The concept of 3D Printing aka Additive Manufacturing remains the same in all different 3D Printing technologies, processes, and techniques. And that is Layers! All of the below technologies 3D Print or manufacture an object in layers. Additive technology as the name suggests adds thin layers (Microns) to create an object from a Computer Aided Design File usually .STL/.OBJ file format.
Fused Deposition Modeling Technology
Invented by S. Scott Crumb in 1988, Fused Deposition Modeling or more commonly known as FDM Technology is one of the most popular methods of 3D Printing because of its affordability and capability to use multiple materials such as ABS, PLA, HIPS, Nylon and more on the same machine. The process works by melting the material and extruding it through a nozzle to 3D Print layers of an object.
Stereo-lithography Technology
This technology is the first commercial Rapid Prototyping Technology also commonly known as SLA. Chuck Hull, the co-founder of 3D Systems invented Stereo-lithography technology along with the STL file format. Photo-polymer resin is used as a raw material in this process where the build plate dips into a resin filled tray. Light from an UV Laser is projected from below the resin tray, hardening the resin onto the build platform. Layer by layer this process repeats until the model is created.
Multi-jet Technology
The Multijet 3D Printer works in a similar fashion as the SLA Technology mentioned above. The main difference though is the use of photo-polymer which is jet sprayed in the form of fine particles that are cured using a UV lamp that is attached to the printer head. This step is repeated over and over in layers to form the final object.
Digital Light Processing Technology
DLP printing technique uses a projector to cure photo-polymer resin. The only difference between SLA technology and DLP technology is the use of curing light. The former uses UV light and the later uses a light bulb. Otherwise the concept of additive manufacturing remains the same in both the processes.
Binder Jetting
A binder Jetting machine will spread a layer of powder onto a build platform. A bonding liquid is sprayed through the printer head, fusing the powdered material together in a layer of the desired shape of the object. The build platform lowers and the step is repeated, building the object layer by layer. The biggest advantage of this technology is the ability to 3D Print in full color. The objects resulting from this technology are fragile thus used for show and tell or as decorative pieces. Best example of products from these 3D Printers are 3D Selfies; Full color 3D Printed Figurines printed by scanning a person or object.
Selective Laser Sintering Technology
Commonly known as SLS Technology, this process uses powdered materials such as Nylon. The powder is melted in successive layers and bonded together to form an object. Complex and interlocking objects can easily be 3D Printed using this process.
Direct Metal Laser Sintering Technology
DMLS Technology uses a high powered laser to sinter metal powder (Metal alloy) along the path of the object layer by layer. The build platform lowers and a layer of powdered material is rolled on. The step is repeated, building the object layer by layer. This process is very similar to the SLS Technology.