Injection molding: Injection molding is the primary process for manufacturing
plastic parts.
Plastic is known to be a very versatile and economical material
that is used in many applications. Although the tooling is expensive, the cost
per part is very low. Injection molding involves taking plastic of your choice
in the form of pellets or granules and heating this material until a melt is obtained.
Then the melt is forced into a split-die chamber/mold where it is allowed to
“cool” into the desired shape. The mold is then opened and the part is ejected,
at which time the cycle is repeated again.
Plastic Injection Molding Materials! Thermoplastics and Thermosets are used
in plastic injection molding.
Thermoplastics! Thermoplastics don't have strong
bonds with each other. therefore, they tend to be soft and ductile. When heated
above glass transition temperature, the bonds weaken and a reduction in strength
results. That's why they can be easily molded under shaping forces but when cooled,
the plastic returns to its original strength and hardness making the process reversible.
Thermosets! Thermosets have stong covalent bonds with each other. Thant's why
they are rigid and stiffer but tend to be more brittle. They also have a low electrical
and thermal conductivity making them excellent insulators. Unlike thermoplastics,
their properties are not very much dependent on the themperature or strain rate.
But if the temperature is high enough, they burn up and disintegrate.
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