The models themselves are first constructed in computer 3D, using software such as Blender. A piece of software called a ‘slicer’ then breaks the 3D computer models up into components to be printed. There are two main types of 3D printing – FDM (Fused Deposition Modelling) and STL (Stereo Lithography).
FDM printing heats a plastic filament and squeezes it onto a steel plate in layers to slowly build up the 3D print. The FDM plastic is predominantly based on corn-starch, so the plastic created can be recycled.
STL printing uses a photosensitive nylon resin and prints components in layers by breaking the model down into thin sections (rather like a CAT scan). STL plastic can be tough, but it’s generally not recyclable
Many mass-market kits are injection moulded, using very expensive machines and steel moulds. This means that hundreds of thousands of the models need to be produced in order to make them cheap enough to sell. Huge print runs mean that it’s difficult to produce models of rare or unusual subjects. Injection moulding also uses a petroleum-based polystyrene.
