自由曲面五轴变步长数控加工刀轨生成方法

为了在满足逼近误差要求的同时最大程度减少冗余刀轨,对自由曲面提出了一种五轴变步长数控加工刀轨生成方法.首先对刀触点轨迹基于线性误差计算出初始刀触点点集,再以局部干涉调整前倾角的方式计算出无干涉刀位点和刀轴矢量;以最大非线性误差刀位处到刀触点轨迹的最小值作为相邻刀位点之间的逼近误差,并基于数据点自适应离散法计算逼近误差;...     

曲面造型及数控加工刀具轨迹生成方法的研究

依据双三次均匀B样条曲面造型理论 ,运用等参数线加工方法 ,给出一种较为简便的曲面造型及数控加工刀具轨迹的生成方法     

自由曲面数控加工刀具轨迹生成的约束条件分析

在提出自由曲面数控加工过程和刀具轨迹的规划原则情况下,分析无干涉控制、恒表面速度进给、伺服能力控制和相邻加工曲线影响等轨迹控制的约束条件,实时对轨迹的生成进行系统优化控制。通过系统分析刀具轨迹生成的约束条件,为刀具轨迹优化控制提供决策,对提高自由曲面的切削质量和加工效率具有重要意义。     

Tool path generation for machining compound surfaces with extended cut region method

Presented in the paper is a novel tool path generation method for 3-axis NC machining of compound surfaces. Tool path generation procedure consists of two core steps: firstly, the extended cut region (ECR) of every surface is constructed; secondly, CL-curves are computed on every ECR and the final tool paths are achieved by sorting, trimming and connecting the CL-curves. The developed ECR method can solve the gouging problems caused by tangent discontinuity, surface overlap or surface gap among surface elements. The proposed method has been implemented and applied to tool path generation in a general CAM system that has been developed by authors. Our case study has demonstrated the validity of the proposed algorithms.     

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.     

A CL surface deformation approach for constant scallop height tool path generation from triangular mesh

In this paper, we present a cutter location (CL) surface deformation approach for constant scallop height tool path generation from triangular mesh. The triangular mesh model of the stereo lithography (STL) format is offset to the CL surface and then deformed in accordance with the deformation vectors, which are computed by the slope and the curvature of the CL surface. In addition, the tool path, which is computed by slicing the deformed CL surface, is inversely deformed by those same deformation vectors to a tool path with a constant scallop height. The proposed method is implemented, and a tool path is generated and tested by simulation and by numerical control (NC) machining. The scallop height was found to be constant over the entire machined surface, demonstrating much better quality than that of mesh slicing, under the same constraints for machining time.     

The implementation of adaptive isoplanar tool path generation for the machining of free-form surfaces

Machining of steep regions is an important research topic in the machining of free-form surfaces. A new tool path generation algorithm to adaptively machine free-form surfaces has been recently developed. However, similarly to many newly emerged methods, so far it has not been used in industry because no commercial platform is currently available and the user-developed system is not robust enough for industrial applications. To solve this problem, this paper presents a new implementation method by integrating it in a commercial CAD/CAM system (Pro/Engineer). With this strategy, other than conducts detailed computations for parameters, such as scallop heights and forward steps, or designing the non-cutting functions such as engaging and retracting methods, which are routines in every tool path generation process, the implementation utilizes existing tool path generation templates in Pro/E to generate the required tool paths. This makes the tool path generation process easier and the tool paths generated more practicable because the integration is relieved of the time-consuming routine calculation and the entire cutting and non-cutting functions in the commercial system are transparent to users. Based on the API of Pro/E, the new tool path generation method was successfully implemented and cutting tests were conducted. Not losing generality, the implementation could also be conducted in other commercial systems as similar templates are available in these systems as well.     

基于网格曲面上空间填充曲线刀具路径生成算法研究

在细分网格曲面上,用最短哈密顿回路法通过连接网格节点去寻找最优路径,以形成填充曲线刀具路径。将空间曲面细分成有限四边形网格后,结合无向网上最短哈密顿回路求解算法,通过构建代价树的方法求解最短路径。应用了邻接矩阵的形式描述图形,及基于矩阵法数据存储的度数消减算法判断和处理图形,构建了空间网格曲面上最短哈密顿回路生成算法。通过一个曲面填充实例验证了构建算法的正确性,及用此方法生成曲面加工刀具路径的可行性。     

自由曲面加工中考虑干涉的刀具路径安排

研究了自由曲面加工中无干涉刀具路径的安排,推出了一种创新的干涉检查方法,将干涉检查和加工刀具路径安排分别进行,加快了数控加工过程,提高了精度,并将该方法应用于三种常用的刀具体,通过实例验证了本法的合理性.规划刀具路径时,先按照某个参数方向的曲率半径和最大弦偏差确定加工步长,然后再按照另一个参数方向的曲率半径和残瘤高度来确定相邻两条刀具路径间的加工步距,最后跳过识别出的干涉区域安排加工路径.     

离散数据曲面的三轴数控粗加工代码生成算法

介绍一种用于离散数据的三轴数控粗加工代码生成算法。该算法以离散数据点为输入信息,先构建一个网格曲面,然后通过一系列的计算步骤,最终得到用于实现离散数据曲面粗加工的数控代码。详细阐述该算法的推导过程,并给出算法的实现细节。该算法被证明具有良好的使用价值。     

组合曲面叶片的螺旋加工刀位轨迹生成

为提高叶片加工质量和改进现有螺旋加工方法,提出了一种新的针对组合曲面造型叶片的四轴螺旋加工方法.该方法在叶片曲面造型过程中,将叶片曲面分割为叶盆、叶背、前缘和后缘四个区域.根据组合曲面叶片造型,提出了组合曲面叶片螺旋加工刀位轨迹生成方法和切触点的计算公式.最后,基于UG软件平台,以二次开发方式编制了相应的数控编程模块.生成了连续光滑的叶片螺旋加工刀位轨迹.试验结果表明,该方法能够实现叶片的四坐标螺旋加工,并可有效提高叶片的加工质量.     

离散点云等残留高度数控加工刀轨生成方法

为了最大化刀轨行间距,从而减少刀轨总长度,针对离散点云提出了一种等残留高度刀轨生成方法。提出以点云局部轮廓点集直接生成残留高度点的迭代计算方法,再根据残留高度点和点云局部点集迭代计算出下一行等残留高度刀位点,从而获得等残留高度刀轨。算法无需点云等距或曲面重构,为了提高算法效率,提出了算法所需数据初值的优化计算方法。最后对典型的点云模型生成刀轨,与等行距刀轨相比,提出的算法生成的等残留高度刀轨总长度大幅减少,验证了算法的可行性和有效性。     

Tool path generation for machining free-form pockets using Voronoi diagrams

Voronoi diagrams for closed shapes have many practical applications, ranging from numerical control machining to mesh generation. Curve offsetting based on Voronoi diagrams avoids the topological problems encountered in the traditional offsetting algorithms. In this paper, we propose a procedure using Voronoi diagram-based tool-path generation for machining pockets with free-form boundaries. A pocket can be bounded by 2D free-form curve elements that are differentiable twice. The procedure consists of three steps:

Non-constant parameter NC tool path generation on sculptured surfaces

An algorithm for three-axis NC tool path generation on sculptured surfaces is presented. Non-constant parameter tool contact curves are defined on the part by intersecting parallel planes with the part model surface. Four essential elements of this algorithm are introduced: initial chordal approximation, true machining error calculation, direct gouge elimination, and non-constant parameter tool pass interval adjustment. A software implementation of this algorithm produces graphical output depicting the tool path superimposed over the part surface, and it outputs cutter location (CL) data for further post-processing. Several applications examples are presented to demonstrate the capabilities of the algorithm. The results of this technique are compared to those generated from a commercially available computer-aided manufacturing program, and indicate that equivalent accuracy is obtained with many fewer CL points.Notation C cutting curve - C ¹ cutting curve tangent - CC ₀,CC ₁, ... cutter contact points - d chordal deviation - /_ABC triangle - w incremental step in parameterw - ABC angle - a small quantity - l chord length - n _s ,n _p , ... normal vectors - P, P _r ,P _c ,P ₁ ,P ₂ , ... space point - Q parametric equation of a surface - R radius of a ball-end milling tool - TC ₀,TC ₁, ... tool center points - u, v, u _s ,u _c ,w, t parameters - angle - curvature - h cusp height - T machining tolerance     

Incomplete two-manifold mesh-based tool path generation

This paper presents a new paradigm for three-axis tool path generation based on an incomplete two-manifold mesh model; namely, an inexact polyhedron. When geometric data is transferred from one system to another system and tessellated for tool path generation, the model does not have any topological data between meshes and facets. In contrast to the existing polyhedral machining approach, the proposed method generates tool paths from an incomplete two-manifold mesh model. In order to generate gouge-free tool paths, cutter-location meshes (CL-meshes) are generated by offsetting boundary edges, boundary vertices, and facets. The CL-meshes are sliced by machining planes and the calculated intersections are sorted, trimmed, and linked. The grid method is used to reduce the computing time when range searching problems arise. The method is fully implemented and verified by machining an incomplete two-manifold mesh model.     

自由曲面数控加工动态仿真研究

在VC++6.0平台上采用OpenGL技术开发一种自由曲面数控加工过程仿真系统。该系统可根据自由曲面的不同造型,规划出适当的刀位轨迹,生成G代码;实现交互控制,完成设计曲面的成型加工,并动态显示加工路径。     

自由曲面三坐标加工等间距刀具路径规划

为提高自由曲面数控加工的切削效率,改善刀具的受力状态,提出了一种自由曲面三坐标加工等间距刀具路径规划方法.分析了在实际加工过程中可采用的几种刀具路径规划方法及其实现等距加工的约束条件.研究了等间距刀具路径的计算方法,并针对计算过程中出现的逼近误差校验和刀具路径延伸与裁剪问题给出了解决方法.对等参数线法和等距截面法进行了比较,表明应用该方法规划自由曲面刀具路径,可提高走刀路径对曲面形状变化的适应性和切削行间距分布的均匀性.     

一种用于多面体加工的圆弧刀轨生成算法

为提高多面体模型的加工效率,提出了一种用于多面体加工的圆弧刀轨生成算法。采用截平面和多面体模型的等距模型求交来计算初始直线刀轨;由等距模型的顶点曲率估算刀位点处沿刀轨方向和刀轨间隔方向的曲率半径,并根据残留高度确定刀轨行距。提出了基于刀位点曲率半径调节的圆弧拟合算法,算法引入拟合约束条件和曲率半径调节系数;在拟合精度范围内,迭代确定曲率半径调节系数,从而确定拟合圆弧。实验结果表明文中方法生成的刀轨保持G1连续且包含的圆弧段数量较少,有利于提高加工效率。     

基于Hilbert填充曲线的自由曲面刀具路径规划研究

利用平面Hilbert填充曲线生成方法简单、易于控制填充疏密的优点,将其用于了自由曲面数控加工刀具路径的生成.对平面Hilbert填充曲线的生成原理进行了研究,用矩阵运算的方法生成该曲线.结合自由曲面的形成过程,提出将平面Hilbert曲线通过与曲面参数域相对应的方法映射到曲面上,进而生成加工刀具路径的思想.最后用一个具体应用实例验证了生成平面Hilbert曲线方法的正确性,和用此曲线作为数控加工刀具路径的可行性.通过与经典刀具路径生成方法比较可见该方法具有算法简单,加工余量均匀,加工效率与表面质量高的优点.     

一个曲面数字化模型及其在数控加工中的应用

通过提出一个新的曲面数字化模型，建立了一个新的参数曲面数控加工刀位点生成方法。该模型的精度控制准则消除了现有的刀位点计算误差分析中的不可靠因素。同时，该曲面数字化模型的建立使刀位点生成速度得到有效的提高