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Modelling allows designers to explore, test and refine ideas before committing to full manufacture. This lesson covers 2D and 3D modelling methods — both digital (CAD) and physical — as required by AQA GCSE Design and Technology (8552), Section 3.3. These are tested on Paper 2 and are essential skills for your NEA.
Modelling serves several purposes in the design process:
| Purpose | Explanation |
|---|---|
| Test form and proportion | Does the product look right? Is it the correct size? |
| Test function | Does the mechanism work? Do the parts fit together? |
| Communicate ideas | Show clients and stakeholders what the product will look like |
| Identify problems early | Discover issues before expensive tooling and manufacturing begin |
| Refine the design | Make changes quickly and cheaply on a model rather than a finished product |
Physical modelling involves creating tangible, three-dimensional representations of a design using materials such as card, foam, clay, MDF or 3D-printed plastic.
| Model Type | Material | Purpose |
|---|---|---|
| Card model (mock-up) | Card, paper, tape | Quick shape and proportion check; packaging net testing |
| Foam model | Styrofoam, blue foam (high-density polyurethane) | Form exploration; can be carved and sanded to shape |
| Clay model | Modelling clay, Plasticine | Ergonomic testing; automotive design (full-size clay models) |
| Breadboard model | Breadboard, components, wires | Electronic circuit prototyping (temporary, no soldering) |
| Toile | Calico or muslin fabric | Textile prototype to test fit and pattern before cutting expensive fabric |
| 3D-printed model | PLA, ABS, resin | Accurate representation of the final form; functional testing of mechanisms |
| Advantages | Disadvantages |
|---|---|
| Can be handled, held and tested physically | Time-consuming to make |
| Gives a realistic sense of scale and form | Materials cost money |
| Users can test ergonomics directly | Difficult to modify (may need to start again) |
| No specialist digital skills required | Only one version exists (unless duplicated) |
AQA Exam Tip: In your NEA, photograph your physical models and annotate the photographs. Explain what you tested, what you learned, and how it informed your next design iteration. This demonstrates the iterative design process.
CAD (Computer-Aided Design) software allows designers to create precise 2D drawings and 3D models digitally. CAD models can be modified easily, shared electronically and used to drive CAM (Computer-Aided Manufacturing) equipment.
| Software | Type | Use |
|---|---|---|
| 2D Design | 2D | Schools — laser cutter files, simple drawings |
| Techsoft Design V3 | 2D | Schools — CNC routing, laser cutting |
| Google SketchUp | 3D | Free modelling tool; architectural and product visualisation |
| Tinkercad | 3D | Free, browser-based; simple 3D models for 3D printing |
| Fusion 360 | 3D (parametric) | Industry-standard; product design, engineering, simulation, CAM |
| SolidWorks | 3D (parametric) | Professional engineering design; widely used in industry |
| Blender | 3D (surface/mesh) | Free; organic modelling, rendering, animation |
| Circuit Wizard | Schematic | PCB design and circuit simulation |
| Adobe Illustrator | 2D vector | Graphic design, packaging, logos |
| Feature | Description |
|---|---|
| Parametric modelling | Dimensions are linked — change one measurement and related features update automatically |
| Assembly modelling | Multiple parts are combined to check fit and interference |
| Rendering | Applying realistic materials, lighting and textures to create photorealistic images |
| Simulation / FEA | Finite Element Analysis tests stress, strain and heat on a virtual model |
| Exploded views | Automatically separating parts to show assembly order |
| Sectioning | Cutting through a model to show internal features |
| Revision history | Every change is saved; previous versions can be restored |
| Advantages | Disadvantages |
|---|---|
| Quick and easy to modify designs | Requires training and practice |
| Precise dimensions and tolerances | Software and hardware can be expensive |
| Can be shared electronically with global teams | Screen-based — lacks the tactile experience of physical models |
| Directly drives CAM equipment (CNC, 3D printing, laser cutting) | Risk of over-reliance — designers may skip hand sketching |
| Photorealistic rendering for client presentations | File compatibility issues between different software |
AQA Exam Tip: CAD/CAM integration is a key exam topic. Be ready to explain how a CAD file is converted to a format that drives a specific CAM machine (e.g. CAD drawing → DXF file → laser cutter; CAD model → STL file → 3D printer).
Annotation is the written notes, labels and explanations added to sketches, drawings and models to communicate design decisions, materials, dimensions, processes and reasoning.
| Element | Example |
|---|---|
| Materials | "Handle: beech timber — hard-wearing, attractive grain, comfortable to hold" |
| Dimensions | "Overall height: 250 mm (suits 50th–95th percentile hand grip)" |
| Manufacturing process | "Body: injection moulded in ABS — suitable for batch of 5,000 units" |
| Colour and finish | "Powder coated in RAL 9005 jet black — durable, scratch-resistant" |
| Design decisions | "Rounded corners to improve safety for young children (target age 3–7)" |
| Improvements | "Version 2: increased wall thickness from 2 mm to 3 mm after stress testing showed flex" |
AQA Exam Tip: Annotation turns a drawing from a picture into a design communication tool. Always annotate your sketches in the exam and in your NEA. Examiners award marks for the quality and depth of annotation, not just the drawing.
A design specification is a detailed list of measurable criteria that the final product must meet. It is created after the investigation stage and is used to evaluate designs throughout the project.
Specification points should be specific, measurable and justified.
| Weak Specification Point | Strong Specification Point |
|---|---|
| "It should be strong" | "The product must support a load of at least 5 kg without permanent deformation (based on intended use as a shelf bracket)" |
| "It should look nice" | "The product must be available in at least three colours to match user preferences identified in the questionnaire (78% wanted colour choice)" |
| "It should be cheap" | "The retail price must not exceed £15 to compete with similar products identified in the product analysis" |
The ACCESS FM framework can also structure a design specification:
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