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Engineering and Design Tools - TSOC 306 and TSOC 305 |
It is widely believed that 70 - 80% of the product cost is fixed at the conceptual design phase. With costs being increasingly important in competitive markets, product development strategies and tools are addressing this aspect.
Benefits of improving the conceptual design phase include:
The SDFM was developed at Stanford University by Professor Phil Barkan with the support of General Motors in the late 1980s. This is now available as a course and is used by many companies including Boeing.
The SDFM methodology considers conceptual design as a four phase process:
Looking at each of these:
Phase I: Problem Formulation
This is to establish the basis for the design and involves using methods to
frame the problem. A careful approach to this requires discipline as there are
often schedule pressures to get on and develop a particular concept quickly.
Failure to assess a wide range of concepts is likely to result in late development
of a poor product.
At this stage the team need to gather all the information, eg requirements, restrictions, before generating concepts. Techniques and tools that may be used will include the following:
Phase II: New Product Vision
At this stage measurable goals must be established, this involves distilling the results from the
problem formulation phase into a product specification and identifying critical issues in
producing a world class product. Issues such as cost, life cycle, performance and reliability
should be addressed in this phase.
Phase III: Concept Generation
The team should generate as many concepts as possible, this will almost certainly
involve one or more brainstorming sessions. Each concept should be documented in a common,
simple format.
Initialising concepts on a large complex project can be difficult, the SDFM process
simplifies this with the following procedure:
Phase IV: Concept Selection
The team uses the Pugh selection method (based on an evaluation matrix that compares each
concept to a datum configuration) to select the best alternatives. In some cases one concept
may be better than the other, but often there will be a number of concepts worthy of
further investigation.
By using this process new concepts may be developed by taking features from from several
concepts and integrating them for a better product.
Rapid prototyping may be used at this stage to aid validation, visualisation and rapid
identification of potential problems.
Further evaluation and refinement may follow. Obviously this work must be carefully
documented so areas needing further work and areas of risk are noted.
Detail Design
After the best concept has been identified the phases remaining can be described as: detail design,
design validation, production and product support.
The detail design phase involves optimising the design, simulation and analysis,
selection and specification of materials and manufacturing processes. Whereas the Concept
stage works well with only a small team, the detail design stage normally
involves a much larger number of people working on the project.
Design Validation
This stage typically involves prototype, system and materials testing to verify design predictions and
service life. To ensure a robust product, all queries raised during earlier phases of the
design must be resolved. Carefully thought out testing can ensure that the product is robust
and minimises the risk of customer problems with the new product.
Once a product has entered the market place, modifications, whether to enhance performance
or overcome problems, need to be carefully planned to ensure changes to effect improvements
are not accompanied by a downside.
Reports from leading manufacturers, such as Boeing, indicate that the SDFM reduces product development cycle time by investing time and effort into the initial problem formulation phase. This gives a clearer direction and results in a better product.
Reference:
M3 'Design for Manufacturability 1995', Ed. J R Behun, ASME, DE-Vol. 81, 1995.
David J Grieve, 11th July 2003.