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Rapid prototyping processes
are a relatively recent development. The first machine was released
onto the market in late 1987. While rapid prototyping is the
term commonly applied to these technologies the terminology is
now a little dated, reflecting the purpose to which the early
machines were applied. A more accurate description would be layer
manufacturing processes. An alternative term is free-form fabrication
processes.
These processes work by building
up a component layer by layer, with one thin layer of material
bonded to the previous thin layer. There are several different
processes. The main ones are:
- stereolithography;
- laser sintering;
- fused deposition modelling;
- solid ground curing; and
- laminated object manufacturing.
In addition there are a number
of newer processes, such as ballistic particle manufacturing
and three-dimensional printing, which have appeared on the market.
All these processes essentially
start with nothing and end with a completed part. This is in
contrast to conventional manufacturing processes such as milling
machines that start from a solid block of a substance and cut
material away to form the finished part.
Rapid prototyping processes
are driven by instructions which are derived from three-dimensional
computer-aided design (CAD) models. CAD technologies are therefore
an essential enabling system for rapid prototyping.
The processes use different
physical principles, but essentially they work either by using
lasers to cut, cure or sinter material into a layer, or involve
ejecting material from a nozzle to create a layer. Many different
materials are used, depending upon the particular process. Materials
include thermopolymers, photopolymers, other plastics, paper,
wax, metallic powder, etc.
The application of these processes
is not restricted to supporting new product development activities
C they can also be used to create production tooling. They can
therefore be used to support one-off or small batch production
runs. Thus the processes can be used to create models, tooling,
prototypes, and even in some cases to directly produce metal
components.
Many rapid prototyping technologies
actually produce physical models. These models are then used
to produce tooling using an indirect secondary process such as
investment casting. The resulting tool is then used to manufacture
a component. However, new processes are beginning to appear that
allow the tooling to be manufactured directly from the computer
model, thus eliminating the physical model production stage.
In the future it is likely to be possible to manufacture components
directly from the computer model, eliminating the need to produce
physical models and tooling first, although these may still be
required for other purposes.
The important point to understand
is that, while rapid prototyping started out as an expensive
tool for producing physical models for design engineers to visualise
their component designs, this is now no longer an accurate description
of the technologies or their application potential.
The potential different applications
of rapid prototyping technologies span the complete product life
cycle from concept generation, through preparation of specifications
and detailed design, to manufacture.
Two further points. First,
rapid prototyping technologies address the area of prototyping
mechanical devices, components, housings, etc. and not software
or electronic components. Second, rapid prototyping technologies
are often used instead of conventional manufacturing processes
such as five axis milling machines. However, there are situations
when the two are used in combination to produce prototypes. Sometimes,
however, components are simple enough to be quickly and cost-effectively
prototyped using conventional methods C in other words there
are situations in which rapid prototyping processes offer no
time or cost advantages over conventional technologies.
Further information about the
processes and associated technologies is given in Chapter
7 of the Management Report. Links to vendors' web site are
provided elsewhere on this
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