NC flame pipe cutting machine tool based on open architecture CNC system

Based on the analysis of the principle and flame movement of a pipe cutting machine tool, a retrofit NC flame pipe cutting machine tool (NFPCM) that can meet the demands of cutting various pipes is proposed. The paper deals with the design and implementation of an open architecture CNC system for the NFPCM, many of whose aspects are similar to milling machines; however, different from their machining processes and control strategies. The paper emphasizes on the NC system structure and the method for directly creating the NC file according to the cutting type and parameters. Further, the paper develops the program and sets up the open and module NC system.     

Implementation of online NURBS curve fitting process on CNC machines

The study aims to develop a method for implementing an online non-uniform rational B-spline (NURBS) curve fitting process on CNC machines for improving the quality and efficiency of machining. Conventional CAD/CAM/CNC systems usually induce some machining difficulties and limit the machining results in real applications. Therefore, some researchers have proposed various methods for improving the machining results. An online NURBS curve fitting process consists of the fetching and fitting stages for CNC machines is developed in this paper. The fetching stage fetches a block of NC code and generates motion commands for obtaining data points. The fitting stage executes the NURBS curve fitting method along with a given set of data points. Moreover, the optimal search method is designed for obtaining good results in the NURBS curve fitting process. Simulations and machining tests carried out on a vertical machining center show that the proposed approach reduces the machining time to about 23% while maintaining the machining quality for the sample test.     

数控线切割机床加工程序过滤转换器的研究

提出了加工程序过滤转换器的概念，论述了数控线切割机床加工程序过滤转换器的功能和使用目的，阐明了加工程序过滤转换器的具体实现方法，指出使用加工程序过滤转换器符合现代数控系统开放性的要求。     

基于NURBS理论的高速插补技术

高速加工是近年来发展起来的一种先进的金属切削加工技术，由于它大大提高了切削效率和加工质量，故又称之为“高性能加工”。但当用高速加工进行高精度的曲面加工时，由微段直线或圆弧构成的数控程序非常庞大，从而造成加工信息量大增，另外直线或圆弧也不能真实、完整地反映CAD／CAM系统所产生的复杂曲面模型，从而造成制造精度偏离设计要求。为了能够更好地解决高速切削的工艺问题，出现了基于NURBS理论的CNC插补控制器，这使得CNC系统具备了能自动进行NURBS格式定义的加工域生成的能力，NURBS插补技术也成为当今数控加工和CAD／CAM领域的一大研究热点。     

CIMT’97主要展品的技术特点综述

两年一度的中国国际机床展览会是国际机床界和我国机械制造业的一件盛事。第五届中国国际机床展览会(CIMT’97)又一次荟萃了国内、外各机床厂及相关配套件厂和工具厂的精华,既可看到一些名牌企业享有盛名的产品,也会发现一些脱颖而出的新秀企业所展示的精品。从展览会上我们能深刻地领会到机床工具行业的发展动向,也能生动地观察到琳琅满目的新产品和新结构。从中既反映了丰富多采的世界先进实用制造技术和最新制造技术,也展示了中国机床工具行业通过“三大战役”在增强开发能力和竞争实力方面所取得的可喜的巨大进步。     

A bisection method for the milling of NURBS mapping projection curves by CNC machines

The concept of non-uniform rational B-spline (NURBS) mapping projection curves (NURBS-MPCs) is proposed in this work. A NURBS-MPC is a projection curve on a NURBS surface of a NURBS curve. The bisection method is used to interpolate NURBS-MPCs. Using an assigned chord, the interpolation of a NURBS-MPC can be obtained easily, and the milling precision of the NURBS-MPC can be controlled effectively. Based on the NURBS theory, the bisection method, and the parametric programming method, an online NURBS software package (NURBS-SP) for FANUC 0i-MB/MC/MD CNC system and an offline NURBS toolbox (NURBS-T) for Matlab have been developed. Using an example of a planar NURBS curve, a NURBS-MPC is created on a NURBS surface. The simulation and milling of the NURBS-MPC show that the bisection method is feasible and effective. The online NURBS-SP endows the NURBS interpolation function for those CNC systems only equipped with linear interpolation (G01) and circular interpolation (G02/G03) and extends the interpolation functions and machining capability of low-middle level three-axis milling machines. The interactive application of the NURBS-T and NURBS-SP can accomplish the design, simulation, and milling for NURBS-MPCs. This feature makes them to have broad application prospects in CNC machining industry.     

基于STEP-NC的NURBS曲面插补技术的研究

为提高曲面的加工效率和精度,提出了一种基于STEP—NC的非均匀有理B样条曲面加工方法。基于STEP—NC的数控系统能够直接处理包括完整的非均匀有理B样条曲面几何信息和1力Ⅱ工工艺信息的STEP—NC程序。详细讨论了非均匀有理B样条曲面插补算法的实现,并通过仿真试验,验证了该方法的有效性。     

A scheme for an internet-based checking method of machine-tools with variant CNC architecture

This paper proposes an Internet-based checking technique for machine-tools with variant Computerized Numerical Controller (CNC). According to its architecture, CNC is classified into one of two types: Closed Architecture Controller (CAC), which is the conventional CNC, or Open Architecture Controller (OAC), which is a recently introduced PC-based controller. Since CAC has a closed architecture, it is dependent on CNC vender specification. Because of this, it has been very difficult for users to implement application programs in the CNC domain. Recently, the conventional CNC of machine-tools has been replaced by a PC-based open architecture CNC. However, now many conventional CAC machines are being operated together with OAC machines in inadequately equipped shop floors. For Internet-based checking for variant CNC machines with CAC and OAC, a suitable systematic environment is necessary. Through this research, for the global management of variant CNC machines both a CAC and an OAC in the manufacturing system, a suitable environment for Internet-based checking of variant CNC machines was designed, and the checking methods for CAC and OAC machines were compared. The results of this research may serve as a base model for global monitoring and remote control in an integrated manufacturing system with variant CNC machines. Checking points defined in this research are classified into two categories: structured point and operational point. The former includes the vibration of bearing, temperature of spindle unit, and other points of periodical management, while the latter includes oil checking, clamp locking/ unlocking, and machining on/off status.     

空间曲面电火花线切割CAD/CAM系统

为解决高速走丝电火花线切割机床加工空间曲面的难题,实现大锥度空间复杂曲面零件的加工,以空间曲面数学模型和数控模型为基础,开发了一种计算机辅助设计/计算机辅助制造(Computer aided design/computer aided manufacturing,CAD/CAM)系统.其硬件系统以研制的数控转摆摆工作台为核心装置,并与现有高速走丝电火花线切割机床结合,组成空间曲面线切割加工系统.其软件系统可以根据上下导线的参数方程进行分析计算,建立空间曲面的三维模型,自动生成NC加工代码,进行加工仿真和空间曲面零件的加工.利用本系统进行典型空间复杂曲面零件的加工试验,结果表明加工结果与仿真结果基本相似.此外,还分析数控模型以及回摆间隙角对加工误差的影响.这些工作为解决高速走丝电火花线切割加工空间曲面的难题打下基础.     

激光切割机自动检测及测量造型系统

给出了系统的功能描述、结构组成以及各主要模块的设计分析。针对由于国外技术封锁造成的激光切割机数据输出问题,提出了一个基于屏幕截取和数字识别技术的数据双向传递方案并给出了具体的实现方法。从而在同一台数控激光切割机(Prim a LW-1530)上实现了工件检测、测量造型和数控加工等功能。该方案可用于基于W indows的各类数控系统来拓展数控设备的使用范围。     

专用锥形活塞环数控车床的改造

文章首先对锥面活塞环的锥面加工进行了分析,提出了一种新型的锥形活塞环加工方法,确定了对原型数控车床的改造方案,同时将自行开发的SEMENC-103S开放式数控系统应用到该车床上,进行了实验切削。     

基于双现场总线的开放式数控系统结构研究

在分析Profibus和CAN两种现场总线的特点和开放式数控系统特征的基础上,提出基于双现场总线的开放式数控系统体系结构。研究和划分了数控系统组件,介绍开放式数控系统运动控制的实现。由于采用了双总线结构,能大大减少信息流的冲突,可提高系统的可靠性和传输效率,为高速、高精度数控加工提供了有效的途径。     

机床数控软件化结构体系

提出了一种新的机床数控软件化的体系结构及其相关技术 ,该结构体系将数控机床运动控制与工艺性能控制分离 ,分别由两个基于PC的控制器控制 ,其软件具有独立于硬件的性质 ,而且运动控制的软件是通用的。给出了该结构体系下通用的数控机床运动控制基本软件模块 ,工艺性能控制以一种玫瑰线铣削加工为例 ,表明在本技术支持下 ,机床数控具有独立于具体硬件的软件化结构体系。本技术将直接支持工艺性能完全不同的机械制造设备的开发 ,如可以用于铣床、车床等通用金属切削机床的数控化 ,也可以用于开发齿轮和复杂曲面加工的专用数控设备 ,还可支持机器人、铸造、锻压以及剪切设备机械运动的数字控制     

数控快走丝电火花线切割加工工艺方法研究

通过对数控快走丝电火花线切割加工中如何加工穿丝孔、装夹工件、编制程序、选择电参数、使用工作液、应用多次切割工艺方法以及诊断加工故障等工艺方法进行研究。形成了一套完整的工艺方法，效果良好。     

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.     

面向数控加工过程的可重配置虚拟加工方法

结合虚拟制造技术对数控加工仿真系统进行了研究,在分析虚拟制造中数控加工仿真技术的基础上,提出了一种可重配置的虚拟加工方法。这种方法通过建立虚拟的部件及部件关系树,根据所需机床的不同类型,来对数控机床的结构进行不同的配置;其中毛坯模型的建立采用的是voxel模型法。此外,运用C++和OpenGL作为开发工具,实现了对数控加工过程的虚拟仿真(即虚拟制造);同时实际应用表明,在虚拟的加工环境下,机床对数控程序的验证时间大大缩短。     

Non-redundant tool trajectory generation for surface finish machining based on geodesic curvature matching

The increasing complexity of surface has put forward higher demands for CNC machining trajectory generation. The constant scallop height method has the disadvantage of point redundancy during trajectory discretization. Therefore, a non-redundant tool trajectory generation method for surface finish machining is put forward. The cutting row spacing is determined by the geodesic curvature according to scallop height and the convexity or concavity of the local surfaces. The adjacent cutter contact (CC) points with constant scallop height are expressed point by point from the present CC point. The redundant points are removed by maximizing each cutting step length through making the chord error equal to the machining allowable error. The dual NURBS ruled surface is constructed to realize smooth transition of the tool trajectories and tool axis vector. The prototype system taking ACIS R13 and HOOPS V11.0 as modeling kernel has been developed to verify the proposed method. The experiment results proved that the proposed method can realize non-redundant tool trajectory considering tool interference during surface finish machining.     

基于STEP-NC的CNC系统中插补技术研究

STEP-NC是一个新的数控编程接口,基于STEP-NC的CNC系统是未来数控技术发展方向之一.在该系统中不但具有直线和圆弧插补功能,而且还具有样条曲线插补功能.开发了一个统一的 基于NURBS样条曲线插补的通用插补器,推导出一个简洁的NURBS几何数据预处理算法,详细论述了基于等弧长的插补技术和插补原理.最后,通过仿真和实例加工验证了上述算法的有效性和可靠性.     

五轴联动数控加工的刀具路径优化方法研究

为解决五轴联动加工复杂曲面过程中的刀具路径不连续问题,提出了五轴数控的刀具路径优化方法。通过五轴NC代码的坐标变换还原有效切削路径,对切削路径进行误差约束下的非均匀有理B样条(NURBS)曲线拟合。对旋转轴路径采用五次样条曲线进行插值,建立切削路径和旋转轴路径的参数映射关系,通过机床逆运动变换求解C2连续的平动轴路径。实验表明,经过该方法优化后,切削路径和各驱动轴运动路径具有良好的平滑性,显著提高了五轴加工曲面精度和表面质量。     

数控加工中刀具的选用

随着数控设备的逐年增加,数控加工逐渐成为零件加工的主要方式,为了提高数控设备的加工精度和效率,首先要合理的选用刀具和切削用量,现在数控加工多采用标准的机夹式刀具,由专业的厂家制造,对于操作者来说主要的任务是选择适合的刀具和切削参数,充分发挥刀具的效能.本文从实际应用的角度出发.详细介绍了数控刀具的种类、选用方法和切削用量的选用原则,对实际生产具有一定的指导意义.