"Additive fabrication refers to a group of technologies used for building physical models, prototypes, tooling components, and even finished series production parts—all from 3D computer-aided design (CAD) data, medical scans, or data from 3D scanning systems. Unlike CNC machines, which are subtractive in nature, additive systems join together liquid, powder, or sheet materials to form parts that may be impossible to fabricate by any other method. Based on thin horizontal cross sections taken from a 3D computer model, they produce plastic, metal, ceramic, or composite parts, layer upon layer. The three primary applications of additive fabrication are design and modeling, fit and function prototyping, and Rapid Manufacturing. " (http://wohlersassociates.com/additive-fabrication.html)
From the Replicator blog :
"“3D Printing” is an umbrella term that covers four distinct manufacturing technologies. All are “Additive Fabrication” processes that create objects by adding material in thin layers until a product is completed. Each technology addresses the challege differently with accompanying benefits and drawbacks."
"usually refers to object made using ink jet technology in three dimensions. As it’s name implies it is a close cousin to traditional 2D printing. These printers work by layering powder a powder substrate and binding it with pigmented glue"
The major manufacturer of 3D printing equipment is ZCorp.
"creates models by heating and extruding a filament of plastic material. Fused Deposition Modeling (FDM) creates models by heating and extruding a filament of plastic material. Stratasys commercialized this technology and owns the trademark.
"produces models by tracing a beam of UV light over a photosensitive pool of liquid. Over time the part is lowered into the bath and the final product is produced. The major benefit of this 3D printing technology is the high level of detail and surface finish it enables."
The Viper line of stereolithography apparatuses (SLA’s) manufactured by 3D Systems produce the highest quality 3D prints available.
"the awesome union of 3D printing and Lasers. The process is similar to stereolithography replacing the UV light with a laser and a vat of liquid with a powdered base. The major benefit of SLS is the ability to produce parts in a variety of materials ranging from plastics to ceraminc to metals."
The Sinterstation by 3D Systems is an example of this technology in practice.
"In addition, two other 3D printing technologies are maturing, but neither is in wide use yet.
Laminated Object Manufacturing (LOM) machines cut and glue thousands of sheets of material together to form solids. MCOR Technology has released a new 3D printer that promises to drastically reduce the cost of 3D printing by using standard A4 paper as the build material.
Electron Beam Melting (EBM) is similar to SLS technology except the process is far more exacting and capable of producing implant grade parts to be used in orthopedic surgery. The final product is higher quality and better embodies the traditional material characteristics making it a true replacement for standard manufacturing techniques. Arcam is the leading the charge in this exciting field." (http://replicatorinc.com/blog/2009/02/4-types-of-3d-printing/)