五轴侧铣加工空间刀具半径补偿算法的研究

根据五轴数控侧铣加工主要依靠刀轴矢量姿态变化来完成的特点,对侧铣加工中的刀具半径补偿问题进行研究,提出了一种补偿方法.该方法应用在工件坐标系下,与具体的机床类型无关,充分考虑刀轴矢量可变的各种加工情形.算法包括一个加工块内的半径补偿、拐角类型的判别公式、内拐角和外拐角处的过渡处理方法.文中对补偿方法进行了误差理论分析,并结合加工实例在matlab中进行了仿真实验,实验结果显示补偿算法能够满足系统加工的精度要求.     

刀尖圆弧半径对主偏角影响的分析与实验研究

刀尖圆弧半径对加工精度、切削力等切削参数有重要影响,而主偏角直接影响切 削变形和切削力的变化。为了研究车刀刀尖圆弧半径对主偏角的影响,建立了刀具要素间的几 何关系。根据切削深度和刀尖圆弧半径大小,将切削条件划分为 4 种：①刀尖圆弧半径小于切 削深度,且主偏角为 90°;②刀尖圆弧半径小于切削深度,且主偏角小于 90°;③刀尖圆弧半径 小于切削深度,且主偏角大于 90°;④刀尖圆弧半径大于切削深度。根据刀尖圆弧半径和切削 深度之间的几何关系,分别计算了 4 种切削条件下刀尖圆弧半径导致的实际主偏角的变化。为 了验证分析结果,进行了切削实验,通过分析背向力和进给力的夹角计算实验主偏角。实验结 果证明,刀尖圆弧半径导致主偏角变小。     

OPEN MIND发布hyperMILL~2013

正近日,OPEN MIND Technologies AG发布了hyperMILL2013:此次新版本中包括了诸多改进和扩展功能,能够进一步提高现代NC机床和切削刀具的使用效率。同时,该软件还进一步缩短编程时间,延长了刀具寿命。hyperMILL2013的一大亮点是它对5轴轮廓偏置精加工的扩展:现在可使用圆桶刀。该策略使用圆桶刀的最大有效半径,采用一个点铣削接触方式。铣削刀具的半径     

基于压缩Voxel模型的五坐标数控加工仿真新方法

文章介绍了一种基于压缩Voxel模型的五坐标数控加工仿真新方法。该方法采用压缩Voxel模型表示数控加工工件模型和刀具空间扫描体模型,计算机内部存贮空间小,布尔操作简单、速度快。通过MarchingCubes方法提取数控加工仿真工件表面三角网格模型并进行图形显,提高了仿真工件显示质量。文章同时提出了一种基于压缩Voxel模型的刀具空间扫描体构造新方法,通过构造基本几何体球体、圆柱体、圆环体、锥形体和鼓形体的空间扫描体,完成各种加工刀具棒刀、球头刀、环形刀、锥形刀和鼓形刀空间扫描体压缩Voxel模型。该方法在《基于压缩Voxel模型的五坐标数控加工仿真系统》中得到了应用,仿真结果三维信息完备,操作人员可从任意方向观察、验证仿真结果,克服了现有五坐标数控加工仿真方法和商品化软件系统的不足,该方法是虚拟数控加工的关键技术。     

基于几何特性的槽加工刀具选取算法

刀具选取是复杂零件数控加工编程的一项重要内容,为实现数控加工程序编制过程中自动选取加工刀具,提高数控加工及其编程效率和质量,结合飞机整体壁板数控加工编程及其粗加工特点,提出基于几何特性的槽加工刀具自动选取算法.在分析刀具与可切削区域间关系的基础上,对Voronoi Mountain定义域进行修正,建立切削轮廓45°拔模体;并给出刀具的可切削面积、残留不可切削面积,以及小刀具半径计算方法;最后根据整体加工时间最短的原则确定最优加工刀具.该算法已在"飞机壁板快速数控加工编程系统"项目中得以应用,结果证明了其是可行、有效的.     

螺旋锥齿轮数控切削仿真系统研究

针对目前螺旋锥齿轮切削仿真系统独立性差、仿真速度慢、精度低、很难实现实时仿真等问题, 提出了刀具和轮坯进行布尔运算的一种新方法,即将螺旋锥齿轮加工区域层片分割后与刀具切削面求交的方法,在此基础上研究了切削过程的可视化及其实现,并基于虚拟现实技术开发出了螺旋锥齿轮数控加工仿真系统,介绍了该仿真系统的整体结构、各个模块的作用以及实现的流程。仿真实例验证了核心算法和仿真系统的正确性和有效性。     

矢量法刀具半径补偿研究

传统刀具补偿方法的计算过程复杂繁琐,计算量相对较大.提出一种新的矢量法刀具半径补偿,通过分析加工线段转接点处切线矢量夹角在平面坐标系中的分布情况,判断出不同的转接类型,并在此基础上进行刀具半径补偿计算,得出各个转接点坐标.仿真实验结果表明,该方法简单实用,较传统方法计算量显著减少,尤其是对转接点的计算,矢量法的引入使得该方法较三角函数方法具有更大的优势.     

基于DEXEL和离散点阵法的数控加工仿真研究

本文提出了基于DEXEL模型实现数控铣削过程中毛坯体的实时建模方法,减少了内存存储空间,支持观察视角的变化和仿真结果的缩放;根据三轴数控铣床加工的特点,将刀具扫描体看成离散刀位点之间的单个扫描体的组合,采用离散点阵法对刀具扫描体建模.使用局部搜索算法,用其搜索发生切削关系的点并动态更新仿真工件的高度值.在VC++ 6....     

平底刀底面加工叶片进排气边

平底刀加工叶片进排气边的传统方法以刀具侧刃切削工件,由于叶片进排气边处曲 面沿着截型线切线方向曲率半径较小,当走刀方向沿着截型线切向时,加工带宽较小。对影响凸 曲面加工带宽的因素进行研究发现,使用平底刀底面进行切削可以提高叶片进排气边处加工带 宽,由此提出了用平底刀底面加工进排气边的刀具定位方法,通过优化两个刀具定位参数使加工 带宽达到最大。以某航空发动机叶片进排气边为例进行仿真加工,结果表明该方法可有效增大叶 片进排气边处的加工带宽。     

数控车削加工中刀尖圆弧半径补偿有关问题

如果数控系统不具备刀具半径自动补偿功能,则只能按刀心轨迹进行编程,但当刀具磨损、重磨或换新刀而使刀具直径变化时,必须重新计算刀心轨迹,并修改程序;当数控系统具备刀具半径补偿功能时,数控程序只需按工件轮廓编写,加工时数控系统会自动计算刀心轨迹,使刀具偏离工件轮廓一个半径值,即进行刀具半径补偿.本文讲述的是车刀刀尖半径补偿问题,文章从刀尖半径的影响进行分析,根据不同功能的数控系统进行刀尖半径补偿方法等进行讨论,有较强的实用性.     

Real‐time cutting simulation of meshless deformable object using dynamic bounding volume hierarchy

This paper proposes a novel method for a real‐time cutting simulation of deformable objects using meshless method. The method utilizes a rapid refinement of topological relations among the simulation nodes of meshless deformable objects. Topological relations are defined as an undirected graph based on a visibility criterion. The graph connects the adjacent nodes that lie within a support of each node. The topological relations are refined by removing the edges of the graph that is intersected by the cut surface during the cutting simulation. Our approach utilizes a bounding volume hierarchy (BVH) to accelerate the computation of the intersection test. The BVH reconstruction algorithm is proposed to account for the cases where pieces of the object are completely cut out from the object. Algorithms to examine the connectivity among simulation nodes and accordingly reconstructing the BVH using two‐level BVH are presented. The proposed approach achieves real‐time cutting simulation of deformable objects through the rapid refinement of the topological relation. In addition, the computational performance of the cutting procedure is preserved during the entire simulation, thanks to the real‐time reconstruction of the BVH. Copyright © 2012 John Wiley & Sons, Ltd.     

一种基于双目视觉的奥制齿轮刀具参数测量方法

将双目视觉技术应用于奥利康齿制螺旋锥齿轮铣刀盘刀具的参数测量,通过双目标定获得系统的内外参数,并对待测刀具图像进行双目极线校正;提取待测刀具图像边缘轮廓并采用最小二乘法对直线边缘进行拟合,将共面直线交点作为匹配特征点,依据理想平行双目视觉系统三维重建方法求出刀具特征点的三维空间点坐标;利用空间点和空间平面的位置关系求取奥制齿轮刀具参数,通过实验对算法进行验证,实验结果证明了该测量方法的有效性,并具有一定的实际应用价值。     

刚体在软体对象环境中的碰撞检测的研究

刚体在软体对象环境中的碰撞检测在虚拟现实的研究领域具有很大的普遍性 ,但以往的研究较少 .文中给出了一种基于固定方向凸包 (FDH)包围盒树的碰撞检测方法 ,并着重论述了利用线性规划的思想以解决刚体自由运动后包围盒树的更新以及通过一种自底向上的方法解决软体对象变形后包围盒树的更新 .实验表明 ,该方法不仅能较好地解决刚体间的碰撞检测 ,而且能有效地解决刚体与软体间的碰撞检测     

Variational sphere set approximation for solid objects

We approximate a solid object represented as a triangle mesh by a bounding set of spheres having minimal summed volume outside the object. We show how outside volume for a single sphere can be computed using a simple integration over the object’s triangles. We then minimize the total outside volume over all spheres in the set using a variant of iterative Lloyd clustering that splits the mesh points into sets and bounds each with an outside volume-minimizing sphere. The resulting sphere sets are tighter than those of previous methods. In experiments comparing against a state-of-the-art alternative (adaptive medial axis), our method often requires half as many spheres, or fewer, to obtain the same error, under a variety of error metrics including total outside volume, shadowing fidelity, and proximity measurement.     

数控仿真技术的回顾与评述

本文在对当前国内外数控切削加工几何仿真和切削过程力学仿真的两个并行发展的研究领域的研究现状和成果的分析评述的基础上，指出了仿真的发展趋势，并提出一种几何仿真和力学仿真相结合的更精确的试切模型。     

Investigation of cutting parameter effects on surface roughness in lathe boring operation by use of a full factorial design

The main objective of this study is to investigate cutting parameter effects of surface roughness in a lathe dry boring operation. A full factorial design was used to evaluate the effect of six (6) independent variables (cutting speed, feed rate, depth of cut, tool nose radius, tool length and type of boring bar) and their corresponding two-level interactions. In this experiment, the dependant variable was the resulting fast cut surface roughness (R,). In order to perform all possible variable combinations, a total of 216 cuts were.

The results revealed that using short tool length always provide good surface roughness and that only slight improvement on surface roughness can be achieved by properly controlling the cutting parameters and/or the type of boring bar used. The results also revealed that using a long tool length may results in vibration that could be efficiently controlled by the use of a damped boring bar. With such a long tool length, the cutting variables become important factors to control in order to significantly improve surface roughness results with both types of boring bars. A prediction model is proposed for each types of boring bar. Both models are highly significant, p<0.00001, with coefficients of determination of 0.56 and 0.57 for a standard boring bar and a damped boring bar, respectively.     

Effect of tool vibrations on surface roughness during lathe dry turning process

Choice of optimized cutting parameters is very important to control the required surface quality. In fact, the difference between the real and theoretical surface roughness can be attributed to the influence of physical and dynamic phenomena such as: built-up edge, friction of cut surface against tool point and vibrations. The focus of this study is the collection and analysis of surface roughness and tool vibration data generated by lathe dry turning of mild carbon steel samples at different levels of speed, feed, depth of cut, tool nose radius, tool length and work piece length. A full factorial experimental design (288 experiments ) that allows to consider the three-level interactions between the independant variables has been conducted. Vibration analysis has revealed that the dynamic force, related to the chip-thickness variation acting on the tool, is related to the amplitude of tool vibration at resonance and to the variation of the tool's natural frequency while cutting. The analogy of the effect of cutting parameters between tool dynamic forces and surface roughness is also investigated. The results show that second order interactions between cutting speed and tool nose radius, along with third-order interaction between feed rate, cutting speed and depth of cut are the factors with the greatest influence on surface roughness and tool dynamic forces in this type of operation and parameter levels studied. The analysis of variance revealed that the best surface roughness condition is achieved at a low feed rate (less than 0.35 mnt/rev), a large tool nose radius (1.59 mm) and a high cutting speed (265 m/min and above). The results also show that the depth of cut has not a significant effect on surface roughness, except when operating within the built-up edge range. It is shown that a correlation between surface roughness and tool dynamic force exist only when operating in the built-up edge range. In these cases, built-u edge formation deteriorates surface roughness and increases dynamic forces acting on the tool. The effect of built-up edge formation on surface roughness can be minimized by increasing depth of cut and increasing tool vibration. Key words:design of experiments, lathe dry turning operation, full factorial design, surface roughness, measurements, cutting parameters, tool vibrations.     

Complete swept volume generation, Part I: Swept volume of a piecewise C-continuous cutter at five-axis milling via Gauss map

In this paper, we present a methodology to generate swept volume of prevailing cutting tools undergoing multi-axis motion and it is proved to be robust and amenable for practical purposes with the help of a series of tests. The exact and complete SV, which is closed from the tool bottom to the top of the shaft, is generated by stitching up envelope profiles calculated by Gauss map.The novel approach finds the swept volume boundary for five-axis milling by extending the basic idea behind Gauss map. It takes piecewise C¹-continuous tool shape into account. At first, the tool shape is transformed from Euclidean space into Tool map (T-Map) on the unit sphere and the velocity vector of a cutter is transformed into Contact map (C-Map) using Gauss map. Then, closed intersection curve is found between T-Map and C-Map on the Gaussian sphere. At last, the inverse Gauss map is exploited to get envelope profile in Euclidean space from the closed curve in the range. To demonstrate its validity, a cutting simulation kernel for five-axis machining has been implemented and applied to mold and die machining.     

一种曲线路径剪裁中刀具形变及其误差分析

动态移动切削阻力载荷对高速数控裁床加工过程中刀具形变及其剪裁误差具有的重要影响,提出了一种适用多层布料/皮革曲线剪裁路径的刀具形变及其误差计算方法;建立了动态负载条件下可伸缩刀具的挠度与转角方程,进而推导出高频振动裁刀剪裁误差及其随切削深度变化规律;计算结果表明,数控布料/皮革剪裁刀的动态载荷、高频振动参数、切削深度对剪裁误差具有重要影响,深入剖析高层数控裁床的加工机理,动态参数数据分析,对于提高机床加工效率,降低加工误差,提高刀具使用寿命具有一定的工程应用价值。