As most readers know, there are several types of additive manufacturing,
In FDM, the printer essentially acts like an autonomous hot glue gun following directions from computer files, called stereolithography (STL) files. Material is heated and extruded through a tip that moves in the direction required by the STL files. The part takes shape as molten material builds up layers, following the pattern of the plans. Most printers have more than one material nozzle and can change color or material as required. Some printers can also build a support framework from material, including dissolvable material, inside the piece if needed.
A host of materials, mostly thermoplastics, are used for FDM printing including Acrylonitrile Butadiene Styrene, Polylactic acid, Polycarbonate, Polyamide, Polystyrene and even synthetic rubber. The material is chosen based on the purpose of the part, as different materials have varying properties.
The other day, one of our engineers needed to print some parts for functional testing of a product we’re working on. You can see the nozzle moving back and forth, layering plastic in this video:
So, to answer our question, FDM is typically used for rapid prototyping, though it is also used for pre-production runs (to get samples for the customer) or low volume production runs if you want to do some market research or testing.
The main reasons for using FDM are cost and time. Rather than investing (tens of) thousands of dollars into an injection tool, you can 3D print the part. It's a much faster and lower cost way to move your product idea into production.
To learn more about 3D printing and prototyping, check out these posts: