细分曲面粗加工刀轨生成算法

研究了细分曲面等高粗加工刀轨生成算法。以Catmull-clark细分曲面为研究目标,首先利用基于面误差的自适应细分算法构建粗加工模型,该方法构建的模型不仅具有均匀的加工余量,且能完全包围精加工模型,;然后采用层切法生成切层轮廓,在计算切削区域边界轮廓时采用了有效边追踪算法,该算法可以有效快速正确的得到每层的加工区域;为了验证算法的可行性及有效性,最后给出了加工实例,实例表明该方法可以有效地控制加工模型的网格数量,并能快速地生成粗加工刀轨。     

基于三角Bézier曲面平刀环切粗加工刀轨生成算法

为实现基于三角Bézier曲面造型技术的产品逆向设计与制造,提出一种针对三角Bézier曲面模型的平头刀环切粗加工刀轨生成算法,该算法通过优化R＊树的构建过程,建立了三角Bézier曲面模型的动态索引,基于该索引快速获取瞬时加工区域三角Bézier曲面片,进而采用刀具表面离散的方法迭代计算无干涉刀位点,并建立了三角Bézier曲面的Z向包络面,采用R＊树组织Z向包络面的拓扑近邻关系。将切削平面与Z向包络面求交获取截面轮廓环,并由它们之间的包含关系确定切削区域,进而获取环切粗加工刀轨。通过实例证明了该算法可对复杂三角Bézier曲面生成平刀无干涉环切粗加工刀轨。     

5轴叶轮粗加工过切与碰撞综合检测修正研究

针对复杂多曲面叶轮的5轴粗加工刀轨自动生成问题,提出一种基于使用平头立铣刀的无过切,干涉的刀具轨迹生成算法。通过对整体叶轮5轴加工中可能出现刀具与叶片干涉的问题,提出了一种干涉检测方法。依据检测结果对干涉进行处理,从而避免实际加工时干涉的发生。方法考虑了刀具运动路径上全部刀位点与叶轮的位置关系,计算量小,对于叶轮数控加工编程中大量刀位数据的干涉检查,可以显著地节省计算机运算时间。     

基于散乱测量数据点的三轴数控粗加工刀位轨迹生成算法

提出了一种直接利用三维散乱测量数据点的三轴数控粗加工刀位轨迹生成算法。首先根据切层深度作一组垂直于Z轴的平面,去截取测量点云,得到一系列切层截面点集,再在每个切层面上组环并判断加工区域,规划出刀位轨迹,将每一分层平面上的刀位轨迹按适当的方式连接起来,就可构成零件的整体加工轨迹。该算法避免了由测量点构造曲面且由曲面来进行刀位轨迹生成的这一复杂过程。     

三角Bézier曲面数控精加工刀轨快速生成算法

为了解决三角Bézier曲面精加工刀轨生成效率低以及存在的刀轨干涉等问题,提出一种基于三角Bézier曲面的数控精加工刀轨快速生成算法,该算法引入动态索引组织三角Bézier面片的拓扑近邻关系,基于该索引快速获取与刀轨截平面相交的三角Bézier面片集,对其中任一相交面片进行初始交点迭代计算,从初始交点开始跟踪迭代获取跨越三角Bézier面片的完整交线,将获得的有序交线各端点作为刀触点获取相应刀位点,依据刀触点处曲面法矢与刀杆矢量的关系快速确定可能存在干涉的区域,进而对干涉区域刀位点进行调整获取无干涉刀位点,顺次连接各刀位点生成数控加工刀轨,实例证明该算法可对任意复杂三角Bézier曲面精确、快速生成数控加工刀轨,并通过三角Bézier曲面模型的数控刀轨生成验证了该算法的实用性。     

基于MMR的三角网格曲面五轴加工刀轨生成算法

为了提高三角网格曲面五轴加工的加工效率,提出了基于最大材料去除率(maximal materialremoval rate,MMR)的平底刀五轴加工刀轨生成算法。首先计算无曲率干涉且具有最大材料去除率的网格曲面五轴加工的刀具方位角;然后在确定网格曲面可能干涉区域的基础上,提出刀触点处干涉性假设,并以最大材料去除率、刀具无曲率干涉和全局干涉为约束条件,采用二分法确定具有最大材料去除率的无干涉刀具方位角;最后采用截面线法生成三角网格曲面MMR平底刀五轴加工刀轨。通过实验验证了采用文中算法生成的刀轨进行加工能够获得较高的加工效率和表面质量。     

非典型叶轮数控5轴技术的研究

由于非典型叶轮结构复杂,无法使用主流CAD/CAM软件提供的叶轮5轴模块,在粗加工阶段采用3轴定向加工时,残余毛坯留量体积大形状不规则,严重影响了5轴加工的效率和质量。为此,一方面对于叶轮开式区域采用双圆柱面投影法获得驱动曲面,从而实现4轴联动粗加工,切削刚性大效率高;对于非开式区域则通过构建驱动曲面获得5轴联动刀轨,刀轨连续且刀轴矢量无突变。另一方面,提出了一种基于NC程序的刀轴矢量评价方法,可快速直观地评价5轴编程质量。实际使用结果表明:基于驱动曲面的刀轴矢量优化法能够显著提高复杂工件5轴加工的效率和质量。     

飞机结构件组合曲面侧铣加工刀轨生成方法

针对目前五轴侧铣刀轨生成方法生成组合曲面侧铣加工刀轨困难的问题,通过分析飞机结构件中组合曲面的类型,提出了一种基于曲面拟合的精度可控、刀轴摆动均匀且无干涉的飞机结构件组合曲面侧铣加工刀轨生成方法.该方法通过迭代拟合使曲面拟合精度可控,通过角度扇形离散控制刀轴摆角,通过局部微调以减少干涉.经实例验证,该方法精度可控、效率高、刀轨生成算法稳定、加工质量高.基于该方法开发的系统已在某大型航空企业得到应用.     

基于机床运动学约束球头刀多轴加工刀轴矢量优化方法

针对目前航空发动机叶片进排气边加工精度和表面质量较差的问题,提出了一种基于机床运动学约束球头刀多轴加工刀轴矢量优化方法。建立刀位优化变量与刀位数据之间的关系方程,同时建立刀位数据与机床回转轴角度之间的运动变换方程,从而推导出刀位优化变量与机床回转轴角度之间的关系方程。通过求解上述方程得到球头刀多轴加工复杂曲面的刀轴矢量计算公式。在此基础上,给出球头刀多轴加工刀轴矢量优化方法和刀轨生成方法。同时,以某航空发动机叶片为例,分析了本文算法和Sturz算法对机床回转轴角度的影响。分别利用本文算法和Sturz算法生成该叶片进气边加工的刀轨,并在五轴数控机床上进行加工试验。试验结果表明,该算法能够避免加工过程中机床回转轴的大幅波动,使机床轴运动更加平稳和光滑,从而提高曲面的加工质量和加工效率,具有一定的实际应用价值。     

运用点涉法原理确定平头立铣刀三轴联动数控加工轨迹

针对现有的空间自由曲面数控编程系统和ＣＡＤ／ＣＡＭ软件只能生成球面刀三轴联动数控加工轨进的局限性，以及实际切削加工中较少采用球面刀，多用小直径平头立铣刀等非球面刀来替代球面刀在三轴联动数控机床上完成空间自由曲面的切削加工这一现状，本文根据点涉法原理推导出在空间自由曲面上生成平头立铣刀三轴联动数控加工轨迹的算法。只要给出被加工曲面的参数表达式，就可以利用该算法在被加工曲面上确定平头立铣刀的三轴联动数控加工轨迹。     

基于插铣加工的非等参数刀具轨迹生成方法

针对复杂多曲面通道的多坐标数控粗加工,提出了一种新的刀具轨迹生成算法.该算法以传统的插铣加工方法为基础,提出适合于复杂多曲面通道的新插铣方法;利用曲面参数线,使用B样务曲线正算反算方法,在流道划分的多个截面上做由初始孔到截面轮廓的渐变曲线;通过计算满足残留高度的走刀行距,在各个截面的渐变曲线上提取参数点并拟合出相应曲线,进而得到刀具接触点轨迹.     

复杂曲面环形刀五轴端铣加工的刀具轨迹规划方法

为了降低复杂曲面类零部件加工的刀具路径,减小刀具路径条数,提高加工效率,提出了一种新的复杂曲面环形刀五轴端铣加工刀具轨迹优化方法。在局部可铣性基础上对刀轴矢量角进行自适应优化,采用新型加工带宽计算方法——等残留高度算法,给出了等残留高度算法的刀具轨迹生成具体步骤。仿真结果表明:与传统等残留高速算法相比,刀具轨迹优化算法的刀具路径更短、条数更少,能够有效提高复杂曲面加工效率。     

An efficient five-axis machining method of centrifugal impeller based on regional milling

This paper presents an efficient five-axis machining method of centrifugal impeller based on regional milling. As the base of the machining method, geometry of the centrifugal impeller and blade surface is analyzed, and sub-machining regions are presented through the division of the double three-cubic d non-uniform rational B-spline (NURBS) surface. In rough milling, the cutter parameters, tool path interval, tool path curves, and the fixed tool axis vector are calculated by the novel algorithm based on regional milling; the biggest cutter and smaller tool path length are obtained. In finish milling, for the aerodynamic performance of the finished impeller, the tool path curves are modified and interlinked to make them uniform and orderly. A modified algorithm of the finish milling of the blade surface is proposed, and not only are the machining errors reduced; their reasonable distribution is also realized. Numerical simulation and a real test impeller are presented as the test of the proposed method.     

开式整体叶盘四坐标侧铣开槽粗加工轨迹规划

为了提高开式整体叶盘的粗加工稳定性，在粗加工阶段，提出采用将自由曲面蜕变为直纹面的方式简化开式整体叶盘通道开槽加工的难度，实现稳定切削。讨论了直纹面逼近自由曲面的算法，提出了一种新的刀轴矢量计算方法，并基于直纹面给出了开式整体叶片通道四坐标侧铣粗加工数控编程方法，规划出了无干涉的刀位轨迹。实例验证表明，采用该方法可快速有效地实现开式整体叶盘的开槽粗加工，并可提高开式整体叶盘加工中的稳定性。     

Optimization of rotations for six-axis machining

Five-axis machines with three translational and two rotation axes are becoming increasingly popular in serving the needs of the mass production industry due to their ability to handle geometrically complex workpieces using the rotational axes. Theoretically, the combination of the five axes offers a minimal number of the degrees of freedom required to transport the tool into a prescribed spatial position and establish a required orientation. However, the rotation axes lead to an inevitable nonlinearity of the tool tip trajectory and the so-called kinematics errors appearing due to the specific kinematics of the machine. Eventually, one arrives at an interesting question. Is it possible to compensate this error by introducing an additional rotation axis? In other words, ??does an additional rotation axis offer any optimization benefits in the sense of the above mentioned error??? In this paper, we answer this question positively by analyzing a hypothetical six-axis milling machine with two rotation axes on the table and one additional rotation axis on the tool. The sixth axis is build on the top of the existing five-axis machine MAHO600E by Deckel Gildemeister. We present an extension of an optimization algorithm developed earlier by the authors for five-axis machining based on an optimal angle sequencing (the shortest path optimization). The extension is a combination of the shortest path strategy and the use of the additional axis. The algorithm leads to an increase in the machining accuracy, in particular, for rough milling. Numerical experiments and cutting by a virtual six-axis machine built in Vericut 5.0 validates the results of the optimization. The proposed optimization procedure is capable of upgrading the existing five-axis G-codes to the case of six-axis machine.     

Research on tool path planning method of four-axis high-efficiency slot plunge milling for open blisk

The great mass of machining allowance for blisk is removed in the rough milling, so improving the rough machining efficiency for the blisk’s tunnel is the key of realizing high-efficiency machining of blisk. According to the structure characteristic of open blisk’s tunnel, a four-axis plunge slot rough milling with high-efficiency and low machining cost is advanced. First, the plunge slot process for blisk and the generation process of the ruled enveloping surface for the freeform surface of the blisk’s blade are put forward. Then, the generating method of the ruled enveloping surface for the blade’s freeform surface and the tool path generation method of four-axis plunge slot milling for blisk are studied. The rough milling region of open blisk’s tunnel is determined by generating the ruled enveloping surface of blade’s offset surface, and the algorithm of tool path for four-axis plunge milling is given. When using a ruled surface to approach a freeform surface, the problem of getting boundary is solved, and the error from the calculation of tool path is avoided by the algorithm. At last, the experiment shows that comparing to the traditional side slot milling, the cutting force of four-axis plunge milling can be reduced by 60% and even the rough machining efficiency can be increased to more than double.     

ENVELOPING THEORY BASED METHOD FOR THE DETERMINATION OF PATH INTERVAL AND TOOL PATH OPTIMIZATION FOR SURFACE MACHINING

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A novel machining of multi irregular surface using improved noncircular turning method

The backplane processing is an important part of the manufacture of electronic communication equipment; the current processing of backplane surface, especially the rough machining, is still using milling; and the production efficiency is quite low. This paper presents a new method to turn with a cylinder for the rough machining of multi backplane surfaces, which is based on a conventional horizontal lathe and uses the improved method of noncircular machining. The performance requirements of fast tool servo (FTS) device and control model for the machining of noncircular surface are analyzed firstly; the position following control strategy is used instead of traditional position interpolation, according to the multi backplane surfaces machining technology and control strategy; and a novel algorithm, which is combined UG (Unigraphics NX) software surface fitting with cubic spline curve fitting of multi backplanes’ space, is proposed for computer-aided manufacturing (CAM) software design. Finally, the proposed processing method and CAM model algorithm are proved to be effective through the simulation and actual verifications, the products meet the processing requirements and the processing time of each piece is reduced from 8 to 2 min, and they also greatly improve the production automation and achieve energy saving and emission reduction.     

Optimal CNC plunge cutter selection and tool path generation for multi-axis roughing free-form surface impeller channel

Plunge milling is the most effective way for rough machining of impeller parts, but previous research had not considered the optimization of plunge cutter selection and tool path. In this paper, a new method for optimizing the plunge cutter selection and tool path generation in multi-axis plunge milling of free-form surface impeller channel is proposed in order to improve the efficiency in rough machining. Firstly, in the case of fixing a rotation axis at a certain angle in five-axis machine, a mathematical representation is formulated for the geometric model of the cutter interfering the impeller, and an optimization model of the cutter size is established at a cutter contact point on the impeller channel surface, so the largest tool could be determined. Secondly, by analyzing the machine tool movement characteristics, the geometric constraint model of the plunge tool path which relative to the largest tool, step distance, and row space is established, and a tool orientation calculation method of impeller channel machining is given, and then, the plunge tool path and tool orientation could be obtained. Finally, the generated tool path and tool orientation are simulated and verified in practical processing. Simulation and experimental result shows that the rough machining efficiency of the impeller part is improved up to 40 % with this method.     

Tool path planning for NC milling of convex polygonal faces: Minimisation of non-cutting area

Face milling is one of the most important machining operations in industry for producing flat surfaces. Substantial research has been conducted in the field of optimisation of machining parameters for face milling, without considering the impact of tool path selection. Choosing an efficient tool path can reduce the tool travel time considerably.In this paper, the authors present a mathematical model that determines an efficient cutter path in staircase-type face milling on an n-sided convex polygon. The algorithm developed minimises the total non-cutting area. The areas of application of this algorithm are suggested and the scope for future research is discussed.