Like most other RP processes (such as 3D Printing and stereolithography), FDM works on an "additive" principle by extruding material in layers. A plastic filament or metal wire is unwound from a coil and supplies material to an extrusion nozzle which turns the flow on and off. The nozzle is heated to melt the material and can be moved in both horizontal and vertical directions by a numerically controlled mechanism, controlled directly by a Computer Aided Design software package. In a similar manner to Stereolithography, the model is built up from layers as the plastic hardens immediately after extrusion from the nozzle.

The Dimension SST Printer uses Acrylonitrile Butadiene Styrene (ABS) Plastic to print solid objects at extremely high resolution directly from 3D CAD files in *.stl format. The ABS models are built up in thin layers, 0.01 in. to 0.013 in. thick. The resulting models are white, sturdy and can be sanded, drilled etc. with typical hand- and power tools. A water-soluble material is used for making temporary supports while manufacturing is in progress, which can later be dissolved away with a cleaning solution. No further post-processing is required for the models.

Several materials are available with different trade-offs between strength and temperature. As well as ABS plastic, the FDM technology can also be used with polycarbonates, polyphenylsulfones and waxes. Developments in the technology have seen the introduction of magnetic levitation to move the extruder head in place of conventional wires and electric motors.

For more information regarding Fused Deposition Modeling and other Rapid Prototyping technologies please see the Stratasys website @ www.stratasys.com