The earliest use of additive manufacturing was in rapid prototyping (RP) during the late 1980s and early 1990s. Prototypes allow manufacturers a chance to examine an object's design more closely and even test it before producing a finished product. RP allowed manufacturers to produce those prototypes much faster than before, often within days or sometimes hours of conceiving the design. In RP, designers create models using computer-aided design (CAD) software, and then machines follow that software model to determine how to construct the object. The process of building that object by "printing" its cross-sections layer by layer became known as 3-D printing.
The earliest development of 3-D printing technologies happened at Massachusetts Institute of Technology (MIT) and at a company called 3D Systems. In the early 1990s, MIT developed a procedure it trademarked with the name 3-D Printing, which it officially abbreviated as 3DP. As of February 2011, MIT has granted licenses to six companies to use and promote the 3DP process in its products [source: MIT].
3D Systems, based in Rock Hill, SC, has pioneered and used a variety of 3-D printing approaches since its founding in 1986. It has even trademarked some of its technologies, such as the stereolithography apparatus (SLA) and selective laser sintering (SLS), each described later in this article. While MIT and 3D Systems remain leaders in the field of 3-D printing, other companies such as Z Corporation, Objet Geometries and Stratasys have also brought innovative new products to market, building on these AM technologies.
Today, some of the same 3-D printing technology that contributed to RP is now being used to create finished products [source: The Economist]. The technology continues to improve in various ways, from the fineness of detail a machine can print to the amount of time required to clean and finish the object when the printing is complete. The processes are getting faster, the materials and equipment are getting cheaper, and more materials are being used, including metals and ceramics. Printing machines now range from the size of a small car to the size of a microwave oven.
3-D printing and other forms of AM are still new players in the field of manufacturing. Additive manufacturing is often compared to, or even mistaken for, another common manufacturing process called computer numerical controlled (CNC) machining. However, CNC is subtractive, which is the opposite of AM. In CNC machining, material is removed from some pre-existing block until the finished product remains, much like a carving a statue from stone.
Now that you have some background information about the field, let's explore some 3-D printing technologies.