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rapid prototyping (RP)
Rapid Prototyping
is a generic term to describe a number of technologies that enables production
of real physical objects directly from 3-dimensional computer aided design
(CAD) data.
The principle of Rapid Prototyping relies on building an object from a
series of stacked cross-sections. A computer model (3 dimensional drawing)
is divided into very thin layers by the software thereby converting a
3D manufacturing task into a series 2D ones. The object is then constructed
layer-upon-layer by a computer-controlled RP machine. The bonded stack
of layers forms the final solid object.
The main
advantage with the RP technology is that it gives almost total geometrical
freedom to create objects that were previously almost impossible to build
or required numerous separate development stages.
There are five main commercial processes to choose from: Stereolithography
(SLA), Selective Laser Sintering (SLS), Fused Deposition Modeling (FDM),
Z Corp and Laminated Object Manufacture (LOM). The first three provides
models in plastics or resins, Z Corp use a powder (usually plaster) fused
with a binder and LOM create models by layers of glued paper.
In the ceramic industry the technology has already become firmly established
for creating realistic presentation prototypes that would previously require
enormous amounts modelling and mould making. The preferred method is FDM
as it produces high quality prototypes of robust ABS plastic that can
tested and handled like the final item. Z Corp machines are a cheaper
alternative but the material strength and the surface quality is not as
good as with FDM. The textured surface, which is characteristic for RP
in general, also means that the process is rarely used to make the final
models to produce moulds from. For this task CNC (computer numerically
controlled) milling, which can utilize the same computer data as an RP
object, remains the better option.
laminated
object manufacture (LOM)
Objects are
build by layers of pre-glued paper that are joined layer by layer with
a heated roller. Each layer is cut by a laser beam to represent the cross-section
of the object at that particular level. The build platform moves downwards
and the cycle starts again. The laser intensity is set to cut through
only one single layer of paper thereby not damaging the previous layers.
The rest of the glued paper works as support for the model while building
but is essentially scrap and automatically crosshatched by the laser for
easy removal. Although the build material is usually paper a variety of
other sheet material, such as MDF, can also be used.
LOM is particularly suited for creating large models and most commonly
used in the automotive industry. The process is rarely used in the ceramic
sector, but for the Contour Project LOM was
the only RP method that could deliver the pronounced stepped texture.
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