3D Printers and Additive Manufacturing Machines Information
3D printers fabricate three-dimensional solid objects from a digital model. 3D printers use an additive manufacturing (AM) process where successive layers of material are deposited in different shapes to form the final piece. Design instructions come from a digital file. These printers are used for prototyping and part repair or reproduction, as well as limited manufacturing applications.
3D printing (3DP) offers speedy fabrication and low material cost. In fact, 3DP is probably the fastest of all rapid prototyping methods. Recently there have been significant advances in printing resolution, product options and finishing, overall part size, and material specifications.
Stereolithography (SLA)—This was the first 3D printing method and was developed in the 1980s. A UV-curing resin is located in a reservoir with a submerged elevator platform. UV light from a DLP projector or laser traces an outline in the resin that causes it to harden. The elevator platform descends and another layer of the component is traced and cured. SLA has very high resolutions compared to other methods, though it is also slower due to curing times. Finished parts are not UV stable.
Fused filament fabrication (FFF) or fused deposition modeling (FDM)TM—This technique extrudes thermoplastic filament through a small nozzle, similar in concept to a hot glue gun. This process is done slowly to maintain uniform part thickness and accuracy. The plastic cools and cures so another layer can be built on top of it. Resolution, surface finish and many other variables can be operator controlled. Some printers have multiple nozzles for different colors or materials. Support materials may need to be constructed to ensure print structure stability, though supports can be mechanically or chemically removed.
Selective laser sintering (SLS) and selective laser melting (SLM)—These two methods are similar but not the same. SLS and SLM printers both use a laser to heat a powdered print material, where a laser is precisely aimed. In the case of SLM the material is melted, in the case of SLS it is sintered. Similar to SLA, parts are cured on a descending piston; however additional powder material is added to the vat between layers from a separate reservoir. The printing material can be anything that can be melted with the laser, which is typically thermoplastics but can be metals with the correct laser. SLS and SLM printers tend to be more expensive than other 3D printers due to the technology, but often produce superior printed components. Support materials are not needed, though printing in multiple materials is not possible.
PolyjetTM—This technique (copyright of Stratasys) uses inkjet heads which deposit a UV-curing resin which is immediately cured so that a new layer can be built on top of it.
Powder bed inkjet/binder jetting—This techniques deposits thin layers of powder on a binder or adhesive to bond layers together. Additional layers of powder are applied and the inkjet bonds it to the layer below. Parts tend to be weak and require additional processing before being used.
Other variations on these printer types can also be found such as direct metal laser sintering (DMLS) and electron beam fabrication (EBF), as well as emerging technologies such as continuous liquid interface production (CLIP).