Civil Engineering Reference
In-Depth Information
by which decisions may be made relative to constraints will require manual interaction as the means of
designing with reference to performance constraints. The system is designed to enable easy access to the
data of the designed model so that the designer can extract the necessary information (geometric or
topological, point, line, face, or surface). Secondly, the system provides the standard subroutines by
which the designer can develop the required formulation to judge constraints, such as dimensional limits
of tools and positioning and interference analysis of tooling assembly. In addition, the module is also
designed to provide interfaces to enable the use of analytical approaches.
Detailed Design
—Before the detailed design of the manufacturing model is initiated, the features of the
model are classified automatically and interactively. The classification is manufacturing method-based,
i.e., for forging and machining, different classification strategies are used for defining manufacturing
models. Geometric features, which have been classified, are displayed individually on the screen to enable
definition of the manufacturing-related attributes.
The general requirements, such as the capacity of equipment, tool, and material, may be investigated
in the concept design. The available CAM facility for tool interference and fixing verification may be
used to test the finished tool-model; further detailed judgments of the manufacturability are conducted
for some local and individual features. At this stage, the required FE simulation of material flow, analysis
of tool deflection, and stress may be conducted. Further, the designer would also rely on machining
simulation to compare the cost-implication of tool manufacturing, which results from the addition of
features to the performance model. The precise shape, dimension, and tolerance of the designed tool-
model are finally specified for the manufacturing models.
Assessment of Design
—The accepted models, after detailed design, are a performance- and manufactur-
ing-proven component design. In other words, the design satisfies the conditions of both performance
and manufacturing constraints. Further assessment of the models is conducted using synthetic cost data;
the cost of each model, the results of the assessment, are delivered as design documents, some of which
may be recorded in a database of the system for reference in other designs, or used for adding and renewing
the design knowledge in the library.
System Development Considerations
At the primary stage of the development of the decision-support system for component/tool design, the
application concentrates mainly on the nett-forming by injection forging and machining for tool man-
ufacturing. The cost of operations within each technology is qualified prior to the development of software
to structure the decision-process, the system and each functional module.
Four major modules are planned; the simplified system-architecture is shown in
Fig. 4.23
.
The CAD/CAM
Module mainly includes basic CAD and CAM tools for component design; currently, ACIS [69] is chosen
as geometric engine to provide primary CAD/CAM tools. ACIS is a new-generation, three-dimensional,
boundary-representation, solid geometric modeler; it provides efficient functions and interfaces to enable
flexible manipulation of geometric entities and their attributes. General CAD or CAD/CAM commercial
packages are designed for direct application to design and manufacturing. ACIS, however, was designed
mainly for fundamental research purposes; it is, therefore, more able to support users in implementing
their own approaches and to develop application software. The Processing Module consists of the process-
related data, knowledge, and process simulation sub-modules; the Company-Specific Information Module
contains the company-specific information on design specifications, product, material, equipment, costing,
etc. The Operational Module is an assembly of a number of sub-modules which includes feature extraction
and attribute manipulation, pre-processing of the model, user-defined constraint analysis, component-form
error analysis, model-assessment and synthesis, and the preparation of design documents. The modules
may be individually and simultaneously operated through common interfaces and a central database system.
In the system, all data, both dynamic and static, will be retained in the several databases, each being
designed for a different functional purpose. Since the decision-support for component/tool design will
eventually be company-specific, the system is open for the designer to develop; the system provides
flexible interfaces. The user will, therefore, be provided with a shell.
