Unified feature model for the integration of CAD and CAx

Abstract

In the context of concurrent and collaborative engineering, the validity and consistency of product information become important. However, it is difficult for the current computer-aided systems to check the information validity because the engineers' intent is not fully represented in the product model. It is also not easy to check and maintain the consistency among related product models because information associations are not fully established. This research proposes and develops a feature-based product modeling scheme for the integration of computer-aided applications, especially CAD and CAPP integration. The scheme extends the traditional feature concept to a flexible and enriched data type, unified feature, which can be used to support the validity maintenance of product models. The novelty of this research is that the developed unified feature scheme is able to support data associations and propagation of modifications across product development life cycle stages. Therefore, it is a significant contribution to feature level interoperability in future virtual enterprises and collaborative engineering. In the proposed scheme, unified features provide an intermediate information layer to bridge the gap between engineering knowledge and product geometry. Unified features are also used to maintain geometric and non-geometric relations across product models. Major technical aspects of the developed scheme include: The identification of common properties and methods of different application features, and the definition of a generic, unified feature type that represents these common characteristics. A rule-based expert system is embedded into a feature-based product modeling system to handle non-geometric data and relations. A unified, multi-dimensional cellular model accommodates different geometric modeling requirements uniformly. Relations across the CAD and CAPP applications are identified and managed by a dependency network with a justification-based truth maintenance system. A database structure for sharing data and storing the inter-stage associations is developed. The feasibility of the proposed unified feature modeling scheme is demonstrated with a prototype system and three case studies which involve conceptual design, detailed design, and process planning.

Geometrical tolerance transfer for sheet metal forming processes

“…A simple feature-based flexible process planning system is laid out in figure 2.13. Tsang and Brissaud (1989); Regli et al (1995); Amaitik and Kilic (2005) Feature modeling and classification Vancza and Markus (1993) Roles of manufacturing features in process planning Herbert et al (1990); Joshi and Chang (1990); Dong et al (1993); Chan and Case (1994); Kim and Cho (1994); Subrahmanyam and Wozny (1995); Liu et al (1996); Kruth et al (1996); Regli et al (1997); Aldakhilallah and Ramesh 1997 Feature-based CAPP system Torvinen et al (1991); ; Hou and Faddis (2005); Chen (2007) Integration of CAD/CAE /CAM/CIM and CAPP Gupta and Nau (1995) Feature-based analysis of the manufacturability of machined parts Daftari (1996, 1997); ; Sun et al (2001) Feature composition and decomposition Srinivasan and Sheng (1999a,b) Feature-based process planning for environmentally conscious machining Source Main Topic Zhang et al 2000; Beg and Shunmugam (2003); Wong et al (2006) Feature-based inspection process planning Joo et al (2001); Shunmugam et al (2002b); Ding et al (2005); Singh and Jebaraj (2005); Liu and Wang (2007) Optimization by AI and KBE techniques Feature-based process planning was a hot research field in recent years. Although many researchers focus on developing CAPP systems or finding optimal process planning procedures, more and more attention is paid to the details of applying feature technique on process planning.…”

“…• A central associative feature-based database (AFDB) is utilized to share and associate geometrical and feature data. The data associations of the AFDB are established in two levels [Chen (2007)]:…”

“…Feature evolvement described how features evolve along with the product life-cycle, including their association and change management across product life-cycle stages. The feature evolvement progress is shown in figure 3.1 and an example for forming feature evolvement is shown in figure 3.2 (basic concepts are from [Chen(2007) • Conceptual design stage: A working structure composed of two conceptual design features, a s-shaped part feature and a hole feature, results in the specification of principles through abstracting the essential customer requirements, concept generation, establishing function structures, evaluating part configuration, etc. The S-shaped part feature is a basic feature and the hole feature is a subsidiary feature.…”