Plastic Injection Molding Process
Plastic injection molding is a manufacturing process that makes possible the production of highly finished and detailed plastic articles at very high repeatable production rates under high tolerances. The basic injection molding machine uses a hopper to feed the granular plastic particles into a heated barrel or unit that makes the plastics in a molten state. The heated barrel has a reciprocating screw-like plunger that in turn pushes the molten plastic under hydraulic or electric/mechanical force into the cavity(s) of a closed together mold that forms the designed part.

Rubber Injection Molding:

Injection molding is accomplished in a molding press specifically designed for that purpose. The mold is closed and locked into place by the operation of the press itself. Uncured rubber is pre-heated in an injection chamber prior to being injected into the mold itself, which “plasticizes” it allowing it to flow more readily through the injection system and into the cavities. This, along with the clamping and injection force provided by the press, allows curing temperatures to be elevated, shortening the curing cycle.

Advantages of Injection molding
Shorter production cycle than the other two methods due to higher clamping/injection pressure and curing temperature
Higher production rate per hour than other methods results in lower unit cost
High clamping pressure on mold results in parts having very little or no flash compared to other methods
Parts may not need any additional finishing processes

Disadvantages of Injection molding
Requires large production runs to be efficient.
Tooling cost considerably higher than other methods
Not all compounds, or durometers, are suitable for this process