Civil Engineering Reference
In-Depth Information
4.5
Computer-Aided Design and Manufacture
of Injection Forging
The design activity is responsible not only for the performance and appearance of the product but also
for the cost of the component. Design, therefore, cannot be an isolated activity but must address all
available manufacturing routes, with a view to optimizing the quality and cost of the component. With
reference to nett-forming, the design exercise is conducted not only to specify the component-form but
also to address all manufacturing constraints—machine, material, tooling, and processing conditions.
Computer-aided “design for manufacture” is currently the main form of implementing of the “con-
current engineering.” To enable this, CAD/CAM is popularly used as a design approach. Using CAD/CAM
approaches, simultaneous design would be effected efficiently by supporting the designer with informa-
tion on all possible resources required for the design and manufacture of components. Some CAD/CAM
systems [42] have demonstrated the potential for the development into decision-support systems for
component/tool design.
Computer-aided design and manufacture for nett-forming by injection forging is being developed as
an aspect of research associated with the development of a decision-support system [64].
Methodology
In order to develop a decision-support system for component/tool design using a CAD/CAM approach,
several design/evaluation methods have been developed [58, 60, 64-68]. These are described briefly in
the following texts.
Geometric Modeling
The popular strategy used for the development of the design-support systems for forging was to evolve
a 2D-CAD system for component and tool design. The system was linked to a knowledge-based system
to enable the evaluation of manufacturability. Subsequent to the evaluation of the geometry, the com-
ponent was transferred to a CAD software to enable detailed design. This approach required the design
to operate in several software environments. An integrated system, supported by solid modeling, would
enable design and assessment of a component more efficiently. A solid modeling-approach—principal
feature modeling—was used to enable component-design for forging within a solid modeling environ-
ment [65, 66]; the approach enables integration of currently available 2D-based knowledge-based systems.
Design for manufacture requires that the component form is specified in a modular form in order to
enable the evaluation of the design. The component may be defined as a combination of primitive forms
as is the case in “design by features;” alternatively, the primitive forms which constitute the component may
be extracted and identified automatically. Unfortunately, both these approaches are currently at a stage of
refinement which only allows their applications to a limited range of component forms. Principal feature
modeling [67] combines the strategies of both “design by feature” and “feature recognition” to enable
efficient modeling and feature manipulation; the approach was proven to be particularly efficient for the
modeling of forging/machining components [65]. Designing is attended to with reference to a prescribed
set of performance requirements rather than to prescribed form features. The principal features, which
represent the principal geometric profiles of a component, may be defined by the designer using arbitrary
geometry—a group of curves on a plane or a curved surface. The principal features which have been
generated are linked, exclusively, to a set of prescribed attributes which are catalogued in a database.
The solid model of the component may be created by geometric manipulation of a principal feature;
several principal features may be defined for more complex components. Subsequent to the definition
of the principal features for a particular component; local features may be added to produce the first
iteration of the “performance” model of the component. The form of the additional features is generated
by the modification of the principal geometric entities; these additional features are extracted and
classified as individual manufacturing features. In circumstances where components cannot be modeled by
defining principal features, the model can be created by other approaches. This will enable the prescription
