1.2 · 3D Printing

Goal: describe how 3D printing works and give realistic applications.

What it is

3D printing (additive manufacturing) builds objects layer by layer from a digital model, using materials such as plastic (PLA, ABS), resin, metal, even concrete or biomaterials.

How it works (simplified)

Design 3D model (CAD)
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Slice into thin layers
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Printer deposits material layer by layer
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Object solidifies

Common processes

Process	Material	Use
FDM (Fused Deposition Modeling)	Plastic filament	Cheapest, hobby, prototyping
SLA (Stereolithography)	UV-cured resin	High detail, jewellery, dental
SLS (Selective Laser Sintering)	Powder	Functional plastic parts
Metal SLM	Metal powder	Aerospace, custom medical implants

Real-world applications

Field	Use case
Healthcare	Custom prosthetics, dental crowns, hearing-aid shells
Aerospace	Lightweight engine parts
Architecture	Building models, concrete printing
Education	Hands-on STEM projects
Fashion	Customised shoes, jewellery
Food	Personalised chocolates, lab-grown meat scaffolds

Benefits

• Rapid prototyping — design to physical object in hours.
• Customisation — every print can be unique.
• Low overhead — no special tooling needed.
• Less waste — only adds material that ends up in the part.

Limitations

• Slow for mass production.
• Material strength may be lower than traditional manufacturing.
• High-end printers and materials are expensive.

Hong Kong context

• HK Science Park has 3D-printing labs.
• Many schools own desktop FDM printers.
• Used in product-design and engineering courses at the Polytechnic University.

Exam-style question

Q (4 marks): Explain how 3D printing works and give two practical applications.

Sample answer:

3D printing builds physical objects layer by layer from a digital 3D model. Software slices the model into thin layers; the printer deposits material (e.g. melted plastic in FDM) one layer at a time, fusing each layer to the previous one until the object is complete.

Two applications:

• Custom prosthetics — patient's limb is scanned, model adjusted, prosthetic printed in plastic at much lower cost than traditional fabrication.
• Rapid prototyping — product designers print iterative versions of a new gadget within hours, testing form and fit before tooling for mass production.

Key takeaways

• Builds layer by layer from a digital model.
• Many materials and processes.
• Great for customisation and rapid prototypes; less ideal for mass production.

➡️ Next: 1.3 AR & VR