深型腔模具精密加工技术的研究与实现

针对淬硬工具钢切削性能差、深型腔模具加工廓形精度不易保证等问题,提出了一种深型腔模具精密高速加工工艺优化技术.该技术根据构建的加工刀轨长度以及刀具悬伸长度与型腔加工廓形误差之间的数学模型,计算随加工刀轨长度变化的廓形误差值,设计瞬时的螺旋线加工刀轨,运用曲线过渡法,生成了适合深型腔模具精密高速加工的优化刀轨.基于米克朗Duro800高速加工机床,对内星轮模具型腔进行精密加工,结果表明,加工精度可提高IT1～2级,表面粗糙度Ra≤0.8.     

贮箱壁板正三角形型腔加工轨迹及系统研究

为了优化火箭贮箱壁板正三角形型腔加工轨迹和编程系统,提高编程和加工效率,针对轨迹规划方式和系统编程方式进行了研究。提出了一种面向高速加工的型腔铣削轨迹生成新方法,其策略是采用螺旋线的走刀方式,轨迹由直线和相切圆弧首尾连接而成,并采用双向行式方式规划型腔间走刀轨迹,提高加工效率。其次,基于UG-CAM平台,二次开发编程系统,实现了对单个型腔加工轨迹和型腔间移刀轨迹的自动生成,并实现了基于形状特征识别的加工区域批量提取、刀具轨迹的干涉检查与修正,自主设计了简捷的人机交互界面。此研究不仅优化了加工轨迹,还实现了加工系统的快速编程。以火箭贮箱壁板为对象进行试切实验,加工效率提高26.23%。     

任意多岛型腔数控加工路径生成算法研究

提出了一个用于计算具有任意多岛型腔环切加工刀具轨迹的算法.该算法采用干涉标志分别生成型腔轮廓和各个岛的等距偏移轮廓,然后通过二维布尔运算进行偏移轮廓的合并,再进行轮廓生成树的深度优先遍历,可以得到最终的环切加工轨迹.     

基于误差补偿的高速等残留高度刀具轨迹的研究

根据微分几何中短程线的原理,在传统的基于等残留高度刀具轨迹生成方法的基础上,通过判断曲面特性,提出基于曲面特性的误差补偿步长计算法.引入NURBS曲线实现相邻刀具轨迹的平稳过渡,实现高速加工下刀具轨迹行间的平滑优化.以上算法利用Visual C+ +实现,通过仿真得到平稳光顺、载荷均匀的曲面高速加工刀具轨迹.     

等残留高度法中的刀具初始轨迹优化

刀具运动轨迹是数控加工技术的核心部分,它会对数控加工的加工质量和加工效率产生极大影响。等残留高度法是近年来被提出的一种非常高效的刀具轨迹规划方法。传统等残留高度法中,一般选择曲面最长边界作为刀具轨迹的初始轨迹。选择马鞍曲面上沿最大凸曲率方向的曲线作为初始轨迹,结合传统的等残留高度算法,生成覆盖整个加工曲面的刀具轨迹。对比新刀轨算法和传统等残留高度法,实验结果表明,采用新算法生成的刀具轨迹可以有效地提高加工效率。     

基于网络优化的复杂型腔刀具轨迹规划算法

复杂型腔零件的加工是数控编程中的一个难点。从提高加工算法的稳定性和加工效率的角度出发,提出了基于网络优化的复杂平面型腔数控加工刀具轨迹优化算法,分析了轮廓环的等距、自交、集合运算等基本运算,详细论述了基于网络优化的刀具轨迹规划方法并优化了刀具轨迹。     

曲面高速精加工刀具规划的研究

分析了曲面高速加工对刀具轨迹的要求,提出了等残留高度法生成曲面高速精加工刀具轨迹的基本原理。通过微分几何理论计算短程线曲率半径,提出了残留高度刀具轨迹生成算法。     

对称多型腔粗加工刀轨快速生成算法

对具有对称特性的多型腔零件的刀轨规划方法进行了研究，提出了一种新的算法：首先生成其中一个型腔的刀轨，然后通过阵列生成其余刀轨，并对刀轨的进退刀进行处理，从而快速生成完整的、连续的、有序的刀具轨迹。该算法尤其适用于高速加工的刀轨规划，实践表明，可大大提高编程效率．节省加工时间。     

基于等残留高度的光顺刀具轨迹规划算法

提出了一种新的等残留高度光顺刀具轨迹规划算法.针对数控加工中高速铣削时力具轨迹规划方法进行比较和研究,以参数曲面为例,用matlab软件对此算法进行编程,通过控制轨迹线的曲率来保证刀具轨迹光顺性,有利于获得好的加工质量.尤其是对高速铣削加工,此算法具有较大的实际应用价值.     

细分曲面数控加工的研究

数控加工刀具轨迹生成是数控加工编程的基础和关键.本文阐述了细分方法和基于细分曲面的数控加工的关键技术:曲面等距、刀具轨迹的生成等,并对其进行总结和展望.     

A mapping-based spiral cutting strategy for pocket machining

Almost 80 % of the milling operations to produce mechanical parts are produced by NC pocket milling, especially in aerospace and automobile industry. At present, for 2.5D pocket machining, direction-parallel and contour-parallel machining strategies have gained nearly universal acceptance. However, in such tool path, abrupt change of path direction, frequent acceleration and deceleration, and sharp velocity discontinuous are found to significantly limit the machining efficiency of pockets. To address these problems, this paper introduces a method for generating a spiral tool path that maintains a steady-state cutting process by as smoothly as possible curvature evolution of the tool path for pocket machining. First, the machined region of a layer of a pocket is mapped onto a circular domain by means of mesh mapping, which reduces the task of tool path generation from the geometrically complex pocket region to a topologically simple disk. On this disk, a guide spiral is constructed according to a mathematical function constrained by the calculated path interval map. Using the mapping from the pocket to the disk as a guide, the guide spiral is inversely mapped into the interior of the pocket and then a smooth low-curvature spiral path is derived. The generated tool paths are guaranteed to not inherit any corners in the subsequent interior tool paths and allows cutting of the pocket without tool retractions during the cutting operations. Finally, the proposed method is implemented and tested on several typical sample pockets to demonstrate its validity and significance.     

Contour parallel milling tool path generation for arbitrary pocket shape using a fast marching method

Contour parallel tool paths are among the most widely used tool paths for planer milling operations. A number of exact as well as approximate methods are available for offsetting a closed boundary in order to generate a contour parallel tool path; however, the applicability of various offsetting methods is restricted because of limitations in dealing with pocket geometry with and without islands, the high computational costs, and numerical errors. Generation of cusps, segmentation of rarefied corners, and self-intersection during the offsetting operations and finding a unique offsetting solution for pocket with islands are among the associated problems in contour tool path generation. Most of methods are inherently incapable of dealing with such problems and use complex computational routines to identify and rectify these problems. Also, these rectifying techniques are heavily dependent on the type of geometry, and hence, the application of these techniques for arbitrary boundary conditions is limited and prone to errors. In this paper, a new mathematical method for generation of contour parallel tool paths is proposed which is inherently capable of dealing with the aforementioned problems. The method is based on a boundary value formulation of the offsetting problem and a fast marching method based solution for tool path generation. This method handles the topological changes during offsetting naturally and deals with the generation of discontinuities in the slopes by including an “entropy condition” in its numerical implementation. The appropriate modifications are carried out to achieve higher accuracy for milling operations. A number of examples are presented, and computational issues are discussed for tool path generation.     

大型核电叶片的螺旋磨削刀具轨迹生成

为了提高大型核电叶片的磨削加工效率和改进现有的砂带磨削刀具轨迹生成方法,提出了一种针对组合曲面叶片的六轴联动螺旋磨削方法。该方法根据组合曲面相邻边界曲线与曲面造型提出了叶片砂带螺旋磨削切触点和刀具轨迹的计算公式。基于课题组自主开发的编程系统平台编制了相应的数控编程模块,生成了连续光滑的叶片螺旋磨削加工刀具轨迹。与砂带磨削原有的横向、纵向磨削方式相比,大大减少了叶片磨削过程中的让刀时间,提高了加工效率,降低了生产成本。     

叶片专用多轴数控编程技术研究

根据叶片螺旋铣加工专用工艺方法,将叶片视为加工特征,设计出叶片专用多轴数控编程算法:构造螺旋铣切削轨迹、构造回转式进退刀轨迹、四、五坐标刀位点计算、计算螺旋铣加工边界和构造螺旋清根轨迹,并计算得到高质量、高效率的螺旋铣加工轨迹。     

Generation of Tool Paths for Machining Free-Form Pockets with Islands Using Distance Maps

In this paper, we present a new procedure for generating tool paths using discrete distance maps, especially for dealing with free-form shaped pockets with multiple islands. In this procedure, a discrete distance map is computed by shading a right circular cone having the height of a given offset distance, while moving its apex along the boundary curve segments. Using the discrete distance maps, the proposed algorithm effectively extracts the characteristic points or the valid self-intersection points of offset curve segments. For an offset distance, one or more offset profiles are constructed without the topological problems by offsetting the boundary curve segments within the parameter values specified by these chararteristic points, and connecting them into closed profiles using the topological information contained in the distance map. The gouging-free tool path is constructed by connecting these offset profiles, starting from the innermost offset profile. In the proposed method, we do not need any artificial bridges for a pocket with multiple islands to merge the pocket profile and the island profiles into a single boundary profile.     

型腔边界拐角精加工刀轨生成算法的研究

在识别粗加工余料区域的基础上,从均匀径向切削深度、平滑刀轨路径等方面考虑,研究并实现了型腔边界拐角处的精加工刀轨生成算法。采用将拐角区域加工分为多个循环进行渐进切削的策略,可减小径向切深。同时,每一切削循环内切削段和空程刀轨段、各循环之间均采用圆弧过渡,刀轨路径满足一阶连续,从而可减小切削力的变化幅度和方向突变,提高加工精度。     

面向高速加工的复合曲线螺旋轨迹生成方法

针对现有螺旋切削方式仅仅适合圆形或类圆形边界曲面的问题,提出了一种复合曲线螺旋切削法,利用直线圆弧构建规则形状的辅助边界以包容不规则的曲面原始边界,以辅助边界构建光顺网格曲面作为螺旋线的投影曲面,然后桥接投影曲线与平面螺旋线作为驱动曲线从而生成复合螺旋刀路,在避免边界尖角影响的同时保留了刀轨连续的优点,适用于各种具有不规则边界的平坦曲面。软件模拟和实际加工结果表明,复合曲线螺旋切削法有效解决了刀轨的连续性和矢量突变问题,特别适合复合曲面的高速加工。     

数控型腔铣削加工稳定性预测

数控型腔铣削加工过程中,铣刀进入拐角时,刀具-工件间啮合信息的变化通常会引起颤振。针对这一状况,在用半离散算法对刀具-工件啮合状况恒定铣削加工稳定性预测的基础上,结合数控型腔铣削加工过程中加工路径引起的刀具-工件间啮合信息的变化,针对给定的加工路径提出了型腔铣削加工稳定性预测的方法。试验证明,该方法能在数控加工时对型腔加工过程中的铣削稳定性进行成功预测。     

基于支持向量机的点云曲面刀具路径规划

针对单值散乱点云曲面刀具路径规划问题,提出了一种基于最小二乘支持向量机的计算方法。在计算过程中,将点云数据向平面投影,得到二维点集。应用网格划分和边界网格内测量点高斯映射技术,提取平面区域内的边界特征点。用边界特征点定义点云曲面的实际加工区域,在此区域内规划平行等间距刀具路径。应用最小二乘支持向量机拟合点云数据,求得被加工曲面的连续表达模型,经此模型将二维刀具路径数据向三维空间映射,求出刀触点数据。将刀触点经法向偏置计算,求得刀位点。实例验证证明,该方法能较好地解决信息不完备散乱点云曲面刀具路径生成问题。