This causes excessive heat loss that will result in a cold slug
, drooling, or stringing, all of which cost molders thousands each day.
It also offers options with which users can specify runners, sprues, and Cold slug
This process results in a lower cavity and gate area temperature, lower injection pressures at injection start and no pushing into the product a cold slug
as is normally the case with single heater hot runner systems.
Or, in one example, "a PVC pipe was found to have a crack that was caused by a cold slug
from the molding process.
Fortunately, most moldmakers do put a cold slug
well in the mold since, as mentioned previously, it's useful for pulling the sprue out of the cavity when the mold opens.
This cold slug
remains in the gate during the mold-open step, part ejection, and mold-close motion.
Note that this cold slug
will not always be caught in the cold-slug well.
A dimple can be used to aid flow at the gate because it permits a well for the frozen cold slug
to be blown into.
However, the more expensive valve-gate nozzle better separates the hot tool from the cold runner, allows for sequenced or profiled filling to each cavity, and leaves little to no gate vestige or chance for a cold slug
in the part," says Kingson sales engineering manager T.
Another source of temperature-related flow imbalances is the formation of small frozen plugs in the gate at the end of each hot tip, much like a cold slug
that forms on each shot at the tip of the machine nozzle.
Also, what about the cold slug
that sometimes comes out with the sprue, and sometimes stays in the nozzle tip?
The nozzle can handle engineering resins due to the design of the tips, which extend to the part surface and produce no cold slug