This mini-lesson covers Topic 3 — Modelling: conceptual and graphical models, drawing conventions, scale, CAD, and physical prototypes including rapid prototyping.
Work through each screen, answer the questions as you go (some are wordy, some are calculations) and collect ⭐ stars. Press Start when you are ready.
A model is a representation of a design used to develop, communicate and test ideas before committing to full production. Modelling lets a designer explore options quickly and cheaply, spot problems early, and get feedback from users and clients.
Models range from rough conceptual sketches, through accurate graphical and CAD models, to physical prototypes that can actually be handled and tested.
Key idea: the cost of changing a design rises steeply as you move toward production — so it pays to find faults at the modelling stage.
Graphical models communicate a design on paper or screen using agreed conventions so anyone can read them:
Watch out: isometric keeps edges parallel and to scale; perspective does not (distant edges shrink). Use orthographic for accurate, dimensioned production drawings.
A scale model represents a real object at a fixed ratio. A scale of 1:20 means the real object is 20 times bigger than the model.
A boat is 4.6 m = 4600 mm long, modelled at 1:20.
model length = 4600 ÷ 20 = 230 mm
Tap a model, then tap the group it belongs to.
CAD (computer-aided design) builds accurate, editable 3D models that can be measured, rendered, shared and tested virtually. CAD drives CAM (machining), FEA (stress analysis) and rapid prototyping.
A prototype is a physical, usually working, model used to test function and get user feedback. Rapid prototyping (e.g. 3D printing) builds a part directly from CAD, layer by layer, in hours — ideal for quick iteration.
Key idea: an aesthetic model shows how a product will look; a prototype shows how it will work. Many projects need both.
Tap a description on the left, then its term on the right.
Orthographic drawings follow a convention set by a symbol in the title block. In third-angle projection (common in the USA) each view sits on the side it is seen from; in first-angle (common in Europe) it is placed on the opposite side.
Getting this wrong flips the layout and can cause a part to be made mirror-imaged, so the projection symbol and dimensions are essential.
When a model scales up, length scales by the factor, area by its square and volume (and mass) by its cube. A 1:20 model has 1/400 of the surface area and 1/8000 of the volume of the real object.
Watch out: this is why a scale model can behave differently from the full-size product — strength, heat loss and airflow do not scale linearly.
A CAD model is more than a picture: its geometry can drive a CAM tool-path so a CNC machine or 3D printer makes the part directly. This tight link removes re-drawing, cuts errors and speeds iteration.
The same model can be rendered for clients, analysed for stress, and shared instantly across a design team anywhere in the world.
Different questions need different models: a concept sketch explores ideas fast; an aesthetic model checks how it looks and feels; a working prototype tests function; an FEA model predicts stress before any material is cut.
Skilled designers pick the cheapest model that answers the current question, and only build more detailed models as the design firms up.
Virtual (CAD/CAE) models are cheap to change, easy to test and share, and can simulate physics. But they are only as good as their assumptions, cannot fully capture how a product feels in the hand, and may miss manufacturing realities.
Key idea: most serious projects combine virtual modelling with at least one physical prototype before committing to production.
Conceptual models: ideas explored as sketches and diagrams early on.
Graphical models: orthographic (flat views), isometric and perspective drawings.
Scale: scale = real size ÷ model size; area scales by the square, volume by the cube.
CAD: accurate, editable, shareable digital models; enables CAM, FEA and rapid prototyping.
Prototypes: physical, working models used to test and evaluate a design.
You have worked through Modelling for IB Diploma Design Technology SL. Press Finish to see your score.
You have worked through Modelling for IB Diploma Design Technology SL. 🎉
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Next: test yourself in the Evaluate stage Confidence Quiz, then lock it in with Verify.