CAD与CMM的集成应用

介绍了利用网络，在企业新产品开发中建立快速的信息传递方法，实现产品设计、加工、检测过程CAD与坐标测量CMM领域编程测量和信息的快速传递，提高产品开发效率。     

CAD/CAM/CNC/CMM在数控技术实训教学中应用

CAD/CAM/CNC/CMM一体化技术是现代制造工程技术人员必备技能之一,阐述了高等工科院校开展一体化实训项目教学的必要性,构建了完整的教学体系,明确了项目教学目的,并以连杆模型零件的制造过程为例,叙述了一体化项目教学的具体内容和实施步骤。     

Precision inspection system for aircraft parts having very thin features based on CAD/CAI integration

In this paper, a precision inspection technique using CAD/CAI integration is proposed for parts having very thin and sharply curved features. The technique begins with feature reconstruction of turbine blades which have combined geometry, such as splines, and thin small radius circles. The alignment procedures consists of two phases — rough and fine phases: the rough phase alignment is based on the conventional 6 points probing on the clear cut surfaces, and the fine phase alignment is based on the initial measurement of the curved parts using the least-squares technique based on iterative measurement feedback. For the analysis of profile tolerance of parts, the actual measured points are obtained by finding the closest points on the CAD geometry by the subdivision technique developed. The Tschebyscheff norm is applied iteratively, giving an accurate profile tolerance. The inspection technique developed is applied to practical blade manufacturing, and has demonstrated good performance.Nomenclature r _i (u),r _j (u) 3D vector curve representing theith,jth curve segment for spline - u, parameters in [0, 1] representing curve - P _i ,P _i+1 ith, (i+1)th control points on the spline curve along the airfoil direction - Q _j ,Q _j+1 jth, (j+1)th control points on the spline curve along the vertical direction - W _i ratio of chord length to the previous chord length on the spline curve - C(Cx, Cy) centre coordinate of the edge circle - _o, initial angle and range angle of the edge circle - N _jp ,N normal vector on the surface patch formed byP _i ,P _i+1,Q _j ,Q _j+1 control points - A ₁ toA ₆ 6 probing points for the rough phase alignment - A ₁ toA₆ contact points at the clear cut surface corresponding to theA ₁ toA ₆ - X(a _x,b _x,c _x),Y(a _y,b _y,c _y),Z(a _z,b _z,c _z) base vectors for CAD coordinate system with respect to the CCM coordinate system - O (O _x,O _y,O _z) origin of the workpiece in the CMM coordinate system - D measurement target points of the workpiece - r probe radius - M coordinate measurement target points in the CMM coordinate system - DM direction vector of the measurement target points in the CMM coordinate system - T ₁ transformation matrix of 4×4 for the rough phase alignment - T ₂ transformation matrix of 4×4 for the fine phase alignment - MM, MM _i measured data of the measurement target points - Lp Tschebyscheff norm of powerP     

基于CMM测量的自由曲面反求技术研究

重点介绍三坐标测量自由曲面的反求技术。通过对自由曲面数字化过程中数据获取、测量数据处理和曲面重构的研究,得到鼠标外壳的三维模型,极大地提高了设计质量和效率。     

A re-configurable cross-sectional imaging system for reverse engineering based on a CNC milling machine

This paper presents a novel reverse engineering digitizing system for full part geometry, which is based on a cross-sectional imaging device built in a NC milling machine. The system successively captures a picture for each planar cross-section contour of the part by end-milling and CCD imaging, and builds the geometry for both external and internal surfaces of the complex 3D part based on a set of the vectored cross-sectional contours. The system mainly consists of three components: a NC milling machine, a cross-sectional imaging device and a computer control unit. Some issues involving the principle and process flow of the system, encasing materials, cross-sectional imaging and NC code generation, etc. are described in detail. Built on an existing NC milling machine, a portable device for capturing the cross-sectional images is designed, which includes an isolated light source, a digital camera, a protective case, a rigid arm and a robust tripod. The device, connected to a computer control unit, serves as a highly flexible accessory for the NC milling machine, constructing the cross-sectional imaging system for reverse engineering. Furthermore, the error analysis and accuracy assessment of the system are also addressed. A typical case is discussed in detail to illustrate the applications of the system. Such a re-configurable digitizing system for reverse engineering offers a number of advantages, such as the functional extension of an existing NC milling machine, low costs, and rapid construction. As a result, this system provides a feasible and useful scheme for many enterprises to construct their own reverse measuring system based on existing equipment to aid in rapid product development and extend the function of existing equipment.     

凸轮机构逆向CAD模型的构建

这里通过对模切机（包装机械）中常用的动力机构一平行分度凸轮机构的分析,给出了这类凸轮机构的逆向设计的一种方法。     

Integration of inspection planning system and CMM via DMIS

INSPEX is a computer-aided knowledge based inspection planning system for preparing inspection plans from CAD toleranced component models of rotational components. To achieve the complete automation of the inspection process, INSPEX has been integrated with CMMs (computer controlled coordinate measuring machines) via DMIS (Dimensional Measuring Interface Specification), where DMIS has been as a data exchange standard. The inspection procedures produced by INSPEX can be automatically converted into DMIS data format file by the DMIS pre-processor described in this paper, which can be fed into any CMMs with a DMIS interface for executing the inspection procedures.     

基于逆向工程技术的布绒玩具CAD系统

我国是玩具制造出口大国,布绒玩具是传统的主导产品之一,但产品创新设计开发能力不强,本文针对这一状况,将逆向工程、三维CAD等先进技术引入布绒玩具设计,开发了一套包括三维模型构思、三维CAD建模、三维曲面（布片）展开在内的全功能布绒玩具CAD系统,从根本上更新布绒玩具的设计手段,缩短产品开发周期,提高设计质量.     

Integrated laser/CMM system for the dimensional inspection of objects made of soft material

The applications of the coordinate measuring machines (CMMs) with a contact trigger probe to the dimensional inspection of manufactured products are restricted to the parts made of hard material, such as steel. By combining the laser and CMM, the applications of the CMMs can be extended to the inspection of objects made of soft materials, such as foils, plastics, wood, wax and clay materials. In this research, replacing the contact probe with an inexpensive laser sensor is attempted so as to eliminate the possible deflection of the component being measured when using contact probe. By combining a laser sensor with the existing automated inspection environment, a CAD-directed, three-dimensional coordinate sampling system which can perform non-contact dimensional inspection is developed.     

Integrated precision inspection system for manufacturing of moulds having CAD defined features

An integrated precision inspection system has been developed for manufacturing moulds having CAD defined features. The techniques of precision measurement are implemented for CAD/CAI integration for moulds having sculptured surfaces with some basic features, such as, holes, slots and bosses. Features to be inspected are chosen in the CAD environment, and inspection planning is performed for each feature. The sampling-point strategies are: uniform distribution, curvature dependent distribution, or hybrid distribution of the two depending on the complexity of the sculptured surface. Line and plane features are divided into subintervals, and the measurement points are distributed at random positions in the subinterval. Prime number subintervals are considered for a circle feature, in order to avoid possible periodic distortion of the measurement features. The measurement path planning is performed considering collision avoidance and coordinate matching between the coordinates. The output of the planning is the machine code for a specific CMM having CNC capability. The machine code is downloaded to a specific CMM, and the measurement results are fed back to the computer. A new algorithm, called MINIMAXSURF, is developed to evaluate the form error precisely for sculptured surfaces. The algorithm considers the radius of the touch probe and evaluates the profile tolerance successfully by removing the unavoidable setup errors. The developed measurement system has been applied to real moulds, demonstrating high performance and accuracy.     

An integrated intelligent process planning system for prismatic parts using PC-based CAD and CAM software packages

Traditional machining process planning relies heavily on human decision making and manual calculations. The utilisation of CAM software and computers to aid machining reduces errors and planning time. A fully integrated planning system using CAD and CAM software would further increase the efficiency of process planning. The goal of this research is the automation of machining process planning for prismatic parts by integrating Autocad and Mastercam software packages using the Autolisp programming language and artificial intelligence techniques. Using only a 3D representation of the prismatic part geometry drawn in Autocad as input, the integrated system will be capable of producing NC code for the machining of the part with minimal human intervention. This system would greatly enhance the productivity of machining process planning.     

典型逆向工程CAD建模系统的比较

点云处理、特征提取与曲面建模、逆向曲面质量评价及对下游工程的影响分析是逆向CAD模型重构中的几个关键环节。目前典型的商用逆向CAD建模系统可以分为专用逆向软件和提供逆向处理模块的正向软件两类，两者在模型重构上有着各自的特点。以这两类软件的典型代表lmageware和Pro／Scantools为对象，针对逆向CAD模型重构的关键环节，对两者的特点进行了较详尽的比较和评述，并在此基础上进行了总结。     

A CAD/CAM system for the machining of precision cams using a half angle search algorithm

This paper describes a computer-aided design and manufacturing system for design and production of complex cam profiles within the specified tolerance using a half angle search algorithm developed for optimisation of CNC part programming of cam profiles. The algorithm provides a systematic searching method to determine the minimum number of NC points required for machining the specified profiles of plate cams within a user-specified tolerance. Based on this algorithm, the CAD/CAM system generates an accurate and economical CNC part program for cams. This is verified by experimental results, analysis from CAD system and comparison with results from other methods.     

基于专家CAD平台的坐标测量机实例库技术与面向MC的产品设计

基于专家CAD平台的坐标测量机实例库技术以设计单元实例类为核心,用设计单元的分级层次结构组织实例库。实例类以设计单元为载体,是设计单元的抽象,提供了设计单元的属性及检索、修改等方面的信息。该设计单元实例库以商用CAD系统与专家系统集成构成的专家CAD系统作为平台。在该系统的GUI下,设计人员的经验和启发式思维方式直接面向专家系统,通过实例检索和约束设计进行设计单元实例的修改,方便快捷地完成定制产品的设计。该系统在一定程度上实现了坐标测量机面向大规模定制制造的设计理念。     

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.     

面向对象技术在工程数据库开发和应用

着重阐述了面向对象技术在工程数据库开发中的地位和重要作用,提出了一种基于通用图形系统的ＣＡＤ建模方法,并详细讨论了其与工程数据库连接和实现方法。这里所提出的数据库的建模和具体实现技术具有较好的普适性,便于推广使用。     

平面连杆机构的计算机辅助设计

所介绍的自行开发的平面连杆机构计算机辅助设计系统，能对常用的平面连杆机构进行运动分析及综合。阐述了该系统的结构，系统设计的原则、设计目标以及有关的建模与求解方法，最后给出一个应用实例。     

轻型汽车液压制动系统CAD

介绍汽车液压制动系统CAD的总体构造、主要功能模块和运行机制,建立了汽车液压制动系统设计分解模型,最后阐述该软件系统在某轿车液压制动系统国产化过程中的运用实例.     

塔设备CAD参数化绘图系统研究与开发

介绍了塔设备CAD参数化绘图系统的设计思想,构建了系统的结构及相关模型,设计了实现系统的方法,并对其中涉及的关键技术进行了深入探讨。