Most rapid prototyping systems electronically divide a 3D CAD model of the part into thin horizontal cross-sections and then transform the design, layer by layer, into a physical model. Rapid prototyping (and tooling) techniques are increasingly being used during the product development cycle. For instance, Ford Motor Company uses stereolithography as an integral part of concurrent product and process design. Developing new automobile components is expensive, traditionally requiring many design iterations and significant schedule time. Stereolithography allows the production of models of the part in a single day, using the same CAD data needed for structural analysis, kinematic studies, NC programming, etc. An example of the use of this technology occurred when Ford sought a supplier for a newly designed internal combustion engine rocker arm. When different suppliers had difficulties in interpreting the 2D drawings of the rocker arm, Ford turned to stereolithography to produce a model of the part in one day. When the model was made available to bidders, Ford received a quote that saved up to 3 million US$ annually in production costs.

Although rapid prototyping and tooling technologies are evolving at great speed, there are of course still limitations as to their use. These include limitations due to the use of rapid proto-type materials different from those specified for the part being designed, restrictions on the number and variety of test conditions that can be applied to the prototype, and difficulty in using test data from the prototype in performing Finite Element Analysis. In addition, even if the tools are available, my own research shows that it takes some time and change of mindset before designers and engineers are able to make the switch to the new design approach. Training and developing familiarity with the new tools is crucial. However, even when training and guidance are provided, it takes time before the tools are being used in an effective and an efficient manner. Moreover, it is obvious that the introduction of those design tools may have a quite disruptive impact on the ‘established’ design expertise and experience at the company. As a consequence, ‘Not Invented Here’ syndromes and resistance to change phenomena may well occur and may thus put a strain on the deployment of the new tools and techniques.

To conclude this brief overview, virtual prototyping is a term that describes the computer analysis and testing of CAD models before the commitment is made to produce the physical prototype. In virtual prototyping the CAD model is evaluated by iterative dynamic simulation before making the physical model. This technique allows testing of the model under various kinematic and dynamic conditions that would be expensive and complex to duplicate in the laboratory.
These last reflections suggest that the use of virtual and physical prototyping should be intertwined and integrated. Prototyping strategies aim at using virtual and physical prototyping in an intermittent and iterative manner in order to arrive at an intelligent experimental program. In this way, the organisation of the design process becomes a rapid sequence of design-build-test-redesign cycles. The ‘build’ phase of the cycle then uses the prototyping approach that offers most added value in terms of design changes and improvements (or for that matter, elimination of design errors) at any moment during the design process.

This puts a strain on ‘traditional’ phased project planning approaches as it almost becomes impossible to have detailed milestone planning and reviews in such a fast prototype design and change cycle approach. In other words, the ‘traditional’ (phased and planned) project organisation format is being replaced (or complemented?) by a more adaptive approach. This adaptive approach allows for a quick sequence of experimentation and analysis cycles, as extensively described in the previous sections of this contribution. Eisenhardt and Tabrizi (1995) coined this organisational approach as ‘experiential project structures.’

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Design Management
VIZO Workshop

“Design makes the Difference”
Brussels, Belgium - 29/30 November 2002

 
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