基于Cimatron的复杂曲面数控加工研究

基于Cimatron软件CAD/CAM集成环境,通过对加工工艺的分析比较得出对平缓型曲面可以用“WCUT”进行粗、精加工,对凹凸型曲面先用“WCUT”进行粗加工,再用“SRFPKT”进行精加工,给出了一种加工效率高、成型质量好的数控加工方法。以实例对其进行分析,并给出了数控加工模拟效果图,证明该方法既可提高加工效率,又可获得较好的表面加工质量。     

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.     

支撑粱两端勾头的数控优化加工

随着数控加工技术的日益普及和不断发展,CAD/CAM软件的不断更新,加工各类曲面或复杂形面一直是多轴数控机床在编程及应用中的一项的关键技术。UG作为一款高端的CAD/CAM软件,在实际加工中有着广泛的应用。通过UGNX4.0的自动编程方式,在TK42200数控龙门铣镗床上加工"支撑梁"两端勾头的加工方案,该方案对其它复合形面的加工也有借鉴意义。     

A new free-form surface fitting method for precision coordinate metrology

Free-form surfaces are widely used in advanced optical and mechanical devices. In order to assess the form accuracy of free-form surfaces, it is needed to fit the measurement surface with the design template. To improve the fitting efficiency and accuracy, the fitting procedure is divided into two stages, rough fitting and final fitting. A new rough fitting method, called structured region signature is proposed. Structured region signature is a generalised global feature which represents the surface shape by a one-dimensional function. The template location occupying the best fitting signature is considered to be the correct initial position of the measurement surface. In the final fitting, the motion parameters are calculated iteratively using the Levenberg-Marquardt algorithm. Simulation and experiments are given to identify the validity of this method. It is demonstrated that the fitting accuracy is as high as 1:10⁶.     

复杂曲面天线的CAD/CAM一体化技术应用

随着CAD／CAM技术的快速发展，对于具有复杂曲面的产品，其设计制造方法也随之相应发生变化。本文介绍了借助大型CAD／CAM软件（Pro／ENGlNEER Wildfire版）和数控加工机床，在复杂曲面反射面天线制造中，运用曲线拟合、曲面构造、三维造型、数控编程、数控加工仿真，生产出高质量的产品。     

圆弧拟合在非圆轮廓曲线数控加工中的应用

利用数控系统所具有的宏变量编程功能,提出了一种非圆轮廓曲线圆弧拟合的加工方法。建立了圆弧拟合非圆轮廓曲线的数学模型,对加工精度进行了分析计算,设计了数控加工的程序编制流程,为数控技术人员加工非圆轮廓曲线提供了一条思路。     

NC machining of free-form Kriging surfaces

An algorithm for three-axis NC tool path generation on sculptured surfaces is introduced when the free-form surface is modeled parametrically by free-form surface Kriging. The flexibility of dual Kriging that easily defines the intersection of the surfaces with a set of parallel planes and Cartesian method are combined to generate the tool-paths automatically. The presented algorithm can simultaneously generate the tool path with a predefined machining accuracy and remove gougings along the tool path. The algorithms are validated by three experiments in rough and finish machining and the results prove its reliability. Since Kriging is based on the interpolation of data points, the proposed algorithm can be used for reverse engineering applications. The system was executed on a standard micro-computer and the software was structured to offer a library of machining functions for endusers.     

用宏程序在数控铣床上编制球面加工程序

数控铣床上加工曲面一般采用软件产生刀具路径、生成程序后自动加工,或采用宏程序手工编程加工。自动生成的加工程序通常字节多,占用很多机床存储空间。而宏程序短小精炼,适合存储空间小的设备,具有很强的适应性,只要改变一两个数据就可以进行粗加工。     

复杂曲面上投影曲线的误差可控插补算法

为保证曲面精加工质量的一致性,减轻后续处理工作量,提出了一种误差可控的复杂曲面上投影曲线的直接插补算法。在分析复杂曲面五轴联动数控加工所产生的非线性误差的基础上,在算法中引入误差控制方法,即采用参数对分法来减小非线性误差的影响。方法简单,实用,有利于提高曲面加工质量,可以很好地满足工程实际需求。最后通过实例仿真验证了算法的有效性。     

叶片复杂曲面的机器人抛磨工艺规划

为了实现复杂曲面工件的智能抛磨加工,对叶片复杂曲面进行机器人抛磨工艺规划。对抛磨点位置规划算法和基于最大接触原则的抛磨姿态规划算法进行了研究。首先,通过平行截面法获得抛磨路径割线,以非均匀有理B样条(NURBS)曲线描述。接着,提取曲线特征参数,根据设定的阈值进行抛磨点规划,再基于抛磨轮与工件的最大接触原则进行抛磨点姿态规划,从而得到完整的抛磨路径。然后,将工件位姿从工件坐标系转换到TCP坐标系。最后,搭建了柔性抛磨系统仿真平台生成机器人控制程序。实验结果表明,此方法规划的路径可用于叶片复杂曲面的机器人抛磨加工。分别用本文规划所得路径和CAM软件规划所得路径对叶片进行抛磨加工,测得表面粗糙度分别为0.695~0.930μm和2.803~3.243μm。本文提出的抛磨位姿规划方法可用于复杂曲面工件的抛磨路径规划,使工具和工件保持最大接触,从而避免了位姿不合理所产生的过抛和欠抛。     

Complexity analysis and calculation for sculptured surface in multi-axis CNC machining based on surface subdivision

Complexity of sculptured surfaces has a great influence on multi-axis computer numerical control (CNC) machining performances such as processing efficiency, surface quality, and energy consumption. A term called surface machining complexity (SMC) is first presented to describe the complexity level of surface geometrical shape features, and its influence on CNC machining performance. Shape features of sculptured surfaces are classified into seven categories based on surface curvature. An innovative method for quantifying SMC using surface subdivision is proposed. Firstly, representation of sculptured surfaces is introduced. Then, three processes of surface subdivision are presented, which are surface discretization based on iso-parameter line sampling, rough partitioning based on surface shape categories, and region grouping based on two criteria. After that calculation, formulas of SMC including formulas of local SMC and global SMC are developed. The proposed formulas utilize three correction factors to describe the influences of surface size, cutter diameter, grouping order, and mode of different surface shape categories. Finally, the proposed method is applied to calculate SMC for a typical sculptured surface and multi-axis CNC machining experiments to demonstrate the ability of our method, which can form a foundation for further research.     

A new accurate curvature matching and optimal tool based five-axis machining algorithm

Free-form surfaces are widely used in CAD systems to describe the part surface. Today, the most advanced machining of free from surfaces is done in five-axis machining using a flat end mill cutter. However, five-axis machining requires complex algorithms for gouging avoidance, collision detection and powerful computer-aided manufacturing (CAM) systems to support various operations. An accurate and efficient method is proposed for five-axis CNC machining of free-form surfaces. The proposed algorithm selects the best tool and plans the toolpath autonomously using curvature matching and integrated inverse kinematics of the machine tool. The new algorithm uses the real cutter contact toolpath generated by the inverse kinematics and not the linearized piecewise real cutter location toolpath.     

直纹面叶轮插铣加工关键技术

为提高整体叶轮的粗加工效率,弥补目前商用计算机辅助制造软件在五坐标插铣加工能力方面的不足,研究了直纹面叶轮五坐标插铣加工的关键技术。根据直纹面叶片的偏移边界矢量,利用四元数插值方法计算插铣加工的刀轴矢量,提出并推导了五坐标插铣加工的行距和步距计算公式,保证了插铣加工的材料去除率和加工效率。依据上述算法自主开发了整体叶轮五坐标插铣加工专用计算机辅助制造软件,并对该软件生成的刀具轨迹进行了仿真和实际加工验证。结果证明,该方法在一定程度上提高了叶轮零件的粗加工效率。     

Integrated rough machining methodology for centrifugal impeller manufacturing

In mechanical engineering, most products or components, especially those for aerospace applications, are designed to fit the requirements of free-form surface features. The impeller often required by 5-axis machine operations is a key component of the aerospace industry. When 3-axis CNC machining center is used to manufacture the impeller, great difficulties, i.e., collisions between the cutting tool and impeller, need to be overcome. Presently most commercial CAM systems for 5-axis control lack generality, and functions for the rough tool-path generation are far from sufficient. Although the rough machining is the most important procedure influencing the machining efficiency and the condition for the following finishing process, many difficulties arise in performing 5-axis rough machining. The main objective of the present study is to overcome this problem by integrating the state-of-art machining technology, and consequently effective rough tool-paths are to be generated. This study aims to implement the algorithm of the constant scallop height method to improve tool-path planning of rough machining. As a result CL data based on the geometry model of blade and hub are generated. The CL data are confirmed by comparing them with original CAD model through software simulations and later by machining experiments. The verification results show that the machining methodology and procedure adopted turn out to be a successful case.     

非圆齿轮齿面加工余量匀化工艺研究与实现

针对非圆齿轮加工中,由齿坯节曲线曲率变化所引起的分次进刀过程中齿面加工余量分布不均的问题,提出一种匀化非圆齿轮齿面加工余量的工艺方法。以非圆齿轮插削工艺为研究对象,基于插齿加工原理,对齿面加工余量分布不均的成因进行了分析;在此基础上建立了非圆齿轮匀化工艺插削联动模型,通过实时调整插刀与齿坯的几何位置关系,实现了非圆齿轮齿面加工余量的匀化;开发了非圆齿轮插齿CAM系统,利用CAM系统对齿面加工余量匀化工艺进行了仿真验证,仿真结果表明,所提工艺方法正确、可行;将匀化工艺集成到自主开发的齿轮加工数控系统中,进行了非圆齿轮插削加工试验,试验结果表明,所提工艺方法能够有效匀化齿面加工余量;对加工出的非圆齿轮齿面进行了三维形貌检测,检测结果表明,所提工艺方法能够显著提高非圆齿轮的加工精度与表面质量。     

A robust surface fitting and reconstruction algorithm for form characterization of ultra-precision freeform surfaces

Ultra-precision freeform surfaces are non-rotational symmetric surfaces possessing sub-micrometer form accuracy and nanometric surface finish. Although they can be fabricated accurately by ultra-precision machining technology, their surface quality is difficult to be characterized. Surface reconstruction is a vital task in the form characterization of ultra-precision freeform surfaces. This paper presents a robust surface fitting algorithm to reconstruct a high fidelity surface from measured discrete points while the surface smoothness can be ensured as well. A fitting threshold named confidence interval of fitting error is proposed to strike the balance between fitting accuracy and surface smoothness in the fitting process. The fitting algorithm is in two steps. In the first step, bidirectional sampling method is developed to extract a curve network from measured points cloud to construct an initial surface. In the second step, the fitting error of the initial surface is minimized to meet the prescribed fitting error threshold. A series of experimental work has been conducted and the results show that the proposed algorithm is able to provide effective means for increasing the accuracy in the form characterization of ultra-precision freeform surfaces.     

基于MasterCAM的印章加工方法研究

印章是常见的办公用品.利用MasterCAM软件对印章进行了加工设置,介绍了采用曲面加工对印章进行加工的方法,达到了提高加工效率,提升加工质量的目的.     

新型并联机床数控系统插补算法的研究

提出一种用于新型并联机床的粗、精插补策略和算法 ,粗插补采用直接对加工曲面进行插补的方法。以NURBS曲线为例 ,运用合理计算方法推导出粗插补计算公式 ,并对粗、精插补进行了误差分析。插补实例结果表明 ,该插补算法具有恒速进给、加工表面轮廓误差易于控制等特点     

基于UG逆向工程对涡轮的计算机辅助加工

为提高涡轮曲面数控加工的工件成型质量，基于UG／CAD／CAM软件集成环境，对逆向工程申重构出的涡轮曲面CAD模型进行数控加工编程的方法和原则进行了讨论，提出对涡轮的数控编程加工方法并在粗加工与精加工中获得较高的成型质量和加工效率。     

基于线锯高效切割的复杂直纹面模型建立及仿真

针对天然石材、人工晶体等材料复杂曲面加工中，初始毛坯与最终产品形状差别较大，粗加工材料去除量大，导致加工效率低、刀具磨耗严重的问题，提出了一种基于线锯加工和点加工协同去除的高效粗坯加工的解决思路。根据线锯加工特点，提出了对最终产品的数字化模型进行分层处理，利用多边形对各层二维外轮廓曲线进行包络，将层与层之间的多边形进行顺序拟合得到相应直纹面模型的建模思路。分析了不同包络多边形边数、连接方式所构建的不同直纹面模型对粗坯加工时间的影响。仿真结果表明，虽然增加多边形的边数或者通过层间旋转可以减小剩余未加工材料体积，但整体粗坯加工时间反而有所增加，从而不利于提高效率。粗坯加工时间可作为综合评价指标来优化构建直纹面模型。