This paper presents a virtual prototyping (VP) approach for geometric mouldability analysis of near-net-shape manufactured parts. The geometric mouldability of a part depends on the geometry of the part and is affected by the number and types of undercut features. A virtual prototype (VP) of a mold, which is a realistic digital product model, is generated by combining automated and interactive approaches to evaluate the mouldability of a part in the early stages of the product development cycle. The automated approaches for generating a VP are proposed to construct the parting surface, cores and cavity of the mold based on the recognized undercut features. Interaction with the VP in the virtual reality environment allows the designers to evaluate the mouldability of a part in an intuitive way. A new volume-based feature recognition method and data structure using non-directional blocking graph (NDBG) have been developed to recognize both isolated and interacting undercut features in a uniform way. Firstly, a set of potential undercuts are generated by performing the regularized difference between the part and its convex hull. The optimal parting direction is then determined by minimizing the number of undercuts. Finally, undercut features are identi

This paper presents an approach to find feasible and practical plans for mechanical assemblies based on a connector-based structure (CBS) hierarchy. The basic idea of the approach is to construct plans for an assembly (i.e. the root node of the CBS hierarchy) by systematically merging plans for primitive structures in the CBS hierarchy, while the plans for primitive structures are built using one of three methods: by reusing the existing plans, by retrieving the stored plans, and by geometric reasoning. The input to the approach consists of the assembly solid model, the connector-based relational model (CBRM) graph, the spatial constraint graphs, and the selected base part for the assembly, all of which are assumed to be generated previously in an interactive and/or automated way. Then, a CBS hierarchy for the assembly is automatically derived from the input CBRM by firstly establishing its functional model, which is constructed from the CBRM by decomposing the assembly or resulted part sets with respect to their connectors. Based on the CBS hierarchy, a set of assembly precedence diagrams representing good plans for the assembly are generated by merging plans for primitive structures systematically in a bottom-up manner. It can be proved that the proposed approach is both correct and complete. To verify the validness and efficiency of the approach, a variety of assemblies including some complicated products from industry are tested in the experimental CBHAP planner.

It is desirable to integrate assembly planning with design early in the product development process. Usually, assembly plans can be generated by using either automated or interactive approaches. However, both kinds of approach have limitations. Interactive approaches require extensive user input in the tedious form of answering questions, whereas automated approaches can only be applied to products with simple component configuration and geometry. Based on virtual prototyping (VP), an intuitive and efficient approach is proposed for assembly planning by combining the potential strengths of the two kinds of approach. The main idea of this approach is to extract human expertise of mechanical assembly from human-computer interaction, and then use it for the automatic generation and interactive evaluation of assembly sequences. To incorporate expert knowledge, one or a few initial sequences are firstly created in a teaching by showing way using the human-computer interface of virtual reality, where some intuitive and meaningful information such as motion path and assembly tool is captured automatically. Then, after representing assembly constraints as precedence expressions by reasoning about these initial sequences, all feasible sequences are generated efficiently based mainly on simply symbolic reasoning in place of costly geometric reasoning. In this way, the complexity of assembly sequence planning is reduced dramatically from seeking paths in a high-dimensional state space into a discrete graph-based searching problem. Finally, practical or good sequences are selected from the feasible sequences by exploiting the VP intuitive manipulation capability for judging the cost of a particular assembly operation. In the present authors' experience, VP-based interaction has been proven to be a powerful and intuitive paradigm for both generation and evaluation of assembly plans. The feasibility of the proposed method is demonstrated through an implemented prototypical system called VPASPE, which has been tested with some practical assemblies.

Accessibility is a kind of important design feature of products, and accessibility analysis has been acknowledged as a powerful tool for solving computational manufacturing problems arising from different manufacturing processes. After exploring the relations among approachability, accessibility and visibility, a general method for accessibility analysis using visibility cones (VC) is proposed. With the definition of VC of a point, three kinds of visibility of a feature, namely complete visibility cone (CVC), partial visibility cone (PVC) and local visibility cone (LVC), are defined. A novel approach to computing VCs is formulated by identifying C-obstacles in the C-space, for which a general and efficient algorithm is proposed and implemented by making use of visibility culling. Lastly, we discuss briefly how to realize accessibility analysis in numerically controlled (NC) machining planning, coordinate measuring machines (CMMs) inspection planning and assembly sequence planning with the proposed methods.

This paper presents a methodology for mouldability analysis by finding the optimal cavity design scheme (CDS) based on manufacturing and cost considerations using part geometry, where a CDS refers to a combination of the parting direction, parting line (PL), and undercut features (UF). The methodology takes advantage of geometric reasoning and fuzzy evaluation, and consists of two main stages: (1) generating all possible design alternatives, and (2) choosing the best alternative. In the first stage, after recognizing the potential UF from the given part, a spherical arrangement is constructed by partitioning the unit direction sphere using outward normals of the part's surfaces with the property that each cell in this arrangement has a unique combination of PL and UF set. Thus all design alternatives can be identified in O