The big idea: An additive technique builds an object one layer at a time, each layer bonded to the one below.
Every strength and limitation of 3D printing follows from that
- The layer height sets the surface.
- The orientation sets which way the part is weak.
- The overhangs set what support has to be printed and thrown away.
CAD model → orient → slice → build → finish, then the three techniques the guide names.
Interactive diagram
Explore the labelled diagram, charts and maps for this topic in full study mode.
Free preview
This is the free notes preview
You're reading the free notes. Aimnova Pro unlocks the full study experience — and you can try it with your first topic free to keep:
- FlashcardsLock in vocabulary and key terms with spaced repetition.
- Practice questionsAnswer exam-style questions and get instant AI marking.
- Mock exams & past-paper vaultSit full mocks and see exactly how examiners award marks.
- Personalised study planA daily plan built around your exam date and weak areas.
| Technique | How each layer is made | What it gives you |
|---|---|---|
| LOM — laminated object manufacture | Sheets of paper, plastic or metal foil are glued down one at a time and each is cut to its outline with a blade or laser | Cheap materials and large parts, with a wood-like block that can be sanded — but the cut-away material is waste and the part is weak between layers |
| FDM — fused deposition modelling | A filament of thermoplastic is melted and extruded through a moving nozzle, drawing each layer as a path | Cheap machines and real engineering plastics, with visible layer lines and a part noticeably weaker between layers than along them |
| SLA — stereolithography | A laser or projector cures liquid photopolymer resin one layer at a time on a platform lifting out of a vat | The finest detail and smoothest surface of the three, from a material that is brittle, degrades in sunlight, and must be washed and cured |
Same chain, different way of making a layer: All three take a CAD model, orient it, slice it and build it layer by layer.
What differs is only how each layer is created — glued and cut, extruded, or cured with light — and that difference decides the material, the finish and the cost.
See how examiners mark answers
Answer exam-style questions with model answers. Learn exactly what earns marks and what doesn't.
Four consequences of building in layers
Layer lines on every curve
A sloping surface is a staircase of layer edges. Thinner layers reduce it and take proportionately longer, which is a direct trade of finish against time.
Weakness between layers
The bond between layers is weaker than the material itself, so a printed part breaks along a layer. The build orientation therefore decides which direction it can be loaded in.
Support under overhangs
Nothing holds up material printed over air, so overhangs steeper than about 45° need support printed underneath and removed afterwards — material and time, both wasted.
Shapes nothing else can make
Internal channels, lattices and parts that would need a mould split into six pieces are all possible, because the machine never has to remove a tool from inside the part.
The orientation question: If a printed hook will hang a load, print it so the load runs along the layers rather than trying to peel them apart.
The same part, printed the other way up, can be several times stronger — for exactly the same material and the same machine time.
Why a manufacturer chooses additive
Shapes nothing else can make
Internal lattices and channels: lighter parts for the same strength, as in printed aircraft brackets.
Material only where needed
Far less waste than machining from a block, which matters with titanium.
No tooling
Print straight from the CAD file, so design changes and one-offs cost little.
How this is tested — explaining how components are produced using additive manufacturing, including LOM, FDM and SLA. It comes up two ways:
Paper 1 — multiple choice
- Identify an additive technique from a description of the machine.
- Choose the technique that suits a stated requirement.
Paper 2 — analysing a product
- Explain how a named component is produced by an additive technique.
- Justify the choice of one additive technique over another.
The trap: Describing a machine without the consequence. Layer lines, directional weakness and support material are what a designer has to live with, and they are where the marks are.
A jeweller needs a master pattern for a ring, with fine surface detail, to be used in casting. Justify the additive technique you would choose.
Model answer plan
See the answer broken into clear points, with guidance on how each point earns marks.