Design process and the iterative design cycle
Design process and the iterative design cycle is examined through questions on briefs, research, specifications, prototyping, testing and evaluation, and on how feedback loops change earlier decisions.
Core rules
- A brief states the problem and intended user; a specification turns it into measurable criteria (dimensions, mass, cost, safety, function).
- Research may be primary (interviews, questionnaires, anthropometric measurement) or secondary (standards, existing products, material data).
- The cycle is iterative: test results feed back into the specification or concept, so several loops are normal.
- Divergent thinking creates options; convergent thinking selects and refines.
- Evaluation must refer back to the specification, not to personal taste.
Worked example
A school asks for a reusable water bottle for students aged 11-16. The brief names the user and problem. Research finds bags are 22 cm wide and students dislike bottles that leak. The specification sets capacity 500 ml +/-25 ml, mass under 150 g empty, leak-proof when inverted for 10 minutes, drop height 1.2 m, cost under GBP 6, and recyclable body. A first prototype fails the drop test at the cap; the team changes to a threaded cap with a silicone seal, retests and passes. The evaluation records the failure and the change, showing iteration.
Traps
Writing a specification as adjectives ("light", "strong") instead of numbers; mixing brief and specification; pretending the process is linear; ignoring user evidence when evaluating.