Multiresolution Representation of 2D CSG Models

Multiresolution is currently one of the main schemes used in CAD modeling for representing objects, particularly when large-scale geometric data must be transferred interactively over a network, as in the case of collaborative design. Increasingly complex products and growing competition have turned design into a collaborative team effort. Furthermore, the widespread development of Internet viewers has also necessitated the transfer and display of large-scale CAD models over networks. In order to reduce the volume of transferred data, efforts have been made to transfer CSG (Constructive Solid Geometry) models rather than those based on B_rep (Boundary Representation). This paper presents an original new method for speeding up data transfer by using multiresolution CSG models at different levels of details (LOD). The multiresolution CSG algorithm generates a hierarchy of multiresolution CSG trees; at each level, the shape is further approximated and represented by a smaller number of CSG primitives. The paper analyzes the proposed algorithm, and demonstrates its feasibility.     

Design of reconfigurable manufacturing systems

This paper explains the rationale for the development of reconfigurable manufacturing systems, which possess the advantages both of dedicated lines and of flexible systems. The paper defines the core characteristics and design principles of reconfigurable manufacturing systems (RMS) and describes the structure recommended for practical RMS with RMS core characteristics. After that, a rigorous mathematical method is introduced for designing RMS with this recommended structure. An example is provided to demonstrate how this RMS design method is used. The paper concludes with a discussion of reconfigurable assembly systems.     

Octree creation via C.S.G. definition

The common method for generating the octrees of complex objects, is based upon generating the octrees of several pre-defined primitives and applying Boolean operations on them. Regardless how the octrees representing the primitives are generated (top-down or bottom-up) the octree of a desired object is obtained by performing Boolean operations among the primitives comprising the object according to the object's CSG (constructive solid Geometry) representation. When carrying out this procedure, most of the computing and memory resources are used for generating and storing the octants comprising the primitives. However, the majority of those octants are not required for the representation of the final object. In this paper the extention of the top-down approach to the CSG level (i.e., generating the octree of an object directly from its CSG representation) is proposed. With this method there is no need to generate the octrees of the primitives comprising the object nor to perform Boolean operations on them. Moreover, only these octants which belong to the final object are generated.     

Maintenance: Changing Role in Life Cycle Management

As attention to environmental problems grows, product life cycle management is becoming a crucial issue in realizing a sustainable society. Our objective is to provide the functions necessary for such a society while minimizing material and energy consumption. From this viewpoint, we should redefine the role of maintenance as a prime method for life cycle management. In this paper, we first discuss the changing role of maintenance from the perspective of life cycle management. Then, we present a maintenance framework that shows management cycles of maintenance activities during the product life cycle. According to this framework, we identify technical issues of maintenance and discuss the advances of technologies supporting the change in the role of maintenance.     

Linear Programming and Genetic Algorithms Methods for Creation of Groups in Networks of Excellence

Creation of groups in Networks of Excellence (NoEs) based on knowledge mapping and expertise is a set covering problem known to be non-polynomial. Therefore it is usually approached by heuristic methods which yield good but not necessarily optimal coverage. Selecting teams to form a group within NoEs that are comprised of tens of teams can also be formulated and solved as an integer linear programming (ILP) problem whose solution is guaranteed to be optimal. This paper presents the ILP solution for team selection with typical objective functions. Several genetic algorithm-based methods are also compared to the optimal solution in terms of convergence (time and solution). The compared methods differ in selecting next-generation population schemes. The plain vanilla method is shown to be superior to both the roulette-based and the SUS methods.     

Identification of faces in a 2D line drawing projection of awireframe object

An important key to reconstructing a three-dimensional object depicted by a two-dimensional line drawing projection is face identification. Identification of edge circuits in a 2D projection corresponding to actual faces of a 3D object becomes complex when the projected object is in wireframe representation. This representation is commonly encountered in drawings made during the conceptual design stage of mechanical parts. When nonmanifold objects are considered, the situation becomes even more complex. This paper discusses the principles underlying face identification and presents an algorithm capable of performing this identification. Face-edge-vertex relationships applicable to nonmanifold objects are also proposed. Examples from a working implementation are given     

Part cost estimation at early design phase

Although 70% of part cost is determined during the early design stage, designers rarely accurately estimate the costs of their designs. Based on extensive literature review, in-depth industrial survey and close collaboration with multiple manufacturers, forty factors were identified as governing part cost and ranked according to cost impact. Based on parameter ranking and availability at the early stages of design, a cost estimator for designers is proposed. As the design progresses and more parameters become available, a more accurate cost model is derived and proposed to manufacturers. Results are analyzed and compared to actual manufacturing costing demonstrating good fit.     

Assembly system design and operations for product variety

Assembly is the capstone process for product realization where component parts and subassemblies are integrated together to form the final products. As product variety increases due to the shift from mass production to mass customization, assembly systems must be designed and operated to handle such high variety. In this paper we first review the state of the art research in the areas of assembly system design, planning and operations in the presence of product variety. Methods for assembly representation, sequence generation and assembly line balancing are reviewed and summarized. Operational complexity and the role of human operators in assembly systems are then discussed in the context of product variety. Challenges in disassembly and remanufacturing in the presence of high variety are presented. We then conjecture a future manufacturing paradigm of personalized products and production and discuss the assembly challenge for such a paradigm. Opportunities for assembly system research are summarized at the end of the paper.