Processing, thermoplastics reciprocating machine

Fig. 11.30 Effect of preheating 50% by weight E-glass fiber-filled polyamide pulltruded pellets on fiber lengths at the screw tip of a 300-ton 23.86-oz reciprocating injection molding machine. [Reprinted by permission from C. G. Gogos, C. K. Yoon, and J. Brizzolara, Injection Molding Process Development for Long Fiber Reinforced Thermoplastics, SPE ANTEC Tech. Papers, 40, 384 (1994).]...

Injection molding is a cyclic discontinuous process used to form three-dimensional plastic parts (25. 26). Both thermoplastics and thermosets are injection molded. The process is shown schematically in Figure 11 for a reciprocating screw injection molder. This type of a machine has a screw rotating in a barrel similar to an extruder. However, here the melt flow is discontinuous and controlled via a check valve at the tip of the screw. Material is melted in the extruder, and the melt is accumulated in front of the screw tip until sufficient melt is at hand to fill the mold cavity (cavities). 

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