The plunger injection molding machine pushes forward the fused plastics in the charging barrelthrough the to-and-fro movement of plunger therein, and the spreader further injects them into the mold cavity through the nozzle. The plastication of plastics in the charging barrel mainly depends on the heat provided by the outer heater of charging barrel. The poor thermal conductivity of plastics results in the unbalanced plastication to the inner and outer layer of materials in the charging barrel and therefore, the plunger injection molding machine is not suitable for the molding of plastic parts with low fluidity, strong heat sensitivity and overlarge amount of injection.
in London in 1961, plunger-type injection molding machines for thermosetting polyester molding compounds are today gaining growing acceptance in a field long dominated by compression and transfer types of equipment. The scope of this paper will be to present the latest developments occurring in plunger-type injection.
Reciprocating screw and plunger-injection molding machines, widely used in the polymer processing industry, are also used with some modification for ceramic suspensions. Reciprocating screw machines provide better metering and injection pressure control, lower cycle time, flexibility in part size, and superior homogeneity and reproducibility of the molded component. However, plunger-type machines are, in general, cheaper and have a longer machine life due to less wear.