Iterative Design and Prototyping
Develop a design through repeated cycles: build a model or prototype, test it against criteria, record the results, and use the evidence to choose changes. Retest to find whether a change helps and what still needs work.
What a learner can do afterwards
- Build a rough prototype or model to test an idea before making a final version
- Test a prototype against criteria, record the results, and identify the main weakness (e.g. 'the bridge failed at the joints, not the beams')
- Explain how each version changed and what test evidence prompted the change
1 · Read
A prototype is a model made to test a design idea before the final product. It may test just one feature. Use the criteria from your brief: what must the design do, and what limits must it meet? Iterative design means building, testing, learning from results, changing the design and testing again. A change may help, do nothing or create another problem.
Zara's bridge model held 2 kg before its joints separated. Its beams stayed intact. She changed the joint method. With the same test setup, version two held 4 kg. The increase was 4 minus 2, or 2 kg. Changing one feature while keeping test conditions alike helps compare its effect. One result is evidence; repeat tests where practical.
Mass held in the same test, measured in kilograms.
Record the version, what changed, the evidence behind the change and the new test results. Observe where and when a problem happens. Investigate that part first, then choose a change supported by evidence. Several parts may need changing, or a new approach may be needed. Retesting checks whether the proposed fix helped. Finding a weak point alone does not prove the cause.
Choose a prototype that can answer your test question. A sketch can test layout, but testing a bag with books needs a physical model with suitable materials and joins. A cheap material may behave differently from the final one. Check other criteria after a change: a stronger design may cost or weigh more. Use adult-approved tools and safe tests for classroom models.
Build a suitable prototype, test against criteria, record the evidence, choose a change and retest. Check whether it helped and what still needs work.
Original lesson, questions and flashcards written for this dataset about prototyping, test evidence and design iteration.
Original readings and flashcards written for this dataset about prototype selection, test records and design decisions.
More to read
Keep evidence from each test
Give each prototype version a name or number. Before testing, record the question, the criterion and the measurement you will use. Agree a safe method with an adult.
Record what happened during the test, including where and when a problem appeared. Keep observations separate from possible explanations. A loose joint is an observation; unsuitable glue is one possible explanation to investigate.
Record the next change and why you chose it. Compare the new results using the same method where possible. If test conditions differ, note that difference. A result that does not improve still helps the team decide what to investigate next.
Choose what the model needs to show
Start with the question you need the prototype to answer. A drawing may help compare where pockets belong on a bag. It cannot test whether a seam will carry books.
A carrying test needs a physical model whose materials and joins suit that question. If they differ from the planned final materials, record the difference and limit what you conclude.
Prototype types do not have one fixed cost order. Tools, detail and time all affect cost. Choose a model that provides useful evidence without adding features the test does not need.
Check what a change achieves
A design change is a proposal to test. It may improve the result, leave it unchanged or introduce another difficulty.
Changing one feature can help identify its effect. Some problems involve connected parts, so several changes may be needed. Explain those decisions in the version record instead of treating one-change testing as a rule for every project.
Check the other criteria too. A stronger part may weigh more or cost more. Use the results to choose a further change, keep the version or try another approach. Finishing the current project does not mean that no later improvement is possible.
2 · Watch
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Where it sits
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Optional connections
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Where this leads
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8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.