3D printers: building objects layer by layer

Picture a hot glue gun that a computer steers with perfect precision. It draws one flat shape, then another on top, then another, hundreds of times.

That's a 3D printer. It's called additive manufacturing because it adds material layer by layer, instead of cutting it away from a block.

"Describe how a 3D printer produces an object." Usually 3 to 5 marks.

Marks come from the journey: design, slice, print layer by layer, solidify, finish.

1. The object is designed using CAD (computer-aided design) software, or scanned with a 3D scanner.
2. Slicing software cuts the design into many thin horizontal layers and turns them into instructions for the printer.
3. The printer builds the object one layer at a time, from the bottom up. In the common type, plastic filament is melted in a heated nozzle that moves in x and y, laying down material only where that layer needs it.
4. Each layer cools and hardens before the next layer is added on top; the build plate drops (or the nozzle rises) by one layer height.
5. Repeat until the object is complete, then remove any support material and clean or finish it.

Step 4 is the one people forget. Without it, there's nothing explaining how a flat drawing becomes a tall solid.

Uses include prototypes, custom medical parts (prosthetic limbs, dental models), spare parts and architects' models.