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There are two types of hot
runner systems:
Insulated runners
Insulated runner molds have oversized passages formed
in the mold plate. The passages are of sufficient size that, under conditions
of operation, the insulated effect of the plastic (frozen on the runner
wall) combined with the heat applied with each shot maintains an open, molten
flow path.
Heated runners
For heated runner systems, there
are two designs: internally heated and externally heated. The first is characterized
by internally heated, annulus flow passages, with the heat being furnished
by a probe and torpedo located in the passages. This system takes advantage
of the insulating effect of the plastic melt to reduce heat transfer (loss)
to the rest of the mold. The second consists of a cartridge-heated manifold
with interior flow passages. The manifold is designed with various insulating
features to separate it from the rest of the mold, thus reducing heat transfer
(loss). |
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