Approximately 30% of all plastic products in the world are produced by
an injection molding process. Within this another 30% are produced
using a custom injection molding technology. There are basically six
steps involved in the normal injection molding process. The first step
is the clamping of the mould, the clamping unit makes for one of the
three units of the molding machine. The other two being the injection
unit and the mold, once the clamping unit holds on to the mold, the
molten plastic is injected into the mold by the injection unit. The
plastic is fed in the form of tiny pellets onto a hopper. These are
then allowed into a cylinder where they are heated into a molten state
and injected into the mold. The steps that follow are referred to as
dwelling phase. It basically involves making sure all the cavities in
the mold are fully filled. The mold is then allowed to cool with the
clamping intact. Finally the mold is opened and the component is
ejected out. The biggest advantage of plastic injection molding is the
cost factor of the produced parts, especially when you need large
number of parts. The disadvantage is the cost of manufacturing the
molds; a simple injection mold can cost you $3000 while the bigger
complex ones can run into several hundreds of thousands.
Rapid Prototyping: Rapid Prototyping is the process of automated
manufacturing of physical components using solid freeform fabrication.
They are used in a wide range of applications, everything from medical
to fine art. Rapid Prototyping machine works by taking virtual models
from software and then converting it into extremely thin, horizontal
cross-sections and then goes onto create each of the cross-section in
physical space in a cyclic manner until the model is completed. Rapid
Prototyping is a WYSIWYG process in which the virtual model bears
identical resemblance to the finished physical model. Additional
fabrications allows the machine to lay down layers of sheet, liquid or
powder material and build up a series of cross-sections These layers
are finally automatically fused together to render the final product.
The main advantage of rapid prototyping is the ability to create any
shape no matter how complex the geometry is. The commonly used data
interface between the machine and the software is the STL format. It
works by approximating the geometry of a part using triangular facets,
smaller the facets higher will be the surface quality. The word
“rapid†is used relative top conventional methods which take days
to construct a model depending upon its complexity. Rapid prototyping
can create the model within a few hours, though it is highly dependent
of the type of machines and the size of the model. There have been
several new technologies available for rapid prototyping including
Fused Deposition Modeling, Selective laser sintering, 3D printing, and
Electron Beam Melting.
Prototyping Injection Molding is a specialized method of combining
traditional plastic injection molding. CAM software are able to combine
rapid tooling and plastic injection molding in order to quickly create
small quantities of any thermoplastic part.
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