10 research outputs found
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
Process capability models for equipment selection
Due to the increased complexity of modern manufacturing facilities
and the increased demands for product variability and system flexibility there is
a need for coherent formal representation of the basic knowledge domains
supporting manufacturing applications such as equipment selection. The paper
presents integrated framework for equipment selection based upon
describing process capability at generic, machine tool and manufacturing
system levels. The decision making process is designed as a sequence of steps
for transforming component design information into processing requirements
which are mapped into specific physical machines organised as
a processing system
Component grouping for GT applications - a fuzzy clustering approach with validity measure
The variety of the currently available component grouping methodologies and
algorithms provide a good theoretical basis for implementing GT principles in
cellular manufacturing environments. However, the practical application of the
grouping approaches can be further enhanced through extensions to the widely used
grouping algorithms and the development of criteria for partitioning components
into an 'optimum' number of groups. Extensions to the fuzzy clustering algorithm
and a definition of a new validity measure are proposed in this paper. These
are aimed at improving the practical applicability of the fuzzy clustering
approach for family formation in cellular manufacturing environments. Component
partitioning is based upon assessing the compactness of components within a group
and overlapping between the component groups. The developed grouping
methodology is experimentally demonstrated using an industrial case study and
several well known component grouping examples from the published literature
Component grouping for cell formation using resource elements
The work reported in this paper recognises that the traditional close association between components and a fixed route utilising a set of machine tools can no longer be relied upon as an appropriate basis for deciding component similarity and partitioning components into families in modern manufacturing applications. A new methodology for describing the capabilities of machine tools and machining facilities using generic capability units termed 'resource elements' is reported. REs are used to capture the processing requirements of components, assessing their similarity and a fuzzy grouping procedure is used for simultaneously grouping components and machine tools for cellular manufacturing applications. The reported results show that the use of resource elements leads to component groups that are more compact with better matching between processing requirements of components and the capabilities of the machine tools selected for their processing compared with the conventional machine-based approach
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 survey of virtual prototyping techniques for mechanical product development
Repeated, efficient, and extensive use of prototypes is a vital activity that can make the difference between successful and unsuccessful entry of new products into the competitive world market. In this respect, physical prototyping can prove to be very lengthy and expensive, especially if modifications resulting from design reviews involve tool redesign. The availability and affordability of advanced computer technology has paved the way for increasing utilization of prototypes that are digital and created in computer-based environments, i.e. they are virtual as opposed to being physical. The technology for using virtual prototypes was pioneered and adopted initially by large automotive and aerospace industries. Small-to-medium enterprises (SMEs) in the manufacturing industry also need to take virtual prototyping (VP) technology more seriously in order to exploit the benefits. VP is becoming very advanced and may eventually dominate the product development process. However, physical prototypes will still be required for the near future, albeit less frequently. This paper presents a general survey of the available VP techniques and highlights some of the most important developments and research issues while providing sources for further reference. The purpose of the paper is to provide potential SME users with a broad picture of the field of VP and to identify issues and information relevant to the deployment and implementation of VP technology
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
Process capability modelling for design and selection of processing equipment
Due to the increased complexity of modem manufacturing facilities and the increased
demands for product variability and system flexibility there is a need for coherent formal
representation of the basic knowledge domains supporting manufacturing applications
such as equipment selection. The paper presents an integrated framework for equipment
selection based upon describing process capability at generic, machine tool and
manufacturing system levels. The decision making process is designed as a sequence of steps
for transforming component design information into processing requirements which are
mapped into specific physical machines organised as a processing system