自由曲面数控加工刀具的研究

对自由曲面数控加工中的刀具进行了较深入的研究。从刀具有效半径和切削速度的角度,对平头立铣刀在五坐标自由曲面加工中的加工效率与切削性能进行了分析。提出了球头刀和平头刀的刀位计算方法,并对叶片曲面的刀具轨迹进行了仿真模拟。     

宏程序在数控加工中的应用

以日本FANUC18i—MA数控系统为例，介绍了用户宏程序在进行参数化加工和中断处理方面的功能和应用。     

曲面沿参数线加工的实时轨迹生成

提出了一种沿参数线加工的无干涉刀位轨迹实时的生成算法，据进给速度和ＣＮＣ插补周期确定轨迹逼近步长，简化了计算，减少了实时轨迹生成的计算量，采用双重干涉判别准则，成功地消除了干涉。     

双联圆柱凸轮的参数化设计与数控加工

根据双联圆柱凸轮特殊的运动要求,运用Pro/ENGINEER及MasterCAM软件进行参数化设计与数控加工,解决了一般编程方法难以解决的问题。     

NURBS曲面的参数化离散及其在数控加工干涉避免中的应用

复杂曲面加工中，如何快速、有效地筛选出特殊曲面点以进行刀具干涉判断是实现无干涉刀具路径生成的关键。通过推导有理Bezier曲面的参数离散算法并结合NURBS曲面可转化为有理Bezier曲面的性质，实现了NURBS曲面基于参数的离散。该离散结果保留了离散曲面点与曲面参数域的一一对应关系，通过切削点的参数信息可快速筛选出少量需进行干涉校验的离散曲面点，从而有效简化了刀具干涉检测计算。实例分析表明，该算法能在保证曲面离散精度的前提下提高无干涉刀具路径规划的效率。     

自由曲面数控加工动态仿真研究

在VC++6.0平台上采用OpenGL技术开发一种自由曲面数控加工过程仿真系统。该系统可根据自由曲面的不同造型,规划出适当的刀位轨迹,生成G代码;实现交互控制,完成设计曲面的成型加工,并动态显示加工路径。     

基于UG的装配加工技术及其应用

本文详细介绍了在UG中进行数控编程时采用的装配加工技术,通过将夹具定义成检查几何体,使得产生的刀位轨迹能够自动避让夹具,最后给出了一个装配加工实例。     

基于参数化编程的薄壁零件数控加工

针对薄壁框架类铸造零件数控加工易变形的问题,提出了“先定余量、再找基准”的方法,并利用数控设备的自动测量、赋值等功能,编制参数化数控程序,实现自动化加工.加工结果表明,该方法能有效解决薄壁零件数控加工中的装夹变形问题.     

圆柱凸轮的参数化设计及数控加工

通过圆柱凸轮的轮廓特征分析,运用AutoLisp语言,按等间隔直线逼近方式,参数化编程绘制圆柱凸累主轮廓展开图,将图形数据转换文件格式后送到MasterCAM中生成平面轮廓的NC代码,再将代码中的Y坐标参数为旋转轴参数,可加工出高精度的圆柱凸轮。     

自由曲面数控加工刀位轨迹生成方法的研究

依据逆向工程中自由曲面造型理论,结合数控编程中等距面法和参数线法,给出了一种较为简便的数控加工刀位轨迹生成方法。     

NURBS曲线、曲面造型过程的可视化设计

由于ＮＵＲＢＳ曲面、曲线构造的复杂性,描述ＮＵＲＢＳ曲线、曲面必然采用复杂的数据结构,这样给人—机交互带来很大的困难。本文利用ＶＣ＋＋编写的ＮＵＲＢＳ曲线、曲面造型系统可以实时观察曲线、曲面的控制点、节点信息,可以实时对控制点、节点进行诸如添加、修改、删除等操作,这对ＮＵＲＢＳ曲线曲面造型无疑会带来极大的方便。     

用于加工弧面凸轮轮廓曲面的NURBS插补方法

在分析弧面凸轮轮廓曲面上加工刀痕产生的原因,以及对分度机构性能影响的基础上,提出了用NURBS样条插补凸轮从动件运动规律曲线的思想方法.通过对NURBS样条插补改进算法的深入分析,得出了进一步校正满足加工步长条件的NURBS样条参数增量的算式.同时对插补前弧面凸轮从动件运动规律曲线的修正、NURBS插补误差和插补过程的实现进行了计算与分析.结果表明,采用文中给出的方法,能显著提高弧面凸轮轮廓面的加工精度.     

Simultaneous 3D machining with real-time NURBS interpolation

Increasing demand on precision machining using computerized numerical control (CNC) machines have necessitated that the tool move not only with the smallest possible position error but also with smoothly varying feedrates in 3-dimensional (3D) space. This paper presents the simultaneous 3D machining process investigated using a retrofitted PC-NC milling machine. To achieve the simultaneous 3-axis motions, a new precision interpolation algorithm for 3D Non-Uniform Rational B-Spline (NURBS) curve is proposed. With this accurate and efficient algorithm for the generation of complex 3D shapes, a real-time NURBS interpolator was developed using a PC and the simultaneous 3D machining was accomplished satisfactorily.     

汽车轮辋的NURBS曲面造型设计

讨论工业设计理论及其在汽车轮辋造型上的应用,讨论NURBS曲面的数学表达并用NURBS曲面造型对轮辋进行大圆弧过渡造型设计,从而获得了产品的三维模型及其效果,为产品的设计制造打下了坚实的基础。     

NURBS curve and surface fitting for reverse engineering

Reverse engineering is an approach for constructing a computer-aided design (CAD) model from a physical part through dimensional measurement and surface modelling. This paper presents alternatives for reverse engineering of free-form parts using Non-Uniform Rational B-Spline (NURBS) surfaces. A two-step linear approach is employed for fitting NURBS curves and surfaces using the measured points. During the first step, the weights of the control points are identified from a homogeneous system using symmetric eigenvalue decomposition. The control points are further processed in a way similar to B-spline curve and surface fitting. Some examples are presented to illustrate both the steps of reverse engineering and the process of NURBS curve and surface fitting.     

Design and implementation of a real-time NURBS surface interpolator

In recent years, various parametric curve interpolators have been proposed for high-speed and high-accuracy machining. However, these methods are based on a constant cutter location (CL) velocity. Hence, the cutter contact (CC) velocity along the surface tends to vary, resulting in a nonuniform machining performance. Furthermore, machining complex surfaces requires the provision of a large number of tool paths and therefore the associated NC data files are generally very large. To overcome these limitations, the current study presents a novel real-time NURBS surface interpolator which ensures a constant CC velocity along the CC paths and its intervals. A PC-based real-time motion control network utilizing SSCNET is developed to achieve the goal of multi-axis synchronous motion. In this study, both the NURBS surface interpolator algorithms and the SSCNET communication protocols are realized by Embedded XP with the RTX real-time kernel. The experimental results confirm that the proposed real-time NURBS surface interpolator is capable of achieving a satisfactory performance.     

NURBS曲线曲面重构的方法

CAD/CAM中用有理多项式函数表示曲面越来越广泛。由于非均匀有理B样条(NURBS)可以精确表示解析形状和自由曲线曲面,国际标准组织(ISO)与1991年把NURBS作为表示工业产品几何形状的工业标准。这里主要讨论了NURBS曲线曲面重构的方法。     

An improved feedrate scheduling method for NURBS interpolation in five-axis machining

Five-axis machining plays an important role in manufacturing by dint of its high efficiency and accuracy. While two rotation axes benefit the flexibility of machining, it also brings limitations and challenges. In order to further balance machining precision and efficiency, an improved feedrate scheduling method is presented considering geometric error and kinematic constraints for the Non Uniform Rational B-Spline (NURBS) interpolation in five-axis machining. A simplification method is proposed to calculate the geometric error which describes the deviation between the ideal tool path and the real tool path induced by the non-linear movement. A linear relation between geometric error and feedrate is built to limit the feedrate. The constraints determined by single axis kinematic performance and tangential kinematic performance are also considered. Under these constraints, a constrained feedrate profile is determined. Aiming to get more constant feedrate in the difficult-to-machine areas, this work proposes a scheduling method which combines morphological filtering and S-shape acceleration/deceleration (acc/dec) mode. Simulations and experiments are performed to compare the proposed feedrate scheduling method with two previous feedrate scheduling method and the results prove that the proposed feedrate scheduling method is reliable and effective.     

三次NURBS样条曲线插补加工螺旋转子建模与加工研究

提出在螺旋转子加工制造过程中,采用三次NURBS样条曲线插补替代通常的微直线段插补;建立了螺旋转子端面摆线段三次NURBS样条曲线方程.在Pro/E软件上比较了三次样条插补曲线和理论摆线之间的精度误差.最后通过在立式加工中心上比较了采用三次NURBS样条插补和采用微直线段插补的加工精度和加工效率,采用三次NURBS样条插补加工取得了理想的效果.     

CNC数控编程技术在雕刻加工中的巧妙应用

本文通过对圆弧曲面数控雕刻加工的实例表述,给出了圆弧曲面数控雕刻的编程加工应用步骤,在圆弧曲面数控雕刻加工中,针对于编程软件的特点和数控铣床的特点,采用了灵活实用编程方案和可靠有效的数控加工工艺,从而保证零件加工质量和加工效率,也使企业经济效益和生产水平得以提高。