Molds & Tooling
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PP Nozzle Drooling
Problem Phenomenon
Nozzle drips and hangs material during mold opening or plasticizing wait; cold material or stringing appears at the gate in the next shot.
Cause Analysis
PP melt has low viscosity; when nozzle temperature is high, back pressure excessive, or suck-back not set, melt flows out by itself after plasticizing; worn and enlarged nozzle orifice also aggravates drooling.
Solution
①Appropriately lower nozzle temperature; ②set a reasonable suck-back action to release pressure; ③replace worn or oversized-orifice nozzles; ④shorten wait time after plasticizing; ⑤if necessary, use a valve gate nozzle.
Key Takeaway
PP's low viscosity makes drooling easy—'lower nozzle temperature + add suck-back' is the first-choice combination; if ineffective, replace the nozzle or use a valve gate; cold slug marks from drooling spread to the next shot—stop it at the source.
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