Platens: The mounting plates of a press on which the mold halves are
attached.
Preform: A plastic test tube shaped part produced by injection molding
systems in the rst step of a two-stage injection molding and blow molding
process used to produce PET bottles or containers. The perform is
subsequently re-heated and stretch blown through a blow molding process
into the nal container shape.
Pressure Disk: Manifold component designed to be compressed by thermal
expansive forces to form part of the plastic sealing mechanism. Also helps to
reduce thermal transfer to a minimum.
Process: The injection molding environment consisting of input variables
such as temperature, pressure, injection rates and time that are controlled
to ll the mold while optimizing the trade-os between cosmetics and
dimensional accuracy.
Ram: The forward motion of the screw in the barrel that forces the melt into
the mold cavity.
Recovery Time: The length of time for the screw to rotate and create a shot.
Retainer Plate: The plate on which demountable pieces, such as mold
cavities, ejector pins, guide pins and bushings are mounted during molding.
Ring Gate: Used on some cylindrical shapes. This gate encircles the core to
permit the melt to rst move around the core before lling the cavity.
Runner: The channel that connects the sprue with the gate for transferring
the melt to the cavities.
Runnerless Molding: See Hot Runner mold.
Scrap: Parts that do not meet the quality standards.
Screw Travel: The distance the screw travels forward when lling the mold
cavity.
Shear: The force between layers of resin as they slide against each other
or the surface of the mold. The resulting friction causes some heating of the
resin.
Short Shot: Failure to completely ll the part or cavities of the mold. Edges
may appear melted.
Shot: The complete amount of melt injected during a molding cycle, including
that which lls the runner system.
Shot Capacity: Generally based on polystyrene, this is the maximum weight
of plastic that can be displaced or injected by a single injection stroke.
Generally expressed as ounces of polystyrene.
Single-Cavity Mold: A mold having only one cavity and producing only one
nished part per cycle.
Sprue Bushing: A hardened-steel insert in the mold that accepts the Screw
nozzle and provides an opening for transferring the melt.
Sprue Gate: A passageway through which melt ows from the nozzle to the
mold cavity.
Sprue: The feed opening provided in injection molding between the nozzle
21-4
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GLOSSARY OF TERMS
Hot Runner User Manual
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