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Tuesday, July 17, 2007

Rapid prototyping also describes a software engineering methodology

Rapid prototyping is the automatic construction of physical objects using additive fabrication. The first techniques for rapid prototyping became available in the late 1980s and were used to produce models and prototype parts. Today, they are used for a much wider range of applications and are even used to manufacture production quality parts in relatively small numbers. Some sculptors use the technology to produce complex shapes for fine arts exhibitions.
1 Introduction
2 Technologies
3 References
4 See also
5 External links

Rapid prototyping takes virtual designs from computer aided design (CAD) or animation modeling software, transforms them into thin horizontal cross sections, still virtual, and then creates each cross section in physical space, one after the next until the model is finished. It is a WYSIWYG process where the virtual model and the physical model correspond almost identically.
With additive fabrication, the machine reads in data from a CAD drawing and lays down successive layers of liquid, powder, or sheet material, and in this way builds up the model from a series of cross sections. These layers, which correspond to the virtual cross section from the CAD model, are joined together or fused automatically to create the final shape. The primary advantage to additive fabrication is its ability to create almost any shape or geometric feature.
The standard data interface between CAD software and the machines is the STL file format. An STL file approximates the shape of a part or assembly using triangular facets. Tiny facets produce a higher quality surface.
The word "rapid" is relative: construction of a model with contemporary methods can take from several hours to several days, depending on the method used and the size and complexity of the model. Additive systems for rapid prototyping can typically produce models in a few hours, although it can vary widely depending on the type of machine being used and the size and number of models being produced simultaneously.
Some solid freeform fabrication techniques use two materials in the course of constructing parts. The first material is the part material and the second is the support material (to support overhaving features during construction). The support material is later removed by heat or desolved away with a solvent or water.
Traditional injection molding can be less expensive for manufacturing plastic products in high quantities, but additive fabrication can be faster and less expensive when producing relatively small quantities of parts.

[edit] Technologies
A large number of competing technologies are available in the marketplace. As all are additive technologies, their main differences are found in the way layers are built to create parts. Some are melting or softening material to produce the layers(LS, FDM) where others are laying liquid materials thermosets that are cured with different technologies (SL, MJM, PolyJet). In the case of lamination systems, thin layers are cut to shape and joined together.
Prototyping Technologies
Base Materials
Laser sintering (LS)
Thermoplastics, metals powders
Fused Deposition Modeling (FDM)
Thermoplastics, Eutectic metals.
Stereolithography (SL)
Multi Jet Modeling (MJM)
Electron Beam Melting (EBM)
Titanium alloys
3D Printing (3DP)
Various materials
Objet PolyJet Modeling

Wohlers, T.(2007). Rapid Prototyping Terms and Descriptions.
Grenda, E. (2006). The Most Important Commercial Rapid Prototyping Technologies at a Glance.
Wright, Paul K. (2001). 21st Century manufacturing. New Jersey: Prentice-Hall Inc.

See also
Solid freeform fabrication: A list of technologies used in rapid prototyping.
3D printing: Faster, more affordable rapid prototyping
MeshLab An open source Windows and Linux application for visualizing, processing and converting 3D meshes to or from the STL file format.
3D microfabrication
The TCT Magazine: Bi Monthly Magazine covering RP

External links
Technical Articles - Many articles on the subject from Wohlers Associates
The Rapid Prototyping Home Page
Rapid prototyping websites at the Open Directory Project
TCT Magazine - Bi Monthly Magazine focusing on rapid product development
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