FDM is the second most widely used
rapid prototyping technology, after Stereolithography. A plastic
filament is unwound from a coil and supplies material to an extrusion
nozzle. The nozzle is heated to melt the plastic and has a mechanism
which allows the flow of the melted plastic to be turned on and off. The
nozzle is mounted to a mechanical stage which can be moved in both
horizontal and vertical directions.
As the nozzle is moved over the table in the required geometry, it
deposits a thin bead of extruded plastic to form each layer. The plastic
hardens immediately after being squirted from the nozzle and bonds to
the layer below. The entire system is contained within a chamber which
is held at a temperature just below the melting point of the plastic.
Several materials are available for the process including ABS and
investment casting wax. ABS offers good strength, and more recently
polycarbonate and polyphenylsulfone materials have been introduced
which extend the capabilities of the method further in terms of strength
and temperature range. Support structures are fabricated for overhanging
geometries and are later removed by breaking them away from the object.
A water-soluble support material which can simply be
washed away is also available.
Back Button to return