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Product assembly design is a complex activity involving collaboration between several designers. Currently, many manufacturing firms out source the design and development of different portions of a product to different suppliers. Due to the absence of an integrated tool for collaborative product assembly design, designers currently follow an indirect approach. This makes collaboration an unorganized and inefficient activity. This paper discusses the architectural novelties and design considerations utilized to develop an integrated collaborative assembly design tool. Further, the scenarios of using such a tool are discussed in detail. This discussion highlights how the tool contributes towards making collaboration an organized and efficient activity and enables designers to rapidly design and prototype the product assembly.

Typically, during product design collaborating, designers share design data and assembly models. However, due to the limited bandwidth of the Internet transfer of detailed CAD based assembly models is slow. Therefore, tools based on polygonized representations of assembly models have been utilized during collaborative design. These models are primarily used for visualization, which is an important activity during modeling. However, providing the designers with the ability to perform real-time geometric modification, assembly constraints specification and concurrent design of different components/sub-assemblies will enable designers to collaborate effectively during design. This paper presents a new geometric representation called the AREP and a prototypical system (cPAD) that uses this representation, which implements the collaboration paradigm by supporting these activities.

Considerable progress has been made on automatic hexahedral mesh generation in recent years. A few automated meshing algorithms (e.g. mapping, submapping, sweeping) have proven to be very reliable on certain classes of geometry. While it is always worth pursuing general algorithms viable on arbitrary geometry, a combination of the well-established algorithms is ready to take on classes of complicated geometry. By partitioning the entire geometry into meshable pieces matched with appropriate meshing algorithms, the original geometry becomes meshable and may achieve better mesh quality. Each meshable portion is recognized as a meshing feature. This paper, which is a part of the feature based meshing methodology, presents the work on shape recognition and volume decomposition to automatically decompose a CAD model into hex meshable volumes. There are four phases in this approach: Feature Determination to extract decomposition features; Cutting Surfaces Generation to form the cutting surfaces; Body Decomposition to get the imprinted volumes; and Meshing Algorithm Assignment to match volumes decomposed with appropriate meshing algorithms. This paper focuses on describing feature determination and volume decomposition; the last part has been described in another paper. The feature determination procedure is based on the CLoop feature recognition algorithm that is extended to be more general. Some decomposition and meshing results are demonstrated in the final section.

The current paper presents a pseudo-sweep algorithm to determine whether a given volume constitutes an approximately swept shape for the purpose of hexahedral finite element mesh generation. The pseudo-swept shape determination approach consists of three steps. Step 1: Determining the source surface, target surface, and lateral surface of a given solid object B. Two requirements: topological and geometric requirements, are used to determine these three surfaces. Step 2: Creating a submappable lateral surface. A submappable surface is one that allows the sweeping of a two dimensional quadrilateral mesh from the source surface to target surface. Step 3: Modifying the topology of the source surface. If the topologies of the source and target surfaces are different, an approach called Topology Mapping is applied. The Topology Mapping approach maps the target surface to the source surface so that sweeping of quadrilateral mesh from the source surface to the target surface is possible. Once the above three steps are applied, a hexahedral mesh is generated by sweeping a quadrilateral mesh from the source surface, along the lateral surface, to the target surface.

Disassembling a selected component from an assembly, defined as selective disassembly, is important for applications such as maintenance, recycling and reuse. This paper presents a geometric algorithm to solve the following selective disassembly problem: given an assembly and a selected component to be disassembled, determine the disassembly sequence with minimum component removals (motions), defined as an optimum sequence. We propose an abstraction “wave propagation” that analyzes the assembly from the selected component outwards, and orders the components for selective disassembly. The main contributions of this research are: (1) determining an optimal disassembly sequence; (2) reducing the search space by analyzing a subset of components in the assembly; and (3) providing a polynomial average complexity algorithm. The proposed selective disassembly approach applies to both two dimensional and three-dimensional assemblies.

Virtual prototyping (VP) typically involves analyzing computer aided design (CAD) models for different end applications such as manufacturability or assemblability analysis. Such analyses may be performed via the aid of expert system agents which could be residing in a distributed fashion on the Internet. Each expert system agent/module requires CAD information at a certain level of geometric abstraction and outputs the analysis at a different level of abstraction. Therefore, a basis is needed to define these different levels of geometric abstraction. The current paper defines and analyzes these different levels of geometric abstraction in the context of an architecture for achieving VP via a central broker that interacts with these different modules—each providing a different level of abstraction.

In this thesis, a human-computer interaction approach for the generation of geometric shapes via multi-sensory user interface of a Virtual Reality (VR) based System is presented. Through the use of VR devices, geometric design can be more effectively inputted into the Computer-Aided Design (CAD) system in a natural and physically intuitive way. The focus of this research is on determining a set of efficient interaction approach by using the combinations of auditory, tactile, and visual sensory modalities to accomplish typical CAD tasks. In order to evaluate the efficiency of the proposed interaction approaches, prototypical VR-CAD systems are implemented as part of this research. A series of interface tests were performed on the prototypical systems to determine the relative efficiency of the interaction approaches. Interface test results indicate that auditory input, voice commands, are effective in operation activations such as rotating viewpoint, creating/deleting entities in the virtual environment. The tactile input, hand actions/motions, are found to be highly efficient for navigation, entity selection, complex 3D manipulations of entities and dynamically changing entity's dimension in the VR-CAD system. It is also determined that building simple geometry shapes containing canonical forms, such as blocks, cylinders, spheres, etc, using VR interface results in a speedup of 1.5 to 2.0 times over the traditional interface. For more complex shapes, the speedup factor is about 3 to 4 times. This indicates that there are greater benefits when designing complex geometry shapes than design simpler shapes in a VR CAD system. The contribution of this research lies on setting a new paradigm for multi-sensory input output interaction approaches of a VR based CAD system to provide an easy-to-use and effective tool for product shape design.

This paper describes an approach for creating concept shape designs in a virtual reality environment— covirds (COnceptual VIRtual Design System). Concept design refers to the ab initio design of a product or part. In concept design, the product details such as shape features and exact dimensions are not rigidly defined and the designer has some freedom in determining the shape and dimensions of the product. Current cad require the designer to specify shape and dimensions to create cad models of products even though these are probably not necessary at the concept development stage. covirds overcomes these drawbacks by providing a bi-modal voice and hand-tracking based user interface to the VR-based cad modeling environment. This interface allows rapid concept design creation without requiring time consuming shape description and the tedious specifications of exact dimensions.

The current research presents a feature-based approach to minimize the number of set-ups in the machining process planning system. It analyses machining features with a set of knowledge-based rules to determine the machining process plan for a part. In this approach, features are classified according to the number of possible tool approach directions that can be used to machine them. This divides features into two classes: single tool approach direction (STAD) features and multiple tool approach direction (MTAD) features. The process planning system groups all the STAD features with the same tool approach directions into one set-up. MTAD features are integrated, if possible, into these set-ups by choosing the appropriate tool approach direction for each MTAD feature. If this is not possible, a new set-up is created. This minimizes the total number of set-ups for machining the part. Knowledge-based rules are applied to guide the search for proper ordering between machining processes and set-ups of a part. Subsequently, a machining process plan with a minimized number of set-ups is created. The process planning system that uses this approach can serve as an integral part of a feature-based product and process design system.

The analysis of designs in single-piece part manufacturing during the design process results in significant benefits during the manufacturing stages. If manufacturability knowledge can be incorporated into the design, significant downstream problems may be eliminated. Manufacturing knowledge is often related to critiques on shape features that are special forms on parts that perform certain functions. The shape features required to analyze manufacturability are not always explicitly available in surface CAD models of parts, and they may need to be extracted. However, it is the variation of shape features with topology and geometry that makes the problem of feature recognition difficult. The research described in the paper focuses on shape-feature recognition that is based on the differential depth filter, which reduces the number of topological entities. A second level of operation causes the topological entities to be transformed into entities of a higher abstraction level called loops. Loops assist in reducing the number of entities in which features need to be searched for, which implies a reduction in the search space. Considerable success in feature recognition has been achieved for parts with varying topology and geometry and for parts with a relatively large number of topological entities (up to 30 000 faces and 40 000 edges).