N

Naturally balanced runner system: each succession of the runner is identical to the runners in the same succession in all other flows in the mold.

Nest Plate: A retainer plate in the mold with a depressed area for cavity blocks.
Non-Fill (also known as Short Shot): Failure to completely fill the mold or cavities of the mold. Edges may appear melted.

Non-Return Valve: Screw tip that allows for material to flow in one direction and closes to prevent back flow and inject material into the mold (check valve).

Notch Sensitivity: The extent to which the sensitivity of a material to fracture is increased by the presence of a surface notch or sudden change in section.

Nozzle: hollow metal hose screwed into the extrusion end of the heating cylinder of an injection machine designed to form a seal under pressure between the cylinder and the mold.

Nucleating Agent: Additive used in a polymer to increase crystallization rate by providing additional sites for crystal growth (i.e. Talc). This results in faster cycle time.