What is a prototype?
A prototype is an early model of an idea, made so it can be tested before the final product is made. It answers questions: Does it fit? Is it easy to use? Is it strong enough? Do people want it?
Prototypes are used for objects (a chair, a bottle), digital products (an app screen), services (a new canteen queue) and even business models (a small trial before a full launch).
Fidelity: how close to the real thing
- Low fidelity: sketches, paper, cardboard, clay, foam. Fast and cheap. Good for early ideas and size.
- Medium fidelity: 3D prints, laser-cut parts, simple electronics. Shape and fit are exact.
- High fidelity: looks and works almost like the final product, in real materials.
Rule of thumb: use the cheapest prototype that can answer your question.
Types of prototypes
- Sketch model / mock-up: a rough 3D model to see size and form.
- Appearance model (looks-like): shows colour, finish and look, but may not work.
- Functional prototype (works-like): works, but may look rough.
- Digital prototype: a CAD model or app mock-up tested on screen, sometimes with simulation of strength or movement.
- Pre-production prototype: the final check before making many.
- Service or business prototype: a role-play, a storyboard, a small pilot with real users, or a simple landing page to see if people are interested.
Rapid prototyping methods
Rapid prototyping means making a physical model quickly, usually from a CAD file, with computer-controlled machines.
- 3D printing (additive): melts plastic and lays it down one thin layer (often 0.1–0.3 mm) at a time. Good for complex shapes. Slow for big parts.
- Laser cutting (subtractive): a laser cuts flat sheets of card, wood or acrylic. Very fast for flat parts that slot together.
- CNC milling (subtractive): a spinning cutter carves a solid block. Strong parts in real materials such as wood or aluminium.
- Hand methods: card, foam, clay, wire, hot glue. Often the fastest of all.
Additive manufacturing adds material only where needed, so there is little waste. Subtractive manufacturing starts with more material and removes some, which wastes more but can give stronger, smoother parts.
Workshop safety
Wear safety glasses, tie back hair, never leave a laser cutter running unwatched, let 3D-printed parts and nozzles cool, and use tools only after training.
Experiments and tests
A prototype is only useful if you test it properly.
- Question: what do you want to find out? ("Can the stool hold 100 kg?")
- Criteria: what counts as a pass? Take it from the design specification.
- Fair method: change one thing at a time, repeat tests, measure with instruments (scales, timers, rulers).
- Record: tables, photos, videos, user comments.
- Conclude: pass or fail, and why. What should change?
Two kinds of test: technical tests (strength, temperature, battery life) and user tests (watch real people use it; do not explain, just observe where they struggle).
Iterate, then present the project
Iteration means going round the loop again: build → test → learn → improve. Each round gives a new version (v1, v2, v3). A failure in testing is useful: it shows exactly what to fix.
When the design is ready, formalise and present it:
- a final model or prototype,
- technical drawings or a CAD file with sizes in millimetres,
- a list of materials and costs,
- the test results and the changes they led to,
- a short pitch: the problem, the user, the solution, the evidence.
Try it
Make a paper or card prototype of a phone stand in 15 minutes. Test: does it hold the phone at a good angle when you tap the screen? Change one thing, test again, and write v1 and v2 results in a small table.
Key formulas and definitions
- Prototype: an early, testable version of an idea
- Fidelity: how close a prototype is to the final product (low → high)
- Looks-like vs works-like prototype
- Rapid prototyping: quick physical models from CAD using machines
- Additive: adds material layer by layer (3D printing)
- Subtractive: removes material from a block or sheet (laser cutting, CNC)
- Print time ≈ number of layers × time per layer; layers = height ÷ layer height
- Iteration loop: Build → Test → Learn → Improve
Worked examples
1. A part is 30 mm tall and printed with 0.2 mm layers. Each layer takes 40 s. Estimate the print time.
Layers = 30 ÷ 0.2 = 150. Time = 150 × 40 s = 6000 s = 100 minutes, about 1 h 40 min.
2. A team wants to know if their new water-bottle handle fits small and large hands. Which prototype should they make first?
A low-fidelity foam or card handle (looks-like / feels-like). It takes minutes, costs almost nothing and answers the question about size and grip. No need for a working bottle yet.
3. Version 1 of a stool bends at 60 kg. The specification says 100 kg. What next?
Record the result (fail at 60 kg, front leg bent). Learn: the leg is too thin. Improve: thicker legs or a cross-brace. Build v2 and repeat the same test, adding weight in the same steps, until it passes 100 kg with a safety margin.
4. A start-up wants to sell a meal-planning app. How can it prototype the business idea before writing code?
Make paper or clickable screen mock-ups and test them with 5–10 users; build a simple web page describing the app and see how many people sign up. This tests whether people want it before spending money.
Common mistakes
- Making a high-fidelity prototype too early. Start cheap and simple.
- Testing without a clear question or pass criteria.
- Changing several things at once, so you cannot tell what made the difference.
- Seeing a failed test as a disaster. A failed prototype is information that saves money later.