多轴联动数控加工刀具轨迹的优化算法的研究和实验验证

提出一种新的刀具轨迹优化算法,使相邻加工轨迹间的残留高度值都等于允许残留高度值(规定精度),从而达到最大的切削带宽,消除了干涉.同时采用刀位显示验证方法对加工某叶片模型所得到的刀具轨迹进行验证.实验数据表明,在保证精度的前提下,轨迹数和轨迹长度明显减少,大大提高了多轴联动数控加工的效率.     

多轴联动数控加工乃具轨迹的优化算法的研究和实验验证

提出一种新的刀具轨迹优化算法，使相邻加工轨迹间的残留高度值都等于允许残留高度值（规定精度），从而达到最大的切削带宽，消除了干涉。同时采用刀位显示验证方法对加工某叶片模型所得到的刀具轨迹进行验证。实验数据表明，在保证精度的前提下，轨迹数和轨迹长度明显减少，大大提高了多轴联动数控加工的效率。     

一种新的数控加工刀位迹排列算法的研究

提出一种基于密切曲率法的刀位轨迹预拉优化算法，使相邻加工轨迹同的残留高度值都等于预定的精度，从而达到最大的切削带宽，在保证精度的前提下，大在提高了数控加工的效率。     

基于等残留高度的自由曲面加工刀具轨迹规划

对于曲面加工来说,效率和精度是相互矛盾的2个方面。加工时,用等残留高度法生成刀具轨迹,选择待加工曲面最长的1条边界线作为第1条加工的轨迹线,通过控制相邻刀具接触点的距离,使刀具轨迹间的残留高度均匀一致,依据刀具半径和允许的残留高度,迭代生成另一条刀具轨迹线。等残留高度法生成的刀具路径间的残留高度均为设定值,所生成的刀位点数最少,刀具路径长度最短。采用牛顿法作为等残留高度法的刀位点搜索方法,得到等残留高度刀具轨迹的生成过程。     

自由曲面数控加工刀具轨迹优化算法的研究

提出了一种数控加工刀具轨迹排列优化算法,使相邻加工轨迹间的残留高度都等于最大允许值,在保证精度的前提下,刀具轨迹排列更加合理,轨迹条数和轨迹长度大大减小,加工效果明显提高。     

椭球精加工轨迹及程序设计

数控加工刀路轨迹影响工件的形状和精度。为了保证椭球的形状和精度,根据球头刀外切于椭球的特征,应用数学知识推导出精加工椭球时刀具中心轨迹的参数方程。并求得近似的刀心轨迹和推导的刀心轨迹之间的误差不在工件的尺寸公差之内,说明不能采用近似的刀心轨迹编程。以半椭球面为例,通过控制残留高度值来计算步进角大小,采用连续进给编程的方法编制宏程序,利用仿真软件验证了刀路轨迹正确。该方法极大地提高了椭球的加工精度和效率,为椭球的加工提供了编程方法与策略。     

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。     

一种自由曲面的改进的等残留高度加工方法

自由曲面的数控加工策略直接决定着其加工质量.等残留高度法是一种加工效率和加工质量都较好的加工策略.对于比较复杂或者有突变点的自由曲面来说,由等残留高度法得到的加工轨迹并不平滑.提出了一种改进的基于等残留高度的加工轨迹计算方法,可得到平滑的加工轨迹.     

复杂曲面五坐标数控加工刀具轨迹的规划算法

提出了复杂曲面五坐标数控加工刀具轨迹的规划算法。该算法在保证刀具不与被加工曲面发生干涉的基础上 ,使得刀具扫描面与被加工曲面在刀触点处切平面上每个方向的曲率相匹配 ,由此规划的等残留高度刀具轨迹能改善曲面加工精度和加工效率     

等残留轨迹规划方法在高速加工中的应用研究

在数控加工中,加工轨迹规划方法直接影响到加工的效率及质量,尤其在高速加工中轨迹规划方法合理的选择关系到加工的成败.本文对等残留轨迹方法与等参数线轨迹规划方法的在高速加工中加工效率和加工后表面残留高度进行了分析比较,探讨了两种方法加工效率和表面质量与自由曲面曲率的关系.结果表明等残留高度法能根据自由曲面状况,不同程度的提高加工效率及表面质量,并与曲面曲率具有较大的相关性.     

Direct tool path regeneration for physical object modification from digitized points in reverse engineering

To reuse the tool paths in tool path regeneration for physical object modification in reverse engineering, this paper presented a novel CL tool path regeneration algorithm based on the CL tool path generated from the measured data points. When a physical part captured is modified, the new tool paths for the modified part can be regenerated efficiently by only calculating the affected CL tool paths on the modified region. With this strategy, if a measured physical part has been modified and the CL tool paths were generated directly from its corresponding digitized points, the affected CL tool paths are identified first; then, new CL tool paths are regenerated and used to replace the affected CL tool paths for a given machining accuracy δ. The tool paths not affected are maintained in the new NC-codes. For the method, only the tool paths for the modified regions need to be regenerated; thus, the tool path, which combines the original and modified tool paths, can be regenerated efficiently.     

Constant scallop-height tool path generation for three-axis discrete data points machining

This paper presents a new approach for the determination of constant scallop-height tool paths in the machining of discrete data points using three-axis ball-end milling. Compared with the existing approaches for surfaces, this approach avoids offsetting data points, which is complex and time consuming. This paper firstly creates the local coordinate system centered at each CL point of the current path to calculate the corresponding scallop point and then the similar local coordinate system is created at each scallop point to calculate the wanted CL point of the next tool path. The tool paths generated by the approach keep the scallop-height constant and meet the step error requirement. The experiment result indicates that the approach is feasible and efficient and the overall tool path length can be reduced significantly compared with the iso-planar method.     

Master CAM刀具路径对偏心工件的加工效果

为解决运用Master CAM软件的外形铣削刀具路径对偏心工件加工时,存在浪费刀具路径的现象,需要作做辅助线纠正的问题,尝试不作辅助线,使用Master CAM挖槽刀具路径对偏心工件加工;通过对挖槽各种类型的刀具路径及外形铣削刀具路径,对偏心工件的加工效果进行比较,得出了边界再加工挖槽刀具路径适合对偏心工件加工的结论。     

Experimental investigation on various tool path strategies influencing surface quality and form accuracy of CNC milled complex freeform surface

Four tool path strategies such as equal-interval tool paths, parallel tool paths, parallel–tangency tool paths, and freeform tool paths are proposed in computer numerical control milling of a complex freeform surface. The objective is to understand how 3D tool paths influence their machining efficiency, surface quality, and form accuracy. In this study, their scallop heights were less than or equal to 15 μm. First, their scallop heights distributions and 3D tool path distances were theoretically analyzed; then, four tool path strategies were investigated with reference to machining efficiency, surface texture height, surface roughness, and form errors. It is shown that scallop heights distribution can be used to display the surface texture state and predict tool path distance. Experimental results indicate that the surface texture height, the surface roughness, and the form errors were nearly identical on the machined flat location and surface for various tool path strategies, whereas their surface quality and form accuracy are easily destroyed on the abrupt ones except for the parallel tool paths. Although the freeform tool paths produce the shortest tool path distance through 3-axes driving mode, the parallel tool paths offer the best surface quality and form accuracy through 2-axes driving mode. This is because the 3-axes driving and its vector changes on abrupt location easily lead to large machine vibration and movement errors. It is confirmed that the parallel tool path strategy with 2-axes driving mode can improve the surface quality and form accuracy in actual milling of a complex freeform surface.     

复杂型腔行切轨迹生成算法研究

复杂型胶类零件的加工是数控编程中的一个难点.本文从提高加工算法的稳定性和加工效率的角度出发.提出了一个复杂平面型腔数控加工的优化算法.即通过二维环的等距、自交、集合等基本运算.按“端点同环最短距离优先剖面线算法”规划并优化刀具轨迹.最后给出了应用实例.     

刀具路径对单点渐进成形的影响

在单点渐进成形技术中,刀具路径是加工时刀具在空间中的运动轨迹。本文使用有限元分析软件ANSYS／LS—DYNA模拟了刀具路径对渐进成形过程的影响。模拟结果表明：当刀具四点压下时,模拟的轮廓曲线对称性最好,底面上凸的幅度较小;同时,板材的最大等效应变和主要变形区节点的塑性应变较小,板材连续逐层变形能力较好。     

基于遗传算法的笔式加工刀具路径优化

为缩短笔式加工时间和提高加工效率,提出了一种新的基于遗传算法的刀具路径优化方法。笔式加工的特点决定了生成的刀具路径为一系列离散的切削路径段,为了精简搜索数目,将每段刀具路径看作两个遗传基因。使用十进制码构造分段染色体模型,采用改进的遗传算法对笔式加工分段路径进行优化排序,得到刀具路径排布的近似最优解。实验结果表明:改进的自适应遗传算法比一般遗传算法搜索速度提高若干倍,可以明显缩短加工路径的总长度。     

Form-truing error compensation of diamond grinding wheel in CNC envelope grinding of free-form surface

In computer numerical control (CNC) grinding of free-form surface, an ideal arc profile of trued diamond grinding wheel is generally employed to plan 3D tool paths, whereas its form-truing errors greatly influence the ground form accuracy. A form-truing error compensation approach is proposed by using an approached wheel arc profile to replace the previously designed ideal one. The objective is to directly compensate the trued wheel arc-profile errors. It may avoid the time consumption of traditional approach that compensates the measured coordinate point errors of workpiece to an iterative grinding operation. First, the 3D tool path surface was constructed to plan the 3D tool paths. Second, the CNC arc truing of grinding wheel was conducted to analyze the form-truing error distribution relative to the applied wheel arc profile. Then, the form-truing error compensation was carried out in CNC envelope grinding. Finally, the iterative closest point (ICP) algorithm was used to match the measured coordinate points of workpiece to ideal free-form surface. It is shown that the 3D tool path surface constructed is practicable to plan arbitrary 3D tool paths for the form-truing error compensation. The ICP matching may be used to investigate 3D ground form error distribution. It is confirmed that the form-truing error compensation can directly improve the 3D ground form accuracy. It may decrease the 3D ground form error by about 20% when the 2D form-truing error is reduced by about 58% using the same truing conditions for CNC grinding.     

Iso-parametric tool path generation from triangular meshes for free-form surface machining

The polyhedral model is widely used in the manufacturing industry. However, apart from the iso-planar method, the tool path generation methods for polyhedral machining are very limited. In such a case, the given tool paths are no longer boundary-conformed or efficient. This paper presents a new approach to iso-parametric tool path generation for triangular meshes. The strategy proposed herein first parameterizes the triangular faces via a harmonic map. The cutter-contact (CC) points and the path interval are then calculated based on the machining tolerance requirements and the iso-parametric tool paths are finally generated. The method is implemented on a computer and some illustrative examples are provided to show the effectiveness of the developed algorithm. The main advantage of the proposed method is that the tool paths can be generated naturally along the boundary of a polyhedral model, thus eliminating internal tight-radius corners in conventional paths. This leads to substantial reductions of tool wear and machining time. In addition, the proposed method can also be used in other non-iso-parametric tool path planning methods for triangular meshes and compound surfaces machining.