基于特征的制造工艺资源建模与检索方法研究

为表达制造工艺资源特征层次结构、分类结构及资源对象关系,采用面向对象与特征建模技术构建了制造工艺资源特征模型,用特征映射技术描述零件结构特征与加工特征、加工特征与加工方法特征、加工方法与制造工艺资源特征的映射关系和模糊决策方法。研究了用工序特征描述工艺设计过程所对应的资源特征的集,并以形式化表示,提出了从制造工艺资源数据库中检索工序资源特征,以特征参数的相似性计算来检索与工序匹配的资源特征的检索算法。最后,将该方法应用于工艺设计中制造工艺资源特征与工序特征的匹配。     

基于零件三维模型的可制造性分析技术研究

CAD系统建立的是采用面向几何造型的特征模型,与制造特征在形状、拓扑结构、特征关系等方面有显著的不同,不能直接应用于后续的工艺性分析与工艺设计。采用了面向制造特征的特征识别技术,通过设计几何拓扑模型建立制造特征模型,然后通过建立加工工艺性评价知识库、规则库,实现基于三维制造特征模型的加工工艺性分析。     

基于特征模型的特征相交识别

在对铣、钻类特征相交关系分析和研究的基础上,运用增量式制造特征识别法设计出相交特征映射识别系统。该系统能有效地识别出新建设计特征与已识别制造特征的相交关系,实现设计特征的映射和识别。识别产生的零件制造特征解释模型和制造特征信息库能有力地支持设计的可制造性分析。     

三维机加工工艺工序间模型快速创建方法

为达到机加工零件快速工艺设计的目的,对快速创建工序间模型的方法进行了研究。根据机加工零件模型加工特征的生成方式及特点,将加工特征分为凹陷特征、凸起特征和过渡特征;以特征识别技术为基础、特征面组为研究对象,结合工艺知识识别出所需加工特征的面组;运用半空间思想及基本建模方法,获取制造特征体并保存;获取所有制造特征体后生成零件毛坯模型,与获取的制造特征体进行布尔操作,快速创建工序间模型。以某机加工零件为例,对该算法进行了实例验证。     

面向三维机加工艺规划系统的尺寸信息模型构建

在数字化工艺设计领域,制造特征识别技术是连接CAD和CAPP的桥梁,并将MBD模型的几何和非几何信息转换为CAPP可识别的特征属性。然而,标注尺寸在工艺设计领域与CAD中表达方式的差异,阻碍了特征识别对应的尺寸信息作为其属性信息。在重点研究二者表达方式的不同点后,为了构建适用于三维机加工领域的尺寸信息模型,将尺寸依附体抽象转化为工艺上有意义的面或中心线,促进了设计特征与制造特征之间的转化,为后续的工艺规划提供了更加完善的制造信息。     

基于加工特征和制造资源约束的CAD/CAPP研究

针对齿轮箱类零件的快速设计与制造,建立了制造资源管理模块,通过加工能力约束文件将制造资源与可加工特征类型及范围对应起来,设计开发了基于加工特征建模的CAD模块和基于制造资源约束的CAPP模块。基于加工特征的建模方式使得CAD与CAPP得以无缝集成,而加工能力约束文件则为CAD/CAPP集成系统提供了实时反映底层制造能力的结构设计和工艺设计约束,从而保证了设计和工艺的可制造性。     

基于制造资源的复杂箱体零件加工特征识别方法

针对复杂箱体零件的加工特征识别问题,介绍了一种基于制造资源的特征识别方法。在分析加工工艺环境中机床、刀具和夹具的基础上,对制造资源进行了参数化定义,获得了制造资源模型。以STEP/AP203中性文件为数据源,获得了三维零件模型的加工表面,根据加工表面与制造资源的映射关系,获得每个表面的制造资源组合方案,即特征因子,并以提高加工效率和经济性为目标,对特征因子进行优化筛选。将同一装夹下采用同一刀具和机床运动模式的加工表面聚类为一个加工特征,完成零件特征识别。     

发动机快速工艺过程优化技术研究

本文从制造特征的角度对现行的发动机部件机体、缸盖加工工艺过程进行优化.通过采集工艺知识,将现行的工艺经过整理和分析然后将其转化为基于特征的工艺知识充实工艺知识库,并对加工工艺知识进行分析分解,通过针对零件特征制造方位面的特征比较,应用制造特征与加工工艺元映射和优化算法工艺路线优化技术,进行工艺方案设计,缩短工艺设计周期,提高数控设备的利用率,减少加工成本,提高加工精度.     

基于特征的电动机轴CAD/CAPP/CAM集成系统研究

利用基于特征的设计思想,将电动机轴的设计特征、工艺特征和加工特征封装在一起;在产品设计阶段采用基于特征建模的设计方法,工艺规划阶段自动继承CAD系统生成的产品设计信息,并与加工方法相对应,生成CAM所需的数控加工程序。使零件在整个制造中实现信息采集、传递和加工过程的畅通无阻。     

面向设计制造的船用柴油机零件全三维数字化定义研究

基于全三维的数字化定义是产品设计制造一体化的发展趋势,针对船用柴油机零件结构复杂等特点,实施全三维数字化定义方法.采用基于特征的三维标注技术和数据管理技术,同时将设计信息、加工制造信息和工艺信息依据制造工序进行合理组织与管理,置于三维软件平台中.在制造时,直接在三维模型上识别加工制造信息和工艺信息,摆脱二维图纸束缚.实验表明,采取该方法可以实现基于全三维模型的统一数据源,满足设计制造对全三维数字化模型的要求.     

An integrated fixture planning system for minimum tolerances

Fixture planning is an important aspect of process planning. The steps involved in automatic fixture planning are manufacturing feature recognition, setup planning and fixture configuration planning. In the present work, an integrated setup and fixture planning system is developed for minimum tolerances at critical regions using a data exchanged part model as an input. A platform-independent STEP-based automatic feature recognition system that can recognize both design and manufacturing features, including intersecting features is implemented. An automatic setup planning module is developed for generating setup plans for complete machining of a given component. A fixture planning module is developed applying the criteria of uniqueness, stability, accessibility and tolerance minimization. A case study is presented to demonstrate the capabilities and integration between the various modules of the system.     

Principal Face-based Recognition Approach for Machining Features of Aircraft Integral Panels

Feature recognition aims at extracting manufacturing features with geometrical information from solid model and is considered to be an efficient way of changing the interactive NC machining programming mode.Existing recognition methods have some disadvantages in practical applications.They can essentially handle prismatic components with regular shapes and are difficult to recognize the intersecting features and curved surfaces.Besides,the robustness of them is not strong enough.A new feature recognition ap...     

Decomposition of interacting machining features based on the reasoning on the design features

Currently, design and machining features diverge in meaning, even when they are interpreting the same object. This divergence of feature interpretation provides a venue for research work to reduce the complexity that arises in recognizing interacting machining features. Therefore, this paper demonstrates the recognition of design features with the aim to eventually decompose the interacting machining features. Loop driving recognition links the CAD data directly to the features to be recognized. The first step is to recognize the design features from B-Reps part. Then geometrical reasoning on these design features is employed to convert the design features to its respective machining features. The process of conversion is in fact the process of decomposing the interacting machining features without having to visit the B-Reps data again. The system takes into account the nesting of the design features that causes more interacting machining features to be decomposed. Finally, output data of both design and machining features are then displayed.     

Generating Alternative Interpretations of Machining Features

One of the major difficulties in extracting machining features is the lack of a systematic methodology to generate alternative ways of manufacturing a machined part. Most of the early research in feature extraction and process planning has not considered this aspect, and has focused on the generation of a single interpretation. In this paper, we propose a feature-based approach to generating alternative interpretations of machining features from a feature-based design model. The proposed approach simplifies the generation of alternative machining feature models by using information on feature which is captured and maintained during feature-based model-ling and machining feature extraction. A set of machining features is incrementally extracted during the feature-based design process of a machined part. A feature conversion process converts each design feature into a machining feature or a set of machining features by using information on the geometry and the feature. Using reorientation, reduction, and/or splitting operations, alternative models are generated from the sets of extracted machining features. During the execution of each operation, unpromising models are pruned by using criteria such as minimising the number of accessibility directions. The machining features and their precedence relationships are represented in a STEP-based machining feature graph for the purpose of data exchange.     

An approach to incremental feature model conversion

A new approach to converting a design feature model (DFM) to a machining feature model (MFM) step-by-step during a design process has been proposed. In the approach, the MFM is incrementally set up and updated through performing a local machining feature recognition on certain areas of a design part’s B-rep when its design features are updated. The areas to be recognized as machining features are determined through geometric reasoning according to the statuses of the DFM and the dynamically generated MFM of the part. To facilitate the above geometric reasoning, a dynamic link list (DLL) has been developed to record the changed topological elements during the design process and the relationships between the DFM and the MFM. Based on the automatic and effective conversion process from design models to machining feature models, the proposed approach can support the establishment of a concurrent product development environment to link product design and manufacturing processes seamlessly.     

Automatic recognition of intersecting features for side core design in two-piece permanent molds

The automatic recognition of molding features (protrusions, depressions, and their intersections), core, and cavity surfaces plays an important role in shortening the lead time in mold design and manufacturing as well as aiding the side core design. Consequently, in this paper, an automatic mold feature recognition system to recognize protrusion, depression as well as intersecting depression features is proposed and implemented. The recognition of various types of intersecting features is a significant contribution to the literature. The output generated by the accessibility analysis (without discretizing the part) is used as the input to the feature recognition module. The newly developed system is assessed by comparing its results with those of earlier systems. A comprehensive case study is presented that can demonstrate the additional capabilities of the proposed system to those of the present in the published literature.     

基于三维几何特征的产品报价方法

针对当前主流报价系统对产品实例库的多样性和时效性要求高且报价响应效率低的问题,在研究自动特征识别技术和CAD二次开发方法的基础上提出了基于三维几何特征的产品报价方法。首先,对常用设计特征进行分类并建立设计特征标识号、设计特征和加工特征间的映像关系,利用特征标识号和设计特征间的一一映像关系完成设计特征的识别,结合设计特征与加工特征的映像关系实现加工特征的识别;其次,通过零件的材料费用和特征加工费用进行零件的报价研究,综合产品、部件及零件的报价层次关系建立产品报价模型;再次,为快速响应用户个性化需求,建立了从用户需求到产品配置再到快速响应报价的服务模型;最后,开发了基于Creo的三维几何特征的报价系统,并将该报价系统应用于某企业大功率逆变器报价中,提高了产品报价效率,验证了基于三维几何特征的产品报价方法的可行性。     

Automatic recognition of design and machining features from prismatic parts

Prismatic parts usually comprise basic features, such as slots, steps, holes, bosses, which may intersect with one another. In general, automatic recognition of intersecting features is difficult and may present bottlenecks when automating the design procedures which make use of features for downstream operations.This paper presents a novel approach to recognising intersecting features and auxiliary features due to tool movements and cutter radii. Since no cutting edges can be perfectly sharp, corner fillets on machined features are invariably created by end mills and other cutters. Fillets, on the other hand, could very well be features which have been designed to increase strength and reduce stress concentration of certain features. A feature recognition system is proposed to recognise features having fillets which may be either design or manufacturing features. This information will be useful to the product designer as it would be possible to distinguish between the intended and unintended features of a part. The developed system has been implemented on an HP-ME30 Solid Modeler.     

基于图的体积分解的加工特征识别方法

为有效提取实体边界模型中的2．5维加工特征,提出了一种实用、可行的特征识别方法。该方法参考毛坯的实际加工过程,从零件毛坯模型中分解出待加工体积;沿待加工体积的进刀方向逐层分解出局部组合特征;依据局部组合特征顶面凹凸性特点,进一步分解,重新组合为通用型加工特征;匹配特征相互关系,构成特征关系图。研究了每个步骤的相应算法,这些算法以基于图的布尔运算为基础,通过特征边界的重构,形成完整的特征边界,并最终生成体积特征。该方法适用于与设计下游单元的有效集成。通过对典型2．5维加工零件的测试,证明了该方法的有效性和实用性。     

Extraction of machining features for CAD/CAM integration

Feature-based CAD/CAM integration is a technology used to realise automatic transmission and conversion of component information among CAD, CAPP and CAM applications. A feature is the medium of information transmission in the integration. Since a process planning downstream application has a different viewpoint from the component designer, feature conversion or feature extraction methodology is used to create a machining feature model based on the design feature model. One of the major difficulties in generating machining features is the preservation of feature integrity because of feature interactivity. The most current research, therefore, focuses on the planar-type form feature conversion. This paper discusses the problem of feature interactivity and proposes a feature-based approach to generating hole-series machining features from a design feature model. Hole-series features are important machining features for gearbox components used in machine tools. These kinds of features cannot be obtained directly from a design feature database. A constraint-based method is developed in this paper to define a hole-series feature model based on the geometric and topological information extracted from the design database. In addition, a STEP file is generated to interface the converted machining feature model with the downstream CAPP application. The implemented feature conversion system is verified by considering its application to some component examples and the developed prototype CAPP system. This revised version was published online in October 2004 with a correction to the issue number.