Iterative design

The iterative process in design

Designing a product for a client can be done in several ways. Manufacturers cannot risk investing large amounts of money into the production of a product that has not had adequate design, modelling, testing, prototyping and evaluation.

Iterative design is a circular design process that models, evaluates and improves designs based on the results of testing.

Diagram illustrating the cyclic iterative design process starting with a brief, to analysis, design ideas, modelling, testing, evaluating and modification.


Starting with a design brief a designer may come up with a good idea that solves a problem. Using an iterative design process, a model can be made from a design sketch and then tested. The test results may suggest failures and modifications to the design. These changes are evaluated, and then the cycle begins again - until the best solution to the problem is found.

Sketching design ideas

This involves creating a series of freehand sketches of design ideas that may help solve the problem in the design brief. These could be different from each other or developments of an original idea.

Sketched design ideas of headphones. Includes rough sketches of the various components and a polished colour drawing.


Modelling ideas in card, paper, clay or other materials can create a cheap and quick way to do initial trials with a product. Using an easy to modify material provides a good way of seeing how a product looks and works, eg checking handles are in the right place or parts fit together well. Taking photographs or video throughout this can show development.


Once a model has been made it can be tested in a variety of ways:

  • destructive testing - tests the product to its extreme to see what conditions it can tolerate before being destroyed, to help decide on the best materials and construction methods to use
  • non-destructive testing - tests the model to identify areas of weakness without destroying it, to test the function of the product and highlight any unexpected design flaws
  • market testing - tests the product with its target market to give feedback on performance and design


The data that is gathered from the testing of a model can be in the form of questions answered or tables of measurements or results. These can then be analysed and used to improve aspects such as:

Evaluation is crucial in the design process as it can highlight any modifications that need to be made at the next stage. It is also a valuable point at which to consider the product against the original design specification and ensure the client or target market’s needs are met.


From the evaluation, a designer can revisit the models and design ideas to make improvements to:

  • performance
  • style
  • function
  • cost

Becoming fixated on a particular idea can become an issue when trying to develop a new solution to a design problem. This can be avoided by: