Automotive air filter pleat parameters must often be estimated by design engineers, affecting overall filter performance. This paper examines pressure-flow response of and particle deposition upon three different pleat profiles. Pleat models, analysis operating point, and analysis parameters were based on a Purolator automotive air filter application. Computational assumptions included steady state, incompressible, isothermal, laminar air flow with a modified/extended Darcy law equation used for media flow computations. Inlet velocities were set to maintain the filter rated volumetric flow rate with equal pressure drop through each pleat model. 1–50 micron diameter spherical particles were used in Monte Carlo particle deposition analyses. Once introduced into the computed flow fields, particle trajectories were computed assuming inertial, body, buoyancy, and drag forces were active. Histograms depicting particle starting and deposition locations were constructed for five particle size sub-classes. Flow field and structural influences on particle deposition tendencies were noted.

Shape feature information about a part is required to analyze the part for downstream issues such as manufacturability and assemblability. One method of obtaining the feature information is feature recognition from the geometric model. This paper presents an approach called Curvature Region (CR) approach for feature determination in solid models. The CR-approach categorizes features into two primitive shape classes: protrusions and depressions. In the first step, these primitive shape classes are recognized from the solid model. In the next step, the primitive shape classes are analyzed using rules to obtain features. Primitive features are found by first converting the boundary representation (B-Rep) of the CAD model to a higher level of representation called Curvature Region Representation (CR-Rep). Curvature Regions are then grouped together to form Minus-Minus Centers (MMCs) and Plus-Plus Centers (PPCs). Primitive shapes are then defined in terms of these centers.

The release into the atmosphere of toxic, flammable and explosive materials is extremely dangerous. If an ignition source is found, the resulting fire can often be devastating. Pertinent information and calculations are given related to the evolution (source release models), dispersion (contaminant dispersion models), and possible ignition of released material.

New techniques for visualizing feature models are presented. These do not only provide better geometric and spatial model insight than the standard display techniques, but also functional insight into a feature model by visualizing engineering information. Geometry is visualized by combining shaded and line visualization techniques, resulting in clearer images. Among the engineering information that is visualized are feature intersections, closure faces and feature parameters. This is done by explicitly displaying feature geometry instead of the geometry of the final shape only, and by displaying additional information in a model image. Combined, these techniques provide powerful possibilities to visualize feature models. The implementation uses specified feature and camera properties and a cellular geometric datastructure for generating images. The cellular data structure contains the feature geometry information required for feature visualization.

Most process planning systems solve process planning problem for individual parts. Quite often, many different parts can be produced on shared setups. However, plans generated by current process planning systems fail to exploit this commonality between setups and try to generate optimal setups for individual parts. In this paper, we present an algorithm for multi-part setup planning. This algorithm takes a family of parts and tries to find a composite setup plan that can work for every part in the part family. Our setup planning algorithm employs a new two-step approach to handle multi-part setup planning problems. First, we identify the setup constraints imposed by various bending operations in the part family. These setup constraints describe spatial constraints on sizes and locations of various tooling stages in the setup. After identifying setup constraints, we try to generate setup plans that can satisfy all setup constraints. Any setup plan that satisfies all setup constraints is capable of accommodating every part in the part family. Setup changes constitute a major portion of the production time in batch production environments. We believe that multipart setup planning technique can be used to significantly cut down the total number of setups and increase the overall throughput.

This paper presents a computer-aided modular fixture design system: FIX-DES. When fixturing requirements are specified as locating/clamping surfaces and points, a fixture configuration will be automatically generated by (1) selecting fixture elements from a fixture element database to form fixture units based on fixture element assembly relationships and (2) placing the fixture units and elements into position on a baseplate while the fixturing requirements and assembly relationships (e.g., hole alignment) are maintained. The fixture element assembly relationships can be automatically established when the geometric models and fixturing functions of the fixture elements are specified so that the FIX-DES system can be easily applied to different fixture systems. The system also provides the interactive design and design modification functions for human expert involvement. The system was developed with core programs in C/C++ and interface programs in a specific CAD environment. The system has been successfully applied in industry and can be easily transferred to other CAD systems. The overall structure of the FIX-DES system is introduced in the paper. The development of the automated fixture configuration design (AFCD) functions are presented in detail. Finally a fixture configura-tion design example is given to illustrate the application of the system.

In this study, typical solid waste processing systems are analyzed. Then, a rotary screen and conveyor is designed for composting plants. A computer program is developed for the design procedure. By use of a simulation model included in the program, data are obtained and these are plotted to see system characteristics. These data then, are compared with the previous works.

This paper describes the current status of our feature recognition method using a convex decomposition method called Alternating Sum of Volumes with Partitioning (ASVP) . Volumetric form features are recognized from a part’s boundary representation by applying combination operations to the ASVP decomposition of the part to obtain a Form Feature Decomposition (FFD). The FFD can be post-processed to obtain application-specific feature representations; in particular, the conversion to the Negative Feature Decomposition (NFD), a machining feature representation, is described. Our domain of recognizable parts includes those having planar and cylindrical surfaces such that all cylindrical surfaces are bounded by straight edges and circular arcs, or are blending surfaces resulting from applying constant-radius blending to the part. We report the results of applying our method to the test parts for the 1997 Computers in Engineering Feature Panel Session.

Current feature-based modeling systems fail to adequately maintain feature semantics. This is partly due to inappropriate specification of validity conditions in feature classes, but mainly due to a lack of effective validity maintenance mechanisms throughout the modeling process. A critical aspect in this is feature interaction management. This paper presents a new approach to the detection of feature interactions, which uses semantic and interaction constraints in feature class specification. Validity maintenance is automatically performed after each modeling operation by checking these constraints, thus being able to detect a variety of interaction types. Such interactions are then analyzed, and their causes identified and reported to the user.

Changing worn tools is a major concern in planning operations on machining systems. Strategies for replacing tools range from changing each tool as it reaches its projected tool life, to changing all tools when the tool with the shortest life on the machining system is expended. Intermediate strategies involve changing tools in groups. Each of these strategies has two cost components associated with it: (1) the cost of lost production due to machine tool stoppage, and (2) the cost of unused tool life. The best tool grouping strategy minimizes the combined cost of lost production. In this paper we present an approach for finding good tool grouping strategies from inputs that include the tool utilization for a given machining application, and the tooling and machining system costs. A genetic algorithm is used as the underlying optimization paradigm for finding the minimum cost strategy. An example is presented for a part produced on a machining center.

An integrated design for manufacture system that performs manufacturability analysis simultaneously in two domains using interchangeable process specific entities is presented. This new approach is illustrated by an integrated system that creates and evaluates parts for manufacture by injection molding using a C-entity, and simultaneously creates and evaluates its mold for manufacture by milling using the fundamental manufacturing entity for milling. The entity for the part manufacturing process is chosen as the complement of the entity for the mold manufacturing process. This obviates the need for converting features from one manufacturing domain to another, and also permits a single uniform data structure to capture the shape characteristics of parts made in the two manufacturing domains. Since all the shapes are represented in the same way, the manufacturability evaluation of the part and the mold is reduced to a small set of algorithms based on an evaluation of the entity’s profile. It is demonstrated that by using process specific entities one can perform manufacturability evaluation of a part without either feature extraction or designing with features. The advantages of using the process specific entities approach for design and manufacturability evaluation over the feature recognition and the design by features approach are enumerated.

This article deals with concurrent design of sheet metal forming product and process by using process modeling and knowledge-based approach. An inverse finite element algorithm and knowledge representation schemes are presented. Numeric models out of process modeling are integrated into knowledge base, with resort to a mathematical and graphical software MATLAB and to a supporting shell called “concurrent design environment” (CDE) developed in Common Lisp. The proposed system can make preliminary determination of product and process specifications such that the product is compatible with its targeted forming conditions with maximum material utilization ratio, shortest lead-time, and reliable quality.

This paper describes the functionality of a Feature Recognition system, known as FeatureFinder. The system’s algorithm has been developed from a graph-based approach to feature recognition and is now capable of identifying a variety of features on a wide range of machined components. The system has been designed to be used within a solids machining package and identifies features from a specified tool approach direction. The paper details the result of applying the algorithm to the CIE97 test pieces. Features are identified on all of the components and the paper concludes with a brief description of on-going work designed to extend the range of components FeatureFinder’s algorithm can analyse.

This paper presents a new approach for automatic recognition of machining features from the B-Reps of the part. In this approach we combine the conventional graph based recognition method with the hint based feature recognition idea so as to efficiently handle feature interactions and provide alternative interpretations of interacting features. A Manufacturing Face Adjacency Graph proposed here is useful for improving the recognition of isolated features and effectively reducing the search space for virtual links, unifiable faces and features. Isolated (non-intersecting) features are recognized first based on the Manufacturing Face Adjacency Graph. Then, interacting features are recognized based on the Feature’s Minimal Condition Sub-Graph (MCSG) which is proposed as feature hint. The MCSGs for all types of features are defined, generated and completed in a uniform way, independent of feature type. Feature definitions are based on an extended Attributed Adjacency Graph, generated by graph decomposition and completed by adding related virtual links. An efficient algorithm for generating virtual links is developed. A new feature interaction classification and a virtual link classification are also described. Our approach can produce alternative interpretations of intersecting features. The main contribution of this paper is a methodology for recognizing interacting features in a uniform way.

An integrated system to support both product and manufacturing process design should be such that (1) the part design can be evaluated and redesigned based on manufacturability analysis and (2) the manufacturing processes can be selected efficiently and flexibly exploiting product information provided by part design representations. In this paper, we describe the collaborative research of the University of Illinois at Urbana-Champaign (UIUC) and the University of Michigan (UM) in computer-aided process planning for mill-turn machining. The UIUC geometric reasoning system based on convex decomposition identifies the machining features and maps the negative feature volumes to machining process methods, and generates geometry-based machining precedence relations. The UM process planning system based on genetic algorithm determines machining process sequences and assignment to multiple spindles and turrets.

A semi-analytical method and a computer program are developed for inverse kinematics solution of a class of robotic manipulators, in which four joint variables are contained in wrist point equations. For this case, it becomes possible to express all the joint variables in terms of a joint variable, and this reduces the inverse kinematics problem to solving a nonlinear equation in terms of that joint variable. The solution can be obtained by iterative methods and the remaining joint variables can easily be computed by using the solved joint variable. Since the method is manipulator dependent, the equations will be different for kinematically different classes of manipulators, and should be derived analytically. A significant benefit of the method is that, the singular configurations and the multiple solutions indicated by sign ambiguities can be determined while deriving the inverse kinematic expressions. The developed method is applied to a six-revolute-joint industrial robot, FANUC Arc Mate Sr.

A wide range of applications deal with the manipulation and expression of process-centered collections of activities. Each of these applications serves a specific audience and need, and focuses on particular aspects of a process. Nevertheless, much could be gained by sharing information among process-centered applications. One of the primary obstacles to such integration is the lack of a common representation the underlying concepts of process. The objective of the project described here is an investigation of the feasibility of a unifying specification of process that is applicable to multiple applications, yet powerful and robust enough to meet each set of requirements. This paper represents the results of the first phase of the project — that of researching the process representational requirements for design/manufacturing process life-cycle applications.

This paper presents an overview of hint-based feature recognition algorithms. A hint is a piece of information that implies a feature’s existence. Geometric completion procedures start from the hint instances, perform extensive geometric reasoning and finally construct feature instances. This paper describes the IF 2 , F-Rex and FBMach systems, and shows that the hint-based reasoning can deal with complex feature intersections.

Most of a product’s life-cycle characteristics are determined during the configuration design stage, when the product’s components are selected and arranged spatially and logically. One set of choices that determines many life-cycle characteristics is fastener type selection. In this paper, an assembly modeling representation is presented that supports changes in fastener types and fastening mechanisms while maintaining consistent degrees-of-freedom among fastened components. A fastening mechanism template and a corresponding instantiation algorithm have been developed for tensile-compressive fasteners. The template consists of four main elements: an assembly representation template, CSG tree fragments (to allow geometry construction), geometric constraint templates, and a parametric relationship template to integrate analysis equations into fastener models. Each particular fastener type is modeled by a specific template that is developed manually using the general template as a guide. The instantiation algorithm maps a particular fastening template onto an existing assembly model (assemblies, components, geometry, and mating relationships) in order to add fasteners to a product. A similar fastener substitution algorithm enables the replacement of one fastener type with another. The use of the algorithms is illustrated in the configuration design of an automotive center console. The paper concludes with a brief demonstration of how fastener selection affects life-cycle product characteristics.

Flashover is characterized by the rapid transition in fire behavior from localized burning of fuel to the involvement of all combustibles in the enclosure. The objective of the present contribution is to calculate the development of flashover in a typical single room fire, and show the effect of ten key parameters on the time required to reach flashover conditions. It is found that the major parameters affecting flashover are fire growth rate, ventilation opening area, and room area.