Feature technology - an overview

Manufacture is an objective that has become more urgent within the wider context of a total Computer Integrated Manufacturing environment. In seeking this integration it is recognised that the diversity of activities and consequent needs for data can best be served by a single representation for design, design analysis and manufacturing planning, and that a strong candidate for this descriptive role is a Feature Representation. This paper briefly overviews the primary methods of the use of features through Feature Recognition and Design by Features, particularly in the process planning application area

Feature technology : an overview

The proper integration of the activities of computer-aided design (CAD) and computer-aided manufacture (CAM)is an objective that has become more urgent within the wider context of a total computer integrated manufacturing (CIM) environment. In seeking this integration it is recognized that the diversity of activities and consequent needs for data can best be served by a single representation for design, design analysis and manufacturing planning, and that a strong candidate for this descriptive role is a feature representation. This paper briefly overviews the primary methods of the use of features through feature recognition and design by features, particularly in the process planning application area

Process capability modelling: a review report of feature representation methodologies

Approximately 150 technical papers on the features methodology have been carefully studied and some selected papers have been commented upon. The abstracts of the comments are documented and attached to this report. The methodologies reviewed are mainly divided into two approaches, ie. feature recognition and design by features. Papers which deal with some specific topics such as feature taxonomies, dimensions and tolerances, feature concepts, etc. are also included in the document

Implementation aspects of a feature-based design system for manufacturing planning

A prototype feature-based design system for process planning is described. The system contains a design by features user interface which is developed within a Boundary Representation modeller; a feature modeller for manipulation of feature data; and an information mapper (feature processor) to transform design information into a form suitable for the planning system. In principle, the design system can be tailored for applications other than process planning by the use of alternative information mapping mechanisms. Emphasis is given to the software implementation aspects of the feature-based design system, such as the design and implementation of the user interface, the arrangement of the additional feature modelling functions together with standard solid modelling functions, the communication mechanism between different data models, and the tools used for the implementation

Feature validation in a feature-based design system

The Loughborough University of Technology Feature-Based Design System (LUTFBDS) allows detail design to be carried out in a computer aided design (CAD) environment by the addition of form features to stock material or part-machined components. An iconic user interface assists in the description parts in terms of a set of primitive features such as holes, pockets and slots or higher level compound features such as patterns of holes and counterbored holes. This feature representation is generated in parallel with the geometric data structure of the underlying boundary representation solid modeller. The feature representation is useful for a range of downstream manufacturing activities, but our research focusses on the integration of CAD with process planning. LUT-FBDS functions allows the designer or manufacturing engineer to progressively construct the final geometry of a part, and facilities are provided for the designer to modify parameters which relate to feature dimensions, location, orientation and relationships with other features. These changes may result in changes to the feature representation and hence there is a need for feature validation to ensure the integrity of the model

Knowledge representation and re-use in FMEA

The research described in this paper addresses the ability rapidly and easily to create product variants through the capture and re-use of design and manufacturing knowledge. New methodologies are envisaged that enable companies to anticipate problems before they occur, thus transferring them from ‘reactive’ to ‘predictive’. The implementation of predictive design represents the crucial move from standard parts to standard knowledge constructs. Standard parts can be used in any application that requires a defined function where the shape and properties do not need to be altered. However, standard knowledge constructs can provide parts that can be used wherever the function is required. Examples of the technique are presented from recently completed research concerning FMEA applied to electronic products

Geometric elements for tolerance definition in feature-based product models

Product modelling is an essential part of all computerised design and manufacturing activities. A precise mathematical model of the geometry of products is important, but must be supplemented with technological information such as the material, mechanical properties, functional specifications and tolerances. Modern CAD systems can model and manipulate components with complex geometry. However, technological information is represented as text symbols on the computer screen or drawing, and subsequent application programs are frequently unable to use this information effectively. This paper discusses this problem, and establishes the geometric elements required for the representation or dimensions and tolerances in a feature-based product modelling environment

A design by features approach to the building of feature data models for process planning

As research and development in Computer Aided Design and Manufacture (CAD/CAM) progresses, the integration of activities such as design, analysis, process planning, assembly planning, production planning becomes ever more complex and important. It has been recognized that a feature based representation of parts is a key to solving this problem. Unfortunately, neither has a feature representation scheme (or standard) yet been generally accepted, nor has a CAD system successfully represented feature information. Ongoing research into process capability modelling is aimed at solving the above problems in the process planning domain. In this paper, a design by features system, which consists of a design by features user interface and an integrated Boundary Representation solid modeller, is introduced. A feature representation scheme that has been implemented in the system is also presented. Although the design by features approach still has limitations, it overcomes some severe problems with the alternative feature recognition approach, such as the complexity of the recognition process, the limited number of features that can be identified from the geometric representations of pans and the absence of the designer's intent

The implementation of a feature-based component representation for CAD/CAM integration

Recent research and development has the objective of increasing productivity and cost effectiveness by integrating many activities such as design, analysis, process planning, assembly planning and production planning which encompass the entire manufacturing planning and operational control aspects of a manufacturing enterprise. It has been recognized that a key to the integration lies in the determination of a representation scheme for products that can be interpreted for the various needs of these different applications. Geometric (solid) modellers were regarded by many researchers as the appropriate representation, but more recently a features approach has been proposed to enhance the capabilities of solid modellers. This paper introduces ongoing research which is aimed at the development of a feature-based design system for process planning. The system is fully integrated with a conventional boundary representation (Brep) modeller which enhances its modelling capabilities in representing, editing and validating features of components. The main aspects of the feature-based design system are described in detail, such as the feature library, feature taxonomy, feature operations, feature relationships and tolerances. The generation of a detailed data model for transmission to manufacturing planning activities is also described and demonstrated by reference to an example component. A brief indication is given of our parallel research work in using such models as the basis of process planning and process capability modelling

An experimental comparison of a feature based design system and a conventional solid modeller

Computer-Aided Design (CAD) systems are currently widely used in design and manufacturing industries. However, the integration of CAD systems with Computer- Aided Manufacturing (CAM) systems such as process planning, graphical numerical control (NC part programming), assembly and inspection planning requires a featurebased representation of components which is not found in conventional geometry-based CAD systems. To meet this requirement, feature-based CAD systems have been developed in research centres worldwide using feature-oriented user interfaces and feature-based representations of parts. The introduction of new technology (feature-based design in this instance) always raises important questions. For example, are feature-based systems easier to learn and more efficient than conventional geometric modellers?; and does the method generate more complete and accurate models? This paper reports an experiment which was carried out to compare a prototype feature-based design system with a conventional solid modeller, where both systems use an iconic interface. Eight engineering students were selected as subjects and each subject was required to generate six features using both systems. The time taken to generate each feature was recorded and the results were presented as a series of graphs and learning curves. The results of the experiment show that both systems are similar in terms of learning their operation and that the feature's approach has clear efficiency gains over the conventional geometric approach. The conclusions drawn from this experiment may be useful for both end users who are considering upgrading their existing systems and software vendors who are designing next generation of products