Different kinds of design a classification

Once required functionality is established, a first preliminary design can be made. At first, the 'design' is no more than a rough sketch with a few specifications. In due course the design becomes more specific. As a corollary, there is no such thing as a frozen design. Modifications are and should be always possible, although the solution space for changes in the design will narrow down considerably once it comes to actually building.

It is useful to distinguish various phases in the design process according to the different parties that are involved. This leads to the following classification of design:

1. Conceptual design: preliminary sketches, main functional requirements.

2. Contractual design:contractual design bill of materials, specifications on sub-system performance.

3. Detailed design: construction drawings, specifications of sub-systems.

4. Design modifications during construction: corrective measures during construction.

Figure 1.1 Schematic pattern of thefrequency of engineering changes tends to show peaks whenever a new group gets involved (Van Gunsteren, 2003, p. 128)

5. Design modifications after commissioning: corrective measures after completion.

This classification is similar to the design phases of the development of a new industrial product (Fig. 1.1).

To achieve quality of design on a new industrial product, both available technologies and specific, or latent, wishes of end users must be incorporated into one integrated design of the new product. This requires effective communication with both the relevant scientific community and the end-users. Design changes inevitably occur whenever new players become involved.

Engineers engaged in Research and Development (R&D), by virtue of their technical background, tend to show a genuine interest in advancements in their field of expertise. However, they are usually not good listeners towards non-technical people, including end-users. They perceive the basic wishes of customers, often related to the user-friendliness of the product, as being straightforward, and not very challenging in the technical sense.

As a result, a great number of engineering changes has to be processed in order to make a product acceptable when launched onto the market. The same phenomenon can be observed when a product design is transferred to another group within a company, since these people can be seen as internal customers.

When the development of the conceptual design starts with a rough idea, a lot of modifications take place. The conceptual design is then transferred to the next group, which has to produce the prototype. Contrary to the expectations of the previous group, it then turns out that the product cannot be made within the cost limits dictated by the market.

Another round of modifications emerges before the prototype is completed.

Table 1.1 Involvement of players in different phases

Owner End user Financier Contractor

1. Conceptual design

• •

2. Contractual design

• • •

3. Detailed design

• • •

4. Design modifications during construction

• • •

5. Design modifications after commissioning •

The project is then transferred to a manufacturing group for production preparation, which in turn introduces another batch of engineering changes. Production of series differs fundamentally from making a single prototype, and these changes are necessary to make the product production-friendly. The project is finally transferred to marketing for introduction into the market. Again, a series of modifications has to be carried out to make the product acceptable to the ultimate customers.

Similarly, the number of design changes in a construction project tends to increase considerably at the beginning of each new phase of the process, when new players become involved (Table 1.1).

To summarise, the design process never ends, but its characteristics change over time. During later phases, design freedom becomes more limited, solution spaces become smaller, but not zero. In different phases other players -actually also designers - get involved.

The distinction between design and construction usually made in practice, is artificial. When projects become large and complex, this artificial separation of design and construction can have disastrous effects as paraphrased so convincingly in the fairytale of De Ridder's 'Granny's puzzle' (De Ridder, 1994, pp. IV-VI). See Appendix.

Design and construct, in our view, refers to one continuous process from initial idea to implementation. We see design and construct as narrowing down design solution spaces until actual implementation.

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