Key Idea: Thirty guide hours, and every statement says construct and interpret. This is a doing topic. Drawings: isometric communicates, orthographic specifies, exploded shows the order. Dimensions from a datum. Physical prototypes answer what the body judges — so full size, weighted, and taken to the real place. CAD: surface knows the skin, solid knows the volume, virtual knows behaviour. None of them knows how it feels. FEA needs a material, loads and constraints. Red is a concentration, blue is weight to remove, then test physically.
Paper 1 — multiple choice
- Read a line type or a view position on a drawing
- Match a CAD model type to a stated task
- Interpret a described FEA result
- Identify why a model will not print
Paper 2 — analysing a product
- Describe the drawings a named product needs, with reasons
- Justify the prototypes to build for a stated question
- Interpret an FEA image and give the design change
- Explain how a model is prepared for rapid prototyping
Carried into the design project
- Criterion C — modelling that produces data, not photographs
- Criterion D — the drawings a maker could actually work from
- Every prototype you build must state what it tested
Almost every mark in this topic comes from matching a representation to a question. Learn the table and the topic collapses to a page.
| The question | What to build | Because |
|---|---|---|
| Will somebody understand the form? | Isometric view or rendered 3D | One image carries the whole object to a person who has not seen it |
| What size is it, exactly? | Orthographic views, dimensioned from a datum | Each view is true size, and a chain of dimensions accumulates error |
| How does it go together? | Exploded assembly with a parts list | An assembly shows the fitted result, not the order |
| How heavy is it, and where is its centre? | Solid CAD model with a density | Only a solid knows what is material and what is air |
| Does it collide through its travel? | Virtual model | A static solid shows one position; a collision hides in the others |
| Where is it overstressed? | FEA, with material, loads and constraints stated | It finds the concentration, and the blue regions to lighten |
| What does it feel like to use? | A full-size, weighted physical prototype | Nothing on a screen has weight, balance or fatigue |
Say what your model could NOT test. A card model has no weight. An FDM part is weak across its layers. An FEA simulated one load on a perfect material. Naming the limit is worth more than claiming more than you showed.
Front view first, the rest projected. The alignment is how a reader carries a dimension between views.
🔒 Interactive diagram
Explore the labelled diagram, charts and maps for this topic in study mode.
| Order | Check | If you ignore it |
|---|---|---|
| 1 | Orientation — load along the layers, best face up | A bracket snaps between layers at a fraction of its load |
| 2 | Wall thickness against the nozzle or beam width | A 0.3 mm wall becomes a gap or a single fragile strand |
| 3 | Clearance of 0.2-0.4 mm at each mating face | A shaft and its hole come off the bed fused together |
| 4 | Supports reachable for removal | Support inside a closed cavity makes the part scrap |
| 5 | Watertight check, immediately before export | The slicer prints a shell or rejects the file |
Important: An isometric view offered as a manufacturing drawing. It cannot carry a reliable dimension set and has no sections. An unweighted foam model. With no mass there is no torque, so every grip shape feels comfortable and the test proves nothing. "The red area will break." Red is the highest stress in that simulation; failure depends on the numbers.
Pair every comment with what you observed before you change anything — and be willing to change nothing.
🔒 Interactive diagram
Explore the labelled diagram, charts and maps for this topic in study mode.
A school is developing a folding stool for its science labs. Justify the models and prototypes the team should build to answer: will it be stable when a student leans back, will it fit under the bench, and will the hinge survive a term?
🔒 Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
An FEA of the folding stool's hinge bracket shows a red band at the sharp internal corner where the arm meets the plate, and blue across most of the arm. Analyse the result and give the design changes.
🔒 Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
Dashed, chain-dotted, or solid?
First angle or third angle?
Why weight a foam model?
Surface, solid or virtual?
Does red on an FEA mean failure?
Why is orientation the first printing decision?
Exam tips
- Match the representation to the question. That is most of the marks.
- Orthographic: project the views, dimension from a datum, state the scale.
- Physical prototypes: full size, weighted, taken to the real place.
- CAD: say what the model knows, then name what it cannot tell you.
- FEA: quote material, loads and constraints; use the blue as well as the red.
- Printing: orientation first, then walls, clearances, supports, watertight.