Layered Manufacturing is actually better known as Rapid Prototyping, which, is the most common name given to a host of related technologies that are used to fabricate physical objects directly from CAD data sources. These methods are unique in that they add and bond materials in layers to form objects. Such systems are also known by the general names freeform fabrication (FFF), solid freeform fabrication (SFF) and layered manufacturing. Today's additive technologies offer advantages in many applications compared to classical subtractive fabrication methods such as milling or turning:

• Objects can be formed with any geometric complexity or intricacy without the need for elaborate machine setup or final assembly;

• Rapid prototyping systems reduce the construction of complex objects to a manageable, straightforward, and relatively fast process.

This has resulted in their wide use by engineers as a way to reduce time to market in manufacturing, to better understand and communicate product designs, and to make rapid tooling to manufacture those products. Surgeons, architects, artists and individuals from many other disciplines also routinely use the technology.

Rapid prototyping isn't a solution to every part fabrication problem. After all, CNC technology is economical, widely understood and available, offers wide material selection and excellent accuracy. However, if the requirement involves producing a part or object of even moderately complex geometry, and doing so quickly - RP has the advantage. It's very easy to look at extreme cases and make a determination of which technology route to pursue, CNC or RP. For many other less extreme cases the selection crossover line is hazy, moves all the time, and depends on a number of variably-weighted, case-dependent factors. While the accuracy of rapid prototyping isn't generally as good as CNC, it's adequate today for a wide range of exacting applications.

The materials used in rapid prototyping are limited and dependent on the method chosen. However, the range and properties available are growing quickly. Numerous plastics, ceramics, metals ranging from stainless steel to titanium, and wood-like paper are available. At any rate, numerous secondary processes are available to convert patterns made in a rapid prototyping process to final materials or tools.

The names of specific processes themselves are also often used as synonyms for the entire field. Among these are stereolithography (SLA for stereolithography apparatus), selective laser sintering (SLS), fused deposition modeling (FDM), laminated object manufacturing (LOM), inkjet systems and three dimensional printing (3DP). Each of these technologies - and many others - has its singular strengths and weaknesses.