force

This article introduces a new torus cutter positioning strategy for five-axis milling of free-form surfaces. This approach ensures elimination of local interference while also allowing better surface quality to be obtained than with positioning proposed by computer-aided manufacturing (CAM) software. In practice, the cutter axis is inclined to the rear in relation to the feed movement. A first inclination for the cutter axis is calculated to allow local interference to be eliminated. Then, an additional inclination is given to tool axis to achieve balancing of the transversal cutting force component perpendicular to the plane containing the tool axis and the feedrate vector. This particular machining situation considerably enhances the cutter's dynamic behaviour and gives better roughness values than those obtained with positioning by CAM software. A positioning method is adapted to the negative rearward inclination of the cutter axis, and it is then shown how transversal cutting force balancing is integrated in the form of an additional inclination. Finally, a comparison of the results obtained after milling with this new positioning and positioning calculated by a CAM program highlights the new method’s advantages.     

Local interference detection and avoidance in five-axis NC machining of sculptured surfaces

The tool interference problem is the most critical problem faced in sculptured surface machining. This paper presents a methodology for interference detection and avoidance in five-axis NC machining of sculptured surfaces with a filleted-end cutter. The surfaces to be machined are divided into convex and non-convex regions. There is no local interference inside the convex regions. For the non-convex regions, based on the analysis of the different local interference, local gouging is first detected and avoided by determining optimal cutter orientations. Rear gouging detection and avoidance algorithms are then proposed for simple smooth surfaces and complex shaped surfaces, respectively. The techniques presented in this paper can be used to generate interference-free tool paths. The realistic results indicate that the proposed method is feasible and reliable .     

复杂曲面投影法精加工刀轨生成

针对复杂曲面投影法精加工问题,提出一种简捷而有效的计算投影轨迹的方法。该算法以减少计算量,提高干涉调整效率为目的。为了避免传统方法中的复杂的曲面偏置问题,提出了一种新的思路,该方法摒弃了先求偏置面再计算投影轨迹并使用对分法处理干涉问题的思路。首先规划导动轨迹,然后将刀触点轨迹沿曲面法向偏置,再利用刀位点到曲面的最短距离进行干涉检测与调整,最后生成了无干涉的投影法轨迹。仿真实验证明,该方法计算量小,可以消除干涉,加工效果好。     

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.