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TRANSFER MOULDING:
Transfer moulding is an adaptation of compression moulding in that the moulding
material (usually a thermoset plastic) is preheated and loaded into a chamber known
as the pot. A plunger is then used to force the material from the pot through channels
known as a sprue and runner system into the mould cavities. The moulds remain
closed until the material is cured. Transfer moulding is widely used to enclose or
encapsulate items such as coils, integrated circuits, plugs, connectors, and other
components.
REACTION INJECTION MOULDING (RIM):
The process for fast and automated pproduction of large, thin and complex-shaped
parts in large numbers, from polyurethane, epoxy and other liquid chemical systems.
RIM differs from standard injection moulding process by fact that polymerisation
takes place within mould instead of cooling to form a solid part. Process where
mixture of two or more liquid components in the proper chemical ratio accomplished
in a mixture is delivered into a mould at low pressure where it reacts chemically
(cures) and results in a solid plastic part being formed. Typically polyurethanes where
the two liquids are isocyanate and polyol or dicyclopentadienes are used. Many RIM
systems incorporate filler materials (glass fiber, woven mats, continuous strand mats
or chopped fibers) for the purpose of enhancing the mechanical properties of the
moulded part or to reduce coefficient of expansion and also the cost of the plastics
system. Strong, flexible, lightweight parts are produced however the process cycles
are slow and utilises expensive raw materials. Moulds used are Machined steel or
cast aluminum.RIM products find wide applications in are the automotive
(automotive bumpers, dashboards and hoods) and construction industries.
PULTRUSION & FILAMENT WINDING: Refer EXTRUSION PROCESS
DIP MOULDING:
Process involves dipping a preheated mandrel into Plastisol (liquid paste based on
PVC and plasticizer) followed by a high temperature cure. The cured plastisol is then
removed from the mandrel resulting in a finished part. Application: Plastic purses,
hand tool grips, shifter boots for trucks & automobiles, bellows.
HAND LAY-UP / SPRAY LAY UP:
Usually involves impregnation of glass fibre mat with a liquid polyester mix. Hand
Lay-up is a method of producing composite structures by hand applying composite
materials in successive layers on a tool or mould that defines the part geometry.
Spray lay up is essentially a variant on this process that involves spraying the
material into the mould. A 'Gel Coat' can be incorporated provides a good surface on
the mould side.
FRP composites comprise two major constituents: the thermosetting resin matrix
and the fibre reinforcement. Unlike blends, in composites the constituents (fibres and
matrix) grossly retain their identities and simultaneously produce properties that can
never be achieved with either of the constituents acting alone. The fibres are usually
of high strength and rigidity and predominantly responsible for the load-bearing
capacity of composites. The role of matrix resin is to keep the fibres in a desired
location and orientation. Because fibres are mostly brittle, the resin is the source of
toughness for a composite. Commonly fibres are glass, carbon and Kevlar fibres. On
the basis of length, fibres can be short fibres and long continuous fibres.

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