Proactive DFA
An interactive tool to perform evaluation and offer advice to
the designer.
General Overview
Previous work on the ‘Ophir’ project integrated DFA within a CAD system
to reduce the amount of user input and eliminate subjectivity,
highlighting design problems before a design enters production and
prompting re-design by the designer. However, this research has
shown that traditional DFA is best suited to complete designs,
since much of the analysis is dependent upon component geometry.
DFA is therefore currently considered as a reactive tool and is
only applicable on completion of the design when it is often too
late to make significant changes.
In order to improve the effectiveness of DFA so that it is useful
in an assembly-oriented design environment a proactive, rather than
reactive, approach is required. This approach enables a 'right
first time' design with minimal additional effort, so that
subsequent changes are not required. Thus, it is important that the
DFA evaluation becomes a fundamental part of the design process,
occurring simultaneously with other design activities so that
designers may optimise design in line with DFA recommendations. The
notion of 'Proactive DFA' is aimed at providing the designer with
the necessary tools for design evaluation at the earliest stages of
the design and development process and thus ultimately, reducing
lead times for product introduction. In order to integrate
Proactive DFA into all stages of design development three levels of
operation have been proposed Product Group, Product Structure and
Component Design as shown in Figure 01 below.
Figure 01. Elements of a Proactive DFA Methodology (Click image to
enlarge)
Product Group Support
Product Group Support aims to help the designer to identify
possibilities for establishing product family themes at the
commencement of product design and development. By identifying
common features and similarities with existing products it provides
the opportunity for rationalisation and standardisation of parts
and assembly operations. It is essential that the use of any
standard components and features be based on a satisfactory DFA
history. It is proposed that DFA experience and case histories form
the core of the Product Group support to encourage the designer to
use common technologies, common assembly features and joining
methods, and common parts and modules.
Product Structure Support
In order to capture the essence of
assembly oriented design it is crucial to allow the designer to
evaluate alternative product structures and assembly sequences. The
proposed Proactive DFA methodology incorporates a simple
interactive method for analysing assembly sequences and the
necessary tools for considering geometric and assembly constraints
during the evaluation process. An essential aspect of generating a
successful product structure and assembly sequence is to optimise
the part count. In order to do this the functional requirements of
individual components must be assessed so that component clusters
may be replaced with single integrated pieces. In order to assist
the designer, information should be provided containing relevant
data such as process descriptions, material suitability and design
considerations.
Component Design Support
The final stage of the proposed proactive
DFA methodology provides assistance to the designer for detailed
component design. In order to help the designer to generate designs
that are suitable for manufacture and assembly, advice on assembly
insertion and fastening processes is required. Process capability
data and cost models for other assembly and manufacturing processes
are also necessary. This information provides the designer with the
capability to evaluate the effects of design decisions on cost and
practicality of manufacture. To ensure that cost models are
appropriate for each working environment the system should allow
users to customise the data.
In summary, the Proactive DFA methodology described above defines
an interactive tool to perform evaluation and offer advice to the
designer throughout product development, with varying levels of
detail and support. The system would allow utilisation of
traditional DFA capabilities whilst removing many of the drawbacks.
By incorporating new or modified analyses it would enable design
optimisation decisions to be made prior to the complete definition
of component geometry, and thereby Proactive DFA would be able to
support the design process from the earliest stages.