In reverse engineering, when a shape containing multi-patched surfaces is digitized, the boundaries of these surfaces should be detected. The objective of this paper is to introduce a computationally efficient segmentation technique for extracting edges, ad partitioning the 3D measuring point data based on the location of the boundaries. The procedure begins with the identification of the edge points. An automatic edge-based approach is developed on the basis of local geometry. A parametric quadric surface approximation method is used to estimate the local surface curvature properties. the least-square approximation scheme minimizes the sum of the squares of the actual euclidean distance between the neighborhood data points and the parametric quadric surface. The surface curvatures and the principal directions are computed from the locally approximated surfaces. Edge points are identified as the curvature extremes, and zero-crossing, which are found from the estimated surface curvatures. After edge points are identified, edge-neighborhood chain-coding algorithm is used for forming boundary curves. The original point set is then broke down into subsets, which meet along the boundaries, by scan line algorithm. All point data are applied to each boundary loops to partition the points to different regions. Experimental results are presented to verify the developed method.

Solid freeform fabrication technology, widely known as rapid prototyping an rapid tooling, can create physical part directly from digital model by accumulating layers of a given material. Providing a tremendous flexibility of a part geometry that they can fabricate, these technologies present a opportunity or the creation of new products that can not be made with existing technologies. For this to be possible, however, various design environments including different fabrication processes needs to be considered at the time of design, and finding an appropriate design solution for the new product by combining necessary design communications become increasingly complex as environmental condition become diverse. This paper proposes a geometric modeling paradigm for design and fabrication of a new product, honeycomb structural geometry.

Presented in this paper is an algorithm for finding all intersections among polygonal chains with an O((n+k)·log m) worst-case time complexity, where n is the number of lien segments in the polygonal chains, k is the number of intersections, and m is the number of monotone chains. The proposed algorithm is based on the sweep line algorithm. Unlike the previous polygonal-chain intersection algorithms that are designed to handle special only cases, such as convex polygons or C-oriented polygons, the proposed algorithm can handle arbitrarily shaped polygonal chains having self-intersections and singularities (tangential contact, multiple intersections). The algorithms has been implemented and applied to 1) testing simplicity of a polygon, 2) finding intersections among polygons and 3) offsetting planar point-sequence curves.

This paper presents a 3D-conferencing system as a prototype implementation of concurrent and distributed engineering environment using CORBA-Java and SDAI-Java. The system consists of some client and server objects that communicate with each other via ORB. The server objects use lightweight version of current working draft of SDAI-Java to access STEP product data models, and the client objects provide user-friendly graphical interface. The proposed system can be used for communicating with 3D CAD data between remote designers, manufactures and customers regardless of he H/W or S/W platforms they use.

An efficient management of product information is critical to the enhancement of corporate competitiveness. Product information is often distributed in term of organization, geography, and time. With the rapid increase in the use of Internet or its associated Web and intranets, it has been accelerating to integrate the distributed information. In this research, a Distributed, Open, Intelligent Product data Management system, namely DOI-PDM, is developed. This system deals with product information following the STEP standard, and its operation is controlled by a Web-based workflow management system. CORBA is employed to ensure interoperability among distributed objects. It is intended to achieve openness by using various standards, such s STEP, KQML, SGML, and WfMC specifications. One major difficulty in managing it needs also be properly modified according to the dynamics. It however is very hard to have a prior anticipation to the dynamics. It however is very hard to have a prior anticipation to the modification requirements in practice. We introduce a process adaptation model and a use of intelligent agent technology. An agent is delegated to modify process definitions during run-time. A method of agent implementation and a proper communication scheme among te agents are proposed. Also developed in this research is a STEP-based content search system which can co-work with the agents by providing relevant product information that the agents require.

This paper proposes a case-based approach to the conceptual design of mechanism, especially of the generation of design alternatives in function generation and motion transmission tasks. The aim of this work is to generate and provide various design alternatives by utilizing the previous design concepts underling in the existing design cases. The approach is based on the basic idea that the whole design concepts or sub-concepts extracted from different design cases can be merged to generate a variety of new design alternatives. The notion of virtual function generator is introduced to conceptualize and represent all possible underlying design concepts in the prior design cases. The virtual function generators are extracted in advance from the existing mechanism and serve as new conceptual building blocks for the synthesis of mechanism. Various design alternatives are generated basically by merging tow virtual function generators that partially match the specified function. By utilizing the design concepts that have been effectively used in the previous design cases. he proposed approach could efficiently produce more feasible design concepts than from-scratch ones. The approach proposed in this paper is illustrated with a design example.

The modeling method to support product development processes (PDP) must have certain characteristics including the ability to represent multiple viewpoints of the product development and integrate with currently available analysis and design methods based on CE concept. This paper describes the reference model to support multiple viewpoints (PPO: Products, Processes, and Organizations/Resources viewpoints) of the product development processes, from which each model (Products model, Processes model, and Organizations/Resources model) can be extracted, as well as produces PPO data schema. This reference model has associative relationships among the products, processes, and organizations/resources. To allow the extensibility to support design evolution, we propose structured dat representation methods using semantic network, which can be constructed through first-order logic. The product development processes is so represented by specifying entities and semantic relationships among them hat he appropriate information can be accessed and all of the relevant attributes about the entities can be retrieved simultaneously.

With the contemporary CAD/CAM system, where the tool path is generated and verified purely based on the geometric operation, geometric accuracy of the machined surface cannot be guaranteed dut to the cutting mechanics, meaning that the cutting mechanics should be incorporated in some fashion. In this paper, we incorporate the instantaneous cutting force and the tool deflection phenomena in predicting the machined surface for the finish-cut and milling operation. For the given NC dat including cutting conditions, the developed algorithm computes cutting force and deflection amount along the tool trajectory, and outputs the 3D graphic model of the machined surface together with error analysis. The validity and accuracy of the presented method has been tested by the actual cutting experiments. Experimental results and accuracy enhancement method together with implementing architecture of the VMCS (Virtual Machining CAM System) are discussed in the paper.

In order to reduce the cost of product and save the processing time, optimal nesting of two-dimensional part is an important application in number of industries like shipbuilding and garment making. There have been many studies on finding the optimal solution of two-dimensional nesting. The problem of two-dimensional nesting has a non-deterministic characteristic and there have been various attempts to solve the problem by reducing the size of problem rather than solving the problem as a whole. Heuristic method and linearlization are often used to find an optimal solution of the problem. In this paper, theoretical and practical nesting algorithm for rectangular, circular and irregular shape of two-dimensional parts is proposed. Both No-Fit-Polygon and Minkowski-Sum are used for solving the overlapping problem of two parts and the dynamic programming technique is used for reducing the number search spae in order to find an optimal solution. Also, nesting designer's expertise is complied into the proposed algorithm to supplement the heuristic method.

Surface/surface intersection is a common and important problem in geometric modeling and CAD/CAM. Several methods have been used to approach this problem. All possible intersection curves can be obtained by using the subdivision algorithm, while it requires a great deal of memory and is somewhat inefficient. The tracing algorithm is much faster than the subdivision algorithm, and can find points on the intersection curve sequentially. But, the tracing algorithm has some problems in the intersection curves on surface boundaries. In this paper, an Improved tracing algorithm that includes some ideas such as a new trace-terminating condition for the intersection curves on surface boundaries, detecting closed intersections and extension for composite surfaces is suggested. This algorithm consists of three step: generating state points for curve tracing, tracing intersection curves and sorting pieces of the intersection curves. The results of this algorithm and comparisons to the 'DESIGNBASE' and 'ACIS' system are presented.