Rapid prototyping, also known as solid freeform fabrication, is the automatic construction of physical objects with 3D printers, stereolithography machines or selective laser sintering systems. Rapid prototyping is a type of computer-aided manufacturing (CAM) and is one of the components of rapid manufacturing. The first techniques for rapid prototyping became available in the 1980s; traditionally they have been to produce models (prototypes). Nowadays, they are increasingly employed to produce tools or even to manufacture production quality parts in small numbers.

There are two main methods of rapid prototyping, which are derived from similar approaches in sculpture. In additive prototyping, the machine reads in data from a CAD drawing, and lays down successive millimeter-thick layers of liquid plastic, powdered plastic or some other engineering material, and in this way builds up the model from a long series of cross sections. These layers are glued together or fused (often using a laser) to create the cross section described in the CAD drawing.

The subtractive method is earlier and less efficient. In this technique the machine starts out with a block of plastic and uses a delicate cutting tool to carve away material, layer by layer to match the digital object. This is similar to a computer controlled lathe or mill and is not usually considered a rapid prototyping machine any more.

The standard interface between CAD software and rapid prototyping machines is the STL format .

The word "rapid" is relative: construction of a model with contemporary machines typically takes 3-72 hours, depending on machine type and model size.

Advances in technology allow the machine to use multiple materials in the construction of objects. This is important because it can use one material with a high melting point for the finished product, and another material with a low melting point as filler, to separate individual moving parts within the model. After the model is completed, it is heated to the point where the undesired material melts away, and what is left is a functional plastic machine. Although traditional injection molding is still cheaper for manufacturing plastic products, soon rapid prototyping may be used to produce finished goods in a single step.

Lab tests have shown that prototyping machines can also use conductive metals as a building material, and conceivably in the future could assemble small electronics like mobile phones in a single process.

Due to the high degree of flexibility and adaptability required by many rapid prototyping techniques, these applications typically require the use of robots or similar mechanisms.

As of 2005, the cheapest rapid prototyping machines cost about US$ 25 000 and are therefore still beyond the reach of most consumers.

However, there are currently several schemes to improve rapid prototyper technology to the stage where a prototyper can manufacture its own component parts. The idea behind this is that a new machine could be assembled relatively cheaply from raw materials by the owner of an existing one. Such crude 'self-replication' techniques could considerably reduce the cost of prototyping machines in the future, and hence any objects they are capable of manufacturing.

Rapid prototyping also describes a software engineering methodology.

External links

• Rapid Prototyping, Rapid Tooling, Sterolithography at ProtoCAM
• Rapid Prototyping, Sterolithography, Selective Laser Sintering at Paramount Industries
• Rapid Prototyping at AxisPrinter
• Rapid Prototyping at the CAISR laboratory
• Rapid Prototyping at Harvest Technologies
• Solid Freeform Fabrication Laboratory at University of Texas at Austin
• Self-Replicating Rapid Prototypers at the University of Bath