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;...     

自由曲面行距自适应五轴数控加工刀轨生成方法

在满足残留高度的前提下,增大行距能够有效减少加工刀轨的行数,从而减少刀轨总长度。针对自由曲面平底刀五轴加工,提出了一种行距自适应的刀轨生成方法。在刀具进给方向法平面上,以椭圆等效表示平底刀切削轮廓,基于曲面局部轮廓线和等残留高度点的几何特征提出迭代计算等残留高度点的方法;再根据等残留高度点、切削轮廓和曲面之间的几何关系,通过迭代调整下一行切削轮廓位置计算出满足残留高度要求的下一行刀轨信息;最后以下一行和当前行刀触点之间最小的参数差值作为自适应行距值规划刀轨。以叶片曲面为例生成刀轨,验证了算法的可行性和有效性。     

数控车削对刀高度对加工精度的影响

数控车削加工中,对刀高度误差不但对零件的尺寸精度有影响,对零件的形状精度也有影响。通过计算分析,得出对刀高度误差越大,对零件尺寸影响越大。在高度误差一定时,零件的尺寸越接近于对刀尺寸,其对零件的尺寸影响越小,提出了提高零件加工精度的具体措施。     

浅谈离散点拟合曲线的数控加工

以缝合机凸轮槽数控加工为主线，介绍离散点拟舍曲线的数据处理方法与步骤，分析了影响加工精度的因素，最后介绍了成组数控编程思想及技巧。     

叶片等残留高度数控螺旋铣加工刀具轨迹的规划算法

根据叶片的曲面特征,提出了基于等残留高度的叶片五坐标数控螺旋铣加工方法,设计了刀具轨迹生成算法,在UG二次开发环境下编程实现.该方法满足相邻刀轨之间的等残留高度要求,无冗余刀轨.避免了刀轨间的抬刀,可实现连续的切削加工,在满足误差要求的前提下可显著提高加工的效率.     

基于水轮发电机叶片的复杂曲面数控加工刀轨生成算法比较研究与优化

以中小水轮发电机叶片加工为研究对象,通过对等参数线法、等距截面法和等残留高度法三种刀轨生成算法所生产叶片零件的加工过程进行研究,比较三种不同算法在复杂曲面加工中的异同及三种不同的加工方法对水轮机叶片加工质量及加工效率的影响,得出水轮机叶片三种加工方法各自最优使用范围及方法,为水轮机叶片实际生产加工过程提供了参考。     

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.     

曲面实时插补无干涉刀轨的生成方法

提出一种数控加工中曲面实时插补无干涉刀轨生成方法。该方法既能在加工中实时产生无干涉刀位轨迹 ,同时也能方便地确定因避免产生干涉而出现的切不足区域 ,以便该区域的后续加工。     

从测量的散乱数据点云直接生成数控刀具路径的研究

提出了一种直接从测量的散乱数据点云用球头刀对自由曲面进行三轴数控加工时生成刀具路径的方法。不同于现有散乱点云基于逆向工程的刀具路径生成方法,本法考虑并估计了曲面加工误差和粗糙度。将散乱数据点云向XY平面投影,以获得的投影边界为刀具路径的主方向,然后根据曲面所需的加工误差和残留高度要求划分该投影数据点云,得到一系列刀位网格单元。通过最小化每个刀位网格单元的加工误差以确定每个刀位网格的节点位置,加权平均相关联刀位网格节点来对齐相邻刀位网格单元的边缘。为了缩短加工时间,裁去刀位路径上多余的线段,最终生成高效合理的数控加工刀具路径。已用实测的数据点云验证了本法直接生成刀具路径的有效性。     

实体造型生成曲面的数控加工进退刀方法探讨

随着数控技术的发展,CAD/CAM软件的发展也越来越快,其发展不仅使工件的曲面造型越来越方便,而且从根本上改变了工件造型的方法,即利用实体造型方法。很多CAD或CAD/CAM软件如:Pro/E、UG、CAXA等都具有实体造型功能,都有可通用的接口进行数据转换,工件在某一软件中进行的实体造型,可以在其他CAD/CAM软件中读取,进行数控程序的生成。由于实体造型极大的方便性、灵活性、快捷性,因此得到了广泛的应用。然而,工件由实体造型方法生成的曲面,是已经修整好了的曲面(即“裁剪曲面”),没有多余的覆盖面(曲面边界外的延伸面)。在数控加工中往     

层切法模具粗加工中自适应刀轨规划方法

目前,模具粗加工方法是制约模具数控加工效率提高的重要因素,为此,深入探讨了基于层切法的零件模具数控粗加工方法,简述了层切法中计算机辅助设计3维模型分层方法,详细论述了截面上数控加工轨迹生成和规划方法。研究了目前层切法刀具轨迹生成算法的不足,提出了刀具环形轨迹的自适应规划方法。根据层面边界曲率在已有粗加工刀具中自动选择粗加工刀具规格,实现了刀具优化选择的目的。应用该方法可以减少粗加工余量,提高粗加工速度,进一步提高零件模具数控加工效率。     

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.     

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.     

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     

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.     

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.     

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.     

Generating efficient tool paths from point cloud data via machining area segmentation

This paper presents a method of generating efficient three-axis ball-end milling tool paths directly from point cloud data. The primary objective is to achieve high efficiency in the machining of free-form surface geometry having isolated complex machining area. The high machining efficiency is attained by segmenting the entire machining domain into distinct areas according to the geometric complexity of the data points and by using cutters of different sizes for the segmented machining areas. An iterative numerical procedure is derived to determine the critical complexity that separates the data points with higher complexity (the complex points) from those with lower complexity (the non-complex points). A larger and more efficient ball-end mill is used to machine the area defined by the non-complex points. The gouging condition of all the data points is then evaluated with respect to the given ball-end mill. The isolated complex machining area is established by enclosing both the complex points and the gouge points. The smaller and gouge-free ball-end mill for the isolated complex machining area is subsequently selected from the standard commercial cutter series. Implementation of the presented method clearly demonstrates the high efficiency of the generated tool paths.     

Collision-free tool path generation using 2-dimensional C-space for 5-axis control machining

This study deals with the method of collision avoidance in the automatic tool path generation for 5-axis control machining. Five-axis NC machining offers the potential for efficient and accurate machining, but collisions between the tool and surrounding objects are still a severe problem. The method devised in this study avoids collision by producing the direction of collision avoidance, based on the 2-dimensional configuration space (C-space) defined by two parameters which determine the tool attitude. This method allows a test workpiece with overhanging parts to be milled without collisions. As a result, the validity of the method has been experimentally confirmed.