As outlined in our introduction to 3D printing, the basics of 3D printing involve building up layers of material until a solid shape is formed. There are several methods for achieving this, this page should act as a brief guide to some of these different methods.
Fused Deposition Modelling (FDM)
This method, also called Fused Filament Fabrication (FFF), is the most common type of 3D printing used in home and hobby 3D printing. In FDM/FFF 3D printing, the finished object is produced by extruding a stream of melted thermoplastic material into gradual layers. Each layer stacks on top of the previous layer and they harden together as the plastic dries. This happens quickly since the material hardens almost immediately after leaving the extrusion nozzle. FDM is the cheapest 3D printing method, which is why it is so popular for home/hobby printing. One of its drawbacks is that it has the lowest resolution of any method, meaning that printing in a lot of detail is difficult.
The SLA method was the first true 3D printing method. SLA differs a great deal from FDM, although the principle is the same. That is to say layers of hardened substance are gradually added to other layers until a solid object is formed. An SLA 3D printer works by focusing a beam of ultraviolet (UV) light onto the surface of a liquid photocurable resin. The UV light draws on the liquid in a predetermined outline, hardening that “slice” of the eventual 3D model as the light hits the resin, the level of the liquid then lowers (or rises) by a miniscule amount and the next layer is created. The main benefit of this method is that it creates extremely high-resolution models, but it is quite expensive, this makes this method more common among professional model makers and designers, as well as being used for many industrial applications.
As mentioned in the FDM section above, a nozzle that excretes a semi solid liquid is used to 3D print. This means that almost any material that has a creamy or semi solid viscosity can be used in 3D printers equipped with syringe extruders. This includes materials like clay, glue, silicone, and some biological materials. Certain foods like chocolate, frosting, and cheese can also be printed with these systems. Some of these materials need to be heated and then cooled to create a 3D model, others harden when exposed to air. These machines are little more than a novelty, especially when it comes to food, that can be used to create interesting designs, but usually without a high level of detail.
Photopolymer printing works much like a traditional inkjet printer. But whereas a traditional inkjet printer deposits ink, a photopolymer liquid is jetted out of a nozzle and then hardened with a UV light. The layers are stacked one by one just like other 3D printing technologies, but it is the combination of material stacking and use of UV light that separates this type of printing from other methods. Polyjet Photopolymer allows for various materials and colors to be incorporated into single prints, and at high resolutions. This use of colour makes this method of 3D printing a popular choice for designers and prototypers.
Selective Laser Sintering (SLS)
Selective Laser Sintering (SLS) was developed by Carl Deckard at the University of Texas in Austin in the 1980s. SLS works similarly to SLA, but instead of using a liquid photopolymer, SLS uses powdered materials, such as polystyrene, glass, ceramics, steel, titanium, aluminum, and silver. A laser hits the powder, the powder is fused at that point and becomes ‘sintered’. All unsintered powder remains as is, and becomes a medium to support the object until the printing process is finished. It is this built in support mechanism that gives SLS the biggest draw over other 3D printing methods, no materials need to be removed or pared away after the model is complete, and no extra waste was created. The model can be removed fully finished from the machine and be put to use immediately. All unused powder can be used for the next printing process. SLS is one of the most popular methods of 3D printing in industrial applications.
Other types of 3D printing
As stated above, 3D printing is defined by the use of a machine that adds successive layers of material to make a solid object from a computer file. There are other variants of these technologies, some of which are not strictly 3D printing. For example, one of these methods is Selective Laser Melting (SLM), which is like SLS but it fully melts the powder rather than just fusing the powder granules at a lower temperature. There also exists a completely different technology called Laminated Object Manufacturing (LOM), where layers of adhesive-coated paper, plastic, or metal laminates are glued together and cut to shape by hand.