Mold-Masters Hot Runner - Page 313

L/D Ratio: A term used to help dene an injection screw. This is the screw
length-to-diameter ratio.
Manifolds: distribute melt from the inlet component to one or more
submanifolds within a Hot Runner.
Melt Flow Rate: A measure of the molten viscosity of a polymer determined
by the weight of polymer extruded through an orice under specied
conditions of pressure and temperature. Particular conditions are dependent
upon the type of polymer being tested. MFR usually is reported in grams
per 10 minutes. Melt ow rate denes the ow of a polypropylene resin. An
extrusion weight of 2160 grams at 446°F (230°C) is used.
Melt Flow Index: Term that denes the melt ow rate of a polyethylene resin.
An extrusion weight of 2160 grams at 310°F (190°C) is used.
Mold: A series of machined steel plates containing cavities into which plastic
resin is injected to form a part.
Mold Frame: A series of steel plates which contain mold components,
including cavities, cores, runner system, cooling system, ejection system, etc.
Mold-Temperature-Control Unit: Auxiliary equipment used to control Hot
Runner temperature. Some units can both heat and cool the mold. Others,
called chillers, only cool the mold.
Moving Platen: The platen of an injection molding machine that is moved by
a hydraulic ram or mechanical toggle.
Multi-Cavity Mold: A mold having two or more impressions for forming
nished items in one machine cycle.
Multi-Material Molding: The injection of two-or-more materials, in sequence,
into a single mold during a single molding cycle. The injection molding
machine is equipped with two-or-more plasticators. (See also co-injection)
Nest Plate: A retainer plate in the mold with a depressed area for cavity
blocks.
Non-Fill: See short shot.
Non-Return Valve: Screw tip that allows for material to ow in one direction
and then closes to prevent backow during injection.
Machine Nozzle: The hollow-cored, metal nose screwed into the injection
end of a plasticator. The nozzle matches the depression in the mold. This
nozzle allows transfer of the melt from the plasticator to the runner system
and cavities.
Packing: The lling of the mold cavity or cavities as full as possible without
causing undue stress on the molds or causing ash to appear on the nished
parts. Over- or under-packing results in less than optimum ll.
PET: Polyethylene Terephthalate, a type of polyester and a leading recyclable
plastic material.
Pinpoint Gate: A restricted gate of 0.030 in. or less in diameter, this gate is
common on Hot Runner molds.
21-3GLOSSARY OF TERMS
Hot Runner User Manual
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