Corner Transition Toolpath Generation Based on Velocity-Blending Algorithm for Glass Edge Grinding

Sharp corners usually are used on glass contours to meet the highly increasing demand for personalized products,but they result in a broken wheel center toolpath in edge grinding.To ensure that the whole wheel center toolpath is of G1 continuity and that the grinding depth is controllable at the corners,a transition toolpath generation method based on a velocity-blending algorithm is proposed.Taking the grinding depth into consideration,the sharp-corner grinding process is planned,and a velocity-blending algorithm is introduced.With the constraints,such as traverse displacement and grinding depth,the sharp-corner transition toolpath is generated with a three-phase motion arrangement and with confirmations of the acceleration/deceleration positions.A piece of glass with three sharp corners is ground on a three-axis numerical-control glass grinding equipment.The experimental results demonstrate that the proposed algorithm can protect the sharp corners from breakage efficiently and achieve satisfactory shape accuracy.This research proposed a toolpath generation method based on a velocity-blending algorithm for the manufacturing of personalized glass products,which generates the transition toolpath as needed around a sharp corner in real time.

Research on a toolpath generation method of NC milling based on space-filling curve

Tool path generated by space-filling curve always turns frequently causing trembling to machine,reducing toollife and affecting workpiece quality. Length and generation time of tool paths are both relatively long. In order to solve these problems,a toolpath generation method of NC milling based on space-filling curve is proposed. First,T-spline surface is regarded as the modeling surface,the grid,which is based on the limited scallop-height,can be got in the parameter space,and the influence value of grid node is determined. Second,a box is defined and planned,and the tool paths are got preliminarily,which is based on minimal spanning tree; Finally,based on an improved chamfering algorithm,the whole tool paths are got. A simulation system is developed for computer simulation,and an experiment is carried out to verify the method. The results of simulation and experiment show that the method is effective and feasible,and length and time of the tool paths are reduced.

A local toolpath smoothing method for a five-axis hybrid machining robot

Smooth transitions between two adjacent five-axis toolpaths can reduce feedrate fluctuation,improving machining quality and efficiency.Hybrid robots’flexibility to adjust the orientation is advantageous in five-axis machining,but their kinematic issues raise challenges for toolpath smoothing.This paper proposes a G3continuous toolpath smoothing method for a hybrid robot.B-splines in the machine coordinate system(MCS)are inserted at corners to synchronize five-axis transitions.The transition errors of the tool position and orientation paths are estimated with the golden section method.These approximation errors are constrained by adaptively modifying the B-splines,i.e.,adding anchor points and optimizing the control points.A bisection search method is proposed for these geometric modifications,guaranteeing the user-defined error tolerance limit.Compared to the method based on the workpiece coordinate system(WCS),the proposed framework generates a smoother trajectory under the same error tolerance limit.Simulations and experiments are provided to validate the effectiveness.

基于图像识别仿生木纹的三维打印路径规划方法

针对传统三维打印采用的诸如网格、三角等均匀同构介观结构填充存在结构效率低、与承载零件应力场不协调等问题,受自然生长的木纹可提高木材整体性能的启发,提出基于图像识别仿生木纹的三维打印路径规划方法,旨在借鉴木材的纤维排布以改善零件的机械性能。通过木材铣削分层,依次提取各层图像木纹并生成对应打印路径,并逐层打印出仿生木纹试件。拉伸试验结果表明:相比同质量的网格填充、三角填充、直线填充三种传统均匀同构填充试件,基于仿生木纹的非均匀异构打印试件最大拉伸载荷分别提高了115.03%、72.89%、64.39%,证明了基于仿生木纹的非均匀介观填充结构能够显著提高打印件拉伸强度。

Four-axis trochoidal toolpath planning for rough milling of aero-engine blisks

The Blade Integrated Disk(Blisk) is one of the key components in the aero-engine, it is generally manufactured by the multi-axis milling and almost 90% raw materials are removed. To avoid the full immersion of a cutter in the rough machining of a blisk channel, the trochoidal milling is a promising strategy since it can keep a small immersion angle in the rough milling process while maintaining the high machining efficiency. However, while toolpaths are being planned for the trochoidal milling process, the conventional methods are mainly for the planar machining area with fixed tool orientations, which cannot be used for complex channels where the multi-axis machining should be employed. To this end, this paper presents a four-axis trochoidal toolpath planning method with a ball-end cutter, and thus the blisk channel can be machined efficiently.For this to happen, the trochoidal paths are planned in the parametric domain and then mapped into the physical domain, with tool orientations controlled by the quaternion interpolation method to have smooth tool movement along the toolpaths. Both geometric simulation and physical milling experiments of the proposed method have convincingly demonstrated the validation of the proposed method.

Toolpath Interpolation and Smoothing for Computer Numerical Control Machining of Freeform Surfaces: A Review

Driven by the ever increasing demand in function integration,more and more next generation high value-added products,such as head-up displays,solar concentrators and intra-ocular-lens,etc.,are designed to possess freeform(i.e.,non-rotational symmetric)surfaces.The toolpath,composed of high density of short linear and circular segments,is generally used in computer numerical control(CNC)systems to machine those products.However,the discontinuity between toolpath segments leads to high-frequency fluctuation of feedrate and acceleration,which will decrease the machining efficiency and product surface finish.Driven by the ever-increasing need for high-speed high-precision machining of those products,many novel toolpath interpolation and smoothing approaches have been proposed in both academia and industry,aiming to alleviate the issues caused by the conventional toolpath representation and interpolation methods.This paper provides a comprehensive review of the state-of-the-art toolpath interpolation and smoothing approaches with systematic classifications.The advantages and disadvantages of these approaches are discussed.Possible future research directions are also offered.

自由曲面加工中的等参数螺旋轨迹生成方法

通过对刀具轨迹有效性的分析,将刀具轨迹规划分为曲面上曲线族的选择和有效合理排布方式的设计两个方面。以此为基础,针对数控加工中心的高速加工特性,提出一种等参数螺旋刀具轨迹生成方法。该方法以减少抬刀、路径转接为目的,并综合考虑刀具轨迹几何与运动力学性能。首先以等参数线型轨迹为基础,生成等参数环形轨迹,进而以对角曲线连接相邻路径,构造能够实现连续切削的等参数螺旋轨迹。仿真试验表明该方法,简单实用,而且避免了轮廓偏置中的干涉检测,特别适用于自由曲面的高速数控加工。

基于Voronoi图理论的自由边界型腔加工路径规划

Ｖｏｒｏｎｏｉ图是计算几何研究中的一个有力工具。给出了基于Ｖｏｒｏｎｏｉ图和单调区划分的型腔数控加工环切轨迹规划算法，并首次将其应用于边界为自由曲线的型腔，提高了Ｖｏｒｏｎｏｉ图在该领域的应用价值。

自由曲面叶片数控加工刀具轨迹规划方法

研究了自由曲面叶片数控加工刀具轨迹规划方法。解决了两个问题:(1)叶片曲面建模过程中的布尔操作破坏了曲面参数域,从而在叶尖处造成冗余刀轨,并在叶根处有可能形成干涉;(2)叶片前后缘处曲率半径的剧烈变化导致步长计算容易超差从而造成啃切现象。针对问题(1),本文提出一种新的参数映射方法,将裁剪后的曲面参数域重新映射到一个规范化的参数域上去,并在新的参数域上规划刀轨;针对问题(2),本文提出一种改进的弦截法来计算走刀步长。该方法收敛速度快,且避免了对复杂函数的求导,计算量小。同时本文采用搜索解空间,并修改变量替换方式来避免该方法收敛于错误的解。仿真实例表明,本文方法达到了预期效果,在提高了加工效率的情况下,避免了啃切现象的发生。

自由曲面三轴粗加工刀具轨迹的计算方法

在复杂自由曲面类零件的加工过程中，粗加工往往要占去大部分的时间。本文从提高加工稳定性及加工效率的角度出发，提出了一个复杂多曲面数控粗加工的算法，即采用分层切削法，通过平面／曲面求交技术和交线环的等距、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”规划每一切削层的刀具轨迹。最后给出了编程应用实例。

裁剪曲面加工中的等参数线轨迹连接方法

针对传统等参数线轨迹连接方法的不足,提出一种简单有效的等参数线轨迹Zigzag连接方法。在该方法中,刀触点被封装成带有输入输出端口的形式,刀触点可以利用自身端口和其他刀触点的对应端口相连。为有效地组织离散的刀触点,该方法使用一种称之为轨迹线网的数据结构。为了获得轨迹线网,按连接特征点在环上的位置组建了双循环链表,以在双循环链表中查询到的信息确立轨迹线间的连接关系。在获得轨迹线网后,为了求取子轨迹,通过用户指定的端口利用轨迹线网来搜索可用路径;另外,为了简化子轨迹间的全局连接,采用一种简单的方法来替代传统的启发式算法。通过仿真试验,验证了有效性,并说明能处理带孔裁剪曲面的特点。

STEP-NC控制器及其刀轨规划方法研究

为实现产品模型数据交换标准—数控程序在传统数控机床上的应用,提出了产品模型数据交换标准—数控程序的刀轨规划方法。首先,概述了产品模型数据交换标准—数控程序控制器的类型及其3大核心功能模块,分析和研究了刀轨规划过程中坐标系转换问题,给出了利用产品模型数据交换标准—数控程序实体索引映射表规划加工特征刀轨的方法和步骤,着重分析了平面和型腔两个加工特征的加工策略,并基于上述方法给出了具体的规划方法流程图。最后,结合一个基于平面、孔和型腔3个加工特征的产品模型数据交换标准—数控程序实例,将所规划出的G代码程序在配备开放式数控系统HITCNC的3轴数控铣床上进行实际加工,实验结果证明,该刀轨规划方法是正确可行的,并具有一定的通用性。

平头锥状刀五轴数控联动刀位轨迹的自动生成

基于点涉法原理和平头推状刀的特点、，推导出了在凸曲面上平头锥状刀五轴数控联动刀位轨迹的计算方法，依据该计算方法和规划好的刀具路径，可以自动生成平头银状刀五轴数控联动的刀位轨迹。

DSX5-70型虚拟轴机床五轴联动控制

分析了最新研制的DSX5 70型三杆五自由度虚拟轴机床的机构组成及自由度 ,推导了其运动学逆解计算公式 ,作为实现运动控制和设计分析的基础·结合所使用的零件造型及数控编程系统 ,给出了实现五轴联动控制的处理方法·并以空间曲线为例 ,进行了五轴联动轨迹规划和切削试验·结果表明 ,运动学计算结果正确 ,五轴联动控制实时性好 。

基于点阵投影的粗加工新方法

提出了一种点阵投影式的粗加工方法。该方法对模具或机械产品的造型没有特殊要求，既可以是规则的实体模型，也可以是自由曲面模型。而且，允许曲面之间有缝隙或相互重叠；毛坯可以是任意形状。该方法计算模型简单，铣削过程中抬刀很少，加工效率高。能自动识别轮廓和岛屿，通过对轮廊和岛屿的合理布局，可方便地实现刀具轨迹的优化和粗加工钻孔点的自动生成。

深凹曲面五轴数控加工自动编程研究

介绍了某深凹曲面零件的五轴数控编程过程及相关知识,将待加工面设为驱动几何体,将投影矢量设为刀轴方向,同时将刀轴相对于ZM轴侧倾-20°,生成的刀路轨迹工作效率高,充分发挥了刀具的切削速度,同时避免了干涉。经试制,达到尺寸要求并获得较高精度的表面质量,达到设计和精度要求。因此,对于深凹曲面类零件的加工,采用该工艺和加工策略是高效的。

一种利用点搜索的多曲面体清根轨迹生成方法

针对复杂多曲面体清根加工刀位轨迹的生成问题,提出了一种基于点搜索的清根轨迹生成方法。在采用单刀清根时,球头刀刀心点到多曲面体所在的自由曲面以及多曲面体表面的距离相等,只要搜索到刀心轨迹上的所有点,即可生成单刀清根轨迹。据此,文章将多曲面体作为研究对象,通过将多曲面体以及搜索的基本初始点映射在曲面的参数域内,确定参数域内的所有搜索初始点及相应的搜索方向,沿搜索方向在参数域内搜索清根加工的切触点,并在物理空间判断相应的刀心点是否满足距离条件,满足的点即为搜索的目标点,所有目标点形成清根加工的刀心轨迹线,根据该曲线即可生成单刀清根的到位数据。在此基础上,通过生成不同尺寸刀具的单刀清根轨迹线,计算多刀加工的切触点,生成了多刀清根加工的到位数据。最后,结合航空发动机叶片阻尼台的加工,生成了其单刀清根轨迹和多刀清根轨迹并进行了切削加工实验。算例与实验结果表明文中方法加工结果符合加工精度要求,加工表面质量较好,说明了点搜索方法在多曲面体清根轨迹生成中的有效性和实用性。

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。

基于Cimatron E的螺旋桨加工技术研究

通过CimatronE7.1软件对螺旋桨轮进行数控编程加工技术的研究,解决五轴复杂曲面在数控编程中的路径规划和工艺问题,并通过正确设置Cimatron后置处理生成NC加工程序。

面向特征的整体叶轮五轴数控加工技术

基于特征制定整体叶轮数控加工工艺,同时兼顾叶轮的工作要求和加工刚度,利用UGNX3.0提供的Interpolate方式规划流道特征的开粗加工和精加工轨迹,Swarf方式规划叶片特征的侧铣加工轨迹。经过仿真验证加工轨迹的合理性,最后使用配有HNC-22M数控系统的五轴加工中心VMC-1100成功加工了整体叶轮。