There are various types of 3D printers but for sake of efficiency I’ll only research the two main 3D printers available –
SLS (Selective Laser Sintering) & FDM (Fused Deposit Modelling) –
SLS works using a system of pistons, roller balls and lasers. The item being created sits on the fabrications piston and is formed layer by layer as the roller ball pushes powders (which is also being raised on a piston) onto the next layer ready to be lased/fused to the previous layer. These layers build up to create a fully formed object. SLS only uses powders polyamide materials rather than other 3D printing systems that use liquid resins and other such materials.
Similarly to the previous printer, FDM also builds the object up layer by layer, but rather than using roller balls and powders, the system uses a system of spools and extruded molten plastics to form the object. Also similarly to the previous printer, FDM also has a piston that lowers the object to build further layers as the process continues. Most kinds of thermoplastic are suitable for this printer as well as a variety of other materials.