Design specification

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What Is a Design Specification?

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The Design Specification consists of a number of requirements. The design of a product is ‘good’ in so far as it complies with the stated requirements. A requirement is an objective that any design alternative must meet. The programme of requirements is thus a list of objectives, or goals. Goals are images of intended situations, and consequently requirements are statements about the intended situations of the design alternative.

<toggledisplay showtext="Show an example of a partial Design Specification" hidetext="Hide example" linkstyle="margin-left: 25px; color: #9900BB;">

2. Distribution:

  • 2.01 The electrical home scissors should be efficiently transported from producer to wholesale and/or small shops
  • 2.02 The electrical home scissors be efficiently transported from wholesale or small shops to the consumer
  • 2.03 The product may not be damaged during transportation and storage
  • 2.04 The packaged product needs to be stackable
  • 2.05 The displayed product should clearly communicate its function and possibilities

3. Use:

  • 3.01 The product can be carried and hand-held
  • 3.02 The electrical home scissors have to be ready for use in 1minute, preferably without use of any extra tool
  • 3.03 The method of assembly of parts needs to be clear
  • 3.04 The use of the electrical home scissors needs to be clear
  • 3.05 Possible use restrictions of the electrical home scissors need to be clear
  • 3.06 The operation of the product needs to be clear
  • 3.07 The product needs to be operated standing and seated.
  • 3.08 The product needs to be able to be used with one hand left and right handed
  • 3.09 The product needs to resist a fall of 0.8m
  • 3.10 The product may not damage the environment in which the product will be used
  • 3.11 The product has to be designed in such a way that it will not harm users
  • 3.12 The electrical home scissors need to be able to be cleaned with a wet tissue
  • 3.13 Adjustments should be done by the user
  • 3.14 The electrical home scissors need to be able to be repaired at a repair service

Design alternatives should comply optimally with the requirements; an alternative which does not comply with one or more of the requirements is a bad alternative and cannot be chosen. Many requirements are specific; they apply to a particular product, a specific use, and a specific group of users. There are also requirements with a wider scope, as they are the result of an agreement within a certain branch of industry or an area of activity. Such a requirement is called a standard. To some extent, a designer is free to choose requirements; standards, however, are imposed by an external authority.

When Can You Make a Design Specification?

Normally, a design specification is constructed during the problem analysis, the result being some finished list of requirements. However, a design specification is never really complete. During a design project, even during the conceptual designing stages, new requirements are frequently found because of some new perspective on the design problem. Therefore, a design specification should be constantly updated and changed.

How to make a design specification?


Starting points

The starting points for making a design specification are the analyses that take place during the stage of problem analysis.

Expected outcome

The outcome is a structured list of requirements and standards. Programmes consisting of 40 or 50 requirements are not un­common.

Possible procedure

  1. List as many requirements as possible. Roozenburg and Eekels state that to arrive at a complete design specification, different points of view can be taken into account. Choose one, or several, of these points of views (stakeholders, aspects, or process tree) to help generate requirements. You can also use a checklist, for example by Pugh.
  2. Make a distinction between hard and soft requirements (between hard requirements, which are quantifiable, and wishes).
  3. Eliminate requirements which are in fact similar or who do not discrimate between design alternatives.
  4. Identify whether there is a hierarchy between requirements. Divide between lower-level and higher-level require­ments.
  5. Operationalize requirements: determine the variables of requirements in terms of observable or quantifiable characteristics.
  6. Make sure that the programme of requirements fulfills the following conditions:
    1. Each requirement must be valid.
    2. The set of requirements must be as complete as possible.
    3. The requirements must be operational.
    4. The set of requirements must be non-redundant.
    5. That the set of requirements must be concise.
    6. The requirements must be practicable.

Tips and concerns

  • Be careful: do not make the possibilities for your design too limited by defining too many requirements.
  • Distinguish between measurable requirements and non-measurable requirements.
  • Give your requirements numbers in order to be able to refer to them.

References and Further Reading

  • Roozenburg, N.F.M. and Eekels, J. (1995) Product Design: Fundamentals and Methods, Utrecht: Lemma.
  • Roozenburg, N. and Eekels, J. (1998, 2nd ed.) Product Ontwerpen: Structuur en Methoden, Utrecht: Lemma.
  • Cross, N. (1989) Engineering Design Methods, Chichester: Wiley.

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