面向CAD/CAPP集成的零件特征组合描述及其应用

在分析目前依靠单特征进行工艺推理不足的基础上 ,从工艺推理角度把组成零件的一些单特征按照加工要求重构 ,由此引出特征组合的概念 ;分析零件中可能出现的特征组合的类型并对其进行描述 ,指出从 CAD模型中提取和识别这些描述的可行方法 ,由此实现 CAD与 CAPP的集成 ;讨论特征组合对工艺推理的影响 ,这种从工艺角度描述特征的方法有利于提高工艺推理的精度 .最后以实例说明特征组合描述在 CAD/CAPP集成系统提高工艺推理准确性的应用     

面向CAD／CAPP集成的零件特征组合描术及其应用

在分析目前依靠单特征进行工艺推理不足的基础上，从工艺推理角度把组成零件的一些单特征按照加工要求重构，由此引出特征组合的概念，分析零件中可能出现的特征组合的类型并对其进行描述，指出CAD模型中提取和识别这些描述的可行方法，由此实现CAD与CAPP的集成；讨论特征组成对工艺推理的影响，这种从工艺角度描述特征的方法有利于提高工艺推理的精度，最后以实例说明特征组合描述在CAD／CAPP集成系统提出工艺推理准确性的应用。     

零件工序模型几何演变序列生成方法及应用

针对机加工艺知识挖掘与重用困难的问题,分析得出工艺知识隐藏在零件工序模型序列的几何变化之中,并进一步提出工序模型几何演变序列的生成和相似性度量方法以及特征匹配算法.首先对工序模型的几何变更进行提取和表示,并将整个工序模型序列中所有前、后道工序间的几何变更按照工艺过程的优先级约束组成了几何演变序列;然后建立零件工序模型几何演变序列的相似性度量算法,并以算法的计算结果作为衡量零件工艺相似性的依据;在几何演变序列中提取出参与特征形成过程的变更元素建立新的加工特征模型,并通过构建特征的匹配算法来为融入加工特征形成过程的更高维的特征识别与匹配提供依据.实例结果表明,文中方法是可行性的.     

关联工艺引导的型腔类零件局部结构检索方法

针对已有的基于内容的三维CAD模型检索技术难以保证检索结果关联工艺的可重用性,需要设计人员进一步甄别其重用价值的问题,提出一种关联工艺引导的型腔类零件局部结构检索方法,以从基于制造特征的结构化工艺数据中查找关联工艺可重用的相似三维几何.首先建立特征关联工艺参数化驱动模型,从特征加工几何、加工精度、刀具几何角度揭示特征实例关联工艺的参数化驱动特性;然后以特征实例关联工艺为参考,建立基于中轴转换的特征相似性评价模型;最后提出基于子图同构的相似局部结构提取算法,并且计算相匹配局部结构之间的相似度.在CATIA平台下开发了原型系统,并验证了文中方法的有效性.     

数据与知识驱动的零件特征工艺决策方法

在零件的工艺设计阶段, 加工工艺方案的生成强依赖于设计人员选择和应用的工艺知识. 而由于实际的生产环境与设计人员选择工艺知识存在着诸多偏差, 加工方案与实际的工艺过程不匹配成为当前零件制造领域关注的难题. 为解决上述问题, 本文提出了一种数据与知识双驱动的零件特征工艺决策方法. 本方法使用基于注意力机制的MLP深度学习算法, 从结构化工艺数据中挖掘工艺知识, 关联零件特征与特征工艺标签. 将其经过数据加工后, 用于训练神经网络模型. 经过验证, 该方法能够以零件特征的工艺数据为输入, 输出其对应的特征工艺标签的概率分布, 为零件工艺方案的选择提供决策支持.     

基于知识图谱的典型零件加工工艺知识构建方法

现代柴油机关键零部件生产工艺的总方案设计迫切需要对零件生产制造过程中的工艺知识进行有效组织,以实现工艺知识的共享和重用,因此,文章对柴油机典型零件的工艺知识以及知识之间存在的内在关联进行分析,引入知识图谱构建工艺知识模型,对知识图谱的关键技术进行研究,包括知识抽取、知识表示和知识融合等。通过工艺知识建模建立本体模型,对柴油机生产制造过程的相关工艺知识进行描述,明确柴油机典型零件加工工艺本体的概念,研究属性以及概念之间的关系。基于知识图谱对柴油机典型零件加工工艺知识进行重构,面向柴油机典型零部件加工过程,将柴油机典型零部件加工工艺知识转换成计算机可识别和处理的内容,完成面向柴油机典型零部件工艺知识图谱的建立。     

基于本体映射的零件工艺实例重用方法研究*

针对目前计算机辅助工艺设计中基于实例的工艺相似性重用问题,提出一种基于本体映射的零件工艺实例重用方法。在分析零件工艺实例信息的基础上,建立了新零件工艺知识本体和零件库零件工艺实例本体。基于本体映射的方法,通过本体间相似度计算,完成新零件工艺实例的检索和重用,并以轴类零件来说明该方法的有效性。     

机械加工MBD毛坯模型的特征识别设计方法

为了解决基于模型的定义(MBD)环境下机械加工毛坯辅助设计问题,采用特征识别技术辅助创建三维毛坯模型.首先分析了机械加工工艺设计环节MBD毛坯模型的组成要素与模型要求,并建立零件模型的属性面邻接图;根据零件模型上加工特征的特点划分简单特征、体积特征和表面特征;通过属性面邻接子图的模式从特征集合中识别出简单特征与体积特征,并利用补特征法与半空间法抑制这2种特征;最后,根据工艺员输入的表面加工余量创建抑制表面特征的实体.在整个毛坯设计推理过程中研究了三维制造标注的维护方法,最终达到辅助工艺员快速设计MBD毛坯模型的目的.     

基于传动箱体零件的CAD/CAPP系统设计

本文介绍了一种基于特征实例的CAD/CAPP系统.在特征库的支持下,用户可完成箱体零件特征造型,形成描述性文件,系统根据描述的特征信息与特征实例库进行匹配,以获得各特征加工链,再利用工艺决策模块进行排序优化,最终获得所需加工工艺.     

融合制造语义的三维工序模型序列重用方法

针对目前三维工序模型序列重用缺少对加工特征尺寸、加工精度、形位公差等制造信息的考虑,不能很好地支持零件制造过程工艺设计重用的问题,提出一种融合制造信息的三维工序模型序列重用方法.首先,利用图同构原理对工艺路线中三维工序模型序列进行优化,减少搜索空间;然后,利用子图同构对三维工序模型加工特征进行匹配,通过融合制造信息对加工特征匹配进行预处理和相似性评价,以获取具有最相似加工特征的三维工序模型;其次,设计三维工序模型序列优化算法获取同构的三维工序模型序列;最后,以某型轴零件工艺设计过程为例进行实例验证,结果表明融合制造信息的三维工序模型序列重用方法能够准确地根据指定制造特征进行工艺设计重用,具有良好的应用效果.     

Recognizing manufacturing features from a design-by-feature model

This paper presents a methodology for recognizing manufacturing features from a design feature model. The common feature-feature interacting relationships are categorized. A feature recognition processor first translates the design feature model of a part into an intermediate manufacturing feature tree by handling design features according to their properties and the interacting relationships between features. Through combination, decomposition, and (tool approach direction) TAD-led operations, alternative interpretations of manufacturing feature model for the part are then generated, and the manufacturing feature tree is updated and extended with AND/OR operators to store these interpretations. Finally, a single interpretation with the lowest machining cost will be selected in the manufacturing feature tree. The proposed processor can support a dynamic and effective recognition process of manufacturing features during the design stage of a part. By defining the interactions between volumetric features elaborately, and utilizing design features and auxiliary information, the processor can recognize manufacturing features from complex parts. The processor recognizes not only some essential manufacturing features but also replicate, compound and transition features defined in STEP. The alternative interpretations can be used for a generic manufacturing application environment.     

A database system of mechanical components based on geometric and topological similarity. Part I: representation

A database of mechanical components is an important issue for some manufacturing activities such as cost estimation, process planning, and design by case-based reasoning. In this paper, we give the representation scheme of the CAD model in such a database. Components are represented using attributed graphs in which the nodes correspond to the surfaces of the component and the links correspond to the edges of the component. The graph is based on the standard for the exchange of product information (STEP) physical file of the component. STEP file should be unique for a single component regardless of the underlying CAD system. The process of creating the graph of a component constitutes two sub-tasks: (i) importing the CAD model from the CAD system in STEP format and (ii) transforming the STEP data into attributed graph-based representation. The graph and its attributes describe the topology of the component completely together with some geometric data that are not dependent on any coordinate system such as surface type and curve type. These geometric data are helpful in the retrieval and matching processes in the database.     

虚拟企业下零件工艺信息建模研究

对于异地分布式虚拟企业来说，信息量需求增大，敏捷性增高，从而使得信息的共享和集成是要解决的难题之一。文中在分析虚拟企业以及已有建模技术的基础上，对工艺信息的获取进行了探索性研究，采取从CAD模型的STEP文件中获取和人工补充两种方式相结合来得到完整的信息；采用基于特征的建模技术建立了零件工艺信息概念模型，从而保证了信息一致性、完整性、永久性。     

基于STEP标准的统一BOM模型研究

在产品生命周期中,BOM贯穿了设计、工艺、制造、计划、采购、销售、财务等几乎所有职能部门,各部门按照本部门的需要定制了各种BOM。在BOM的定制过程中往往没有统一的设计和管理规范,无法保证各BOM之间数据的一致性,这种现象严重影响了企业产品设计、生产和管理等过程的集成和效率,增加了产品生产成本、延长了产品开发周期,所以研究基于STEP标准的统一BOM模型对制造业信息化的进程具有十分重要的意义。文中首先剖析了企业中存在的多视图BOM,阐述了BOM多视图的演变过程,在此基础上提出了统一BOM模型,并基于STEP标准构建了统一BOM模型。实践证明,文中提出的基于STEP标准的统一BOM模型可以较好地解决多视图BOM的模型不统一问题。     

Design of a STEP compliant system for turning operations

The changing economic climate has made global manufacturing a growing necessity over the last decade, forcing companies from East and West to collaborate beyond geographic boundaries in the design, manufacture and assembly of products. The ISO 10303 and ISO 14649 Standards (STEP and STEP-NC) have been developed to introduce interoperability into manufacturing enterprises so as to meet the challenges of responding to production on demand. This paper describes and illustrates a STEP compliant CAD/CAPP/CAM System for the manufacture of rotational parts on CNC turning centers. The information models to support the proposed system together with the data models defined in the ISO 14649 standard used to create the NC programs are also described. A structured view of a STEP compliant CAD/CAPP/CAM system framework supporting the next generation of intelligent CNC controllers for turn/mill component manufacture is provided. Finally a proposed computational environment for a STEP-NC compliant system for turning operations (SCSTO) is described. SCSTO is the experimental aspect of the research and is supported by information models that and have been constructed using a structured methodology and object-oriented methods. SCSTO was developed to generate a Part 21 file based on machining features to support the interactive generation of process plans utilizing feature extraction. A case study component has been developed to prove the concept of using the milling and turning parts of ISO 14649 to provide a turn-mill CAD/CAPP/CAM environment.     

STEP中性交换文件的实现方法

首先简要介绍了ＳＴＥＰ中性文件实施的过程和方法,以及二维工程图ＩＧＥＳ和ＳＴＥＰ实体的对应关系,然后介绍了二维工程图基本几何实体和文本注释、尺寸标注等非几何信息的ＥＸＰＲＥＳＳ描述,及其映射生成ＳＴＥＰ中性文件的方法,并给出一个实际工程图的ＳＴＥＰ中性文件（由自行研制的ＡＰ２０１应用工具的后处理器生成）,最后对ＳＴＥＰ中性文件的优缺点进行了评价。     

A STEP-BASED CAD/CAPP INTEGRATION

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Dimensional metrology interoperability and standardization in manufacturing systems

Dimensional metrology is an important part of any manufacturing system. It consists of distinct components and requires a large, diverse, and interconnected knowledge base. How to pass information seamlessly with minimal cost and minimal data loss between different components of a dimensional metrology system is a major issue that concerns software and hardware vendors, standards developers, and customers. This paper focuses on the four main elements of a dimensional metrology system: product definition, measurement process plan definition, measurement process execution, and analysis and reporting of quality data. The activities and software modules that are involved in these elements are discussed. Key issues that cause interoperability problems are identified. These issues are discussed as they relate to the current situation in dimensional metrology standards development. The STEP (ISO 10303) standards are the product of an international effort to achieve interoperability for manufacturing systems. Extending STEP is an appropriate way to solve the interoperability problem within dimensional metrology systems. Further development of STEP standards is proposed so that Geometric Dimensioning and Tolerancing (GD&T) information already available in STEP can be linked with manufacturing feature information, measurement technology, and measurement results. The proposed STEP data model is an attempt to provide a standard that will support automatic measurement process plan generation for in-process on-machine measurement. Some case studies are under way to test the model.     

面向集成的CAD系统

在ＣＩＭＳ中，集成是关键技术。设计者在不同环境中产生的数据需要相互交换和共享。该文主要介绍设计阶段产生的数据如何与ＣＡＰＰ／ＣＡＭ集成。开发特征造型系统，建立包含零件的几何信息和加工信息的信息模型，最后输出ＳＴＥＰ中性文件，达到ＣＡＤ／ＣＡＰＰ／ＣＡＭ集成。     

基于XML的STEP产品数据网上描述与识别

为了实现STEP的XML表达，以STEP Part21物理文件为研究对象，首先分析了EXPRESS与XML语言并建立匹配关系；然后建立基于数据实例层次结构树的XML DTD以实现通用的、统一的XML表达；最后结合原型系统SX－Viewer的实现过程和结果证明其可行性和实用性。