基于逆向工程的虚拟设计研究

基于逆向工程的再设计是现代设计的一种有效新方法，虚拟设计有必要采用反求技术来充实它的设计方法和专家库系统。文章首先对机电系统进行基于逆向工程的系统设计分析，找到系统反求虚拟设计的集成化模型结构，并建立了系统反求虚拟设计的各个模型。然后，对系统中零件的实体反求虚拟设计的体系结构、零件三维模型重构的关键技术进行了研究，从而完成基于逆向工程的虚拟设计。     

反求工程及其在Pro／E中的应用

介绍了反求工程的定义和方法，论述Pro/E软件系统在反求工程设计中的应用，重点讨论了模型的建立，曲面光顺、曲面连接等技术，并举例说明了反求工程的应用，为反求新技术项目的推广应用提供理论依据和设计方法。     

基于Imageware的汽车后大梁反求设计

以汽车后大梁为研究对象,介绍了反求设计关键技术以及使用Imageware进行自由曲面反求设计的方法。通过对点云数据的采集、数据预处理、特征线构建以及三维模型重建,介绍了利用Imageware实现汽车后大梁这种复杂曲面的反求设计的整个步骤,还介绍了反求设计的一般设计流程以及在Imageware中进行反求设计的技巧。     

谈谈零件工艺尺寸链计算中尺寸换算问题

谈谈零件工艺尺寸链计算中尺寸换算问题安徽农业大学方筱萍在零件工艺尺寸链中最常碰到的反计算问题就是尺寸换算──这是已知尺寸链封闭环尺寸公差。求某一组成环尺寸公差的反计算问题。在零件机械加工过程中，经常出现基准不重合的情况。如为了便于加工或测量，会出现原...     

基于反求技术的模具快速设计

反求技术作为模具开发的一种重要设计手段,越来越受到工程技术人员的重视。随着计算机技术、激光测量技术和数控技术的飞速发展,反求技术不再仅仅满足对已有产品进行简单复制,而是已发展成为船舶、汽车、航空和模具等工业领域重要的产品创新设计方法,是工程技术人员通过实物样件快速获取工程设计概念和设计模型的基本技术手段。反求技术能将实物样件或手工模型转化为CAD模型,并对CAD模型进一步优化和再设计,有力地促进了模具设计数字化与制造技术更紧密的结合,更好地为模具设计创新服务。     

快速电池检测机反求设计实例分析

反求设计可以在较短时间内设计出符合市场最新要求，性能优于原型的新产品，本文结合快速电池检测机的反求设计实例，阐述反求以获得良好机器性能而不是再现原型为最终目的。具体论述了快速电池检测机反求设计的步骤及其关键参数的选择。     

面向产反求的CAD／CAM一体化系统的研究

反求工程是一种新型生产力的象征，对提高企业产品开发能力和市场竞争力具有十分重要的意义。本文在对反求工程着急性技术进行分析和研究的基础上，提出了几种面向产品反求的ＣＡＤ／ＣＡＭ一体化方案，为实现产品的快速２设计、快速成型、快速制造提供了可行的框架。     

自由曲面反求技术及其CAD/CAM一体化实现

以某鞋楦底面的反求设计为例,应用反求技术建立自由曲面CAD模型,通过UG/Parasolid Binary数据格式与CAM软件进行对接,较好地实现了CAD技术与CAM技术的一体化。该设计技术考虑了产品的外形美观和制造的需求,并能提高设计效率,有效控制误差,是一种新产品开发的有效手段。     

数字化公差控制效果预测方法及其公差数学模型的建立

针对机床系统的数字化精度分析及其公差设计需求,提出了一种计算机辅助公差分析与设计方法。以定义面向系统的几何要素公差语义为基础,推导了几种基本几何表面的公差数学模型,模型包括几何表面在6个自由度上的约束,并表示为齐次坐标变换矩阵的形式以方便与机床系统误差模型的兼容。最后给出了公差控制效果预测方法的示例。     

复杂冲压零件数字模型的反求技术

提出一种利用激光光学扫描仪、三坐标测量机以及相应软件系统对具有复杂曲面冲压件进行数字化几何模型反求的技术路线，并对不同的软、硬件系统进行了比较，同时介绍了一个微型车发动机油底壳壳体反求的实例。     

Computer-aided operational dimensioning for process planning

One of the important steps of process planning is to determine the tolerance and mean size for each working dimension. This paper presents a computer-aided operational diminsioning systems which can determine tolerances systematically and calculate mean sizes of working dimensions automatically for a process plan. The system is based on the tolerance charting technique. Firstly, a tree theoretic representation for a tolerance chart is described in this paper. Three trees can be generated from blue print dimensions, stock removals and working dimensions of a tolerance chart. The algorithms for generating the trees are provided, and these trees can be used to identify dimensional chains and solid stock removals in a tolerance chart. Then a linear programming model is built to determine the tolerance of each working dimension. Finally, a mathematical model of linear equations for calculating mean working dimensions is formulated from the dimensional chains.     

基于Ontology的装配公差规范的自动生成

针对几何产品公差规范设计中存在的不确定性问题,文章将本体理论引入到装配公差规范的设计中,为装配公差规范的自动化、智能化设计提供一种可行的方法。首先构建装配公差规范层次化表示模型,并采用OWL DL断言表示模型层次间的约束关系;其次,根据装配公差规范中的概念和关系,构建装配公差规范的本体模型;再次,根据装配公差规范设计领域的专家知识,使用语义网规则语言(SWRL)构建装配公差规范设计的推理规则;然后,根据构建的本体表示模型及定义的推理规则,构建装配公差规范设计知识库,在此基础上编写装配公差规范智能化设计算法;最后,以齿轮减速器为实例说明了装配公差规范自动生成的过程,并分析验证了该方法的有效性。     

Study of an assembly tolerance allocation model based on Monte Carlo simulation

The traditional design methods of assembly tolerance allocation are usually based on engineers' experience, or the worst on worst tolerance analysis (WOW) method, or the root sum square tolerance analysis (RSS) method. However, the above-mentioned methods, whilst used frequently in the analysis of a single-dimensional chain, are not suitable for the analysis of geometrical tolerance and multi-dimensional chains. Also, the relationship between tolerance and manufacturing cost is not considered and a suitable tolerance allocation based on minimum manufacturing cost can not be obtained. Some research works have applied linear or non-linear programming methods to optimize the tolerance allocation of each part in an assembly. However, the convergence of the solution is not ensured. The purpose of this study is to provide an integrated approach, including tolerance design, manufacturing cost analysis and multiple chains consideration, using the Monte Carlo method to optimize the tolerance allocation with minimum cost. The Monte Carlo method, a statistical simulation method, was used to simulate the dimension variance of each part and each dimensional chain. The contribution percentage of each part on each dimensional chain was calculated. Tolerance cost was chosen as an object function and the tolerance allocation model as a constraint condition, the optimum tolerances of each part being obtained by the iteration method. Results of computer simulation for several examples were compared with published data for demonstrating the feasibility of the proposed method. It can be concluded that the tolerance-allocation model combined with a tolerance-cost relationship can provide a very practical and useful approach for design engineers.     

基于实际工况的装配体公差建模方法研究

几何产品的装配公差数学模型对CAD/CAM/CAE的集成有着重要的作用。目前的装配公差模型以刚体假设为前提,忽视了实际工况的影响。为解决此问题,研究了实际工况对产品工作性能及公差设计的影响,利用有限元仿真计算了零件在实际工况下的变形量,并在公差模型中综合考虑变形量的影响,建立了实际工况下装配体的公差模型。将该方法应用到尾座装配体的公差建模中,验证了该方法的有效性。     

基于小位移旋量公差建模和蒙特卡洛模拟的装配体公差优化设计方法北大核心

提出一种基于小位移旋量(SDT)公差建模和蒙特卡洛模拟的装配体公差优化设计方法,通过分析装配精度链、装配结合面和结合面公差3个对装配精度具有重要影响的核心要素之间的关系,利用SDT理论和蒙特卡洛模拟法建立公差模型,再利用齐次变换理论建立结合面误差模型和装配精度模型,进而推导出装配体装配精度与结合面公差相关的映射模型;结合公差制造成本、装配精度可靠度原则,建立装配体装配精度的公差优化模型,并以顶尖装配体为例完成公差优化分析。研究发现:在满足装配精度可靠度的前提下,可使顶尖装配体加工成本降低9.02%,而装配精度可靠度提高至97.81%,验证了所提方法的有效性。     

CAD/CAM自动编程中零件尺寸公差的保证

针对现有CAD模型的公差信息不能用来支持后续的CAM工作,为使CAD/CAM自动编制的NC程序能满足零件的尺寸公差要求,我们以Mastercam为例总结出了三种方法,即在CAD中以公差带中心建模、修改刀具补偿量、预留公差带中心偏移量等方法,这三种方法中各有其特点.     

机床夹具公差的灰色综合设计理论与方法

根据灰色聚类综合评价的原理和方法，对影响夹具公差选择的多种因素进行了数据处理，建立了夹具公差选择的灰色聚类综合评价模型，为定量确定夹具的公差提供了有效的方法。     

Incorporating tolerances of customers’ requirements for customized products

Tolerancing conventionally deals with the variation of manufacturing processes to meet the requirements of product quality. With the development in product customization, it has been generally accepted that customers’ requirements also have acceptable tolerance range. This flexibility provides an opportunity to better match customer requirements with richer product offerings through customization. A probabilistic model is presented in this paper to incorporate the tolerance of functional requirements into customized product design. By leveraging on the requirements tolerance, customers are more likely to get their desired products. Customer requirements tolerance can thus open up a new dimension for product customization.     

Quantitative circularity tolerance analysis and design for 2D precision assemblies

Circular, cylindrical, or spherical features are fundamental geometric features in engineering. As precision requirement becomes more stringent, it is not sufficient to consider only size tolerance of circular and cylindrical parts. However, currently there is no quantitative and systematic way of assigning circularity and cylindricity tolerances. This paper investigates how to specify circularity tolerance quantitatively for 2D assemblies. Statistical matrices to quantify positioning error of two perfectly circular mating parts subject to size tolerance for both clearance and transition fit conditions are first developed. The analysis is then extended to nonideal profiles whose profile errors are assumed to deviate from a best-fit circle according to a normal distribution. The assumption of the normal distribution is then removed for more general results via computer simulation. For this purpose, an experimentally verified profile model is used to generate realistic profiles as those produced by various machining processes. Numerous pairs of these realistic profiles are then assembled virtually using Monte Carlo simulation to quantify their positioning errors. The simulation results and the analytical results are compared for cross-checking. Finally, systematic design procedures are proposed to assign circularity tolerance by prescribing a fit condition with a desirable process capability. By the nature of circularity tolerance, this paper addresses a 2D assembly. The result of this 2D analysis can be a foundation for more complicated 3D problems, such as assigning cylindricity tolerance.